NC0000272_Color Related Reports 2006_20061103

BLUE RIDGE
PAPER PRODUCTS INC.
Blue Ridge Paper Products .Inc.
Canton Mill
NPDES No. NC 0000272
Color Related Reports — Nov 2006
Public Version for Interested Party Review
May 2006 Color Compliance Report
July 2006 GL&V Bleach Environmental Process and
Evaluation Report (Leibergott II Report) —
Nov 2006 public version with commercially sensitive process data
redacted
August 2006 NCASI Technical Bulletin No. 919 — Review of
Color Control Technologies and Their Applicability to
Modern Kraft Pulp Mill Wastewater
These reports were submitted to the North Carolina Division of Water Quality
as part of the May 2006 application to renew the NPDES permit for the Blue
Ridge Paper Products Canton Mill. These copies were requested by the
Division to satisfy third-party requests related to review of the permit
application. The enclosed reports are identical to those submitted to the
Division. Some process-related data in the Leibergott II Report is
commercially sensitive and has been redacted. The redacted information does
not change the analysis, recommendations or conclusions in the report
regarding wastewater effluent color control.

Paul .To [e-mail]
Dickens/Canton/BlueRidge
[e-mail], [e-mail],
11/02/2006 11:39 AM cc Bob Williams/Canton/BlueRidge@BlueRidgePaper, Derric
Brown/Canton/BlueRidge@BlueRidgePaper, Glenn
bcc
Subject Public Report Versions in Mail
11/2
Sergei -
Thanks for the update on the 10/26 conference call with EPA and for the update on your discussions with
Don Anderson concerning the TRW.
As promised by Bob Williams,the public version of the Leibergott II Report is in the overnight mail to you.
This is the copy for Hope Taylor and other interested third parties. I am also sending a CD with a
read-only, print protected PDF version of the pubic Leibergott II Report.
I am sending one copy of the public report notebook to Roger Edwards at the ARO for their use.
Paul Dickens
Manager, Environmental Affairs
Blue Ridge Paper Products, Inc.
[e-mail]
828-646-6141 FAX [phone]
,
Address for Sergei for overnight mail -
Dr. Sergei Chemikov
Environmental Engineer
NPDES Unit
North Carolina Department of Environment
and Natural Resources
Division of Water Quailty
1617 Mail Service Center
Raleigh, NC 27699-1617
919-733-5083, ext594
Address for ARO -regular mail
Roger Edwards
Regional Supervisor
Division of Water Quality
North Carolina Department of Environment
and Natural Resources
Asheville Regional Office
2090 US Highway 70
Swannanoa, NC 28778
828-2964500

Z PROU D TO B E A
wMAKER
PER
J
Q
we are highlighting
u ONCE AGAIN THIS YEAR IN PAPER3600
w examples of personal and corporate excellence. Excellence is
more thandoingthingsbythebookoriusttosurvive.It'sabout
seeing the big picture and making the tough choices in order to
move forward.It's a tradition established over generations that
continues today and into the future.
P
Restoring the Pigeon River;
�ey
Evergreen Packaging
Y 1
AN AGGRESSIVE ENVIRONMENTAL PROGRAM CLEANS UP a troubled waterway
GLENN OSTLE
Dwrk Brawn ntxiar 9uteYtabBlY
vergreen Packaging in Canton, N.C., today a lot of hardworking people available to work at the mill
rkable environmental success reinforced the idea that the company came for the trees
ranks as a remapeop
story.But it has been a long trip getting there. but stayed a°rPfoducts`eand i 92007 it was bacquired lby
In the 100 years since the mill opened, g P Group, art of New Zealand-based
effluent from the mill flowed into the Pigeon Evergreen Packaging p,P
d.
River,negatively affecting water quality.But in RankCanton s atfully-integrated Kraft pulp and paper mill
Ethe early 1990s,the mill began an aggressive program to
upgrade its environmental performance. employing about ns people and located near the Great
ut 5600
Derric Brown. Director of Sustainability, has been at Smokey Mountains Nerc percent] and HW 160 peational. Park. it uses rt ntl chips
the mill since the 1980s working in environment, health se°t to shif ed in SW from within 300 miles of the mill, to
and safety. His father worked there before him. "Today p Y PP
in Haywood County [North produce about 1420 short tpd of pulp.Tall oil and turpen-
Carolina], there is a huge tine produced are sold as feed stock chemicals.
The pulpbecomesfurnishforthemill'sfourpaperand
commitment to improving
protecting the Pigeon board machines that have a total production capacity of
and up to 1800 short tons per day.Three of the machines—
River," says.
Nos. 11. 12 and 20—produce rolls of uncoated freesheet
SMOKEY MOUNTAIN [UFSI,which are shipped toa variety of customers around
MILL the world for conversion into envelopes,printing papers,
The Canton mill began oper- and colored and specialty papers. It is estimated that
hampion Evergreen fills about 4 percent of the North American
ations in 1906 as C
Fiber Co. The 175-acre site white paper market.
was originally selected for No. 19 machine is a single-ply board machine that
its proximity to red spruce, produces FDA food-grade paperboard which is sent to
fir and chestnut; a good Evergreen's Waynesville (N.C.) plant,about eight miles
Evergreen's state-of-the-art water supply;and a railroad. away,where the rolls are extrusion coated with polyeth-
wastewaler treatment facility has
slgm scantly imp,eved waterquaiity. The fact that there were also ylene and other plastics.The Canton mill and Waynesvi e
a poper360a November/December 2010

plant, plus other converting plants, originally formed in North Carolina's Blue Ridge Parkway and flows north
Champion's DairyPak Division. about 20 miles to the Walters Dam,built for power genera-
At Waynesville and other Evergreen converting facili- tion.The single Pigeon River watershed is unusual in that it
ties,the board is printed,scored and shipped flat to cus- is entirely contained within Haywood County.After the dam,
tomers who use it to produce gable top cartons for liquids the river drops about 1000' before crossing into Tennessee
such asjuice and milk,cup stock and ovenable trays.Most ThePiiteventallyconnectswithteFregindnch BroadRigin-
paperboardproducedatCantonisconsumedinternallyby Ting Pigeon
state line.
River supports a robusustry
the company's converting plants.
Says Dane Griswold, General Manager, Canton- According to Nick McCracken, Evergreen Packaging s
Waynesville operations,`Liquid packaging board isn't as Water Compliance Coordinator,"The river started to come
cyclical as other products,and our smatter UFS machines
eat iinth the ear0sandly 70sbutwith the lytookomitt's odernizatioiUhas
roj-
allow us to make a lot of specialty products'
spent more than US$300 million on pollution prevention.
MODERNIZING THE MILL As a result of the mill modernizing the pulping,bleaching
In 1993 the mill completed the Canton Modernization and spill recovery and significantly improving the quality of the
Project which included the addition of oxygen delignifica- wastewater discharge,water quality of the Pigeon River and
tion on both fiber lines Ipine and hardwoodl, and instal- the health of fish populations improved greatly.Species that
lation of 100 percent chlorine dioxide substitution. This had not been seen in over 60 years began returning including
allowed the mill to achieve 100 percent ECF bleaching small mouth bass,walleye and trout.
using chlorine dioxide,which is manufactured on-site.
Enhancements to the black liquor evaporators resulted
in improvements in color and environmental performance
and reduced boil out time.The mill also added an exten-
sive sump recovery system with 22 sumps.Through the
environmental improvements,the mill was able to reduce
colorfrom 350.000 lbsto 39.0001bs,measured on a mass
basis,between 1990 and 2010.
"Our whole strategy has been focused on pollution
prevention throughout the mill,to reduce color,flow,BOD,
TSS,and AOX,"says Brown."Our BOD load is a smallfrac-
tion of other mills—typically less than 10 mg/L our limit
is just over 3,000 lbs/mo.We also reduced water use by
about 35 percent and color by over 75 percent.W e've done
all this through an overall program of pollution prevention
which provided more benefits than just dealing with one The Pigeon River mns th ough the center of Evergreen Packeging.Canton.N.C.
piece at a time"
In 1995 the mill added Bleach Filtrate Recycling IBFRI
on the pine line which recycles about 80 percent of the
filtrate back into the liquor recovery process.It consists
of two parts, one to remove minerals such as calcium,
T .:.
magnesium and manganese through ion exchange,and
the second to remove chloride which can build up in black
Liquor and cause corrosion and blockages.The improved
recycling rate keeps color in the process instead of losing
it to the wastewater plant. "Some mills run part of this
process,but we are the only Kraft mill in the world that
runs the whole process,'says Brown.
A RIVER RUNS THROUGH IT he cooling mrec the comemm�eM lre mitts water system,helps re aana
The Pigeon River that bisects the mill,is small and fluctu- 1e13e Intel.
ates greatly with the seasons. It begins with headwaters
poper360° November/December 2010
9

PROUD TO BE A PAPERMAKER
z "It has become a model template," according to
O
— .--v F4 •� ,-- McCracken who says that other groups wanting to start
kin for advice.
programs are now asking reintroduction progra
w Yhl - The project also received the 2006 award for the Most
Environmentally Beneficial Practice at the EPA sponsored
a National Environmental Partnership Summit.
u As further proof of the improvements to the water
w quality,last year more than 150.000 people paid to raft on
a
vt - the Pigeon River,which is good news for the local county
Keith Treadway and jimmy Inman monitor the Foxboro automation as it charges$2a rafter.Since 1995 more than 1.5 million
syatema far the sw fip Mn.. people have paid to raft on the river.
TREATING THE WATER
"We've come a long way over the past 20 years,"says Brown.
"We now have a state-of-the-art wastewater treatment facil-
ity and our performance is among the best in the world."A
1995 NCASI study revealed that the Canton mill was signifi-
cantly better than the overall average of 23 surveyed mills in
the areas of AOX,TSS,BOD,COD,color and flow.
According to Brown, the Canton mill uses activated
sludge wastewater treatment and foul condensate steam
stripping for better quality and efficiency.The plant even
'• ' '" +- - _ processes all the wastewater for the town of Canton.
PM-20 is ona of tnrae UFs paper maen nee atI teCerdm r`& While many mills use unlined lagoons for wastewater
But there was still a question about the fish that were treatment.Canton uses a fully contained activated sludge
missing. Biological studies found that while the bigger system."This is a high efficiency treatment system,"says
game fish had returned,there were still a lot of smaller Brown."A lot of other places wish they had one"
non-game fish that didn't have a way to come back on
their own."A river that can support both has highbiologi- OTHER GREEN EFFORTS
cal diversity and integrity," says McCracken.So the mill, In the last few years the Canton mill has attained a num-
tate,federal and private groups bar of environmental certifications including SFI and FSC
along with a number of s
introduce Chain of Custody.Since 2000,the mill has spent more than
began the Pigeon River Restoration Project to reUS$19ittionon air emissions controls.
and re-colonize native non-game species back into the energy it uses comes from renewable sources.today
Pigeon River.
Coordinated bythe University of Tennessee,Knoxville, Derric Brown is also heavily involved in a project with
ve
this multi-agency effort began by reintroducing missing the CartonCounciltorecycleused infrastrartons, a ucture
species in Tennessee in 2001, based on an earlier suc- processthat requiresa sustainable infrastructure starting
cess reintroducing mollusksthere.In 2004 reintroduction with recyclers and working with them to accept cartons
efforts began in North Carolina.The fish to be reintro- and sort them into a separate single grade."There's a lot
in the sorted carton grade,and demand is
duced were found in nearby tributaries and waters that of value
Brown"We are working with mills to akegthose
had a similar habitat structure and tolerances. g, says .
"There's a lot that goes into it,"says McCracken."For cartons and recycle them into tissue or recycled pulp.It is
instance,fish were injected with small spots of dye to iden- essentially a new source of very good fiber.
tify those from different years and confirm that they were The Canton mill also boasts asolarfarm that generates
reproducing.A lot of the techniques had to be developed 555kW of electricity—enough to power about 50 homes for
as we went along, and now the University of Tennessee a year.
r.O 's closed landfil and operated byiSFLS Energy largest d built
on
farm
folks have become national experts"
Today reintroduced fish species that were believed in western N.C. "We don't own it but it makes us feel that
to previously live in the Pigeon River, are surviving and we are helping a local green company and contributing to a
reproducing.To date,there have been nine species and future renewable energy source,"says Brown.
26,000 individuals reintroduced including gilt and banded
site is darters, bigeye chub, mirror, saffron, silver, telescope. Flenn 0
aper360°and can obe conrial ttacted/at gos[le®tappi!ohgr of
Tennessee and highland shiners.
20 poper360° November/December 2010

2006 UPDATE
BLEACH ENVIRONMENTAL PROCESS
EVALUATION AND REPORT
BLUE RIDGE PAPER PRODUCTS, INC.
FOR: CANTON MILL
JULY 7, 2006
GL&V Proposal Number 604-5857 RO
Blue Ridge Paper Products Purchase Order Number 319926
Public Version - November 2006
Commercially sensitive process data redacted_
Pubic Version - Nov 2006

IGnt
ACKNOWLEDGEMENTS
The authors of this report gratefully acknowledge several Blue Ridge personnel
for the dedication of their time during the site visit, and sharing of their knowledge
and expertise of the Blue Ridge Paper Products Inc. mill operations during the
course of this study.
Michael P. Ferguson
Derric Brown
Glenn Rogers
Chad Dowdle
RESPECTFULLY SUBMITTED
Dr. Norman Liebergott, Ph.D. Lewis D. Shackford, P.E., and
Liebergott & Associates Consulting Inc. GL&V USA, Inc.
5825 Shalom Avenue, Suite 802 141 Burke Street
Cote St. Luc,Quebec, Nashua, NH 03060 USA
Canada H4W 3A5 TEL. [phone]
TEL. [phone] FAX [phone]
FAX [phone] E-mail: lewis.shackford(cDglv.com
E-mail: IiebergottC)svmpatico.ca
Omit Sezgi, Ph.D.
GL&V USA, Inc.
TEL. [phone]
E-mail: umit.sezgi(aglv.com
Pubic Version - Nov 2006 CONFIDENTIAL

VGA/
Table of Contents
Tableof Contents.......................................................................................................... 2
ExecutiveSummary...................................................................................................... 3
Process Optimization..............................................................................................................3
Review of Color Reduction Initiatives Implemented since 2001 ..............................................0
In-Process Changes...............................................................................................................0
ExternalTreatment................................................................................................................. 1
Summary of Options For Environmental Improvement HARDWOOD LINE ...........................5
Summary Of Options For Environmental Improvement SOFTWOOD LINE............................6
Background and Introduction...................................................................................... 7
Environmental Performance Benchmarking............................................................. 10
Site Audit and Performance Review.......................................................................... 13
Introduction: ......................................................................................................................... 13
Review of Color Reduction Initiatives since 2001: ................................................................ 14
Review of Process Operating Data:......................................................................................34
No. 1 Hardwood Fiberline.................................................................................................34
No. 2 Softwood Fiberline:.................................................................................................39
No. 1 and No. 2 Fiberline Audit Observations and Recommendations:.................................43
Summary of Recommendations: ..........................................................................................52
Overview of Technology Options .............................................................................. 54
Introduction ..........................................................................................................................54
In-Process Options...............................................................................................................54
External Treatment Options..................................................................................................81
Jacobs Study and NCASI Study Commentary..................................................................81
Emerging External Treatments.........................................................................................97
Methods for Recycling Effluent........................................................................................... 100
Options for Improved Environmental Performance............................................... 109
Basisfor Study................................................................................................................... 109
Conversion to Extended Delignification .............................................................................. 115
Conversion to Two Stage Oxygen Delignification............................................................... 117
Conversion of Extraction Stages to Eop.............................................................................. 120
Conversion of Extraction Stages to PHT.............................................................................. 121
Appendices................................................................................................................ 125
APPENDIX 1. Confidentiality Agreement............................................................................ 126
APPENDIX 2. Study Participant Resumes.......................................................................... 132
APPENDIX 3. Technical Overview Of Blue Ridge Paper Products Inc ............................... 138
APPENDIX 4. Washing Definitions..................................................................................... 141
Pubic Version - Nov 2006 CONFIDENTIAL

VGIN
Executive Summary
In 2001 Liebergott Associates, Inc. and GL&V USA conducted an evaluation of
Blue Ridge Paper Product's Canton Mill. The evaluation was conducted for a
consortium of environmental groups led by Clean Water for North Carolina with
support from Blue Ridge Paper Products. The focus of the study was to evaluate
the operation of the fiberlines and prepare a report identifying options for effluent
color reduction.
This 2006 update report was requested by Blue Ridge Paper Products in order to
independently:
• Assess the progress made on the 2001 recommendations
• Review the results of the changes implemented and improvement
achieved
• Audit current process conditions and provide feedback on opportunities for
improvement
• Recommend potential technology options that would further improve
environmental performance.
This report concludes that Blue Ridge Paper Products has done a very good job
implementing the 2001 recommendations and has made additional
environmental improvement as a result. An updated comparison of the Canton
Mill to other Kraft mills in the USA, Canada, and Finland indicated that there still
are no COD, BOD, or color values lower than those achieved by the Canton mill.
Given the current state of adaptable technology and the mill's already high level
of environmental performance, future improvements are expected only to be
marginally incremental. The potential for future improvements are described in
the body of this report.
Process Optimization
A review of the operation of the hardwood and pine fiberlines was conducted,
and some opportunities were identified to potentially reduce color from the
fiberlines. The current operation of the fiberlines has been compared to the
performance reported in the 2001 Bleach Process and Environmental Report
(BEPER). Overall, the performance of both fiberlines is good, and the control
has been improved quite substantially since the last audit in 2001.
Specific recommendations from this site study have been made to improve the
performance of the current operation are shown in Table 1.
Pubic Version - Nov 2006 CONFIDENTIAL

TABLE 1 — PROCESS IMPROVII. ;NT RECOMMENDATIONS
Hardwood Pine
Cr
n Washing Washing
m Improve performance of vacuum washers through: Improve performance of decker showers through:
yr Reduction in feed consistency Reduction in feed consistency
Raise the vat level set point Raise the vat level set point
Clean and correctly align all showers Continue replacement of shower bars with the
pContinue replacement of shower bars correct alignment
c Calculate drop leg velocities of each washer as a performance Calculate drop leg velocities as a performance metric
o metric
0
rn
Improve operation of the deckers to improve the
discharge consistency(if additional changes are
needed after completion of#1 above)
Evaluate the elimination of wash water bypass on the
first decker shower(liquor being added directly to the vat
will reduce dilution factor applied to the washer)
Evaluate the elimination of bypass of Eo filtrate to
decker filtrate tank- move the application to the decker
showers or another washer
Bleaching Bleaching
Evaluate the use of oxygen and peroxide fortification of the extraction Evaluate the use of peroxide fortification of the extraction
stage at reduced D1 kappa factors stage to reduce Eo color
Decrease target kappa factor to= Decrease target kappa factor to NEW

* GB/
It is difficult to project the potential chlorine dioxide use or reduction in color in the
bleach plant effluent for improvements to the washing on the deckers. Further, it
was planned to replace the showers on the pine decker shortly after this site
study, so the benefits on the pine side may have already been realized.
However, we do expect a slight improvement on the hardwood side with this
optimization.
Review of Color Reduction Initiatives Implemented since 2001
Since the 2001 BEPER ('Bleach Environmental Process Evaluation and Report)
was issued, almost $6,000,000 has been invested by Blue Ridge in upgrades to
the mill, as well as studies of proposed potential technologies to be implemented.
These changes have been reviewed, and comments offered relative to their
actual reported results and/or the validity of the test data in key studies. These
initiatives can be classified as "In-Process" changes and External Treatment
changes ("end-of-pipe"). There remain several potential changes to be
considered based on learnings from the earlier work, and new developments
since the issuance of the 2001 BEPER. An Overview of Technology Options for
consideration is included, and is also broken into the two main strategies to
achieve color reduction: "In-Process" changes and External Treatment ("end-of-
pipe").
In-Process Changes
Four key technologies, which modify the cooking, oxygen delignification, or
bleaching operation for the hardwood and/or pine fiberlines, have been evaluated
in further detail. Estimated color reductions of 740-3534#/day for hardwood and
1224-3100#/day for pine may be achieved using modifications to the fiberline and
maintaining ECF pulp production.
The impact of these options on the mill operation are summarized in tabular form
on the next two pages, and detailed in the Options for Improved Environmental
Performance. There is the potential for greater color reduction by combining two
or more of these technologies on hardwood or pine pulp; however, the benefits in
color reduction are not additive, so various combinations of technologies need to
be separately estimated. All environmental impact projections are based on
outflow from the bleach plant to the effluent treatment plant. Effluent color from
the treatment plant is difficult to predict and decreases in bleach plant effluent
color do not necessarily translate into decreases in effluent color from the
treatment plant.
Any technology that is determined to be of interest for commercial
implementation at Canton should be confirmed by properly executed laboratory
studies and potentially followed by mill trials.
Pubic Version - Nov 2006

IGBI
External Treatment
A number of emerging technologies for bleach plant effluent treatment have been
described in the Overview of Technology Options. These options may be
considered for color reduction, but this strategy incurs significant capital
expenditure while increasing operating and maintenance costs. One or more of
these external treatments may be considered for treatment of individual sewer
streams, but this is beyond the scope of this study. The treatment of whole mill
effluent by any of these technologies does not appear financially viable.
Pubic Version - Nov 2006 CONFIDENTIAL

f0 GVV
< Summary of Options for Environmental Improvement HARDWOOD LINE
m
a) Extended E/EoP (PO)/P T
O Deli nification conversion Conversion
I
Color Current#/Day 8,220 8,220 8,220
z Potential Reduction % 20% 31% 43%
O Potential Reduction #/Day -1,644 -2,548 -3,534
N Impact
o Water Use, gal/ton N/C N/C N/C
rn Effluent Flow, gal/ton N/C N/C N/C
AOX kg/t -0.11 -0.3 -0.3
Toxicity N/C decrease decrease
Temperature N/C increase increase
Pulp Quality Significant N/C N/C
increase
Commercial Experience High Moderate I Moderate
Operating Cost Decreased Increase Increase
Capital Cost Very High Moderate/Low Moderate
Commercial Experience Capital Cost
Low 0-3 similar installations in operation Low <$1 million
Moderate 4-10 similar installations in operation Moderate $1-5 million
High >10 similar installations in operation High $5-10 million
Very High >$10 million
Capital costs are preliminary estimates, and do not
include lost production or impact of downtime
NOTES:
1. Technologies are not additive in impact; combinations of two or more technologies require further estimation.
2. All technologies require more detailed study for performance and installation feasibility.
3. Capital cost estimates are limited to only changes in the fiberline equipment; utilities and support services not included.
4. All environmental impact projections are based on outflow from the bleach plant to the effluent treatment plant and not the color
discharged to the river.

c
n
Summary of Options for Environmental Improvement SOFTWOOD LINE
m Extended Two Stage Eo/Eop (PO)/PHT
v) Deli nification Oxygen Conversion Conversion
Color Current#/Day 8,160 8,160 8,160 8,160
Potential Reduction % 15% 14% 25% 38%
Z Potential Reduction #/Day -1,224 -1,142 -2040 -3100
o Impact
N Water Use, gal/ton N/C N/C N/C N/C
o Effluent Flow, gal/ton N/C N/C N/C N/C
AOX kg/t -0.26 -0.1 -0.36 -0.36
Toxicity N/C N/C decrease decrease
Temperature N/C N/C decrease increased
Pulp Quality Significant Potential N/C N/C
Increase improvement
Commercial Experience High High Moderate Moderate
Operating Cost Decreased Decrease Increase Increase
Capital Cost Very High Moderate Moderate/Low Moderate
Commercial Experience Capital Cost
Low 0-3 similar installations in operation Low <$1 million
Moderate 4-10 similar installations in operation Moderate $1-5 million
High >10 similar installations in operation High $5-10 million
Very High >$10 million
Capital costs are preliminary estimates, and do not
include lost production or impact of downtime
NOTES:
1. Technologies are not additive in impact; combinations of two or more technologies require further estimation.
2. All technologies require more detailed study for performance and installation feasibility.
3. Capital cost estimates are limited to only changes in the fiberline equipment; utilities and support services not included.
4. All environmental impact projections are based on outflow from the bleach plant to the effluent treatment plant and not the color
discharged to the river.
CONFIDENTIAL

VGBI
Background and Introduction
The Canton mill is unique in the world, being the only mill to incorporate the
BFR° process in the fiberline. The BFR° process is installed on the softwood
line, and allows a major portion of the D, and Eo bleach plant effluent to be
recycled through the brown stock washing system and to the chemical recovery
process. This process has been extensively evaluated, and is operated at a
degree of filtrate closure where the penalty in bleach chemical use and pulp
quality parameters is minimized, while maximizing the environmental benefit.
To continuously improve effluent quality, Blue Ridge Paper Products Inc. has
undertaken a comprehensive program focused on reducing the level of color
discharge. As part of an ongoing color reduction initiative, Blue Ridge Paper
Products Inc. asked Liebergott and Associates, Inc., and GL&V USA, Inc. to
evaluate the current operation of the fiberlines, and prepare a report identifying
options for further effluent color reduction at the facility. A Site Review and Audit
was conducted at the mill from May 9-11, 2006.
It was agreed that the study would include four parts.
I. Scope of Work
A. Review of Changes Implemented
Review the results of changes implemented since the original
Bleach Environmental Process Evaluation and Report ("BEPER")
report was issued in June 2001. Identify whether best performance
is being achieved, and comment on any potential further
optimization.
B. Site Review and Audit
Conduct an on site review and evaluation of present process
conditions, and make recommendations for improvement, review the
current performance of the fiberline, and identify specific operating
parameters that may be changed to improve environmental
performance.
Pubic Version - Nov 2006

* GIN
This will specifically include:
Evaluation of the chemical usage and procedures used in
bleaching
Review chemical addition points and individual control
strategies
Review washer operation
Review oxygen delignification stages to optimize performance
Where changes may be suggested, and prediction of outcome is
desired, outline laboratory trials that may be performed to determine
best operating configuration to ensure that changes made will
produce better quality pulp and effluent.
C. Environmental Performance Review
Review the findings from the June 2001 BEPER report and how
Blue Ridge has responded to the suggestions. Comment on any
and all conclusions made by Blue Ridge in the viability of the
implementation of prior recommendations. The technologies will be
reviewed and the technologies framed in the context of their
"current state" and Blue Ridge's current color data.
D. Options for Improving Environmental Performance
Include suggestions for additional options that may be valuable to
improve environmental performance.
Prior to the study, Blue Ridge Paper Products Inc. provided to Liebergott and
Associates Inc. and GL&V USA, Inc. copies of all information requested in the
Study Proposal. This included flow schematics of fiberlines, historical
environmental data, operations logs from a stable operating period 2006, as well as
all specific data requested. As this data includes sensitive operations data, a
Confidentiality Agreement was executed among the parties prior to the start of work
at the mill. A copy of this Confidentiality Agreement is included in Appendix 1 of
this report; a fully executed original copy of the Agreement was distributed to each
of the three parties on May 9, 2006 at the Blue Ridge mill.
The data received in advance offered the opportunity for Liebergott and Associates
Inc. and GL&V USA, Inc. to identify areas of the fiberline that may have
opportunities for improvement in operating economy and/or environmental
performance.
Pubic Version - Nov 2006 CONFIDENTIAL

VGB/
On May 8, 2006, Dr. Norman Liebergott of Liebergott and Associates, and Lewis D.
Shackford and Omit Sezgi of GL&V USA, Inc. arrived at the mill in Canton, N.C.
During the period of May 9-11, 2006, Blue Ridge Paper Products, Inc. offered a
detailed review of color reduction initiatives studied or implemented since the issue
of the 2001 BEPER study, provided a detailed tour of the mill, and was responsive
to all requests for operating information as well as requested data and historical
reports for review. This provided a good understanding of the current operation of
the fiberlines for the parties.
Pubic Version - Nov 2006 CONFIDENTIAL

VGBI
Environmental Performance Benchmarking
A comparison of selected effluent parameters; AOX, TSS, BOD, COD, Color and
Effluent outflow between the Blue Ridge Paper Products Inc. mill and other mills
in the U.S.A., Canada and Finland was included in the 2001 BEPER study. The
USA data includes results from 30 facilities with similar paper products to those
produced at Blue Ridge Paper Products Inc. The Canadian data was taken from
a comprehensive report in the "1996 Environmental Conditions of the Pulp and
Paper Mill in Canada", which was prepared by HASimons, and published by
CPPA. The value and average from the forty-three mills were used in the
comparison. Also included were two published mill updates, including data
produced in the year 2000 for two Canadian mills, one of which had introduced
ozone into the chlorine dioxide delignification stage. Effluent data from 3 facilities
in Finland were also evaluated. The information is shown in following table. In
updating this table, we have added the Canton Mill 2005 average data, as well as
updated data on the Espanola and Boyle mills in Canada, and included the
results from a more recent environmental survey of all Canadian mills.
At Canton, the color and AOX have been reduced further from the 1999 data, by
9.4% and 17.7%, respectively. There were no COD, BOD, or Color values lower
than those produced by the Canton mill. There was one mill in the NCASI survey
that reported a lower TSS value than shown by Canton mill value. The average
AOX reported by the TCF mill in Finland are 0.07 lb/ton of pulp, lower than the
0.14 lb/ton listed for the Canton facility. Finnish TCF mills sometimes do produce
ECF grades of pulp and hence do produce AOX. The low AOX values shown
are averages taken combining both ECF and TCF regimes, which may bias the
data.
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GLN
Cr
3 A Comparison between Selected Mill Effluent Parameters (discharge from treatment plant) from the Blue
Ridge Paper Products Inc. Canton Mill and Other Facilities in the U.S.A., Canada and Finland (Integrated
Mills
Pulp
Production
Z
0 BHWK BSWK AOX TSS BOD COD Color Flow*
< Data From ADMT ADMT Lbs/ton Lbs/ton Lbs/ton Lbs/ton Lbs/ton Gal/ton
o Canton Mill 2005 average 797 586 0.14 2.61 1.16 25.1 28.30 18,547
C) Canton Mill 1999 764 551 0.17 2.57 0.9 16.63 31.22 18,631
rn
Canton Mill 1995 0.33 2.81 1.34 30.80 56.20 19,547
NCASI Study
Avg 2.16 6.68 4.13 76.88 200.55 20,637
Min 0.20 1.00 0.91 13.90 31.90 13,413
Max 16.78 23.00 16.06 224.00 581.00 42,000
Espanola Mill, 2000 450 550 0.36 3.0 4.4 20.8 108. 00 26,800
Boyle Alberta Mill, 2000(2) 1700 1480 0.40 4.8 0.41 15.0 51.11 22,890
CPPA Study
30HWASW, 38-43 mills
9 HW/SW - Avg 1.20 8.1 5.20 68.20 146.22 22,140
Min 0.32 4.3 0.41 15.90 24.20 19,800
Max 2.35 24.60 28.20 83.96 297.20 29,000
Report on Environmental (5) (5) 0.80 6.2 3.2 65.6 122.4 20,424
conditions P&P mills in
Canada 2001 (2003)4
TCF Finland (mills
produce TCF and ECF HW & HW& 0.10 N/A 1.6 30.02 40.3 9,000
pulps based on demand) SW SW
CONFIDENTIAL 71

v
m
� (1) 1995 NCASI Solid Waste Survey (23 mills) —overall average of 17 to 30 mills.
(2) 2000 (2) Canadian Mill data (Softwood pulp bleached on different days).
o (3) 1996 CPPA Environmental Study (48 mills).
< (4) 1999 Finnish mill data — (3 mills).
o (5) Based on a total production of 47,556 metric tons/day all mills (hardwood and softwood)
o Flow is Total Mill Effluent Flow.
rn
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Site Audit and Performance Review
Operation Review of the No. 1 and No. 2 Fiberlines at
Blue Ridge Paper Products Inc., Canton, North Carolina
Introduction:
Omit Sezgi and Lew Shackford of GL&V USA Inc. and Norm Liebergott of
Liebergott and Associates toured the pulping and bleaching operations of the
Blue Ridge Paper mill located in Canton, N.C. during the period of May 9-11,
2006.
The areas toured during the period May 9-11, 2006 were:
• The No. 1 hardwood fiberline brownstock washing, 02 delignification
and bleaching.
• The No. 2 softwood fiberline brownstock washing, 02 delignification
and bleaching.
• The central control room for both No.1 and No.2 fiberlines.
• The metals removal process (MRP) and the chloride removal process
(CRP).
In addition, numerous meetings were held with Blue Ridge Paper personnel, and
requested data was assembled.
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Review of Color Reduction Initiatives since 2001:
In 2001, the color in the bleach plant effluent streams was summarized and
reported in the BEPER study. Since that time, color in the bleach effluents have
been significantly reduced, as shown in the following table, which also includes
2005 data to show the progress in color reduction:
Pine Sewer 1999 1999 2005 2005
Stage Color, Wday Color, Wton Color, #/day Color, Wton
Di 6770 12.3 2790 4.7
Eop 2260 4.1 4450 7.6
DZ 1000 1.8 920 1.6
Total 10,030 #/day 18.2 #/t 8,160 #/day 13.9 Wton
Hardwood
Sewer 1999 1999 2005 2005
Stage Color, #/day Color, Wton Color, #/day Color, Wton
D, 7310 9.6 4570 5.7
EoP 5970 7.8 3650 4.6
Total 13,280 Wday 17.4 Wt 8,220 Wday 10.3 Wton
Combined Total 23,310#/day 16,380 #/day
Acid from Bleach Stages) 1999 2005
-Stage Color, #/day Color, #/da
Pine Di 6770 2790
D2 1000 920
HW D, 7310 4570
Total 15,080 Wday 8,280 #/da
Alkaline from Bleach Stages) 1999 2005
-Stage Color, #/day Color, Wda
Pine Eo 2260 4459
HW Eo 5970 3650
Total 8,230 #/day 8,100 #Ida
Combined Total 23,310 #/day 16,380 Wday
Reduction 30%
Blue Ridge Paper monitors all sewers daily, and is able to create performance
averages of color in each sewer. This was provided to us in the form of "Pie
Charts". We have reviewed he "Pie Charts" for each year since 2001. From this
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data, we have created the following data table to study the changes in each
sewer for the last 5 years. This is illustrated in the following table:
2001 2002 2003 2004 2005
PIE Chart data % of total % of total % of total % of total% of total
26 - Digesters, No. 1 FL 7% 9% 5% 8% 2%
3A - No.2FL BSW, 02 Delig 1% 4% 1% 9% 13%
PM's- 11 & 12 4% 4% 3% 4% 4%
56- Recovery, BLO,CRP 20% 24% 22% 16% 21%
#2 - Evaporators: 1% 1% 1% 1% 2%
Contaminated Condensate: 2% 2% 3% 4% 6%
Combined Condensate: 1% 1% 1% 1% 1%
Pine Eo 6% 7% 9% 8% 10%
Hardwood Eo 12% 10% 8% 5% 8%
Pine D, 5% 5% 4% 7% 6%
Pine D2 1% 1% 1% 1% 1%
Hardwood D, 12% 14% 12% 10% 10%
Unaccounted: 27% 18% 30% 26% 15%
From the earlier data, it is clear that a 30% reduction in bleach plant effluent color
has been achieved in the period 1999-2005. However, this reduction relates to
only a 9.4% reduction in effluent color from the treatment plant. This indicates
that it is extremely complex to predict the impact future color reduction initiatives
will have on whole mill effluent color. As can be seen from mill color data,
reductions in color streams entering the mill's treatment plant do not translate
into equivalent reductions in whole mill effluent color. With this in mind, it is
valuable to also consider the source of the color in the specific mill sewers to
identify areas for further improvement.
An analysis of the pie chart data indicates that although the percentage of bleach
plant color has been reduced by 30% since 1999, it remains at approximately 35
— 36% of total influent color to the treatment plant.
The recommendations in the 2001 BEPER study included several
recommendations for reducing color and operating cost at the Blue Ridge mill.
These recommendations became a base outline for the "Color Reduction
Initiatives Under 2001 NPDES Permit". Those items and additional items
identified by Blue Ridge are shown in the table entitled "Color Reduction
Initiatives/Projects " on page 16.
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Col eduction Initiative/ Project 2002 2004 2006 $
1 2-11— ..—or testing frequency
2 Lieber ou Recommendations Implemented 2001 BEPER Report) incl in#8
3 Use of Off-line Clarifier for Spill Diversion
Hwd Brown Recovery Tank Line to Pine Blow Tower - - l
135,000
I-Hour color testing frequency during maintenance outages 1
Installation of Mechanical Seals clean water segregation) 180,000
Improvement of equipment used for handling Pine and Hardwood Knot Rejects I25,500
Bleach Filtrate Recycle Improvements 1,550,000
hmstalled Fiberline control logic improvements 1,080,000
I 1 Bench-scale sewer-generated color work 5,000
Yl 108,000
TL Improvements made to Pine Brownstock sumps for better recovery 200,800
White Rot Fungus Trial(See note below)* 30,000
C102/Ozone Bleaching of CRP wastestream(See note below)* 15,000
Ozone/C102 ZD Stage for Hardwood bleach line -lab stud See note below)* 30,000
17 2nd Stage 02 delignification on Pine- lab stud (See note below)* incl in# 15
18 Ozone Bleaching of effluents-lab pilot studies See note below)* 35,000
19 1Pine Brown Recovery Tank Line to Hwd Blow Tower incl. in#13
20 Milk of Lime Trial See note below)* 25,000
21 Land Application of CRP wastestream(See note below)*
22 Commercial Incineration of CRP wastestream See note below)*
23 Coagulation/Precipitation of CRP wastestream(See note below)* 12,000
24 Solidification for Land Disposal of CRP wastestreant See note below)*
25 Pine and Hardwood Quaternary Screen Rejects Press 151,000
26 Catalytic peroxide treatment of Eo stream(See note below * _ _ __ _ _ __ _ 15,_000
27 Trial to confirm and size system for C102 de-colorization of CRP/evaluate full-scale - -
a lication trials completed after Sep 04 floods,see note below * 60,000
28 lPeroxide Trials on Hardwood Eo(See note below)* 30,600
29 Green Liquor Sump at recovery furnaces 100,000
30 CRP on Lime Precoat Filter See note below)*
31 Peroxide Trials on Pine Eo(See note below)* 1♦ 15,006
32 Acid Sewer Rerouting 1,535,000
33 Pall Filtration(See note below)* 15,000
34 Color Process Improvement Six Sigma Team to examine operating conditions
associated with good color performance
35 Color Reliabiity Projects-process and monitoring focus to reduce variablity of7wnw, 1 color performance 446,000
Completed Process Change/Evaluation Process Evaluation or Change 1 ,.... Total S 5,898,300
Continued Performance Improvement Expected Performance Improvement
*Intitiative determined not to be technically,operationally,or economically feasible
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These initiatives can be classified into groups, as follows:
Laboratory and Mill Trials
In-Process
External Treatment
Process Controls
Upgrades
We have reviewed the results of each of these initiatives, and have made the
following observations.
Laboratory and Mill Trials
In-Process
Ozone/C102 (ZD) Stage for Hardwood bleach line - lab study
Reference Report Title: "Bleaching Evaluation for Effluent Color Reduction.
Ozone / CI02 (ZD) Stage for Hardwood Bleach Line (Pulp and paper Research
Institute Of Canada, PAPRICAN)
SUMMARY
1. D and (ZD) produced a similar kappa number, although after the next Eo
stage, the kappa number indicated an improved delignification from the
(ZD)Eo sequence, allowing for a reduction in CL02 usage in the next D,
stage to achieve a comparable brightness.
2. An acid stage before the (ZD)EoD sequence improved the bleaching
efficiency, allowing for a reduction in C102 charge from 0.35 to 0.25% in
the last D, stage with the benefit of a 1-point brightness gain.
3. The (ZD) stage failed to reduce the color of the filtrates compared to the
control DEoD sequence; in fact the color was higher mainly from the
increased color emanating from the Eo filtrate.
4. The DEoPD sequence with the addition of 0.7% H2O2 at an increased
temperature from 165 to 180OF and initial pressure from 20 to 70 psig
reduced the color of the filtrate by 20% compared to the control DEoD
sequence.
5. Both the A(ZD)EoD and the DEoPD sequences bleached the pulps to ISO
brightnesses of 87.5-87.6%, yet the color of the filtrate from DEoPD
bleaching was 35% lower than that from A(ZD)EoD.
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6. The strength properties of the pulp after bleaching in (ZD)EoD and DEoPD
were similar to those after the controls DEoD. A slight decrease in the tear
index extrapolated the 5.5 km breaking length was observed after
A(ZD)EoD
COMMENTARY ON THE STUDY RESULTS AND CONCLUSIONS
Summary points No 3 concludes that the effluent color was slightly higher for the
ozone containing sequence with respect to the base case. On examining the
laboratory procedure it can be seen that the quantities of color in each stage
were added cumulatively to obtain the value for each sequence. It is a fact that
mixing equivalent amount of effluent from each individual stage (as occurs in the
mill) produces reactions that may change (higher or lower) the numerical value of
the color in the effluent. In mills, it is also seems dependant on the mill, the
effluent treatment plant operation, the season, and other factors.
The quantity of chlorine dioxide added in the ZD stage is too high. Based on
Oxidation Equivalents OXE, (The amount of a substance that takes up one mole
of electrons when the substance is reduced: CI02 = 74.12 OXE/Kg and 03 =
125.00 .OXE/Kg) a minimum replaced of 1 kg of ozone should have been
sufficient to replace 1.7 Kg of chlorine dioxide. Therefore using 0.428% ozone
and 0.49 % chlorine dioxide as a charge in the ZD stages in effect means a
charge equivalent to 1.23% of chlorine dioxide was used in the D, stage. This of
course would produce a lower value for extracted kappa number, pulp viscosity,
strength, and higher effluent color, which it did.
Although it is clear that the ZD technology will lower color from the first stage, it is
not clear from the results of the lab trials that the total color from the sequence
with ZD will be reduced. However, despite the mill experience at Espanola and
Finland , this technology is not recommended for the Canton mill due to capital
cost and limitations in power availability.
Peroxide Trials on Hardwood Eo, and Peroxide Trials on Pine Eo
Laboratory and mill testing of E, EO, and Eoa treatment of D, treated Hardwood
pulp.
Two laboratory studies and a mill trial reported on the effectiveness or non-
effectiveness of EoP treatment of a D, treated and washed hardwood pulp
The PAPRICAN study concluded that:
The DEoPD sequence with the addition of 0.7% H202 at an increased
temperature from 165 to 180OF and initial pressure from 20 to 70 psig
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CONFIDENTIAL

VGBI
reduced the color of the filtrate by 20% compared to the control DEoD
sequence.
Obviously the quantity of peroxide used in the experiment was too high and
the therefore brightness achieved (82% was also too high) with a small
change in lowering the kappa number; however, the effectiveness in
decreasing the color of the effluent very noticeable.
An issue with this study is that the D, charge of chemical was not
decreased to allow for more efficient use of peroxide. The D2 charge of
chlorine dioxide was substantially decreased
"Hardwood EoP Implementation study" AKZO NOBEL, EKA NOBEL
Laboratory and mill trials.
SUMMARY
The addition of 10 Ib/T of peroxide increased the extraction stage brightness by
5.1 ISO units. This was further increased by 2.2 ISO units with the addition of
magnesium sulfate. The kappa number reduction was 0.2 units when peroxide
was applied alone and 0.3 units when used in conjunction with magnesium. The
replacement ratio for peroxide with magnesium was 0.11, with chelation this
increased to 0.13. This number is based on the extraction stage kappa number.
If EoP brightness is used, the replacement ratio is considerably higher; however,
normally kappa number provides a better indication of peroxide success. The
minimum replacement needed to be cost effective is 0.5.
The results of the mill study closely mirrored those of the laboratory work. The
replacement ratio was 0.12. Although optimization of the process was not
completed, it was clear from the laboratory work and the mill study that the
replacement ratio of 0.5 needed to justify peroxide was not going to be achieved.
CONCLUSIONS
• There were no cost benefits with peroxide addition to the hardwood line.
• Peroxide applied to the extraction stage will increase the brightness and
decrease the kappa.
• Magnesium sulfate will improve brightness gain by approximately 40%
and chelant by a further 50%.
• Recycling of extraction stage filtrate to the D, stage does not hinder the
peroxide reaction.
• The D, stage chlorine dioxide charge should be maintained at
approximately 60% of the total charge applied in the bleach plant.
• Color is reduced by 13% with peroxide addition to the extraction stage at
constant production.
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On page 6 of the report the author's state:
"There are two parameters to consider when looking at the economics of
peroxide application. Both extraction brightness and kappa number are
important. However, the weighting of the two parameters when determining the
C102 requirements in the D2 stage can vary. For softwood, it is primarily the
kappa number that determined the D2 chemical requirements. However for
hardwood, both extraction stage parameters can factor into the equation."
COMMENTARY ON THE STUDY RESULTS AND CONCLUSIONS
There is one clear fact emerging from the two reports, Oxygen and
peroxide addition to the extraction state can lower color of the stage from
13 to 20%, but it is unclear what the overall impact will be on the total
bleach plant effluent color.
"Hardwood Pressurized Peroxide study" AKZO NOBEL, EKA NOBEL
Laboratory and mill trials. .
CONCLUSIONS
• Higher brightness values can be achieved by adding a pressurized
peroxide stage to the present operation (Base 1).
• By adjusting the chlorine dioxide split relative to the mill's standard
operating conditions, the target brightness could be achieved (Base 2).
• The maximum replacement ratio attainable was approximately 0.6
CI02/1-1202 and occurred at a peroxide charge of 0.4%.
• At this replacement ratio, addition of a pressurized stage was not being
cost effective.
• Bleach Plant Effluent color could be reduced by approximately 28% with
the addition of peroxide.
• Pressure did not contribute significantly to either pulp brightness or
effluent color reduction.
COMMENTARY ON THE STUDY RESULTS AND ITS CONCLUSIONS
We do not agree with some of the conclusions in all the above reports, based on
the techniques used in the experiments. It cannot be concluded that a proper
optimized use of Eop stage on the hardwood line is not economical, because
there must be an economic analysis to determine the cost for decreasing the
color of the effluent whether the treatment is internal or external. External
treatment costs are much higher then internal process changes.
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External Treatment
Determined multiple contributors and interaction effects causing Sewer
Generated Color
Bench-scale sewer-generated color work
White Rot Fungus Trial
C102 / Ozone Bleaching of CRP waste stream
Ozone Bleaching of effluents - lab pilot studies
Milk of Lime Trial
Application of Fe-TAML Catalyst and H2O2 for color reduction of hardwood filtrate
Commercial Incineration of CRP waste stream
Coagulation/Precipitation of CRP waste stream
Catalytic peroxide treatment of Eo stream
Trial to confirm and size system for C102 de-colorization of CRP/evaluate full-
scale application
CRP on Lime Precoat Filter
Pall Filtration
Commentary:
The treatments above have all been studied by BRPP. Several reports were
reviewed and our comments are included in the following sections.
Treatment of Five Different Mill Effluents with Ozone
Target of tests
Study of the possibility to achieve a decoloration by ozonation, evaluation of the
behavior of COD, TOC, BOD5, and pH.
Preliminary remarks
All tests have been performed with five effluent samples (40 liters each), sent
August 12th from Canton and received in Bern August 15th. It has been
assumed that the samples were of average quality. All samples have been
stabilized previous to transportation with NaOH up to pH 10.
Samples received: Hardwood EO filtrate HW-EO
Pinewood EO filtrate PW-EO
Hardwood screen rejects HW screen
Pinewood screen rejects PW screen
CRP Purge CRP
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Artificial mix according to the information from Blue Ridge Paper
(mixed in the lab in Bern)
51 % HW-EO
21 % PW-EO
15 % HW-screen
11 % PW-screen
2 % CRP (after sedimentation and prefiltration)
Color: Although the absorption was measured with 4 different wavelengths (436
nm, 465 nm, 525 nm and 620 nm) only the results with 465 nm have been used
for the different calculations.
Reaction time: The tests were performed using 103S's standard pilot equipment.
The time for testing is such that sufficient samples can be taken to provide data
that can be correctly interpreted over the range of expected treatment. It must be
noted that these times are not to be confused with actual design treatment times
in a real plant. Assuming that the ozone absorption in the used pilot equipment
is better than 95 % of the ozone-input, the reaction time in a technical plant can
be calculated because it is limited only by physics and not by kinetics.
SUMMARY Of RESULTS from TEST #1
Based on a total flow of 151 m3/h (all 5 streams together), a decoloration by >
70% (465 nm) with 600 mg ozone/I would end with a total demand of 90 kg
Ozone/h. As a raw calculation 900 kg/h Oxygen and 900 kW energy (with a
ozone concentration of 10%w) would be needed.
Based on a total flow of 151 m3/h (all 5 streams together), a decoloration by > 80
% (465 nm) with 750 mg ozone/I would end with a total demand of 115 kg
Ozone/h. As a raw calculation 1150 kg/h Oxygen and 1150 kW energy (with a
ozone concentration of 10 % W) would be needed.
In order to keep the reactor volume low and to reduce the energy consumption of
the contact system for the ozone, the ozone concentration should be as high as
possible (14 % W).
For a decoloration of > 70 % a reaction time of 15 minutes would be
sufficient, this would give a reactor volume of about 40 m3, adding the gas
hold-up and the foam phase, the volume would be around 50
m3.
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For a decoloration of > 80 % a reaction time of 20 minutes would be
sufficient, this would give a reactor volume of about 90 m3, adding the gas
hold-up and the foam phase, the volume would be around 110
m3.
A pH-control and adjustment before ozonation and a pH-control after ozonation is
requested under all circumstances.
A mechanical de-foaming system with the possibility to add antifoaming agents is
requested.
A vent-ozone destruction system is necessary but a simple gas-washer with a
small fraction of one of the effluent streams would be sufficient, there is no need
for a thermal system and catalytic systems or GAC cannot be used anyway.
TEST#2
Target of this second test program was to evaluate the impact of higher
temperature (50°C and 70°C) on the decoloration effect on the mix of those
5 streams (Hardwood EO, Pinewood EO, Hardwood screen, Pinewood
screen and CRP purge). These tests have been done under the same
conditions as the previous test
The previous results from similar tests with the mix (tests 7a and 8a) have been
confirmed. The same results can be reached also with temperatures between
500C and 700C The temperature have most probably only a minor impact (in
this range) to the ozone efficiency, COD reduction and decoloration. Naturally
the ozone-absorption will be as high as theoretical possible because of the high
reaction temperature and the intensive foam phase. Also the foaming tendency
seems to be independent from the reaction temperature.
The differences in the results are based on the fact that for the two series
different samples have been used.
Ozone absorption:
The Ozone-absorption in a non-foaming system will be lower than 90°C, in order
to increase that to a level of more than 95 % of the input, the residence time and
with this the reactor volume would have to be higher. For the evaluation of the
decoloration efficiency the absorption efficiency is not important at all because all
calculations have been done based on the real absorbed ozone quantities and
not on the ozone input.
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Ozone and plant parameters:
70 % Decoloration 80 % Decoloration
Ozone dosage 450 - 550 mg/I 600 - 700 mg/I
Average dosage 500 mg/I 650 mg/I
IFlowrate 80 m3/h 80 m3/h
Residence time 1 Fi mint tpc 9n mini tpc
Reaction volume 20 m3 26.5 m3
Total amount of ozone 40 k /h 52 k /h
TEST# 3
Target of this third test program was to evaluate the impact of ozone concerning
decoloration to a mix of only two of those streams (Hardwood Eo and CRP-
Purge) under ambient and realistic temperature (50°C) conditions. These tests
have been done under the same conditions as the previous test. The samples
have been filtrated before ozonation because the contact-loop of the pilot-plant in
our laboratory cannot be used with this amount and size of solids. In a technical
plant there is no need to remove those solids for the ozonation.
Artificial mix according to the information from Blue Ridge Paper (mixed at Blue
Ridge Paper), not pre-filtrated
96 % HW-Eo
4 % CRP (after sedimentation and pre-filtration)
The zero-values (analysis of the raw effluent previous to ozonation) of the two
samples showed a considerable difference concerning COD, TOC, and color:
Zero Values COD total TOC Abs.465 nm Color units
Sample 2 used for test tta 1860 mg/I 731 mg/l 0.921 3380
Sample I used for test 12a 2600 mg/l 854 mg/l 1.066 4114
i
Difference 39.7% 16.8% 15.8% 21.7%
Color
Based on the fact that we had two different samples concerning color intensity for
the 2 tests the ozone dosage to reach a decoloration of 70 or 80% is different.
The kinetics of decoloration is in both samples the same, independent from the
quality of the effluent.
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Temperature is of no influence to the decoloration efficiency (at least up to
50°C).
General Comment Primary laboratory testing indicate that ozone at high
concentration can remove color from the 5 mixed stream of effluent namely: 51
% HW-EO, 21 % PW-EO, 15 % HW-screen, 11 %screen 2 % CRP (after
sedimentation and prefiltration or the 2 streams Mixture of 96 % HW-EO and 4
% CRP (after sedimentation and pre-filtration) by 80%
A. Mohammed and D.W. Smith" Effect of Ozone on Kraft Process pulp Mill
Effluent' Ozone Science & Engineering , Vol. 14, NO. 6, December 1992.
Conclusions
The most significant improvement with ozonation was color removal. The
effectiveness of the ozone for removing color highest when the effluent had
undergone biological treatment for secondary effluent, the average reduction in
color removal was 62% for 50 mg 03/L and 83% for 100 mg 03/L.
The capital cost for the system, plus the operating costs, and the acquisition land
to build the retention pond is close to 40 million dollars.
Another major problem is that the mill at the present time does not have the
hydro grid to support the project.
Noting the above and the need for acquisition of land for tertiary treatment of
biological treated full mill effluent is an article with one of the conclusions shown
below
We do not believe ozonation on this scale is economically feasible.
CHLORINE DIOXIDE TREATMENT OF CRP EFFLUENT (Mill Trial)
Internal Report March 2005.
The objective of this trial was to study CRP bleaching with chlorine dioxide
and its impact on mill secondary effluent color.
During the initial part of the trial, parameters were manipulated to understand the
bleaching reaction of the purge stream as well as find optimal parameters to
obtain maximum bleaching efficiency. This part of the trial showed that a
maximum color reduction average of 78.9% was achieved at 40 Ib/hr C102 for a
CRP purge rate of 8.0 GPM although significant gassing off occurred at this
production rate. Continuous color reduction of 68.5% was achieved at 42 Ib/hr
C101 and a purge rate of 10.0 GPM. Additional heat was added through hot
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lGiAl
water dilution in the CRP filtrate in an attempt to use up excessive C102 but did
not prove effective. An acid bias of 15.0% showed to maximize bleaching
efficiency while lower levels of acid bias did not make significant differences in
color reduction. The extended trial period showed a significant color reduction in
5B sewer of 45.1% amounting to a 2023 lb/day decrease. Lab studies show that
this reduction could possibly carry through to secondary effluent and is not
affected by green liquor or dregs mixing. Due to the normal range of variability in
secondary and primary color numbers, this color reduction cannot be verified.
Lab studies also show that the CRP bleaching process achieved 95.6% of
bleaching potential when compared to lab scale CRP bleaching. Lab tests show
that bleaching CRP filtrate with twice the amount of C102 as that of the process
resulted in a color measurement of 5591 ppm compared to the process bleached
filtrate color of 6021 ppm, both adjusted for dilution factors. Due to variability in
secondary effluent color numbers, the color reduction gained in CRP bleaching
cannot be verified in a mill sewer color reduction. Based on the results noted in
this correspondence and all of the issues related to using C102 bleaching of the
CRP purge stream it is difficult to recommend CRP filtrate bleaching using
chlorine dioxide as a solution to reducing color in the mill discharge.
The cost of this type of external treatment would be high. Chlorine dioxide will
also attack other organic constituents of the effluent stream and it would be
important to determine what organo-chlorine compound are produced in the
treatment.
Application of Fe- TAML Catalyst and H202 for color reduction of hardwood
filtrates
Mill Trial Report by Carnegie Mellon University September 2005.
The Data collected from the mill trial at Blue Ridge data suggests that Fe-TAML
concentrations of approximately 0.15 ppm are effective for color removal of
approximately 40-45%. There does not appear to be a significant advantage to
have Fe-TAML concentrations higher than 0.15 ppm. Concentrations of the Fe-
TAML catalyst lower than 0.15 ppm need to be explored in greater detail, but
based on this limited data set and laboratory results, they are likely to require
greater reaction times. In summary, the addition of the Fe-TAML catalyst even at
low concentrations can more than double the color reduction seen with H2O2
alone. The process is easily implemented, requiring only simple delivery
mechanisms. The results also indicate that the existing infrastructure of E, sewer
pipes provides an adequate reaction vessel and time for the color reduction to
take place. Further trial work with Fe-TAML and H2O2 concentrations which are
more closely tied to E filtrate flow should give optimal results.
It was also found in bench tests at Blue Ridge Paper that the Fe-TAML catalyst
and H2O2 could be used to remove color from the Eo softwood sewer, sample
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point 5. The time-scale for this process is currently unknown but tests could be
performed by Blue Ridge personnel under the guidance of Carnegie Mellon to
assess color reduction in this area. If implemented, treatment of E softwood
would presumably be done on an as needed basis.
Estimated annual use and cost of Fe-TAML catalyst. Assumptions:0.15 ppm
Fe-TAML 500 gpm flow for Eo hardwood sewer. Annually use: 330 Ibs Fe-TAML
catalyst. The supplier of the Fe-TAML catalyst used in this trial, Fisher Scientific,
has quoted a cost of approximately $1350/lb for 100 lb quantities of Fe-TAML
catalyst. Fisher Scientific is a small to mid-scale chemical producer and their
costs are higher than large producers. However, they could supply the amount
of catalyst needed by Blue Ridge Paper, but they should not be considered as its
long-term supplier. As production of the Fe-TAML catalyst increases and new
suppliers are identified, the cost will come down. There is a quote from one
large-scale producer that a cost of approximately $275/lb should be achievable,
when production reaches multi-ton quantities. Currently this technology is not
commercially viable because the TAML catalyst is not produced on an
industrial scale. When the TAML was added to the EoP tower in another
study, the catalyst use was lower than when the EoP filtrate was treated.
The TAML may thus be more effective when added in the bleaching
process. This process is currently not technically feasible.
Lime Precipitation
The mill participated in milk of lime treatment trial of filtrate and treatment of the
CRP effluent on lime filter treatment. The mill has declared both initiatives not to
be technically operational or economically feasible.
COLOR REMOVAL-FUNGUS/BACTERIA/ENZYMES White-Rot Fungus
Treatment
Various strains of white-rot fungus have been known to be able to degrade lignin
as a "secondary metabolism," meaning lignin would be metabolized if a certain
growth factor becomes limited. This ability is not lost when the lignin becomes
chlorinated in pulp bleaching, so the fungus has become of interest in removing
chlorolignins and chlorinated phenolics in bleach plant effluents as a means of
reducing effluent color and toxicity.
Several parallel research programs have been pursued and the one most
advanced at this point is the "MyCoR" process at North Carolina State University.
In this process the fungus is immobilized on a series of flat disks, which are
mounted in parallel on a rotating horizontal shaft such that portions of each disk
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are alternately submerged in the waste operation. Either 1- or 2-day retention
time would probably be required (Pellinen, 1998).
Since the fungus cannot use lignin as an energy source, it must be supplied one.
If the stream to be treated does not contain enough energy sources, such as
hemicellulose, suggested possible additives are glucose, xylose, cellulose, or
possibly primary sludge. In addition, the pH should be between 3 and 5, the
temperature between 28 - 40 °C, and nitrogen should be the limiting nutrient.
Other white-rot fungal treatments include the MyCoPor (Messner, 1990) and
immobilized fungal fluidized bed bioreactor.
The MyCoPor process is a trickling filter that immobilizes the fungus on the
surface of polyurethane foam cubes. Both the MyCoR and MyCoPor use
passive immobilization, i.e., adhesion of cells to a solid support.
The immobilized fungal fluidized bed bioreactor uses entrapment of the fungus in
urethane foam Pallerla, 1996). This active immobilization results in a media with
a high resistance to deterioration by mechanical action and pH. This reactor is
effective at removing color and AOX, with removal efficiencies of 70% and 50%,
respectively. The reactor was fed a mixture of 60% D stage effluent and 40% E-
stage effluent which was obtained from a mill with a OD(Eo)DED bleaching
sequence. The reactor functions best at a pH of 5 and due to the porous nature
of the urethane foam, transport processes are non-diffusion limited. As with other
white-rot fungus treatments, an energy source for the cells must be supplied. In
this case glucose at 8 g/I would be recommended along with nitrogen and
phosphorus.
Currently this technology is in the pilot scale phase. Some mill testing has
done but the results were not successful for color removal
Blue Ridge was one of the mills to test the process without success.
Their findings are:
The cost per is $8 to $10 per ton of pulp is expensive.
It did not help color removal
Usually the bioaugmentation is with bacteria, not fungi.
Needed to add glucose or a similar nutrient to the treatment system
This is necessary for fungal color removal, but the mill is also trying to remove
BOD, not add it. Additional BOD means additional aeration, residence time and
biosolids production.
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The fungi grow best at pH 4-5, while the usual bacterial consortia in a treatment
system grow at neutral pH.
The bacteria grow rapidly and consume glucose much faster than the fungi,
therefore there will not be any glucose left for the fungus.
Another research lab found that white-rot fungi can adsorb color initially in the
absence of glucose, but this is not sustainable
One would see a color removal Initially due to adsorption, but the effect will soon
disappear
Fungi need a readily available carbon source to achieve consistent color
removal. In a treatment system the bacteria will rob them of this carbon source.
White Rot Fungus is not currently technically feasible.
Process Controls
Liebergott Recommendations Implemented (2001 BEPER Report)
2-Hour color testing frequency
1-Hour color testing frequency during maintenance outages
Installed Fiberline control logic improvements
Hardwood Fiberline Six Sigma Team for process optimization and color
improvements
Color Process Improvement Six Sigma Team to examine operating conditions
associated with good color performance
Color Reliability Projects - process and monitoring focus to reduce variability of
color performance
Commentary:
It is clear that the color in the mill effluent has been significantly reduced since
the 2001 study. It is, however, quite difficult to assess how much of the
improvement was due to any specific change. However, it is appropriate to
comment on the changes made.
The color testing frequency during normal operation and during maintenance
outages offers the opportunity to more clearly understand changes in effluent
color due to changes in operation of the mill. Unfortunately, it has been
extraordinarily difficult to quantify changes to a specific action, even with the
more frequent monitoring of color.
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A major improvement to the operation of the fiberline has been realized by the
addition of kappa analyzers (suggested in 2001 study) and the repair of the
existing brightness and residual monitors in the chlorine dioxide stages
(recommended in 2001 study). The operation of these instruments has provided
the capability to implement a modern fiberline control system, thus improving
stability of the fiberline and reducing bleach chemical use. This deserves special
commentary, as it likely has had a significant contribution to the reduced color in
the effluent since the 2001 study.
Fiberline Control Logic Improvements
The stability of the PN on both hardwood and pine was identified as a key issue
for further study in the 2001 BPER study. On line kappa measurement and
control has been implemented in both the hardwood and pine lines, in four
locations each, as follows:
"Digester Blow" sampled at the feed to the knotter on HW
sampled at the #3 pre-oxygen washer feed on Pine*
""Post Oxygen" sampled at the feed to the first post oxygen washer
"Pre-Bleach" sampled at the feed to the pre-bleach washer
"CEK" sampled at the feed to the Eo washer
The sample frequency for hardwood and pine is 15 and 20 minutes, respectively.
* The baseline data from the 2001 study was based on lab determined PNs,
with the sample taken at the feed to the knotter. The current Kajaani
sampler takes its sample from the feed to the final pre-oxygen washer.
There is a surge tank between the blow tank and the first stage washer,
with a retention time of 20-30 minutes. The highly alkaline, high
temperature in this tank results in leaching of lignin from the pulp, resulting
in a significant PN drop from the blow tank to the feed to the oxygen
stage. The drop is typically a PN of_ This is significant in analyzing
the performance of the oxygen stage, as typically results are reported from
the digester to the final post oxygen washer. Data from 2005/2006 for
comparison to the 2001 study uses the lab PN data rather than the
Kajaani data.
With the added capability of continuous monitoring of the PN on both lines, it has
been possible to implement a modern continuous control system targeted to
control the Pre-Bleach PN, the CEK number, and the final brightness. The
brightness and residual sensors on the D, and D2 stages continue in use and are
utilized in the control strategy, albeit at a lower bias. At present, the PN is biased
too/o of the feed forward control and the brightness/residual measurements are
biased toa/o of the feedback control. The CEK targets areMfor hardwood
andnfor pine.
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Additional improvements made to improve PN stability is the relocation of direct
steam piping to the hardwood digesters to the bottom elbow of the digester. This
has greatly improved the "cleanliness" and reliability of the digester blow, as well
as the PN uniformity in the digester. These same changes are currently being
implemented on the pine digesters. All steam is now desuperheated, leading
also to improved uniformity of the cook.
Kappa Number Stability
Log Sheet Data for the period of January 16-30, 2006, was evaluated. The
range of PNs in both hardwood and pine was quite wide:
Pre-oxygen PN (HW): minimum maximum _
Pre-bleach PN (HW): minimum - maximum
Pre-oxygen PN (Pine): minimum maximum _
Pre-bleach PN (Pine): minimum maximum _
However, in most days, the control seemed very good, with an approximate
variability s follows:
HW variability
Pine variability
The variability seems to be much improved since the 2001 study. Most
importantly, the operators have a higher degree of confidence that they will be
able to react to pending upsets early enough to avoid off grade pulp. This
improve stability of the PNs is likely responsible for reduced bleach chemical
cost.
Upgrades
Liebergott Recommendations Implemented (2001 BEPER Report)
Use of Off-line Clarifier for Spill Diversion
Hardwood Brown Recovery Tank Line to Pine Blow Tower
Installation of Mechanical Seals (clean water segregation)
Improvement of equipment used for handling Pine and Hardwood Knot Rejects
Bleach Filtrate Recycle Improvements
Improvements made to Pine Brownstock sumps for better recovery
Pine and Hardwood Quaternary Screen Rejects Press
Green Liquor Sump at recovery furnaces
Acid Sewer Rerouting
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Commentary:
It is clear that the color in the mill effluent has been significantly reduced since
the 2001 study. It is, however, quite difficult to assess how much of the
improvement was due to any specific change.
An example of the difficulty in assessing impact is the installation of the
installation of the quaternary screen rejects presses in both the hardwood and
pine fiberlines. These screen rejects, at the time of the 2001 study, were
discharged directly to the sewer. After this change, the rejects were dewatered
to high consistency and burned, while the pressate is now returned to the
fiberline filtrate system. This rejects stream had previously been quantified to be
responsible for about 700 #color/day; however, this reduction could not be found
in the color data in the secondary effluent from the mill. This example illustrates
that there are very complex chemical interactions taking place in the mill
operations and sewer system, and that there is significant risk in investments
made to reduce color, even where the results should be clear.
Improved collection from sumps and improved spill collection during maintenance
outages clearly reduces the number of days with high color in the mill effluent.
This then reduces the overall monthly average color in the effluent.
Improvements in Washing
Some opportunities for improvement in washing were noted in the 2001 study,
with specific recommendations made for improvements. It is well known that
pulp washing prior to the oxygen stage, and pulp washing between bleach
stages, particularly on the Eo stage prior to the D2 stage has a very large impact
on performance and bleach chemical consumption. Several inefficiencies were
identified in the 2001 study, which were addressed soon after the study was
completed
Both Lines (Hardwood and Pine)
The defoamer formulation and additions points were optimized on both the
hardwood and pine lines. It is reported that the washers now operate much more
stable, and are much more responsive to changes in defoamer addition. A
silicone based defoamer is used on both lines with defoamer added at strategic
points in dilution and shower streams on both lines.
In 2003, it was determined that the washing performance on the bleach washers
was deteriorating, as noted by changes in caustic and acid addition for pH
control. Although it was typical practice to hydro blast the decks on the CB
washers, and the wires on the vacuum washers, it was ultimately determined that
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scaling with oxalate scales was more severe than expected. The scale on the
CB washers, for example, was almost totally plugging the drainage channels
under the deck on some washers. A rigorous program of cleaning the drainage
channels and re-decking the CB washers was implemented, as well as hydro
blasting the decks twice per year. Similarly, the hardwood wires are hydro
blasted 4 times per year, and the face wires are replaced every two years. A
preventative maintenance program of chelant washing the washers during
outages is expected to minimize the future scale buildup in the washers. This
program has certainly improved the operating stability on the washers, as well as
the discharge consistency and washing efficiency on all washers.
Improvement in Oxygen Delignification
Several recommendations were made in the 2001 study regarding the
performance of the oxygen delignification stages. At the time of the study both
the hardwood and pine oxygen stages were performing below their capability, in
the range of A target for well run oxygen
stages was stated to be 35-40% and 40-45% for hardwood and pine,
respectively.
The Clove-Rotor pumps that fed both oxygen delignification stages have been
replaced with Sulzer medium consistency centrifugal pumps, as recommended in
the 2001 report. The advantages of this change are:
Increased time between required rebuilds of the pump
Increased discharge pressure, and thus increased reactor pressure.
Reduced cost of rebuild
Air removal capability (less "dead load" gas in reactor)
The results from this change were immediate. The degree of delignification
increased byW/o on both hardwood and softwood, leading to lower pre-bleach
PNs, and subsequently increased pre-oxygen PNs at the same pre-bleach PN.
Concurrently, the dilution that had been added at the discharge of the fourth pre-
oxygen washer on hardwood was eliminated, so the reactor consistency
increased significantly. It is well known that a consistency in the reactor of >10%
is criteria to achieve best delignification in an oxygen stage. It is believed that
this single change resulted in reduced HW Eo color by 2500 Ibs/day
In addition, a steam sparger was added to the pine oxygen delignification stage
to minimize the possibility that any uncondensed steam enters the mixer, and
assuring uniform temperature of the pulp to the mixer. Blue Ridge is evaluating
the addition of a similar steam sparger to the hardwood oxygen stage in 2006.
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Review of Process Operating Data:
Significant changes have been made to the fiberlines since the 2001 BEPER
study. In order to quantify the changes made, operations data was studied to
compare the current operation to that during the 2001 study.
Benchmark data for year 2000 includes the period July-August 2000 which was
reported in the 2001 audit report.
Benchmark data for year 2002 includes the period September-December 2002
for both Line #1 (Hardwood) and Line #2 (Softwood) as this was the only data
provided.
Benchmark data for year 2005 includes the period June-September 2005 for Line
#1 (Hardwood) and April-September 2005 period for Line #2 (Softwood). April-
May 2005 period for Hardwood line was not included due to problems with the
CI02 flowmeter in this line that was replaced by new one on June 3, 2006. Jan-
Mar 2005 period was not included in the data provided to GL&V. Oct-Dec 2005
data was not included in the evaluation as this was the period of time for high
brightness trials.
Operating data during the site by GL&V and Lundberg Associates for the period
May 7-11, 2006 was obtained and presented as another column in the table for
comparison.
Data from those periods were used to establish the Canton operating
benchmarks. Canton benchmark data was compared to the performance
expected for fiberlines of this design. These operating parameters are derived
from GL&V pulping and bleaching operations similar to the Canton operation.
Data on the far right column is the recommended values.
No. 1 Hardwood Fiberline
We have examined the washable Dissolved solids and COD losses from the
brown stock and post oxygen washers in line 1 for the period 1995-2004.
Washing losses from the 4th brown stock washer averaged at
is below the maximum tolerable value of 370 lb
DS/odst and 330 lb COD/odst. Washing losses to bleach plant averaged at=
� that is lower than typical values seen in the industry (22 lb COD/odst).
There was no recent data showing the 2005-2006 period.
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The following tables show the Canton mill operating data for hardwood line
during several periods examined and recommended values.
No 1. Hardwood Fiberline
Stage Parameter Canton Canton Canton Canton Expected
2000 2002 2005 May 7-11,
2006
Pre-02 k-no 10.4
02 02 charge, % 1.5
NaOH, % 2.0
H vat 10.2-10.5
Pressure, si 100
Deli nification, % 40
Pre-bleach k-no 6.3
lab
Pre-bleach k-no 5.7
Kajaani
D, Kappa factor (ad 0.24
basis) 3i
CIOz, 1 0.86
EoP 02, charge, % 0.3
H2O2 charge, % 0.3
k-no 1.7
% ISO 70-72
D2 CI02 charge, % 0.6%
Final pH 3.8-4.0
Final ISO, % 86
Retention, min. 240
Total CI02 charge 1.5
p,+Dz (2)
Note : Delignification Rate is Based on Lab K numbers reported.
Note(2) % CI02 charges are ad basis as read from DCS.
Note(3) Kappa factor is back calculated (on ad basis) from D1 CI02 charge and
Lab K number.
In May of 2001 the IMPCO 1200 HC Clove-Rotor pump that fed the hardwood
oxygen delignification system was replaced with a Sulzer 32-6 MC Pump to
allow for the following:
1. Increased Service Life due to wear and unscheduled mechanical
failure.
2. Available increase in operating pressure of the system due to
inadequacies of the Clove-Rotor design.
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3. Improved efficiency of Oxygen Delignification system due to increased
oxygen effectiveness due to degas capability of MC Pump.
The brown stock line consists of four Pre 02 Coru-Dek washers, one Post-02
Coru-Dek washer, two deckers, and a Pre Bleach Coru-Dek Washer. Oxygen
delignification system includes the following equipment,
- Sulzer 32-6 Medium Consistency Pump
- IMPCO 1200 Series High Shear Mixer
- 10.5 x 85 Ft Pressurized Reactor, Design Retention time is 69 minutes
- Blow Tank
Operational Improvements of System
Average % Delignification Std. Dev Bleachi
Operating based on Kappa Plant K Number
Pressure Number
Clove-Rotor 90 psi �/o
Pum
MC Pump 100 psi /o
As expected with the delignification increase across the oxygen system chlorine
dioxide usage has been reduced in the bleach plant.
Hardwood oxygen delignification system is performing rather good providing
delignification rates in the range/o (based on lab K), the delignification rate
during the GL&V/Liebergott visit period average was W/o. It seems that the
delignification rate has improved continuously since year 2000 and resulted in
lower pre-bleach K numbers going to bleach plant. This in turn contributed,
partly, to lower total CI02 consumption in Line 1.
The applied NaOH (as OWL) charge is adjusted based on the Pre-02 K number
according to the relationship in the following table,
%NaOH (as OWL) = [Pre 02 Kappa - Target Outlet Kappa] * Kf
%02 = %NaOH * 0.70, where target kappa number ism
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Pre OZ Kappa Number Kf
Over this entire range of incoming kappa numbers, according to this table, the
alkali charge demanded by the control system is �/o NaOH per delta
kappa number. Typical average use in the industry for hardwood pulps is in the
range of 0.22-0.28% NaOH per delta kappa, so we believe the control algorithms
are in the best range for oxygen stage operation. Oxygen use is typically about
80% of the NaOH use in the stage, and the algorithm is calling forW/o, a little on
the low side. It was noted that, according to current control algorithms, the
maximum alkali that will be applied under any condition isM/o. Overall, the
control of the oxygen stage seems to be good, and far improved from the
operation in 2001.
The D, stage CI02 charge is controlled using the online instrumentation. The
charge is calculated using the Pre-bleach kappa number and kappa factor
relationship given in the following relationship,
Pre-bleach Kappa Kf %Act Cl (for ref)
The new control strategy, with on line kappa analysis, for CI02 charge in the D,
stage is adequate, however the kappa factor target is higher than needed to get
any benefit from the subsequent Eo stage.
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At present, the D, stage kappa factor, or applied CI02 is still high at=kappa
factor M/o CI02). This is a bleaching strategy common in three stage bleach
plants. It is a typical operator habit in mills to err on the high side of kappa factor
to assure that final brightness is achieved. These pulp and washing systems can
display a great deal of k-number and carryover variability. The process sampling
and testing is now spread over 15 minute periods. A high kappa factor setpoint
in the D, stage is often to reduce the variability in the bleach plant feed and
maintain the final brightness target. However, high kappa factor bleaching often
results in overshooting the final brightness target and excessive overall CI02
usage.
First chlorine dioxide stages that operate at high kappa factors generate
relatively high levels of color in the effluent. However, as discussed previously,
levels of color at the Canton mill are low. This acid color can increase when
subjected to alkali, and often this effect is irreversible.
The mill has now removed the oxygen and peroxide from the extraction stage
due to no appreciable gain in the PN number or brightness in the extracted pulp.
The E stage operates within the standard conditions. The final brightness range
is high ate/o ISO indicating high application of chemical in the D, stage as
no oxygen and peroxide is used. Application of oxygen and peroxide in the
extraction stage at the high kappa factor would have minimum or no effect on the
overall bleaching. Because of the high CI02 charge in the D, stage, a previous
mill H2O2 trial made no impact on overall No. 1 brightness performance.
D2 stage CI02 charge has been adjusted using the online instrumentation. The
amount of CI02 is calculated using the CEK number and Kappa factor given in
the following table,
CE Kappa Kf %Act Cl (for ref)
The final D2 stage is under utilized due to the aggressive D, bleaching previously
discussed. This under utilization is part of the previously discussed operator
strategy, allowing D2 stage brightness recovery. The D2 stage operates at am
pH (earlier it was ® and retention time of approximately = which is
acceptable. The previous lower pH ® was to aid shive reduction. This pH
range typically slows the brightening kinetics of CI02. Given this strategy, there
seems to be adequate retention time at-minutes to reach theta/o ISO
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target. However, further optimization of the screen room performance did reduce
or eliminate the need for this operating strategy.
No. 2 Softwood Fiberline:
We have examined the washable Dissolved solids and COD losses from the
brown stock and post oxygen washers in line 2 for the period 1995-2004.
Washing losses from the 3rd brown stock washer averaged at
This is below the maximum tolerable value of 370 lb DS/odst
and 330 lb COD/odst. Washing losses to bleach plant averaged at -
- that was higher than typical values seen in the industry (22 lb
COD/odst). This is due to bleach filtrate recycle in this fiberline. However, it was
noted that the washing losses from the pre-bleach washer averaged higher than
the washing losses from the post oxygen decker. The bleach filtrate recycle
locations should be examined to reverse this situation. There was no sampling in
years 2005 and 2006, therefore we recommend BRPP to take new samples after
the coming shutdown.
No 2. Softwood Fiberline
Stage Parameter Canton Canton Canton Canton Expected
2000 2002 2005 May7-11,
2006
Pre-02 k-no 16.8
02 02 char e, % 2.0
NaOH, % 2.2
H vat 10.5
Pressure, psig 100
Consistency, % 12
Deli nification, % 45
Post 02 k-no lab 9.2
Post 02 k-no (ABB) 8.3
D, Kappa factor (ad 0.24
basis)is
CI02, % 1.24
Eop 02, charge, % 0.5
NaOH char e,% 2.0
H2O2 char e,% 0.3
Final pH vat 10.5
k-no 2.3
% ISO 62
D2 CI02 charge, % 1.0
Final pH 3.8-4.0
Final ISO, % 86
Retention, min. 240
Total CI02 charge - 2.4
D,+DZ 121
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Note(') : Delignification Rate is Based on Lab K numbers reported.
Note(2) % C102 charges are ad basis as read from DCS.
Note(3) Kappa factor is back calculated (on ad basis) from D1 C102 charge and
Lab K number.
The table above shows the Canton mill operating data for softwood line during
several periods examined and recommended values.
Oxygen delignification system during the 2001 audit was performing at about
W/o delignification due to several inadequacies, which were pointed out in the
2001 study. It is clear from this data that the delignification has been increased
to about'/o by 2005. The delignification rate during the GL&V/Liebergott visit
period average was=/o, but is typically higher than this. The improvements in
the delignification rate were due to:
- Installation of MC pumps in late 2002
- Improvement of#3 BS CB filter discharge consistency
- Improvement of CB washer maintenance program to prevent scale and
plugging of cylinders with fiber
Once the improvement in the 02 system performance is noted, the target digester
kappa was raised byepoint. This explains the increase in both the pre- and post
02 kappa numbers in table above from 2002 to 2005 and 2006.
The applied NaOH (as OWL) charge is adjusted based on the Pre-02 K number
according to the relationship in the following table,
%NaOH (as OWL) = [Pre 02 Kappa - Target Outlet Kappa] ' Kf
%02 = %NaOH ' 0.90, where:
Kappa Number Kf
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In the mid-range of entering kappa numbers, according to this table, the alkali
charge demanded by the control system is about�/o NaOH per delta
kappa number. Typical average use in the industry for softwood pulps is in the
range of 0.17-0.22% NaOH per delta kappa, so we believe the control algorithms
are in the best range for normal oxygen stage operation. We do not have much
experience on the extreme range of incoming kappa (<20 and >32), be we
assume that the results achieved at BRPP have been determined by mill
operations to be proper. Oxygen use is typically aboutW/o of the NaOH use in
the stage, and the algorithm is calling forte'/o, a little on the high side, however
all of these relationships are wood species dependant, so we believe that the
Canton operation has been optimized for this specific mill location, and current
control is likely better than can be achieved by benchmarks to other mills. It was
noted that, according to current control algorithms, the maximum alkali that will
be applied under any condition is=/o. Overall, the control of the oxygen stage
seems to be good, and far improved from the operation in 2001.
The oxygen and caustic charges are higher in 2005 averages and in 2006 May
data compared to the 2002 averages in the oxygen delignification stage. This is
due to the higher kappa number entering the oxygen stage.
The D, stage kappa factor is high at_M/oC102). The control strategy uses
real time measurement and compensated brightness, i.e. non linear predictive
control algorithm based primarily on the inverse relationship between brightness
and residual measurements taken shortly after the chemical addition to maintain
a constant post tower target. The chlorine dioxide charge is controlled based on
the incoming PN number read by analyzer according to following formula,
Pre-bleach Kappa Kf %Act Cl (for ref)
The control strategy for CI02 charge in the D, stage is adequate, however the
kappa factor target is high which limits the benefit that can be obtained from the
subsequent Eo stage. The higher kappa factor control target is due to a similar
operator control strategy as the previously described hardwood strategy. The
No. 2 Line pulping and washing system is monitored more closely than the No. 1
Line, but operation still favors the conservative approach. This also is partially
due to the increased carryover levels around the D, stage due to BFR®.
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The Eo stage final brightness has been decreased from previous high values
(>60%) and consumption of NaOH and oxygen in this stage has been reduced.
D2 stage CI02 charge has been adjusted using the online instrumentation. The
amount of CI02 is calculated using the CEK number and Kappa factor given in
the following table,
CE Kappa Kf %Act Cl (for ref)
Total CIOz charge for softwood seems to be in the range—since year 2000.
The drop seen in hardwood line total CI02 consumptions is not present in
softwood line. The main reason for that is the increase in the target kappa
number from the digester plant by@ points following installation of the oxygen
stage medium consistency pumps.
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No. 1 and No. 2 Fiberline Audit Observations and Recommendations:
The following observations were made from the current operation at the mill. It
was noted that many items on the pine line have been recognized by Blue Ridge,
and have been identified to be resolved during a scheduled outage week
following the completion of this site study.
Hardwood Line Washing
Observation: Washing efficiency of the hardwood washers can be
improved (vat level and shower application).
The hardwood line consists of four vacuum brown stock washers, a single stage
oxygen delignification stage, one post oxygen washer followed by the screen
room, a decker, and a pre-bleach washer.
Recommendations:
Improve performance of HW vacuum washers (general)
Reduce feed consistency
Increase vat level
Correct shower pipe alignment
Future - replace shower bars with more modern design
(Note: BRPP has an ongoing project at mill to replace showers on
the washers, with the #1 HW BSW and #1 HW POW completed,
and the Pine decker showers to be replaced in May 2006
1. Feed Consistency to washers
The feed consistency to each washer appeared to be higher than the
optimum of 1.25% (OD basis) for best pulp formation; however, the pulp
sheet discharged from each washer appeared to be fairly uniform, so it is
not so high that it is a serious issue. However, an improvement in
washing efficiency can likely be achieved by reducing the feed
consistency somewhat.
2. Washer Vat Level
When the feed consistency is reduced, the washer drum speed will
increase to maintain the vat level. However, concurrently, the vat level set
point should be raised, so it is likely that the drum speed will remain about
the same as present when reducing the feed consistency in combination
with increasing the vat level. The optimum vat level should result in a
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"cascade" of pulp from the inlet weir to the vat level of 6-12". At this level
of "cascade", good mixing will be achieved, without significant air
entrainment and foam generation. There is a potential for a slight
decrease in defoamer use. This is shown in the figure below:
WAB m CnH1BEN RMATWN
FULP MAT
INLET � e / DOCTOR
BOM "El WEIN 3
DISPLACEMENT \'
ENi ZONE
ATMOSPHERIC
i NEOFF20NE
EXTRAC➢oN ZONES RAW \\
FORMATION
I
ORMATON ZONE
VACI,UM
FORMATION ZONE
PULP DI51 RIBUT10I
BAFFLES
BILIRNIN
3. Washing Shower Application
Another of the items that is an opportunity for improvement in the washing
system are the shower bars on all the washers. The wash water
distribution across the face of the drums as well as the application rate per
shower bar is in need of improvement.
At present, the individual shower nozzles on each bar are not properly
aligned to place wash water on the sheet without sheet disruption, and
some nozzles are plugged. With the current arrangement the issues are:
a. The angle the shower liquor is applied is incorrect. The shower
nozzles should be postioned to "lay a blanket" of wash liquor on the
sheet uniformly. Currently, each nozzle is directed to impinge the
wash liquor directly into the sheet, causing sheet disruption and
pulp "roll back" to the inlet box.
b. Although difficult to observe each shower bar operation due to the
environment under the hood, it appeared that the flow rate through
each shower bar is neither equal, nor are all nozzles operational
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VIGIN
(likely plugged). This is a result of improperly aimed shower bars
and the variability of each individual nozzle on the bars
All showers need to be cleaned and adjusted to give the best shower
water distribution without impinging the wash liquor into the sheet.
The mill has an ongoing program to replace shower bars with modern
design, higher efficiency shower bars on additional washers in the
hardwood line.
4. Drop Legs and Drop Leg Vacuum
The feed and discharge consistency on each washer should be sampled
(composite sample 5 locations across the length of the drum). With this
data, along with the produciton rate and shower flow on the washer, a
filtrate flow can be calcuated. Preferably this data should be collected
before and after the recommendations in items 1-3 above are
implemented. The drop leg velocity should be checked to assure it is in
the correct range for best performance. It will be necessary to know the
inside diameter of the installed drop legs. The flow rate in the drop leg
calculated should be used to calculate a "superficial" velocity (disregard air
content) in the drop leg by calculating the velocity.
For conventioanal washers, the "superficial velocity' should be 9-12
ft/sec., and for "low air" type washers, like "Coru-DeC" washers, the
"superficial velocity should be 12-16 ft/sec.
Observation: The discharge consistecy on the hardwood deckers is
very low (4/6).
Recommendation:
Improve operation of the hardwood deckers to improve the discharge
consistency (if additional changes are needed other than shower
adjustment and vat level changes).
Although the general operation of the hardwood deckers appeared good, the
discharge consistency from the deckers is very low. Decreasing the feed
consistency and increasing the vat level may improve the discharge consistency.
In the event the improvments is not achieved by these changes, further study
should be initiated.
The hardwood deckers are 9'6" diameter by 16'0" long Coru-Dek washers, with
two machines operating in parallel. This results in a washer surface area of
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about 960 ft2 for both deckers. A production rate of-is roughly_
M(brown pulp) is a "specific loading„ on the deckers of _
There are many Coru-Dek washers operating on
hardwood pulp with good discharge consistency at over 1.0 odtpd/ft2 �/o
higher than the Canton operation), so we believe that there is opportunity for
improvement of the performance of these deckers by process optimization
(operating conditions, air entrainment), shower application (design and
adjustment), valve adjustment or type, etc.
Observation: Wash liquor bypasses are operated on the hardwood
deckers.
Recommendation:
Evaluate elimination of wash water bypasses
Shower to washer vat on hardwood deckers
Bypass of Eo filtrate to Decker Filtrate Tank; move application to
Decker Showers or potentially other washer (Washing system
performance may be improved by changes to recycle strategy;
needs further study)
It was noted that, on the decker, a pipe was installed just below the first shower
bar with liquor being added directly to the vat. Any liquor added at this point
bypasses the washing showers and reduces the dilution factor applied to the
washer. As the washing efficiency is a strong function of the dilution factor,
elimination of this liquor bypass should result in an improvement in washing
efficiency. The impact on washing by eliminating this bypass depends on the
amount of bypass flow, which could not be determined. It is possible that this
pipe was installed to dilute thickening in the vat which can occur during upsets;
however, it must be stressed to the operators that use of this dilution should be
reserved only for emergencies, and the flow shut off immediately after achieving
stability of operations.
For reference, the calculations associated with the dilution factor and
displacement ratio are included in Appendix 4.
Observation: The Eo filtrate recycle to recovery bypasses two
washing stages.
A portion of the Eo filtrate is returned to recovery by using it as wash liquor in the
brown stock washing system. This filtrate is pumped to the decker filtrate, rather
than using it as shower liquor. On the hardwood line, about=GPM is returned
continuously by pumping to the decker filtrate tank. In principle, bypassing
washer showers with subsequent liquors decreased washing system efficiency.
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However, the Blue Ridge Paper Pine Fiberline is quite unique due of the
implementation of the BFR® process. This location was determined through
extensive material balances performed for commercial implementation of this
unique process. Several years later, the hardwood Eo filtrate was also recycled
to a certain extent.
The location of applicatoin of the Eo filtrate into the brown stock washing system
should be evaluated according to the current mill operations. There may be a
benefit to relocate the application point from the decker filtrate tank to the decker
showers, or other location, to minimize the degrees of filtrate bypass around the
washers.
Hardwood Line Bleaching
Observation: The degree of delignification in the oxygen stage is
significantly improved compared to the 2001 BEPER
study.
The degree of delignification reported in the 2001 BEPER report was 33%, while
the expected range of operation was noted to be 35-40%. Specific action items
recommended were improvements in washer operation, and replacement of the
Clove-Rotor pump with at centrifugal medium consistency pump. Both of these
action items were completed, resulting in much improved degree of
delignification off'/o.
Observation: Oxygen is no longer used in the extraction stage of the
hardwood extraction stage.
Recommendation:
Evaluate the use of oxygen and peroxide fortification of the extraction
stage, at reduced D, kappa factors.
Since the first commercial implementation of oxidative extraction stages,
economic benefits of this technology have been almost universally achieved. In
addition, a benefit in color reduction has been reported for the use of Eo and Eop
compared to a conventional extraction stage. One isolated example of a mill that
did not achieve beneficial economic results was a mill in the US that operated on
a wood mix that was largely red oak, and operated at a very high kappa factor in
the Do stage.
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Oxygen Charge to Hardwood Eo Stage
It was suggested in the 2001 study that a trial be done to reduce the oxygen
charge to the hardwood Eo stage to 0.3%. A charge of 0.3% is very typical in the
industry for this application. Such a trial was performed by gradually reducing
the charge from 0.5% to 0.3% to 0.05% and ultimately to 0%. It was noted that
no change in bleach chemical use was noted when eliminating the oxygen
charge to this stage, so it has been shut off.
It is quite likely that the reason that no positive impact is achieved adding oxygen
to this stage is that the CEK number is already so low that there is not sufficient
lignin present for the oxygen. This is an indication that the kappa factor is too
high in the D, stage, and reducing the kappa factor should allow sufficient lignin
to be present to be removed by the oxygen in the Eo stage. A further indication
of the abnormally high kappa factor is the very high brightness from the Eo
washer off/o ISO. Reducing the kappa factor should reduce the total active
chlorine required, and moving more of the color in the effluent to the alkaline
sewer, which is believed to be more "treatable" in the treatment plant.
Another factor that may come into play is the high manganese (Mn") content in
the pulps and liquors in the mill, typically aboutappm from the D, washer. It is
known that high levels of Mn"will negatively affect the efficiency of oxygen and
peroxide stages. However, we believe that this needs to be investigated in a
disciplined laboratory study.
Careful consideration must be given to the optimum operating conditions in the
stage (temperature, pH, pressure, time, D, kappa factor, etc.) in order to
maximize the benefits of the technology. This recommendation will not be
successful without simultaneously addressing the target kappa factor in the D,
stage.
Hydrogen Peroxide Trial in Hardwood Eo Stage
Several mill trials and laboratory studies were run on mill pulp to attempt to study
the effect on operating cost and effluent color. The conclusions from these trials
and studies were:
The replacement ratio of CI02 displaced per unit H2O2 was insufficient to
maintain or lower the bleach chemical cost.
There was not significant impact on hardwood Eo effluent color.
For these reasons, no further work was done.
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We believe that peroxide addition to the Eo stage should, at low application rates,
be cost effective, and at low and high application rates, should reduce effluent
color in the EoP stage. We have reviewed the mill trial reports, and the laboratory
study data, and included our commentary on the work done to date in the earlier
section entitled "Review of Color Reduction Initiatives since 2001".
Observation: The kappa factor target for hardwood pulp bleaching is
high compared to recommendations in the 2001 BEPER
study.
Recommendation:
Decrease target kappa factor to
A recommendation was made in the 2001 BEPER study that the kappa factor on
hardwood pulp be reduced. The kappa factor at the time was observed to be
about= but it has now been realized that the kappa factor was reported on an
air dry, not bone dry basis. This means that the kappa factor was actually
running about_ The recommended kappa factor is 0.22 bone dry, or 0.24 air
dry. The current strategy for kappa factor control was reviewed. At the target PN
of-the kappa factor target is about
At this very high kappa factor, there is little lignin left after the D, stage to gain
any significant economic or color benefit in the subsequent extraction stage.
The objective of this work is, in principle, to force less acid and more (lesser
colored vs. E stage, more easily removable) alkaline effluent color in the total
bleach effluent. The 2005 average color in the Di effluent is 5.7 # color/t and in
the E stage is 4.6 # color/t, which is very good color performance. Addition of
oxygen and peroxide will be at least additive, and may by synergistic.
Pine Line Washing
The pine line consists of three stages of CB washers, a single stage oxygen
delignification stage, one CB post oxygen washer followed by the screen room, a
vacuum decker, and a pre-bleach CB washer.
The operation of the Compaction Baffle Washers on the pine line has improved
dramatically since the 2001 Study. There were a number of issues that were
addressed after issuance of the 2001 report, as discussed in the section entitled
'Review of Color Reduction Initiatives since 2001. These will not be repeated
here.
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No significant changes are recommended for the operation of the washers, but
as always, continuous optimization by periodic training sessions for the operators
is a good plan.
However, some observations were made relative to the operation of the pine
decker, and the filtrate recirculation.
Observation: Washing efficiency of the softwood line decker can be
improved (vat level and shower application).
The pine decker, at the time of the site survey, was being operated in a similar
manner as the hardwood deckers previously discussed. The same
recommendations regarding feed consistency, vat level, washing shower
application, and drop leg and drop leg vacuum are pertinent, so the discussion
will not be repeated here.
Recommendations:
Improve performance of the Pine decker
Reduce feed consistency
Increase vat level
Correct shower pipe alignment
(Note: BRPP has an ongoing project at mill to replace showers on
the washers, with the #1 HW BSW and #1 HW POW completed,
and the Pine decker showers to be replaced in May 2006
As with the hardwood line, a similar observation was made regarding wash liquor
bypass from the Eo stage to the decker filtrate tank (bypassing two stages of
washing). However, it is clear that this location for the recycle on the pine line
was identified after careful study when implementing the BFR process.
Therefore, it is likely the optimum location for this recycle on the pine side. It has
been recommended that the bypass that has been installed on the hardwood line
be reviewed to see if the hardwood washing can be improved by relocation this
recycled liquor. The hardwood line is a much lower flow of liquor, and it is not
recycled to the BFR process, so the optimum location for this bypass may be
different. Once evaluated, and if the hardwood bypass is relocated to the benefit
of bleach chemical consumpion and/or color in the effluent, then the pine side
bypass locatoin should be studied to see if a similar benefit can be achieved.
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Pine Line Bleaching
Observation: The degree of delignification in the oxygen stage is
significantly improved compared to the 2001 BEPER
study.
The degree of delignification reported in the 2001 BEPER report was 40%, while
the expected range of operation was noted to be 40-45%. Specific action items
recommended were improvements in washer operation, and replacement of the
Clove-Rotor pump with at centrifugal medium consistency pump. Both of these
action items were completed, resulting in much improved degree of
delignification of aboute/o.
Observation: Hydrogen Peroxide is not used in the Eo stage of the
pine bleach plant.
Recommendation:
Evaluate the use of peroxide fortification of the Eo stage, at reduced D,
kappa factors.
Peroxide is used in many pine bleach plants around the world as a cost effective
way to reduce the chlorine dioxide use. Typically up to 6# H2O2 A is used to
achieve this benefit. However, it is likely that the benefits of peroxide use in the
Eo stage at Canton are not realized is due to the very high kappa factor used in
the Di stage.
As with the hardwood line, another factor that may come into play is the high
manganese (Mn") content in the pulps and liquors in the mill, typically about
ppm from the D, washer. It is known that high levels of Mn" will negatively affect
the efficiency of oxygen and peroxide stages. However, we believe that this
needs to be investigated in a disciplined laboratory study.
Careful consideration must be given to the optimum operating conditions in the
stage (temperature, pH, pressure, time, D, kappa factor, etc.) in order to
maximize the benefits of the technology. This recommendation will not be
successful without simultaneously addressing the target kappa factor in the D,
stage.
Hydrogen Peroxide Trial in Pine Eo Stage
Several mill trials and laboratory studies were run on mill pulp to attempt to study
the effect on operating cost and effluent color. The conclusions, as with the
hardwood line studies suggested that the use of peroxide could not be
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IGBI
economical justified. However, we believe that significant benefits may be
obtained by the optimum use of peroxide in this stage, and, if successful, may
lead to a reduction in color in the pine Eo sewer.
Observation: The kappa factor target still for pine pulp bleaching is
very high compared to recommendations in the 2001
BEPER study.
Recommendation:
Decrease target kappa factor to
A recommendation was made in the 2001 BEPER study that the kappa factor on
pine pulp be reduced to the range of The kappa
factor is currently about- This is still a little high to get the best
benefits in the subsequent extraction stage.
The objective of this proposed change is, in principle, to force less acid and more
(lesser colored vs. E stage and believed to be more easily removable) alkaline
effluent color in the total bleach effluent. The 2005 average color in the D,
effluent is 4.7 # color/t and in the E stage is 7.6 # color/t. Additional benefits from
the added oxygen, plus added benefits of peroxide addition should reduce the
color in the extraction stage effluent.
Summary of Recommendations:
The following recommendations are suggested to incrementally improve the
present process operations of the No. 1 and No. 2 Fiberlines, with minimal capital
investment.
Hardwood Line
Washing
Improve performance of HW vacuum washers (general)
Reduce feed consistency
Increase vat level
Correct shower pipe alignment
Future - replace shower bars with more modern design
Ongoing project - #1 HW BSW and #1 HW POW; SW decker
showers to be replaced in next maintenance outage
Improve operation of the hardwood deckers to improve the discharge
consistency (if need changes other than shower and vat level changes).
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Evaluate elimination of wash water bypasses
Shower to washer vat on hardwood deckers
Evaluate elimination of bypass of Eo filtrate to Decker Filtrate Tank; move
application to Decker Showers or potentially other washer— needs
further study (Washing system performance may be improved by
changes to recycle strategy; needs further study)
Bleaching
Evaluate the use of oxygen and peroxide fortification of the extraction stage, at
reduced D, kappa factors.
Decrease target kappa factor to force less acid and more (lesser colored vs. E
stage and believed to be more easily removable) alkaline effluent color in the
total bleach effluent— current D, is 5.7 # color/t and E is 4.6 # color/t.
Pine Line
Washing
Improve performance of Pine decker
Replace shower pipes to allow increased flow reliably (scaling in pipes)
Install shower pipes with proper alignment (new showers to be installed in
the next maintenance outage)
Bleaching
Evaluate the use of peroxide fortification of the extraction stage to reduce Eo
color- current Di is 4.7 # color/ton and Eo is 7.6 #color/ton.
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Overview of Technology Options
Introduction
The color in pulp and paper industry wastewater results from four major
operations: chemical pulping carryover from washers, spills and other losses,
pulp bleaching chemical reactions of lignin and carbohydrate fraction of pulp and
from colored paper production. Unfortunately, the compounds responsible for
color are not easily biodegradable. The highly polymerized nature of the
chromophores accounts for their biorefractory nature. Secondary biological
treatment plants typically provide a 20-40% reduction in color load.
Color problems may be handled in three ways: control color within the system by
using oxidative chemicals, a recycle system that allows recovery and burning, or
external tertiary treatment.
During the course of the 2001 Study, a number of options were identified that
may be considered to improve environmental performance, particularly in respect
to the outfall of color. Reduced color in the effluent can be achieved through in
process changes or by treating effluents externally. Both options were reviewed,
and projections made as to the potential benefit each option may offer.
In-Process Options
Decreasing Effluent Loading
As bleached Kraft pulp mills in North America strive to comply with stricter
effluent quality regulations, most of them have stopped using chlorine as a
bleaching chemical. Because of the variety of the mills, they have found different
ways to modify their bleaching sequences to reduce AOX, color and other
compounds in effluent discharges. The number of alternatives to elemental
chlorine bleaching is growing as a result of accelerated research carried out by
pulp producers, research institutions, chemical producers and equipment
manufacturers. There are at least thirty different methods in pulping and
bleaching to reduce the lignin content of pulp and to modify the bleaching
processes, and integrate system closure alternatives, as shown in the following
table.
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Technologies to Reduce Bleaching Pollution
Process Technique Options
Reduce lignin in Extended MCC, EMCC
pulp delignification
Kraft RDH, low solids
Su erbatch
Additives Anthraquinone
Pol sul hides
Other cooking Organic solvent Alcell
chemicals Organocell
Others
Sulphite ASAM
Others
Partial Oxygen 02 delignification
delignification Eo
before chlorination Eop
Pressurized PO
PHT
QP
00
Enzymes
Peroxide P and pressurized
PO
PHT
Non-chlorine Ozone ZD, DZ
substantial Peracids
replacement PXA
Activated oxvqen
Reduce or Treatment Addition
eliminate chlorine conditions Mixing
compounds in Substitute CI02 for pH
delignification Cl2
Reduce chlorine Peroxide P
compounds in Pressurized PO,
brightening PHT
Peracids Peracetic Acid
Ozone PXA
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Pulping Technologies
The retrofit of existing batch or continuous digesters to extended delignification
technology would be prohibitively expensive in most mills and technically
impractical in many of them. Those mills that install extended delignification will
generally install new digester systems. Excessive kappa reduction in extended
delignification can adversely affect pulp strength and yield, but this loss can be
mitigated by the addition of anthraquinone or polysulfide.
Oxygen delignification can be easily implemented into existing mill operations. It
should be noted that the Canton mill has this technology in place. This
technology is now well established commercially with more than 200 installations
worldwide (14 in Canada and 56 in the USA). This trend is expected to increase
in the next 5 to 10 years. Although oxygen delignification has a high capital cost,
it provides significantly lower operating costs.
Technically, pulping modifications such as extended delignification and oxygen
delignification are readily integrated into the liquor cycle. As these technologies
redirect organic material away from the effluent and into the liquor cycle, they
increase the recovery boiler loading that will adversely impact pulp production
capabilities in a recovery limited mill.
Since extended delignification and oxygen delignification reduce the kappa
number of pulp entering the bleach plant, bleaching chemical application can be
reduced.
Extended Delignification
Extended delignification in cooking is an option for reducing the lignin content of
the pulp going to the bleach plant. Lower kappa numbers entering the bleach
plant reduces bleaching chemical usage, and therefore minimizes the effluent
load from bleaching. Extended delignification results in improved selectivity,
lower rejects, and improved yield. The benefits of extended delignification can
be achieved by(1-3):
i) High sulfide concentration during initial and early bulk phase of the
delignification,
ii) Low and uniform alkali concentration throughout the cook, and
iii) Removal of dissolved lignin from the reaction medium.
This technology can be practiced in either continuous or batch digester systems,
and has the following benefits:
• Lower effluent discharges
• Chemical cost savings
• Maintain or improve pulp quality
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• Suitable for short sequence bleaching
• More selective than conventional cooking
• Improved bleachability of pulp
• Improved yield
These benefits are achieved by providing for the reduction in cooked kappa
number without a prohibitive yield loss that would be encountered in conventional
cooking processes. For example, softwood pulp, in conventional batch or
continuous digesters commercially operate in the range of 28-32 kappa number
as an optimum economic point considering all costs of steam, power, bleach
chemical, wood use, etc. Applying the principles of extended delignification will
allow for a reduction in kappa number by about 6.5 units, while maintaining the
same wood consumption (same yield). This results in a kappa to bleaching in
the range of 22-25. This lower kappa number results in lower bleach chemical
costs.
It is possible, with extended delignification, to cook to even lower kappa pulp,
with good preservation of yield down to about a kappa number of 18-20 for
softwood pulps; however, below this point, the yield drops dramatically. With this
yield drop comes a reduction in production capacity in a recovery boiler limited
mill. This makes operation of this process to such low kappa numbers not
economically feasible. Mills that are currently operate at these very low kappa
numbers are producing TCF pulps, where brightness cannot be achieved unless
the kappa number to bleach plant is extremely low.
Oxygen Delignification (Installed at Canton)
Oxygen delignification systems were developed in the late 1960's and early
1970's in order to minimize and/or avoid the cost of external effluent treatment
facilities. This technology provided a significant reduction in lignin content to the
bleach plant by delignifying with oxygen and alkali and returning the dissolved
wood solids to the recovery boiler. Early oxygen delignification systems were
practiced at high consistency (30%) as it was perceived to be difficult or
impossible to mix sufficient quantities of oxygen gas with medium consistency
(10-14%) pulp to achieve the delignification effect. In the early 1980's, the
advent of the High Shear mixer allowed the practice of oxygen reinforced alkali
extraction (Eo) and subsequently oxygen delignification stages.
Since the development of the High Shear Mixing Technology, most of the oxygen
delignification systems have been installed to operate at medium consistency,
and integrated into existing fiberlines that conventionally had drum type washers
operating at medium consistency discharge. The release of solids dissolved in
the oxygen delignification stages requires careful consideration of pulp washing
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requirements both before the oxygen stage and after the oxygen stage (prior to
the bleach plant). Normally 3-4 stages of washing are required before the
oxygen stage, and 2-3 stages of washing are required between the oxygen stage
and the bleach plant.
Recently, there have been numerous configurations of oxygen delignification
system installed and operated commercially. Two-stage oxygen delignification
systems, either before or after the first chlorine dioxide delignification stage are
also operating commercially. Several different types of oxygen delignification
systems are shown in the simplified schematics as follows:
"Mini" design, 15 minutes,
25 - 30% kappa drop
Single stage, 60 minutes,
L 40-45% kappa drop
Two stage, 15/60 minutes,
50-55% kappa drop
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The level of delignification to be achieved in a mill is site specific, and the
average levels of delignification cited above are averages that may be achieved
with these various technologies for softwood pulps. There have been a number
of surveys done on oxygen delignification performance in mills around the world,
and the variability is quite wide. One such survey(4), which included 14 mills in
the U.S. and Canada showed an average delignification in single stage systems
medium consistency systems of about 35%, with two stage systems in the range
of 39-40% (one high consistency system response showed 50% for that
installation). A more recent study in Canada in 2003 reported that the average
delignification for all types of oxygen stages (single and two stage, high and
medium consistency) on softwood pulps was 42% and for hardwood pulps was
34%.
There are a number of factors that can contribute to limited performance in
delignification, which are particularly applicable in `retrofit' installations:
High Solids Carryover to the Oxygen Reactor
Low Consistency to the Oxygen Reactor
Poor Oxygen Gas Mixing
Low Reactor Pressure
Limited Steam Availability
However, it is clear that a well designed and operated oxygen delignification
system can achieve an average delignification of 45% for a single stage systems,
or 55% for a two stage system on a typical softwood pulp. Beyond this level of
delignification, the selectivity of the reaction becomes poorer, and excessive
viscosity losses can occur, which may lead to a concurrent loss in pulp strength.
To achieve these averages requires disciplined operating practice, and good
control of kappa number to the oxygen stage, as well as good washing upstream
of the reactor.
It is known that there are a few oxygen systems in the world, which achieve
greater than 55% delignification on a regular basis. However, many of these
installations are on acid sulfite pulps or on Kraft pulps where the oxygen stage is
preceded by an acid wash or chelation stage. The incremental benefit in
chemical savings to achieve 60-65% delignification versus 55% delignification is
too small to economically justify the installation of such a pre-oxygen stage in a
retrofit installation. In most cases, on Kraft pulps, this type of system is installed
where maximum delignification is demanded and/or in new fiberline installations
where TCF pulp is produced. For TCF pulps, it is known that the kappa number
to the bleach plant must be maintained well below 10 to achieve reasonable
brightness, and pulp strength approaching that of conventional ECF Kraft pulps.
There are two installations in North America where >55% delignification is
claimed to be achieved on regular basis (reported 60-63%), however, this should
Pubic Version - Nov 2006 CONFIDENTIAL 11

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be checked by reviewing long term averages from several months' of operating
logs. If this investigation confirms the long term average results of >60%
delignification, it may be due to wood species dependant, or may be viable due
to final product quality specifications. In any case, the Canton pulps should be
tested to quantify the oxygen delignification response on Canton pulps, before
projecting a long term average result of greater than 55% delignification.
There are numerous publications that address the issues of oxygen stage
performance in relation to ECF and TCF bleaching of Kraft pulps (5-12).
A schematic diagram that shows the required equipment to convert a single
stage oxygen delignification stage to a two stage systems is shown in the next
figure.
The implementation of two stage oxygen delignification on softwood pulp can
result in a reduction of the kappa to the bleach plant by about 1.5 units (increase
in delignification from 45% to 50%), the capital investment will be very high
compared to the reduction in chlorine dioxide that will likely be achieved (- 2.5#
CI02/t). Further, since a major portion of the pine alkaline effluent is recycled to
the BFR process, any benefit will be diminished. On hardwood pulp, the
delignification achieved is already >40%, and was reported to be 47% just prior
to the site survey, so it is unlikely that any significant benefit can be achieved by
the additional of a second stage reactor on hardwood pulp, while retaining target
viscosity and strength of the bleached pulp. This conclusion depends on
maintaining optimum operation on the hardwood single stage oxygen system to
consistently achieve a nominal 45% delignification.
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0'
Retrofit of a Single Stage Oxygen Delignification System to a Two Stage System
Cn
o'
0
< 60 Min.
N 0 Reactor
L
Discharger
Pulp in 10-30 MinPre- ReactNaOH,0 LP SteamNaOH
Oz
Oz
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MP Steam
CONFIDENTIAL

VGUI
Bleaching Technologies
Acid Hydrolysis Treatment for Removal of Hexenuronic Acids
Hexenuronic groups (Hex A) are formed in Kraft pulp cooking when methanol
groups are split off from xylan while transforming the glucuronic acid components
to unsaturated hexenuronic acid units. The hexenuronic acids contribute to the
use of higher kappa factors and thus more chlorine dioxide use and more color in
the delignification D, stage.
The impact on hardwood pulps is higher than on softwood pulps and higher for
oxygen delignified pulps than for pulps without oxygen delignification. The
hexenuronic acids consume bleaching chemicals (all except oxygen and
peroxide). The hexenuronic groups also provide anionic sites to bind transition
metals and heavy metals to the pulp, the presence of which contributes to pulp
color reversion and aging of the pulps, and if peroxide bleaching is employed, to
the peroxide decomposition by free radicals. Removal of the Hex A groups can
thereby also reduce the peroxide consumption.
In general, softwood pulps contain fewer hexenuronic acid groups than hardwood
pulps. Therefore, the removal of hexenuronic acid groups from hardwood Kraft
pulps prior to bleaching can provide substantial reductions in chlorine dioxide
consumption, and thus less color in the effluent. Savings of chlorine dioxide in
the bleaching of softwood pulps are less. In addition, the various cooking
methods impact the hexenuronic acid content of the pulp.
The impact of the Hex A groups can be decreased by the introduction of a
selective hydrolysis step in the bleaching sequence, generally as a first stage
following the last brown stock washer. The selected acid hydrolysis may be
performed at conditions optimized for different pulps. Testing has been carried
out at pH 3-5, temperatures 50-1150 C for times from 30 minutes to 5 hours.
Although not all the Hex A acids were removed from a hardwood pulp, the table
shown below indicates favorable results. Savings of chlorine dioxide and
reduction in effluent color were obtained at temperatures of 500 C to 700 C for 30
minutes.
Although the hot acid stage is an interesting technology for many greenfield mills,
it is not appropriate for a mill design like Canton, where a major amount of the
bleach effluent is recirculated to recovery. In fact, the implementation of a hot
acid stage at Canton will result in increased effluent flow, and likely increased
color in the effluent.
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Effect of Time and Temperature in the Pre-Acid Stage on CI02 Use
HARDWOOD KRAFT PULP
Kappa No. 13.2, Viscosity 28.4 mPa.s
Brightness 39.4% ISO
BLEACH SEQUENCE A D, EoP D2
Acid Stages Basic 1 2 3 4 5 6
Case
Temperature, °C 50 50 70 70 90 90
Time, min. 30 180 30 180 30 180
D, staae (ADo)
C102 charge, % 1.20 0.80 0.79 0.79 0.77 0.77 0.77
EoP stage 1.7/.5/.3 1.7/.5/.3 1.7/.5/.3 1.7/.5/.3 1.7/.5/.3 1.7/.5.3
Charge NaOH,/O2/P 1.9/.5/.3
D2 stage 0.6 0.6 0.6 0.6 0.6 0.6
C102 charqe, % 0.7
8riahtnPss_°ln_1S0 85.8 86.1 86.3 86.7 86.6 86.9
Total C102, % 1.9 1.4 1.39 1.39 1.37 1.37 1.37
C102 savings, % - 0.50 0.51 0.51 0.53 0.53 0.53
Color, Ibs/Ton AD Basis 11 9 8 8 8 8 8
Hot Chlorine Dioxide Delignification Stage
Conventional chlorine dioxide bleaching (Do stage) is usually conducted at 50-70
°C for 30-60 minutes. One option that has been studied to improve D stage
bleaching is to raise the reaction temperature to 85-950C and extend the reaction
time to 90-150 minutes in a so called DHT or D* stage. Most work with hot C102
bleaching has focused on hardwood pulps because they seem to give better
results in a hot D stage than softwood pulps. This is generally considered to be
due to the fact that hardwood pulps have higher hexenuronic acid (Hex A)
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content than softwood pulps. Some recommendations for a hot D stage include
the use of a hot acid stage (see above) before the hot D stage (i.e., ADHT, first
stage), optimization of the pH to improve performance, and the addition of
sulphamic acid or formaldehyde to the hot D stage to reduce organically bound
chlorine in the pulp. Although the hot D stage could be used to replace any D
stage (Do. D1, DA it generally gives the best results when used to replace the Do
stage.
One drawback with the hot first D stage is a slightly negative impact on the pulp
viscosity, strength and the energy required to reach high temperature. Hot CI02
bleaching has been shown to significantly lower the AOX discharges from
bleaching. Part of the AOX reduction comes from the fact that less C102 is
required to reach the same brightness level and part from the fact that the
elevated reaction temperature and extended reaction time in a hot D stage cause
the AOX to be degraded to chloride ions.
There are a few commercially operating systems in the world today. The major
issues with this technology are yield, corrosion, and scaling. It is difficult to
assess changes in yield in a laboratory environment, and much more difficult to
assess yield in a mill operation; however, some detailed evaluations show
significant yield loss by this acid hydrolysis which is not fully offset by reduced
yield loss in subsequent bleaching. The application of sulfuric acid at high
temperature creates a very corrosive environment, and some mills have reported
failures of austenitic stainless steel equipment and piping. Where this effluent is
recycled to the post-oxygen washing, care must be taken to prevent scale
buildup on equipment and piping.
Since there is no documented literature on the impact on effluent color from a hot
D stage we can only recommend a laboratory investigation at this time. This
process would likely increase energy demand due to heat requirements and
increase effluent thermal load. This technology may be of some interest to
BRPP, but it is known that the Canton mill has a limitation in steam supply that
would make it difficult to practice.
Ozone Bleachinq
Ozone bleaching has been installed worldwide in 28 mills. Those operating
commercially today are the ones that operate at medium (10-14%) consistency
and high (40%) consistency. Recently, it has been proposed that this
technology, especially for applications of low doses of ozone, and particularly
when used in combination with chlorine dioxide in a single stage, may be
practiced at low (2-4%) consistency. Market demands will justify ozone use in a
limited number of mills. However, it remains to be seen if further regulatory
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demands may require widespread implementation. There are numerous
published articles regarding the implementation and use of ozone and peroxide
in bleaching sequences.i57
The capital cost for an installation of this type is very high for a retrofit installation,
due to the requirement of providing high consistency pulp (40%). In all cases,
the implementation of ozone bleaching commercially was done during a major
fiberline rebuild, where the incremental cost of ozone was realistic.
It is well accepted that bleaching sequences using relatively high ozone charge
(0.8-1% 03 on pulp) results in a pulp with a relatively low viscosity, even though
the strength properties for fine papers is acceptable. Combining ozone and
chlorine compounds in a single stage (HZ, DCZ, CZ, ZC, DZ, ZD) was known
since 1967. Six mills have reported using a sequential ZD or DZ stage in these
sequences(19). The implementation of ozone in combination with chlorine dioxide
in the first stage of bleaching rose significantly for a few years in the late 1990s,
but there have since been almost no additional installations.
ZD technology was implemented at the Domtar mill in Espanola, Ontario in
combination with a major fiberine rebuild. A significant reduction in BOD, COD,
Color, and AOX was noted, but it is not clear to what extent the ozone stage was
responsible. Further, and as reported in the 2001 study, the installation at
Domtar is on a very difficult to bleach species which is quite unique in its oxidant
demand (very high). Therefore, it is difficult to extrapolate these results to other
hardwood bleach plants without further study.
The implementation of ozone bleaching at the Canton mill cannot be
recommended, as an effluent color reduction cannot be clearly projected from
other mill installations, nor could it be demonstrated in a laboratory study on
Canton mill pulp. The risk of not achieving a major reduction in color, while
investing high capital and operating cost is high with this technology.
Effect of Oxvaen and Peroxide Addition to Extraction Stage E, EP, Eo EoP
After a Chlorine dioxide Delignification treatment and washing step 40 to 65% of
the oxidized products are removed. The second stage of bleaching is an
extraction with caustic soda (dilute aqueous sodium hydroxide solution) at
temperature of 140-175OF to dissolve the rest of the oxidized and chlorinated
lignin (80 to 90%). This prevents the pulp from consuming bleaching chemicals
in the later stages.
The addition of oxidation chemicals (oxygen and/or peroxide) to the extraction
stage increases the effectiveness of extraction. Initially these additions were
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made to decrease the overall cost of the bleaching sequence but now, because
of environmental concerns, the extraction stages are being fortified with oxygen
and peroxide to minimize the amounts of chlorine dioxide used in the bleaching
process, and also to decrease AOX and color in the bleaching effluent.
Caustic Soda Charge
Hardwood pulps require a higher ratio (70% of the applied chlorine factor
charge then softwood Kraft pulp. When chlorine dioxide is fully substituted for
the chlorine, less acid is formed and less NaOH is required. For Kraft
hardwood the sodium hydroxide charge is reduced to 0.35 Ibs of NaOH per 1.0
1 b of available chlorine.
Peroxide Charge
The use of peroxide as an oxidant in the first extraction stage was first reported
in 1936. Adding small amounts of peroxide to the extraction stage, the pulp
darkening caused by the action of the hot alkali and was decreased. Some
brightness improvement was possible after the second chlorine dioxide stage
thus maximizing the efficiency of a conventional bleaching sequence.
Hydrogen peroxide was also found to lower the effluent color coming from the
extraction stage. The quantity of peroxide used in an Ep stage ranges from 4 to
8 lb peroxide per ton of pulp. Generally Ep produces brighter pulp than Eo but
the Kappa number (K#) is higher.
Oxygen Charge and Oxygen Pressure in an Eo Stage
The use of a small amount of oxygen in a conventional extraction stage
produces an extracted pulp with a lower Kappa No. (K#) and a higher
brightness. The charge of Oxygen ranges from 5 to 10 lb of oxygen per ton of
pulp.
A pressure of 20 psig with good mixing of the gas and stock, along with an
exposure of the pulp to the oxygen pressure for at least 3 minutes, is sufficient.
This can be accomplished by either having a pressurized tube long enough to
provide the retention time at pressure or by installing a black pressure value on
top of the tube to ensure the 20 psig MPa of oxygen pressure for the specified
time.
Since there seems to be little response to the addition of oxygen in the extraction
stage on hardwood pulp, we have evaluated the operating conditions in the
upflow tube of the Eo tower. When oxidative extraction was first invented and
introduced to the industry, the design guideline was to allow for 3 minutes
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ItGnl
retention time at 20 psig. According to the original development work, very little
additional benefit was achieved for longer time under pressure or higher
pressure. The Eo towers at the Canton mill use static pressure to achieve this
guideline (no backpressure control valve). The Eo tower has a total height of
96'10" to the elbow, and the bottom 14'6" is piping and the bottom cone on the
upflow tube. This means, at the entry to the straight wall section of the upflow
tube, the static pressure is about 36.7 psig. At an operating rate of 797
ADBT/day and 12% consistency, the pulp flow is 147 CFM in a tower of 4"9"
diameter (17.7 ft2 area), which results in a velocity in the tower of 8.3 fpm. This
means that at the minimum 20 psig pressure, the retention time would have been
about 5'/z minutes. This satisfies the design criteria, so there is no reason to
suspect tower design as a key issue in performance. Further, since the diameter
of the upflow tube is quite small, there is not a good reason to suspect tower
channeling as being responsible for reduced retention time. If there is any
reason to believe that there may be channeling, a tracer test should be run to
confirm the actual retention time.
We were unable to check the softwood side Eo tower, as we did not have all of
the tower dimensions; however, the same design criteria would have been
applied when built, and the effect of oxygen on the softwood side has been
confirmed.
EoP Extraction
Reinforcement of the first extraction stage with oxygen and hydrogen peroxide
adds several benefits to existing bleach plants. Lower Kappa number (K#),
brightness stability, brightness increase, and effluent color reduction are well
documented benefits. Indirect benefits from reinforcement include AOX
reduction, resulting from kappa factor optimization lower charges of chlorine
dioxide. The charge of oxygen is similar to the Eo stage with the peroxide charge
ranging from 4 to 6 lb peroxide per ton of pulp.
An important fact about the chlorine dioxide and extraction stage is that there is a
finite limit to reduction in the kappa number and only a certain quantity of lignin
can be removed before an asymptotic limit is reached. When oxidizing
chemicals are added to the extraction stage and the lower kappa number value
reached, then pulp brightness increases. Although pulp brightness for hardwood
after DEop treatment of 80-85 % have been achieved, the final brightness in ECF
bleaching were only improved by one to two points compared to Eo extracted
pulps.
Addition of oxygen and peroxide to extraction stage has been a proven
technology to improve brightness from the extraction stage and to lower the color
from the bleach plant. The following study shows the effect of addition of these
Pubic Version - Nov 2006 CONFIDENTIAL n'

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chemicals on hardwood pulps under different combinations to represent DE, DEP,
Do, and DEoP stages.
EFFECT OF Do, E, Eo, EoP, TREATMENT (HARDWOOD KRAFT- 02 PULP
KAPPA NO. 9.3 VISCOSITY, 24.6 mPa.s KAPPA FACTOR 0.23)
SEQUENCE CHEMICAL ISO
on pulp, % kappa no. lignin ,% Brightness, %
Do 0.8 C102 5.1 1.01
Dn E 1.2 NaOH 3.6 0.49 72.2
MFD 03H..M A n43 75A
Do Eo 0.5% 02 2.8 0.39 74.1
Do EoP 0.5% 02+0.3%H202 2.3 0.34 79.5
Note: Viscosities ranged from 19.6 to 21.8 mPa.s.
Effluent Loading
Sequence Kgtt COLOR
AOX BOD COD
Do 14
Do E 21 0.07 4.4 16.7
D. F. if) n CA 4 A 169
Do Eo 13 0.06 4.6 16.1
Do EoP 8 0.07 4.7 16.8
Similarly, the following study shows the effect of addition of oxygen and peroxide
on hardwood pulps under different combinations to represent DE, DEP,DEo, and
DEoP stages.
EFFECT OF D„ E, Eo, EoP, TREATMENT (SOFTWOOD KRAFT- 02 PULP KAPPA NO.
16.6, VISCOSITY, 23.4 mPa.s, KAPPA FACTOR 0.23)
SEQUENCE CHEMICAL ISO
on pulp, % kappa no. lignin ,% Brightness,
o�
Do 1.5 CI02 6.7 1.31
On E 1.1 NaOH 4.1 0.59 51.2
On En 0.4 1-1909 3.2 0.46 58.1
Do Eo 0.5 02 2.9 0.41 56.2
Do EoP 0.5% 02+0.4%H202 2.6 0.38 64.3
Note: Viscosities ranged from 21.6 to 23.0 mPa.s.
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Sequence Effluent loading
Kg1t COLOR AOX BOD COD
Do 17
D E 42 0.61 8.0 30
D. Eo—_ - 24 0.53 8 5 32
Do Eo 28 0.47 8.4 29
Do EoP 14 0.45 8.1 28
Hot Peroxide Stage
The use of hydrogen peroxide continues to steadily increase in ECF bleaching.
This technology was first implemented to overcome the decrease in effectiveness
of Dioo versus chlorination stages. It has since been demonstrated in most mills
that a small quantity of hydrogen peroxide (0.2-0.3% on pulp) is very effective in
reducing the total active chlorine demand in replacement ratios such that lower
bleaching cost is achieved. There are, however, some mills in which this practice
has not been successful. The benefit in the use of hydrogen peroxide in the Eo
stage is to achieve a reduction in the kappa factor in the first stage, and not
necessarily in the final bleaching stage. Generally, the technology is not as
attractive for mills that tend to use a very high kappa factor, or those who attempt
to reduce the final chlorine dioxide stage charge.
More recently, the advent of hot pressurized peroxide stages(311-13,21-30) has been
demonstrated to be capable of consuming significant quantities of peroxide (up to
2-3% on pulp) and to significantly reduce the total active chlorine demand. Most
of these stages have been installed primarily to operate in fiberlines where totally
chlorine free (TCF) pulp is produced either continuously, or in campaigns.
Generally, the use of high quantities of hydrogen peroxide in the first alkaline
extraction stage does not reduce bleach chemical cost. However, the relative
cost of chlorine dioxide and hydrogen peroxide has been changing such that the
operating cost penalty is reduced or eliminated at some mills. This economic
situation is geographically dependant, as well as dependant on the stage of
purchase contracts for hydrogen peroxide and chlorate.
This technology uses high temperature and extended retention time to effectively
consume the peroxide in the stage. The temperature of this stage is generally in
the range of 90-110°C (195-230°F), with retention time from 1-3 hours. There
are two technologies proposed for practice of this technology:
1. The use of a pressurized 60-180 minute reactor vessel, very similar to an
oxygen reactor is used in place of the Eo stage. This is commonly
referred to as a (PO) stage.
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2. The use of a short, high temperature upflow tube, in combination with an
existing atmospheric downflow tower for added retention. The
combination of a 10-20 minute high temperature upflow tube, followed by
30-120 minutes of atmospheric retention has been shown in laboratory
studies to achieve results similar to those achieve with high temperature
pressurized retention throughout the entire reaction time. This is
commonly referred to as a PHT stage.
In both cases, alkali, hydrogen peroxide, and a viscosity protector are added
ahead of a steam mixer and a chemical mixer. Steam is added to achieve
reaction temperature, and oxygen gas may or may not be required to achieve
best results, depending on the position of the stage in the fiberline. A simplified
schematic of the PHT design is shown on the next page. (The (PO) stage design
is the same as a single oxygen delignification system, but without added
washers.)
The use of chelants for proper management of trace metals is important to
improve effectiveness and selectivity of peroxide, oxygen and ozone stages in
both ECF and TCF bleaching. In both cases of hot peroxide bleaching stage
design, the use of chelants for proper management of trace metals and/or the
use of magnesium salts for preservation of viscosity must be considered.
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a:
CD
General Schematic of the Eop and PHT Stage
o'
z
0
N
O
O
O
Upflow Section:
Pressurized: 4 bar
Temperature: 90 - 130°C
Downflow Section:
Atmospheric Condition
Temperature: 95 - 980C
Pump
Mixer
CONFIDENTIAL

VGBI
TCF Bleaching
In the early 90s, there was a strong trend towards the implementation of non-
chlorine, or totally chlorine free (TCF) bleaching, particularly for those mills
furnishing pulp and paper into the Germanic speaking countries of Europe. The
first implementation of TCF bleaching was in sulfite mills in Europe. Sulfite pulps
have inherently higher bleachability compared to Kraft pulps, and most mills were
able to achieve this goal using only oxygen and peroxide. The growth rate for
ECF and TCF pulps is shown in the figure above. In the early 1990s, the
production of TCF pulp followed the growth curve shown in the figure below, and
in the subsequent 5 years, the growth rate of TCF pulps slowed, while the growth
rate of ECF pulps has increased.
60
Other
m
40
0
0 0
c CF -5 mt/y
° 20
Z>
TCF
0 a-1 mt/y
1988 1990 1992 1994 1996
Year
The development of quality TCF pulps from the Kraft was proven to be more
problematic, especially when targeting the same brightness and pulp quality
targets of conventional Kraft ECF pulps. There continue to be number of mills,
especially in Scandinavia that produce TCF pulps from hardwood and softwood
on a continuous basis. However, some mills have displaced some production to
be "ECF-Light" pulps, where only a very small amount of chlorine dioxide is used,
but higher brightness and quality can be achieved compared to TCF pulps.
Although technically, TCF pulp can be produced at the Canton mill, there is no
published commercial experience with this technology in the world to produce the
paper and paperboard grades manufactured at Canton. Further study of this
technology at the Canton mill is not recommended.
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In a 2006 article in Pulp and Paper Canada (Ref 107:4(2006)), Paul Earl
summed up the current status of TCF bleaching: "It is an ECF world, whether
you look in North America, Europe, South America, and now Japan is catching
up, too. Only in Scandinavia can you find a few TCF producers, all tightly linked
to TCF customers. And even there, I don't see much likelihood of more bleach
plant conversions, or that the TCF market will grow. There's nothing on the
horizon that suggests a significant change away from ECF". If there is no
significant future demand for TCF pulp, there will be little development taking
place globally to resolve the operating issues and pulp quality issues with
producing high quality Kraft pulp with TCF sequence. This makes consideration
of TCF bleaching at Canton a very risky proposition, with a very high operating
cost.
BFR® Process for Hardwood Line
The BFR® Process has been demonstrated to significantly improve the effluent
quality on the softwood line at the Canton mill due to reuse of bleach effluent for
oxygen washing. This process can be incorporated on the hardwood line, and
the results can be expected to be similar. However, this approach is similar to
pursuing external treatment options, as there will be a high capital cost required
for implementation, and the operating cost of the mill will increase. Further study
of this technology at the Canton mill is not recommended.
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Emerging Pulping and Bleaching Technologies
There are a number of other developing technologies that may be considered in
the future for implementation at the Canton mill. These technologies are not
included in the evaluated options, as we believe that there has not been sufficient
commercial experience to implement at this time and assure performance in
color reduction or financial benefit will be achieved.
LIGNOX
The LIGNOX process is one of several processes that use chelating agents,
oxygen delignification and hydrogen peroxide treatments. These types of
processes, as well as (PO) and PHT stages, are becoming more widely used as
efforts to reduce chlorine-containing compounds are increased.
Enzymes
The potential for use of enzymes has been decreased as other technologies
such as extended delignification and oxygen delignification are implemented.
However, some mills have implemented this technology on a full time basis (10-
20 mills globally). Most mills that have implemented this technology did so due
to limitations in the application of chlorine dioxide in the bleach plant. There are
some mills, however, that have found a slight reduction in operating cost,
particularly on hardwood pulps. The success of enzymes in a particular mill is
very dependent on the wood species processed. This technology could be
incorporated by adding enzymes and controlling pH in the brown stock high
density storage tower. However, the viability will also depend on the cleanliness
of the pulp, the actual temperature of the pulp, and the temperature variations
encountered in normal operation at the high density storage tower.
Molybdate Activated Peroxide Delignification and NetFloce Recovery
Process
Addition of acidic peroxide activated by catalytic amounts of a molybdate (31) (mP) is
an alternate delignification method that can be used on hardwood pulps after
oxygen delignification. The reaction may be carried out in the brown stock storage
tower (if metallurgy is acceptable) with no large capital investment required. If the
effluent is either used for back washing or sent to the secondary treatment as an
acid stream, only the equipment for charging the chemicals, sulphuric acid,
hydrogen peroxide and molybdate is needed. The reaction is done at 10%-12%
consistency for 2-4 hours at 70-90°C, and pH 4-5. Besides decreasing the kappa
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VGBI
number 4 to 5 units of the Kraft hardwood pulp the mP treatment removes
hexenuronic acids and bound COD thus reducing the formation of oxalate in the
following stages. Mill scale results have shown a usage of 2.6 lbs. hydrogen
peroxide per unit kappa number drop. Molybdate usage is 0.8 lbs. but may be
recovered with some new schemes now being tested.
Accompanying the decrease in Kappa number of 4-5 units the kappa factor would
also decrease to 0.20 from the initial value of 0.30. Thus, for oxygen delignified
pulp with kappa number 5, the chlorine dioxide charge in the D, stage would be 7.6
lbs CI02/ton of pulp. This means the AOX would be further reduced while color
may be decreased by 5,700 lbs/ton.
The Kemira Company, which provides chemicals for the mP technique also,
endorses the NetFloc( 2) process (the use of polyethylene oxide as a flocculant) to
remove extractives, non-process elements, and color from process effluent.
Recovery of the molybdate and color from this stage as well as from the EoP stage
is being tested at a mill site.
This technology is in the early phases of commercial demonstration in Finland. It is
expected that this technology will be quite sensitive to black liquor carryover, so
further study should be made before considering this technology.
Peracids
Distilled peracids have proven to be viable for use in chlorine and chlorine-free
bleaching sequences. The pulp quality parameters are generally as good as or
better than for ozone, but the low capital costs are attractive particularly as mills
assess the viability of ozone. Peracids have been evaluated in both pilot plant
stage and are now used in four mills in Finland. This is potentially a promising
new area of pulp bleaching research and it is possible that peracids will become
an additive or alternative to C102, ozone or peroxide when used in conjunction
with ECF and TCF sequences. At present, however, the use of peracids
generally results in an increase in operating cost, so their use today is primarily in
mills that are producing TCF pulps. There is no commercial production of
peracids in North America.
Aldehyde-Enhanced Bleaching (AEB)
The efficiency of chlorine dioxide bleaching falls short of the theoretical oxidizing
power of chlorine dioxide. In practice, much of the chlorine dioxide is wasted
through conversion to chlorite and chlorate in a complex series of reaction
pathways. Aldehyde-Enhanced Bleaching process improves the efficiency of
chlorine dioxide bleaching stage by adding an aldehyde compound to the
chlorine dioxide bleaching stage. This generates reactions, which promote the
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regeneration of chlorine dioxide from chlorite. Formaldehyde is the cheapest and
simplest of the aldehydes, and has proven in successful mill trials as an additive
in the Do stage. Bleaching costs have decreased by as much as 20%.
Mill trials tested the feasibility of the AEB process, with the following
conclusions:
• The chemistry works in mill scale
• Capital cost is minimal
• The process is safe with no exposure concerns
• No harm to either the treatment system or the environment
• Pulp can be sold for any use without concern of formaldehyde residual in
pulp
• Low cost opportunity to save chlorine dioxide. A saving of 1.1% chlorine
dioxide / MTAD pulp was obtained. The savings for this mill represented
$2 million per year after taking into account the cost of the formaldehyde
•A 22% decrease in effluent color of the Do stage was measured
TABLE I *. Comparison of properties of filtrates from the overflow of the Do seal
tank.
Average of four samples Average of four samples
taken on taken on
Sept. 17, two days before Sept. 19, Day I of the trial
he trial
BOD, mg/L 1182 1142
standard deviation: 65 standard deviation: 60
COD, mg/L 2313 1958
standard deviation: 40 standard deviation: 45
Color,C.U. 1516 1174
tandard deviation: 90 Istandard deviation: 80
First Mill trial of Aldehyde — Enhanced Bleaching preprints of the 2005 IPBC,
Stockholm JUNE 14-16, 2005
The straightforward implementation of this technology without the requirement of
major capital expenditures makes it an attractive option for some mills to benefit
from lower chlorine dioxide application.
Hot Chlorine Dioxide Stage
Recently, laboratory work has shown the benefits of increased temperature in
combination with extended retention time in the first chlorine dioxide stage.
Chlorine dioxide savings of 10-20% have been reported when operating the
stage at 70-800C (160-175°F) for 1-2 hours retention time. This technology may
be of some interest to BRPP, but it is known that the Canton mill has a limitation
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in steam supply that would make it difficult to practice and would likely increase
effluent thermal loading.
Pulp Washing and Effluent Flow Reduction
The only reason there is any process effluent from a bleach plant is that we wash
the pulp after each bleaching stage and there is the need to purge dissolved
solids from the system, which, if retained, would inhibit production, consume
chemicals, or adversely affect product properties. If these contaminants could be
completely removed through internal systems such as BFR®, there would be no
need for process effluent; the mill water effluent system would be substantially
decreased. However, to date, no technology, including the BFR® process has
been demonstrated to eliminate liquid effluent from Kraft pulp bleach plants.
Notwithstanding some of the findings from previous work (33-311 washing in the
modern bleach plant is important in that more costly bleaching chemicals are
being used, especially in TCF bleaching. In addition, hydrogen peroxide,
peracids, and ozone are very sensitive to transition metals. Finally, efficient
washing must be used if the industry is to achieve the "low effluent flow bleach
plant".
Over the last two decades, the pulp and paper industry has made significant
gains in its efforts to use recycled effluent to reduce fresh water usage and
minimize effluent discharges.
The effluent quantity from bleached Kraft pulp mills has also been reduced, while
the effluent quality, as measured by toxicity, BOD, COD, color, odor and foam,
has been improved. This is especially true if bleach plant closure is made part of
the comparison where it has been shown that the old filter bleach plant, which
used to emit 12,000 gal/ton, is modernized to a filter ECF bleach plant, the
volume would decrease to 2,880 gal/ton. For the same degree of filtrate closure
it has been shown that a corresponding press-based bleach plant would only
emit 1,920 gal/ton(36)
The Canton mill is one of the most modern mills in the world relative to water
reuse, minimization of effluent flow, and minimization of environmental impact
from the bleach plant effluent. There are a number of principles of pulp washing
and water reuse that are pertinent to any modern mill; most if not all of these
have been addressed or are practiced at the Canton mill. A review of these
principles may be of value in planning future potential changes to the mill
operation.
Conventional washing techniques include (a) direct counter-current, (b) split flow
and (c)jump-stage counter-current which were all tried to effect lower fresh water
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use. "The key to filtrate recycling is remembering that 'like goes with like'. For
example, if pulp is going into a D100 stage, D,00 filtrate can be used for dilution,
similarly for the other stages. If the washer showers allow for two different
filtrates to be used for washing, the top or last shower can use filtrate from a
following stage. To avoid mixing acid and alkaline filtrates, it is important to not
break through the pulp sheet with the filtrate from the subsequent stage.
Breakthrough will not occur if the last shower flow is more than half the total
shower flow, where the total shower flow is about a dilution factor of 2. The
philosophy of using two different filtrate flows for showers is employed with the
split-flow counter-current washing system. Direct countercurrent recycling is
generally not recommended as it may increase chemical consumption and may
cause pitch and foaming problems."(3
The following is a list of some opportunities for water reduction that can typically
be found in pulp mills today(38).
a. For all washing stages, improving the discharge consistency of the washer
will improve pulp washing. Discharge consistency drops on older and
overloaded washers. The most common operating problems on vacuum
drum washers are low operating vacuum, improper application of wash water,
high washer speed, low discharge consistency, inadequately or unevenly
washed pulp and difficult pulp discharge. These issues are being
addressed at the Canton mill, and some recommendations are included
in this report.
b. Improving the wash shower type to get better shower distribution and more
efficient washing. There already exists a plan to continue to replace the
washing showers stepwise on the vacuum washers in the Canton mill,
with two washers already converted to modern shower designs.
c. Replacing older washer drums with new drums having anti-rewet decking will
result in several points increase in discharge consistency and offer the
potential for reducing wash water requirements. All of the vacuum washer
drums at the Canton mill, except for the hardwood brown stock
washers, have already been replaced with modern Coru-Dek washer
drums.
d. Use of filtrates on wire cleaning showers and operating the cleaning showers
intermittently can reduce water consumption.
e. Use recycled filtrates for repulper dilution and any standpipe dilution (often a
16% washer discharge is diluted to 12% with repulper dilution). Generally
pump standpipe dilution can operate on the filtrate from the following washing
stage, although this is often connected to hot or warm water for ease of start-
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up. Non-compatible construction materials may be an issue. This is already
practiced at the Canton mill.
f. Water doctors can often be replaced with air doctors or operated using
washing filtrate for that stage. Sometimes this will require installation of fiber
filters. This is already practiced at the Canton mill.
g. It may be possible to recycle excess white water from the pulp or paper
machine or bleach screening system to showers where hot or fresh water is
being used. This is already practiced at the Canton mill.
h. The bleached pulp screen room can be closed. This is already practiced at
the Canton mill.
i. Typically, washer showers are set at a constant flow but flow control can be
installed to enable wash ratio or dilution factor control. This is already
practiced at the Canton mill.
j. Washer seal tanks should be put on level control to avoid spillage for
effective level control. However, seal tanks are often too small to make this
practical in older mills. This is already practiced at the Canton mill.
k. Converting the D/C or D100 stage from low to medium consistency can
improve the water economy. This is already in place at Canton.
I. A great deal of attention has already been spent at the Canton mill on spill
recovery not only for fiber, but filtrates as well. There is little else that can
be done at Canton for spill recovery.
The Key Elements in Achieving Water Reduction in a Mill are:
• Decrease effluent volume (this will permit economic treatment of the effluent)
• Decrease process water (in washing and raising consistency of bleaching
stages) This is already practiced at the Canton mill.
• Reuse evaporator condensate
• Reuse machine white water
• Recover and reuse heat from process
• Standardize temperature.
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Based on the site survey undertaken by the authors of this report, most of the
principles of water reduction have been addressed and are being practiced at the
Canton mill. One observation made on site is that the water use on the washers
seems to be at a flow that is borderline low to achieve best economic operation
of the fiberline. Specific recommendations on some current problem areas have
been made in the "Site Audit and Performance Review" section of this report. An
increase in water use should be studied as a means to reduce bleach chemical
consumption and thus reduce operating cost.
The "Bleach Filtrate Recycle" process (BFR®) which was developed at, and is
currently practiced at the Canton mill is a benchmark for low effluent flow in the
world(39 .
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External Treatment Options
Jacobs Study and NCASI Study Commentary
In 2001 Blue Ridge has engaged the Jacobs Engineering Group Inc. to evaluate
and report on end-of-pipe color technology. A comprehensive report (") on eight
different color technologies clearly delineated to what extent color removal could
be expected and the economics associated with a particular technology was sent
to the mill in early spring of 2001. In 2006 to bring the information up to date the
Blue Ridge along with several other pulp and paper companies engaged NCASI,
to review the color control technologies and their application to modern Kraft mill
wastewater. A Technical Report 'Review of Color Control Technologies" has
been issued. Some of the technologies discussed in both reports are the same.
The technologies reviewed were:
Alum Color Removal System
Lime Color Removal System
Polyamine Color Removal System
Ultrafiltration System
Carbon Adsorption System
Storage and Time Release System
Ozonation System
Crystallization System
The basis of the analysis of these systems was the mill data on:
Average flow 24.8 MG/Day
Peak flow 28.7 MG/Day
Average color 41,188 Ibs/day
Maximum color 65,888 Ibs/day
The Following are technologies reviewed in the NCASI Report (where there is a
phrase - [BRPP experiments] shown, then the mill has undertaken either a
laboratory or mill trial to evaluate the technology).
EXTERNAL TREATMENT (notes included where BRPP has evaluated)
Membrane Technologies
Microfiltration (BRPP experiments)
Ultrafiltration
Nanofiltration
Reverse Osmosis
Membrane bioreactors
Ion Exchange
Activated petroleum coke
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Powered activated carbon
Electrodialysis and Electrodialysis Reversal
Precipitation Processes
Lime (BRPP experiments)
Alum
Iron
Polymer (BRPP experiments)
Nitric acid
Electrochemical Treatment
Oxidation Processes
Peroxide
Enhanced Peroxide with catalysts-TAML (BRPP experiments)
Cost prohibitive and commercial availability (BRPP
experiments)
Ozone with Biological Filtration
Evaporation and Incineration
Fungus/Bacteria/Enzymes
White rot fungi (MyCoPor) - (BRPP experiments)
The basis of the analysis of these systems was the mill data on:
2005 Wastewater Treatment Performance, Blue Ridge Paper Products Canton
Mill, Canton Mill 2005 Wastewater Effluent Performance - all Secondary
Effluent (SE)
NPDES -7�--—Normalized to 1
Parameter 2005 average Permit Limits Pulp Production
25.65 mgd 29 9 mgd
Flow (0.65 mgd from Town of Canton) monthly avg 18,547 gal/ADTBP
BOD5 7.5 mg/I 3205 Ibs/day 1.16 Ibs /ADTBP
1610 Ibs/day monthly avg
COD 162.6 m g/I NA - monitor 25.1 Ibs/ADTBP
34,775 Ibs/day and re sort
TSS 16.8 mg/I 12,549 Ibs/day 2.61 Ibs/ADTBP
_ 3606 Ibs/day monthly avg
SE Color 183 ppm 42,000 Ibs/day 28.3 Ibs/ADTBP
39 128 Ibs/day annual average
0.91 mg/1 1557lbs/day
AOX 194 Ibs/day monthly avg 0.14 Ibs/ADTBP
A summary of the results of the Jacobs Report appeared in the Bleach
Environmental Process Evaluation Report June 8, 2001. It is not the intention of
the authors of this report to further describe each of the eight technological
systems mentioned in the Jacobs Engineering report. We agree with comments
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VG01
that the end of pipe color treatments is not economically feasible because they
require high capital investment and ongoing operations expenses.
We will however, comment on the external treatment options feasibility fully
discussed in the NCASI Technical Bulletin and note whether or not Blue Ridge
has evaluated the technology.
However, some thoughts and concerns are stated in the next several pages
particularly relative to treatment of individual bleach effluent streams using similar
technology. All of these technologies have the same disadvantage as the "End-
of-Pipe" options in that they incur capital to install and result in increased
operations and maintenance costs for the mill. Thus they are not favored in light
of alternative in plant process changes.
COLOR REMOVAL - SEPARATION PROCESSES
Membrane Technologies
The following sections describe various membrane technologies, which could be
used for treating colored wastewaters. Depending on the pore size the
membrane processes are divided into microfiltration (MF), ultrafiltration (UF),
nanofitration (NF) and reverse osmosis (RO). The pore size or cut-off value of
the membranes in these processes decreases in named order. A membrane with
a higher cut-off value has a higher filtration capacity but generally lower removal
efficiency.
Because of the high membrane cost and their limited flux capacity, the
economical feasibility of the process is directly proportional to the volumetric flow.
Therefore, of the Kraft mill effluents, the Eop filtrate with a low volume and high
concentration is typically considered most feasible to treat with membrane
separation. Treatment of total mill effluent would be extremely costly.
Microfiltration (MF)
Microfiltration has the largest pore size of any of the membrane technologies
discussed above, approximately 0.03 to 10 microns and a molecular weight cut-
off of greater than 100,000 daltons. The typical operating pressures for MF
systems are 10 to 100 psi. Microfiltration membranes usually come in two flow
types: cross-flow and dead-end flow. With cross-flow membranes the fluid runs
parallel to the membrane and passes through the membrane based on the
pressure differential. In dead-end flow the fluid flows perpendicular to the
membrane. Because of its large pore size, MF is often used as a pre-treatment
step for reverse osmosis and nanofiltration. To prevent fouling, frequent
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backwashing aids in keeping the membrane clean and helps maintain membrane
flux. Microfiltration can also be used with biological treatment in membrane
bioreactors. Most mill scale implementations of microfiltration are for the recovery
and reuse of internal water streams (coating kitchen effluent) or as pre-treatment
stages for other membrane processes.
Ultrafiltration (UF)
Membrane filtration is a separation method that separates dissolved molecules
based on their size and charge. High molecular weight substances such as
lignin compounds, which are the primary sources of color and COD in effluents,
can be concentrated in a smaller stream for separate treatment or destruction.
The permeate, which contains low molecular weight components (mainly water),
is sewered or may be reused in the mill to some extent.
Ultrafiltration (UF) is a pressure-driven process where colloids, particulates and
high molecular mass soluble compounds are retained by size exclusion. OF has
a pore size of approximately 0.005 to 0.1 microns and a molecular weight cut off
of 10,000 to 100,000 daltons. The typical operating pressures for OF systems are
5 to 150 psi. The OF membranes are generally manufactured in either flat-sheet
or tubular form. The main system components include the membrane units,
pumps, and cleaning system.
Ultrafiltration is considered proven technology but it has not gained acceptance in
the pulp industry. The OF or RO treatment processes would require extensive
pre-treatment processes for solids removal, which would most likely include
coagulation and filtration. This would increase the equipment cost and land
required for these treatment processes. There are no known installations of Kraft
mills using OF to treat the whole mill effluent or bleach plant, although OF is used
in paper mills to treat the white water in the paper mill circulation system and
coating kitchen effluent.
There are several risks related to membrane applications. The modularity of the
membrane installation makes it more reliable than a single unit. Membrane
fouling and abrasion gradually diminish the flux causing the membrane to be
replaced after some time. Typically, membrane lifetime has been around 18
months. Short membrane lifetimes or unpredictable fouling tendencies make a
membrane unreliable.
Impact of pH
It is well known that membrane filtration of acidic bleach plant filtrates results in
severe fouling problems destroying the capacity of the membrane (Sierka, 1996;
STFI, 2002). This is explained by the fact that organic acids (e.g. fatty acids) are
protonized in acidic filtrates and strongly adsorbed onto the membrane.
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Therefore ultrafiltration of the acidic bleach plant effluents would not be
practical.
The most viable application of a membrane process is to treat the EoP filtrate by
using a OF type membrane. However, the membrane pore size must be
established in lab and pilot tests. The figure below shows a possible
configuration for OF treating bleach plant effluent.
i —7 —�
� ,
To OF OF Tc
Brownstock Concentrate permeate Waste
Fiberline Treatment
Ultrafiltration of alkaline filtrates from an ECF bleach plant(Herstad, 1998)
Treatment of bleach plant EoP filtrate by full-scale ultrafiltration processes has
been applied in at least two Japanese mills and one Swedish Kraft mill for a
number of years. To our knowledge, all three of these ultrafiltration installations
have been discontinued after several years of operation.
Although ultrafiltration is considered proven technology it has not gained
acceptance in the pulp industry.
Nanofiltration (NF)
NF has a pore size of approximately 0.001 microns and a molecular weight cut-
off of 1,000 to 10,000 daltons. No full-scale NF plants are known to operate in
Kraft mills.
Nanofiltration has a lower permeate flux than ultrafiltration, which results in
cleaner product, but NF is more sensitive to fouling and must be preceded by a
pre-treatment step. The pre-treatment step is often ultrafiltration or a biological
process.
Like the other membrane technologies, NF could be used to treat the whole mill
effluent. However, to treat the whole mill effluent a pre-treatment step would be
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VIGIN
required to remove suspended solids to prevent membrane fouling. Also, using
NF would create a highly concentrated stream that would need to be disposed of.
There are no known installations of Kraft mills using NF to treat the whole
mill effluent.
Reverse Osmosis (RO)
Reverse osmosis is similar to ultrafiltration in that the effluent is treated by
passing it through a membrane that rejects molecules that are larger than the
pore size. The difference is that in reverse osmosis the pore size is much
smaller, with the result that high-pressures (10 - 100 Bar) must be used to force
the effluent through the membrane.
Reverse osmosis is used, for example, in desalinization of seawater and has the
potential to remove almost all impurities and produce clean water for reuse.
To treat the whole mill effluent a pre-treatment step would be required to remove
suspended solids to prevent membrane fouling. There are no known
installations of Kraft mills using RO to treat the whole mill effluent or
colored bleach plant effluents. RO has been used in sulfite mills for water
reuse and spent liquor treatment.
In 1998 the Irving pulp and paper mill in Saint John, New Brunswick, Canada
started up an RO system for the treatment of condensates from the 5th
evaporation effect (Dube, 1999). The mill is a bleached Kraft mill that produces
about 900 tons/day of market pulp. The mill did not have secondary treatment
and instead uses in-process measures to meet its environmental requirements.
The RO treatment of the condensate from the 5th evaporator effect was
implemented to reduce the effluent toxicity, which was not removed by
condensate stripping. The RO treatment removes about 89% of the COD from
the stream and about 88% of the BOD. No data was given for color removal. The
clean permeate is returned and used as wash water on the No. 2 post oxygen
delignification washer and the concentrate (about 1% of the flow) is either burnt
in the bark boiler or sent to the high solids crystallizer and eventually burnt in the
recovery boiler.
Membrane Bioreactors
The membrane bioreactor (MBR) is a hybrid biological treatment system that
combines the biological activity of a free-floating reactor, such as an AST, with
the advantage of membrane separation to achieve reductions in suspended
solids, COD, BOD, and toxicity. In this process, membranes are placed in an
aerated biological reactor. Effluent is fed to the reactor, where it is biologically
degraded. The effluent passes through the membrane and this permeate is
discharged. The accumulated sludge is then withdrawn for disposal. The
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advantages of a membrane bioreactor include higher loading, smaller size,
insensitivity to sludge settling characteristics, and effective removal of solids,
COD, and toxicity. In addition, the sludge retention time (SRT) and the hydraulic
retention time (HRT) can be varied independently. Disadvantages include
membrane life span, restricted flux rates and initial investment cost.
This process is used in a variety of industrial applications, but there is no
full-scale implementation treating Kraft mill effluent.
Ion Exchange
Ion exchange resins, such as weak basic resins based on a phenol formaldehyde
matrix, have been found suitable for treatment of pulp and paper mill effluent.
The ion exchange treatment processes include the following steps:
• pH adjustment and pre-treatment (pH requirement varies with the resin;
usually it is on the acid side towards pH 2 - 4, but may be up to pH 9)
Effluent treatment step passing the effluent through the column until
breakthrough capacity is reached. When the resin is saturated the column
needs to be eluted
• Elution stage, where the pollutants are removed usually with caustic in a
concentrated form
• Activation stage where sulphuric acid is passed through the resin to
reactivate it.
In the Kraft industry the ion exchange process research has concentrated on
treatment of bleach plant effluent for removal of color and chlorinated organic
compounds. One example is "The Uddeholm Non-Polluting Bleach Plant"
developed in Sweden in 1975 - 1980 (Billerud AB, Skoghall mill). However, the
process is currently not in use at the Skoghall mill (Fitch, 1981).
Their processes have been tested in pilot scale but no full-scale installations are
known.
The risks with the ion exchange process are:
• Resin life time and plugging problems
• Disposal of elutate and associated chloride problems.
Treatment Efficiencies
The EPA tested the Billerud Non-Polluting Bleach plant in pilot scale in 1980
(Fitch, 1981). About twenty-five different organic components and thirteen heavy
metals were measured, as were the typical parameters (COD, color, pH and
chloride) showed significant reductions.
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Though promising this technology has not developed further for pulping
effluent since the 1980's and does not appear to be an active area of
investigation.
Activated Carbon and Activated Petroleum Coke Adsorption
Activated carbon has been used for removing organics from wastewater for many
years. The effectiveness of activated carbon in removing dissolved and colloidal
material by adsorption is primarily due to its extremely high surface area. Pore
size distribution and surface chemistry also determine the overall effectiveness.
Activated carbon treatment in the pulp and paper industry has primarily been
proposed for color reduction. High molecular weight organic compounds are
typically amenable to carbon adsorption, whereas colloidal compounds or
strongly polar organic compounds (amino acids, hydroxyl acids, sulphates and
sugars) are refractory to carbon treatment. Powdered activated carbon has a
higher surface area than granular carbon, which may improve color removal.
The PACTT", or powdered activated carbon treatment process, has been
developed by USFilter's Zimpro division, which owns the trademark. According to
the PACT trademark, the process consists of "wastewater treatment systems
comprising aeration contact tanks, aerobic digesters, air diffusers, clarifiers,
clarifier drive mechanisms, scum collectors, waste sludge airlift pumps, scum
removal airlift pumps, flow measuring weirs, aeration blowers, recycle pumps,
froth control pumps, polymer feed systems, carbon eductors and/or motor control
centers sold as a unit". The PACT process is also used at DuPont's Secure
Environmental Treatment (SET) commercial and industrial wastewater treatment
facility located at its Chambers Works site in Deepwater, New Jersey. One
potential problem with the PACT process was pointed out in a recent study
(Kennedy, 2000), which determined that PACT-treated wastewaters were
toxic to Ceriodaphnia dubia. The study concluded the toxicity was a result
of ingested PAC. Tertiary filtration was recommended). Further study of this
technology at the Canton mill is not recommended.
Recent studies have focused on less expensive alternatives to activated carbon.
One investigation used delayed petroleum coke, which is a waste by-product
from the oil sand industry (Shawwa, 2001; see below).
Color Removal from Bleach Plant Effluent using Activated Petroleum Coke
(Shawwa, 2001)
One laboratory study addressed the removal of color from bleaching effluent
using activated carbon obtained from delayed petroleum coke. The study found
that there was an abundant and cheap supply of delayed petroleum coke
available in western Canada. The petroleum coke was ground into powdered
form and activated in a two-stage process. The carbonization stage was carried
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VGBI
out at 8500C followed by a steam activation stage that lasted 1-6 hours. The
activated petroleum coke was tested using bleach plant effluent. The activated
petroleum coke was shown to be effective in removing color and AOX.
Applications of 2,500 mg/1 of powdered activated petroleum coke resulted in
about a 30% reduction in color and AOX. Applications of 15,000 mg/I of
powdered activated petroleum coke resulted in about a 90% reduction in color
and AOX.
Activated carbon produced using a 4-hour activation period provided the
maximum color reduction. Dosages of up to 2500 mg/1 produced a maximum
color removal of 33%. Higher color removal required higher activated carbon
dosages. The use of activated petroleum coke appeared to remove the
recalcitrant portion of the organic matter in the bleach plant effluent. This would
make the remaining effluent more susceptible to biological treatment.
Sludge handling was not addressed in this study. Further study of this technology
at the Canton mill is not recommended.
Electrodialysis (ED) and Electrodialysis Reversal (EDR)
In the electrodialysis (ED) method the electrolytes in a water solution are
separated with the aid of an electrical current and a membrane. The achievable
separation result depends first on the magnitude of applied electrical current and
the available size of membrane and secondly on the ion strength of the solution.
An electrodialysis system consists mainly of the electrodialytic membrane stack,
pumps, and membrane cleaning system.
Electrodialysis has been proposed as a method of closing up the bleach plant.
One study looked at the laboratory treatment of bleach plant acid stage effluent
using ED to remove non-process elements and then return the treated filtrates to
brownstock washing (Tsai, 1999). Electrodialysis could also be combined with
other membrane processes such as the treatment of nanofiltration permeate by
ED and then reuse in the mill (De Pinho, 1996). Electrodialysis is a
commercial technology used for desalination of water and the treatment of
various types of industrial effluent, but there are no known applications in
Kraft mills.
The electrodialysis reversal (EDR) process operates on the same basic principle
as ED, where an electrical current supplies the driving force to transfer
electrolytes through an ion-change membrane. However, the EDR process
includes polarity reversal that provides self-cleaning of the membrane surfaces
as part of the process. The EDR process can be used to remove COD and
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color. EDR has been used commercially, however there are no known
applications in the pulp and paper industry. Further study of this technology
at the Canton mill is not recommended.
COLOR REMOVAL - CHEMICAL PROCESSES
Chemical coagulation and solids separation of biologically treated effluent is a
method to reduce dissolved residual components such as color, COD, AOX and
nutrients. By adding organic coagulants or Me3+ (Fe, AI) salts, larger dissolved
organic molecules can be precipitated out of the solution. Floc-forming and ability
to settle are often enhanced by adding a separate organic polymer prior to solids
separation. The treatment involves the addition of a coagulant and a polymer, pH
control (if metal salts are used), separation of the formed solids in a dissolved air
flotation unit or in a conventional clarifier, and sludge disposal.
The addition of chemicals to the effluent treatment, especially in larger quantities,
has to be evaluated from all aspects, including the toxicity of the specific
chemical used in order to avoid potential effluent toxicity issues.
Lime Precipitation
Precipitation with lime has been used to reduce effluent color. Lime treatment
has been effective in industry trials for color removal (Ganjidoust, 1996; Roux,
2000). Other parameters would be reduced as well, including COD (60-70%), P,
and organic solids. Lime treatment typically requires higher dosage than alum
treatment and generates more sludge. A considerable amount of research was
devoted to the development of lime treatment processes in the late 1960's and
1970's. Basically there were "minimum lime" and "massive lime" processes. A
few installations were built in the USA (Baird, 1995). Essentially the processes
were similar to the raw water lime treatment. Reburnt lime was used as the
precipitating agent. In the massive lime process the precipitated sludge
containing lignin, other organic material and the used lime was regenerated in a
dedicated lime kiln, or it was combined with the mill's lime sludge. In other
processes separate sludge handling was attempted. The large dosages of lime
that were needed to achieve an acceptable treatment efficiency resulted in very
large quantities of sludge. The difficulties involved in the sludge dewatering
eventually led to the discontinuation of the efforts to develop lime treatment of
effluents.
One of the study mills in the NCASI's survey attributes about 30% color removal
in the effluent treatment system to the presence of lime in the influent. The mill
adds 40 tpd of lime (about 320 ppm) to neutralize the mill effluent. Any precipitate
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VGnt
is removed in the primary and secondary clarifiers with the sludges and taken to
landfill. That mill does not experience any special issues with sludge handling.
Cost for operating this system was estimated to be $23 million a year, which included
depreciation and capital recovery. The cost for installing a lime color removal system
was estimated to be $55 million (1987 cost). Further study of this technology at the
Canton mill is not recommended.
Alum precipitation
One of the Study Mills adds an aluminum-based salt to its activated sludge
process for color control. The addition is controlled depending on the season and
varies between 40 - 88 ppm. The color reduction in the activated sludge process
increased by about 30% when the AI-salt was added.
Most of the installations utilizing alum treatment are tertiary treatment
installations, using aluminum and/or iron salt with or without polymer addition as
a coagulant (mechanical/recycled paper mills). The main drawback of the
coagulation/precipitation methods has been the disposal of the formed sludge
Iron Precipitation
One example of tertiary treatment using iron is the Fennotriox process by
Kemira. Fennotriox uses both oxidation and coagulation to remove pollutants.
The Fennotriox process uses ferrosulphate (a waste) in combination with
hydrogen peroxide (Fenton reaction) in a chemical effluent treatment plant. The
reactions between the metal salt and peroxide will produce radicals that can
oxidize organic compounds in the effluent.
No full-scale applications of the Fenno-Triox process are known. Tertiary
treatment with ferric - aluminum sulfate (AVR) without hydrogen peroxide
is done in a few Scandinavian mechanical pulp and paper mills for
phosphorus control.
Polymer Precipitation
Polymers have been used in primary, secondary and tertiary coagulation and
flocculation treatment of industrial effluents.
Two of the Study Mills in this survey use polyamine to remove color. One mill
adds polyamine to a spare clarifier that contains diverted highly colored effluent.
The other mill adds polyamine to a process effluent stream that contains mainly
black liquor. About 4700 IBM/day is added to 17000 gpm of effluent (23 ppm) to
remove about 100 t/d of color (we suspect that this number is high).
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Stone Container has used this process at their mills in Missoula, MT and Hodge,
LA. Stone Container also has a patent (U.S. patent 4,724,045) for the removal of
color from alkaline pulp and paper wastewaters using a polyacrylamide
coagulant.
The Stone process is also used at the mill in Skookumchuck, B.C., Canada
(Hodgson, 1997; Stevenson, 1995). The Skookumchuck mill has a river-based
color limit. With the Stone process they report color removal rates of 55-80%
depending on effluent characteristics and polymer type. The mill has also
reported reductions in other parameters, including BOD, suspended solids, COD
(22% removal), and AOX (23% removal). The sludge from the flotation unit is
returned to the black liquor evaporators where it is combined with the black liquor
and incinerated in the recovery boiler. Figure 8.2 shows the process used at the
Skookumchuck mill. Because of the high cost of the polymer treatment the mill
has studied the recycling of the EoP filtrate as an option to reduce effluent color
(see Section 6.2.2.3).
F-om To ouaau
secor4 ry�
From ! Di31oMa0 Nr
Coop Irn Fblapon O.M.
seta'
Frain '�
FNZWant
Swge W W"k
+fuYF,�I�^Cwa� Black Lk7uo„Ter,k
Color removal process used at Skookumchuck (Hodgson, 1997)
COLOR REMOVAL: OXIDATION PROCESS
Peroxide treatment of EoP Filtrate
Peroxide treatment of EoP filtrate has been used in the Grande Prairie AB.
Canada since 1997
The major advantage of this technology is the low capital cost involved. Also, the
process is easy to operate and the influent color can be controlled to a desired
level.
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The peroxide treatment system at the mill in Grande Prairie included mixing of
the aqueous peroxide solution with E-stage filtrate leaving the seal tank. The
mixture was allowed to react in a retention tank for 0.5 to I hours before being
discharged to the sewer. The system included the following main equipment:
Peroxide delivery system
Retention tank
Level and dosage control systems.
This system is currently not in use after installation of oxygen
delignification.
The peroxide treatment technology is simple, involving primarily the mixing of
chemicals and retention of the mixture. Up to 30%- 50% reduction of E-stage
color has been reported to be achievable (Wohlgemuth, 1997). Peroxide
treatment can also reportedly reduce BOD and COD (Robinson, 1994).
Enhanced Peroxide Treatment with Catalyst of E, Stage Effluent
This process is similar to peroxide treatment except that a catalyst is added to
the reactor to enhance the treatment. Catalysts (TAML) are currently being
developed at Carnegie Mellon University (Wingate, 2001, 2004).
TAML (tetra amido macrocyclic ligand) iron (III) catalysts are one-time-use
hydrogen peroxide activators. By using TAML catalysts with hydrogen peroxide,
color and AOX can be removed from E-stage effluent.
Bench scale and pilot scale tests have been conducted on softwood (pine) and
hardwood (eucalyptus) E-stage effluent at a Kraft mill in New Zealand. The
TAML catalysts function best under alkaline conditions and with efficient
agitation to achieve the maximum color removal. The pilot plant tests consisted
of two vessels, a 200 L vessel with a hydraulic retention time of one hour, and
an 800 L vessel with a hydraulic retention time of four hours.
The vessels were operated in series with a flow rate of 3.3 L/min and chemical
addition to the first vessel. It was determined that a reaction time of one hour
provided suitable color removal. The table below shows the results of the pilot
testing. As can bee seen in the table, TAML catalyst is more effective for
softwood (pine) effluents than for hardwood (eucalyptus) effluents.
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TAML Catalyst Pilot Plant Results on Bleach Plant Alkaline Effluent
Chemical Application Parameter Colo AOX
_ ur
0.5 pM catalyst, 6.5 MM H2O2, pine Influent 18±4 0.41±0.11
(0.23 mq/l, catalyst, 190 mq/1 TAML treated 10±3 0.34±0.05
Removal (%) 46
1 gM catalyst, 13 mM H202, pine Influent 23±3 0.38±0.10
TAML treated 8±1 0.31±0.09
Removal (%) 67
2 uM catalyst, 22 mM H2O2, pine Influent 25±3 0.38±0.04
TAML treated 6±1 0.26±0.04
Removal (%) 78 32
2 pM catalyst, 22 mM H2O2, Influent 2.9±0. 0.22±0.09
TAML treated 1.6±0. 0.12±0.06
Removal (%) 45
Conditions: pH 11.8, 1 hr, 60 °C
In previous work the authors of the study noted that the addition of hydrogen
peroxide alone caused an increase in the color at 400nm wavelength due to the
formation of a finely divided precipitate. The TAML catalyst is short lived and
degrades after about 10 minutes at the reaction conditions. Therefore, Microtox
toxicity testing was also done on the pilot plant effluent to determine if the
catalyst degradation products impacted effluent toxicity and no toxicity was
found.
Currently this technology is not commercially viable because the TAML
catalyst is not produced on an industrial scale. When the TAML was added
to the EoP tower at another mill site, the catalyst use was lower than when
the Eop filtrate was treated. The TAML may thus be more effective when
added in the bleaching process.
Ozone
Ozone Treatment Process and Applications
Ozone is a gaseous oxidant with a high oxidation potential, second only to
fluorine, preferentially attacking compounds which consist of carbon-carbon
double bonds (color causing structures) and organic functional groups. Any
unreacted 03 decomposes rapidly to 02• The reactivity of ozone is not dependent
on temperature and favors lower pH's. Therefore, ozone treatment may be
applied on the total effluent as well as on any particular stream.
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GUI'l
Ozone could be added to the D or EoP stage effluent or the total mill effluent. The
gas would be dissolved into the effluent by means of diffusers or other similar
equipment in an airtight tank with a detention of approximately 10 - 20 minutes.
Any residual ozone in the off-gases would be destroyed before venting to the
atmosphere.
The scope includes the following main equipment:
• Ozone delivery system
• Retention tank
Off-gas treatment unit.
The production of ozone is proven technology. Ozone treatment of water for
disinfection purposes is a well-established technology employed at several
municipal water and wastewater treatment plants.
In the pulp and paper industry the D and E stage and total mill effluents have
been targets for much lab and pilot-scale testing with ozone. However, no full-
scale ozone effluent treatment has been installed on Kraft mill effluents.
The potential environmental risks are related to the following issues:
• Color reversion in ASB
• Possible BOD increase
• Environmental impact of 03 oxidation products
Residual ozone air emissions.
Impact on Color when Treating Bleach Plant Alkaline Filtrate with Ozone
A 60% reduction of E-stage filtrate color would be expected, assuming no color
reversion in secondary treatment. Literature results are varied on color reversion,
with some studies showing reversion, some no change, and some further color
reduction in the treatment system. In one study ozone was applied to the alkaline
bleach plant effluent from a bleached Kraft mill (Norske Skog, Elk Falls, BC,
Canada) (Bijan, 2003).Color removal from the alkaline bleach plant (bench scale
testing) showed 70% removal of color.
Impact on Color when Treating Combined Mill Effluent with Ozone
Ozone treatment can reduce up to 80% of whole mill effluent color with an inlet
ozone concentration of up to 3.0% by weight according to results from pilot-scale
tests with ozone at a softwood Kraft pulp mill (Zhou, 1996). Bench scale testing
used effluent from a stilling basin following an aerated lagoon. The whole mill
effluent had the following characteristics:
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Parameter Unit Value
COD mq/1 485
BOD5 mq/I 11
TOC mq/I 192
AOX mo/1 7.77
Color TCU 943
off 7.62
Total Mn mq/I 0.62
The color removal for an inlet gas flow rate of 1500 ml/min and an ozone
concentration of 3.0% by weight is shown in the Figure below.
1000 20
-4- effluent color
800 E -o- off-gas ozone j
16
✓"" O
v 600 12 c)
I-- j
t a
c 400 8
v tiQa
200 Q , I - ) mL:mtn - 4
C ,r U °'h
0 0
0 6 9 l � I
Time. mm
Pilot testing on whole mill effluent using ozone was also conducted at the
Tenneco Packaging containerboard mill in Valdosta, GA (Love]], 1997). Color
removal of about 90% was achieved.
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BOD
The breakdown of organic molecules increases the potential of BOD formation
(Zhou, 1996), by one estimate increasing the raw BOD load to treatment by 5-
10%. This low MW BOD may, however, be treated more easily with biological
treatment, so the net impact on BOD may be low.
COD and TDS
As a result of oxidation, COD and TDS may be reduced by approximately one-
third of the ozone dosage.
Ozone with Biological Filtration
This process is applied at a paper mill in Germany (Schmidt, 2000). The tertiary
treatment step consists of ozone treatment followed by biological filtration. The
ozonation stage consists of two reactors in parallel. Ozone is mixed with the
wastewater and flows into the reactor. The off-gasses from the reactor are used
as such, i.e. no off-gas destruction, in an AST. The wastewater from the ozone
reactor flows to a holding tank with a 1.5 hour retention time that allows the
remaining ozone to dissipate and protects the biofilter from ozone shock. The
biofilters consist of three rotating filter units with air and wastewater feed to the
bottom and a design speed of 4.5 rpm. The system was designed to minimize
COD and BOD discharges.
There are no units operating at pulp mills.
Emeraing External Treatments
Chemical Destruction
The mineralization of AOX is the hydrolysis of organic chlorine compounds under
alkaline conditions to produce inorganic chlorides. Subjecting E-stage
ultrafiltration concentrates at pH's up to 12.5 to high temperature (100°C)
decreases AOX concentrations by up to 50%(41,42). AOX reduction by hydrolysis
also will take place in a conventional wastewater treatment plant when
chlorination effluent is subjected to an alkaline pH, increased temperature and
time(43). At usual bleach plant operating temperatures (60 to 80°C),AOX removal
of from 54 to 67% was obtained at pH of 11 using Ca(OH) or NaOH respectively.
Substituting weak black liquor for NaOH increased the AOX removal by up to
30% more 44). Increasing the temperature to 150°C and pressure to 475 kPa
increased the AOX removal to 80%(44)
Biological Treatment
Certain fungi such as white-rot fungus, Phanerochaete Chrysosporium in a
rotating biological contactor has been found to remove AOX and color for a
bleach plant effluent stream. Most methods using biological treatment depend
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upon treating selected bleach plant effluent or concentrated streams of effluent
from active carbon adsorption or ultrafiltration processes(","). White-rot fungus
dechlorinates the bleach plant effluent by converting the organically bound
chlorine to inorganic chloride. Color and AOX destruction by the fungus is
accomplished by a family of enzymes the fungus excretes; there are some 15
extracellular enzymes that are produced by the fungus(47). These enzymes which
can degrade lignin and lignin modified during pulping and bleaching are called
peroxidates(47).
To decrease the potentially high cost of this type of treatment ($6-$8/adt), the
white-rot fungus was immobilized on granular activated carbon. One major
problem was the dissociation of the hydrogen peroxide produced by the fungus
on the activated charcoal carbon structure. Research on bench scale fluidized
fungal experimental systems where the fungi is immobilized on granular activated
carbon and employing a recirculating reactor loop showed that the chlorinated
organics were reduced to below the limits of detection within eight hours(49)
Photo-oxidations
Photo-degradation reactions are initiated when bonding electrons absorb a
quantum of light whose energy corresponds to an energy difference in the
electronic state of the absorber(50). Results of studies showed that when whole
mill effluent was irradiated at 254 nm in the presence of an oxidant catalyst, Ti02,
the degradation of the effluent was greatly increased at 50°C; the degradation is
strongly dependent on the intensity of the irradiation.
Aeration of the effluent by oxygen not only maximizes the degradation but cause
the rate to be independent of pH, improving the techniques applicability to
different bleaching effluent streams. Under the best present known condition a
dark colored mill effluent can be treated by photo-oxidation to produce a clear
solution with low or no toxicity in less then 30 minutes(49)
Thermal Destruction
As bleached Kraft mills move towards closed mill technologies using either
polymer, resin, ultrafiltration or activated carbon treatment they will produce
concentrated effluent streams that may contain high concentrations of
chlorinated organic and inorganic chlorides(51). Presently the only mill technology
for treating these concentrates is by treatment in multiple-effect evaporators
followed by burning in the recovery furnace. This raises the problem of the high
chloride residual in the various process streams and the possible corrosion of the
evaporators.
As an alternate technology the thermal destruction approach in equipment other
then a Kraft recovery furnace is now under investigation. Initial results were
obtained by examining effluent concentrates obtained by ultrafiltration and
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VGLA/
reverse osmosis. These concentrates were analyzed for their solid content, color,
AOX, total organic carbon, metals, heating value and ash content. Ultrafiltration
concentrates were found to be more desirable as a fuel then the reverse osmosis
concentrates due to the higher level of carbon organic to inorganic ratio, heating
value and lower levels of ash. The heating values of ultrafiltration concentrates
are in the range of 12,000 to 19,200 kJ/kg which are in the same range as that of
black liquor solids. The organic content to inorganic content also effect the
heating values, since the organics are major contributors to the net heating value
while the inorganics are not. It is important to note that the air emission should
be monitored for potential PCDD/PCDF emissions which may be eliminated
when the effluent concentrates are mixed with a small quantity of black liquor or
other suitable absorbers are used(51).
Thermal destruction technologies include: rotary kiln incinerators, circulating
fluidized bed combustors, gasification of waste to medium or low BTU fuel gas,
and co-firing waste with other fuel, such as black liquor bark, coal, oil and gas.
COLOR REMOVAL-FUNGUS/BACTERIA/ENZYMES
White-Rot Fungus Treatment
Various strains of white-rot fungus have been known to be able to degrade lignin
as a "secondary metabolism," meaning lignin would be metabolized if a certain
growth factor becomes limited. This ability is not lost when the lignin becomes
chlorinated in pulp bleaching, so the fungus has become of interest in removing
chlorolignins and chlorinated phenolics in bleach plant effluents as a means of
reducing effluent color and toxicity
Several parallel research programs have been pursued and the one most
advanced at this point is the "MyCoR" process at North Carolina State University.
In this process the fungus is immobilized on a series of flat disks, which are
mounted in parallel on a rotating horizontal shaft such that portions of each disk
are alternately submerged in the waste operation. Either 1- or 2-day retention
time would probably be required (Pellinen, 1998).
Since the fungus cannot use lignin as an energy source, it must be supplied one.
If the stream to be treated does not contain enough energy sources, such as
hemicellulose, suggested possible additives are glucose, xylose, cellulose, or
possibly primary sludge. In addition, the pH should be between 3 and 5, the
temperature between 28 - 40 °C, and nitrogen should be the limiting nutrient.
Other white-rot fungal treatments include the MyCoPor (Messner, 1990) and
immobilized fungal fluidized bed bioreactor.
The MyCoPor process is a trickling filter that immobilizes the fungus on the
surface of polyurethane foam cubes. Both the MyCoR and MyCoPor use passive
immobilization, i.e., adhesion of cells to a solid support.
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The immobilized fungal fluidized bed bioreactor uses entrapment of the fungus in
urethane foam Pallerla, 1996). This active immobilization results in a media with
a high resistance to deterioration by mechanical action and pH. This reactor is
effective at removing color and AOX, with removal efficiencies of 70% and 50%,
respectively.. The reactor was fed a mixture of 60% D stage effluent and 40% E-
stage effluent obtained from a mill with a OD(EO)DED bleaching sequence. The
reactor functions best at a pH of 5 and due to the porous nature of the urethane
foam, transport processes are non-diffusion limited. As with other white-rot
fungus treatments, an energy source for the cells must be supplied. In this case
glucose at 8 g/I would be recommended along with nitrogen and phosphorus.
Currently this technology is in the pilot scale phase. Some mill testing has
done but the results were not successful for color removal. Blue Ridge
Paper was one of the mills to test this technique without success.
Methods for Recycling Effluent
Other methods of closing up existing mills, as well as in Greenfield mill, include
technologies for bleach plant in-plant and external control using:
• Membrane process: ultrafiltration and reverse osmosis
• Resin process
• Activated carbon adsorption
• Chemical coagulation:
(a) lime
(b) alum
(c) ferric chloride or sulfate
(d) organic polymer treatment
• Paper machine white water reuse in the bleach plant
• New bleaching sequences
Membrane Processes
1. Ultrafiltration is a membrane process that can decrease color and AOX in the
effluent. The process involves a physical separation of the components by
applying pressure to the fluids being cleaned. The selectivity of the
membrane depends upon its pore size. Ultrafiltration is usually done in the
10 to 175 psi pressure range and the molecular weight separation can be
varied from 1,000 to 1,000,000. Ultrafiltration is used primarily on extraction
stage filtrate, where approximately 80 to 90% of the color, 70% of the COD
and 25% of the BOD are removed(52) It has also been reported that a
significant fraction of the resin and fatty acid are removed but low molecular
chlorinated phenolics are not removed(53). Typical operating costs are $6/adt
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for the filtration equipment and $15-20 million for installation cost excluding
incremental evaporation capacity.
2. Reverse osmosis is a high pressure membrane process in which dissolved
solids are separated from water by applying a pressure higher than the
osmotic pressure. Applying pressure to the feed stream of effluent, water
will permeate through the membrane from the area of high dissolved solids
concentrated to the area of low solids concentration, producing clean water.
Reverse osmosis membranes are made from a multitude of materials
including acetate, polyacrylic acid, cellulose and other cross-linked polymers.
The reserve osmosis system usually operates at pressures of 100 to 1500
psi. Information from laboratory and pilot plant studies have been reporte&54)
and a full-scale reverse osmosis system was installed at a NSSC corrugating
milli55) but later abandoned due to the unavailability of suitable membranes.
Cost of operating a reverse osmosis system in conjunction with ultrafiltration
or diafiltration or freeze concentration of the concentrated material ranges
from $10-30/adt with a capital investment on $40 million for a 1000 t/d
mill(53,56)
Areas of Further Research
• Evaluation of different membranes for various applications as membrane
fouling results in flux reduction.
• Low flux rates and a decline in flux rates with time of membrane operation.
• Effect on the recovery system on burning ultrafiltration and reverse osmosis
concentrates. The effect of air emissions.
Resins
Resins, through ion exchange or sorption, remove selected chemicals from a
solution. The resin technology involves pretreatment of the effluent to remove
large particles and to effectively optimize the effluent pH from pH 2.5 to 7
depending on the type of resin used. The effluent is then passed through a resin
column where color and some organic compound ions are removed. When the
removal rate of the column drops it is replaced and the resin regenerated. The
material collected from the regeneration process is concentrated and eliminated
from the system. Processes tested and reported upon are the Rohm and Haas
process(57�, the Dow process(58) and the Billerud-Uddeholm process(59) for color
reduction. The latter process is said to also remove organic material (chlorinated
phenols and guaiacols), therefore decreasing effluent toxicity. Color reductions
from 80 to 90% are achieved, while BOD decreases of 50% have been
reported(59). The estimated operating cost in 1981 was between $7.75-10.25/adt
assuming a 2-year life of the resin. The equipment and installation costs were
$1,300,000 for a 1000 AD/t pulp production.
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Area of Further Research
Evaluation of different resins for various applications, including removal of other
chemical components.
Active Carbon Adsorption
The use of activated carbon for removing organics from effluent streams has
been known for many years. Activated carbon characterized by a very large
surface area per unit mass (450 to 1800 mz/g) has an extremely high capacity for
surface adsorption of organic molecules with relatively low water solubility.
It has been reported that activated carbon in laboratory and pilot plant studies
removed greater than 90% of the color from extraction stage filtrate( 61) and that
the spent carbon could be regenerated several times with caustic before thermal
regeneration was required.
The annual operation cost, including depreciation and capital cost recovery for
this system, was estimated to be $42 million (1987 costs) while the cost of
installation of an activated carbon system at a mill to treat the entire secondary
effluent was said to be $117 million(6 �.
Further Research Needs
Problems to be solved include:
• Frequent plugging of carbon beds with suspended solids
• Absence of a reliable technology for treating the concentrates from carbon
regeneration at bleached Kraft mills.
• Biological growth in carbon columns along with gassing off.
Chemical Coagulation
Chemical coagulants such as lime, alum, ferric salt, ferric chloride and ferric
sulfate, along with organic polymer (polyelectrolyte), are known to destabilize
large organic molecules contributing to the color of the effluent and produce
flocs. The resulting flocs can be separated from the water by settling or air
flotation and thus removed. Only lime treatments will be discussed since all the
above processes remove color, but lime has been shown to also remove AOX.
Lime Treatment
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Several massive lime treatment processes are known and the results from the
International Paper Company's mill at Springhill, Louisiana study reported(611
slaked lime was applied to a colored extraction filtrate and allowed to settle out in
a primary clarifier. The clarifier effluent was recarbonated with CO2 to recover
the soluble lime. The results show that 90-95% of the color can be removed.
Recently(64�, it was shown that 80% of the AOX can also be removed by massive
lime treatment. Only one such system is presently operating.
Cost for operating this system was estimated to be $23 million a year, which
included depreciation and capital recovery. The cost for installing a lime color
removal system was estimated to be $55 million (1987 cost).
Further Research Needs
Given the sludge from the clarifier would be dewatered and sent to the lime kiln,
the effect of chloride ions along with other metals would have to be fully
examined.
The effect of increased dissolved solids resulting from implementing this
technology is not known and would have to be elucidated.
Paper Machine White Water Reuse in the Bleach Plant
To decrease fresh water use in several mills, the bleach screen room and paper
white water are used for diluting pulp entering the bleach plant from the HD
storage chest but usually for diluting pulp leaving the final bleach plant washer.
Some mills reported using machine white water on showers of the chlorination
and extraction stage washers. Shower washers are required to operate a large
number of sprays. The quality of water coming from the paper machine was both
screened and clarified to remove impurities that may affect the bleaching
process.
References
1. Sjoblom, K., Mjoberg, J., and Harder, N. - Paperi ja Puu 65:227 (1983).
2. Axegard, P., and Wiken, J.E. - Svensk Papperstidning (86):R178 (1983).
3. Harder, N., and Olsson, L.A - Svensk Papperstidning (75):Nr13 (1972).
4. Bennington, C.P.J. and Pineault, I., Pulp & Paper Canada 100:12(1999).
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IGBI
5. Germgard, U., and Norden, S., "OZP - Bleaching of Kraft Pulps to Full
Brightness", 1994 International Bleaching Conference, Vancouver, BC,
TAPPI, SPCI, EUCEPA, and CPPA, p. 53-58.
6. Tibbling, P. and Dinner, B., "TCF Bleaching can be Carried Out with
Difference Bleaching Systems", 25th EUCEPA Conference, 1993 Vienna,
Austria, 842 pp.
7. Dillner, B., and Tibbling, P., "Optimum Use of Peroxide and Ozone in TCF
Bleaching", 1994 International Bleaching Conference, Vancouver, BC,
TAPPI, SPCI, EUCEPA, and CPPA, pp. 319-333.
8. Sjodin, L., Solverg, N., and Bomar, R., "Extended Delignification in Oxygen
and Hydrogen Peroxide in ECF and TCF Sequences", Proceedings of the
1994 TAPPI Pulping Conference, San Diego, pp. 21-27.
9. Basta, J., Holtinger, L., Lundgren, P., Fasten, H., Fredriksson, R.,
"Alternatives for Achieving High Brightness TCF Pulps". Proc. of Non-
Chlorine Bleaching, Amelia Island, FL, USA, 1994.
10. Axegard, P., Ekholm, U., `Peroxide-Based TCF Bleaching Basics and New
Development', Workshop on Emerging. Pulp Tech., Durham, April 1995.
11. Basta, J., Holtinger, L., Hermansson, W., and Lundgren, P., "Metal
Management in TCF Bleaching", 1994 Int. Pulp Bleaching Conference,
Vancouver, BC, TAPPI, SPCI, EUCEPA, and CPPA, p. 29.
12. Basta, J., Holtinger, L., Lundgren, P., and Persson, C., "Emerging
Technologies in TCF Bleaching". Proceedings of the 1995 TAPPI Pulping
Conference, Chicago, p. 53-57,
13. Breed, D., Shackford, L.D., Pereira, E.R., and Colodette, J.L., "Cost-
Effective Retrofit of Existing Bleach Plants to ECF and TCF Bleached Pulp
Production Using a Novel Peroxide Bleaching Process". Proceedings of the
1995 TAPPI Pulping Conference, Chicago, p. 779-788.
14. Liebergott, N., 'The Use of Ozone in the Bleaching and Brightening of Wood
Pulps", 1979 Preprints of Fundamentals of Ozone Technology Seminar, The
Center for Professional Advancements, East Brunswick, NJ, July 23-25,
1979.
15. Lachenal, D., Taverdet, M.T., Muguet, M., "Improvement in the ozone
Bleaching of Kraft Pulps", Intern. Pulp Bleaching conference, SPCI,
Stockholm, 1991, pp. 33-43.
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16. Dillner, P., and Tibbling, P., "Use of ozone at medium consistency for fully
bleached pulp. process concept and effluent characteristics. TCF bleaching
can be carried out with different bleaching systems", Intern. Pulp Bleaching
Conference, SPCI, Stockholm, 1991, pp. 59-73,
17. Tsai, T.Y., US Pat. No. 4,959,124 (Sept. 25, 1990).
18. Lachenal, D., Muguet, M., "Degradation of Residual Lignin in Kraft Pulp with
Ozone', Nordic Pulp & Pap. Res. Journal, No. 1/1992, pp. 25-29.
19. Liebergott, N.L., Ozone Tutorial. Preprints of the 1996 INCBC, Orlando,
Florida.
20. Munro, F., and Griffiths, J., "Operating Experience with an Ozone Based
ECF Bleach Sequence.
21. Str6mberg, B., and Szopinski, R., "Pressurized Hydrogen Peroxide
Bleaching for Improved TCF Bleaching", 1994 International Bleaching
Conference, Vancouver, BC, TAPPI, SPCI, EUCEPA, and CPPA, pp. 199-
209.
22. Wiltshire, K., Steffes, F., and Reeves, R., 'Pressurized Peroxide - A Good
Fit for both the Bleach Plant of Today and the Future", Proc. 1995 Spring
Conf. CPPA Technical Section, Whistler, BC, Canada. Preprints.
23. Stn5mberg, B., "Pressurized Hydrogen Peroxide Bleaching for Improved
TCF Bleaching", 1995 TAPPI Emerging Pulping and Bleaching
Technologies Workshop, Durham, NC. preprints.
24. Devenyns, J., Desprez, F., and Detroz, R., "Enhanced Hydrogen Peroxide
Bleaching Stages for Chemical Pulps". 1995 TAPPI Emerging Pulping and
Bleaching Technology Workshop, Durham, NC. Preprints.
25. Boman, R., Reeves, R., and Nordgren, B., `Pressurized Peroxide Bleaching
- An Important Tool for Modern ECF and TCF Bleach Sequences", Proc.
Nonchlorine Bleaching Conf., Amelia Island, FL, USA, March 5-9, 1995.
Preprints.
26. Breed, D., Colodette, J.L., "Pushing the Peroxide Window", 1995 TAPPI
Emerging Pulping and Bleaching Technology Workshop, Durham, NC.
Preprints.
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27. Reeves, R., Boman, R., and Nord6n, S., "Impact of Sequence Position for
Pressurized (PO) Stages in ECF Bleaching", Proceedings of the 1995
TAPPI Pulping Conference, Chicago, p. 264-279.
28. Roy, B.P., van Lierop, B., Berry, R.M., and Audet, A., "High Temperature
Alkaline Peroxide Bleaching of Kraft Pulps". Proceedings of the 1995 TAPPI
Conference, Chicago, pp. 771-778.
29. Hill, R.T., Walsh, Walker, S.D., and Dutton, D.B., "An Evaluation of
Pressurized Hydrogen Peroxide Systems for Delignification and Bleaching".
Proceedings of the 1995 TAPPI Conference, Chicago, PP. 789-806.
30. Wigren, G.A., Canadian Patent 769,631 (Oct. 17, 1967).
31. Paren, A and Jakara, J. Molybdate Activated Peroxide in ECF Bleaching of
Hardwood Kraft Pulps, Preprints of the 10th International Symposium on
Wood and Pulping Chemistry, June 1999.
32. Roberts, J. `The Organ of Closure", Pulp and Paper Europe, July/August,
1999
33. Gullichen, J., "Displacement Bleaching", The Bleaching of Pulp, TAPPI,
Atlanta, GA, 1979, Chapter 10, pp. 275-291.
34. Cook, R.A., "A Bleaching Process for Minimizing AOX Discharges", Appita
44:(3), p. 179, 1991.
35. Lachenal, D., and Mugent, M., 'Reducing TOCI with OXO with the OXO
Process". Pulp Pap. Mg. Can. 92:12, T297-301, 1992.
30. Histed, J.A., "Simplified Bleaching Process", US Patent 4,238,281, Dec. 9,
1980.
36. Germgard, U., and Steffes, F., "Pulp Washing in a Closed Bleach Plant".
Preprints, Minimum Effluent Mill Symposium, Atlanta, GA, Jan. 22-24, 1996,
p. 115.
37. Luer, M. and Cunnington, R., "Pulp Washing — Controlling Water Use",
Tech. 95 Bleaching Course Notes, CPPA Tech.Sect. 1995.
38. Turner, P., "Water Use Reduction in the Pulp and Paper Industry", 1st
edition, 1994.
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39. Manninen, D. Status Report — another step forward towards the effluent-free
mill. Finnish Trade Review, pp. 14-15, April 1993.
40. Johansson, N.G., Fletcher, D.E. and Clark, F.E. New technology
developments for closed cycle bleach plant. Minutes of the 1995 Spring
Meeting of Tech. Section CPPA Bleaching Committee meeting. Castlegar,
BC, May 1995.
41. Blue Ridge Paper Products Inc.: 2001 Color Removal Technology
Assessments,
42. SUN, Y.B., ET AL, Tappi 72(9):209(1989).
43. German Pat. 3620980 KRAUSE, T. ET AL "Continuously Processing Pulp-
Bleach Effluent', Jan. 14, 1988.
44. DORICA, J., "Removal of AOX from Bleach Plant Effluents by Alkaline
Hydrolysis", JPPS 18:6 P J 231, Nov. 1992.
45. EATON, D. ET AL, "Fungal Decolourization of Kraft Bleach Plant Effluent
the Chromophoric Material', Tappi 64(9):145, 1980.
46. MATSUMOTO, Y., YIN ET AL "Degradation of Chlorinated Lignin and
Chlorinated Organics by White-Rot Fungus". Proceedings of the 1985
International Symposium on Wood and Pulping Chemistry, Vancouver BC,
Canada, Aug. 26-30.
47. HAMMEL, K. ET AL "Oxidation of Aromatic Pollutant by Phanerachaete
Crysosporium Ligninese". Proceedings of the International Seminar on
Lignin Enzymatic and Microbial Degradation, Paris April 23-24 1987.
48. KIRK, J., `Enzymatic Combustion: The Degradation of Lignin by White-Rot
Fungi". Proceedings of the International Seminar on Lignin Enzymatic and
Microbial Degradation, Paris, April 23-24 1987.
49. NCASI TECHNICAL BULLETIN NO. 609, "In-plant and Closed Cycle
Technologies R&D Program-Add On Control Technologies", May 1991.
50. RANBY, B. ET AL, Photodegradation, Photo-Oxidation and
Photostabilization of Polymers", Wiley-Interscience, N. Y.(1975).
51. ADAMS, T.N. at al "Kraft Recovery Boiler Physical and Chemical
Processes", The American Paper Institute, New York, NY, (1988).
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52. Lundahl, H. and Manssin, I., "Ultrafiltration for Removing Color from Bleach
Plant Effluent', TAPPI 63:4, p.97, April 1980.
53. Dorica, J., et al, "Complete Effluent Recycling in the Bleach Plant with
Ultrafiltration and Reverse Osmosis', TAPPI 69:5, p. 122, May 1963.
54. Morris, D.C., et al, "Recycle of Papermill Waste Water and Application of
Reverse Osmosis', US EPA, WCRS Report No. 12040 FUB, January 1972.
55. MacLeod, J.M., "Mill Achieves Maximum Reuse of Water with Reverse
Osmosis', Pulp and Paper (48):12, pp. 62-64, November 1974.
56. Rock, S.L. et al, "Decolourization of Kraft Mill Effluent with Polymeric
Adsorbent:. TAPPI Environmental Conference, April 17-19, 1974.
57. Chamberlain, T.A. et al, "Colour Removal from Bleached Kraft Effluents",
TAPPI Environmental Conference Preprint, pp. 35-45, May 14-16, 1975.
58. Lindberg, S. and Lund, L.B., "A Non-Polluting Bleach Plant, TAPPI (63):3,
p. 65, March 1980.
59. Timpe, W.G. and Lang, E.W., "Activated Carbon Treatment of Unbleached
Kraft Effluent for Reuse. Pilot Plant Results', TAPPI Environmental
Conference Proceedings, pp. 203-218, May 1973.
60. Lang, E.W., "Activated Carbon Treatment of Unbleached Kraft Effluent for
Reuse: Final Report on Part 1", EPA/660/2-75-004, April 1975.
61. Report by Sirrine Environmental Consultants, "Effluent Color Treatment,
Carbon Adsorption — Color Removal". Canton Mill, Champion International
Corporation Mill, North Carolina, April 1987.
62. Oswalt, J.L. and Land, J.G., "Color Removal from Kraft Pulp Mill Effluent by
Massive Lime Treatment', US EPA Environmental Protection Technology
Series, report No. EPA-R-2-73-086 (EPA 12040DYD), February 1973.
63. Dorica, J., Private Communication.
64. Narum, Q.A. and Moaller, D.J., "Water Quality Protection at the Shasta Mill",
TAPPI Environmental Conference Proceedings, April 1977.
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Options for Improved Environmental Performance
Basis for Study
The Blue Ridge Paper Products Inc. mill includes a pulp mill with an average
production in 2005 of 1383 ADBT/day of softwood and hardwood pulp. Prior to
its being purchased by Blue Ridge Paper Products Inc from Champion
International, a major modernization project was undertaken to reduce the
effluent outfall from the mill, and improve the effluent quality. Included in this
modernization was the complete rebuild of the hardwood and softwood fiberlines
and the incorporation of novel technology to improve environmental performance.
In 2001, a Bleach Environmental Process Evaluation was completed and
identified several options to reduce effluent color. Since that time, Blue Ridge
Paper has implemented many changes and studies at the mill to evaluate viable
options. A summary of these initiatives has been discussed in the section titled
"Review of Color Reduction Initiatives since 2001".
An overview of the current softwood pulp production specifications is as follows:
Softwood Pulp
Production = 586 ADBT/Day, average daily rate 2005
Digester K# = 17.5 (Kajaani), 19-19.5 blow tank (lab)
Post-Oxygen K# = 9.5
CEK# = 2.1
Final Quality Targets
86 % ISO Brightness minimum
86.5-87.0% target
15.5 cp viscosity (14 minimum)
<3 Dirt Count
Compared to the 2001 Study time frame, the target CEK # has been reduced by
0.1 unit. In addition, the brightness target has been increased by about 1 unit
due to market demands. All other targets are the same.
The mechanical equipment on the softwood line includes conventional batch
digesters, knotting system, brown stock washers, single stage oxygen
delignification, post-oxygen washers, fine screening system, a vacuum decker
followed by unbleached pulp storage. A 20-30 minute surge tank is installed
between the knotters and the first brown stock washer. The bleach plant
includes a pre-bleach washer followed by a conventional D1EoD2 bleach plant.
All washers are Compaction Baffle Washers, except for the second stage post-
oxygen washer (decker) after screening, which is a vacuum washer.
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The surge tank provides for leaching and extraction of the lignin from the pulp
due to the high temperature and alkalinity at this point in the process. The PN
measured by the Kajaani is sampled at the feed to the final pre-oxygen washer,
while the lab sample is from the feed to the knotters. In general, the lab and
Kajaani kappa measurement is very close, so this means that the effect of
leaching is the equivalent of 2-2.5 PN drop (3.2-4 kappa drop*). This means that
data on degree of delignification for softwood pulp when using Kajaani readings
vs. the lab readings is significantly different. The overall impact on %
delignification is up to 5% vs. the Kajaani readings.
* Kappa No. = 0.293 + ("K" No. x 1.47), (BRPP relationship)
The softwood fiberline is unique in the world due to the incorporation of the
Bleach Filtrate Recycle (BFR®) process. In this process, the D, filtrate is treated
in a Metals Removal Process (MRP), after which is recycled for washing on the
bleach pre-washer and the D, washer as shower water. Metals are purged from
the system in the acid effluent. The Eop filtrate is largely recycled to the decker
filtrate. This process results in the transfer of a high level of chlorides to the
recovery cycle. An additional component of the BFR® process is a Chlorides
Removal Process (CRP) installed at the electrostatic precipitator. It is at this
point that chlorides are removed from the system to prevent buildup of chlorides
in the recovery cycle and prevent potential boiler corrosion.
This process has been optimized such that 80% of the bleach effluent is
generally recycled to the recovery process, thus achieving a very low effluent
volume, and subsequently less discharge of undesirable characteristics, in
particular color and toxicity.
An overview of the current hardwood pulp production specifications is as follows:
Hardwood Pulp
Production = 797 ADBT/day
Digester K# = 10.5-10.8
Post-Oxygen K# = 6.2
CEK# = 1.7
Final Quality Targets
86 % ISO Brightness minimum
86.5-87.0% target
15.5 cp viscosity (14 minimum)
<3 Dirt Count
Compared to the 2001 Study time frame, the target CEK # has been reduced by
0.7 unit. The brightness target has been increased by about 1 unit due to market
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demands. The viscosity is actually the same target as in 2001, except for the
period of the study (there had been some serious issues with the start up of a
paper machine, and it was initially believed to be due to pulp viscosity). All other
targets are the same.
The mechanical equipment on the hardwood line includes equipment that had
largely been in operation prior to the major modernization project, but with
reconfiguration and upgrades to key pieces of machinery for improved
performance. The line includes conventional batch digesters, knotting system,
four stage vacuum brown stock washers, single stage oxygen delignification
system, a vacuum first post-oxygen washer followed by screening and two
deckers in parallel, followed by unbleached pulp storage. The bleach plant
includes a pre-bleach vacuum washer followed by a conventional DIED2 bleach
plant. All washers are vacuum washers.
The current fiberline equipment configuration for the hardwood and pine lines is
included in Appendix 3 in this report.
Based on the current configuration of the mill, and the operating practices
reviewed during the Site Audit, we have evaluated several options for
consideration for reducing color discharges, while not increasing effluent toxicity.
The commercial status of each of these technologies are summarized in the
previous section of this report entitled "Overview of Technology Options'.
Several of these technologies have the potential to achieve color reduction in the
effluent, may be considered commercially demonstrated, and may achieve the
projected performance with a reasonable degree of confidence. Some of these
technologies, however, will require very high capital investment per #/color/day
reduction. Any option, which is deemed of interest to Blue Ridge Paper Products
Inc., must be properly studied in further detail, including comprehensive
laboratory simulations and in some cases, mill scale trials in advance of any
decision to proceed.
All environmental impact projections are based on outflow from the bleach
plant to the effluent treatment plant and do not necessarily translate into
equivalent reductions in whole mill effluent color
The basis upon which effluent color reductions are based is as follows, and is
based on data given by the mill. Should a different baseline be identified, the
color reductions will increase or decrease in direct proportion to the change in the
baseline:
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Pine Sewer
Stage Color, #/day Color, #/ton
Di 2790 4.7
E9 4450 7.6
D2 920 1.6
Total 8,160 Wday 13.9 #/t
Hardwood
Sewer
—Stage Color, #/day Color, #/ton
D, 4570 5.7
E 3650 4.6
Total 8,220 Wday 10.3 Wt
Combined Total 16,380 #/day
Acid from Bleach Stages)
Stage Color, #/da
Pine D, 2790
DZ 920
HW Di 4570
Total 8,280 #/da
Alkaline (from Bleach
Stages)
Stage Color, #/da
Pine Ea 4450
HW E 3650
Total 8,100 Wda
Combined Total 16,380 #/day
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Options Studied for In-Process Changes
Several of the technologies described in the previous section have been
commercially demonstrated sufficiently to make reasonable projections on the
impact that these technologies may have on the Canton mill. Each of these
technologies appear to be viable technologies for implementation at the Canton
mill, but we recommend that each case be studied in further detail to confirm
logistics of implementation, and confirm availability of power and other utilities
that may be required for operation. The technologies that have been reviewed
are:
Conversion to Extended Delignification on the hardwood and pine lines
Conversion to Two Stage Oxygen Delignification on the pine line
Conversion of E Stage to EoP stage in hardwood line
Conversion of E Stage to PHT (hot peroxide) stage in hardwood line
Conversion of Eo Stage to EoP stage in pine line
Conversion of Eo Stage to PHT (hot peroxide) stage in pine line
In each case, we have quantified the impact on bleach chemical use, water use,
and effluent flow, and commented on other impacts which will need to be
assessed in greater detail, such as space requirements, utilities required (steam,
power, etc.). In addition to the impact on color in the effluent, we have
summarized in tabular form, for each option, the impact on the water use, effluent
flow, AOX, Toxicity, Temperature, and Pulp Quality.
We have also categorized the level of commercial experience with each
technology as it relates to the products manufactured at the Canton mill site.
Low 0-3 similar installations in operation
Moderate 4-10 similar installations in operation
High >10 similar installations in operation
During the site audit, it became apparent that there are a number of current
limitations at the mill regarding space and utilities supply. In many cases, the
changes which may be considered for the Canton mill may require incremental
utilities (steam and power), or may increase the load on the existing
infrastructure (causticizing and lime kiln).
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At this level of detail in a study of this nature, it is difficult to arrive at capital cost
estimates with any significant level of confidence. Installation costs at existing
mills are very site specific and require the development of process flowsheets
and preliminary layouts of equipment. However, as requested, we have included
a rough estimate of capital cost for each option, and have identified a category of
possible capital cost for each option as follows:
Low <$1 million
Moderate $1-5 million
High $5-10 million
Very High >$10 million
In some cases, the capital cost of support facilities (steam and power, in
particular) may be far greater than the cost of the changes to the fiberline. The
categories of capital cost consider only the changes to the fiberline.
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Conversion to Extended Delignification
Most major rebuilds of fiberlines today include digester designs that are capable
of extended delignification. The strategy in operation of the cooking system;
however, is site specific. The optimum kappa number for any given pulp is
dependent on the yield characteristics of the wood, the steam/power balance in
the mill, and the bleaching sequence/bleach chemical costs. Extended
delignification may be implemented at the Canton mill with low risk, but high
capital cost.
Hardwood Softwood
Kappa
Digester _
Post-OZ - =
Future
Digester 12 24
Post-02 7 13
Bleach Chemical
Kf —_
Do, % —
Eo/EoP NaOH,
D2, % —
Color Current #/Day 8,220 8,160
Reduction % 20% 15%
Reduction #/Day -1,644 -1,224
Impact
Water Use N/C N/C
Effluent Flow N/C N/C
AOX kg/t -0.11 -0.26
Toxicity N/C N/C
Temperature N/C N/C
—Pulp Quality Significant Increase Significant Increase
Commercial Experience High Hi h
Operating Cost Decrease Decrease
Capital Cost Very High Ve Hi h
The replacement of the conventional batch digesters at the Canton mill will have
a major, positive impact on the overall energy balance of the mill. Modern
displacement batch and modern continuous digesters have been demonstrated
to have very low steam use (about 0.5 and 0.9 t steam/t pulp, respectively), and
produce high quality, high yield pulps. The barrier to cooking to lower kappa
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VIGIN
numbers is usually that most mills are recovery boiler limited, and therefore do
not have the capacity for additional solids load to recovery. This is also the case
at Canton, and it is expected that the incremental solids load can not be handled
with minimal capital cost. There is, however, an incremental load in white liquor
use to produce low kappa pulps, which may require concurrent investment in the
causticizing and lime kiln area.
The key benefits to Canton for replacement of the cooking system is:
Significant decrease in steam use
Significant increase in pulp strength
Minimizing the peak steam demand in cooking
Lower kappa variability (lower standard deviation)
More uniform pulp quality
Lower rejects
Reduced bleach chemical consumption
Reduced effluent outfall
Increased yield
Modern cooking systems to practice extended delignification can be either
continuous digesters (Kvaerner and Ahlstrom) or displacement batch (GL&V or
Metso). All of the benefits listed above apply to both technologies, although
continuous or batch technology may have an advantage in any specific mill and
application. The major differences between the two technologies as it applies to
the Canton mill are as follows:
Continuous digesters require significantly less space for installation
Displacement batch digesters have a significant advantage in quality
(minimum off-quality pulp) for a mill that produces both hardwood and
softwood pulp.
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Conversion to Two Stage Oxygen Delignification
The design of commercial oxygen delignification stages has evolved significantly
since its introduction in the 1970s. Most new installations are operated at
medium consistency, with the majority of the operating installations being single
stage with nominally 60 minutes retention time. Two stage oxygen delignification
systems have become well accepted in the industry, especially for softwood
pulps. In addition to bleach chemical cost savings, environmental benefits can
be achieved due to the lower kappa number entering the bleach plant.
Hardwood Pine
Current Kappa (PN)
To
To Bleach Plant
Delignification, % _
2-Stage 02 kappa 8.0 (5.5) 13.2
0 Kappa 0.8 (0.5) 2.2
Delignification 46.6% 52%
Color
Current#/Day 8,220 8,160
Reduction % 9% 14%
Reduction #/Day -740 -1,142
Impact
Water Use N/A N/C
Effluent Flow N/A N/C
AOX kg/t -0.05 -0.1
Toxicity N/A N/C
Temperature N/A N/C
Pulp Qualit Niscosit N/A Potential improvement
Impact on Operating Cost -0.2% C102 -0.2% CI02
-0.2% NaOH -0.2% NaOH
+Steam +Steam
+Power +Power
+02 chemicals +02 chemicals
Commercial Experience High High
Operating Cost Not recommended Decrease
Capital Cost Not recommended Moderate
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Due to the very small impact expected on hardwood pulp (-0.8 kappa unit
reduction), we do not recommend the installation of two stage oxygen on the
hardwood side. This small reduction in kappa will result in only a very small
bleach chemical savings and very small reduction in color in the bleach effluent.
The conversion to a two stage oxygen delignification system may require an
upgrade to the pressure capability of the medium consistency pump feeding a
new reactor vessel. The new reactor vessel will be sized for 15-30 minutes
retention time, and will be a straight walled cylindrical upflow vessel, similar to
the existing oxygen reactors in the mill. A second point of addition of steam,
oxygen, and alkali, with their associated controls will be necessary. A simplified
schematic of this conversion is shown on the next page.
The implementation of a second oxygen reactor ahead of the existing oxygen
reactor is simple in principle, but particularly on the softwood line, installation
may be very difficult due to space constraints. On the softwood side, it may be
necessary to install a second medium consistency pump due to a potential
remote location of the new first stage oxygen reactor.
The capital cost for implementation of this technology is estimated to be $1.5-2
million for the hardwood line, and $2-3 million for the softwood side.
From an operating standpoint, this conversion will result in the following changes:
Increased steam use
Increased oxygen and alkali use
Increased power use (pump and mixers)
Increased maintenance costs
Lower kappa to the bleach plant
Reduced bleach chemical costs
Reduced environmental impact
Increased solids load to recovery
There are a number of commercial installations of two stage oxygen systems in
North America on hardwood and softwood pulp. Generally, it is difficult to justify
the second oxygen reactor on hardwood pulp, as the incremental kappa number
reduction is quite small. This makes this technology commercially demonstrated,
and operating mills can be visited to verify applicability to the Canton Mill.
Irving Pulp and Paper has Retrofitted a single stage oxygen delignification
system to a two stage system. One stage system operated at a 43%
delignification rate on softwood with an incoming kappa number of 32. The
upgraded two stage system was able to achieve 63% delignification without an
impact on final bleached pulp quality.
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VGUI
m
-,
o'
Retrofit of a Single Stage Oxygen Delignification System to a Two Stage System
z
° 60 Min.
N Reactor
0
0
Discharger
Pulp in 10-30 Min.
Pre- Reactor)
NaOH,
LP Steam
I I NaOH
Q2
02
Steam
Med % HI-ShearrM I HI-ShearrM
Mixer I Mixer Blowtank
MP Steam
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VIGIN
Conversion of Extraction Stages to EoP
The use of a small quantity of hydrogen peroxide in the first oxidative extraction
stage has been well established in the industry to reduce chlorine dioxide use
and overall bleach chemical cost. We believe it has good potential for low cost
retrofit of this stage to reduce color at the Canton mill.
Hardwood Pine
Current
Kappa to Bleach Plant —
Kappa Factor (KF) _
Potential KF future 0.18 0.18
Chemical Use Impact
H2O2/ton 10 10
Repl. Ratio #act.Cl/#H2O2 1.2 1.8
Reduced CI02, #/t 4.6 6.8
Added NaOH +10#/t +10#/t
Added 02 +0#/t +0#/t
Added MgSO4 2-4#/t 2-4#/t
Temperature 175 OF 175 OF
Color
Current#/Day 8,220 8,160
Reduction, % 31% 25%
Reduction, #/Day -2548 -2040
Impact
Water Use N/C N/C
Effluent Flow N/C N/C
AOX kg/t -0.3 -0.36
Toxicity decrease decrease
Temperature increase increase
Pulp Quality/viscosity N/C N/C
Commercial Experience Moderate Moderate
Operating Cost Increase Increase
Capital Cost EoP Moderate/Low Moderate/Low
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Conversion of Extraction Stapes to PHT
The use of hydrogen peroxide in the first oxidative extraction stage, operated at
high temperature has been well established in the industry to increase brightness
capabilities in short sequence bleach plants, reduce chlorine dioxide use and
AOX in the effluent. Although, as far as we know, this technology has not to date
been deployed for color reduction, we believe it has good potential for moderate
cost retrofit of this stage to reduce color at the Canton mill.
Hardwood Pine
Current
Kappa to Bleach Plant _
Kappa Factor (KF) _
Potential KF future 0.15 0.15
Chemical Use Impact
H2O2/ton 14 14
Repl. Ratio #act.Cl/#H2O2 2.3 2.8
Added NaOH +12#/t +12#/t
Added 02 +0#/t +0#/t
Added MgSO4 2-4#/t 2-4#/t
Temperature 195 OF 195 OF
Color
Current#/Day 8,220 8,160
Reduction, % 43% 38%
Reduction, #/Day -3534 -3100
Impact
Water Use N/C N/C
Effluent Flow N/C N/C
AOX kg/t -0.3 -0.36
Toxicity decrease decrease
Temperature increase increase
Pulp Quality/viscosity N/C N/C
Commercial Experience Moderate Moderate
Operating Cost Increase Increase
Capital Cost (PO /PHT Moderate Moderate
Although this technology has not yet been applied for color reduction, there is
substantial laboratory data that supports a significant decrease in color using this
technology. Most data is on non-oxygen pulps, but shows reduction in total
bleach effluent color in the range of 25 and 45% for softwood and hardwood
pulps, respectively for the use of 10-20 #H2O2/ton addition. Limited data on
oxygen pulps suggests a reduction of greater than 35% can be achieved with this
technology. One study shows the conversion of an Eop to a PHT stage on
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VGBI
softwood pulp resulting in a total bleach color reduction of 60% when the
peroxide charge is increased form 12 #/t to 24 #/t (+12 #/t). For Canton, we
suggest the total peroxide use of 14 #/t. This will allow a significant reduction in
kappa factor in the Di stage, thus reducing D, stage color significantly.
There are two technologies that can be implemented to achieve the benefits of
increased peroxide use in the Eo stage. There is significant commercial
experience with the use of the (PO) stage technology. This technology is very
similar to an oxygen delignification stage, where the pulp is treated in a
pressurized upflow tower for 1-3 hours at relatively high temperature (>900C). An
alternative technology has been developed, in which high temperature is applied
only in the first 10-20 minutes, after which, the pulp is discharged to an
atmospheric retention tower. This concept is shown on the next page.
The implementation of a (PO) stage in the Canton mill will be a relatively high
capital cost project, and will be difficult, especially on the hardwood side due to
the space requirements for the (PO) reactor. For simplicity, we will describe an
overview of the system changes required to implement PHT technology at the
Canton mill. It should be recognized, however, that (PO) technology is currently
operating on hardwood, softwood, and eucalyptus pulps in mills today, while
there is no "true" PHT stage in operation to date. All installations that have the
mechanical configuration of the PHT technology, are unable to operate at the
specified time, temperature, and/or pressure.
The implementation of the PHT technology requires the following steps:
1. Upgrade or replacement of the medium consistency pump feeding
the stage
2. Addition of steam sparger and/or steam mixer to add steam to the
pulp to achieve a temperature of 195-205°F (90-951C), along with
piping and controls for addition of medium pressure steam to this
stage
3. Replacement of the current upflow tube with a pressurized upflow
tube designed for 10-20- minutes retention time
4. Upgrade or installation of new magnesium preparation and delivery
system
5. Upgrade or installation of new hydrogen peroxide delivery system
6. Upgrade or maintenance of Eo mixer
The implementation of the PHT technology in the softwood line should be less
complex due to the available space around the existing Eo tower; however, the
opposite is true for the hardwood line. It is likely that the new upflow tube for the
hardwood line would need to be constructed in place, which will dramatically
increase the cost of the installation. In either case, we anticipate the cost of the
Pubic Version - Nov 2006 CONFIDENTIAL

VGnt
conversion to PHT technology may be in the range of $1-2 million, while the
conversion to (PO) technology is likely closer to $2-3 million.
This technology is one that could be tested at mill scale at the Canton mill using
existing equipment, even with its limitation in retention time. For such a trial to be
valid, a means to add magnesium, sufficient quantities of hydrogen peroxide, and
a means to increase the temperature to 195-205OF is necessary. Laboratory
studies could then be used to predict the benefit of increased retention time in
the upflow tube.
Pubic Version - Nov 2006 CONFIDENTIAL

] V
y General Schematic of the Eop and PHT Stage
0
z
0
N
O
O
O
Upflow Section:
Pressurized: 4 bar
Temperature: 90 - 130°C
Downflow Section:
Atmospheric Condition
Temperature: 95 - 98°C
Pump
Mixer
CONFIDENTIAL za

VGU/
Appendices
Pubic Version - Nov 2006
CONFIDENTIAL

APPENDIX 1. Confidentiality Agreement
Pubic Version - Nov 2006
CONFIDENTIAL "-

fYGBI
AGREEMENT FOR THE DISCLOSURE OF
CONFIDENTIAL INFORMATION TO PARTIES
This Agreement is entered into effective this 9th day of May, 2006
("Effective Date") between GL&V USA Inc having a mailing address of 141 Burke
Street, Nashua, NH 03060 ("GL&V"), Liebergott & Associates having a mailing
address of 5825 Shalom Avenue, Suite 802, Cote St. Luc, Quebec, Canada H4W
3A5 ("NL"); (also individually and collectively called the Party or Party's) and Blue
Ridge Paper Products, Inc., having a mailing address of Main Street, PO Box 4000,
Canton, NC 28716 ("Discloser").
WHEREAS, Discloser is interested in disclosing certain of its confidential
and proprietary information relating to process design and mill operating and
financial data (collectively "Technology") to the Party's for the purpose(s) stated
herein; and the Party's desire to keep secret and proprietary to itself the content
of such disclosures; and
WHEREAS, the Party's desire to receive Discloser's confidential and
proprietary information relating to a proposed Bleach Environmental and Process
Evaluation Report;
NOW, THEREFORE, for and in consideration of the disclosure to the
Parties by Discloser of Discloser's confidential and proprietary information, the
parties agree as follows:
1. Discloser's "Technology" shall be defined as Blue Ridge Paper's
("Discloser's") process design and mill operating and financial data. Discloser
shall make disclosure of proprietary and confidential information "Confidential
Information" to the Parry's in a manner permitting the most appropriate and
certain communication, i.e., orally, in writing, or partly orally and in writing.
"Confidential Information" shall mean any and all data and information contained
in any tangible or intangible medium of expression as made available by the
Discloser to the Party's pursuant to this Agreement, and shall include, but not be
limited to, ideas, concepts, development plans for new or improved products or
processes, data, formulae, techniques, flow sheets, designs, sketches, know-
Pubic Version - Nov 2006 CONFIDENTIAL

how, photographs, plans, drawings, specifications, samples, test specimens,
reports, customer lists, price lists, findings, studies, computer programs and
technical documentation, trade secrets, diagrams, or inventions; and all
information pertaining thereto and/or developed there from.
2. Upon Discloser's request, the Party's agree to (a) return all Confidential
Information to Discloser, or (b) destroy all such Confidential Information and
certify such destruction to the Discloser by an appropriate officer of each of the
Respective Party's.
3. The Party's hereby covenant and agree that they (a) will not knowingly
(either directly or indirectly) reveal or disclose Confidential Information to any
other person, partnership, association, or corporation; (b) will treat all
Confidential Information as a trade secret confidential and proprietary in nature to
the Discloser; and (c) will safeguard the secrecy of such Confidential Information
by following procedures at least as stringent as those used in safeguarding its
own valuable confidential information and trade secrets.
4. The Party's covenant and agree not to use, sell, lease, license, compete
with or otherwise commercially use Confidential Information or distribute
information regarding the relationship of the parties, either directly or indirectly,
unless express, prior written authorization is obtained from the Discloser signed by
an appropriate officer.
5. To maintain the confidentiality attaching to Confidential Information, the
Party's shall (a) limit disclosure of Confidential Information only to those of its
employees (i) who have a reasonable need to know and use such Confidential
Information in furtherance of this Agreement; (ii) who have been informed of the
confidential nature of the Confidential Information of the Discloser and of the
obligations of each Party in respect thereof; and (iii) who have executed
agreements with their respective Party obligating their employees to maintain the
confidentiality of the Confidential Information to at least the same extent as that
required by this Agreement; (b) not make copies of Confidential Information
Pubic Version - Nov 2006
CONFIDENTIAL '`'%

without the prior written approval of the Discloser, except to the extent necessary
in furtherance of this Agreement; (c) not use, reproduce, transform or store any
Confidential Information in an externally accessible computer or electronic
information retrieval system transmitted in any form or by any means whatsoever
outside of its usual place of business; (d) not permit or allow the Confidential
Information to be used or accessed by or otherwise made available to any
consultant or contractor of each Party without the prior written permission of the
Discloser; and (e) not make any changes, modifications or enhancements to the
Confidential Information, or create any derivative work from such Confidential
Information, except as agreed to in writing with the Discloser and which changes,
modifications, enhancements and derivative work would be considered as work
made for hire and as Confidential Information also owned by the respective Party
hereunder.
6. Nothing hereinabove contained shall deprive the Party's of the right to use
or disclose any information (a) which is, at the time of disclosure, known to the
trade or the public; (b) which becomes at a date later than the time of disclosure
known to the trade or the public through no fault of a Party and then only after
said later date; (c) which is possessed by a Party before receipt thereof from the
Discloser; (d) which is disclosed to the Party's in good faith by a third party who
has an independent right to such information; or (e) which is required to be
disclosed by the Party's pursuant to an order of a court of competent jurisdiction
or other governmental agency having the power to order such disclosure,
provided the Party's uses its best efforts to provide timely notice to the Discloser
of such order in order to permit the Discloser an opportunity to contest such
order.
7. Confidential Information disclosed under this Agreement shall not be
deemed to be within the foregoing exceptions merely because such information is
embraced by more general information in the public domain or in the Party's
possession. In addition, any combination of features shall not be deemed to fall
Pubic Version - Nov 2006 CONFIDENTIAL ""

within the foregoing exceptions merely because individual features are in the public
domain or in the Party's possession, but only if the combination itself and its
principle of operation are in the public domain or in the Party's possession.
8. Nothing hereinabove shall be construed as granting or implying any right or
license under any Letters Patent or any right to use any invention covered thereby.
Nothing hereinabove shall be construed as granting or implying any right or duty to
purchase any material, process or service. The obligations incurred in this
Agreement shall terminate five (5) after the date of last disclosure of Confidential
Information hereunder.
9. The Party's hereby agree that no secret or confidential information
proprietary to either Party will be disclosed to the Discloser as a result of this
Agreement, except as may be agreed upon in a separate agreement signed by an
officer of the Discloser.
10. Neither the Discloser nor any of its officers, directors, employees,
affiliates, agents, or representatives ("Discloser Representatives") has made or
makes any representation or warranty as to the accuracy or completeness of the
Confidential Information. The Party's agree that neither the Discloser nor the
Discloser's representatives shall have any liability to it or to any of its officers,
directors, affiliates, partners, employees, agents, or representatives (either
"Party's Representatives") resulting from the provision or use of the Confidential
Information.
11. The Party's understand and agree that the Discloser is entitled, in the
event of any breach of this Agreement, to obtain a restraining order and/or
injunction from any competent court of equity to enjoin and restrain the Party's
and their employees or agents from any disclosure of Confidential Information of
the Discloser. Such equitable remedies shall be in addition to and not in lieu of
any damages to which the Party's may be entitled by law.
Pubic Version - Nov 2006 CONFIDENTIAL

12. This Agreement cannot be assigned by either party hereto without the other
party's written permission, which shall not be unreasonably withheld, except to a
purchase of a party's business to which this Agreement relates.
13. This Agreement sets forth the entire agreement between the parties
relating to the subject matter hereof and can only be amended or modified by an
amendment in writing signed by both parties. Failure of either party to seek a
remedy for the breach of this Agreement by the other shall not constitute a
waiver of the right of such party with respect to the same or any subsequent
breach by the other party. If any provisions of this Agreement shall be held
unenforceable, such holding shall not affect the enforceability of any other
provisions of this Agreement. This Agreement is entered into in contemplation of
and shall be construed in accordance with the laws of the State of New York,
excluding its conflicts of law and choice of law statutes. The place of venue shall
be New York City, New York.
IN WITNESS WHEREOF, the parties hereto have caused this
Agreement to be executed by their duly authorized officers.
GLBV USA Inc. Blue Ridge Paper Products, Inc.
("Party") ("Discloser")
By: By:
(Signature) (Signature)
Name: Name:
(Type or Print) (Type or Print)
Title: Title:
Date: Date:
Liebergott &Associates Consulting, Inc.
("Party")
By:
(Signature)
Name:
(Type or Print
Title:
Date:
Pubic Version - Nov 2006 CONFIDENTIAL

VGIN
APPENDIX 2. Study Participant Resumes
Pubic Version - Nov 2006 CONFIDENTIAL

� GIN
NORMAN LIEBERGOTT Ph.D.
Norman Liebergott was formerly a Senior Scientist at the Pulp and Paper Research
Institute of Canada (Paprican). He is currently the President of Liebergott & Associates
Consulting Inc. as well as Special Consultant to many pulp and paper companies and
environmental groups globally. Dr. Liebergott is also was an adjunct professor of the
Department of Chemical Engineering at McGill University, Montreal, Quebec, teaching in
the Master program in bleaching of chemical wood pulps and non wood pulps, as well
as mechanical and secondary fibre pulps.
During his 51 years of service to the pulp and paper industry Norman Liebergott has
distinguished himself as a leader in pulp bleaching processes. His contributions include
instrumental work using oxygen, alkali and peroxide to decrease and/or eliminate the
use of chlorine and chlorine-containing chemicals in the bleaching sequence of chemical
pulps. His work in this area has centred on developing, implementing, and promoting the
oxygen-alkali delignification, activated oxygen delignification, oxygen-peroxide re-
enforcement of the alkali extraction stage and ozone and per-acid delignification and
oxidative bleaching processes. He also has been conducting research on sulphite, kraft,
kraft AQ-polysulphide pulping. Dr. Liebergott has developed bleaching techniques using
reducing and oxidizing chemicals to enhance the pulp properties of mechanical and
secondary fibre pulps.
Norman Liebergott has been involved with over 200 different mills in assisting them to
better control the bleaching process and to meet environmental regulations. His
research in the area of pulp bleaching processes and environmental control has earned
him 19 patents and he has published over 100 scientific articles. He has reported on his
work at over 150 scientific meetings and has been invited to numerous mills in Canada,
United States, South Africa, Chile, Argentina, Brazil, Russia and China to provide
technical assistance.
Over the past several years he has been contracted by various mills to audit the
processes by undertaking an evaluation of the bleach plant lines, chemical usage and
procedures used by these mills. In addition he has updated the knowledge of bleach
plant operators by providing in-house bleaching technology training
(Note: Worked as a consultant at over 200 mills, research centers and universities
issuing over 175 confidential reports)
Dr. Liebergott received a Diploma in Textile Chemistry, a B.Sc and a Ph.D. in Chemistry
from Sir George Williams University Montreal Quebec Canada.
Membership and Positions held in organizations Related to the Pulp and Paper Industry
Norman Liebergott has been a member of the member of the Pulp and Paper Technical
Association of Canada (PAPTAC) since 1957 as well as Secretary of the Sulphite
Committee, a member of the Alkaline Pulping Committee and in 1977 was the founding
Chairman of the Bleaching Technology Committee. In 1993 he was made a Honorary
Life Member of the Committee and is still an active member. He has been the Course
Leader for the PAPTECH Pulp Bleaching Courses since 1991 and has also served as
Pubic Version - Nov 2006
CONFIDENTIAL

course leader for the one day Seminars on Washing and Process control. He served as
Chairman of the International pulp bleaching conference in 1976 and again in 1982. In
February of 2005 Dr. Liebergott was awarded Honorary Life Membership in PAPTAC for
outstanding service to the industry in the area of chemical and mechanical pulp
bleaching.
TAPPI INVOLVEMENT.
Norman Liebergott is a senior member of the Steering Committee, and a member of the
Bleaching Committee as well as Chairman of the Publications Committee.
International Ozone Institute (101)
Dr. Liebergott was a founding Director of the International Ozone Association (now the
101) and also a member of the American Chemical Society
AWARDS
CPPA &TS I.H. Weldon Medals (in 1968 and 1971)
CPPA&TS Douglas Jones Environmental (1991)Award
CPPA & TS Best Technical Paper (other than a mill presentation) Western Branch
(1989)
PAPTAC Honorary Life Member of the Bleaching Committee (1993)
1 PAPTAC Honorary Life Member of the Association (2005)
TAPPI Russell 0. Blosser Best Paper Award from the Environmental Conferences
of the Technical Association of the pulp and paper industry.
TAPPI Pulp Manufacturers Division Award and the CFC Ritter prize (1986)
TAPPI TAPPI FELLOW (1991)
TAPPI Six Awards of Recognition for Contribution as an Instructor in bleaching
Seminars
South African Forest Products International Award for Excellence in Bleaching
PAPRICAN'S President's Citation Award.
Over the past 28 years Norman Liebergott has served the community as a school board
commissioner and has served as either chairman of the Council of Commissioners or
the Executive Committee of the Laval, North Island and Laurenval School Boards. In
appreciation of his many years of devoted service for his support for the staff, and for his
value for public education and the love of children, he was recently honoured with the
Laurenval School Boards "Distinguished Service Awards" in the field of public education.
1
Pubic Version - Nov 2006 CONFIDENTIAL 134

VGnt
Lewis D. Shackford
Vice President
GL&V USA Inc.
Education
B.S. Chemical Engineering with minor in Paper Engineer, Magna Cum Laude
University of Lowell (formerly Lowell Technological Institute), Lowell, MA
Professional Engineering
Licensed Professional Engineer, State of New Hampshire (#5823)
Affiliations
TAPPI Member(Alkaline Pulping Committee since 1973, Brown Stock Washing
Subcommittee member since 1981; Pulp Manufacture Division Officer since 1996,
currently Chairman)
CPPA, APPITA, ABTCP, AIChE, NSPE
Summary of Experience
Experienced in performing tasks, and/or leading engineers or scientists, as individuals or
as teams, towards goals to improve organizations' financial results. Nearly 30 years'
experience in pulp mill fiberline systems design and operation, with particular expertise
in the areas of pulping, washing, delignification, bleaching, industry and regulatory
trends, and emerging process technology. Strong background in process technology
and development, benefits analysis for conventional or advanced machinery and
process technology. Negotiation of agreements for technical and business cooperation
and management of agreements with alliance partners has been a key responsibility.
Extensive experience in commercialization of new product and process technology, and
process risk management. Extensive experience in preparing and presenting technical
reports on process design and optimization, technical and business process training,
and technical papers for industry conferences. Numerous mill process start-ups and
optimization efforts have been undertaken with successful results. General knowledge
in woodyard operations, recycled fiber, stock preparation, power/recovery and effluent
treatment.
Typical Project Experiences
Leadership of machine and process design for an innovative pulp washer, supervision of
installation, and leadership of the start-up and optimization efforts (Southeast U.S. mill).
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CONFIDENTIAL ' j�

VGBI
Evaluation of the operations of a multiple line kraft mill (several brown stock washing
lines and bleaching lines), and development and presentation of strategy to optimize
financial results in the mill (Southeast U.S. mill).
Participation in high and medium consistency ozone bleaches pilot plants and
commercial installations' start-up and optimization (six occasions U.S. and Canada).
Start-up and optimization of the first integrated medium consistency oxygen
delignification system in North America (Mid-West U.S. mill).
Optimization of two stage medium consistency oxygen delignification system (B.C.,
Canada mill).
Development of recommended technical strategy for achieving compliance with USEPA
Cluster Rule (several U.S. mills).
Optimization of brown stock washing bleaching (plants and unit operations) in numerous
American mills.
Other Experience and Contributions
Continuing Education — 'The Professional Manager" and "Managing Business
Strategies"— Indiana Executive Program, Bloomington, Indiana.
Numerous publications and presentations in the fields of pulp cooking and washing, ECF
and TCF bleaching, and issues regarding the closure of mill filtrate cycles to approach
TEF operation. List available on request.
Patents -4 U.S. issued, 7 pending (32 global issued or pending)
TAPPI Pulp Manufacture Division Leadership and Service Award Recipient, 1995.
TAPPI Short Course Contributor since 1979
Brown Stock Short Course (Chairman and Instructor), Bleach Plant Operations
Short Course (Instructor), Improving Screening and Cleaning Efficiencies Short
Course, Oxygen Delignification Symposium (Paper Presenter), Mixing
Symposium
Pubic Version - Nov 2006
CONFIDENTIAL

VGB/
Umit S. Sezgi
Process Manager
Technology
GL&V USA Inc.
Education
1991-1994 Doctor of Philosophy in Wood and Paper Science, Minor in Industrial
Process Simulation, North Carolina State University, Raleigh, NC.
1988-1991 Master of Science in Wood and Paper Science, Minor in Operations
Research, North Carolina State University, Raleigh, NC.
1982-1987 Bachelor of Science in Chemical Engineering, Middle East Technical
University, Ankara, Turkey.
Summary of Experience:
- Expertise in Chemical Pulping, Pulp Washing and Bleaching process.
- Pulp and Paper Process Simulation.
Work History
1994-1997 Senior Research Engineer, Beloit Research and Development Center,
Pittsfield, MA
Responsibilities: Directing technical customer services and research activities in
chemical pulping and bleaching area. Designing and building full scale pulping pilot plant
equipment, supervising technicians. Supporting marketing and projects group with sales
presentations, start-ups, and performance tests in chemical pulping and bleaching area.
Contribute to research activities with Research Alliances and publish technical papers.
1997-Present Process Manager, Technology, GL&V
Responsibilities: Process management and marketing of chemical pulping equipment.
Perform process evaluation for existing fiberlines from Cooking to Bleaching and
determine the required modifications to system and/or to individual equipments in order
to meet customer's requirements for final product. Identify the type and optimum
configuration of equipment for new fiberlines. Join equipment and system start-up,
perform process optimization and trouble shooting, attend individual equipment or
system performance trials.
Publications
- 17 technical publications written and presented at several journals and conferences
worldwide.
Activities and Honors
Awarded full scholarship towards M.S., and Ph.D. studies at North Carolina State
University.
Process and Research Advisory Committee Member, Institute of Paper Science and
Technology, Atlanta, GA.
Member, Process Simulation Committee, Technical Association of Pulp and paper
Industry (TAPPI).
Pubic Version - Nov 2006
CONFIDENTIAL

APPENDIX 3. Technical Overview Of Blue Ridge Paper Products Inc
Pubic Version - Nov 2006 CONFIDENTIAL

' Washer/Decker
02 Reactor
Knotting Pre-02 Washers Post 02 Washer Brown
Screening Stock
-Densi
Stora e
Pre-Bleach
Washer D1 Washer Eo Washer D2 Washer
Bleached
D1 Eo D2 ffi-Densi
Storage
IA IA 4 C$�
CONFIDENTIAL ^gg

:s
CD
51 HARDWOOD FIBERLINE SCHEMATIC
Pre Oxygen Washers 02 Reactor
Past Oxygen Washers
oZ
N
O
Knotting
a
Q
Blow Screening
Tank
C5�
Pre-Bleach
Washer D1 Washer Eo Washer D2 Washer
DI Eo D2
CONFIDENTIAL 140

VGBI
APPENDIX 4. Washing Definitions.
WASH Appendix
Waak Ddiu dm
SAaa+x
Lu
Cu
L„
Cq
Pulp In L- w"ImIpalpout
w
Lt, Ch
C„
Film"
Wask Liquor Ratio - R „ ". L,.__.. Liquor Flow
L,,, Ton Gran Dried Pulp
Ligvw Vf,cW t Ri io = W -
Ln C r Otesolwd S6adt C.eaYaMri/ien
Dilution Faun or Fatten Wa* . DF - Lu . Ln
DiVilto m a Ratio - DR. - CK . Ca,
Cp - ell
Total Solids Carryover = C,,, 0 L„
Washing Yield - C� L x_i (7f C,; - 0)
Nardam Washing Efflciancy New
t4 M)
E - eaCu
LL ln(R}
Lft
Pubic Version - Nov 2006 CONFIDENTIAL

■
r"
ncasi
NATIONAL COUNCIL FOR AIR AND STREAM IMPROVEMENT
REVIEW OF COLOR CONTROL
TECHNOLOGIES AND THEIR
APPLICABILITY TO MODERN
1 KRAFT PULP MILL WASTEWATER
TECHNICAL BULLETIN NO. 919
AUGUST 2006
by
Eva Mannisto
EKONO, Inc.
Bellevue,Washington
L�

Note regarding Blue Ridge Paper Products
September 2006
The Blue Ridge Paper Products Canton Mill is Mill A
in this NCASI report. Blue Ridge Paper is one of the five
mills that funded this study through NCASI. The five mills
discussed in the study are leaders for wastewater effluent
color prevention and control in the pulp and paper industry.
The report was included as supporting information for the May 2006
application to renew the Blue Ridge Paper NPDES permit. The
report has two purposes:
• update the current"state of art"for Kraft pulp mill effluent
color prevention and control
• benchmark performance and reasons for differences
between the leading color performing mills.
�1

�i
Acknowledgments
The preparation of this report was made possible through funding by five U.S.pulp mills. The report was prepared
by Eva Mannisto and Sean Smith of EKONO,Inc,with input by NCASI staff and representatives of the five mills.A
considerable amount of the previously unpublished information incorporated into this report,specifically,that related
to mill study of color reduction alternatives,was provided by the five mills involved in the study. Ms.Anna Aviza is
acknowledged for her efforts to convert the EKONO report into NCASI technical bulletin format.
For more information about this research,contact:
Paul Wiegaud
Vice President,Water Quality
NCASI
P.O.Box 13318
Research Triangle Park,NC 27709-3 3 1 8
[phone]
[e-mail]
For information about NCASI publications,contact:
Publications Coordinator
NCASI
P.O.Box 13318
Research Triangle Park,NC 27709-3318
[phone]
[e-mail]
National Council for Air and Stream Improvement,Inc.(NCASI). 2006. Review ojcolor control technologies and
their applicability to modern krajt pulp mill wastewater. Technical Bulletin No.919. Research Triangle Park,N.C.:
National Council for Air and Stream Improvement,Inc.
©2006 by the National Council for Air and Stream Improvement,Inc.

ncasi
serving the environmental research needs of the forest products industry since 1943
PRESIDENT'S NOTE
Color in wastewaters from wood pulping and pulp processing operations,and techniques for
minimizing this color,have been studied since the earliest days of wastewater management. Color
loads in chemical pulp mill effluents have decreased in recent years due to increased vigilance in
minimizing pulping liquor losses and as chlorine dioxide bleaching has replaced chlorine bleaching.
However,site-specific circumstances associated with small flow or unique clarity of receiving waters
at a few mills has prompted continuing efforts to investigate in-process and end-of-pipe treatment
technologies that may offer further, cost-effective reductions of color in treated effluents.
Periodic summaries of effluent color reduction techniques have been prepared during the last
several decades. For example,in 1984,NCASI prepared a series of reports titled Effluent Color
Reduction Technology Review and Identification oflnformation Needs,and in 1995 a Pennsylvania
State University Masters Thesis by James Baird provided an updated summary of color control
techniques.The attached report was prompted by the recognition that research and implementation
of in-process and end-of-pipe color reduction techniques have continued during the last decade and
a comprehensive update summarizing these studies and experiences should be prepared. Five mills
ij provided funding for the generation of the report which was prepared under NCASI contract by Eva
Mannisto and Sean Smith of EKONO,Inc. in Bellevue,Washington. The report includes not only
a summary of current literature on color control techniques,but also a review of mill-specific color
loads from various process sources and experiences with investigation and implementation of color
reduction alternatives.
The availability of this report to the broad NCASI membership is courtesy of the five mills that
funded its preparation.
Ronald A.Yeske
August2006
National Council for Air and Stream Improvement

■
ncasi
au service de la recherche environnementale pour Pindustrie foresti6re depuis 1943
MOT DU PRESIDENT
La couleur des eaux us6es du proc6d6 de mise en pate du bois et des op6rations de traitement de la
pate ainsi que les techniques pour r6duire cette couleur font 1'objet d'6tudes depuis qu'on s'int6resse
A la question de la gestion des eaux us6es. Depuis quelques ann6es,on constate une diminution de
la charge des composes responsables de la couleur en raison d'une plus grande attention apport6e
A la minimisation des pertes de liqueur de mise en pate et du remplacement du chlore par le dioxyde
chlore dans le blanchiment des pates. Cependant,les conditions particulieres de quelques fabriques
associ6es a des eaux rdceptrices qui ont un faible debit ou qui font 1'objet d'exigences sp6ciales en
mati6re de limpidit6 ont incit6 les chercheurs a poursuivre leurs efforts en mati6re de methodes de
traitement en amont on en aval du proc6d6 qui pourraient entrainer une reduction additionnelle de la
couleur des effluents trait6s et ce, d'une mani6re 6conomique.
An tours des derrieres ddcennies,un certain nombre de rapports sur les techniques de reduction de
la couleur ont 6t6 publi6s de fagon p6riodique. Par exemple,NCASI publiait en 1984 une s6rie de
rapports intitul6e Effluent Color Reduction Technology Review and Identification oflnformation
Needs et, en 1995,James Baird de l'Universit6 de 1'Atat de la Pennsylvania d6posait sa these de
I maitrise qui rdsumait les connaissances du temps en mati6re de techniques de contr6le de la couleur.
NCASI a command6 le present rapport pour montrer que la recherche sur les techniques de reduction
de la couleur en amont et en aval du proc6d6 et la mise en oeuvre de ces techniques se sont
poursuivies an tours de la derniere d6cennie et pour r6sumer les connaissances acquises par ces
Etudes et ces exp6riences. Cinq fabriques ont financ6 la production du present rapport redigd par
Eva Mannisto et Sean Smith de la fume EKONO,Inc. de Bellevue,Washington,en vertu d'un
contrat avec NCASI. Le rapport contient non seulement un r6surn6 des comtaissances actuelles en
matiere de techniques de controle de la couleur,mais examine aussi la charge des composes qui sont
responsables de la couleur et qui sont 6mis par diverses sources du proc6d6 de fabriques sp6ciftques
de m@me que Les expdriences de recherche et de mise en oeuvre de techniques de remplacement pour
diminuer la couleur.
La distribution du present rapport a 1'ensemble des membres de NCASI est une courtoisie des cinq
fabriques
qui en ont financ6 sa pr6paration.
Ronald A. Yeske
Aofrt 2006
National Council for Air and Stream Improvement

REVIEW OF COLOR CONTROL TECHNOLOGIES AND THEIR APPLICABILITY
TO MODERN KRAFT PULP MILL WASTEWATER
TECHNICAL BULLETIN NO. 919
AUGUST 2006
ABSTRACT
The color of treated effluents from kraft pulp mills has decreased considerably in recent years owing
to increased efforts to reduce losses of pulping liquors and the replacement of chlorine bleaching with
chlorine dioxide. For a few mills,however,the unique characteristics of receiving waters have
prompted ongoing efforts to investigate techniques for achieving additional reductions in effluent
color.This report provides a review of recently investigated and currently employed color reduction
techniques, focusing primarily on information made available since 1995,when a similar review was
last prepared.
The report summarizes some 27 color reduction technologies including in-process measures to
minimize color generation and/or loss to wastewaters,and treatment of wastewaters to remove color.
In addition,a mill-specific review of color sources,in-process loss control measures,and experiences
with the investigation and implementation of color practices is provided for several low color
discharge mills. Successful and unsuccessful efforts to reduce effluent color at these mills are
summarized.
KEYWORDS
best management practices,black liquor,bleaching,color reduction,effluent quality,loss control,
pulping,treatment,wastewater
RELATED NCASI PUBLICATIONS
Technical Bulletin No. 803 (May 2000). An update ofprocedures for the measurement of color in
pulp mill wastewaters.
Technical Bulletin No. 630(January 1992). Effects of chlorine dioxide substitution on bleach plant
effluent BOD and color.
Technical Bulletin No.494(January 1986). A laboratory study ofpre-biological treatment color
reduction technology effectiveness for selected kraft streams.
National Council for Air and Stream Improvement

REVUE DES TECHNIQUES DE CONTR6LE DE LA COULEUR
ET APPLICABILITE AUX EAUX USEES DES FABRIQUES MODERNES
DE PATE IQ2AFT
BULLETIN TECHNIQUE NO. 919
AOUT 2006
RESUME
Depuis quelques ann6es, on constate une diminution consid6rable de Is couleur des effluents traites
de fabriques de pate kraft on raison d'efforts accrus pour r6duire les pertes de liqueur de mise en pate
et du remplacement du chlore par le dioxyde de chlore. Cependant,pour certaines fabriques, les
caract6ristiques uniques de leurs eaux r6ceptrices ont incit6 les chercheurs A poursuivre leurs efforts
pour trouver des techniques qui r6duiraient davantage Is couleur des effluents. Le pr6sent rapport
passe en revue les techniques de reduction de la couleur qui ont fait 1'objet de travaux de recherche
r6cents et qui sont pr6sentement en usage et met Paccent principalement sur 1'information existante
depuis 1995,c'est-A-dire depuis Is derni6re revue du meme type.
Le rapport r6sume les 27 techniques de reduction de la couleur,notamment les mesures en amont
du proc6d6 pour minimiser Is formation de Is couleur,les pertes d'eaux color6es dans les eaux usdes,
ou les deux,et les m6thodes de traitement des eaux us6es servant A 61iminer la couleur. De plus,le
rapport examine les sources qui sont responsables de la couleur dans certaines fabriques,passe en
revue les mesures de contr6le des pertes en amont du proced6 et decrit les travaux de recherche sur
Ies m6thodes de reduction de la couleur ainsi que la mise en o:uvre de ces m6thodes daps plusieurs
fabriques qui ont des effluents peu color6s. Le rapport d6crit 6galement les travaux qui ont port6
fruit dans ces fabriques ainsi que ceux qui ont 6t6 vains.
MOTS CLES
blanchiment,contr6le des pertes, eaux us6es,liqueur noire,meilleures pratiques de gestion,mise en
pate, qualitd de 1'effluent,reduction de la couleur,traitement
AUTRES PUBLICATIONS DE NCASI DANS CE DOMAINE
Bulletin technique No. 803 (mai 2000). An update ofprocedures for the measurement of color in
pulp mill wastewaters.
Bulletin technique No. 630(janvier 1992). Effects of chlorine dioxide substitution on bleach plant
effluent BOD and color.
Bulletin technique No.494(janvier 1986). A laboratory study ofpre-biological treatment color
reduction technology effectiveness for selected kraft streams.
National Council for Air and Stream Improvement

TABLE OF CONTENTS
1.0 INTRODUCTION........................................................................................................................ 1
1.1 Background......................................................................................................................... 1
1.2 Measurement of Color........................................................................................................ I
2.0 TASK I: COLOR REDUCTION TECHNOLOGIES...................................................................2
2.1 Wood Species—Impact On Color......................................................................................2
2.2 Kappa Number Reduction...................................................................................................3
2.3 Oxygen Delignification.......................................................................................................4
3.0 BLACK LIQUOR LOSS CONTROL..........................................................................................5
3.1 Improved Brown Stock Washing........................................................................................6
3.2 Reduction of Other Regular Black Liquor Losses..............................................................8
4.0 BLEACHING.............................................................................................................................11
4.1 Chlorine Dioxide Bleaching............................................................................................. 11
4.2 Hydrolysis Treatment for Removal of Hexenuronic Acids.............................................. 14
�J 4.3 Ozone Use in Bleaching.................................................................................................... 16
4.4 Peroxide in Bleaching.......................................................................................................21
4.5 Peracid Bleaching.............................................................................................................23
5.0 COLOR MONITORING............................................................................................................25
6.0 RECOVERY OF COLORED WASTEWATERS......................................................................26
6.1 Black Liquor Spill Recovery............................................................................................26
6.2 Bleach Plant Effluent Recovery........................................................................................33
7.0 COLOR REMOVAL—SEPARATION PROCESSES..............................................................54
7.1 Membrane Technologies...................................................................................................54
7.2 Ion Exchange....................................................................................................................64
7.3 Activated Carbon and Activated Petroleum Coke Adsorption.........................................65
7.4 Electrodialysis(ED)and Electrodialysis Reversal(EDR)................................................68
8.0 COLOR REMOVAL--CHEMICAL PROCESSES..................................................................69
8.1 Lime Precipitation.............................................................................................................69
8.2 Alum Precipitation............................................................................................................70
8.3 Iron Precipitation..............................................................................................................70
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8.4 Polymer Precipitation........................................................................................................71
8.5 Nitric Acid Precipitation...................................................................................................72
8.6 Electrochemical Treatment................................................................................................73
8.7 Summary of Chemical Treatment......................................................................................73
9.0 COLOR REMOVAL—OXIDATION PROCESSES............................................................. 75
9.1 Peroxide.............................................................................................................................75
9.2 Ozone................................................................................................................................78
9.3 Wet Air Oxidation with Catalyst.......................................................................................83
10.0 COLOR REMOVAL—EVAPORATION AND INCINERATION....................................... 85
10.1 Evaporation and Incineration of Bleach Plant Effluent.....................................................85
11.0 COLOR REMOVAL,—FUNGUS/BACTERIA/ENZYMES ................................................. 90
11.1 White-Rot Fungus Treatment............................................................................................90
12.0 TASK II:MILL-SPECIFIC REVIEW OF TECHNOLOGIES AND PERFORMANCE...... 93
12.1 Color in Study Mills..........................................................................................................93
12.2 Benchmarking...................................................................................................................97
� 12.3 Color Technologies in the Study Mills............................................................................101
13.0 SUMMARY AND CONCLUSIONS................................................................................... 106
REFERENCES .................................................................................................................................. 108
National Council for Air and Stream Improvement

TABLES
Table 2.1 Kappa Targets of Participating Mills..................................................................................5
Table 3.1 Correlation of Color to Other Parameters in Liquid Squeeze from
WashedUnbleached Pulp...................................................................................................6
Table 3.2 Correlation of Color to Other Parameters in Black Liquors...............................................8
Table 4.1 Impact of ECF Conversion on Effluent Color in the Study Mills.................................... 12
Table 4.2 Hexenuronic Acid Content of Various Pulps.................................................................... 15
Table 4.3 Comparison of Acid Hydrolysis Sequence with Other Bleach Sequences....................... 16
Table 4.4 Full-Scale Kraft Mill Ozone Bleaching Installations........................................................17
Table 4.5 Ozone Bleaching Laboratory Study Results on Softwood ZD and DZ Combinations..... 19
Table 4.6 Comparison of Effluent Data for Ozone and ECF Bleaching,kg/ADt.............................20
Table 4.7 Ozone Bleaching Laboratory Study Results on Hardwoods.............................................20
Table 4.8 Comparison of Bleach Sequences.....................................................................................21
Table 4.9 Examples of Full-Scale Peroxide Bleaching Installations................................................23
Table 4.10 Full-Scale Peracid Bleaching Installations.......................................................................24
Table 4.11 Effect of ePaa and dPaa-Stage on Bleaching Effluents...................................................25
Table 6.1 Example of Color in Acid and Alkaline Bleach Plant Effluents
inThis Study(ADT=shT)................................................................................................34
Table 6.2 ESP Ash Treatment Processes for Chloride and Potassium Removal..............................43
Table 6.3 Information about the IP (Franklin,VA)Mill Closed Cycle Bleach Plant.......................48
Table 6.4 Pilot Plant Results of Eka Chemicals Ultrafiltration Concept..........................................52
Table 6.5 Simulated(GEMS)Impact of PC+on Bleach Plant.........................................................53
Table 7.1 Results of OF and NF of Eop Filtrates..............................................................................58
Table 7.2 Information about Full-Scale OF Plants...........................................................................60
Table 7.3 Bleach Plant Effluent Characteristics...............................................................................67
Table 8.1 Full-Scale Installations of Coagulation as Tertiary Treatment.........................................74
Table 9.1 TAML Catalyst Pilot Plant Results on Bleach Plant Alkaline Effluent............................77
Table 9.2 Bleach Plant Effluent Characteristics (Bijan and Mohseni 2003)....................................79
Table 9.3 Whole Mill Effluent Characteristics(Zhou and Smith 1996)...........................................80
Table 10.1 Bleaching Effluent Evaporation Installations...................................................................89
Table 12.1 Summary of Color Balance Data in Four Papergrade Bleached Kraft Mills....................93
National Council for Air and Stream Improvement

Table 12.2 Summary of Mill A Color Data(ADT=Air Dry Short Tons of Bleached Pulp)-
2005 Data..........................................................................................................................94
Table 12.3 Summary of Mill B Color Data(ADT=Air Dry Short Tons of Bleached Pulp)-
2005 Data..........................................................................................................................95
Table 12.4 Summary of Mill C Data(ADT=Air Dry Short Tons of Bleached Pulp).......................96
Table 12.5 Summary of Mill D Data(ADT=Air Dry Short Tons of Bleached Pulp).......................97
Table 12.6 Successful External Technologies...................................................................................103
Table 12.7 Unsuccessful External Technologies...............................................................................104
Table 13.1 List of Color Reduction Technologies Included in the Evaluation ................................107
FIGURES
Figure 2.1 Effluent Color in Two HWD(SWD ECF Mills...................................................................3
Figure 2.2 Bleach Plant Effluent Color as a Function of Unbleached Kappa Number........................3
Figure 2.3 Example of a Yield—Kappa Diagram.................................................................................4
Figure 3.1 Washing Loss as a Function of Dilution Factor..................................................................7
Figure 4.1 Example of Color Reduction by Increased Substitution...................................................11
Figure 4.2 Impact of Kappa Factor on Bleach Filtrate Color.............................................................13
Figure 4.3 Contribution to the Kappa Number in Kraft Pulp.............................................................14
Figure 4.4 Example of an Acid Hydrolysis Stage(Domtar,Espanola,Ontario)................................15
Figure 4.5 Typical Arrangement of Ozone Medium or Low Consistency Stage(Espanola Mill).....18
Figure 4.6 High Consistency Ozone Stage.........................................................................................18
Figure 6.1 Daily Color for Three Mills...............................................................................................27
Figure 6.2 Example of a Simulation of a Fiberline Spill Collection System......................................32
Figure 6.3 Simulated Spill System Improvements..............................................................................33
Figure 6.4 Processes Involved in the Proposed Progressive System Closure at the
Skookumchuck Mill Based on the Literature....................................................................37
Figure 6.5 Simulated Impact of the Progressive System Closure.......................................................38
Figure 6.6 Fiberline Filtrates at the Blue Ridge Hardwood Line........................................................40
Figure 6.7 Fiberline Filtrate at the Blue Ridge Pine Line...................................................................40
Figure 6.8 Minerals Removal Process by Ion Exchange....................................................................41
National Council for Air and Stream Improvement

Figure 6.9 Impact of a Modest Recycle of Eop Filtrate on NaCl Content of White Liquor..............42
Figure 6.10 Crystallization CRP Process.............................................................................................45
Figure 6.11 Ion Exchange Process.......................................................................................................45
Figure 6.12 ESP Dust by Leaching......................................................................................................47
Figure 6.13 Bleach Plant Filtrate Recycle at International Paper,Franklin,VA.................................48
Figure 6.14 Bleach Filtrate Recovery at Metsa-Rauma Mill...............................................................49
Figure 6.15 Laboratory Simulation of Alkaline and Acid Filtrate Recovery.......................................50
Figure 6.16 EKA Nobel Partial Bleach Plant Closure.........................................................................52
Figure 7.1 Membrane Size Classifications.........................................................................................54
Figure 7.2 Ultrafiltration of Oxygen Delignification Effluents at the Nym6lla Sulfite Mill
inSweden..........................................................................................................................57
Figure 7.3 Ultrafiltration of Alkaline Filtrates from an ECF Bleach Plant........................................59
Figure 7.4 Color Removal Using NF270 Membrane.........................................................................61
Figure 7.5 Membrane Bioreactor.......................................................................................................63
Figure 7.6 USFilter's PACT System Process (Single-Stage,Aerobic)..............................................66
Figure 7.7 Color Removal at Different Activated Coke Dose and Activation Periods......................67
Figure7.8 Electrodialysis...................................................................................................................69
Figure 8.1 Color Removal Process Used at Skookumchuck..............................................................72
Figure 9.1 Post Color Treatment Efficiency......................................................................................75
Figure 9.2 Post Treatment Color Removal Percent Efficiency..........................................................76
Figure 9.3 Color Removal from Alkaline Bleach Plant Effluent.......................................................79
Figure 9.4 Color Removal versus Contact Time for Whole Mill Effluent.........................................80
Figure 9.5 Ozone and Biological Filtration at a Paper Mill...............................................................82
Figure 9.6 Super Critical Water Oxidation Process Developed by MODEC.....................................83
Figure 9.7 Color Removal with Pd-Pt-Ce/Alumina Catalyst.............................................................84
Figure 10.1 Pre-Evaporation of Bleach Plant Effluent.........................................................................85
Figure 10.2 Evaporation of Acid Bleach Filtrates,Carryover in Condensates....................................88
Figure 11.1 Color Removal in an Immobilized Fungal Bioreactor......................................................91
Figure 11.2 Color Removal by Algae Treatment.................................................................................92
Figure 12.1 Color Sources and Effluent Color in Four Study Mills....................................................98
Figure 12.2 Approximate Sources of Color from Hardwood Pulp Production....................................99
/ Figure 12.3 Approximate Sources of Color from Softwood Pulp Production.....................................99
National Council for Air and Stream Improvement

Figure 12.4 Bleach Plant Effluent Color at Varying Kappa...............................................................100
Figure 12.5 Benchmarking of Final Effluent Color............................................................................100
Figure 13.1 Effluent Color Benchmarking.........................................................................................106
National Council for Air and Stream Improvement

REVIEW OF COLOR CONTROL TECHNOLOGIES AND THEIR APPLICABILITY
TO MODERN KRAFT PULP MILL WASTEWATER
1.0 INTRODUCTION
1.1 Background
At the request of five U.S.bleached kraft pulp mills,NCASI contracted with EKONO Inc. to
undertake a review of color control technologies and their applicability to modem kraft pulp mill
wastewater.The study was to build on an earlier color reduction study carried out in 1995 (Baird
1995).
The ultimate goal of the current study is to help kraft pulp mills identify potential opportunities to
reduce effluent color. The specific objectives for each task are outlined below.
Task I:Develop a comprehensive list of different in-mill(both"brown"and bleached)and effluent
treatment color reduction technologies and describe the technologies,their applicability to modern
bleached kraft pulp mills,and their impact on color loads.
Task I includes a technology review based on literature and other information covering
• in-process measures,such as loss control,recovery of colored wastewaters,practical
minimum color losses associated with pulping liquor,modification of process operating
parameters (pulping and bleaching conditions),bleaching chemicals (CIOZ,H2OZ, ozone,
- etc.),and other operational practices
• treatment of color in wastewater, including wastewater from separate processes and
combined mill effluent wastewater through separation techniques(including management
of color residuals); using membranes, adsorption/ion exchange materials and color
removal/destruction techniques;using chemicals/polymers/catalysts,
evaporation/incineration,etc.
The detailed discussion was reserved primarily for technology or process operational practices
offered or adopted in the last 10 years.Data generated during this project are referred to as data from
the study mills.
Task II: Conduct a mill-specific review of the color control measures and benchmark the effluent
color of the participating mills relative to other mills.
Task II includes a)a mill-specific review of in-process loss control measures and end-of-pipe
treatment at each of the five mills participating in this project,including a review of successful and
unsuccessful in-process and end-of-pipe measures used to control color; and b)a benchmarking of the
current mill performance with respect to color contributed by bleach plant sources,and pulping liquor
sources.
1.2 Measurement of Color
Color is a property of the specific effluent sources in a mill.This report refers to the so called"true
color,"which in the U.S. is measured using the NCASI method(previously NCASI 253,modified to
NCASI 71.01 since 2000). The color of the effluent is measured by spectrophotometry at 460 rim
after(pre-filtration using a 1 µm filter),adjusting the pH to 7.6 and filtering the sample on a 0.8 µm
filter.The standard solution to which the color is compared is a solution of platinum and cobalt salts;
therefore, color is expressed in platinum cobalt units (PCU). The measurement of the color is
sensitive to the pore size of the filter and to the pH, so standardized conditions are needed.
National Council for Air and Stream Improvement

2 Technical Bulletin No. 919
Although color is a characterization of the effluent and not a quantity, it is customary to calculate
color as a mass(commonly expressed as lb color/d or kg color/d)based on the measured flow and
PCU concentration. Color permit limits are also varyingly expressed: as mass(lb color/d,kg color/d),
or as an effluent concentration,PCU, or as an increase in river color,PCU.
By treating color as a quantity, a mass balance can be developed for the colored streams in a mill. In
this effort many mills have documented a balancing problem. It is generally believed that the color of
the in-mill sources changes in nature on its way to the effluent treatment plant, increasing the color of
the sources.This so-called color amplification has been attributed to the presence of sulfide, green
liquor dregs,pH,mixing issues,anaerobic conditions,etc.
Similarly,mills treating the effluent in aerated stabilization basins have documented a reversion of the
color(or amplification)during the effluent treatment process.
The effect of sulfide on color reversion(amplification) in aerated stabilization basin influents and
effluents was the subject of a recent master's thesis(Esty 2005). Sulfide exposure experiments
undertaken with different effluents yielded as much as 100%color reversion in some tests,whereas in
other tests the results suggested that sulfide had relatively no effect on color reversion.The
differences appeared to be associated with the initial color of the wastewater;lighter colored samples
yielded higher color increase upon sulfide exposure than darker ones.It was concluded that the
underlying differences in color reversion appear to be related to the wastewater composition,given
the extreme variability of the wastewaters. When different humic functional groups were tested,the
catechol and anthraquinone solutions exhibited the greatest effect on sulfide color reversion.
The amplification or reversion of color was not included in this study.
2.0 TASK I: COLOR REDUCTION TECHNOLOGIES
2.1 Wood Species—Impact on Color
Since hardwoods contain less lignin than softwoods,the unbleached kappa number(or K number) is
lower for hardwood pulps than softwood pulps if the pulping and oxygen delignification processes
are similar. Therefore,the color of the effluent is lower for hardwoods than for softwoods.
A potential color control technology in multiple species mills is maximizing the hardwood portion, if
the product allows.An example of the difference in effluent color is illustrated in Figure 2.1.
Figure 2.1 shows the monthly average effluent color in two bleached kraft mills as a function of the
share of hardwood pulp production in each facility.Both mulls are equipped with oxygen
deligtufication for both softwood and hardwood,but have different age and effluent treatment
processes.The lines indicate that softwood operation generates about 28-401b/ADT more color than
hardwood operation.The difference is clearly mill-specific, depending on process systems and
running rates when alternating between hardwood and softwood.
National Council for Air and Stream Improvement

Technical Bulletin No. 919 3
6
50 • mill 1
0 5
0 0 Mill2
4
_0` 0
3
c 0
a
2
...............................a o...a
:._...._
w 0
1
0
0
0 2 40 60 8 10
%AHardwood Pulp Produc%d 0
Figure 2.1 Effluent Color in Two HWD/SWD ECF Mills
2.2 Kappa Number Reduction
2.2.1 Impact on Bleach Plant Effluent Color of the Kappa Number
The kappa number(K number) of unbleached pulp is an approximate measure of the amount of lignin
} in the pulp.
\� Since lignin contains color-causing compounds,the color of the bleach plant effluent has been found
to vary with the kappa number of the unbleached pulp entering the first bleach stage.Figure 2.2
illustrates the color of the bleach plant effluent in the sequence DEoDED for two different wood
species,based on work by Liebergott(Liebergott 1992).Between kappa numbers 17 and 25,the
bleach plant effluent color—unbleached kappa lines have a slope of around 5.6 lb color/ADT/kappa
unit.A reduction of the kappa number,for example by 8 units from 25 to 17,has the potential to
reduce the effluent color by about 45 Ib/ADt.
160
140 'Hemlock
•S NCC msam
120 (f
Q
a too
80
0
C
40
20
0
10 15 20 25 30 35
Kappa
Figure 2.2 Bleach Plant Effluent Color as a Function of Unbleached Kappa Number
(based on Liebergott 1992)
National Council for Air and Stream Improvement

4 Technical Bulletin No. 919
The color/kappa relationship is exponential,so a reduction from a kappa level of 17 to a lower kappa
would not result in the same color reduction as from kappa 25.
No similar documentation was found for hardwood pulp.The color/kappa relationship may be
different for hardwoods than for softwoods.Hardwoods have a higher content of hexenuronic acids,
which also are measured with the kappa measurement.The contribution to color of the hexenuronic
acids is most likely different from lignin-originated color,although not much data is available on
color of hexenuronic acids (see Section 4.2).
2.3 Oxygen Delignification
Oxygen delignification is the most widely used method in lowering the kappa number.Reduction of
the kappa number in the cooking process has also been studied and used, especially in the early
1990s. Studies of the pulp yield in laboratory and mill conditions have confirmed that cooking to low
kappa results in a reduced yield compared to oxygen delignification to the same kappa,as illustrated
in Figure 2.3 (Axegard and Stigsson 1998).
Yield,%on wood
so
48 ............I........................Op�ellgnnic9tion....
Bleaching
46 ...........i......... I_. ..........
I
44 ....-----[.:.- _... ....._j--------i..........
. .........: ...... E cooking .
42
40
0 5 10 15 20 25 30
Kappa number
Figure 2.3 Example of a Yield—Kappa Diagram
With respect to kappa optimization between cooking and oxygen delignification,the trend is to target
a somewhat high digester kappa and take a large kappa drop in the oxygen stage.This is done in order
to maximize the total pulp yield.In newer and modified oxygen delignification installations,the trend
is to have a two-stage oxygen delignification system with or without intermediate washing.
A lower kappa means lower wood yield,i.e., a higher amount of dissolved wood material to remove
during pulp washing.More biofuel energy can be produced in the recovery boiler and less chemicals
will be consumed in the bleaching.However,the kappa target is very mill-specific and is determined
mainly by the process and final pulp quality and other requirements.Too low digester kappa
deteriorates the pulp strength and impairs its paper making properties.Kappa targets of the mills
participating in this study are shown in Table 2.1.
National Council for Air and Stream Improvement

Technical Bulletin No. 919 5
(r 1
Table 2.1 Kappa Targets of Participating Mills
Lines w/o Lines with
oxygen delignification oxygen delignification
Softwood pulp
Digester kappa 26—28 25—36
Unbleached kappa 16-22
Hardwood pulp
Digester kappa 16-20 15 -22
Unbleached kappa 10- 14
Use of polysulfide and/or anthraquinone can compensate the yield loss when lowering the kappa to
bleaching(Jiang, van Lierop,and Berry 2002).The feasibility of polysulfide anthraquinone(PSAQ)
cooking and the impact on product qualities and papermaking,however,is mill-and product-specific.
One mill has installed PSAQ cooking process together with oxygen delignification and documented a
reduction of effluent color by about 50-601b/ADt(Pagoria 2005).
All the study mills that have implemented oxygen delignification have also noticed significant
effluent color reductions.
In addition to reduced bleach plant effluent color,a reduction of the kappa number also impacts the
following factors.
• Environmental parameters: lower BOD, COD,AOX per ton of pulp
• Chemical cost: lower bleach plant chemical costs
• Wood cost: lower yield—higher wood costs
• Biofuel: increased steam amount from biofuel in the recovery boiler(unless the boiler is
steam limited)
• Pulp strength: Too low kappa, especially from cooking,can damage the pulp and its strength
properties.
3.0 BLACK LIQUOR LOSS CONTROL
All kraft mills lose some of the black liquor from the liquor loop. There are in principle two types of
losses:
• stationary or continuous losses that are mainly determined on the equipment design and
efficiency; and
• diffuse losses and temporary discharges(i.e.,spills,leaks, overflows).
The stationary losses include continuous losses such as washing losses,reject losses,knotter system
losses,brown stock screen room white water losses, carryover of liquor in condensate streams, and
evaporator boil-out losses.These controllable process losses are discussed in Section 3.
The temporary discharges include spills,leaks,overflows,wash liquids and similar discharges that
can happen accidentally, or they can be part of normal mill shutdown/start-up procedures.These
types of losses are discussed in Section 6.1.
1
National Council for Air and Stream Improvement

6 Technical Bulletin No. 919
— The technologies for loss control and for recovery of lost black liquor are overlapping,since the
accidental losses can be controllable with the spill collection systems.
3.1 Improved Brown Stock Washing
Brown stock washing in modern mills is a completely countercurrent process,including brown stock
screening and possible post oxygen delignification washing. The carryover of black liquor or oxygen
delignification stage liquor to the bleach plant in the pulp off the last washer in the brown stock fiber
line,prior to any dilution,represents the washing loss.
The washing loss is typically measured as the amount in the pulp sheet of salt cake(Na2SO4), COD or
conductivity,and more seldom as color in the pulp sheet.Available data for the relationship between
color and other parameters are summarized in Table 3.1.
Table 3.1 Correlation of Color to Other Parameters in Liquid Squeeze
from Washed Unbleached Pulp
SWD/02 HWD/No02 HWD/02 SWD/02
Color/COD 0.9 3 0.5 0.6
PCU/ppm (1.5-5.5) (0.3-0.9) (0.4-0.9)
Color/Na2SO4 1.1
PCU/ppm
Color/Dry Solids 0.8 3.5 0.7 0.9
�J PCU/ppm (2.1-4.9) (0.4—1.0) (0.6—1.2)
Color/ 1.0 7.7 1.8 1.2
Conductivity (3.9—9.8) (1.0—3.0) (0.7—1.8)
PCU/µS/cm
The data in Table 3.1 indicate that the color of the carryover to bleaching varies.For all oxygen
delignified pulps,the relationships between color and other parameters are about the same order of
magnitude.The washing loss of the hardwood pulp without oxygen delignification seems to carry
more color than the oxygen delignified pulp. Obviously these relationships are mill-and-process
specific but may be useful when investigating color sources and reduction technologies.
The color of the washing loss carried in to the bleaching process will to some extent be bleached in
the first Do stage and then discharged in the bleach plant effluent with the wash filtrates.The extent
of this"color bleaching"of the carryover liquor was not found in the literature.However,a typical
engineering estimate is 50-70%reduction of the color originating from the black liquor in the
bleaching process.
Independent of the extent of the bleaching of black liquor originated color,the carryover to bleaching
will have a certain impact on the bleach plant effluent color. Therefore, a reduction of the carryover
reduces bleach plant effluent color.
The washing efficiency and thereby the carryover to bleaching is detennined by the washing
equipment and the dilution factor in the pulp washing.In addition,the wood species,liquor charges,
and kappa drop in the oxygen delignification impact the result. One guideline for the carryover to
bleaching is provided by the European Union's BAT document(EU-IPST 2001)where the following
data are given:
National Council for Air and Stream Improvement

Technical Bulletin No. 919 7
Washing loss with conventional drum washers 10-16 lb COD/ADt
Washing in a modern line with presses 4-8 lb COD/ADt
The washing loss can vary significantly in a given washing configuration, especially if the dilution
factor vanes significantly.For example,when the production rate varies,the carryover can show
significant variations.
Figure 3.1 illustrates the carryover as liquor solids as a function of the dilution factor for two washing
configurations with different washing efficiencies, E values (EKONO 2006).
Example of Carryover from Pulp Washing
70
o i
Q fi0 ___ ______I___ +currant _
I
� I
50 ____ ____!_
washing _
m sW a
0
`g
N
9 I I
O 'tQ Y J
W I
I
� I I
� I
� I I
J 0
0 1 2 3 4�pq 5
Dilution Factor, m31ADt W ElECDNO
aawcag.r
Figure 3.1 Washing Loss as a Function of Dilution Factor
Because the carryover-dilution factor relationship is logarithmic,the washing loss can vary
significantly if the dilution factor is not kept constant.If, for example,the dilution factor is allowed to
decrease from 2.5 m3/ADt to 1.5 T/ADT the washing loss may increase by 11- 17 lb/ADT as liquor
solids (BLDS)or as about 9-14 lb/ADT as black liquor color. On the other hand, the washing loss
decreases only by 2-4 lb BLDS/ADT when the dilution factor increases from 2.5 to 3.5 T/ADT.The
stabilization of the dilution factor and the pulp washing process overall can be implemented with
advanced controls and paper design.
In summary,the best available technology(BAT)for carryover of black liquor to the bleach plant is
4-8 1b COD/ADt(4-8 1b washable Na2SO4/ADt or about 4-8 lb color/ADt)when washing with clean
water. This level of washing loss is estimated to contribute 2-4 lb color/ADt to the bleach plant
effluent color.
The reduction of the carryover of washing losses to the bleach plant has these benefits:
• lower bleach plant effluent color,estimated to be about 0.5 lb color/lb BLDS carried over to
the bleach plant, assuming that the black liquor color is reduced by 50%in the bleach plant;
lower bleach plant effluent BOD,COD, and AOX;
• lower bleach plant chemicals demand,i.e., about 0.85 1b active chlorine/lb COD (332); and
• more bio-energy from the recovery boiler
U
National Council for Air and Stream Improvement

8 Technical Bulletin No. 919
Possible cost items may include increased steam costs in the evaporation plant if the dilution factor in
pulp washing increases.
3.2 Reduction of Other Regular Black Liquor Losses
Black liquor lost to the sewer contributes to color.Black liquor losses are typically measured as dry
solids,conductivity, sodium, COD,and less often as color,although some mills measure liquor losses
as color.Examples of correlation of the color of black liquor to other black liquor parameters are
shown in Table 3.2.
Table 3.2 Correlation of Color to Other Parameters in Black Liquors(EKONO 2006)
Color/ Color/COD Color/NaZSO4 Color/Dry
Conductivity PCU/ppm PCU/ppm Solids
PCU/µS/cm PCU/ppm
Dilute black liquor 2
Specialty pulp mill 4
Pre-02 filtrate squeeze 0.7 1.2 0.6
Pre-Oz washing filtrate 1.2 1.1 1.1 0.82
3.2.1 Effluent-Free Knot Handling
The term"knots"frequently describes the rejects of the first stage of screening after cooking.This is
where the screen hole or opening is around 0.25-0.5 in.Knots include good chips that did not get
impregnated,as well as the"biological"knot(for example,where a branch connected the tree trunk).
Biological knots are very dense and have an extremely high lignin-to-fiber ratio.Their fiber yield is
thus low.In addition,they require more energy and white liquor consumption than normal wood.
Biological knots primarily become dissolved solids in the black liquor rather than pulp.Knots also
contain rocks,bullets,and tramp metal. Chip thickness screens, air density separators,and chip-
conditioning devices have all improved the capability of reducing the traditional"knot"reject stream.
(Bucher 1999).
Knots can be handled in different ways,most often by recooking, landfilling or burning.From a color
discharge point of view, it is important that the knots are handled without losing black liquor to the
sewer.
The knotters typically operate in series of two stages with the knots rejected from the second stage.
When the knots are returned to the digester(s)the knots are dewatered(e.g., in a knot drainer)and the
dewatering liquor returned to the washing line,so there is no effluent from the knot handling in those
cases. Vibratory knotters are used in many mills as the secondary knotting stage. These open knotters
are often a source of spills and leaks, even if the knots are recooked.
Some black liquor may accompany the knots as they are removed from the fiber line.
In one mill the knots were sluiced out of the process with decker brown water.By replacing the sluice
water with paper machine white water,the mill estimated the COD discharge to decrease by about 3
lb/t(Genco 2005).The black liquor color discharge would have decreased by roughly the same
i ) amount(EKONO's estimate).
National Council for Air and Stream Improvement

Technical Bulletin No. 919 9
One of the study mills in this survey has installed recovery sumps on the knot reject bins and recovers
the liquor drained from the knots to the brown side spill collection tank. This measure,together with
other improvements in spill collection and internal color control in the digester and brown side sewer,
reduced the color by about 8000 lb/d on the hardwood line(about 10 lb/ADt of HW pulp).
3.2.2 Closed Screen Room
In modem mills the screen room water system is part of the brown stock washing,and is carried out
in a closed,completely countercurrent system.This is true whether or not oxygen delignification is
used in the fiber line. The only stream leaving the system may be the screen room fine reject(in
addition to knots removed earlier in the fiber line). See Section 3.2.3.
During so-called"open screening,"the filtrate from the last washing stage (normally the decker
following the screening)would not be taken counter-currently back to the brown stock washing, but
would partly overflow to the sewer. The closing of the water cycle may require new screening
equipment and larger filtrate tanks and may be costly in older mills.However,most modernized
papergrade bleached kraft mills have implemented closed screening.The benefits include water and
energy savings as well as lower effluent load of black liquor.The carryover with the pulp to
bleaching may,however,increase and thereby increase the bleach plant chemicals demand,
depending on the efficiency of the washing following the screen room.All the study mills reported
the closing of the water systems in the screen room as a significant color reduction technology. One
study mill has documented a color reduction of 35%by implementing closed screening.
3.2.3 Effluent-Free Reject Handling
Most mills purge a small stream of reject from the screen room in order to discharge impurities.The
color load associated with that reject stream depends on the amount and consistency of the reject and
the concentration of the liquid discharged with the reject. Options to reduce color discharge with
reject streams include the following.
• Upgrading of screening equipment. In one mill, the primary and secondary screen baskets
were replaced with slotted baskets on a hardwood pulping line.This allowed the mill to shut
down the brown stock cleaners and eliminate the cleaner reject stream.The resulting
reduction in black liquor originated COD was around 9500 lb/d(Genco 2005) or as color,
roughly 12 lb/t HW pulp.
• Replacement of brown white water with less colored water for dilution of rejects prior to
sewering. In one mill,the brown white water was replaced by paper mill white water at an
estimated COD reduction of about 5800 lb/d or about 10 lb/ADt SWD pulp or approximately
10 lb color/ADt(Genco 2005). One mill employing oxygen delignification and a modernized
closed screening system discharges about 1.5-2 lb color/ADt pulp with the reject when using
combined condensate for diluting the feed to the last reject screening stage(EKONO 2006).
• Washing and dewatering of the final reject with recovery of the wash filtrate and dewatering
liquids.After dewatering,the reject can be burnt or landfilled. There would be no effluent in
such a system. One of the study mills documents the installation of reject presses to have
resulted in equipment problems and is considering abandoning the pressing due to unreliable
operation.The color associated with the reject is reportedly around 1500-2000 lb/d;however,
the black liquor color is typically reduced by 50%in their effluent treatment plant,so the
impact on the final effluent would be lower.Another study mill successfully operates a press
on the screen room reject.
• Depending on the ultimate reject disposal, a refining stage may be included in the reject
handling, especially if the reject can be used for other grades(e.g., corrugated medium).In
National Council for Air and Stream Improvement

10 Technical Bulletin No. 919
such a case the rejects would be washed after refining and the wash liquids recovered in the
liquor cycle.
In summary, a good target for the color discharge related to reject handling is 0-21b/ADt, depending
on how the rejects are disposed of.
3.2.4 Minimization of Carryover in Black Liquor Flash Vapors
Vapors flashed off from black liquors often carry with them droplets or mist of black liquor.The
amount of carryover varies widely, depending on factors such as liquor properties,foaming tendency,
solids levels,soap content,process temperature and pressure,vapor velocity,efficiency of drop or
mist separation,and elimination equipment.
Mills normally have safeguards in the form of conductivity meters and alarms in order to detect
carryovers and counteract such situations.
Potential process points for black liquor carryover into condensing vapor streams that can enter the
sewer systems include
• digester relief vapors (batch digester relief,steaming vessel relief);
• digester flash tank or blow tank vapors;and
• black liquor evaporator vapor dome or vapor side vapors.
In normal conditions, the color from liquor carryover into the condensate streams is low because of
effective entrainment separators and mist eliminators.
The carryover(conductivity)is also limited by the way the condensates are handled or reused. If
stream stripping is employed,the condensates taken to the stripping have to be clean from black
liquor in order to avoid foaming and to maintain the stripping efficiency of the volatile compounds.A
normal conductivity limit is around 300 µS/cm(approximately the same in color units).Above this
limit the condensates would be recovered to the spill system or sewered.
A similar limit is typically used if the condensates are reused in the pulp washing or recausticizing
area in order to eliminate foaming or total reduced sulfur(TRS) emissions.
Contaminated condensate can have a color level at about 400 PCU. Clean condensates(e.g.,
condensates from effects 2-4 in a five-effect evaporation plant) typically have a color concentration
below 100 PCU. Condensates can therefore contribute with a black liquor originated color of around
1-3 lb/ADT.
3.2.5 Evaporator Boil-Out Procedures
Evaporator surfaces can scale for many reasons and by many compounds (by burkeite,which is a
sodium carbonate-sulfate mixed salt,by calcium carbonate,by aluminum silicate,by soap or fiber,
etc.). The evaporator surfaces need to be regularly cleaned to maintain efficient heat transfer. Of
course it is also important to try to prevent the formation of scaling through various measures
(Gullichsen 2000),but even if scale prevention is implemented,scaling may occur.
The scaling with burkeite occurs mainly in effects with>40%liquor solids concentration. This
scaling is typically removed by washing with weaker liquor(switching of effects).
Other scaling,such as CaCO3 scaling,requires boil-out with water, condensate or acid washes.Liquor
losses can occur if the boil-out procedures are not carefully managed.The unit to be washed is first
drained to liquor storage. The wash and rinse liquids can be fully recovered or recovered until a set
National Council for Air and Stream Improvement

Technical Bulletin No. 919 11
conductivity value is reached, after which the rinse liquids are sewered. The set point of the
conductivity, together with the amount of rinse liquid sewered, determines the black liquor lost in this
way.
A normal conductivity cut-off value for sewering the boil-out liquids may be around 2500 µS/cm(or
approximately 2500-5000 PCU of color). Sewering of,for example, 800 gpm of rinse liquid at that
concentration means a color discharge of 1000-2000 lb/h(24000-48000 lb/d),a significant color
contribution if prolonged.
4.0 BLEACHING
4.1 Chlorine Dioxide Bleaching
Bleaching with chlorine dioxide or ECF bleaching is standard BAT for papergrade bleached kraft.
Bleach sequences for dissolving kraft,however,may include hypochlorite or chlorine bleaching.
Bleach Plant Effluent Color as a Function of
CIO,-substitution(based an Ueborgolt)
50o
450
460 ____ __ ,K, 16.6 ___
Y -I
0
a 250 ----I_____I__-_J__-_
0266 ----�---'--'--'-----'- --a--
a I
_____ ____
I I I
_J _ JI
1 I I I
0
a 20 40 60 60 too 120
Subs1ftuUM%
Figure 4.1 Example of Color Reduction by Increased Substitution
All papergrade mills participating in this study converted to ECF within the last 10 years and have
documented significant reductions in effluent color with the conversion to ECF bleaching.The impact
of increased substitution based on laboratory studies is illustrated in Figure 4.1,based on data by
Liebergott(Liebergott 1992).
Table 4.1 shows the approximate effluent color reduction experienced from the conversion to ECF
bleaching in three mills,where the conversion impact could be approximately separated from other
improvement measures.
The percent reduction has of course varied depending on the C102 substitution degree before the
conversion to ECF and on other measures that were implemented in the same time frame.
L�
National Council for Air and Stream Improvement

12 Technical Bulletin No. 919
Table 4.1 Impact of ECF Conversion on Effluent Color in the Study Mills
Color before ECF Color after ECF Reduction, %
Mill 46lb/T 28lb/T 41%
Mill 2 100000 lb/d 70 000 lb/d 30%
Mill 45000lb/d 36000lb/d 25%
The operation of the Do(or 13100)stage may offer some opportunities to impact bleach plant effluent
color,i.e.,by varying the kappa factor and the temperature. One option to optimize the Do stage is to
reduce the kappa factor(underbleach) in the Do stage and increase the bleaching power of later stages
by reinforcing the extraction stages with oxygen and peroxide and if necessary,increasing the C1O2
charge in the Di and D2 stages.Another option is to increase the kappa factor(overbleach)in the Do
stage. The C1O2 required to reach a target kappa number is a function of pH, chloride ion
concentration,the type of pulp, and extraction stage conditions. Pulp mill bleaching conditions such
as pulp consistency,temperature,retention time,and pulp cleanliness are extremely vaned. In
addition,the objectives of bleaching,in terms of target brightness,cleanliness,and strength differ
among products and mills.Because of this variety,bleaching conditions must be optimized for each
product produced at each mill.
The impact of the kappa factor on the ECF bleach effluent Do and Eop stage color was documented
by Wohlgemuth,Lam,and Willis (1997)for a conventional brown stock softwood pulp of kappa 29.7
in mill and laboratory trials.
National Council for Air and Stream Improvement

Technical Bulletin No. 919 13
As shown in Figure 4.2, the color of the Do stage effluent was highest around a kappa factor of 0.18-
0.20 and declined if the kappa factor was increased to more than 0.25 or decreased to below 0.18.The
color of the Eop stage effluent steadily decreased with increasing kappa factor. The increase of the
kappa factor would result in somewhat higher bleaching costs.
DoEop filtrato colourvs KF Bleaching savings vs KF
Hm um
uv
um
sxoo um
Was n]o
!Dpg !}.N
g b' tom
bin — 500:
Y !pp
NM
Y tO
5pm
O}I 011 LLR 09 02I pq
kappa factor app.Na
..
Do colourvs KF Eop colour W Kappa Factor
ie5o aeao T.
1 �
rOm 5
a GC Y apm
U pm )¢O I
.0 a10 pJ! pA oaa am
0 Wppa FaNm
aL0 at0 LLq aA am am raOTnEW I •1a% .olY .a5% .01%
Wppa F%Cm µ•pa
5•
Figure 4.2 Impact of Kappa Factor on Bleach Filtrate Color(Wohlgemuth,Lam,and Willis 1997)
Conventional chlorine dioxide bleaching(Do stage)is usually conducted at 50-70 aC for 30-60
minutes. One option that has been studied to improve D stage bleaching is to raise the reaction
temperature to 85-95aC and extend the reaction time to 90-150 minutes in a so called DHat stage or
commonly denoted as D*.Most work with hot C1O2 bleaching has focused on hardwood pulps
because they seem to give better results in a hot D stage than softwood pulps. (Lachenal and Chirat
2000). This is generally considered to stem from the fact that hardwood pulps have higher
hexenuronic acid(Hex A)content than softwood pulps. Some recommendations for a hot D stage
include the use of a hot acid stage before the hot D stage(i.e.,ADhot stage), optimization of the pH to
improve performance,and the addition of sulphamic acid or formaldehyde to the hot D stage to
reduce organically bound chlorine in the pulp.Although the hot D stage could be used to replace any
D stage(Do,Di,DA it generally gives the best results when used to replace the Do stage. One
proposed five-stage bleaching sequence is H,Do-Eop-Dl-HatDa-P.The final peroxide(P)stage is used
to increase pulp brightness and improve the brightness stability of the pulp. One drawback with the
i hot D stage(D*)is a slightly negative impact on the pulp viscosity and the energy required to reach
high temperature.Hot CIO,bleaching has been shown to significantly lower the AOX discharges
National Council for Air and Stream Improvement

14 Technical Bulletin No. 919
from bleaching.Part of the AOX reduction comes from the fact that less C102 is required to reach the
same brightness level and part from the fact that the elevated reaction temperature and extended
reaction time in a hot D stage cause the AOX to be degraded to chloride ions (Lindstrom and Ragnar
2004;Ragnar 2005).The impact on effluent color from a D* stage was not found in the literature.
The first D* stage began operation in 2002(Ragnar 2005).
4.2 Hydrolysis Treatment for Removal of Hexenuronic Acids
Hexenuronic groups(Hex A)are formed in kraft pulp cooking when methanol groups are split off
from xylan while transforming the glucuronic acid components to unsaturated hexenuronic acid units.
The hexenuronic acids contribute to the kappa number as exemplified in Figure 4.3.
20 10
16 g
■M1gNn
18 OHexA 6
`e 14 Oabmsmcmos 7 t•Ggan
DHexA
Dane.svwraes
12 3 6
b 10 5
E 6
6 4
6 a
4 2
2
01 L
0
Unbleached 02-derignRed OD bleached ODE. Unbleached 02-0erignified 00-bleached OO(OP)-
bleached bleached
Spruce Kraft Pulp Birch Kraft Pulp
Figure 4.3 Contribution to the Kappa Number in Kraft Pulp (based on Sevastyanova,Li,and
Gellerstedt 2002)
The impact on hardwood pulps is more significant than on softwood pulps and more significant for
oxygen delignified pulps than for pulps without oxygen delignification.The hexenuronic acids
consume bleaching chemicals(all except oxygen and peroxide).The hexenuronic groups also provide
anionic sites to bind transition metals and heavy metals to the pulp,the presence of which contributes
to pulp color reversion and aging of the pulps,and if peroxide bleaching is employed,to the peroxide
decomposition by free radicals.Removal of the Hex A groups can thereby also reduce the peroxide
consumption.
In general,softwood pulps contain fewer hexenuronic acid groups than hardwood pulps(Figure 4.3).
Therefore,the removal of hexenuronic acid groups from hardwood kraft pulps prior to bleaching can
provide substantial reductions in chlorine dioxide consumption,but the savings for softwood pulps
are less. In addition,the various cooking methods impact the hexenuronic acid content of the pulp as
can be seen in Table 4.2.
National Council for Air and Stream Improvement

Technical Bulletin No. 919 15
Table 4.2 Hexenuronic Acid Content of Various Pulps (Jiang, Van Lierop, and Berry 2000)
Pulping Process Wood Type Kappa Number Hexenuronic Acid
Mmol/g
Conventional(batch) Hardwood 18.2 76
Conventional(batch) Softwood 25.9 54
Conventional Softwood 25.5 22.7
Lo-Solids Softwood 21.0 15.3
Soda Softwood 25.0 0.5
Soda-AQ Softwood 21.0 3.7
Polysulfide Softwood 24.2 4.6
The impact of the Hex A groups can be reduced by introduction of a selective hydrolysis step in the
bleaching sequence, generally as the first stage following the last brown stock washer.The selective
hydrolysis would be performed at conditions to be optimized for different pulps.Testing has been
carried out at pH 3-5,temperature 85-115°C for 1-5 hours (Lindstrom and Ragnar 2004;Ragauskas
2000).Full-scale installations exist in several mills outside North America and at Domtar's Espanola,
Ontario mill on oxygen delignified hardwood pulp as an A Z/D E Do D sequence(Semeniuk et al.
2002). See Figure 4.4.
rin,
h d I
1
A Z / D E Dn D
Sequence O-A-ZO-E-Dn-D Chemical Savings 20%
Wood Species Birch;Aspen,Maple Final Brightness >90%,ISP
Post 02 Kappa 8.0 Final Viscosity unchanged
COD in Pulp -Skg/T Tensile unchanged
02 consumption 3-6 kg/ADT TOX in pulp 50-70%reduction
C102 R-R 2.5 to 3.5 Dirt zero
Figure 4.4 Example of an Acid Hydrolysis Stage(Domtar,Espanola,Ontario)
The impact on effluent color of an acid hydrolysis stage is likely to vary depending on the sequence
and bleach plant water configuration.Ragauskas determined the color of the effluent from a
hydrolysis stage treating well-washed HW kraft pulps (Kappa range 11.6-14.2) for 5 hours, at 2%
consistency,pH 3 and 100°C,and found a color varying between 120-220 PCU(approximately 10-20
lb/ADT)depending on the kappa drop in the acid hydrolysis stage(Ragauskas 2000).No information
about the color of the effluents from subsequent bleaching was available from this study.
The effluent color of complete bleach sequences with and without acid hydrolysis was studied by
Colodette et al. (2002,2005)on eucalyptus pulp. The laboratory study included bleach plant effluents
National Council for Air and Stream Improvement

16 Technical Bulletin No. 919
without filtrate recovery and with filtrate recovery to brown stock and the recausticizing area.
Although the study was for a non-North American wood species, the results are included here for
their conceptual value.
Their study on open bleaching included the sequences D (EoP)D D,Ah°t(Eop)D (PO)and Dh°t(Eop)D
(PO),with a washing between each stage. The bleaching was performed on a pulp with kappa number
8.3 and with a comparatively high washing loss as canyover COD=26 kg/t(52 lb/ADT).The reported
data are summarized below(Colodette et al.2002).
Table 4.3 Comparison of Acid Hydrolysis Sequence with Other Bleach Sequences
Unit D(EoP)DD AW(EoP)D(PO Dhot(Eoe)D(PO).
Brown stock kappa 8.3 8.3 8.3
Carryover kg COD/t 26 26 26
Total C102 % 1.876 0.845 0.85
Total H2O2 % 0.333 1.333 0.9
Effluent AOX g/t 1112 277 554
Effluent COD kg/t 35.2 39.6 38.1
Effluent BOD kg/t 10.8 18.2 16.8
Effluent Color kg/t 34.1 44.4 33.8
Final viscosity mPa.s 13.4 11.5 11.4
Brightness A.D%ISO 90 89.9 90.0
The data in Table 4.3 indicate that the bleach sequence D(EoP)DD generated the lowest colored
effluent and produced pulp with highest viscosity. The relatively high effluent color in the acid
hydrolysis sequence may partly have been due to the high COD carryover,which would have been
"bleached"in the D(EoP)DD but not in the acid hydrolysis stage.Based on the data in Table 4.3, one
can conclude that if the bleach plant filtrates are not recovered,an acid hydrolysis stage may increase
the influent color if the pulp is washed after the hydrolysis stage.
The concept of recovering bleach plant effluents from sequences including an acid hydrolysis stage is
included in Section 6.2.3.4.
4.3 Ozone Use in Bleaching
4.3.1 Process and Applications
Ozone bleaching has received considerable attention during the last ten years as an opportunity to
reduce bleaching with chlorine containing chemicals.
Ozone gas is a basic industrial chemical that has been widely used,for example,for chemical
synthesis. Ozone must be produced on site because it is unstable with a half-life in water of 20-30 min
at 20°C.It is produced by passing oxygen through a discharge gap between two electrodes. This
discharge causes dislocation of the oxygen molecules,some of which subsequently recombine in the
form of ozone. The oxygen carrier gas is typically recovered and returned to the ozone reactor. Ozone
can be produced at up to 13-14%concentration in oxygen gas;when exceeding a concentration of
15%,the gas mixture will be dangerous to handle. Ozone is one of the strongest oxidizing agents
known and has, like oxygen,some selectivity toward lignin attack over cellulose,but it requires
optimized process conditions in order for it to not cause any serious fiber degradation.
National Council for Air and Stream Improvement

Technical Bulletin No. 919 17
For industrial-scale bleaching,both medium-and high-consistency systems have been used. Low
consistency ozonation tests have been run at the hardwood mill in Espanola, Ontario,using the
sequence OA(ZD)EDnD. The tests showed equal kappa reduction and ozone consumption and lower
COD and power consumption when compared to the medium consistency stage(Epiney et al. 2002).
Because of the considerably lower capital costs and the developments in mixing technology,the
medium consistency approach may have been more popular than the high consistency operation.High
consistency operation may offer an opportunity to more effectively separate the water systems.
Several new installations have been high consistency. No low consistency ozone stage is currently
not in operation.
The use of ozone has been investigated for pulps without or with preceding oxygen delignification.
However,ozone sequences in use currently all follow an oxygen delignification stage See Table 4.4.
The prerequisite for ozone bleaching include metals removal in an acid washing and/or chelating
stage, i.e., a D or a Q stage.The ozone bleaching stage itself is simple,consisting of a mixer or mixers
for ozone,a short reactor(2-5 min)and a washing stage or it is followed by the next bleaching stage.
The pH is typically around 3 and temperature at 40-50°C.
There are many full-scale installations using ozone bleaching,some of which are listed in Table 4.4.
Examples of medium and high consistency ozone stages are shown in Figures 4.5 and 4.6.
Table 4.4 Full-Scale Kraft Mill Ozone Bleaching Installations
Approximate
Start- Capacity
Mill up Type Sequence (ADt/d)
IP,Franklin,VA,USA 1992 ECF,HC O(QZ)EoD 900
Stora,Skogball,Sweden 1992 ECF OZDEnDED,Pilot plant 200
MoDo,Husum,Sweden 1993 TCF OQPZP 1000
Metsa-Bomia,Kaskinen,Finland b 1993 TCF/ECF OPZ/ODPZ 1200
UPM,Pietarsaari,Finland"' 1993 ECF/TCF OQXZQO(PE),ZP(TCF) 1000
O(ZD)O(PEp)DEPD
SCA,Ostrand,Sweden 1995 TCF,HC Q(OP)(ZQ)(PO) 1250
Metsa-Rauma,Rauma,Finland 1996 TCF (00)(ZQ)P(ZQ)(PP) 1000
Stora-Enso,Wisconsin Rapids,WI, 1996 ECF,HC OZEoDD
Votorant,Lacarei,Brazil 1996 ECF
Votorant,Luis Antonia,Brazil 1997 ECF/TCF
ZP Rosenthal,Germany 1999 ECFITCF, Q(OP)DQZ(PO)P(ECF) 900
HC Q(OP)QZ(PO)P(TCF)
Domtar Inc.,Espanola,ON 1999 ECF OA(ZD)EDnD 1000
Burgo Ardennes,Belgium 2000 ECF,HC ODZEOpDD 1030
Votorantim Celulose a Papel(VCP), ECF,HC OAZEDP 2100
Jacarei Mill,Brazil
Sappi Ngodwana SW OA(ZD)(EO)D
Ruzumberok,Slovakia 2005 HC.
Oli,Nichinan,Japan HC
a HC=high consistency b Main product is ECF pulp. Ozone is not used in all sequences
National Council for Air and Stream Improvement

18 Technical Bulletin No. 919
Os vent to destruct unit
®resld-I
%ems
%Delignified Pulp from Aslage wash press
[DA Inlet
Dilution water -
P,T
To Dostage
%miser %mixer
Pulp and filtrate Pulp and filtrate
sample sample
I Figure 4.5 Typical Arrangement of Ozone Medium or Low Consistency Stage(Espanola Mill)
(Epiney et al.2002)
Spent Gas
to recycling
From Oypost washing
H2SO4
Chelant --
Ozone
r
To 02-post washing
Figure 4.6 High Consistency Ozone Stage(Gullichsen 2000)
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Technical Bulletin No. 919 19
1
4.3.2 Risks
The main risk associated with the ozone technology is reduction in yield and potentially the pulp
strength.
A recent study documented a yield loss of 0.5%and 0.8% for the sequences(DZ)EpDED and
(ZD)EpDED, respectively, compared to the conventional DEpDED sequence on softwood pulp
(Huber et al.2006).
4.3.3 Environmental Lnpact
Ozone breaks down the lignin into smaller compounds.Thus,without filtrate recovery,BOD and
COD could rise in the untreated effluent. Treated effluent BOD and COD might not increase,
however,because the lower molecule weight compounds break down more easily in the ASB.AOX
would be reduced due to lower chlorine dioxide consumption.
Metso's ZE-Trac process(former Union Camp's"C-free"process) includes recovery of the ZE stages
back to brown stock washing(http://www.metsopaper.com/). Scandinavian mills using ozone
bleaching are also exploring partial or total recovery of the filtrates.In such a case,the effluent
discharges in the bleaching effluent can be greatly reduced(see Section 6.2.3).
Table 4.5 shows data for three different North American softwood pulps for different combinations of
DZ and ZD sequences(Colodette et al. 1999).The effluent data exclude the oxygen delignification
stage.As shown, the effluent color was in many cases slightly higher for the ozone containing
sequences than for the conventional DEopDD sequences.The main environmental impact from the
ozone stage was a reduction in the AOX discharge.The viscosity,of the pulps bleached in the ozone-
containing sequences was lower than the conventionally DEoPDD bleached pulps.
Table 4.5 Ozone Bleaching Laboratory Study Results on Softwood ZD and DZ Combinations
(Colodette 1999)
Total C103
Kappa 03 C103 Field. Bright Bright. COD
Factor kg/OD kg/O kg/kg .% Revers. vise. kg/O Color AOX
Sequence lst Stage t Dl 03 ISO %ISO tnPa.S Dt kg/ODt kp/ODt
Western Canadian
Spruce/Pine(Kappa 18.9)
OD(Eor)DD 0.24 0 26.8 - 90 87.2 19.9 46.1 38.5 0.83
O(DZ)(Eor)DD 0.11 3 21.2 1.87 89.6 86.1 14.6 44.8 44.8 0.48
O(ZD)(Fa,)DD 0.11 3 21.2 1.87 90 86.9 17.2 46.7 43.8 0.58
OD(OP)(ZE)D 0.18 3 16.7 3.37 901 87.3 18.8 45.5 42.5 0.52
Southern Pine A(Kappa 12.9)
OD(EOP)DD 0.24 0 20.1 - 90 87.2 15.9 30 27.8 0.53
O(DZ)(EOP)DD 0.11 3 16.8 1.1 90.3 86.5 12.2 27.3 28.1 0.2
O(ZD)(EOP)DD 0.11 3 16.8 1.1 90 87.1 13.4 29.4 29.3 0.32
OD(EOP)(ZE)D 0.14 3 14.9 1.73 90 87 14.7 29.2 28.7 0.28
Southern Pine B(Kappa 11)
OD(EOP)DD 0.24 0 16.5 - 90.3 87.3 17.1 27.5 23.1 0.47
O(DZ)(EOP)DD 0.11 3 13 1.17 90 86.4 12.7 26.8 24.8 0.17
O(ZD)(EOP)DD 0.11 3 13 1.17 90 86.9 14.1 27.3 25.4 0.27
OD(EOP)(ZE)D 0.11 3 12.2 1.43 90.3 87.1 15.2 27.4 24.2 0.23
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20 Technical Bulletin No. 919
Laboratory tests by Liebergott for softwood pulp with kappa 29.5 gave the results included in Table
4.6 for impact of an ozone stage on color(Liebergott 1995).
Table 4.6 Comparison of Effluent Data for Ozone and ECF Bleaching,kg/ADt
AOX COD BOD Color
Dtoo Eop 1.8 44 16 40
ODtan Eop 0.5 23 6 14
D/Z50 Eo 0.17 42 13 38
OD/Ze5 Eo 0.10 31 8 19
Based on the two tables above,the use of ozone did not reduce the bleach plant effluent color
compared to the conventional ECF sequence,DEopDD,when the bleach filtrates were not recovered.
Table 4.7 documents similar data for hardwood(Eucalyptus)pulp for the sequences O-DEopDD,
OQOP-ZEDD (Z-ECF)and OQOP-ZQPO(TCF).The effluent data include stages starting from the D
or Z, i.e.,the study assumed that the effluents from the O(single stage oxygen delignification)and
OQOP (double stage oxygen delignification)stages were recovered.
Table 4.7 Ozone Bleaching Laboratory Study Results on Hardwoods(Colodette et al. 1998)
Effluent Kraft Kraft- tuft_ Modified Modified
ffora Kraft AQ Polysulfide PSAQ Conuue= Batch Kraft
Kraft
{ Brown Stock Kappa 18.2 17.4 17.9 17.2 17.2 16.8
\/ ODEooDD(ECF Sequence)
Kappa after 10.9 10.4 10.5 9.8 10.4 10.4
Color Ib/ADT DEopDD 13.8 12 16.4 17.2 17.6 17.8
COD Ib/ADT DEopDD 34.4 41 44 41 40.6 36
(00)(OP)(ZE)DD(Z-ECFsea)
Kappa after OQOP 10.3 10.0 10.0 95 9.9 9.8
Color Ib/ADT (ZE)DD 11.6 11.8 13 12.8 13.6 13.8
COD Ib/ADT (ZE)DD 34.8 34.4 31.8 30.6 31.8 31
00)(OP)(ZO)PO(TCF Sao.)
Kappa after OQOP 10.3 10.0 10.0 9.5 9.9 9.8
Color Ib/ADT (ZQ)(PO) 8.2 7.8 8 8.2 8 8.4
COD Ib/ADT (ZQ)(PO) 67.6 65.2 66.6 64.2 63.6 65.8
The data in Table 4.7 indicate that the color from hardwood bleaching using the Z-ECF sequence is
only slightly lower than using ECF for the conventional kraft cooks,taking into account the
difference in kappa before the D or ZE stage. The color from the TCF sequence was lower.Another
feature was the difference in color for the different cooking processes,indicating a higher color from
pulp cooked in modified processes compared to conventional cooks. The COD of the TCF sequence
effluent was about double that of the ECF sequence in this study.Other parameters differed between
the bleach sequences as indicated in Table 4.8.
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Technical Bulletin No. 919 21
Table 4.8 Comparison of Bleach Sequences (Colodette et al. 1998)
Parameter Unit ECF Z-ECF TCF
Pulp Yield %in final bleaching 95.6 95.4 95.1
Viscosity dm'/kg 983 960 877
Tear Index at 40'SR mNm'/g 9.61 9.99 9.37
Tensile Index at 40'SR mNm2/g 98.0 93.5 100.6
PFI rev at 40'SR 2537 2659 2987
Relative Chemical Cost 110 119 159
Relative Steam Cost 100 131 147
Effluent AOX kg/t 0.251 0.116 0
Munro and Griffiths reported the impact of a ZD stage on color.Mill data from the Domtar Espanola,
Ontario mill documented a significant reduction in color with the modernization and installation of an
ozone stage on the hardwood line(Munro and Griffiths 2001).No data for the bleach plant color was
however made available,only color in the total mill effluent,including softwood and hardwood line,
where a 27%reduction in color was reported.
Based on the information in Tables 4.54.7 it can be concluded that the benefit of using ozone is most
significant for the AOX discharges.The situation changes if the bleach filtrates are recovered(see
Section 6.2.3).
The chelating agents such as ethylenediaminetetraacetic acid(EDTA)and diethylene-
\� triaminepentaacetic acid(DTPA)normally have to be used in connection with ozone and peroxide
bleaching because of their ability to suppress the activity of the dissolved transition metal ions
without precipitation("Q").These metal ions are able to catalyze the decomposition of the bleaching
agent hydrogen peroxide into radicals.Totally chlorine free(TCF)bleaching is currently only
possible by treating the pulp with Q before the ozone and hydrogen peroxide stages.Increased
concentrations of Q are therefore found in wastewaters generated from the production of TCF pulps.
Although EDTA is non-toxic to mammals at environmental concentrations,there is some concern
about the potential of EDTA to remobilize toxic heavy metals out of sediments and the difficulties in
biodegrading this substance.
4.4 Peroxide in Bleaching
In recent years,hydrogen peroxide has been used extensively in ECF bleaching sequences as a
reinforcing chemical in alkaline extraction stages.In TCF bleach sequences,oxygen delignification is
usually necessary prior to hydrogen peroxide stages in order to obtain desired brightness levels.Also,
in the absence of an acidic D stage, the purging of transition metals (which deactivate peroxide)has
to be accomplished some other way.
4.4.1 Peroxide in the Eop Stage
The use of peroxide in sequences like ODEoeDD or ODEOpDEpD represents the conventional ECF
bleaching technology.A recent survey showed that both alkali and peroxide were used in the
extraction stages in 90%of the industry(Pryke,Kanters, and Tam 1999,2000).About 0.2-0.5%
peroxide is normally added, in many cases to a pressurized"tube"with short retention time.Peroxide
application in the E stage in addition decreases the color of the alkaline filtrate by 10-30%.
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22 Technical Bulletin No. 919
Several options exist for optimizing the EoP stage for reduced environmental impact. These options
include optimizing the temperature,reaction time,and hydrogen peroxide charge,metals management
through chelation or acid stages, and the addition of magnesium or other peroxide bleach stabilizers.
Increased hydrogen peroxide charge was used at the Leaf River mill to meet the color limit under
extreme low river flow conditions(Smith and Walley 2002).The mill established an internal target
for the effluent color corresponding to 500 pcu(-21 kg/ADt,42 lb/ADT).This target was met by
modifying the bleach plant operation.Hydrogen peroxide was added to the two extraction stages,
changing the bleaching sequence from DEoDED to DEOpDEpD.The showers on the first two
chlorine dioxide stage washers were also changed,replacing the fresh water with additional caustic
extraction filtrate. This took all the flow that was going to the caustic sewer and recycled it back
through the extraction stage. The main costs were doubling the hydrogen peroxide usage. Increased
depositing of barium sulfate on the first chlorine dioxide washer was another result.Annual cleanup
of the deposits will be required.
4.4.2 Peroxide in TCF or ECF Light Bleaching
Peroxide can also be used as the dominant bleaching chemical in TCF and Low CI02 ECF(ECF-
light)sequences.
Several mills have used various peroxide bleaching sequences,some examples of which are seen
below.
• OQPP
• OQPZP
• OQPPP
• OQPDEpD
• OQPoPQP
The last sequence listed,TCF sequence OQPoPQP,was used at the Louisiana Pacific(currently
Evergreen Pulp Inc.)mill in Samoa,California.Brightness levels on the order of 85+were achieved
while maintaining pulp strength equal to that of the original chlorine compound bleached product.
The total effluent color with the open bleach sequence was reportedly about 200 PCU for an effluent
flow of around 100 m3/t(15 MGD)corresponding to 40 lb color/T(Louisiana Pacific 2000).
Currently,the mill produces unbleached pulp(Yolton and Patrick 2005).
Another development in peroxide bleaching.has been pressurized peroxide(PO or EoP).Typical
peroxide stages operate at atmospheric conditions at temperatures between 80-90°C for long
residence times (four hours or more),while the pressurized stages can have residence times of 15-60
min.
Two examples of ECF-light bleach sequences which incorporate pressurized peroxide stages are
OQ(PO)DND and ODEoPD(PO).The benefit of the first sequence is that the(PO)filtrate can be
recycled to post-oxygen washing with fewer chloride issues,while with the second,the need for a Q
stage is eliminated.
Both non-pressurized and pressurized peroxide stages are now well established both in ECF and TCF
bleaching.Table 4.9 lists examples of peroxide bleaching applications.
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Technical Bulletin No. 919 23
Table 4.9 Examples of Full-Scale Peroxide Bleaching Installations
Mill Bleaching Sequence Wood type
Munks36,Aspa,Sweden' TCF OQPPPP'
SCA,Ostrand,Sweden TCF OQ(PO)(ZQ)(Po) SW,HW
Stom-Enso,Nornsundet,Sweden' TCF OQEoPQ(PO)' SW
Sodm,Monsteras,Sweden TCF OQ(oP)(PaaQ)(oP) SW,HW
Sodm,Morrurn,Sweden TCF OQEoPQ(PO) Sw,H W
Sodm,Varo,Sweden" TCF OQEoPQ(PO) sw
Rotmeros,Vallvik,Sweden TCF OQPaaQ(PO)PPP' sw
Stom-Enso,Kemi,Finland' ECF OQO(PO)DEpD SW,HW
Stom-Enso,Uimahariu,Finland' TCF 0QPPaaP' HW
Metsil-Rauma,Rama,Finland TCF (o0)(ZQ)P(ZQ)(PP) sw
Snails,Karim,Finland' TCF (00)QEoPCW SW
UPM-Kymmene,Lappeemanta,Finland' TCF (00)QEoPQ(PO)P' sw
UPM-Kymmene,Lappeenranta,Finland' ECF (00)(ED)DEorD sw
UPM-Kymmene,Pietarsaari,Finland' ECF ODEoPDP SW/HW
UPM-Kymmene,Pietamami,Finland' TCF OQZIQOPZIOP' SW/Hw
Evergreen Pulp,Samoa,CA TCF4 QPoPPP sw
Stoa-Enso,Skoghall,Sweden ECF O(OP)DQ(OP) SW,HW
Votorantim Celulose a Papal(VCP),racarei Mill, ECF OAZEDP HW
Brazil
ZellstoffStendal,Germany ECF OQ(OP)D(PO) sw
CIA Suzann Bahia Sul,Brazil ECF Do(PO)D,
'Main product is ECF pulp. also uses Pas `Sequence when producing TCF;main product is ECF "Currently unbleached
Note that there is some overlap in the definition of the two processes.Many of these mills can
produce both ECF and TCF pulp. Only the S6dra mills and the SCA Ostrand mill in Sweden and the
Metsa-Rauma mill in Finland produce TCF only. The other mills produce mainly ECF pulp,but can
produce TCF on demand.
The risks associated with peroxide bleaching processes are lower pulp strength and reduced optical
brightness.
4.4.3 Environmentallrnpact
Peroxide bleaching reduces effluent color if it is used early in the bleaching process.Therefore,
peroxide bleaching could have a significant impact on color,while a(PO)stage at the end of an ECF
bleach sequence would have almost no effect.However,in the early stages of the bleaching peroxide
can also impair the pulp strength and yield. Since nearly all installations are in Scandinavia where
effluent color has not been an issue of concern,there are unfortunately no data available to allow
precise estimation of color reduction(e.g.,when comparing conventional ECF bleaching and
peroxide based TCF bleaching).
If the peroxide stage effluents were recovered back to brown stock,the color reduction potential
would be even higher. AOX will be reduced as the C102 usage is lowered in an ECF sequence.
However,the BOD and COD will be increased as a result of a higher use of peroxide,if the filtrate of
the peroxide stage is not recovered.
In conclusion,use of peroxide stage in an ECF bleaching sequence reduces the bleach plant effluent
color,and more so if the peroxide or Eop-stage filtrate is recovered.
4.5 Peracid Bleaching
4.5.1 Process and Applications
Peracids can be used in both oxygen delignification and bleaching stages. Peracids have a high
selectivity for lignin and can be used as a partial or complete replacement for chlorine dioxide.
Peracids include peracetic acid(Paa) or CH3C000H, and Caro's acid or CaP=(Ca)H2S05-Peracid is
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24 Technical Bulletin No. 919
currently used in several Nordic mills.Peracetic acid is manufactured as a distilled product from
acetic acid and hydrogen peroxide.It is mainly used in TCF bleaching sequences (TCFpaa)where
higher brightness has been achieved,as well as improved strength, when compared to peroxide- or
ozone-based sequences.The recirculation of Paa-stage effluents could be a possibility in order to
further reduce effluent color.
All full-scale applications include a chelating stage prior to the Paa stage because the hydrogen
peroxide in the peracid solution generates hydroxyl radicals. Without chelation,the peroxide
consumption would increase:In the Rottneros Vallvik mill in Sweden,the peracetic acid bleaching
stage is operated at 60°C for a 3-hour retention time, and is followed by second chelating stage with
no intermediate washing.The Vallvik mill does not have biological effluent treatment.Effluent color,
however, is not reported. The COD discharge in 2005 was 41 kg/ADt(821b/ADT) and the AOX
discharge was 0.11 kg/ADt bleached pulp(0.221b/ADT) (http://www.rottneros.se/
page_l 5.aspx?epslanguage=EN).
Bleaching with peracids is a proven technology. It is practiced in full scale at several Nordic mills,
listed in Table 4.10.Many of the mills listed in Table 4.10 predominantly produce ECF pulp,but
have the capability to make TCF pulp on demand.Mill-scale trials with peracids have been conducted
at many more mills,including Munksj6/Aspa in Sweden and the Stora-Enso mill at Norrsundet in
Sweden.The kraft mill in Stendahl, Germany also has the option of using a Paa stage in place of its D
stage,but this is not currently done.
The bleach sequence at Sodra in Monster's, originally QI,OP,Z(Q),PO,was modified in 2000 by
replacing the ozone stage with a Paa-stage. (Sodra Cell,2002). The peroxide stage is a Prepox stage.
Bleach plant washing is done in a press(after pre-bleaching),two vacuum filters in parallel(after the
Q stage)and three Kvaemer wash presses following the OP,PaaQ,and PO stages.The bleached pulp
is then screened,cleaned,and dried in two Flakt dryers.
The Sodra Vdr6 mill also used Paa in bleaching(Sodra Cell 2002).
Table 4.10 Full-Scale Peracid Bleaching Installations
Mill Peracid used Sequence Wood type
Rottneros,Vallvik,Sweden' Peracetic OQPaaQ(PO)PPP Softwood
Stora-Enso,Kemijd vi,Finland' Peracetic (XQ)(00)PPaaQP Softwood
Stora-Enso,Uimaharju,Finland' Peracetic OQPPaaP Hardwood
Sunila,Kotka,Finland' Caro's Acid (00)QEOpCaP Softwood
Stora-Enso,Oulu,Finland' Peracetic ECF main sequence S WD/HWD
Sodra,Var6 Peracetic TCF Softwood
Sodra,Monster's Peracetic TCF SWD/HWD
Zellstoff Stendal,Germany' Peracetic OQ(OP)Paa(PO)or Softwood
OQ(OP)D(PO)
a Main product is ECF pulp with some chlorine dioxide use.
4.5.2 Risks
Peracid bleaching may not be compatible with all pulp quality parameters.It has been applied in TCF
bleach lines with the purpose of improving brightness and strength.An environmental risk would be
increased BOD and COD in the effluent caused by the acetic acid,unless Paa stage filtrates are
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Technical Bulletin No. 919 25
recirculated back to brown stock washing.As shown in Table 4.10, all known sequences utilize the
chelating agents (Q) in order to accomplish bleaching to high brightness levels.
4.5:3 Environmmntallntpact
The Paa treatment can be carried out with both equilibrium(ePaa)and distilled acid(dPaa),although
the optimum pH differs(ePaa pH 4-5; dPaa pH 5-8). The main difference is the higher effluent load
when using ePaa as illustrated in Table 4.11.
Table 4.11 Effect of ePaa and dPaa-Stage on Bleaching Effluents
(Vuorenvirta,Panula-Ontto,and Fuhrmann 1998)
Stage/Paa charge Unit CODc, TOC Oxalic Acid
ePaa/10 kgBDT 27.9 8.6 0.08
P kgBBDT 7.9 3.5 0.08
ePaa+P,total kgBDT 35.8 12.1 0.16
dPaa/10 kgBDT 13.5 5.7 0.03
P kgBBDT 7.2 2.7 0.07
dPaa+P,total kgBDT 20.7 8.4 0.10
dPaa/5 kgBDT 8.9 3.8 0.02
P kgBDT 7.7 3.1 0.08
dPaa+P,total kgBDT 16.6 6.9 0.10
{
In addition to the reactions of the peracids with lignin,peracids have been found to react with the
hexenuronic acid(HexA)by oxidizing it to smaller compounds.The peracids have been reported to
actually degrade HexA faster than lignin.Removal of the HexA prior to peracetic acid treatment in an
A-stage(acid hydrolysis)would result in more selective bleaching and reduced peracid consumption.
Since most of the installations and trials have been carried out in Nordic countries where effluent
color is typically not regulated,there is very little information available on the impact on color.Early
laboratory studies have indicated that peracids applied to effluent reduce color to the same extent that
peroxide does,which would suggest that a Paa stage would behave similarly to a peroxide stage.
If Paa effluents were recirculated back to brown stock washing,the effluent color would be reduced.
Because of the acetic acid used,effluent BOD and COD would rise unless the effluents were
recirculated back to brown stock washing.
5.0 COLOR MONITORING
Monitoring of the color is essential for color control.
Although color is a property of the specific effluent sources in a mill,it is customary to calculate
color as a mass load so that a mass balance could be developed for the colored streams in the mill and
for the total treatment plant influent.Many mills have documented a balancing problem, and it is
generally believed that the color of the in-mill sources changes in nature on its way to the effluent
treatment plant,increasing the color of the sources.This so-called color amplification has been
attributed to the presence of sulfide,green liquor dregs,pH,mixing issues,anaerobic conditions,etc.
In essence,it is largely unknown what causes the color amplification or how extensive it is.
�J
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26 Technical Bulletin No. 919
It is,however, essential for color control to establish an in-mill color balance as detailed as possible to
understand the color sources.After that, an appropriate color measurement and monitoring system
can be set up so that color sources can be monitored on a sufficiently frequent basis.
Most mills monitor the bleach plant filtrates and black liquor sources separately.For black liquor,
conductivity is frequently used as a substitute for color. In areas where the color losses are due only
to the presence of black liquor,the color mass can be estimated when the typical color/conductivity
for black liquor is known and the effluent flow(see Table 3.1).
An essential part of the color monitoring would be directed to monitoring spills and spill handling
systems.Monitoring for control of black liquor spills is described in the following section.
Monitoring of washing losses and other regular black liquor originated sources as well as kappa
number variability should also be part of the color monitoring.Variation in washing losses and kappa
numbers are reflected in the bleach plant effluent loads.
Blue Ridge Paper Products(Blue Ridge 2006)is using an extensive in-mill monitoring system to
manage and detect black liquor and bleach filtrate losses.Their monitoring system includes
2 hr color monitoring of influent color(1 hr monitoring during upsets and outages);
• in-mill daily color source balance with color measurements in about a dozen in-mill effluent
streams;
• alarms for sewer conductivity,liquor tank level,and filtrate tank level;
• redundant overflow alarms for black liquor and spill containment tanks;
�i • real time sewer conductivity and color trend data for mill sewers available at process operator
control stations;
• action levels for process operators for color in influent and mill sewers from each production
area; and
• daily process control trend charts for color in mill sewers and waste water treatment.
The detailed color balance developed on a daily basis is essential for maintaining low color loads at
that mill.
6.0 RECOVERY OF COLORED WASTEWATERS
6.1 Black Liquor Spi11 Recovery
The Cluster Rule promulgated by the U.S. Environmental Protection Agency(EPA)in1998 includes
requirements for mills to implement"best management practices"(BMP)plans.These,in effect,are
spill control systems for black liquor,turpentine, and soap.To comply with this rule,the mills must
record variability of effluent before treatment and take corrective action to reduce peaks.The rule
leaves decisions on control criteria to mill management. The chosen control criteria typically are
conductivity,COD,or TOC,but some of the study mills in this survey have chosen to use color as
BMP control parameter.
The prime target for most spill control programs is black liquor. Soap and turpentine can cause
catastrophic spills that drastically reduce the performance of the biological treatment,and these types
of spills have to be prevented by enclosure in accordance with the BMP.
L
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Technical Bulletin No. 919 27
Black liquor spills,however,are difficult to completely prevent, so black liquor loss(spill)control
q P� P Y P � q � P� )
programs include both prevention of spills and recovery of spills.
6.1.1 Contribution of Spills to Effluent Color
Task II of this report addresses the contribution of black liquor losses to the influent color in the
actual study mills in this survey.
Data illustrating influent color variability in three mills published by McCubbin(McCubbin 2001a)is
shown in Figure 6.1.
US N Wilk calnr;at intimmit to WWTP fc*No 8
w
:s
w w ea_ m is
m . . NlY color atkAwt(aWINITfor Nil
140
A
m
its, d� GailywdorgRirilluwdloWWfP JIYLL. . ,..
iao
�m
40
0 -_ W - M, W we 1w 1w
Figure l:Daily color flow for three different mills
Figure 6.1 Daily Color for Three Mills(McCubbin 2001 a)
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28 Technical Bulletin No. 919
"The graphs represent six months of daily color flows for three mills, expressed as
kilograms of color per average ton of pulp production at the treatment plant influent.
The mills are similar. The principal difference is the execution of the spill control
programs.All mills have two fiber lines. The mills have paper machines built before
1940 and are located on severely restricted sites with far from optimal layout of the
equipment and sewer systems.
All three mills have complete coverage with spill recovery sumps,and a number of
conductivity monitors with data display and alarms on the operator's control panels.
Management at all three mills believes they have excellent control of spills.In the
author's view,the performance of the systems shown ranges from average to
excellent. Clearly the staff at mill S is the most effective at controlling spills."
(McCubbin 2001)
Assuming that the peaks in the charts in Figure 6.1 are due to spills,one can draw the conclusion that
significant spills could double or even triple the daily average influent color compared to the normal
operation in the mills included in that survey.
Some variability in the influent daily color is caused by variability in the process operation.Variable
production rate,kappa number,brown stock washing efficiency,and bleaching conditions impact the
influent color,but likely not to the extent shown in mill C and L in Figure 6.1.
6.1.2 Black Liquor Spill Management
Spill discharges consist of foam, leaks,tank overflows, failures in pump seals,unauthorized draining
of equipment for repair, etc. Spill in the form of foam is probably the most difficult to handle,because
of the consistency.Foam can occur in large volumes,causing overflows and problems transporting
the spill through the usual spill collection system. Combined with the fact that spill is by definition
diffuse,the exact amount of spill discharge is often difficult to estimate.
A good spill management system includes measurements and monitoring,spill prevention,spill
collection,and lastly,spill equalization to reduce impact on effluent treatment and level out
unavoidable spills.
6.1.3 Spill Prevention
Important features for spill prevention include the following.
• Operating philosophy. Steady production and process conditions always result in lower
process discharges compared to variable conditions. This of course requires appropriate
instrumentation and control,but also the correct set points for e.g.,production and operating
conditions.Both from production and discharge point of view it is often more beneficial to
target e.g.,a manageable production level that can be steadily maintained than to target too
high production that causes equipment overloads,downtime and variability,overflows,and
uneven operation, all of which can result in a lower average production.
• Operator and maintenance personnel training. According to McCubbin(McCubbin 2001a)
the principal difference between the three mills in Figure 6.1 is operator skill and attitude.
Education and training of process operators in understanding the process operating
parameters that impact effluent color is important for the prevention of spills and reduction of
variability.Training and education of types and sizes of spills and the impact of spills on
color is an essential part of spill management to reduce the frequency and magnitude of the
spills.
National Council for Air and Stream Improvement

Technical Bulletin No. 919 29
"Training programs should be tailored to the mill's specific systems,and to the level of
knowledge of the personnel.Training should explain the key parameters,and how the
department worked in affects the effluent discharge.Each piece of equipment or operating
procedure that can generate spills should be identified and explained,and corrective action
defined.In all cases,training should encourage feedback from operators and maintenance
people, since they know many local details well.A good spill control system provides
operators with continuous,rapidly updated data on key factors of plant operation. Operators
must understand these data,be able to diagnose causes,and take corrective action.Initial
training requires several hours of class time for each student,with a couple of hours as a
refresher each year for most operators and maintenance personnel. Continuous feedback
helps workers learn from mistakes.Mills where spills are controlled successfully normally
have a report of all major incidents at daily production meetings,and advise all operators in
relevant departments about what happened and how to avoid repeat incidents."(McCubbin
2001b)
• Maintenance of equipment. Many mills perform daily rounds to check condition of
equipment,piping,and pumps for leaks.
• Instrumentation and control. Reliable instrumentation is very important for spill prevention.
Level measurements with alarms on liquor tanks alert the operators about potential situations,
so that overflows can be prevented. Conductivity or temperature measurements and alarms on
overflow pipes and in locations where equipment failures might occur are important to alert
the operating personnel about spills so that preventive actions can be taken quickly.
• Cascading of tank overflows and adequate filtrate and spill collection tank volumes. Most
large spills occur when tanks overflow.
6.1.4 Spill Collection and Recycling
One important feature of a spill control system is to collect the spills,e.g.,tank overflows,before they
reach the floor drains.A modem brown stock line with oxygen delignification typically has at least
six liquor filtrate tanks that are coupled for countercurrent washing via the wash filter showers.When
imbalances in these long systems occur,the result may be an overflowing tank.Rather than
overflowing to the sewer and to the spill collection system,some mills have cascaded the overflows
countercurrently to the preceding liquor(or fiber)tank. That way,any extra dilution is avoided and
the overflows are recovered closer to the source.Where tank overflows are a problem,an overflow
detector is useful. Some mills monitor temperature in the overflow pipe,since this will detect foam
overflows that fail to show on the tank level monitor.
The spill recycling system with drains,sumps,and spill tanks should collect spill and directly recycle
it back to the process,preferably as close to the spill source as possible(Lundstrom,Berglin,and
Annergren 2002).Recovery pumps are often installed in all sumps that receive spill.These pumps are
activated automatically,when highly contaminated spill is collected in the sumps so that the spill can
be transferred to a spill collection tank. Conductivity is often used to estimate the contamination in
spill. If a large amount of water is recycled,it can cause overload in the evaporators,to the point that
operators have to deactivate the spill recovery system(McCubbin,2001b). Uncontaminated water
also dilutes the contamination in spill,which can cause significant amounts of discharge to pass the
recovery pumps undetected. It is therefore important not to mix uncontaminated water into the spill
recycling system. Other important factors in the spill recycling system are outlined below.
• Sufficiently large spill tanks with the capacity to collect even large spills.
National Council for Air and Stream Improvement

30 Technical Bulletin No. 919
l '
• Sufficiently large pipes that can quickly regulate any imbalance in the system.
• Appropriate number of spill sumps throughout the mill. Simple, single line mills typically
require 3 to 6 sumps,though some mills require a dozen or so.Actual requirements are very
site-specific,and usually involve some compromise between the ideal configuration and the
costs of retrofitting.
• Continuous measurement of conductivity in each sump and operating area of interest.
Locations should be selected so that they will serve to locate spills in a reasonably small area
(such as an evaporator set or the digester department)all under the control of one operator.
• An appropriate choice of conductivity limit in the sumps to activate spill recovery pumps.
• Recovery sumps on knot reject bins.
• Mechanical pump seals in black liquor areas to avoid clear water dilution of color materials
that prevents efficient recovery.
Specific conductivity is the most successful parameter in current use for continuous monitoring for
black liquor spills.It will also detect spills of white and green liquor,and usually soap(because some
black liquor normally travels with soap). Spills have to be monitored instantaneously by conductivity
or other continuous sensor,at multiple points,to initiate appropriate corrective responses.A longer-
term assessment is also useful,particularly to benchmark against other mills. COD and color are
useful for such assessments.
The conductivity limit for activating spill pumps or rerouting an in-mill sewer or floor drain to a spill
collection system eventually determines the black liquor losses to the effluent.In North America,
most mills consider that an effluent stream should be pumped back to the black liquor system when
the conductivity exceeds 5000 micromhos/cm(µmhos).This corresponds to a black liquor
concentration of about 0.5%,although some mills have set points for recovery at 2500 µmhos
(McCubbin 2001a).A lower limit was employed in a Swedish mill where the usual limit was 150
mS/m or 1500 µmhos.That limit is increased to 175 mS/m(1750 µmhos)during shutdowns or in
cases of large temporary spill events,to ensure that as much high contaminated spill as possible is
recycled(Lundstrom,Berglin,and Annergren 2002).
When taking into account the typical ratio color/conductivity of black liquor(1-4 PCU/µmhos) (see
Table 3.1),the color contribution of a spill can be approximately calculated,if the volume of the
black liquor spill is known.
The recycling of a spill also has an economical value,because chemicals and energy are lost with the
black liquor solids and need to be replaced. On the other hand,the water with the spill has to be
evaporated which consumes energy.To minimize the cost it is again important to separate clean
waters from black liquor floor drains that are connected to spill sumps.
6.1.5 Example of an Optimization of a Spill Collection System
The spill collection system in each mill has to be optimized individually for the specific
configuration,layout, floor drain,and sewer layout.
A Swedish investigation studied the spill system in an existing mill(M6nsteras,750000 ADt/year
bleached market kraft pulp)and established an improved concept based on a dynamic simulation of
the fiber and liquor systems (Lundstrom,Berglin, and Annergren 2002).
A schematic structure of the existing fiber line and spill recycling system is shown in Figure 6.2 (Part
1).The filtrate tanks in this mill are connected such a way that the filtrate in one tank can be directly
National Council for Air and Stream Improvement

Technical Bulletin No. 919 31
transported to the next tank. This structure reduces the risk of overflow of filtrate from these tanks.
The maximum allowable level in the blow tank is—80%.At higher levels the operators reduce the
inflow from the spill system to reduce the risk of overflow. The total volume of the spill tanks on the
brown stock side(Tanks 1,2, and 3)was 230 m3 or 60,000 gallons.
Three typical types of spills were simulated:
• leaking pipe(10 Us or 160 gpm leak for 16 hours at the end of the brown side);
• emptying a wash filter(filter in the screening position plugs and has to be empted fast);and
• a major tank overflow(a 500 in or 130 000 gallon overflow from the blow tank flushed
down with water so that the pulp in the floor drain had a I%consistency).
The present spill recycling system in this mill was good,but dimensions were not sufficient to cope
with all the simulated spill cases. Suggestions for improvements to the spill recycling system that
were identified in the study are shown in Figure 6.2(Part 2).The suggested improvements are
outlined below.
• Replacing of Spill Tanks 2 and 3 with a new 2000 m3 (510000 gallon)tank.The size was
chosen to ensure that all highly contaminated spills from the simulated cases were collected.
• New pipes from both sump 1 and spill tank 1 to the new spill tank.
• A seal that automatically shuts down the inflow of spill when the volume in the blow-tank
exceeds 80%,to reduce the risk of overflow.To quickly control changes in the spill recycling
system,the dimensions of the pipe between the blow tank and the new spill tank were such
that a flow rate of 150 Us(-2400 gpm)could be handled.
• A separate system for clean water or water containing low levels of contaminants,to reduce
the dilution of the spill recycling system.
With these improvements,the simulation showed that even a significant blow tank overflow could be
collected so that the average daily COD discharge from black liquor remained around 1 kg/ADt, (2
lb/ADT)compared to an increase by 12.4 kg COD/ADt(25 lb/ADT)in the existing mill case.
The simulated improvements in COD discharges are shown in Figure 6.3.
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32 Technical Bulletin No. 919
WZj
caparay asaad 1,NWne
Blawlarik IlClower
Dig..W-►new[e<--► -► i Oargen
bea[bngi Qi i
1 . 1
1
FgnbT..k Fquuu.k S u auk Fibula unk FBLme,enk
gralm
cmaanea.e,Lw[-asgms/m cmrau.Awvuma-150au^/m
'••••••••••••••► Sump1 •••: rscm6vm �—�«— Sump2 E�� Spill Aom
Screeruig t� Nea[bplaM
eiu.gical SPill,ankl SdA:mk2 SPAIu*3 SpiA mNoa
' Treatmem '
c.p.-V 30 3 100w3 IOC. 13kr2
Figure 1. A schematic figure of the fiber line and the spill recycling system in the mill. The location of the
three spill cases can be seen in the figure. Numbers refer to the three spill cases: (1) leaking pipe, (2)
emptying of a wash filter,and(3)tank overflow.
capeedy v000 xo.gP.d
BI.I.Pk
-
1 1 1 1
FA O.Tarik FAraie tvW e a FigralnaPk FigmeuM
PW
P••Sepanumolpelpene lmrve^A Fgndc
ONna
a I.amvrmlbw:l3g1(i. a
Pv,caee,Apmean q�
cenaamwyume-uooslm . ...Lehi....... !•7 cn.enawv,:.,n.a.oes/m
a. � SumP2 ~— h4acbPlaa
�SpAt h.m fapaM'20Pp� Cey.eS0135n,3
Smmmq I ay].s5m1
euleginl � SPJI iaNl
Tuwnam Copaay3ortl
Figure 2:Proposed changes at the mill to improve the spill recycling process.
Figure 6.2 Example of a Simulation of a Fiberline Spill Collection System
(Luudstrom,Berglin,and Annergren 2002)
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Technical Bulletin No. 919 33
Table 3:Comparison of dto original uul tiw impmFvd spill meycling systonxi
°Avomgo COD dischwgo during 24h to biological treatment(kg/AD[)
,t +'E"�"f'u^`° a ;` n Coiiltnnons iL' I<nkotn PlPc` JAL PtFlnS uta �'+� r Tm--
owl
Size of the scenario Normal day Small Medium Large
Orlglml spill recycling system
Dilution factor (m'?ADt) 2.6 3.8 2.8 2.7
Avemae COD discharg • 1-0 0.7 IA 12J
Proposed spill recyele system
Dilution factor (ae/ADt) 23 3.8 2.6 4.7
Average COD diselsu e- 1 0.8 1 0.5 1.0 12
Figure 6.3 Simulated Spill System Improvements (Lundstrom,Berglin,and Annergren 2002)
The study concluded that a spill recovery system that would reduce the black liquor spill discharges
from the fiber line to a mean level below 1 kg COD/ADt or about 2 lb color/ADT could probably be
constructed(at an estimated cost of 5.1 million SEK or about 0.6 million USD,2001)but not without
negative effects.Recycling of spill results in either a high dilution factor of material entering the
evaporators or deterioration in washing efficiency,followed by a larger amount of carry-over to the
bleach plant.To recycle as much organic matter as possible, the flow of clean water into the spill
system has to be kept low. To reduce the amount of water entering the spill system,a separate system
for uncontaminated water(seal water, cooling water etc.) can be built.Large temporary spill events
must also be avoided by spill prevention techniques to ensure a low total discharge from a mill.
6.1.6 Spill Diversion(Sewer Diversion)
Diversion of spills is often utilized in cases where spills escape the in-mill recovery systems and enter
the effluent stream. To reduce the impact on effluent treatment and a risk for exceeding e.g.,a daily
color limit, it is beneficial to have a back-up where the colored waters can be stored and slowly bled
into the treatment plant,or even slowly recovered into the process if the evaporation plant capacity
allows. The sewer diversion is typically managed via conductivity guards ahead of the diversion
system.Diversion for effluent color is most useful if the mill has a segregated sewer system so that
black liquor-containing sewers are separately monitored from other sewers. That way the conductivity
from elevated black liquor content can be separated from other high conductivity losses(white and
green liquor losses,ESP dust purges,demineralizcr backwashes,etc.).Because the effluent stream at
the treatment plant influent often has a high flow and also contains non-colored or less colored
effluent streams,the back-up volumes should be large(million gallons).
One study mill treats the diverted black color-containing stream in a spare primary clarifier batch
wise with polyamine,which separates the black color from the effluent. The sludge from the spare
clarifier is mixed with the primary and secondary sludge.
6.2 Bleach Plant Effluent Recovery
6.2.1 General
The recovery of bleach plant effluent in combination with the black liquor recovery cycle has been
the target of a long-time development effort. The introduction of the ECF and TCF technologies,
r
chloride and non-process elements removal processes,has enabled partial recovery of the bleach plant
effluents.
National Council for Air and Stream Improvement

34 Technical Bulletin No. 919
r-
`/ Kraft pulp bleaching alternates between acid and alkaline conditions.Modern bleach plants cascade
the water systems countercurrent to produce an acid effluent and an alkaline effluent from the first
two bleaching stages. The alkaline filtrate is compatible with the brown stock area from a pH point of
view;therefore,most bleach plant effluent recovery concepts include the use of alkaline filtrate in the
brown stock area. The first acid filtrate in the bleaching process contains the major part of metals and
minerals that are released and washed out from the pulp in the acidic conditions,and represents a
purge point for non-process elements that enter the process with the wood(green liquor dregs being
another major purge point).Recycle of the acid filtrate is not common.It is known to be in
continuous operation only at the Blue Ridge mill,as a partly closed system,and in the TCF bleach
line at the ASSI Doman,Fr6vi where the acid effluent(Q)is evaporated in a separate evaporation
plant(see Section 10).
6.2.2. Recycle of Filtrates in ECF Bleaching
6.2.2.1 Color in Filtrates
Table 6.1 summarizes effluent color data from the alkaline and acid stages of some of the ECF mills
participating in this study.
Table 6.1 Example of Color in Acid and Alkaline Bleach Plant Effluents in This Study(ADT=shT)
Acid Effluent Alkaline Effluent
Wood type Kappa Total Color
lb/ADT Flow, Color, Flow,m3/ADT Color,
m3/ADT Ib/ADT lb/ADT
HW 12.8 24.4 23.6 16.4 15.1 8.0
HW 17.4 37.6 21.5 27.0 4.5 10.6
SW 17.8 36.1 8.5 15.4 6.0 20.7
SW 16 55.4 27.1 22.9 18.8 32.5
SW 28 62.5 29.9 29.3 10.7 33.2
SW 22.6 67.5 43.3 26.1 12.3 41.4
HW 16.9 40.1 32 37 1 3.1
As shown in Table 6.1,the alkaline effluent contained only about a third of the bleach plant color
load in the two hardwood bleach lines,while in the softwood lines the alkaline filtrate contained 50-
60% of the bleach plant color.Note that the data in Table 6.2 do not take into account any
amplification of the color measured in the in-mill streams compared to influent color.This
phenomenon may cause an increased color load of the bleach plant effluent and may impact the acid
and the alkaline streams differently.
National Council for Air and Stream Improvement

Technical Bulletin No. 919 35
f
� e
6.2.2.2 Filtrate Recycle
The recycling of chloride containing filtrates from ECF bleaching is practiced in some mills.The
most extensive known recycle is at the Blue Ridge mill in Canton,North Carolina, where the Bleach
Filtrate Recycle(BFR)process for recycle of both alkaline and acid filtrate is employed on the pine
line and alkaline(Eop)filtrate recycle on the hardwood line. Another kraft mill using partial recovery
of the Eop filtrate is the Tembec Inc.mill in Skookumchuck,British Columbia.That mill has
announced a long-term plan for complete recovery of the Eop filtrate.
To achieve a significant color reduction from the Eop filtrate recycle, a substantial portion of the
alkaline filtrate needs to be returned to the liquor loop.
The presence of chloride in the alkaline filtrate is large enough to require chloride removal from the
liquor loop at substantial degrees of filtrate recycle in order to protect equipment from chloride
corrosion and especially the recovery boiler from plugging. With low degrees of recycle (< 10-30%),
a sufficient chloride amount could be removed by purging recovery boiler ESP dust, depending on
the mill chloride balance,but with more recycle of alkaline filtrate the installation of a chloride
removal process becomes necessary(Baxter et at.2004).
Removal of chloride from the liquor cycle can be motivated even without recovery of the bleach plant
filtrates, depending on the chloride intake to the liquor loop from other sources. Chloride removal
processes are discussed in Section 6.2.2.7.
The optimum process concept for recycle of the alkaline bleach filtrate is mill-specific and has to be
developed for each mill individually,taking into account equipment configuration in the bleaching,
brown stock, and recovery areas,chloride and potassium and other non process element balances,
color balances,washing efficiencies,effluent flows and composition, etc.
The following are risks o£E-stage effluent recirculation:
• build-up of chlorides,potassium and other NPE in the liquor system;
• increased foaming and corrosion in brown stock washing;
• higher recovery system loading;
• disruption of the sodium-sulfur balance; and
• new technology at very high recycle degrees in ECF.
The concept proposed for the Tembec Inc.Skookumchuck mill and the concept in operation at the
Blue Ridge mill are reviewed below.
6.2.2.3 Eop Filtrate Recycle at the Tembec Ina Skookanichuck Mill
One of the mills using Eop filtrate recycle is the Tembec mill in Skookumchuck,British Columbia.
This mill is a softwood market kraft mill with oxygen delignification and ECF bleaching.
Skookumchuck has been recycling 10-15%of its Eop filtrate back to the unbleached fiber line since
August 1996.The Eop filtrate has been returned back to the liquor balance tank between the decker
and the two-stage atmospheric diffusion washer and occasionally to the second post oxygen washer
filtrate tank. The chloride content of the liquor loop has been managed,albeit the white liquor
chloride concentration has increased.
The Skookumchuck mill has been working with Paprican of Canada to develop a progressive system
closure concept(Baxter et al.2004). One of the main objectives of the progressive system closure
J concept at Skookumchuck is to achieve 100%Eop filtrate recycle back to the second post oxygen
National Council for Air and Stream Improvement

36 Technical Bulletin No. 919
L washer.Limitations to increasing EoP filtrate recycle include brown stock washing operation,black
liquor evaporation capacity,chloride levels in the recovery cycle,and increased bleach plant chemical
consumption. On the other hand,sodium and dissolved solids would be recovered.
To achieve 30%EoP filtrate recycle, computer modeling done by Skookumchuck has shown that 3%
of the ESP dust must be sewered to prevent increased chloride levels in the white liquor. To achieve
100%EoP filtrate recycle,the following would be required at Skookumchuck.
• Chloride removal system for treatment of ESP dust to remove excess chloride that
accumulates in the recovery cycle. The planned system is an ion exchange system(PDP; see
Section 6.2.2.7)
• Reuse of black liquor evaporator condensate that is being displaced by the EOP filtrate.The
displaced condensate can be used to replace fresh water and reduce mill effluent flow.
Possible uses for the condensate are the bleach plant or pulp machine.Further treatment of
the condensate maybe required.
• Use of EOP filtrate on the second set of DO showers.This strategy is expected to lower the
volume and increase the concentration of the EOP filtrate being recycled to brown stock
washing.
To combat the side effects of filtrate recycle at Skookumchuck,several other projects would be
required to facilitate system closure.These include
• improvements in post oxygen washing;
• improvements in brown stock washing control;
• improvements in bleach plant control;
• water conservation;
• evaporator and recausticizer upgrades;
• installation of a chlorine dioxide generator acid purification and evaporation system; and
• installation of a sodium thiosulphate removal system to help control the mills chemical
inventory.
Figure 6.4 shows a block diagram of the processes involved,based on the description of the system
given in the literature(Baxter et al.2004).
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Technical Bulletin No. 919 37
Eop
Bleached
Pulp
ChipsBSW p Pulping 02 ell d D E Bleach Plant Pu l
H2Og Do Machine
Filtrate
OWL Thiosulfate ,i CIO,
removal
piocess
Na2S2O3 Bleach Chemicals Condensate
H2O preparation '.Polishing
Recovery
GAP C1O2 generator
H2O Na2S0JH2SO
PDP NaC1O3
H2SO4
NaCl
i Figure 6.4 Processes Involved in the Proposed Progressive System Closure at the Skookumchuck
Mill Based on the Literature(Baxter et al.2004)
The simulated impact of the proposed progressive system closure on the effluent,color and dissolved
organic material and on the chloride concentration of the white liquor is shown in Figure 6.5,based
on the published material. The mill effluent color was simulated to decrease by 50%with 100%Eop
filtrate recycle.The effluent flow volume at the mill was about 40 m3/ADt,so the resulting total mill
color discharge was simulated to be 40 m3/ADt*450 PCU or 18 kg/ADt(36 lb/ADt),without the
use of chemical treatment. Without 100%recycle,the mill effluent color would be about twice that
amount or 721b/ADt(without chemical treatment).
The implementation of the progressive system closure at the Skookumchuck mill is reportedly
currently on hold, so there is no information available with respect to the actual color reduction
achievable with the proposed system in operation.
I
National Council for Air and Stream Improvement

38 Technical Bulletin No. 919
L�
25 30
x20 -____________________________
a,
15 ____ 25 - ------ ----------- ______
., 20 ___________________ ______
0 a 15 __________________ _____ _
0 70
O Base 15%Eop 30%Eop 100%Eop °
t
Case recycle recycle recycle+ O 10
_ __________ ______
PDP
1200
U 1000 -- --------------------- 0
0
0 800 -- ----- ----------- Base 15% 30% 100 100
°u 600 ----- ------------ Case Eap Eop % %
5 400 __
W200 -- ----- ---- - Chloride concentration mwhite liquor with increasing Eop
0 filtrate recycle rate and after implementation of the PDP system for the
processing of40%ofteh ESP dusL 3%of the ESP dust is assumed to be
Base Case BSWISpill 100%Eop sewered in the 30%recycle case forchloride control.
Control recycle
Figure 6.5 Simulated Impact of the Progressive System Closure(Baxter et al.2004)
6.2.2.4 Eop Filtrate Recycle in Blue Ridge Hardwood Line
The Blue Ridge Paper Products mill currently recycles Eop filtrate on the hardwood line to reduce
effluent color.The recycling is possible because the chloride removal process is in operation at the
mill as part of the BFR process.A schematic of the hardwood line filtrate systems is included in
Figure 6.6.The estimated color reduction due to the partial Eop filtrate recycle on the hardwood line
is 5-7 lb/ADT of hardwood pulp(Blue Ridge 2006).
6.2.2.5 Bleach Filtrate Recycle(BFR)Process
The Blue Ridge Paper Products mill developed their bleach filtrate recycle(BFR)process to reduce
the effluent color from the pine line bleaching.The process enables recycle of the filtrates from the
first two stages of bleaching back to the kraft recovery cycle.There are three key components to their
process:
• oxygen delignification combined with 100%C102 substitution(OD100), in order to
minimize the impact of dissolved solids carryover to bleaching;
• a minerals removal process (NIRP)to purge metals from the fiber line by treating the first D
stage effluent; and
• A chloride removal process(CRP)to remove chloride from the recovery cycle by treating the
precipitator catch.
In the BFR installation the Eop filtrate is split in half,with part being used as wash water on the first
D stage and part sent to the post-oxygen washing decker seal chest.
National Council for Air and Stream Improvement

Technical Bulletin No. 919 39
�l
J The first D stage filtrate is also split,with part going directly to the post-oxygen washing decker
upper shower, and part being treated in the MRP.Treated D filtrate is reused as wash water on the
post-oxygen washing decker lower shower and the fast D stage shower. Only filtrate from the final D
stage would enter the sewer at complete closure of the system. Currently,the degree of closure is
around 75%. A schematic of the water systems in the pine line is shown in Figure 6.7.
The recycling of the bleach filtrates to this extent,including recirculation of both acid and alkaline
chloride containing filtrates,is possible because the mill has installed a minerals removal process
(MRP)and a chloride removal process(CRP).Minerals removal processes are discussed in Section
6.2.3.6 and chloride removal processes in Section 6.2.3.7.The mill maintains a certain redundancy in
these processes to achieve high uptime.
The BFR project reduced the final effluent color by about 12 lbs/ADT total pulp or about 28 lb/ADT
of softwood pulp(15000-20000 lb/d). Other environmental benefits would include reduced BOD,
COD,and AOX.
The BFR process generates two new waste streams: the ion-exchange backwash from the MRP, and
the chloride purge stream from the CRP.These streams have to be sewered in order to remove non-
process elements and chloride from the system.The recovery boiler is equipped with a direct contact
cyclone evaporator.Liquor droplets carried over into the flue gases have therefore resulted in a
colored purge from the chloride removal process.The color of the purge is about 5000 lb/d(3.5
lb/ADT)in the influent,but most of this color is likely to be removed in the effluent treatment plant.
Colored purge would probably not be an issue in a recovery boiler without direct contact evaporator.
The operating costs have been 10%higher due to filtrate recycle. Chemicals and energy would be a
major part of the increased costs.The MRP requires a sodium chloride regenerant.Recovery loop
U` makeup requirements would be impacted by the addition of sodium from the bleaching effluents and
by the amount of sodium lost with the purge from the chloride removal process (as sodium chloride,
carbonate and sulfate,in addition to the same salts of potassium).The net effect on the sodium-sulfur
balance and chemical makeup requirements would be very mill-specific, depending on the actual
sulfur-sodium-chloride-potassium balances.
The evaporation in the CRP process requires steam in an amount that depends on the selected
chloride removal process. There would also be a minor increase in power demand.
The main process risks with the BFR process include potential corrosion,scaling,and pulp quality
issues.
National Council for Air and Stream Improvement

40 Technical Bulletin No. 919
�l
1
Blue Ridge Paper Conlon Mill-No.1}{nrdW«d Fiber I.Ine end Bleach Plant Fiyllrale FIRw
y5W
nsw � � � ? x°
BMW � 1 1 1 1 1
aSW' Wa Ite GIB) b n2
� D¢ta Bkap
3 3 3 3 d
a5W1 BSW] 9NIl D W4 n,aw Re
Rha fJvua i"Jmu IBn.e FMw B� al. Froam rimaw
Tak Tsk TmY Ta Tvk iv Tmk Tvt Tmk
Tek
Eve-
Figure 6.6 Fiberline Filtrates at the Blue Ridge Hardwood Line
Blue Ridge Paper Cnnlon Mill-No.2 Pine Fiber Line and Bleach Plant Filtrate Floe
b y
5g
CRW x 3
CRW aovl T` S
DIM 1 11
B
IXekm Fla Ee 0.2
p Btah y
i 11 a 2 R t
alw
RRInc
Tmk
CTWI CBW] CBW] ktra OT B� no R2
RlvaLe Ftuav Inuwe FLrwv B W FW
Tank Tank Tmk Tm! Recker �tliw Tank Tmk
Raw. ^'
Tank
MRY
Ax Te Rnpoeeiwr
Black
1IWw
Figure 6.7 Fiberline Filtrate at the Blue Ridge Pine Line
National Council for Air and Stream Improvement

Technical Bulletin No. 919 41
i
6.2.3.6 Removal of Non Process Elements
Ion Exchange Methods
The minerals removal process(MRP)installed at the Blue Ridge mill is an ion exchange process and
is shown in Figure 6.8.
Removal of non-process elements is necessary if the acid bleach filtrates are extensively recovered,as
is the case in the Blue Ridge mill,in order to avoid scaling and other harmful impact due to build-up
of non-process element concentrations in the fiber line.
In this process the Da stage(D100)filtrate pumped to the MRP is first sent through a fiber filter.The
fiber is returned to the De stage,and the filtrate drops into a storage tank. It is further filtered in
several parallel sand filters in order to remove other suspended solids down to a size of one micron,
dropping to a second storage tank.
It is then pumped through parallel ion-exchange beds to a treated filtrate tank,from which it is
returned to the process.
The ion-exchange beds must be regenerated with NaCl. One bed can be regenerated while the others
continue to treat the filtrate.
Blue Ridge Paper Products, Canton
Schematic of Metals Removal Process
Bleach Filtrate (MRP)
from Di Stage
Brine
Fiber j (NaClj
Return ZFlitered
t
t
Fiber1
Strainert
t_. Regenorant
Softeners ______Wast e
Untreated related DI Filtrate
to Bleach Plant
Caron, Delaney, 1997
Figure 6.8 Minerals Removal Process by Ion Exchange(Blue Ridge 2006)
National Council for Air and Stream Improvement

42 Technical Bulletin No. 919
` "Chip Kidney"
The main source for metals non-process elements(NPEs) in the bleach plant acid effluent is the
wood.Normally,a large part of the NPEs contained in the wood will stay attached to the fibers until
they reach an acidic stage in the bleach plant. The other part of the NPE follows the black liquor to
eventually exit primarily with green liquor dregs(Wohlgemuth et al. 2001).It has been proposed to
use a"chip kidney"to purge metals. The metals would be extracted in an acid treatment stage(acid
hydrolysis)of the chips. This process removes metals effectively (Backlund and Radestrom 2005),
but it also creates a new effluent that contains the metals and some wood extractives.Before the"chip
kidney"can be regarded as an acceptable process,a suitable method for handling the acid treatment
effluent has to be developed.Precipitation methods have been studied for this.However,the"chip
kidney"process is in the development phase.
6.2.2.7 Chloride Removal Processes
Even a modest recycle of the Eop stage effluent to the brown stock washing has been found to
increase the white liquor sodium chloride concentration.An example is provided in Figure 6.9 from a
mill that tried the recycle for an extended period of time.At a level of 10%Eop filtrate recycle,the
sodium chloride concentration increased by about 4 g/I NaCI(2.5 g C1/1).
NaCI in White Liquor vs. Eop filtrate recycled
12 12
1510 •-----}----- - ' ---- 10 0
•
`o • • • c
------- - • _
8
•
t i 27
N O
tyJ
_ V 0
LOU
Z
0 0
200 400 600 800 1000 1200
Days of recycle
• Naa in WL Eop filtrate— s�soivo
ADwplm C-*-W
Figure 6.9 Impact of a Modest Recycle of Eop Filtrate on NaCl Content of
White Liquor
National Council for Air and Stream Improvement

Technical Bulletin No. 919 43
}
The tolerable level of chloride in the liquor loop depends on the mill and equipment and recovery
boiler operating conditions. Typical maximum allowable chloride levels are
• 2-3 g/I chloride in white liquor;
• 0.2-0.3 %chloride of black liquor solids; and
• 1.0-1.7%chloride in the recovery boiler ESP dust.
Recirculation of a significant amount of the Eop filtrate to brown stock cannot be tolerated without the
installation of a chloride removal system.
There are several patented processes for the removal of chloride from the kraft pulp mill. Table 6.2
shows a list of ESP ash treatment processes for chloride removal,the expected chloride and potassium
removal efficiencies,and the expected sulfate and carbonate recovery efficiency. The efficiencies are
defined as percent removed or recovered from the precipitator ash.
Chloride removal processes currently in operation in full scale include leaching processes(e.g.,in
Aracruz,Brazil)and crystallization processes (e.g.,in Blue Ridge and Soporcel's Figueira da Fez mill
in Portugal).
Table 6.2 ESP Ash Treatment Processes for Chloride and Potassium Removal
Process Chloride Potassium Sulfur Sodium
Process,Developer Removal Removal Recovery Recovery
Efficiency' Efficiency' Efficiency' Efficiency'
CRP(Sterling Chemicals), Crystalli- 85-90% 80-90% 85—90% —80%
ARC(Andritz), zation
PDR(Eka Chemicals)
PDP,Paprican Ion >92% —2% —98% —80—90%b
Exchange
ALE(Andritz) Leaching'- 80% 80%° —70% 70%
filter
LeacMng(Kvaemer/Metso) Leaching- 90% 82% 68% 63%
centrifuge
Bipolar Membrane Membrane 60% low 95%+
Electrodialysis(BME),
Paprican
Aqueous-Aqueous 60% 90%
Separation of Chloride w/
Polyethylene Glycol
'efficiencies defined as percent removed or recovered from treated ash
b depending of the ratio K/Na in the ESP dust
Conceptually,the leaching processes involve less equipment and process operations than e.g.,
crystallizing and ion exchange processes,but on the other hand experience higher losses of sulfur and
sodium.
The ion exchange process removes chloride selectively.Potassium and sodium are purged according
to their molar ratio in the ESP dust,which leads to very low removal of potassium. This may be
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44 Technical Bulletin No. 919
L' beneficial,but may also be an undesired feature in mills which experience build-up of potassium in
their liquor loop. The plugging and scaling of recovery boiler heating surfaces are,however,more
related to chloride than to potassium in the recovery boiler carryover and in the ESP fine dust.
Another difference between the ion exchange process and the crystallizer or leaching processes is that
the cleaned dust stays in solution(around 28%) in the ion exchange process and therefore has to be
evaporated to filing solids concentration when returned to the black liquor system. This consumes
steam for evaporation.
Again,the selection of the optimal chloride removal process becomes a mill-specific issue depending
on the equipment,recovery boiler conditions and sulfur/sodium/chloride/potassium balances,energy
prices, etc.
Crystallizing process
The concept for the crystallizing process used at Blue Ridge is shown in Figure 6.10.Dust from the
recovery boiler ESP is dissolved in water to a concentration of about 26%solids(corresponding to
85%saturation of sodium sulfate)and stored in a pre-evaporator feed tank.The solution is
crystallized in a vacuum evaporator/crystallizer, separated in a hydroclone,and dewatered on a
vacuum rotary drum filter. Condensate from the evaporator is returned to the ESP to dissolve the ash.
The concentration of the slurry leaving the crystallizer is maintained below the saturation point of
potassium sulfate and potassium chloride.It is pumped to a hydroclone to separate the sodium sulfate
crystals,which are dewatered on a rotary vacuum drum filter and dropped to an agitated black liquor
slurry tank.The black liquor slurry at high consistency is returned to heavy liquor storage. The
solution leaving the hydroclone(containing fine crystals)is returned to the crystallizer.A portion of
the filtrate from the vacuum drum is sewered to control the chloride and potassium levels in the
liquor.The rest is pumped back to the precipitator ash-dissolving tank.
The concept of the ARC process by Andritz and the PDR process by Eco-Tech utilize the same unit
operations,i.e.,dissolving and recrystalizing of the ESP dust followed by washing and dewatering of
the crystals on a filter.
Ion Exchange Process
The ion exchange process,PDP,developed by Paprican and marketed by Noram Engineering
(http://www.noram-eng.com/)and Eco-Tech is illustrated in Figure 6.11 (Noram 2006).
The dust is first dissolved in warm water in an agitated tank, forming a nearly saturated sodium
sulfate/sodium carbonate solution(28°/n)with chloride and potassium.There is an insoluble portion
that must be removed since suspended solids tend to clog the ion exchange resin bed.Pulse filtration
(Eco-PulseT Pressure Filter)is used to separate the suspended solids. The filter elements of the
pressure filter are periodically cleaned of insoluble solids using a short,low-pressure back-pulse.
During this sequence,the flow of liquor to the Pulse Filter is stopped and recycled back to the
dissolving tank(Brown et al. 1998).
National Council for Air and Stream Improvement

Technical Bulletin No. 919 45
Chloride Removal Process - CRP
Condense
• Diagram of the Process
for Removing Chloride Proc phator C ystallizer
and Potassium "sh
from the Kraft Heater
Recovery Boiler
Wash
Strong
Black Liquor
SaBcake Saltcake
Filter
fdix
To Recovery Tank
Boller
Chloride and
Potassium
Caron, 1995 to Clsposal
Figure 6.10 Crystallization CRP Process(Blue Ridge)
PDP - Precipitator,-'Dust"Purification
System :r
•_ (Titaco-rec
Water
ESP �� ;Nast
Dusk'. Waste d
�s ` �'to bla&llquor
,. Sludge a eva,,ratbrs
D�sahiinp� Fet s P�rwvOd
Tank" Ten., 1san •93
Figure 6.11 Ion Exchange Process (Norarn 2006)
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46 Technical Bulletin No. 919
The salt separation unit(SSU) utilizes short bed/water regeneration ion exchange technology. The
chloride is removed with an ion exchange process utilizing a short bed column. The fact that the ion
exchange occurs in a very narrow zone makes it possible to reduce the length of the column to just
longer than the zone. Using fine mesh resins allows this zone to be reduced further.A special
amphoteric ion exchange resin with both cationic and anionic exchange groups on each resin particle
is used.It allows both cations and anions to be removed simultaneously.The special resin also allows
sodium chloride to be eluted from the process with water, a key feature in the economic feasibility of
the process. The process involves an upstroke and downstroke in the column.In the upstroke,the
solution to be treated containing a mixture of sodium chloride and other chemicals is introduced into
the column. Sodium chloride is picked up by the resin.The cleaned solution is collected from the top
of the column. On the downstroke,water is passed countercurrently through the column. The resin is
regenerated by elution of the sodium chloride from the resin. Waste sodium chloride is collected from
the bottom of the column and the process is repeated.The waste solution, containing mainly sodium
chloride,is discharged.The cleaned solution of the ESP dust has a concentration of about 28%solids
and is recirculated to the evaporation plant. Stem is thus needed to concentrate the dust to firing solids
concentration(Brown et al. 1998).
This process can be applied to several other chloride-bearing streams such as the oxidized white
liquor and the spent scrubber liquor. It is reportedly possible to remove more than 90%of chloride
while retaining over 90%of valuable components.
Leaching Processes
Ash leaching is a simple process schematically shown in Figure 6.12.The ESP dust is diluted with
water to about 28% consistency.After that the solution,in which the chloride and potassium are
tenriched,is separated from the solids fraction by filtering(Andritz)or by centrifuge(Kvaerner).
The solids fraction at about 90%consistency is returned to the recovery boiler mix tank. The filtrate
or the centrifugate is sewered for purging the chlorides and potassium.
National Council for Air and Stream Improvement

Technical Bulletin No. 919 47
ESP dust Water
GoU o
Treated ESP
Cl Purge dust to mix tank,
@ 90%solids
Figure 6.12 ESP Dust by Leaching
6.2.3 Recycle of Chloride-Free Bleach Filtrates
Recovery of alkaline filtrates is more easily implemented where the preceding bleach stages do not
use chlorine dioxide.Mills that operate TCF or ECF-light sequences recycle some or all of the
alkaline filtrate to brown stock.Regardless of the sequence(ECF,TCF,ECF-light, etc.),the issues
with non-process elements present in the acid filtrates remain.
6.2.3.1 International Paper, Franklin, VA
The International Paper mill at Franklin,Virginia operates a high consistency ozone stage,the ZEtrac
process in an ECF-light sequence O (A)ZED on pine pulp. The mill recycles the filtrates from the Z
and the E stages according to the concept shown in Figure 6.13 (Griggs 1997).
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48 Technical Bulletin No. 919
WASH WATER
......... Z ........... E ........... D ......�
POST O± ACID
PRESS PRESS
TO B ROWIV-
STOCK _
WASHLN'G
2.1 m3/ADt 7.3 m3/ADt
Figure 6.13 Bleach Plant Filtrate Recycle at International Paper,Franklin,VA(Griggs 1997)
The last wash stage after the oxygen delignification stage is a wash press where Z-stage filtrate is
used as wash water.Following that press the pulp is pressed again in an"acid press."Some water(Z-
stage filtrate or water)is obviously added between the presses to allow a discharge of 2.1 m3/ADt of
acid filtrate from the acid press to sewer.Based on the water balance data indicated in Figure 6.13,
most of the"acid press"filtrate was obviously sewered together with non-process elements removed
t in the"acid press."Clean water is used as wash water on the E-stage and D-stage.All filtrate from the
D-stage(7.3 m3/ADt)is sewered, as well as the filtrate from the"acid press",2.1 m3/ADt.Thus, in
this scheme,the problems with chloride and other non-process element build-up have been
significantly reduced by sewering the D-stage and the"acid press"stage filtrates.
The literature documents the following performance data for the ZEtrac F-bleach line.
Table 6.3 Information about the IP(Franklin,VA)Mill Closed Cycle Bleach Plant
Griggs 1997 Bicknell et al. 1995
m3/t kg/t lb/T m3/t kg/t lb/T
Flow 9.4 11
AOX. 0.05 0.10 0.085 0.16
BOD 4.4 8.8 6.94 14.0
COD 11 22 11 22
Color 3.1 6.2 5.75 11.5
6.2.3.2 Mets6-Botnia,Rauma Mill, Finland
The Metsa-Botnia mill in Rauma,Finland operates the only Finnish 100%TCF mill with the bleach
sequence(ZQ)(PO)(ZQ)(PO)(PO).According to a recent announcement,the mill will start producing
ECF pulp also in 2007(Brantestrom 2006). Figure 6.14 shows the filtrate recovery concept is
conceptually similar as at IP,Franklin F-line: alkaline filtrate is recovered to brown stock washing
and acid filtrate is purged to the sewer.
National Council for Air and Stream Improvement

Technical Bulletin No. 919 49
J The Metsa-Rauma mill has a joint effluent treatment plant with UPM-Kymmene's mechanical pulp
and paper mill on the same site. The Metsa-Botnia mill reported its share of the total effluent
discharges after biological treatment as follows (Metsa-Botnia 2006):
Effluent flow 19.6 m3/t
BOD 0.16 kg/t 0.32 lb/T
COD 4.3 kg/t 8.61b/T
Color is not reported by the Metsa-Rauma mill.
Metsfi-Botnia-Rauma Bleach Filtrate Recycle
White water
Wash t- --- j Condensate
<Polpo
'� ��g."' it •,��'�,.;
7m3/t 1 1/2 Stage DD Fractional Washing
Metsa Ravme,&each Recycle,September 1999
Figure 6.14 Bleach Filtrate Recovery at Metsa-Rauma Mill(Gleadow et al. 2003)
6.2.3.3 Swedish TCF Mills
Two of the Sodra mills in Sweden(Vero and Mansteras)have converted to 100%TCF operation.The
Monsteras mill studied closed cycle technology extensively in the late 1990s,but concluded that it
was not successful.The mill decided to install biological effluent treatment to meet the COD limit
(Sodra Cell 2002).
The recovery of the acid filtrate was studied at the Varo mill using e.g.,the Netfloc process (Kemira)
as a non-process element removal"kidney."These studies were not continued after the Swedish EPA
ordered the mill to build a biological effluent treatment plant. The mill had originally planned to
implement closed cycle operation.
All three Sodra mills currently operate very efficient biological treatment plants. Unfortunately,
effluent color is not reported by any of these mills, as color monitoring is not required in the Nordic
countries.
The SCA mill in Ostrand, Sweden has a ZEtrac bleach plant.The bleaching sequence was reported to
be O Q OP ZQ OP (SCA 1996).Kappa for softwood pulp from the digester was 23 and from the Oz-
stage 12.The brightness of the pulp is reported to be 90%ISO and viscosity 560-570 dm3/kg.The
1 bleach plant effluent was reported to be 7 m'/ADt. The COD discharge from the bleach plant has been
reported to be 20-25 kg/ADt. Data for effluent color is not available.Precipitation of metals in the
National Council for Air and Stream Improvement '

50 Technical Bulletin No. 919
r
first acid bleaching stage has been reported as a problem when closing up the plant(370). When the
water system is closed to a certain degree, calcium oxalate and gypsum start to precipitate in the
piping system. When this happens the mill has to open the water system. To improve the metal
management,the mill was going to install a green liquor filter and a new dregs filter.Recent
information suggests"a totally closed bleach plant would be a very difficult target to reach."The mill
has therefore installed efficient biological treatment(Rodden 2005b).
6.2.4 Laboratory Simulation ofAlkaline and Acid Filtrate Recovery
A laboratory simulation was carried out for the recycling of both acid and alkaline stage effluents for
the Aho,(EoP)D(PO)bleach sequence according to the concept shown in Figure 6.15 (Colodette et al.
2002). In this concept both unbleached and bleached pulp were assumed to be pressed to high
consistency to allow a tight water balance.The simulation was carried out on oxygen delignified
eucalyptus pulp with a kappa number of 8.3 and a carryover to bleach plant of 10.2 kg CODA.
O•Press A�,,,•Vacuum Filter ^(EOP)-Vacuum Filter D•Vaeuum Filter (PO)-Preis
CF=1.67 eF-1.67 OF- 1.67 DF- 1.67 CFa 1.67
j 4A (EDP) 9.0 (d CC4SC-0P) 9.0 (i CC rSY/NI) BA (PO) Co 10.7
I Cat- 30 Cat- 12 Cat- 12 Cat- 12 Cat= 30
I 2.33 7.33 7.33 7.33 Z33
Cat is a' Cat 1.5 .:x8 Cat 1.5
�,...;' I .
6SJ �t 66.7 'ir� 657 � 240
?+ 6.67 1.67 1.67 1.67
Cat- 10 Cat- 10 Cat• 10 Cat= 10 Cat- 10
l i ' 617
56.7 67.3 56.7 67.3 569 672 15.0 25.7
i
Rorauatiewn9 4.0 to(EOPI 9.0 to 0
3.89 10.7 f0.7 70.7 10.7
i
0.11 9.0
Filtrate,mVl
unites Sewer 131uent 9.11
Consistsnry(Cat)-; Id,caustkiain9611uent 389
Volume-mra Pr6-%Waahin9 4.00
011utlan Factor(OF)-m'R White Water MM 9.00
Clean Candensete(CC) B.BO
i
Figure I-Amt(EOP)D(PO)Bleaching Filtrate Strategy.
Figure 6.15 Laboratory Simulation of Alkaline and Acid Filtrate Recovery(Colodette et al.2002)
)
National Council for Air and Stream Improvement

Technical Bulletin No. 919 51
`✓ In the study,part of the Au.,stage effluent was returned to the recausticizing cycle to be used for lime
mud and dregs washing.The minerals in the acid filtrate would be discharged mainly with green
liquor dregs. The Eop stage effluent was recycled to the post OZ delignification wash press and the
An,,drum washer. Most of the D-stage filtrate was sewered.
The use of the acid filtrate from the acid hydrolysis stage on the post-oxygen washer was not
considered viable for the following reasons:
• increased oxidized white liquor consumption in the oxygen delignification;
• risk for lignin precipitation;
• increased calcium oxalate formation in the oxygen delignification;
• accumulation of heavy metals possible leading to a selectivity loss in the oxygen
delignification; and
• contamination of the pulp with by-products from the hydrolysis.
With the acid hydrolysis filtrate used as a water source in the white liquor making,the color in the
total bleach plant effluent would be 2 lb/T.With the acid filtrate going to sewer,the total bleach plant
effluent color was about 12 lb/T.The chloride-containing effluent would not be recycled,so a
chloride removal process would not be necessary.
The application of the acid hydrolysis filtrate as make-up water in the recausticizing was not
simulated.This concept represents new technology and poses several challenges.
• The water balance of the recausticizing area has to be able to receive the make-up water,i.e.,
f the lime kiln should have an electrostatic precipitator rather than a scrubber,which would
supply most of the water make-up to the weak wash.
• The filtrate has to be filtered to remove fibers.
• The non-process elements(NPEs)introduced with the acid filtrate will increase the NPE
content of the lime mud and green liquor. NPEs will likely accumulate in the lime mud,thus
impacting the kiln and recausticizing operations (Colodette et al.2002)
• Potential odor and TRS emission issues may arise from using an acid filtrate for water make-
up in the recausticizing area.
• Increased formation of dead load compounds may result from the sulfur present in the acid
filtrate.
In conclusion,the proposed laboratory concept represents an interesting opportunity to further reduce
color but generates several unanswered questions.
6.2.5 ECF Bleach Plant Closure by Eka Chemicals(Ultrafthration)
Eka Chemicals has studied'a concept for partial bleach plant closure(PC'Tm),which is illustrated in
Figure 6.16.Results from operating the process in pilot scale in a Scandinavian mill were reported
(Bryant,Sundstr6m,andJour 1998).
It was concluded that the OF and partial closure of the alkaline filtrates can reduce the COD by as
much as 60%and the AOX by as much as 40%. Since the permeate,now containing mainly low
molecular weight material, is taken to biological treatment,the efficiency of the biological treatment
increases.
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52 Technical Bulletin No. 919
The Eka Chemicals' concept was tested extensively in pilot plant scale at Stora Norrsundet mill,
where combined Eop and EP filtrates from sequence D(Eop)D(EP)D were treated.The cut-off was
4000 Dalton and the flux rate was about>180,1/m3 h.
UNBLEACHED BLEACHED
CHIPS DIGESTER PULP BLEACH PULP
BROWN STOCK AREA PLANT
WHITE BLACK ALKALINE
LIQUOR LIQUOR ALKALINE
RECOVERY ` -MEMBRANEl1NIF +
RECAUSTAREA tMEMBAFRTRATt0 1 ACID
EFFLUENT
OF PERMEA
TREATED
ESP DUST
EFFLUENT
G}yaK TREATMENT
SYSTEM
CHLORIIDE TREATED
SOLUTION EFFLUENT
L
Figure 6.16 EKA Nobel Partial Bleach Plant Closure(PC)
The bleach plant was not operated as a closed cycle but only a small fraction of the effluent was
filtered in the membrane unit.The permeate combined with the acid filtrate was treated further in a
pilot biological treatment unit.
The ultrafrltration of the alkaline effluents reduced the bleach plant loads and improved the treatment
efficiency of the biological treatment as shown in Table 6.4.
Table 6.4 Pilot Plant Results of Eka Chemicals Ultrafrltration Concept(Bryant,Sundstrom, and Jour
1998)
Bleach Plant Discharge Removal in Biological Treatment
1 2 1 2
kg/ADt(lb/ADT) kg/ADt(lb/ADT) % %
AOX 0.52(1.04) 0.41 (0.82) 69.9 76.9
COD 27.3 (54.6) 15.3 (30.6) 60.1 77.6
TOC 11.1 (22.2) 6.7(13.4) 64.3 78.6
Color 14.4(28.4) 5.5(11.0)
BOD7 8.4(16.8) 5.2(10.4) >96 >96
NOTES: - 1 =Untreated acid filtrate+untreated alkaline filtrate
2=Untreated acid filtrate+OF treated alkaline filtrate
f
�J
National Council for Air and Stream Improvement

Technical Bulletin No. 919 53
It was concluded that the OF improved the biological treatability considerably.
A simulation of the application of Eka Chemicals PC`process was carried out for the Leaf River Pulp
Mill(Herstad et al. 1998, 1999).The simulation included both a OF process for the alkaline filtrate
and a chloride/potassium removal process for the recovery boiler ash.Different points of adding the
OF concentrate to the fiber line were tested. Table 6.5 summarizes the main data for the bleach plant
effluent at different points of adding the OF concentrate in the fiber line,compared to the base case
(no ultrafiltration,or recycle).
Table 6.5 Simulated(GEMS)Impact of PC'on Bleach Plant(Herstad et al. 1999)
Unit COD Color AOX
Base process,no UF,no closure kg/ADt(lb/ADT) 53.4(106.8) 46(92) 0.59(1.18)
OF concentrate to post 02-stage kg/ADt(1b/ADT) 40(80) N/A 0.55(1.1)
decker bottom showers
OF concentrate to pre Oz-stage kg/ADt(lb/ADT) 35(70) 20(40) 0.48(0.96)
brownstock washer
OF concentrate to weak black kg/ADt(lb/ADT) 34(68) 20(40) 0.46(0.92)
liquor(A)
Based on the simulation, about I kg of chloride/tp(2 lb/ADT)would be returned to the liquor cycle
with the OF concentrate.The application of the Eka Chemicals chloride removal process would
-/ eliminate any chloride buildup in'the cycle,and actually result in less chloride in the cycle than the
base case mill.Based on these simulations,it was concluded that the Eka Chemicals PC`process,if
applied at Leaf River mill
• would reduce bleach plant effluent AOX and COD after effluent treatment by 33%and 53%
respectively(20%and 37%before treatment). Color would be reduced by 60%.
• would not change evaporation loading.Total solids to the RB would be about the same
because less ESP dust is recirculated to heavy black liquor.
• would decrease the chloride and potassium in the ESP dust 54% and 89%respectively with
partial closure and chloride removal.
• would increase the bleach plant chlorine dioxide use by around 1 kg/t while the sodium
make-up requirement would decrease by about 2.9 kg NaOH/t(48).
The application of the membrane process at the two mills participating in the above studies has not
gone forward.The membrane technology is still developing. No applications for ECF or TCF bleach
plant filtrates are known to be in operation.The only full-scale operating membrane treatment for a
fiber line filtrate is at the Stora-Enso Nym6lla mill in Sweden where the oxygen delignification stage
filtrate is treated.The Nymolla mill is a Mg based sulfite mill.The oxygen delignification stage uses
sodium hydroxide as the base.Therefore,joint recovery of the cooking and oxygen delignification
spent liquors is not possible. The installation at the NymSlla mill and the experiences with membrane
filtration is discussed in more detail in Section 7.
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54 Technical Bulletin No. 919
i
7.0 COLOR REMOVAL—SEPARATION PROCESSES
7.1 Membrane Technologies
The following sections describe various membrane technologies which could be used for treating
colored wastewaters.Depending on the pore size,the membrane processes are divided into
microfiltration(MF),ultrafiltration(UF),nanofitration(NF), and reverse osmosis (RO). The pore size
or cut-off value of the membranes in these processes decreases in named order.A membrane with a
higher cut-off value has a higher filtration capacity but generally lower removal efficiency. Figure 7.1
gives a comparison of membrane sizes.
Separation
Process ,
'Ay®��grni i Mllk ,ro e
�•�.. .Red 9kod Cet1s`.
CiC�:tl�r� a 6eletln , IM611cellec
S�t-f'CQ '61eta1Wn eacterta
FJ1mumn r ropen ActlYatilt `
' : �QltYl1T0T[ oa:en_mswn";, : Csihori „__'„
ilrl'i�GCfYi�S 8 ° wrus„^ s Biue. CryptaspaMAhim
lndigo:0yo'
"Le$oss�t ,J%atlMstd- GWrdta ;Homan Halr�
I��l • t;ssmwk cyst^
0 M 7W._. 94tl
Appraxldotecuinr 100 20if ON 20 000 JN.'j% 11 600;0ao 1 ktM s MFl
tHklpht as
Note:'1.minron"lmtcrairioteh<4x104 inchcs+ix�04�AnjsSiom units. � "'��200�-Kali Mam6rai�mffiysr¢rin
Figure 7.1 Membrane Size Classifications(from Koch Membrane Systems)
Because of the high membrane cost and their limited flux capacity, the economical feasibility of the
process is directly proportional to the volumetric flow.Therefore, of the kraft mill effluents,the Eop
filtrate with a low volume and high concentration is typically considered most feasible for treatment
with membrane separation. Treatment of total mill effluent would be extremely costly.
7.1.1 Microfiltration (MF)
Microfiltration has the largest pore size of any of the membrane technologies discussed above,
approximately 0.03 to 10 microns and a molecular weight cut-off of greater than 100,000 daltons. The
typical operating pressures for MF systems are 10 to 100 psi.Microfiltration membranes usually
come in two flow types: cross-flow and dead-end flow. With cross-flow membranes,the fluid runs
parallel to the membrane and passes through the membrane based on the pressure differential.In
dead-end flow,the fluid flows perpendicular to the membrane.Because of its large pore size,MF is
often used as a pre-treatment step for reverse osmosis and nanofiltration. To prevent fouling,frequent
National Council for Air and Stream Improvement

Technical Bulletin No. 919 55
backwashing aids in keeping the membrane clean and helps maintain membrane flux.Microfiltration
can also be used with biological treatment in membrane bioreactors.Most mill-scale implementations
ofmicrofiltration are for the recovery and'reuse of internal water streams(coating kitchen effluent) or
as pre-treatment stages for other membrane processes.
7.1.2 Ultrafiltration(UF)
Membrane filtration is a separation method that separates dissolved molecules based on their size and
charge.High molecular weight substances such as lignin compounds,which are the primary sources
of color and COD in effluents, can be concentrated in a smaller stream for separate treatment or
destruction.The permeate,which contains low molecular weight components(mainly water),is
sewered or may be reused in the mill to some extent.
OF is a pressure-driven process where colloids,particulates, and high molecular mass soluble
compounds are retained by size exclusion. OF has a pore size of approximately 0.005 to 0.1 microns
and a molecular weight cut off of 10,000 to 100,000 daltons.The typical operating pressures for OF
systems are 5 to 150 psi. The OF membranes are generally manufactured in either flat-sheet or tubular
form.The main system components include the membrane units,pumps,and cleaning system.
Ultrafiltration is considered proven technology but it has not gained acceptance in the pulp industry.
The OF or RO treatment processes would require extensive pre-treatment processes for solids
removal,which would most likely include coagulation and filtration. This would increase the
equipment cost and land required for these treatment processes.There are no known installations of
kraft mills using OF to treat the whole trill effluent or bleach plant, although OF is used in paper
mills to treat the white water in the paper mill circulation system and coating kitchen effluent.
Several risks related to membrane applications are discussed below.The modularity of the membrane
installation makes it more reliable than a single unit.Membrane fouling and abrasion gradually
diminish the flux,necessitating membrane replacement after some time.Typically,membrane
lifetime has been around 18 months. Short membrane lifetimes or unpredictable fouling tendencies
make a membrane unreliable.
Recirculation of membrane concentrate into the liquor loop or reuse of the permeate may have a
considerable impact on liquor quality and production processes. Some impacts might be increased ash
and calcium content of pulp and increased chloride concentration in the black liquor.The increased
chloride content in the liquor could lead to recovery boiler fouling.Return of the concentrate to the
weak black liquor would increase the load on evaporation and the recovery boiler,possibly reducing
production.
Impact of pH
It is well known that membrane filtration of acidic bleach plant filtrates results in severe fouling
problems, destroying the capacity of the membrane(Sierka,Cooper,and Pagoria 1996; STFI 2002).
This is explained by the fact that organic acids(e.g.,fatty acids)are protonized in acidic filtrates and
strongly adsorbed onto the membrane. Therefore,ultrafrltration of the acidic bleach plant effluents
would not be practical.
Because of the high membrane cost and their limited flux capacity,the economical feasibility of the
process is directly proportional to the volumetric flow.Therefore,of the kraft mill effluents,the Eop
filtrate,which is alkaline and has a low volume and high concentration,has typically been considered
most feasible to treat with membrane separation.Depending on the bleaching conditions and the
kappa number,the first E stage(El)effluent can have a higher content of higher molecular weight
and colored organic compounds than the other bleach stages. Since the volume of this stream is much
National Council for Air and Stream Improvement

56 Technical Bulletin No. 919
less than the total bleach plant effluent,it would be much more economical to treat while still
removing a large portion of the bleach plant COD,AOX,and color.
Flux
The surface load or flux(liters/m2h) defines the dimensions of the plant.Typically,an expected flux
for OF would be 150-300 I/m'h,and for NF 50-701/m2h. Studies of EoP filtrates in an OD EoP DED
sequence confirmed that the flux on OF membranes increases with decreased incoming COD(STFI
2002).Another study found that the parameter with the largest impact on flux is conductivity,i.e.,the
concentration of the low molecular weight inorganic substances.The retention of organic substances
varied depending on the type of filtrate and the water management system of the mill.
A study where EoP filtrate was filtered through a OF membrane with 4000 D cut off found that the
flux varied between 160-2001/m2h, depending on the applied water pressure,at volume reduction
factors at least up to 12(Bryant,Sundstr6m,and Jour 1998).
The Finnish Lappeenranta Technical University has studied the DOW 270 membrane,a rather
hydrophilic NF membrane with fairly high retention and permeability,in high shear filters called CR
filters. (ManMiri,Nystrom,and Pekuri 2004).Metso PaperChem(OptiFilter CR)supplies the CR
filter process(http://www.metsopaper.comi). On paper machine white water the flux rates of 80-100
1/m2h could be obtained at a recovery below 70%.No corresponding studies on EoP filtrate using this
specific membrane could be found in the literature.
Fouling
The membrane technology is developing with respect to resistance to fouling.A study used
membranes made of polyether sulfone in a trial to treat the EoP filtrate from a D(Eop)DED sequence.
—1 They found that membranes that were modified in order to minimize their hydrophobicity reacted
more positively to washing than unmodified membranes.They also concluded that a considerable
amount of the fouling caused by a cake or gel layer could be reduced if the shearing forces at the
membrane surfaces increased(STFI 2002).
Various physical or chemical methods can be employed to clean the membranes.
The Stora-Enso mill at Nymolla in Sweden has a OF plant with membranes from PCI in operation,to
treat the alkaline effluent from an oxygen delignification stage.Figure 7.2 shows the OF
configuration at the Nymolla mill.A study was performed to evaluate the cleaning and operation of
the ultrafiltration plant(Greaves 1999). Laboratory tests were carried out in order to find out what the
fouling layer consists of and to find the most appropriate cleaning procedure.Production data were
analyzed to establish if the membranes were cleaned unnecessarily often.It was found that the fouling
was mainly of organic origin and was seen as brown precipitation on the surface of the membranes.
Analysis of the membrane surface with energy dispersive X-rays(EDX)showed that there was also
some inorganic fouling,mostly silicon,iron,and magnesium. Cleaning tests were carried out on a
small laboratory test unit from PCI using fouled membranes from the mill.Both acid and alkaline
chemicals were used to clean the membranes. The current cleaning procedure was not optimal and
some improvements were suggested.Production data showed that the membranes were often cleaned
when there was no decline in flux.This leads to high wear on the membranes and shortens their
operational lifetime.Less frequent cleaning,especially during the first stages, of the OF plant was
therefore recommended.It was found that many of the membrane tubes were clogged with a clay-like
precipitation consisting of fibers, organic material and precipitated magnesium hydroxide. This clay
completely stopped the flow through the tube,thereby reducing the active membrane area of the OF
plant.The 2003 EMAS report issued by the Nymolla mill notes that the COD discharge of the mill
.J
National Council for Air and Stream Improvement

Technical Bulletin No. 919 57
increased because of bad performance of the OF plant due to plugged membranes. The problems have
reportedly been corrected.
WA5Nt7ATER
O Q P
o
UNRLP.ICHEDPULP
12%D$ BLEACH
Pule
uP
UQUORS70
.CONCENTRATE AcnYE8LUDCE
2URARKEDIIER
Figure 7.2 Ultrafiltration of Oxygen Delignification Effluents at the Nym6lla Sulfite Mill in Sweden
(Wickstr6m 1997)
One novel technique that has been studied in the literature is to use dissolved gas flotation to remove
the suspended solids and colloidal material prior to OF treatment(Pokhrel and Viraraghavan 2004).
In laboratory experiments,El effluent was treated with both dissolved air flotation(DAY)and
dissolved CO2 flotation followed by UF. The dissolved CO2 flotation proved slightly better than
DAY,but both were effective in removing a large portion of the TSS in the EI effluent. The dissolved
CO2 flotation reduced membrane fouling more than DAF.
Treatment Efficiencies
Studies have been carried out on Eop stage kraft bleach plant filtrates from oxygen delignified pulp
(Filth,Pfromm, and Sokol 2000;Bryant, Sundstr6m,and Jour 1998;EKONO 2006).
Table 7.1 summarizes the reduction efficiencies that have been measured when filtering the Eop
filtrate from softwood bleach plants, sequence DE(OP)DED.
�J
National Council for Air and Stream Improvement

58 Technical Bulletin No. 919
Table 7.1 Results of OF and NF of Eop Filtrates
OF OF OF+NF OF OF+NF OF
in series in series
Effluent type Eop Eop Eop Eop Eop Eop
filtrate filtrate filtrate filtrate filtrate filtrate
Bleach Sequence D(EoP)DED DEDED DEDED DEDED DEDED DeopDED
Filter/Membrane 1) 2) 2) 3) 3) 4)
Flux I/mZh 200-400 50-80 200-400 50-80 160-200
Removal
Lignin 70%
COD 71% 55% 91% 26% 85% 50%
BOD 16% 28%
Conductivity 2% 38% 2% 15%
Color —75%
TOC 49% 90%
AOX 51% 96% 50%
DS 0% 0%
P 27% 93% 27% 91%
N 41% 68% 41% 65%
Monovalent Ions very low
Divalent Ions 70-80%
(Ca,Me.Mn.Ba)
Na 8% 44% -2% 18%
CI 1% 3% 0% 1%
K 14% 43% 0% 17%
Mn 67% 100% 100% 100%
Fe 100% 100% 100% 100%
SO4 3% 98% -13% 90%
NOTES: 1) polysulfone membranes
2) CR filters,using ultrafiltmtion membranes C30,PS100,PES25S(cutoff 4000 D),and nanofiltration
membrane DESAL 5(cutoff 200-500 D). Tests with a low volume reduction factor,VRF=24(VRF=
feed flow/concentrate flow);
3) same as 2)but high volume reduction factor,VRF?7;and
4) PCI—filter with ES404 polyethersulfone membrane(cutoff 4000 D),VRF=6.
Based on Table 7.1, it can be concluded that OF reduced lignin and thereby the color of the filtrate by
70-75%. COD and AOX were reduced by 50-55%.BOD,however,was only reduced 20-30%. OF
removes the high molecular weight colored compounds that are hard to biodegrade,leaving the
smaller, easily biodegradable compounds. Soluble chloride was not removed at all by UF, and sodium
very little,0-8%. Divalent ions,e.g.,Fe and Mn,were also removed quantitatively.
When the OF permeate was treated with NF(or the Eop filtrate as such with NF),more organic
material was removed.COD,TOC,and AOX(and color)were removed to>90%. Soluble chloride,
being a very small ion,was still going through the membrane almost quantitatively,while the NF
membrane removed 20-40%of the sodium.Note that AOX(organic halogen)was retained in the
concentrate.
Thus, if OF or OF+NF or NF were used, the soluble chloride concentration in the feed,permeate,
and concentrate would be about the same. The amount of chloride recovered would be determined by
National Council for Air and Stream Improvement

Technical Bulletin No. 919 59
�— the amount of concentrate, i.e.,the volume reduction factor and the chloride attached to the high
molecular mass as AOX.
One literature source concludes that the optimum VRF may be between 5-7 or 80-85%permeate of
the feed(Bryant, Sundstrom,and Jour. 1998). If a larger fraction is removed as permeate,the cost of
removal increases due to lower flux.On the other hand,more chloride is recovered with the
concentrate at lower permeate fractions.This impacts the recovery cycle.
The most viable application of a membrane process is to treat the Fop filtrate by using a OF type of
membrane. However,the membrane pore size must be established in lab and pilot tests. Figure 7.3
shows a possible configuration for OF treating bleach plant effluent.
i
OF
Unit
TO OF OF TO
Brownstock Concentrate (Penteate Waste
Fiberltne Treatment
Figure 7.3 Ultrafiltration of Alkaline Filtrates from an ECF Bleach Plant(Herstad et al. 1998)
The permeate,which contains most of the original inorganic dissolved compounds(e.g.,chlorides) as
well as about half of the organics,would be directed to the treatment plant.
Separate incineration and evaporation of the concentrates would be possible,but it is more likely that
the OF concentrate would be returned to the liquor loop for evaporation and incineration.To prevent
unacceptable build-up of chlorides in the white liquor, it would most likely be necessary to purge
chloride in a chloride removal process.
Treatment of bleach plant Eop filtrate by full-scale ultrafiltration processes has been applied in at least
two Japanese mills and one Swedish kraft mill for a number of years.To our knowledge,all three of
these ultrafiltration installations were discontinued after several years of operation.
Although ultrafiltration is considered proven technology it has not gained acceptance in the pulp
industry.
Table 7.2 summarizes the information known about full-scale installations in chemical pulp mills
(kraft and sulphite).The only OF plant that is known to be operating on effluent in a pulp mill is the
Stora-Enso sulfite mill in NymSlla,Sweden,where oxygen delignification effluent is treated.
A sulphite mill in Norway operates a OF plant on fermented spent sulphite liquor prior to vanillin
production.
National Council for Air and Stream Improvement

Table 7.2 Information about Full-Scale OF Plants rn
0
Supplier,
Mill Treated stream surface area, Feed Cut-off Flux Reduction
oper,period, m3/d gpm Daltons Vm2/h VRF Achieved
status
Borregaard Industries Calcium sulphite PCI Remove low mol.
Sarpsborg sulphite mill liquor,after fermentation 1200 220 20,000 material prior to
Norway 1984...... the vanillin
_
MoDo,Domsjo Pre-bleach caustic PCI production unit
-
m Na-based sulphite mill deresination stage effluent 728 m2 2880 530 100,000 150 23.5 COD 70%
Sweden 1985- 1988 pitch 80-85%
m shut down
n MoDo,Husum About 40%of E� filtrate in Flootek COD 50%
bleached kraft mill O(CD)(EO)D bleaching 200 m2 1200 220 25,000 200-250 15 AOX 50%
g Sweden 1989- 1993 BOD7 35%
o shutdown Na 20%
Y Cl 7%
Stora+Enso,Nymolla Oxygen delignif.filtrate PCI COD 46-55%
o bleached sulphite mill prior to bleaching 4650 m2 7200 1320 4,000 70 SW 50 Na 5%
rn Sweden (2 lines: SW,HW) 1995..... 87 HW TOC 50%
m in operation
m
3 Sanyo-Kokusaku Pulp Co. One-third of El stage Ultrasep
bleached kraft mill effluent 672 m2 900 165 47-66 8.3 COD 82%
Iwakuni,Japan °
/0.
m shut down
CD
3 Taio Pulp Company El stage effluent Nitto-Denko
bleached kraft mill 1480 m2 1740 320 8,000 98 16.5 COD 79%
Japan 1990—unknown
shut down m
v_
W
c
m
Z
0
co
co

Technical Bulletin No. 919 61
7.1.3 Nanoffltration (NF)
NF has a pore size of approximately 0.001 microns and a molecular weight cut-off of 1,000 to 10,000
daltons.No full-scale NF plants are known to operate in kraft mills.
Nanofiltration has a lower permeate flux than ultraf)ltration,which results in cleaner product,but NF
is more sensitive to fouling and must be preceded by a pre-treatment step.The pre-treatment step is
often ultrafiltration or a biological process.
Generally,NF has been conducted with conventional spiral wound membranes,but recently high-
shear cross-rotational(CR)membranes have been developed. CR membranes are more resistant to
fouling and may not require the rigorous pre-treatment step needed by spiral wound membranes.In
CR filters,the high-shear or turbulence is generated on the surface of the membrane by a rotating
blade. Laboratory tests for a high-shear CR membrane(named NF270)were conducted using the
effluent from an activated sludge plant in a mechanical pulp and paper mill(Manttari,Nystrom,and
Pekuri 2004).At volume reduction factors of 2 and 13,the NF270 membrane retained about 85%of
the TDC,60%of the conductivity, and most of the color(see Figure 7.4).Performance was enhanced
by neutral pH conditions and temperatures below 45°C.NF appears better at removing color than
UF,because salts pass through the OF membranes.
Like the other membrane technologies,NF could be used to treat the whole mill effluent.However,to
treat the whole mill effluent,a pre-treatment step would be required to remove suspended solids to
prevent membrane fouling.Also,using NF would create a highly concentrated stream that would
need to be disposed of.There are no known installations of kraft mills using NF to treat the whole
mill effluent.
�-� conductivity -
l0 10000 colour
•i
10 so
• •g
IOW
E 6 •
• g 100
q ° A p 0 C p
• A A4 0 0
° 2 '• C � 10 �
U 8 po 0 0 0 O
0 1
0 s 10 I5 0 s 10 Is
300 TIC • 1200 TOC •
250 1000
200 900
E Is0 • A E •
• e •
F 100 • 400
c
s0 0 0 200
.0
•
001.
3 10 15 0
0 5' 10 is
Fig.6.Conductivity(a),colour(b),total dissolved inorganic carbon(c)and total dissolved organic carbon(d).concentration in the concentrate and the
pemcote streams as a function of values:reduction factor(VRF)in nonofiltration of discharge water of an actisated sludge plant((•)concentrate,(0)
TFC ULP membrane and(a)NF270 membrane).
Figure 7.4 Color Removal Using NF270 Membrane(Mantrari,Nystrom,and Pekuri 2004)
National Council for Air and Stream Improvement

62 Technical Bulletin No. 919
7.1.4 Reverse Osmosis(RO)
Reverse osmosis is similar to ultrafiltration in that the effluent is treated by passing it through a
membrane that rejects molecules that are larger than the pore size. The difference is that in reverse
osmosis the pore size is much smaller,with the result that high-pressures (10-100 Bar)must be used
to force the effluent through the membrane.
Reverse osmosis is used;for example,in desalinization of seawater and has the potential to remove
almost all impurities and produce clean water for reuse.
To treat the whole mill effluent,a pre-treatment step would be required to remove suspended solids to
prevent membrane fouling. There are no known installations of kraft mills using RO to treat the
whole mill effluent or colored bleach plant effluents.RO has been used in sulfite mills for water reuse
and spent liquor treatment.
In 1998,the Irving pulp and paper mill in Saint John,New Brunswick, started up an RO system for
the treatment of condensates from the 5th evaporation effect(Dube et al. 1999). The mill is a
bleached kraft mill that produces about 900 tons/day of market pulp. The mill did not have secondary
treatment and instead used in-process measures to meet its environmental requirements.The RO
treatment of the condensate from the 5th evaporator effect was implemented to reduce the effluent
toxicity,which was not removed by condensate stripping. The RO treatment removed about 89%of
the COD from the stream and about 88% of the BOD.No data were given for color removal. The
clean permeate is returned and used as wash water on the No.2 post oxygen delignification washer
and the concentrate(about 1%of the flow) is either burnt in the bark boiler or sent to the high solids
crystallizer and eventually burnt in the recovery boiler.
7.1.5 Membrane Bioreactors
The membrane bioreactor(MBR)is a hybrid biological treatment system that combines the biological
activity of a free-floating reactor,such as an AST,with the advantage of membrane separation to
achieve reductions in suspended solids, COD,BOD,and toxicity.In this process,membranes are
placed in an aerated biological reactor.Effluent is fed to the reactor,where it is biologically degraded.
The effluent passes through the membrane and this permeate is discharged.The accumulated sludge
is then withdrawn for disposal.The advantages of a membrane bioreactor include higher loading,
smaller size, insensitivity to sludge settling characteristics, and effective removal of solids,COD,and
toxicity.In addition,the sludge retention time(SRT)and the hydraulic retention time(HRT)can be
varied independently. Disadvantages include membrane life span,restricted flux rates,and initial
investment cost.
In one pilot study,an MBR treating CTMP interstage refining effluent and operating with a hydraulic
retention time of 36 hours and a sludge retention time of 15 days achieved removals of 68%, 87%,
and 98%for COD,BOD,and suspended solids,respectively(Dufresne et al 1998). Color removal
was not reported. Figure 7.5 shows the configuration used for this study.
National Council for Air and Stream Improvement

Technical Bulletin No. 919 63
�1
I
2 a
I
I
A.
2
i
4 �
1
o�el i
2.Schematic dfogmm o(the Hollow Aber internal mem6wnce bioteoctor.I.pnvun
gauge,2.wamm pump63.Qoat fo,level eantm44.membmve 6,aemtcn,6.dudge
Wde,T.bad69thing.8 wa#ewater entry,9 ate entry,10.effluent sevnrge
Figure 7.5 Membrane Bioreactor(Dufresne et al. 1998)
Laboratory studies of the treatment of secondary condensates in a bioreactor,consisting of a reactor
and a ceramic tabular OF membrane,were carried out at the Western Pulp Ltd.Kraft mill in
Squamish,British Columbia. The reactor was operated at 60oC and fed with evaporator condensate.
The removal efficiencies were 99%for methanol, 91%for TOC, and 99%for reduced sulfur. Color
was not reported(Brrube 2000a,2000b,2001).
A membrane bioreactor combines both biological treatment and membrane separation. The system
consists of a reactor tank,ultrafiltration membrane, and aeration system. The reactor tank can be filled
with packing media,which serve as a carrier for biological growth. In this process,the untreated
effluent is fed to an aerated reactor tank with the appropriate hydraulic retention time(HRT).A side
stream is then withdrawn and passed through an ultrafiltration membrane.The permeate from the
membrane is discharged as treated effluent and the concentrate from the membrane is returned to the
reactor.A portion or all of the permeate from the membrane can be recycled to the reactor if needed.
This process is used in a variety of industrial applications,but there is no full-scale implementation
treating kraft mill effluent.This process has been proposed as a form of condensate polishing to treat
evaporator condensates,but it could be used to treat other streams.
National Council for Air and Stream Improvement

64 Technical Bulletin No. 919
' 7.2 Ion Exchange
Ion exchange resins, such as weals basic resins based on a phenol formaldehyde matrix,have been
found suitable for'treatment of pulp and paper mill effluent.
The ion exchange treatment processes include the following steps.
• pH adjustment and pre-treatment(pH requirement varies with the resin;usually it is on the
acid side towards pH 2-4,but may be up to pH 9)
• Effluent treatment step passing the effluent through the column until breakthrough capacity is
reached.When the resin is saturated the column needs to be eluted
• Elution stage,where the pollutants are removed usually with caustic in a concentrated form
• Activation stage where sulfuric acid is passed through the resin to reactivate it.
In the kraft industry,the ion exchange process research has concentrated on treatment of bleach plant
effluent for removal of color and chlorinated organic compounds. One example is the Uddehohn non-
polluting bleach plant developed in Sweden in 1975-1980(Billerud AB, Skoghall mill).However,the
process is currently not in use at the Skoghall mill(Fitch 1981).
Based-on information from Billerud,Sweden,the ion exchange technology worked very well in the
bleach plant.There were no problems in incinerating the ion-exchange elutate.However,because of
the high costs of the ion exchange resin,the costs of the process became very high. Therefore,the
company decided to shutdown the process and moved toward oxygen delignification and other
methods of cleaning effluents.
Other developers of ion exchange systems include Rohm and Haas (Fitch 1981) and Dow Chemicals
(Fitch 1981).
Their processes have been tested in pilot scale but no full-scale installations are known.
Risks
The risks with the ion exchange process are a)resin life time and plugging problems,and b) disposal
of elutate and associated chloride problems.
Treatment Efficiencies
The EPA tested the Billerud non-polluting bleach plant in pilot scale in 1980 (Fitch 1981).About 25
different organic components and 13 heavy metals were measured,as were the typical parameters
(COD,color,pH, and chloride).
Based on these results,the bleach plant effluent load reduction is estimated to be as follows:
• COD 65-70%reduction
• Color 90%reduction
• Chlorinated phenols 90-99%reduction
• Zn 40-90%reduction
• BOD 25%reduction
National Council for Air and Stream Improvement

Technical Bulletin No. 919 65
• Toxicity almost complete elimination
• AOX very high reduction.
Though promising,this technology has not been developed further for pulping effluents since the
1980s and does not appear to be an active area of investigation.
7.3 Activated Carbon and Activated Petroleum Coke Adsorption
Activated carbon has been used for removing organics from wastewater for many years. The
effectiveness of activated carbon in removing dissolved and colloidal material by adsorption is
primarily due to its extremely high surface area.Pore size distribution and surface chemistry also
determine the overall effectiveness.
Activated carbon treatment in the pulp and paper industry has been proposed primarily for color
reduction.High molecular weight organic compounds are typically amenable to carbon adsorption,
whereas colloidal compounds or strongly polar organic compounds(amino acids,hydroxyl acids,
sulfates,and sugars)are refractory to carbon treatment.Powdered activated carbon has a higher
surface area than granular carbon,which may improve color removal.
The PACTTM, or powdered activated carbon treatment process,has been developed by USFilter's
Zimpro division,which owns the trademark(http://www.usfitter.com/en/).Figure 7.6 shows
USFilter's PACT process.According to the PACT trademark,the process consists of"wastewater
treatment systems comprising aeration contact tanks,aerobic digesters,air diffusers,clarifiers,
clarifier drive mechanisms,scum collectors,waste sludge airlift pumps, scum removal airlift pumps,
flow measuring weirs,aeration blowers,recycle pumps, froth control pumps,polymer feed systems,
carbon eductors and/or motor control centers sold as a unit."The PACT process is also used at
DuPont's Secure Environmental Treatment(SET)commercial and industrial wastewater treatment
facility located at its Chambers Works site in Deepwater,New Jersey.One potential problem with the
PACT process was pointed out in a recent study(Kennedy et at.2000),which determined that PACT-
treated wastewaters were toxic to Ceriodaphnia dubia. The study concluded the toxicity was a result
of ingested PAC. Tertiary filtration was recommended.Another bench-scale study also
recommended tertiary filtration when powdered activated carton was used in activated sludge
treatment at 500-1000 ppm dosages(Narbaitz et al. 1996).
National Council for Air and Stream Improvement

66 Technical Bulletin No. 919
r_
=
Y Gnu
�h'lLs VIRGIN t'.l',v{' , ,+a�✓ n�"a JS 9
{q
TLTTE�g fi
STORAGE STORAGE.'P'
y.'rFy'S
9,r1 u � >-! _ ,•r � t rE .y- `. 9'�r 2 "��Y " SEMINO Y Ixh,`�: E� F � .1 f �`r�.l
F
-, CONfACTAERATION
TANK ,f
4 4
,It
ran � o{E r V a�v h k � dr12m bl
✓' r
v
OVERFLOW
))hs�• tk
E Y.+ ?+`r •r +tOR ORAL-� r r} � 1 _
Figure 7.6 USFilter's PACT System Process(Single-Stage,Aerobic)
Powdered activated carbon can also be combined with ultra-or microfiltration to remove dissolved
r species(Zhou and Smith 2002).The PAC is added to the recirculation loop of the membrane system.
-% PAC may also reduce the fouling of the membrane due to the surface scouring effect of the PAC
particles.
Recent studies have focused on less expensive alternatives. One investigation used delayed petroleum
coke,a waste by-product from the oil sand industry(Shawwa, Smith,and Sego 2001;see below).
Another novel source of activated carbon is coconut jute carbon(Singh 2006). Coconut shell husk
was used to produce activated carbon,which was then tested on pulp and paper mill effluent to
determine color removal. Color removal varied between 30-90%depending on pH,time, initial color
concentration,and amount of activated carbon added. Color reduction improved with increased time
(maximum at 100 minutes),increased adsorbent concentration,and higher initial color concentration
and reduced pH(maximum at pH=2).Dosage was 0.6 g/100 ml or 6000 ppm.
Color Removal from Bleach Plant Effluent using Activated Petroleum Coke(Shawwa,Smith,
and Sego 2001)
One laboratory study addressed the removal of color from bleaching effluent using activated carbon
obtained from delayed petroleum coke.The study found that there was an abundant and cheap supply
of delayed petroleum coke available in western Canada. The petroleum coke was ground into
powdered form and activated in a two-stage process. The carbonization stage was carried out at 850°C
followed by a steam activation stage that lasted 1-6 hours.The activated petroleum coke was tested
using bleach plant effluent.The activated petroleum coke was shown to be effective in removing
color and AOX.Applications of 2,500 mg/1 of powdered activated petroleum coke resulted in about a
30%reduction in color and AOX.Applications of 15,000 mg/t of powdered activated petroleum coke
resulted in about a 90%reduction in color and AOX.
National Council for Air and Stream Improvement

Technical Bulletin No. 919 67
�— The petroleum coke was subjected to various activation periods (2,4, and 6 hours)and then used to
treat bleach plant effluent. The characteristics of the bleach plant effluent are presented in Table 7.3.
Table 7.3 Bleach Plant Effluent Characteristics
Parameter Unit Value
COD mg/l 2126
DOC mg/1 575
AOX mg/1 as Cl 80.2
UV254 nm(cm") 13.11
Color465 nm(mg/l Pt-Co) 2300
pH 2.1
Batch testing was then conducted to generate adsorption isotherms using the bleaching effluent. The
color removal,based on a 2-6 hour reaction time, is shown in Figure 7.7.
Based on the figure,the activated carbon produced using a 4-hour activation period provided the
maximum color reduction.Dosages of up to 2500 mg/1 produced a maximum color removal of 33%.
Higher color removal required higher activated carbon dosages. The use of activated petroleum coke
appeared to remove the recalcitrant portion of the organic matter in the bleach plant effluent.This
would make the remaining effluent more susceptible to biological treatment.
Sludge handling was not addressed in this study.
i' 2500
—E— 2 hours
2000 a 4 hours
..1
—a— 6 hours
1500
E
O
U 1000
500
0
100 500 1000 5000 10000
Activated-Coke dose (mg/L)
Figure 7.7 Color Removal at Different Activated Coke Dose and Activation Periods(Shawwa,
Smith,and Sego 2001)
i
National Council for Air and Stream Improvement

68 Technical Bulletin No. 919
�- Powdered Activated Carbon Addition to Total Mill Effluent
The Appleton Papers mill in Roaring Springs,Pennsylvania,has conducted a full-scale trial with
powdered activated carbon addition.The mill is an integrated hardwood kraft mill producing about
300 Tpd of paper.The mill's wastewater treatment system(4.5 MGD,color concentration 250-300
PCU) (Simmers 2005) consists of a bar screen, and primary clarification(2 clarifiers), followed by
two aerated lagoons in series.The overflow from the second lagoon goes to two aeration tanks and a
re-aeration tank before going to final clarification(3 clarifiers). The mill conducted tests with a
variety of coagulants, oxidative processes, and carbon absorption to determine their effectiveness at
color removal. For coagulants,the mill tested ferric chloride,ferrous sulfate,ferric sulfate,time
combinations, and polymers. For oxidative processes,the mill tested hydrogen peroxide, ozone,
ultraviolet light treatment, and ultraviolet light with hydrogen peroxide.The target was to reach a
color concentration of<200 PCU(Simmers 2005).
For carbon absorption,the mill tested various granular and powdered activated carbons on final
clarifier effluent.The most promising results were obtained with powdered activated carbon,which
consistently reduced the effluent color to 150-200 PCU.The mill conducted a full-scale test adding
powdered activated carbon to the final clarifiers. The powdered activated carbon was slurried with
water and added at the aeration tanks.During the trial the feed rate varied from 0.5 to 1.0 Tpd of
carbon(27-56 ppm)(Simmers 2005).It was found that the addition of powdered activated carbon
reduced color and BOD.The sludge from the clarifiers was dewatered by a press and then incinerated
in the mill's power boiler.The amount of powdered activated carbon in the effluent was not
determined.The mill is now considering a full-scale implementation of powdered activated carbon
addition. When used in the biological process,the carbon becomes part of the biological sludge and is
dewatered and handled in the same processes as the other sludges.
a One of the study mills in this survey undertook mill-scale trials with activated carbon added to
different locations throughout the effluent treatment process.The sludge handling during these trials
performed as normal,and no special difficulties were experienced.
7.4 Electrodialysis (ED)and Electrodialysis Reversal(EDR)
In the electrodialysis(ED)method,the electrolytes in a water solution are separated with the aid of an
electrical current and a membrane.The achievable separation result depends first on the magnitude of
applied electrical current and the available size of membrane,and secondly on the ion strength of the
solution.
An electrodialysis system consists mainly of the electrodialytic membrane stack,pumps, and
membrane cleaning system.
Electrodialysis has been proposed as a method of closing up the bleach plant. One study looked at the
laboratory treatment of bleach plant acid stage effluent using ED to remove non-process elements and
then return the treated filtrates to brownstock washing(Tsai et al. 1999).Figure 7.8 shows the
configuration proposed in this study.Electrodialysis could also be combined with other membrane
processes such as the treatment of nanofiltration permeate by ED and then reuse in the mill(De Pinho
et al. 1996). Electrodialysis is a commercial technology used for desalination of water and the
treatment of various types of industrial effluent,but there are no known applications in kraft mills.
�1
National Council for Air and Stream Improvement

Technical Bulletin No. 919 89
Weak black liquor NNGH,Or
To chemical recovery I fg,steam
(water,inorgardes,IWO
4 --- �
Brown pulp Os f
(from digester) wash deligni- wash
n '
brow stock fication
i t
washing L—___ r
--' —— ————— —*
r --- ---—-—-t r--Water
I
D wash ' $ wash D wash
J
! -t
nor Acidic elauent NaOH. ————— — ————
fl,o (conwim most mewls, Q02
St. musitim metals, Ha0 11,0
chloride) steam Bleached
tau up
Inorganic
pulp
wkeup lnorgaNc PPEa (to Paper
Remove
a N ulysis:
Re NIrE's,tL¢nreryele To newer making)
Figural: Schematic of a generle bleached krah pulp bleaching operation with water recycling(D:chlorin dioxide
bleaching stage,E:caustic extraction sup).
r
Figure 7.8 Electrodialysis (Tsai 1999)
The electrodialysis reversal(EDR)process operates on the same basic principle as ED,where an
electrical current supplies the driving force to transfer electrolytes through an ion-change membrane.
However,the EDR process includes polarity reversal that provides self-cleaning of the membrane
surfaces as part of the process. The EDR process can be used to remove COD and color. EDR has
been used commercially;however,there are no known applications in the pulp and paper industry.
8.0 COLOR REMOVAL—CHEMICAL PROCESSES
Chemical coagulation and solids separation of biologically treated effluent is a method to reduce
dissolved residual components such as color,COD,AOX and nutrients.By adding organic coagulants
or Me}+(Fe,Al)salts,larger dissolved organic molecules can be precipitated out of the solution.Floc
formation and ability to settle are often enhanced by adding a separate organic polymer prior to solids
separation.The treatment involves the addition of a coagulant and a polymer,pH control(if metal
salts are used),separation of the formed solids in a dissolved air flotation unit or in a conventional
clarifier, and sludge disposal.
The addition of chemicals to the effluent treatment,especially in larger quantities,has to be evaluated
from all aspects,including the toxicity of the specific chemical used in order to avoid potential
effluent toxicity issues.
8.1 Lime Precipitation
Precipitation with lime has been used to reduce effluent color.Lime treatment has been effective in
industry trials for color removal(Ganjidoust et al. 1996;Roux and B61rmer 2000). Other parameters
would be reduced as well,including COD (60-70%),P,and organic solids.Lime treatment typically
National Council for Air and Stream Improvement

70 Technical Bulletin No. 919
requires higher dosage than alum treatment and generates more sludge.A considerable amount of
research was devoted to the development of lime treatment processes in the late 1960s and 1970s.
Basically,there were"minimum lime"and"massive lime"processes. A few installations were built
in the U.S. (Baird 1995). Essentially,the processes were similar to the raw water lime treatment.
Rebumt lime was used as the precipitating agent. In the massive lime process,the precipitated sludge
containing lignin, other organic material,and the used lime was regenerated in a dedicated lime kiln
or it was combined with the mill's lime sludge. In other processes,separate sludge handling was .
attempted.The large dosages of lime that were needed to achieve an acceptable treatment efficiency
resulted in very large quantities of sludge.The difficulties involved in the sludge dewatering
eventually led to the discontinuation of the efforts to develop lime treatment of effluents.
A more recent study on lime precipitation looked at the effectiveness of lime precipitation prior to
biological treatment(Roux and BShmer 2000).Both lab-and pilot-scale studies were conducted on
spent OZ delignification liquor,foul condensates,and total mill effluent.Color removal of about 80%
was achieved. The optimum pH range was 10.5-12.5 with retention times of 1-2 hours. Lime
precipitation worked best when the calcium concentration was above 1000 mg/1.
One of the study mills in this survey attributes about 30%color removal in the effluent treatment
system to the presence of lime in the influent. The mill adds 40 tpd of lime(about 320 ppm)to
neutralize the mill effluent.Any precipitate is removed in the primary and secondary clarifiers with
the sludges and taken to landfill. That mill does not experience any special issues with the sludge
handling.
8.2 Alum Precipitation
8.2.1 Industry Applications
One of the study mills adds an aluminum-based salt to its activated sludge process for color control.
The addition is controlled depending on the season, and varies between 40 and 88 ppm.The color
reduction in the activated sludge process increased by about 30%when the Al-salt was added.
Most of the installations utilizing alum treatment are tertiary treatment installations,using aluminum
and/or iron salt with or without polymer addition as a coagulant(mechanical/recycled paper mills).
The main drawback of the coagulation/precipitation methods has been the disposal of the formed
sludge. The volume of sludge can be significant,especially if metal coagulants are used.Also,the
dewatering characteristics of the sludge are typically poor.
Arauco's Valdivia bleached kraft pulp mill in Chile uses aluminum sulfate for tertiary treatment of its
effluent(Rodden 2005a). The tertiary treatment is mainly for the removal of color.The chemical
sludge from the tertiary treatment is currently landfilled, although future plans call for composting the
sludge.No information about the equipment for handling of the tertiary sludge as found in the
literature. The primary and secondary sludge is dewatered on belt presses and incinerated.
8.3 Iron Precipitation
One example of tertiary treatment using iron is the FennoTriox process by Kemira. FennoTriox uses
both oxidation and coagulation to remove pollutants. The FennoTriox process uses ferrosulphate(a
waste) in combination with hydrogen peroxide(Fenton reaction)in a chemical effluent treatment
plant. The reactions between the metal salt and peroxide will produce radicals that can oxidize
organic compounds in the effluent.
National Council for Air and Stream Improvement

Technical Bulletin No. 919 71
In the FennoTriox system, all chemicals are introduced into a reactor with a mixing zone and a
reaction section. The flocs generated in the reactor are removed in the flotation unit following the
reactor. The retention time is 10-30 minutes in the reactor and 3-5 minutes in the flotation unit. The
removal of organics and nutrients is claimed to be more efficient than with conventional coagulation.
The sludge from this process(0.2-0.5 kg/m3 effluent) could be landfilled or burned.
Laboratory testing of biologically treated kraft mill effluent(following AST)resulted in the following
reduction efficiencies with the FennoTriox process (Syvapuro 1994):
• COD 92%
• AOX 88%
• Chlorinated phenolics 57%
• N 85%
• P 98%
Other laboratory testing of the FennoTriox process showed color removal rates of 90-95%.
No full-scale applications of the FennoTriox process are known.Tertiary treatment with ferric—
aluminum sulfate(AVR)without hydrogen peroxide is done in a few Scandinavian mechanical pulp
and paper mills for phosphorus control.
8.4 Polymer Precipitation
Polymers have been used in primary,secondary, and tertiary coagulation and flocculation treatment
of industrial effluents.
Two of the study mills in this survey use polyamine to remove color. One mill adds polyamine to a
spare clarifier that contains diverted highly colored effluent.The other mill adds polyamine to a
process effluent stream that contains mainly black liquor.About 4700 lb/d is added to 17000 gpm of
effluent(23 ppm)to remove about 100 t/d of color.
One polymer treatment process used in the pulp and paper industry is the Smurfit-Stone Container
Corporation's color removal process. he process is covered by U.S.patent 4,738,750,which states
"A system and method for converting pulp and paper mill waste water into a
decolored,neutral pH effluent and.a solid suitable for use as fuel in a furnace. The
treatment system is used following primary and secondary treatment of pulp and
paper mill waste waters typically found in the industry. After secondary biological
treatment,the waste waters are pumped to a coagulation tank where the waste water
is brought in contact with a polyamine coagulant which coagulates lignins,degraded
sugars,and other compounds which typically discolor this water.The coagulation
particles are increased in size by addition of an acrylamide polymer in a flocculation
tank to improve the hydrophilic characteristics of the coagulant.The waste water is
then mixed with a dissolved air and water solution under pressure.Upon dissolution
of the dissolved air at atmospheric pressure the air is absorbed by the flocculated
matter in the aeration tank and the flocculated matter is caused to migrate towards the
area of less pressure, i.e.,the surface of the tank.The flocculated matter accumulates
on the surface of the flocculating tank and can be skimmed from the top,dried and
ultimately burned in a furnace."
National Council for Air and Stream Improvement

72 Technical Bulletin No. 919
i
This process uses an organic polyamine as a coagulant targeting color precipitation and
polyacrylamide as a flocculant. Since the formed sludge is almost purely organic(lignins),
incineration in the recovery boiler has become possible while increasing heat recovery and reducing
sludge disposal costs. In bleached kraft mills,however,the incineration of chlorine-containing sludge
could lead to increased chloride levels in the white liquor loop,resulting in corrosion and boiler
plugging problems. In recovery-limited mills, adding solids to the black liquor would also potentially
reduce the pulp production capacity.
Smurfit-Stone Container Corporation has used this process at their mills in Missoula,Montana and
Hodge,Louisiana.The corporation also has a patent(U.S.patent 4,724,045)for the removal of color
from alkaline pulp and paper wastewaters using a polyacrylamide coagulant.
The Stone process is also used at the mill in Skookumchuck,British Columbia(Hodgson et al. 1997;
Stevenson 1995). The Skookumchuck mill has a river-based color limit. With the Stone process,they
report color removal rates of 55-80%depending on effluent characteristics and polymer type.The
mill has also reported reductions in other parameters,including BOD, suspended solids, COD (22%
removal), and AOX(23%removal).The sludge from the flotation unit is returned to the black liquor
evaporators where it is combined with the black liquor and incinerated in the recovery boiler. Figure
8.1 shows the process used at the Skookumchuck mill. Because of the high cost of the polymer
treatment,the mill has studied the recycling of the Eop filtrate as an option to reduce effluent color
(see Section 6.2.2.3).
Figure 8.1 Color Removal Process Used at Skookumchuck(Hodgson et al. 1997)
r To 0utla� t •�
11
TRYh110111
666
y
Cwputant,+=�' � ..., R .-� e. }•.;..� r ly�r,`.Fbu9onCluNr
I—,
�. y
u L
dU1R1AL1! <<4_ � m �BIMJ�1.fQJOf`rB(Jt fa
4
8.5 Nitric Acid Precipitation
Nitric acid has been used in laboratory and pilot tests for color precipitation(Roux and B61mer
2000). The effluent was acidified to a pH of 3 and then a polymer was added.The precipitate was
removed using a dissolved air flotation(DAF)unit.The tests were conducted using untreated whole
mill effluent.It was found that the color in effluents containing high amounts of black liquor was
easily,removed by precipitation with about 80%color removal.The DAF unit was required because
National Council for Air and Stream Improvement

Technical Bulletin No. 919 73
_4
the precipitate formed from nitric acid treatment did not settle well. In addition,the acidification of
the effluent caused the formation of HZS,which could cause odor problems. This technology has been
tested in pilot scale only and there are no know commercial applications of this technology. Use of
nitric acid would add to the nitrogen load on the effluent,which could be a potential problem.
8.6 Electrochemical Treatment
Electrochemical treatment involves the use of sacrificial iron electrodes.A current is applied across
the electrodes,which creates iron ions at the cathode and hydrogen and hydroxide ions at the anode.
The iron ions then form flocs of Fe(OH)2 onto which the color is adsorbed.The flocs can then be
removed by clarification. Electrochemical treatment has been used industrially in the textile and
carpet industries to remove dyes and heavy metals from wastewaters.The sludge recovered from the
process would have to be dewatered and disposed of.In laboratory tests of mill effluent color,
reduction ranged from 60-90%for electrochemical treatment(Springer, 1995)and up to 95%for
electrochemical treatment combined with a polymer(Orori et al. 1995). Toxicity was also reduced in
one study. Operating costs included energy,sludge disposal, iron for the electrodes and acid for
cleaning the electrodes.
8.7 Summary of Chemical Treatment
Table 8.1 presents data on some installations where chemical treatment is used as tertiary treatment.
National Council for Air and Stream Improvement

Table 8.1 Full-Scale Installations of Coagulation as Tertiary Treatment a
State/ Targeted Chemical
Prov. Source m3/d Parameter
Stone Container Missoula MT USA UBK/10%BK Stone 1988 7 mo/yr 38,000 Color Polyamine—
Corp. Stone Process
Stone Container Hodge LA USA UBK/NSSC Stone 1985 dry 53,000 Color Polyamine—
Corp. season Stone Process
Crestbrook Industries Skookumchuck BC Canada BK Stone 1994 cont. 38,000 Color Polyamine—
m Stone Process
0
y Arauco Valdivia Chile BK Tertiary 2005 Color AI-compound
Study Mill USA BK Activated Color Similar to PAC
Sludge
add'n
° SCA Ostrand Sweden CTMP Fennottiox 1995 intermit. 3,600 COD,P FeSO4/H202
D
m M-Real Kirkniemi Finland CTMP/GWD Tertiary Cont. 10,000 COD,P AVR'
co StomBlllerudFors Fors Sweden CTMP/GW Tertiary cont. COD,P AVR]°
m
AB
d
3 Holmen Paper AB Braviken Sweden TMP/GW Tertiary COD,P AVR'
v Holmen Paper AB Hallsta Sweden TMP/GW Tertiary o P COD,P AVR
3 Stora Feldmuhle Hylte Sweden TMP/GW/SI Tertiary COD,P AVR'
Hvltr AR
United Paper Mills Jamsankoski Finland TMP Tertiary only COD,P m
Ltd. emerg.
Savon Sellu Ltd. Kuopio Finland NSSC Tertiary On d
occasion �o
c
a ferric aluminum sulfate (D.
Z
0
m
m

Technical Bulletin No. 919 75
9.0 COLOR REMOVAL—OXIDATION PROCESSES
Recent research has focused on the use of advanced oxidation processes(AOPs)to treat either whole
mill effluent,bleach plant effluent,or effluent from specific bleaching stages. AOPs include Fenton
and photo-Fenton reactions,peroxide(H202)treatment, ozone treatment, ozone with H202 or UV
light or both,and heterogeneous photocatalytic processes (such as titanium dioxide photocatalysis).
Some of these processes will be reviewed below.
9.1 Peroxide
9.1.1 Peroxide Treatment ofEop Filtrate
Peroxide treatment has been used commercially to treat various wastewater streams.
Treatment of the EoP-Filtrate with hydrogen peroxide has been used at the mill in Grande Prairie,
Alberta since 1997 (Wohlgemuth, Lam,and Willis 1997).
Figures 9.1 and 9.2 show the effect of peroxide treatment on EoP filtrate for non-oxygen delignified
pulp. Chemical oxidation with peroxide(H202)oxidizes certain structures of organic compounds and
hydrolyzes large molecules into smaller units,thus reducing color. Some components are fully
oxidized to carbon dioxide and water.Color removal is not proportional to peroxide dosage.With
higher dosage the chemical becomes less efficient.The required dosage increases exponentially as a
function of color removal,which enables one to determine the maximum reduction achievable with a
reasonable dosage.
Effluent eoIour vs Past Treatment M202
uoo
3000
2500
a I �
v =0MU • s
loc
1000
a
0 2C0 400 "a No 1000 1200
H2O21ppm)
KF»0!.20 0 KF=0.22•KF=0.271 Eop M02-0.4%
Figure 9.1 Post-Color Treatment Efficiency(Wohlgemuth,Lam, and Willis 1997)
National Council for Air and Stream Improvement

76 Technical Bulletin No. 919
l
(30
'Removal %
50
40
30
20
10
0
0 150 300 4W 600 750 900 1050 1200 1350
H2O2 Charge, ppm
KF=O.16-e-KF=0.2- KF=0.251
Figure 9.2 Post-Treatment Color Removal Percent Efficiency(Wohlgemuth 1999)
The major advantage of this technology is the low capital cost involved. Also,the process is easy to
operate and the influent color can be.controlled to a desired level.
The peroxide treatment system at the mill in Grande Prairie included mixing of the aqueous peroxide
solution with E-stage filtrate leaving the seal tank.The mixture was allowed to react in a retention
tank for 0.5-1 hour before being discharged to the sewer.The system included the following main
equipment: a)peroxide delivery system retention tank,and b)level and dosage control systems.
This system is currently not in use after installation of oxygen delignification.
The peroxide treatment technology is simple,involving primarily the mixing of chemicals and
retention of the mixture. Up to 30-50%reduction of E-stage color has been reported to be achievable
(Wohlgemuth,Lam,and Willis 1997).Peroxide treatment can also reportedly reduce BOD and COD
(Robinson 1994).
9.1.2 Enhanced Peroxide Treatment with Catalyst of Et Stage Effluent
This process is similar to peroxide treatment except that a catalyst is added to the reactor to enhance
the treatment. Catalysts(TAML)are currently being developed at Carnegie Mellon University
(Wingate et at.2001,2004).
TAML(tetra amido macrocyclic ligand)iron(III)catalysts are one-time use hydrogen peroxide
activators. By using TAML catalysts with hydrogen peroxide,color and AOX can be removed from
E-stage effluent.
U
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Technical Bulletin No. 919 77
Bench-scale and pilot-scale tests have been conducted on softwood(pine)and hardwood(eucalyptus)
E-stage effluent at a kraft mill in New Zealand. The TAML catalysts function best under alkaline
conditions and with efficient agitation to achieve the maximum color removal. The pilot plant tests
consisted of two vessels, a 200 L vessel with a hydraulic retention time of one hour, and an 800 L
vessel with a hydraulic retention time of four hours.
The vessels were operated in series with a flow rate of 3.3 L/min and chemical addition to the first
vessel. It was determined that a reaction time of one hour provided suitable color removal. Table 9.1
shows the results of the pilot testing.As can be seen in the table,the TAML catalyst is more effective
for softwood(pine) effluents than for hardwood(eucalyptus) effluents.
Table 9.1 TAML Catalyst Pilot Plant Results on Bleach Plant Alkaline Effluent'
Chemical Application Parameter Color AOX
0.5 µM catalyst,6.5 mM HZOZ,pine Influent 18±4 0.41f0.11
(0.23 mg/1,catalyst, 190 mg/I H202) TAML treated 10-0 0.3410.05
Removal(%) 46 -
1 µM catalyst, 13 mM HZOZ,pine Influent 2313 0.38f0.10
TAML treated 8t1 0.31i0.09
Removal(%) 67
2 µM catalyst,22 mM HZOZ,pine Influent 2513 0.38f0.04
TAML treated 611 0.26f0.04
Removal(%) 78 32
2 µM catalyst,22 mM HZOZ,eucalyptus Influent 2.9t0.04 0.2210.09
TAML treated 1.610.3 0.12f0.06
Removal(%) 45 -
°Conditions: pH 11.8, lhr,60°C
In previous work,the authors of the study noted that the addition of hydrogen peroxide alone caused
an increase in the color at400 not wavelength due to the formation of a finely divided precipitate.
The TAML catalyst is short lived and degrades after about 10 minutes at the reaction conditions.
Therefore,Microtox toxicity testing was also done on the pilot plant effluent to determine if the
catalyst degradation products impacted effluent toxicity and no toxicity was found.
Experiments have also been undertaken using the TAML in the Ep stage in the process (Horwitz
2005).
A summary of the chemical dosages for about,30%color reduction using TAML/112O2 color was
given in the 2005 NCASI Effluent Color Management workshop(NCASI 2005):
Eop filtrate treatment (825 ADT/d @ Eop filtrate 1.8 MGD):
13.5 lb FE-TAML/d(0.016 Ib/ADT) and 0.5 T H202/d(0.06%)
Eop tower treatment (300 ADT/d)
2.5 lb FeTAML/d(0.008 Ib/ADT)and 0.65—0.75%H20, on pulp
Currently,this technology is not commercially viable because the TAML catalyst is not produced on
�7 an industrial scale. When the TAML was added to the Eop tower,the catalyst use was lower than
National Council for Air and Stream Improvement

78 Technical Bulletin No. 919
^� when the Eop filtrate was treated.The TAML may thus be more effective when added in the
bleaching process.
9.2 Ozone
9.2.1 Ozone Treatment
Process and Applications
Ozone is a gaseous oxidant with a high oxidation potential, second only to fluorine,preferentially
attacking compounds which consist of carbon-carbon double bonds (color causing structures) and
organic functional groups.Any umeacted 03 decomposes rapidly to 02. The reactivity of ozone is not
dependent on temperature and favors lower pHs. Therefore, ozone treatment may be applied on the
total effluent as well as on any particular stream.
A small paper mill in Germany called BOttenpapierfabrik,which produces about 5,000 tons/yr of
colored paper,uses ozone to decolorize their effluent.The ozone also gives a 10-20%reduction in
COD and reduces AOX..This allows the mill to reuse part of their effluent for process water(Webb
2002).
The ozonation process includes the ozone generation and ozone dissolving into effluent. Ozone is
generated from dry air or pure oxygen by a high voltage electric discharge. The generator outlet gas
stream may contain up to 12%ozone.The gas is dissolved into the effluent by means of diffusers or
other equipment.
Ozone could be added to the D or Eop stage effluent or the total mill effluent.The gas would be
- - dissolved into the effluent by means of diffusers or other similar equipment in an airtight tank with a
�y J detention of approximately 10-20 minutes. Any residual ozone in the off-gases would be destroyed
before venting to the atmosphere.
The scope includes the following main equipment: a) ozone delivery system,b)retention tank, and c)
off-gas treatment unit.
The production of ozone is proven technology. Ozone treatment of water for disinfection purposes is
a well-established technology employed at several municipal water and wastewater treatment plants.
In the pulp and paper industry the D and E stage and total mill effluents have been targets for much
lab-and pilot-scale testing with ozone.However,no full-scale ozone effluent treatment has been
installed on kraft mill effluents.
The potential environmental risks are related to these following:
• color reversion in ASB;
• possible BOD increase;
• environmental impact of 03 oxidation products;and
• residual ozone air emissions.
Impact on Color when Treating Bleach Plant Alkaline Filtrate
A 60%reduction of E-stage filtrate color would be expected,assuming no color reversion in
secondary treatment.Literature results are varied on color reversion,with some studies showing
reversion,some no change, and some further color reduction in the treatment system.In one study,
ozone was applied to the alkaline bleach plant effluent from a bleached kraft mill(Bijan and Mohseni
✓� 2003).The characteristics of the bleach plant effluent are presented in Table 9.2.
National Council for Air and Stream Improvement

Technical Bulletin No. 919 79
Table 9.2 Bleach Plant Effluent Characteristics (Bijan and Mohseni 2003)
Parameter Unit Value
BOD5 mg/1 282.2
COD mg/1 1586.3
TC mg/1 676.6
pH 11.03
Color C.U. 1542.7
Figure 9.3 shows the color removal from the alkaline bleach plant effluent for bench scale testing.
Color removal of up to 70%was achieved in the testing.
1800 - -�
1600 - -
1400 •
1200
`c
1000
I p 800
U
600 —
400 --
200
0
0 0.1 0.2 0.3 OA 0.5 0.6 0.7 0.8 0.9
Ozone dosage(mg 03fmL wastewater)
Figure 5: Color removal of alkaline bleach plant effluent during ozonation(T=20°C,pH= 11,
inlet gas flow rate= 185 mUmin,03 concentration in the input gas=0.11 mg/mL)
Figure 9.3 Color Removal from Alkaline Bleach Plant Effluent(Bijan and Mohseni 2003)
Impact on Color When Treating Combined Mill Effluent
Ozone treatment can reduce up to 80%of whole mill effluent color with an inlet ozone concentration
of up to 3.0%by weight according to results from pilot-scale tests with ozone at a softwood kraft pulp
mill(Zhou and Smith 1996).Bench-scale testing used effluent from a stilling basin following an
aerated lagoon. The characteristics of the whole mill effluent are presented in Table 9.3.
National Council for Air and Stream Improvement

80 Technical Bulletin No. 919
Table 9.3 Whole Mill Effluent Characteristics(Zhou and Smith 1996)
Parameter Unit Value
COD mg/1 485
BOD5 mg/1 11
TOC mg/1 192
AOX mg/1 7.77
Color TCU 943
pH 7.62
Total Mn mg/1 0.62
The color removal for an inlet gas flow rate of 1500 ml/min and an ozone concentration of 3.0%by
weight is shown in Figure 9.4.
1000 20
[7Cc;.u,:
g00 16
60012
O
4008
200min 4
Av %)
0 0
0 3 6 9 12 15
Time, min
Figure 9.4 Color Removal versus Contact Time for Whole Mill Effluent(Zhou and Smith 1996)
Pilot testing on whole mill effluent using ozone was also conducted at the Tenneco Packaging
containerboard mill in Valdosta,Georgia(Lovell, Stein,and Schmadel 1997). Color removal of about
90%was achieved.
�J
National Council for Air and Stream Improvement

Technical Bulletin No. 919 81
BOD
The breakdown of organic molecules increases the potential of BOD formation(Zhou and Smith
1996),by one estimate increasing the raw BOD load to treatment by 5-10%. This low molecular
weight BOD may,however,be treated more easily with biological treatment,so the net impact on
BOD may be low.
COD and TDS
As a result of oxidation, COD and total dissolved solids may be reduced by approximately one-third
of the ozone dosage.
9.2.2 Ozone/UV Treatment
The ozone/UV treatment processes use UV photons to activate ozone molecules to form hydroxyl
radicals.The hydroxyl radicals then oxidize pollutants in the wastewater.In laboratory experiments,
bleach plant and total mill effluent exposed to sunlight have been decolorized and dechlorinated(i.e.,
AOX and COD have been reduced),and high molecular weight material(HMW)has been degraded
(Sonnenberg et al. 1994).Both UV and visible light contribute to this process.In a UV or ozone/UV
process,effluent would be exposed to ultraviolet radiation in an exposure/reaction chamber.This
process is still in the research phase.Initial results indicate that pH,light intensity,exposure time and
BOD/COD ratio are important process parameters.In the ozone/UV process,03 consumption is much
higher than with 03 treatment alone.This makes the 03/UV process less economically attractive
compared to 03 treatment alone or ozone/peroxide or peroxide/UV processes(Zhou and Smith 2002).
9.2.3 Ozone with Biological Filtration
This process is applied at a paper mill in Germany (Schmidt and Lange 2000). The tertiary treatment
step consists of ozone treatment followed by biological filtration.The ozonation stage consists of two
reactors in parallel. Ozone is mixed with the wastewater and flows into the reactor.The off-gasses
from the reactor are used as such,i.e.,no off-gas destruction,in an AST.The wastewater from the
ozone reactor flows to a holding tank with a 1.5 hour retention time that allows the remaining ozone
to dissipate and protects the biofilter from ozone shock.The biofilters consist of three rotating filter
units with air and wastewater feed to the bottom and a design speed of 4.5 m/h. The system was
designed to minimize COD and BOD discharges.
The mill's entire treatment system consists of primary clarification,equalization,AST,secondary
clarification,ozonation,and biofiltration. The entire system operates at approximately 98%BOD
reduction efficiency and approximately 85%COD reduction efficiency. The treatment volume is
small, 14,000 m3/d(3.7 MGD),and there is no pulp mill at the site.Figure 9.2 shows the treatment
system at the mill.
National Council for Air and Stream Improvement

82 Technical Bulletin No. 919
)
�. �14!000m'Id IQ Sd00vPld " rvctiv ycy:a gym' ude;
Via... 1992 e3D Q 26i
COO �23.000Y�Id. COD'10 T70 kgld -
BOB--i1A I&M •BOD- 53i3kN" t. .
•55.:.,31,ODOkgN' ;55�=- 327 kgld,i ordm-
aedimeduivel - � , "
r I..
.�eSEa�' eid
eEBvmt _ pr.
room kdvy,Yvdg 2' ud
imurnl f x (PremY6m)• 2 ' ..7t'
Pits' F- -
' "Ev3.
' ` cWal. ICKtivn ro .
• � .. If i s�`.Y.
.M•nuch) �� '.� fwenneo - i... ' pear•
' 7iro� - Y, caouin "iankn
Figure 9.5 Ozone and Biological Filtration at a Paper Mill(Schmidt and Lange 2000)
f 9.2.4 Heterogeneous Photocatalyst and Ozone Treatment
Heterogeneous photocatalysis involves the irradiation of a semiconductor anode,such as titanium
dioxide(Ti02),with ultraviolet light with a wavelength less than 390 nm.The light source can be
either sunlight or UV lamps.This process is thought to create hydroxyl radicals that react with the
organics in the effluent. Several variations of the heterogeneous photocatalysis process have been
experimented with,including combined 03/UV heterogeneous photocatalysis treatment and
photocatalysis with Ti02.Although 03/UV experiments were based on bleach plant effluent,this
process could be used on the whole mill effluent as well.In the 03/UV heterogeneous photocatalysis
process,the ozone increases the production of hydroxyl radicals and thus improves the treatment
efficiency.The combined 03/UV heterogeneous photocatalysis provided the same treatment
efficiency as ozone and UV heterogeneous photocatalysis applied in sequence,but the time required
for reaction was much lower(Torrades et al.2001).
Other laboratory experiments using a Ti02 slurry and an Hg vapor lamp as a light source were
conducted with a variety of mill obtained effluents after primary treatment(Almquist and Boyd
2004).This research looked at photocatalysis only(without ozone)and its effect on COD,BOD5 and
toxicity(Microtox test).After an 8-hour treatment,the kraft mill effluent COD was reduced by 40%,
BOD by 30%and toxicity by 35%.The color of the effluent was also reduced,but not measured.
Reductions were larger for mills using other types of pulping processes. Other studies(Torrades et al.
2001)have shown that the combined ozone-photocatalysis process is more effective than each
process individually or in sequence.
This process is still mostly laboratory scale(Zhou and Smith 2002).For this process to be
commercially viable,several areas will need to be addressed,including reactor design and catalyst
immobilization.
National Council for Air and Stream Improvement

Technical Bulletin No. 919 83
9.3 Wet Air Oxidation with Catalyst
9.3.1 Process and Applications
Under conditions of moderate temperatures(200-650°C) and elevated pressure(100-250 bar)
dissolved and solid organics can be oxidized in the presence of water and oxygen in a process called
super critical water oxidation(SCWO).Depending on temperature,pressure and residence time,
organic compounds are broken down into smaller molecules and eventually to carbon dioxide,water
and inorganic acids.Figure 9.3 shows an example of super critical water oxidation(Cooper et al.
1996).
Experiments have been conducted on the use of wet air oxidation(WAO)with a catalyst(Zhang and
Chuang 1999).By using a catalyst like Pd-Pt-Ce/alumina,much milder reaction conditions, 130-
170°C and 15 bar for 3 hours, can be used. Without a catalyst, oxidation would not occur under these
conditions.The milder conditions also allow the use of carbon steel process equipment(Zhang and
Chuang 1999).Figure 9.4 shows color removal in laboratory tests of combined Do and EoP stage
effluent.
LIQUID
OXYGEN
TANK
WASTE
WASTE BYPRODUCT LIQUID
TANK CO2 STORAGE OXYGEN
PUMP
1 RECIRCULATION&
HOMOGENIZATION OXYGEN
02•CO2 VAPORIZERS MED.PRESS.
SEPAR TOR SEP
HP
FEED
PUMP VENT
COLdPRE550R MAKEUP 02
02 ACCUMULATOR LOW PRESS.
COOLER HIGH SEP.
RESS,
PREHEATER REACTOR COOLER SEP.
P.OILER AQUEOUS
OJSOUD EFFLUENT
HEAT RECOVERY SEP.
RECIRC. LOOP
PUMP
SOLIDS
STORAGE
Figure 9.6 Super Critical Water Oxidation Process Developed by MODEC(Cooper et al. 1996)
National Council for Air and Stream Improvement

84 Technical Bulletin No. 919
14
100 I
,
13
80
12
o 11
60 I 10
0 40 • �6 �9 —i
�o 20 /
4�4 6
0 15
0 20 40 60 80 100 120 140 160 180 200
Run Time, min
FIGURE 4. Color and pH versus reaction time profile at 443 K and
1.5 MPa with 1.0 g of catalyst.
Figure 9.7 Color Removal with Pd-Pt-Ce/Alumina Catalyst(Zhang and Chuang 1999)
Several catalysts have been investigated,including various iron and zinc oxide catalysts.These have
suffered from several problems,including catalyst deactivation due to dissolution in acidic effluents,
which would require an additional step to remove the leached metal ions.To combat this,the
combined bleach plant effluent,which has a higher pH, can be treated.This reduces the leaching of
metal ions from the catalyst.
This process results in a significant reduction in color and TOC. Because most of the color removal
occurs in the first hour of reaction, a short treatment time could be used as a preliminary step
followed by biological treatment.Super critical water oxidation has also been proposed as a treatment
for the concentrate from ultrafiltration or reverse osmosis (Hauptmann, Gaims,and Modell 1994).
9.3.2 Technical Feasibility
Wet air oxidation is a commercial process with a few installations in the pulp and paper industry.The
Zimpro(wet air oxidation)process is employed at the Weyerhaeuser mill in Rothschild,Wisconsin
for sludge conditioning,a mild version of wet oxidation.At the Stora-Enso mill in Kimberly,
Wisconsin(Jortama 2003)wet oxidation enables the recovery of filler from waste activated sludge.
Research is ongoing for using wet air oxidation on pulp mill wastes and effluents,including at least
one mill that has investigated its impact on haft mill bleaching effluent(Cooper et al. 1996). As the
r�
National Council for Air and Stream Improvement

Technical Bulletin No. 919 85
t
largest units currently in operation can handle only a few liters per minute,this technology is still
several years away from full-scale availability for bleaching effluent.
9.3.3 Risks
The fundamental reliability issue is the scaling problems experienced on heating surfaces.Also,
plugging caused by inorganic precipitation in the reactor has created problems. Chlorides in the
effluent will set requirements on the materials needed to avoid corrosion.
10.0 COLOR REMOVAL—EVAPORATION AND INCINERATION
10.1 Evaporation and Incineration of Bleach Plant Effluent
The bleach plant effluents contain the major part of a kraft mill's color,COD,dissolved organic
material, and total dissolved solids discharge.The bleach plant effluent typically also contains metals
such as manganese,iron, calcium,aluminum, silica,phosphorus,nitrogen,and other trace elements.
Several groups have developed separate evaporation and incineration of ECF bleach plant effluent.
Separate evaporation of TCF effluent is also being developed,with incineration of the concentrate
either in the recovery boiler or in a separate incinerator. Condensates from the evaporation process.
are high in methanol and need to be treated to be suitable for reuse or to avoid air emissions.Figure
10.1 shows how bleach plant effluent evaporation might be integrated into the process.
Figure 10.1 Pre-Evaporation of Bleach Plant Effluent(Algehed, Stromberg,and Bermsson 2000)
t
Make-up water
Wood s Cooking`) tOa= ` ' bleach 'firOrying s Pulp
t� �>.,:•--'2� .s:�� ern..vQ�ent.ib�7".. �' " '.: �{
Nl" elatltun eieu ptafd
fpuu 6qt oMUenl
R 'cavery ;,s Biack liquor. b
'
+area 'evaporatlonTg. n.
#-s ...,�.;K .:.:$ ''§.. evaporation
Day
:Condensal'
y
dean[ond,)Wte a;4%C180n{tle„ Contlensata
tw#
',Recipient,±i
oean aridansatn -'`w.�r� !s'.
Rest prod M
i
National Council for Air and Stream Improvement

86 Technical Bulletin No. 919
Two sample bleach sequences (ECF:DEopDD and TCF: O-Q-Paa-PO-P) are briefly evaluated below:
10.1.1 Process Description
The process would involve bleach plant effluent minimization through filtrate recycle, collection of
the effluent to be treated,pH adjustment of the effluent,pre-evaporation,concentration, incineration,
condensate treatment,and incinerator residue handling for disposal or for recovery of chemicals to the
bleach plant. After treatment,the evaporator condensate could be used as wash water in the bleached
fiber line.
The scope would typically include the following main equipment:
• bleach plant piping modifications to allow increased water recycle;
• ' effluent storage tank;
• pre-evaporation plant and concentrating unit(>40%ds);
• cooling tower for cooling water recirculation;
• incinerator;
• condensate handling; and
• incineration residue handling,possibly with chemicals regeneration.
10.1.2 Evaporation of ECF Bleach Plant Effluent
The following concepts have been studied:
• Evaporation of the whole bleach plant effluent(Blackwell et al. 1991)
• Evaporation of the EOP filtrate only(Dahl and Niinimaki 2000).Pilot trials at the Stara
Gruvbn mill have been performed with actual ECF bleach filtrate.
• Taking the EOP filtrate to the brown stock washing, and taking only the DO filtrate to
evaporation(Dahl et al. 1997).This concept would introduce chloride into the current
recovery cycle along with some of the dissolved material in the EOP filtrate.
Pre-evaporation for the bleach plant effluent
A few suppliers have developed evaporation plants for chloride-containing effluent, including Andritz
(trademark Zedivap)and Hadwaco(Finnish company owned by Hackman,Finland,now USFilter)
(Fagemas,McKeough, and Kyll6nen 1999;Koistinen 1996). Both of these companies use
evaporation principles used in desalination plants.
The Hadwaco plant applies MVR(mechanical vapor recompression) and FF(falling film)principles
(Koistinen 1996).To withstand corrosion in a chloride-containing environment,the heating surface is
made of high density polyethylene(HDPE).The low heat transfer of HDPE is increased by making
the surface very thin(0.02-0.04 ram).This very thin plastic surface results in low AT(2.5°C)and low
pressure drop. At low dry solids concentrations,the energy demand becomes low(8-10 kWh/t
water). The vapor recompression can then be accomplished by a blower type compressor. Up to 8%
dry solids concentration can then be achieved. The use of plastic material limits the upper operating
temperature to about 55°C,so a warmer effluent would flash off the excess heat.The system is
available in modules with capacity about 3.5 Us,each covering 33.2 mz ground area.
National Council for Air and Stream Improvement

Technical Bulletin No. 919 87
J The Zedivap plant operates along the same principles (FF)but the heating surface is a metallic surface
coated with thin plastic on both sides. The temperature limit of the operation is 80-85°C. The
wastewater stream itself or another hot waste stream(>60-65°C)may be used as energy sources.
Depending on the situation,up to 10-12 evaporation stages may be feasible. It can also operate as a
VRC unit, (8-10 kWhh water),in which case the specific loading may be higher and the unit smaller.
Depending on the effluent properties,the effluent may have to be sweetened to 4%dry solids.In this
case it would be evaporated to 10-15%dry solids.The heating elements can be stacked,reducing the
surface demand.
Concentration of the effluent
Before the pre-evaporated filtrate can be incinerated, it has to be further concentrated to 40-50%
solids.This can be done in a similar plant as the pre-evaporation,but needs a higher AT due to higher
boiling point rise,and thus more energy (20-30 kWh t water).A conventional evaporation plant with
the adequate metallurgy (titanium for ECF mill) could also be used.
Incineration
The incineration of the chloride-containing concentrate represents a risk for generating dioxins and
other hazardous air pollutants. Combustion tests have been performed at pilot scale using the
CONOX oxidation unit developed in Finland by the Combustion Chemistry Research Group working
in cooperation with Abo Akademi(Koistinen 1996).A mean residence time of 2 seconds at about
1000°C was considered necessary for complete oxidation of all organic matter.
The ultimate handling of the incineration residue is still not satisfactorily solved.In an ECF mill,the
incineration product will largely be NaCl,and Na2CO3,together with the metals,phosphorus,etc.
present in the bleach plant effluent.It could be possible to clean the residue and recover the sodium
and chloride from it by an electrolytic process.
The incinerator would need adequate flue gas cleaning, e.g., a scrubber and ESP.
Instead of incinerating the evaporation residue on site,it could be potentially sold as such to an
outside chemicals manufacturer,who would process it back into chemicals(NaC1O3 and NaOH).
Condensate treatment
The volatile compounds in the effluent will boil over in the evaporation,including methanol and
volatile chlorinated organic compounds such as chloroform,if present.At higher dry solids
concentrations,hydrochloric acid has also been found to boil over in evaporation tests.
Figure 10.2 shows the carryover in the condensates from the evaporation of acidic bleach plant
effluents as measured in laboratory tests.At high solids concentrations the condensate became more
colored and had a higher concentration of chloride.
Prior to reuse,the condensate has to be cleaned by steam stripping and possibly other methods.The
stripper off-gases have to be disposed of at least thermally,but also with a scrubber to remove the
chlorine compounds.
No full-scale installations of ECF bleach plant evaporation and incineration are in use at this point.
The pilot unit that was operating at Gruv6n, Sweden is not in use any longer.
National Council for Air and Stream Improvement

88 Technical Bulletin No. 919
700 300
ra
600 --- 250 a,
—
O 3 500 —'-- . - -`�-- - u c
� c p
p 400 E mI--�_.�_a.
O u 300 150 -_.�_.___ _.�..... �_
1004
__
4 so
U 0 I n —
0
1 2 3 4 5 1 2 3 4 5
Total solids of concentrate,% Total solids of concentrate,
COD.nOA— TOC.mOA�Cobu,m2Al ry—Folnc a<N,ngA—b—Aboaml,ngA— —Acete acid,Irc�A�
120 3
too
so V % 100
2.8
60
a a —'I--
o v c 27,. i 60 ._�.
D V. s 40 _�t._ —r--._.1.� z `o 40 I i
O 20 2.6 a ro+ I I
D
1 2 3 4 5 1 2 3 4 5
Total solids of concentrate.I. Total solids of concentrate,%
�— Ohbrtle.m67 --+—Conduetrvty.mS/m ...�....pMl — —.f�—r—G K
Figure 10.2 Evaporation of Acid Bleach Filtrates, Carryover in Condensates
(Dahl,Niinimaki,and Kuopanportti 1998)
10.1.3 Evaporation ofTCFBleachingEffuent
Evaporation and incineration of effluent from a TCF plant would need the same basic processes as the
ECF bleach filtrate evaporation. Since no chloride is present,conventional material can be used,
relying on less unproven technology.
The incineration residue would not contain chloride but Na2SO4(if H2SO4 is used in the QA stage for
pulp acidification)and Na2CO3 or Na2S and Na2CO3 if incinerated in a reductive boiler.
A full-scale evaporation unit is in operation in a Swedish TCF line in a linerboard mill in which the
concentrate is mixed with black liquor from the unbleached process and burned in the recovery boiler
(Pekkanen and Kiiskila 1996;Valttila et al. 1995).
10.1.4 Summary of Bleach Plant Effluent Evaporation
Table 10.1 lists the pilot-and full-scale applications of bleaching effluent evaporation.
r
LJ
National Council for Air and Stream Improvement

Technical Bulletin No. 919 89
Table 10.1 Bleaching Effluent Evaporation Installations
Location Bleach sequence Filtrate evaporated Scale Equipment
Stora,Gruvon, O-DEop-D-Ep-D 50150 mix of acid and 300 t/d Hadwaco—pilot
Sweden alk.effluent studies only
Assi Doman, 00-Q-Paa-Po-P Q stage 1400 t/d Zedivap—full
Fr6vifors,Sweden scale,in operation
In the only mill-scale installation,only part of the total kraft pulp is bleached. Obviously,the
accumulation of NPE and other potential problems related to the closure of the bleach plant water
system would be diminished when only less than 50% of the total kraft production employs closed
cycle technology.
10.1.5 Risks
ECF Effluents
• Materials failure risk.
• Chlorinated compounds in condensates and flue gas.
• Incineration residue that is contaminated with chloride may be more difficult to dispose of or
use for recovery of chemicals.
• Build-up of chloride levels in bleacher/dryer if the bleach plant evaporator condensates are
reused on the pulp dryer(related to possible HCl carryover in the condensates).
• If the concentrate is incinerated in the recovery boiler, the accumulation of chlorides and
other NPEs poses a high risk for the mill operation.
TCF Effluents
• Incinerator residue handling in the case of separate incineration(chemicals recovery,
destruction).Mixing with other black liquor prior to incineration is the preferred method for
handling the concentrate.
• Non-process element build-up in recovery if the evaporator concentrate is burned with the
black liquor.
10.1.6 Environmental Impact
The system would eliminate the bleach plant effluent discharges to the sewer, and potentially make a
closed cycle around the bleach plant.However,the real possibilities of achieving this have to be
examined further as technology and experience develop.
The evaporation plant condensate will contain volatile compounds present in the bleach filtrates
(methanol etc.),and also chlorides, depending on the pH.Tests have also indicated that color bodies
may be carried over into the condensates (Dahl,Niinimaki,and Kuopanportti 1998;Dahl and
Niinimaki 2000).The condensates have to be cleaned before they can be reused.
National Council for Air and Stream Improvement

90 Technical Bulletin No. 919
10.1.7 Impact on Chemicals
In order to minimize carryover in the condensate, the pH of the feed to the evaporator should be
slightly alkaline.Acid waters(such as if Do effluent is treated alone)have to be adjusted to alkaline
pH.
There could be a potential to recover bleach plant chemicals from the incinerator wastes if that
technology would develop.
10.1.8 Water Requirements
The need for cooling water in the evaporation plant will depend on the system configuration.In
principle, all energy that is fed to the evaporator,including the energy in ingoing water less energy in
outgoing condensate and liquor,has to be removed from the system with cooling water. If heat is the
energy source,the cooling demand is significant but lower in a MVR or VRC unit.
11.0 COLOR REMOVAL—FUNGUS/BACTERIA/ENZYMES
11.1 White-Rot Fungus Treatment
Various strains of white-rot fungus have been known to be able to degrade lignin as a"secondary
metabolism,"meaning lignin would be metabolized if a certain growth factor becomes limited. This
ability is not lost when the lignin becomes chlorinated in pulp bleaching, so the fungus is of interest
in removing chlorolignins and chlorinated phenolics in bleach plant effluents as a means of reducing
effluent color and toxicity.
Several parallel research programs have been pursued and the one most advanced at this point is the
"MyCoR"process at North Carolina State University.In this process the fungus is immobilized on a
series of flat disks,which are mounted in parallel on a rotating horizontal shaft such that portions of
each disk are alternately submerged in the waste operation.Either 1-or 2-day retention time would
probably be required(Pellinen,Joyce, and Chang 1988).
Since the fungus cannot use lignin as an energy source,it must be supplied one. If the stream to be
treated does not contain enough energy sources,such as hemicellulose,suggested possible additives
are glucose,xylose,cellulose,or possibly primary sludge. In addition,the pH should be between 3
and 5,the temperature between 28-40°C, and nitrogen should be the limiting nutrient.
Recent work conducted by researchers in Mexico used a two-stage process in the laboratory to
simulate the treatment of weak black liquor spills(water with weak black liquor)(Caffarel-Mendez et
al. 2004). In this experiment no additional carbon source was used.The treatment process consisted
of an anaerobic first stage,which was a methanogenic fluidized bed reactor,and an aerobic second
stage,which was an upflow reactor packed with wood cubes containing immobilized Trametes
versicolor white-rot fungi. Hydraulic retention times(HRTs) for stage 1 were varied between 0.5 and
5 days and the hydraulic retention times for stage 2 were 2.5 and 5 days.The fungal reactor was able
to sustain removal activity for 95 days without carbon addition.The overall process had a COD
removal efficiency of 78% and a color and ligninoid removal efficiency of 75%. The aerobic fungal
treatment(stage 2)removed color and ligninoids more efficiently than the anaerobic stage (stage 1),
while the anaerobic stage was better at COD removal.
Other white-rot fungal treatments include the MyCoPor(Messner et al. 1990)and immobilized fungal
fluidized bed bioreactor.
National Council for Air and Stream Improvement

Technical Bulletin No. 919 91
The MyCoPor process is a trickling filter that immobilizes the fungus on the surface of polyurethane
foam cubes.Both the MyCoR and MyCoPor use passive immobilization,i.e., adhesion of cells to a
solid support.
The immobilized fungal fluidized bed bioreactor uses entrapment of the fungus in urethane foam
(Pallerla and Chambers 1996).This active immobilization results in a media with a high resistance to
deterioration by mechanical action and pH.This reactor is effective at removing color and AOX, with
removal efficiencies of 70%and 50%,respectively.Figure 11.1 shows the color reduction during the
experiment using a continuous fluidized bed bioreactor.The reactor was fed a mixture of 60%D-
stage effluent and 40%E-stage effluent obtained from a mill with a OD(EO)DED bleaching
sequence.The reactor functions best at a pH of 5, and due to the porous nature of the urethane foam,
transport processes are non-diffusion limited. As with other white-rot fungus treatments, an energy
source for the cells must be supplied. In this case glucose at 8 g1I would be recommended along with
nitrogen and phosphorus. Currently this technology is in the pilot-scale phase.
z 86'
O
> >2 i
W
W 581
0
J
u 44
30�-
0 5 10 15� 20 25 30 35
TIME,days
Figure 11.1 Color Removal in an Immobilized Fungal Bioreactor(Pallerla and Chambers 1996)
11.1.1 Technical Feasibility
This process has only been tested at small scale,with the largest existing unit treating about 75 1/d.
Technology to take advantage of the decolorizing ability of the white-rot fungus has not developed to
the point where it can be utilized industrially.
11.1.2 Environmental Impact
Rough removal efficiencies for one-day retention time are listed below.
• Color 50-80%
• Chlorinated phenolics — 100%
�J • AOX 45-70%
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92 Technical Bulletin No. 919
• BOD 30%
• COD 14-30%.
Tests for acute toxicity of effluent treated with this process have been done on daphnia and Microtox;
complete removal of toxicity was demonstrated. Dioxin has also reportedly been reduced by white-rot
fungi.
Laboratory experiments have also been conducted by researchers in Turkey on the use of algae to
treat wastewater from kraft mills(Dilek,Tarlan, and Yetis 2002). The experiments were conducted on
wastewater from a mill pulping red pine and using a CEHDED bleaching sequence. The tests were
conducted in jars maintained at a constant temperature and the wastewater was treated with a nutrient
medium and a light source to stimulate algae growth.After a treatment time of 42 days the COD had
been reduced by about 55%,the color by about 80%,and the AOX by about 65%.Figure 11.2 shows
the reduction of pollutants during the experiment. The long treatment time,the temperature
requirement, and the light requirement make this technology impractical for a mill operating in a
northern climate.
1.01 50
0.8 40
ZK
X 0.4 30
d
G5 � OA � � 20
0
Ov 0.2 10
0.0 0
0 10 20 30 40 50
Tore,d
Fig. 1. Algal growth and COD. AOX and color removals under 3.4
klx light intensity and 230 mgfl initial COD((M): COD; (a):color,(�)
AOX; (x) algal biomass).
Figure 11.2 Color Removal by Algae Treatment(Dilek,Tarlan,and Yetis2002)
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Technical Bulletin No. 919 98
12.0 TASK II: MILL-SPECIFIC REVIEW OF TECHNOLOGIES AND PERFORMANCE
This study was supported by a group of bleached kraft mills.It included a review of successful and
unsuccessful color technologies applied or tried at those mills. It also included a benchmarking of the
color discharges from the mills.
12.1 Color in Study Mills
Table 12.1 summarizes the color data for the four papergrade mills.
Table 12.1 Summary of Color Balance Data in Four Papergrade Bleached Kraft Mills, Ib/ADT
Mill A Mill B Mill C Mill D
Bleaching 12.6 42.9 42.4 25.2
CRP Waste 3.5
Brown Side Color 11.4 9.2 7.2 8.9
Paper Machines 1.1
Total Measured 28.6 52.1 49.6 34.1
Unknown/amplificatio
n 4.7 28 ? ?
Total Influent 33.3 80.1 51.2
Final effluent 28.3 66.3 20.1 23.5
f In these grills the identified"brown color"amounted to 7-10 lb/ADT.
When using best available technology(BAT)the"brown color"target(excluding washing loss)could
be
• From spills: 2 kg COD/t or about 4-5 lb color/ADT(22)
• From condensates: 21b/ADT(EKONO's estimate)
• From rejects and knots: 0-2 Ib/ADT(EKONO's estimate)
• Total 6-91b/ADT
A more detailed summary of the color data for four mills participating in the study is shown in Tables
12.2 through 12.5.
Table 12.2 shows the data for Mill A based on 2005 average data.The in-mill color sources are
extensively monitored, so that only about 14%of the color in the combined influent has not been
identified. The mill largely attributes the unknown color to amplification of the color in the sewer
system.The color is reduced in the activated sludge plant by an average of about 15%. The mill
attributes the reduction mainly to reduction of black liquor originating color rather than bleach plant
color.The mill estimates the black liquor color to be reduced by 50% due to sorption of colored
lignin on the bacterial sludge.
National Council for Air and Stream Improvement

94 Technical Bulletin No. 919
Table 12.2 Summary of Mill A Color Data(ADT=Air Dry Short Tons of Bleached Pulp)-
2005 Data
Unit SWD HWD Total Total coloq
lb/d
Bleached Kraft Sham %of total mill output —79
Hardwood %of total bleached 58
kraft onto
Digester Kappa —35
Pm-Bleach Kappa 16-17last) 10 lest)
Bleach Sequence ODEoD ODEoD
Kappa Factor (No 1 Stage) 0.255 0.229
Bleach Plant Effluent
Acid Sewer
Flow m3/ADT(GPM) 2.4(257) 7.0(1028)
Color Ib/ADT(PCU) 8.3(1566) 5.7(367) 9371
Alkaline Sewer
Flow m3/ADT(GPM) 1.2(125) 2.5(361)
Color Ib/ADT(PM 7.5(2940) 4.6(853) 8117
Total Bleach Plant Effluent Color Ib/ADT 15.8 10.3 12.6 17489
Non-Bleach Color Sources
Brown Stock Ib/ADT 4.4 6100
Digester Area Ib/ADT 0.8 1149
Condensates lb/ADT 2.0 1821
Evaporation Plant Ib/ADT 0.6 818
Recovery Boiler Ib/ADT 7.1 9789
Paper Mill&Other Ib/ADT 1.1 1426
Total Non Bleach Sources Ib/ADT 16.0 22103
t Total known Sources Ib/ADT 28.6 39591
(Unmeasured Color/Amplification Ib/ADT 4.7(-14%) 6522
Measured Primary Influent Color Ib/ADT(PCU) 33.3(215) 46113
Final Effluent
Flow n3/ADT(MOD) 70.1(25.6)
Color Ib/ADT(PCU) 28.3(183)
Color Limit(Annual Average) Ib/d 42000 39128
Color Limit—Normalized, Ib/ADT-2005 prod'n 30.5
Approximate
'5000 lb/d(3 lb/ADT)is due to CRP,i.e.,the bleach plant filtrate recovery process.
Table 12.3 shows the color sources for mill B,based on 2005 data. In this mill the difference between
known in-mill sources and combined influent is 35%,likely due both to unmeasured color and to
possible color amplification in the sewer system.
The color is reduced in the effluent treatment plant by 17%, of which 2% in the primary clarifier and
15%in the activated sludge plant.
National Council for Air and Stream Improvement

Technical Bulletin No. 919 95
Table 12.3 Summary of Mill B Color Data(ADT=Air Dry Short Tons of Bleached Pulp)-
2005 Data
Unit SWD HWD Total Total color
lbld
Bleached Kraft Share %of total mill 80
Hardwood %of total bleached 78.5
kraft nulu
Digester Kappa 28 17.4
Pre Bleach Kappa
Bleach Sequence DEopPD DEopD
Kappa Factor (No 1 Stage) 0.26 0.22
Kappa Factor (whole BP) 0.44 0.37
Bleach Plant Effluent
Acid Sewer
Flow m3/ADT(GPM) 30(1260) 21(3310)
Color lb/ADT(PCU) 29(445) 27(570) 29414
.Alkaline Sewer
Flow m3/ADT(GPM) 10.6(450) 4.5(700)
Color Ib/ADT(PCU) 33.1(1410) 10.6(1055) 16501
Total Bleach Plant Effluent Color lb/ADT 62.5 37.6 42.9
Non-Bleach Color Sources Ib/ADT
Digester Area Ib/ADT N/A
Brown Stock Ib/ADT 6.1 6500
Contaminated Condensate Ib/ADT N/A
Evaporation Plant Ib/ADT N/A
Recovery Ib/ADT 3.1 3269
Paper Mill&Other Ib/ADT N/A
Total Measured Non-Bleach Color lb/ADT
Total Known Color Sources lb/ADT 52.1 55684
Unmeasured Color/Amplification b/ADT 28(35%)
Combined Influent Color(Measured) lb/ADT(PCU) 80.1(480) 85725
Secondary Influent Color Ib/ADT(PCU) 78.5(462) 84065
Final Effluent
Flow m3/ADT(MOD) 77(21.8)
Color Ib/ADT(PCU) 66.3(390) 70965
Color Limit(max,downstream in 75(monthly)
river) 225(daily)
Table 12.4 shows the color sources for mill C.The bleach plant color is monitored regularly,but
other sources are not.Data from a color survey in year 2000 was used to break down the black liquor-
originated color; therefore, the current level of black liquor originated color and the so called color
amplification cannot be assessed.The data indicate that the bleach plant effluent contributes over
80%of the combined influent color as an average.
Mill C takes a high color reduction in the effluent treatment system. The biological treatment by itself
reduces the color by some 40-50%.The mill also has to add chemicals(alum based) to meet the
current color limit. The total color reduction in the effluent treatment system is 55-65%when
chemicals are added.
t
National Council for Air and Stream Improvement

96 Technical Bulletin No. 919
Table 12.4 Summary of Mill C Data(ADT=Air Dry Short Tons of Bleached Pulp)
Unit SWD HWD Total Totalcolor
lbld
Bleached Kraft Share %of total mill _80
output
Hardwood °%of total bleached 55
kaft pulp
Digester Kappa —25 —20
Pre-Bleach Kappa 16-17 lost) 10-11
Bleach Sequence ODEopD ODEopD
Kappa Factor (No 1 Stage) 0.27 0.25
Kappa Factor (Total) 0.5 0.5
Bleach Plant Effluent
Acid Sewer
Flow m3/ADT(spin) 24.4(1443) 21.3(1560)
Color Ib/ADT 22.9(425) 16.4(350) 13933
Alkaline Sewer
Flow m3/ADT(gpm) 14.7(871) 3.6(265)
Color Ib/ADT(PCU) 32.5(1000) 8(1000) 13653
Total Bleach Plant Effluent Color Ib/ADT 55.4 24.4 38.2 27586
Other Measured Color Sources(2000 data) Ib/ADT
Other Measured Color Sources,Total Ib/ADT 6.5 4709
Total Known Color Sources lb/ADT 44.9 32295
Other b/ADT(%) 1.2 1006
Combined Influent Color(Measured) Ib/ADT 46.1 33301
Secondary Influent Color Ib/ADT 43.3 31300
Final Effluent
Flow m3/ADT(MOD) 65.5(12.5)
Color_summee lb/ADT(PCU) 16.9(133) 13873
Color_winte? Ib/ADT(PCU) 19.2(117) 12206
Color Limit in final effluent ppm,monthly avg 140(so)
123(wi)
Color Limit in Final Effluent-Normalized lb/ADT 2005 prod 22(so)
(Approximate) 19,8(wi)
'So=summer
n Wi=winter
Table 12.5 details the color balance for Mill D. In this mill, all black liquor-containing color sources
are continuously monitored in a sewer separate from the bleaching paper making.However,the
combined influent is not monitored separately,only by adding the separate influent streams.The
black liquor-sourced color is 8.9 lb/ADT.
This mill also measures a color reduction in the effluent treatment system of about 30%.The mill
attributes this to the use of lime used for neutralization of the influent.
National Council for Air and Stream Improvement

Technical Bulletin No. 919 97
\% Table 12.5 Summary of Mill D Data(ADT=Air Dry Short Tons of Bleached Pulp)
Unit HWD SWD HWD Total Total
1b/d
Bleached Kraft Share %of total mill -95
output
Hardwood %of total _82
bleached kaft
Digester Kappa IS 36 16.9
Pre-Bleach Kappa 11.8 22.6 16.9
Bleach Sequence ODED ODEDD DEDD
Kappa Factor (No r Stage)
Kappa Factor (Total)
Bleach Plant Effluent
Bleach Plant Effluent-Special Test
2006
Acid Sewer
Flow m3/ADT(gpm) 3.8(665) 39.2(2750) 32(4400)
Color Ib/ADT 3.9(460) 23.4(273) 37(510)
Alkaline Sewer
Flow m3/ADT(gpm) 5.3(930) 11.1(1060) 1(105)
Color Ib/ADT(PCU) 5.7(487) 37.5(1052) 3.1(1740)
Total Ib/ADT(PCU) 9.6(491) 61.9 40.1
Total Bleach Plant Effluent Color- Ib/ADT(PCU) 10.0(491) 38.1(516) 25.2 -59801
2005 Average
Total Non-Bleach Color Ib/ADT
Flow m'/ADT(MGD) 8.3(4.72)
Color Ib/d 21112
- - Color lb/ADT(PCU) 8.9(536)
Combined Influent Color B Addition, Ib/ADT
( Y 38.9 80912
Not Measured)
Final Effluent
Flow m'/ADT 53.4(30.3) 55891
Color Ib/ADT 23.5(221)
Color Limit in Final Effluent ppm,monthly 800
Color Limit in Final Effluent Ib/ADT 2005 85.2 202,000
(Normalized,Approximate) prod'n
12.2 Benchmarking
Figure 12.1 summarizes the color from the mills in bar charts as sources to the influent and as final
effluent. The data has been normalized based on the total pulp produced on each site in air dry short
tons (ADT).
The data in Figure 12.1 are for the average production at the mills. Figures 12.2 and 12.3 show the
color sources separately for softwood and hardwood, assuming that the black liquor-originated color
is the same for both wood species and the bleach plant effluent color differs as reported by the mills
and detailed in Tables 12.1 through 12.4.Mill F and Mill G in these charts are mills outside the
survey,based on literature and EKONO file data.
The data in Figures 12.2 and 12.3 indicate that,depending on the specific mill conditions,hardwood
production would generate 30-45%less color than softwood.
Figure 12.4 is an attempt to separately benchmark the bleach plant effluent color in comparison with
literature data.All bleach lines in this study are included as well as other data from EICONO files.As
National Council for Air and Stream Improvement

98 Technical Bulletin No. 919
shown,there is a wide spread among the data,depending on measurements and specific mill
conditions.
Figure 12.5 shows a benchmarking of the final effluent color of 30 bleached kraftmills in North
America and South America in EKONO's database. The mills include both market pulp mills and
integrated wood free mills.In this case the effluent color was normalized based on the total mill
output of paper(and market pulp, if any).Three of the study mills are among the lowest six
dischargers of color. When known,the share of hardwood pulp is indicated on the charts.The highest
discharges of effluent color occur among the softwood market pulp mills.
Color Sources and Effluent Color
90
80 ___ _ -------------®Unknown/Amplification
EI Identified BL color
70 -------------------- -------------❑Paper Mill
■CRP Waste
60 -------------O BP
O
❑Final Effluent
a
0 40 ---------------—--- -------- --------------------
0
10 --- -------- -------- -- -- -
0 -
58% HWD 78 %HWD 55 % HWD 83 % HWD
Mill A Mill B Mill C I Mill D
Figure 12.1 Color Sources and Effluent Color in Four Study Mills
National Council for Air and Stream Improvement

Technical Bulletin No. 919 99
Color Sources of Influent Color, Hardwood
120
0 Unknown/Amplification
❑Identified BL color
100 ----------------------------—----- ❑Paper Mill
m CRP
El BP
80 —-------------------------------------—--------------—--
I-
Q '
a60— --------------- ---------------------------------------
`o
0
U
40 _______________ _____-_____________-____,______
i
0
Mill A Mill B Mill C Mill D/02 Mill D/No 02
Figure 12.2 Approximate Sources of Color from Hardwood Pulp Production
Color Sources of Influent Color, Softwood
120
0 Unknown/Amplification
D Identified BL color
100 -- ------------------- O Paper Mill
■CRP
17 BP
80 ------------ -------------- -----
F 4
Q
n 60
0
0
U w
40 ----------`- --- ----- - - ---- -
20 -- . .i —`— ----- ----- --- ---- --
A IL
0
Mill A Mill B Mill C Mill D Mill F Mill G
! Figure 12.3 Approximate Sources of Color from Softwood Pulp Production
National Council for Air and Stream Improvement

100 Technical Bulletin No. 919
ECF Bleach Plant Effluent Color as a Function of
Unbleached Kappa number (Paper Grade Pulp)
100
O Mill A1021BFR
O
90 *Mill aoz ----- --- -----'---------------------'----------
80 ♦MillD102 O_HWD
-- --------------------
•Mill 13/02 -
70 ♦Mill DINo 02 _________y______-___,__________,____
O Mill C/02 ' ^
O 60 0Mill C102 -____�_________�_____-___-___�_____,_____a
Q
2 0 Mill B
50 ---- ,
C ,
O Mill H102 _
O •Mill H1No 02
i ,
30 - -------------------
PO
0
0 5 10 15 20 25 30
Kappa
}} Figure 12.4 Bleach Plant Effluent Color at Varying Kappa
Lf
Benchmarking of Final Effluent Color
180
160 ----�
140 ------- ------------------------------------
a ' I
i
100 --------------------------------------------- i
F- 80 fI
60 -------------------------
L 40 -- -
O i � If
O 20 --- i I -
- - E - - -
0 . IRI
x x x x x x x x x x x
U C Q m m o 0 0 o 0 0 0 O
Figure 12.5 Benchmarking of Final Effluent Color
National Council for Air and Stream Improvement

Technical Bulletin No. 919 101
12.3 Color Technologies in the Study Mills
A questionnaire was sent out to the participating mills to collect data on successful and unsuccessful
color technologies that have been implemented or tried in the mills. The technologies were discussed
in follow-up interviews with the mills.
12.3.1 In Process Technologies
Successful in-mill color technologies that were listed and commented on by the participating study
mills include the following:
• Maximize hardwood(possibly,but market-driven)
• Kappa to bleach plant(reduced by installing oxygen delignification,raised in digester for cost
savings, including yield).
• Oxygen delignification(high cost)
• "Mini 02"(Modeled in one mill—pending decision)
• New washer line
• Addition to existing washer line; lay-on roll additions, added stages,replace shower bars
• DF control on last washer before bleach plant; study of filtrate balance and washer
performance during good color period to set targets
• Vibratory knotters replacement,pressure knotters installation
• Knot filtrate recovered:
• In-process,post-discharge knotter drainage recovery being installed
• Knotter bins: small source of color,therefore not much reduction
• New screening equipment-closed screening(35%reduction in color)
• ECF conversion
J • Kappa factor change
Study recommendations and process optimization
• Eop—peroxide reinforced extraction(no benefit if the Eop filtrate is recovered)
• Effluent-free reject handling
• Reject press project: Mechanical reliability and operational issues persist, SE color
reduction<500 lbs/day
• Reject press-successful
• Larger flash tanks,drop separators
• Evaporator boil-out procedures—effluent-free
• Capture wash water in spill collection
• Equipment drainage before and during S/D—collected or sewered
• BMP program; collect and return process colored materials
• Pump seal and leak daily rounds
• BMP inspection program,mechanical seal project underway
• Overflow alarms
• Conductivity probes in sewers
• Daily/hourly color balance/alarm
• In operation
• Operator education
• Conductivity cut-off limit
• Conductivity set points vary by process area
• Spills collection
• capture and recover color events when possible,or batch treat with chemicals
• Eop filtrate recycle to brown stock washing w/o pretreatment—requires chloride removal
National Council for Air and Stream Improvement

102 Technical Bulletin No. 919
• bleach filtrate recycle process
• (BFR; ion exchange+chloride removal)
• Chloride buildup and washer scaling are ongoing operational problems
• Mechanical reliability of minerals removal process also an issue.
• Mechanical seals
• On pumps in black liquor areas to avoid clear water dilution of color materials
Unsuccessful in-mill color technologies include:
• 02-two stages
• Pulp strength deterioration, insignificant savings at BFR closure rates>80%
• COZ use for acidification of e.g.,washwater
• Excessive foaming
• Closing screen room existing line
• in specialty mill-product quality constraints
• Ozone bleaching
• Studied in detail,color increased, freeness decreased, and high operating cost
• Peroxide treatment of effluent streams
• Hwd Eo filtrate—no benefit with Eo filtrate recycle in place
• CRP-Severe foaming;high operating costs;no benefit to secondary effluent color,
increased cost of production
12.3.2. External Color Technologies
Table 12.6 summarizes the external color technologies that were judged as successful from a color
reduction point of view.Many of the technologies are,however,not justifiable from economic
feasibility or technically related issues,such as sludge handling,etc. The most promising external
technologies could be:
• Polymer treatment for brown color(applied in two mills). With appropriate sewer segregation
the resultant sludge could be combined with black liquor,burnt in the recovery boiler and
yield savings in make-up chemicals.
• Aluminum-based treatment in the activated sludge treatment(AST)plant(applied in one
mill).Possibly AST combined with activated carbon and sludge burning in the recovery
boiler.
The reported color reduction in the biological treatment(without chemical aid) in the mills using
activated sludge process varied between 15-40 (50%).An improved understanding of the color
reduction in the activated sludge process could provide an opportunity to reduce color for some mills.
Only one of the study mills has an aerated stabilization basin.That mill, like many other mills with
the ASB process, experiences a color reversion,i.e., an increase of the color in the effluent treatment
system.
Table 12.7 summarizes the technologies that were unsuccessful from a color removal point of view or
that were technologically not reliable.
National Council for Air and Stream Improvement

Table 12.6 Successful External Technologies
Treated Stream ; y n
1 Applicability a2.
nasis s
d ------- ---'
21
U l •P o f y 03
`° t I 11 :9 I ,o a
w z
U ❑ O
{ [ I j High cost. - CO
Y I ? Y I i 2 ro
g
0 Activated Carbon I Y High cost.
Y Y =Y
Too costly due to too much AC required
0 3 1 : 2 5 2 and stud a disposal issues.
' Y Y Y 1 1 I If lime is reused in the process,could
O Lime Treatment _._ have a product Quality impact.
30% Y — . —
O Yes iv
D Polymer precipitation In-mill sewer containing black I 100 T I Y - 1 5 • ? 5 5 Successfully reduces 100 tons of
Ii um' {__ t ` t s _ ! color/day in black liquor trmt.
O_ Al-based chem.add Y Y i �� 3 j�� 4 secondary effluent with recycled sludge.
___-.—
cT Peroxide treatment Y I I ! 1 f 4 2 ! 5 t 2 ' For HWD Eo filtrate—not applicable if
I .._. ..._._.._..! .._ ____ Eo filtrate is recovered. _
9 Treatment of Hwd Eo,successful pilot.
y 3 4 l 0 4 Cost of TAML catalyst very high and is
cost-prohibitive;may revisit if TAML
Enhanced peroxide treatment of E- _ i_ - _, '• cost comes down.
Nstage effluent(TAML catalyst) } Y ( Y e -- 3' I ! 5 Z ' Not ye[ready for full-scale operation due
3 1 < f �._ __..._. __ _ ____x_?.' _.'__ _ - -� to manufacmnrgissues. _
i - —
CD ! Y I ! j Y ! { 5 I ? 1 ! 4 1 —30%reduction in Ep filtrate.
i I I Not recommended for full-scale
1 operation(cost/sludge issues and
Polyamine ' Y 3 Y ! ' 3 ' 0 3 5 I concerns about effluent toxicity).Works
fine for batch treatment of high color
- I j events captured in spare primary
I a1 clarifier.30 to 65%color reduction.
Scale:0=no reduction.....5=very significant reduction
Scale:0=not technically feasible(technology not ready for full scale)......5=technology ready and in use
`Scaler 0=not monomicallyjustified(high costs)......5=positive payback
Scale:0=negative impact.....5=.no or improving impact on quality
O
W

f
Table 12.7 Unsuccessful Extemal Technologies o
F Treated Stream I !
1 _,__Applicability analysis___
� F
13
3 U v E v ci0ip 2 • co
Ii a 4 �' U i rn i c
9 F W
W
} i �
mLimited and inconsistent color removal;
Microfilmition(MF) Y 1 j t Y 3 1 2 g requires pretreatment chemicals;high
m I capital and operating costs.Pilot equipment
n j i i had control problems.
Membrane fouling and failure high capital
2. Ultrafiltration(UF) Y Y 2 Y 2 1 2 3 and operating costs not reliable for routine
6 ---— ---__---L ­­ ---. _
yReverse osmosis(RO) Y ! ? � 1 2 Expensive
I i i i I i 1 a 1 Massive amounts of lime and lime sludge if
� treating total wastewater influent,high
ET I i capital and operating costs.Lime addition
m ? 1 I C to 5B sewer from recovery had no
B Lime precipitation Y I Y j 2 1 Y j 1 0 f 3 1,2&4 statistically significant effect on SE color.
Massive lime doses during kiln wash will
remove color by co-precipitation in primary
! clarifiers.Not practical or economical for
3 i i i j j everyday treatment of color.
CD — —
T I �
Causes pH problems at W WTP,massive CD
Al-based precipitation Y Y 2 Y 1 0 3 1 &2 amounts of sludge that dewaters poorly.
IT High capital and operating costs. m
— — ----- ._. -- — W
Electrochemical treatment Test stream not defined ' Y 0 rp
(Continued on next page.See notes at end of table.) _- Z
0
rD

Table 12.7 Continued
m
Treated Stream s
t c Applicability analysis„ f_..____.
E E v U ( f y z n o 'a .,o v c m Z
n i a F w 3
a } o U m 7
to � � i j cO
0
m
Peroxide treatment with iron Y 0 Y 1 0 0 q "Poor Man's TAMU Trial on Hwd Eo
� activator was a bust,no color removal.
0
C
i ! Capital intensive:with high operating
o Ozone treatment Y j Y 3 Y i 0 0 ! 3 j 2 ; cost,effluent toxicity w/out ozone
1 destruction step.
m Y i 0 1 Y j 0 i 3 i 3 j q r Fungus would not grow.The study was
a
`` I f E _to White-rot fungus treatment f terminated.
m 2 4 Not sustainable in alagoon
i
m Mostly 1 5
g environment.
Y
v C1O2 added to hdwd Eo filtrate—no
-o CIOi treatment benefit with Eo filtrate recovery
� ' Y f Pilot-scale trial
03 CIOZ treatment of CRP waste Y (control t I on CRP purge Process control issues high chemical
1 (color) foaming) 0 2 j 3 stream i costs,foaming.
Other-UV-Peroxide Y 7 1 0 4
'Scale:0=no reduction.....5=very significant reduction
"Scale:0=not technically feasible(technology not ready for full scale)......5=technology ready and in use
Scale:0=not economically justified(high costs)......5=positive payback
Scale:0-negative impact.....5=no or improving impact on quality
0
rn

106 Technical Bulletin No. 919
13.0 SUMMARY AND CONCLUSIONS
At the request of five U.S.bleached kraft pulp mills,NCASI contracted with EKONO Inc. to
undertake a review of color control technologies and their applicability to modern kraft pulp mill
wastewater. The study was to build on an earlier color reduction study carried out in 1995 (Baird
1995).
The ultimate goal of the current study is to help kraft pulp mills to identify potential opportunities to
reduce effluent color. The specific objectives for each task follow.
Task I: Develop a comprehensive list of different in-mill(both"brown"and bleached)and effluent
treatment color reduction technologies and describe the technologies,their applicability to modem
bleached kraft pulp mills,and their impact on color loads
Task II: Conduct a mill-specific review of the color control measures and benchmark the effluent
color of the participating mills relative to other mills.
The color technologies addressed in this study are summarized in Table 13.1 together with an
assessment of their impact on color and some of the risks associated with them.Many of the
technologies are applied or have been tested in the study mills.
The color of the effluents from the study mills producing papergrade pulp is among the lowest
compared to a database of 30 bleached kraft mills, as shown in Figure 13.1.
Benchmarking of Final Effluent Color
180
160 ----- --------
a.
120 ---------------------------------------------- f
LL100 ----------------------------------------------- f I
80 ---------—---------------------- - - [ i
] . I
C 40 ---- - t
V 20 --
0 Ji IIIIIIt
3 3 3 3 3 3 3 3 3 3 3 3 3 3
x x x x x x x x x x x x x x
Figure 13.1 Effluent Color Benchmarking
National Council for Air and Stream Improvement

Table 13.1 List of Color Reduction Technologies Included in the Evaluation
Technology Scale of Implementation Color reduction Risks —i
Reduce kappa number Full scale Major Product quality m
Improved washing Full scale Major
Improvements in knotter and reject systems Full scale Moderate ci
Closed screen room water cycle Full scale Major
Reduced carryover of black liquor in flash vapors Full scale Moderate to high
Improved evaporator boil-out and wash procedures Full scale Moderate to high
Convert to ECF bleaching Full scale Major CD
Use oxidizing bleach chemicals Full scale
Hexenumnic acid removal—w/o filtrate recovery Full scale No Z
0
Ozone—w/o filtrate recovery Full Scale No(lab data) Product quality
Z Eop w/o filtrate recovery Full scale Moderate Color reversion --�
m Peroxide(PO,P) No data—likely moderate Product quality,color reversion
Cox
0 Perseids w/o filtrate recovery Full scale No data—likely moderate Product quality,color reversion
toSpill prevention Full scale Major
nSpill collection and control Full scale Major
0 Spill system adequate sizing Study Major
7 Operator education Full scale Major
Q. E,filtrate recirculation to brown stock washing 10—15%recycle-Full scale Low Corrosion/RB plugging
0 100%recycle-Study Potentially high Chloride removal process necessary,scaling
Bleach Filtrate Recycle(BFR)process with chloride and numerals removal 75%recycle in full scale Major Corrosion,scaling
D Recycle of chloride free bleach filtrates-alkaline Full Scale Potentially high
Recycle of chloride free bleach filtrates-acid Study Potentially high Scaling,NPE accumulation
Membrane treatment of alkaline bleach filtrate Kraft-installations Sin Potentially high N/A High costs—fouling,developing for krft
0- Sulfite 02 filtrate-Full Scale Fouling
b problems
Ion exchange Kraft installation SID Potentially high High costs,fouling,No data for ECF
CD w Eleclrodialysis Lab No data Cost
3 Activated carbon No full scale yet Moderate to high Cuban cost,sludge,toxicity
Chemical precipitation
-0 Of brown color Full scale Potentially high Chemicals cost,Sludge
0 Of mill effluent Full scale High Chemicals cost,Sludge,Toxicity
N Oxidation processes
3 Peroxide treatment of Eop filtrate Was operating in full scale Moderate Chemicals cost,color reversion
D Peroxide TAML Lab and Pilot Potentially high Chemicals cost,color reversion,TAML supply in
industry scale
Ozone Lab Moderate to high at high dosages Ozone cost,toxicity,ozone
Ozone/Uv Lab No data(probably significant) Ozone cost,toxicity,ozone
Ozone/Photocatalyst Lab No data(probably significant) Ozone cost,toxicity,ozone
Wet air oxidation Lab Significant at long residence times Full scale undeveloped
Evaporation and incineration of bleach plant effluent Full Scale for TCF No data
Studies for ECF Significant Chloride,corrosion,materials,condensate
composition
Fungus/algae/bacteria/enzymes Lab Moderate to high—no effect Sensitive to external factors
on some tests.
0
v

108 Technical Bulletin No. 919
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