NC0000272_NCASIColorMeasurementTechBulletin_20000501

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NATIONAL COUNCIL FOR AIR AND STREAM IMPROVEMENT
AN UPDATE OF PROCEDURES
FOR THE MEASUREMENT OF
COLOR IN PULP MILL
WASTEWATERS
TECHNICAL BULLETIN NO. 803
MAY 2000
by
Diana Cook
National Council for Air and Stream Improvement, Inc.
West Coast Regional Center, Corvallis, OR
Nikki Frum
National Council for Air and Stream Improvement, Inc.
West Coast Regional Center, Corvallis, OR

4
Acknowledgments
This report was prepared by Diana Cook,Senior Research Scientist,and Nikki Frum,Research Associate,at the
NCASI West Coast Regional Center.
For more information about this research,contact:
Diana Cook Reid Miner
Senior Research Scientist Vice President,Water&Pollution Prevention Programs
NCASI West Coast Regional Center NCASI
P.O.Box 458 P.O.Box 13318
Corvallis,OR 97339 Research Triangle Park,NC 27709-3318
[phone] [phone]
[e-mail] [e-mail]
For information about NCASI publications,contact:
NCASI
P.O.Box 13318
Research Triangle Park,NC 27709-3318
[phone]
[e-mail]
National Council for Air and Stream Improvement,Inc.(NCASI). 2000. An update of procedures for the
measurement of color in pulp mill wastewaters. Technical Bulletin No.803. Research Triangle Park,NC:
National Council for Air and Stream Improvement,Inc.
©2000 by the National Council for Air and Stream Improvement,Inc.

n cas i
serving the environmental research needs of the forest products industry since 1943
PRESIDENT'S NOTE
One of NCASI's roles in support of the pulp and paper industry's environmental programs is the
eIaluation and development of analytical methods useful in characterizing the constituents and
properties of process effluents and wastewaters. In 1971,NCASI developed and published a method
for the measurement of color in effluents from pulping operations and their receiving waters. Since
then,the NCASI color method has been widely used in mill effluent monitoring and compliance
assessment programs;it has also been used to evaluate receiving water properties. But in the nearly
three decades since the color method was published,a number of innovations have occurred in pulp
and papermaking techniques. The impact of these innovations on effluent quality has been significant
enough to suggest that the NCASI color procedure be re-evaluated using modem pulping effluents.
' Ws bulletin describes a recent evaluation of the method and provides an updated procedure for color
measurement. The procedural updates were designed to enhance the repeatability and reproducibility
oIf the method while maintaining the existing fundamental basis of historical pulp mill effluent color
measurement.
Aspects of the color measurement procedure that were evaluated included wavelength for lower color
effluents,turbidity removal,pH during and following filtration, and sample cell path length. The
updated procedure was subjected to single-and multi-laboratory evaluations, and the results were
used to determine quality assurance and quality control criteria for assessing method performance.
The updated method was also compared to the 1971 version and found to yield similar values in most
cases. The complete, updated method,NCASI Method Color 71.01, is included as an appendix to
this report. The results of this investigation will be useful to mills that measure color in process
effluents, treated final effluents, and receiving waters.
Ronald A.Yeske
May 2000
National Council for Air and Stream Improvement

AN UPDATE OF PROCEDURES FOR THE MEASUREMENT OF
COLOR IN PULP MILL WASTEWATERS
TECHNICAL BULLETIN NO. 803
MAY 2000
ABSTRACT
NCASI Method 253 was originally developed in 1971 to provide a technique for color measurement
in pulping wastewaters and their receiving waters. Because the processes of pulp and paper
production have changed considerably since that time,a study was undertaken with the objective of
updating the method. The color of pulp mill effluents is highly pH-dependent, and the pH adjustment
procedure included in Method 253 sometimes resulted in less than optimum stability of pH during the
analytical procedure. The use of a buffer to stabilize pH and reduce the erroneous increase in
absorbance was investigated and successfully implemented. Experiments were conducted to
investigate approaches for removing turbidity from pulp mill wastewater samples, since turbidity can
interfere with the assessment of color by scattering light and introducing a high bias. Centrifugation
was investigated as an alternative to filtration for the removal of turbidity. The percent decrease in
turbidity was consistently higher for aliquots treated using filtration vs. centrifugation. In addition,
the resultant color values were consistently higher for samples that were centrifuged. The current
technique,use of a 0.8 µm membrane filter,proved to be an effective method of turbidity removal in
pulp mill wastewaters. Pre-filtration of the samples using a 1 µm glass fiber filter was confirmed as
an acceptable method for reducing filter plugging of the 0.8 µm membrane filters. Comparisons of
three different types of membrane filters demonstrated that similar results could be obtained with any
of the three filter types. The selection of a wavelength of 465 Tim was confirmed to be valid in low
color effluents for the spectrophotometric measurement of absorbance. Finally,the method was
assessed at both the single-and the inter-laboratory level for ruggedness,precision, and accuracy.
The average relative standard deviations for the single laboratory precision were 2.8%in biologically
treated effluents and 7.1%in treatment plant influents. The average relative standard deviations for
the inter-laboratory precision were 15%in biologically treated effluents and 24.1%in treatment plant
influents. A well-defined and documented method for the measurement of color was developed;
including quality control and quality assurance criteria. The updated method is included in this report
as Appendix B.
KEYWORDS
color units,true color,turbidity, filtration,pH stability, spectrophotometer,platinum cobalt
RELATED NCASI PUBLICATIONS
Technical Bulletin No.253 (December 1971). An investigation of improved procedures for
measurement of mill effluent and receiving water color.
National Council for Air and Stream Improvement

CONTENTS
1.0 INTRODUCTION........................................................................................................................I
2.0 BACKGROUND ..........................................................................................................................1
3.0 RESEARCH OBJECTIVES.........................................................................................................2
4.0 EXPERIMENTS AND RESULTS...............................................................................................2
4.1 Sampling Site Selection and Sample Collection.................................................................2
4.2 Analytical Methods and Instrumentation............................................................................3
4.3 Wavelength Selection Verification.....................................................................................3
4.4 pH Adjustment Validation Experiments.............................................................................4
4.5 Turbidity Removal Experiments.........................................................................................7
4.6 Sample Volume Selection.................................................................................................13
4.7 Effects of Various Light Path Lengths on Resultant Color Values...................................13
5.0 UPDATED METHOD COLOR 71.01 VALIDATION AND QA/QC.......................................15
5.1 Brief Description of NCASI Method Color 71.01: The Updated Color Method.............15
5.2 Preparation of the Calibration Curve................................................................................15
5.3 Daily Calibration Verification...........................................................................................15
5.4 Single Laboratory Precision...............................................................................................16
5.5 Comparison of Updated NCASI Method Color 71.01 to NCASI Method 253.................17
5.6 Inter-laboratory Investigation of NCASI Method Color 71.01.........................................18
6.0 SUMMARY AND CONCLUSIONS.........................................................................................21
REFERENCES........................................ ............................................................................................22
APPENDICES
AStatistical Data.................................................................................................................Al
B NCASI Method Color 71.01 ............................................................................................B 1
C Inter-laboratory Study Plan,Procedure, and Data Sheet..................................................Cl
D Youden Pair Statistical Analysis Plots.............................................................................D1
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TABLES
Table4.1 Description of Mills............................................................................................................3
Table 4.2 Effects of Pre-filtration vs.No Pre-filtration on True Color...............................................8
Table 4.3 Comparison of Various Membrane Filters...........................................:............................I I
Table 4.4 Effects of Sample Volume on the True Color Value Determined ....................................13
Table 4.5 Calibration Curves for Various Light Path Length Cells..................................................14
Table 4.6 Summary of Light Path Length Experiments....................................................................14
Table 5.1 Summary of Daily Instrument Calibration Checks...........................................................16
Table 5.2 Summary of the Statistics Comparing NCASI Methods 253 and Color 71.01
inDifferent Matrices.........................................................................................................18
Table 5.3 Summary of the True Color Results and Percent Recoveries for the
QA/QC 125 PCU Standard...............................................................................................19
Table 5.4 Inter-laboratory Study: Summary of Results ....................................................................20
Table 5.5 Results of the Inter-laboratory Study Youden Pair Analyses............................................21
FIGURES
Figure 4.1 Absorption Curve Overlap..................................................................................................4
Figure 4.2 Effects of Sample pH on True Color Value Determined....................................................5
Figure 4.3 pH Stabilization Using Various Buffers in an Effluent Sample with a
Color Value of Approximately 100 PCU............................................................................6
Figure 4.4 pH Stabilization Using Various Buffers in an Effluent Sample with a
Color Value of Approximately 360 PCU............................................................................7
Figure 4.5 Effects on Sample Turbidity and Color:Filtration vs. Centrifugation................................8
Figure 4.6 Filter Porosity Effects on Mill B Effluent Turbidity and Color..........................................9
Figure 4.7 Filter Porosity Effects on Mill C Influent Turbidity and Color........................................10
Figure 4.8 Turbidity Agent Removal Results: Effluent Sample.........................................................12
Figure 4.9 Turbidity Agent Removal Results: Lignin Solution Sample.............................................12
Figure 4.10 Color Units of Five Effluent Samples Using Various Light Path Length Cells................14
Figure 5.1 Comparison of Resultant Color Values in Different Sample Matrices Using
NCASI Methods 253 and Color 71.01..............................................................................17
Figure 5.2 Comparison of Post-filtration pH in Different Sample Matrices Using
NCASI Methods 253 and Color 71.01..............................................................................18
National Council for Air and Stream Improvement

AN UPDATE OF PROCEDURES FOR THE MEASUREMENT OF COLOR IN
PULP MILL WASTEWATERS
1.0 INTRODUCTION
Many mills routinely monitor color as a tool in assessing wasteload for Best Management Practices
(BMP),to assist in evaluating process changes, as a requirement of a facility's National Pollution
Discharge Elimination System(NPDES)permit,and to monitor effluent and receiving water quality.
In 1971, in an effort to standardize the measurement of color in pulp mill wastewaters,NCASI
published Technical Bulletin No. 253,An investigation of improved procedures for measurement of
mill effluent and receiving water color(NCASI 1971). Since then,the nature of pulp mill wastewater
samples has changed due to the application of process technologies such as oxygen delignification
and chlorine dioxide substitution, as well as improvements in spent liquor management.
Subsequently,the matrices currently being assessed differ from the matrices initially used to develop
the NCASI method. In some instances,problems have been encountered with pH stability and
turbidity interfering with the accurate assessment of true color,using Method 253. In addition, an
effort was made to make the method more consistent with current NCASI method protocols and to
define quality assurance and quality control (QA/QC)parameters. In response to these issues,
NCASI initiated a task to optimize the NCASI color method for application to pulp mill wastewaters.
2.0 BACKGROUND
Color in pulp mill effluents may result from the presence of several substances in the wastewater that
contribute different chromophoric characteristics to the matrix. The largest portion of this
chromophoric component is thought to be the high molecular mass materials that result from
degradation of lignin during pulping and bleaching processes. This high molecular mass material
(molecular weights greater than 1000) carves several chromophoric structures that impart light-
absorbing qualities to the resulting effluents (Kringstad and Lindstrom 1984). The measurement of
color in industrial wastewater samples is typically limited to true color,which is the color of samples
from which turbidity has been removed. The measurement of color present in pulp mill wastewaters
can be determined using several different methods,including the visual comparison method,
spectrophotometric method,colorimetric method, and tristimulus filter method (Standard Methods
1998;USEPA 1971, 1978). Within the pulp and paper industry,the spectrophotometric methods,
which include NCASI Method 253, are frequently used to assess true color in wastewaters. NCASI
Method 253 measures the absorbance of a pulping mill wastewater or receiving water sample at a
wavelength of 465 rlm, once the sample has been adjusted to pH 7.6 and filtered through a 0.8 µm
membrane filter to remove turbidity.
The determination of a true color value is extremely pH dependent,with the color value increasing as
the pH of the sample increases. Therefore, controlling the pH of the sample during filtration and
measurement of absorbance is of great importance.
The turbidity of the sample can also influence the color value determined. Turbidity is an expression
of optical properties that cause light to be scattered or absorbed rather than transmitted in a straight
line through the sample. Suspended materials such as clay, fiber,titanium dioxide,precipitated
calcium carbonate, humic materials, and lignin may cause turbidity in pulp mill wastewaters.
Because much of the color in effluent samples is due to high molecular mass (HMM) materials which
are byproducts of the degradation of lignin, it is difficult to devise an optimal method for removing
turbidity without removing some of the true color. The true color in a sample,when determined using
a spectrophotometric method,is the dissolved color which absorbs light as it is transmitted through
the sample. It is desirable to remove the greatest amount of turbidity from the samples while limiting
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2 Technical Bulletin No. 803
c
the amount of true color removed. This optimum may vary from sample to sample, depending on the
particles contributing to the overall turbidity and true color, and the ease with which they are
removed. The majority of color measurement methods,including NCASI Method 253, use filtration
or centrifugation for the removal of turbidity from a sample. The filtration technique can produce
results that are consistent from day to day in the same lab and among different labs, but may also
remove some of the true color. Centrifugation avoids the interaction of color with the filtering
material,but it can be difficult to obtain consistent results due to variations in the nature of the
sample,the size and speed of the centrifuge in use, and reintrainment of turbidity during sample
transfer.
When a spectrophotometer is utilized for the determination of color, several instrumental parameters
can also influence the overall results. These parameters include the wavelength selected for
measurement of absorbance, differences in light path lengths, the condition of the cell, the presence of
stray radiation,reflection losses, scattering losses,photocell fatigue, source fluctuations, and loss of
wavelength calibration (Ingle and Crouch 1988). It is also critical that the cells used to measure
absorbance are clean,free of scratches, and reproducibly placed in the spectrophotometer. For these
reasons, use of properly calibrated equipment in good working order is important.
3.0 RESEARCH OBJECTIVES
The four primary objectives of this research project were to:
1. evaluate the performance of NCASI Method 253 for the measurement of color when used on
influent and effluent samples from present-day pulp mills exhibiting low effluent color;
2. develop and evaluate various approaches to improve the color measurement procedure for the
assessment of true color in influent and effluent samples from present-day pulp mills exhibiting
low effluent color. This objective involves the development of techniques to stabilize sample pH
during filtration and absorbance(color)measurement, and the investigation of potential
interference in the color method(including different sources of turbidity);
3. provide a well-defined and documented method for the measurement of color that incorporates
quality assurance and quality control (QA/QC) criteria and is consistent with EPA's method
development guidelines,NCASI method protocols, and current NPDES requirements for the
industry; and
4. assess precision and accuracy by conducting intra-and inter-laboratory investigations using the
updated procedure.
4.0 EXPERIMENTS AND RESULTS
4.1 Sampling Site Selection and Sample Collection
Table 4.1 provides summary descriptions of the mills that provided samples for this research.
Information in the table shows wood type, bleaching sequence, average daily production, average
daily water usage, and wastewater treatment plant(WTP)type. Grab and composite samples were
collected from six bleached kraft mills that utilize oxygen delignification and/or high chlorine dioxide
substitution. During the course of this research, additional samples from a thermomechanical pulping
mill and an unbleached kraft mill were also tested. Samples of biologically treated effluent, influent
to the treatment system,primary effluent(effluent from primary treatment before secondary
treatment),and receiving water were analyzed. The unpreserved samples were collected by mill
personnel and shipped overnight on ice to the NCASI West Coast Regional Center(WCRC). The
samples were stored at 4°C until analyzed. Prior to manipulations,the samples were removed from
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Technical Bulletin No. 803 3
the refrigerator and allowed to warm to room temperature. Settled solids were re-suspended by
vigorously shaking the sample bottles prior to use.
Table 4.1. Description of Mills
Mill Wood Bleaching Average Daily Average Daily WTP
Code Typeb Sequence` Production Water Usage` Type'
A SW D(EO)WDED 950 16 ASB
B SW/HW (CD)EHD 1450 44 AS
C SW/HW O(CD)ED 1850 . 28 ASB
D SW/HW (CD70)(EP)D 680 13.5 AS
E SW/HW CEDD 1700 32 AS
F SW unbleached 1090 24 ASB
G SW sodium hydrosulphite 750 5 ASB
H SW OM(EOP)MP 500 11 ASB
' The mills sampled in this study used the kraft process(with the exception of Mill G,which is a TNT mill).
b SW=softwood;HW=hardwood.
` D=chlorine dioxide;E=alkaline extraction;C=chlorine;H=hypochlorite;O=oxygen;
M=chlorine monoxide;P=hydrogen peroxide;W=washing stage.
d Average daily production in air dried tons/day.
` Average daily water usage in million gallons/day.
f ASB=aeration stabilization basin;AS=activated sludge.
4.2 Analytical Methods and Instrumentation
4.2.1 Brief Description of NCASI Method 253
NCASI Method 253 (NCASI 1971) involves selecting a 200 mL sample of wastewater or water and
adjusting the pH to 7.6 with hydrochloric acid (HCI)or sodium hydroxide(NaOH),while assuring
less than a 1% change in the sample volume. A 50 ml.,aliquot of this pH-adjusted sample is filtered
through a 0.8 µm porosity membrane filter pre-rinsed with distilled water. A portion of the filtered
sample is transferred to an absorption cell, and the sample's absorbance is measured at 465 tlm using
a spectrophotometer. The color is determined by spectrophotometric comparison of the sample with
known concentrations of platinum cobalt solutions.
4.2.2 Instrumentation
Measurements were conducted at the NCASI WCRC using a Spectronic 21D spectrophotometer
equipped with a digital readout. This spectrophotometer utilizes a tungsten light source and has a
wavelength range of 340 to 1000 rlm, with a spectral slit width of 10'gm. The color units for a
sample are determined by comparing the absorbance reading with a standard curve prepared using
solutions of platinum cobalt. Turbidity measurements were done on a Hach Model 18900 Ratio
Turbidimeter with ranges of I to 2, 1 to 20, and 1 to 200 nephelometric turbidity units(ntu). The unit
is equipped with a tungsten lamp, and was operated using the procedure in the instrument manual
(Hach 1991).
4.3 Wavelength Selection Verification
Selection of the wavelength used to measure the absorbance of the samples influences the accuracy
and precision of color measurements. Ideally, the absorbance observed for samples of similar color
values should overlap the absorption of the standard selected to assess the color value(Ingle and
Crouch 1988). NCASI conducted experiments during the development of Method 253 to determine
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4 Technical Bulletin No. 803
e ,
the wavelength at which the platinum cobalt standard overlapped the absorption curve of pulp mill
wastewater samples. The experiments involved plotting the absorption curves for bleached kraft mill
effluent samples in each of 18 sets of data from a survey representing 18 different instruments. The
results of the experiments indicated that the areas of the visible spectrum yielding an exact match of
sample with the platinum cobalt color standard occurred in the range of 450 to 480 11m(NCASI
1971). The results also indicated that accuracy and precision could be achieved by measuring the
absorbance at a wavelength of 465'rim.
To verify this wavelength selection in current sample matrices, an experiment was performed which
involved measuring the absorption curve for a 200 platinum cobalt unit(PCU) standard,a
biologically treated effluent(Mill A), and a treatment system influent(Mill B). The absorption
curves were prepared within a wavelength range of 400 to 700 rlm in intervals of 1011m using
samples with color values of approximately 200 PCUs. The absorption curves for this experiment are
plotted in Figure 4.1. Ideally, the plots for the absorbance vs. wavelength for the samples tested
should show lines overlapping the platinum cobalt standard curve at the wavelength used for
measuring sample absorbance in the method. The mill wastewater samples tested did not show
distinct peaks,indicating that a mixture of chromophores are responsible for the resulting color
observed. As wavelength increased,the absorbance of light gradually decreased. Optimum overlap
occurred in the range of 460 to 47071m. The selection of a wavelength of 46511m for the
measurement of effluent and influent color was valid.
0.20
+Color Standard I
0.15
Effluent
flu
R i
0 0.10 Influent
d 0.05
0.00
400 410 420 430 440 450 460 470 480 490 500 510 520 530 540 550
Wavelength (nm)
Figure 4.1. Absorption Curve Overlap.
4.4 pH Adjustment Validation Experiments
4.4.1 The Effects ofpHon Color Determinations
In NCASI Method 253,the pH of the sample is to be adjusted to 7.6 using a solution of NaOH or
HCL As previously noted,users of this method sometimes find the pH difficult to stabilize. In most
cases,the pH of the sample increases following filtration through a 0.8 µm membrane filter and over
time. Comparative work conducted as part of an inter-laboratory evaluation of the updated NCASI
Method Color 71.01 confirmed these observations (Section 5.5,Figure 5.1).
To examine the effects of pH on the color value determined for a biologically treated pulp mill
effluent sample,the absorbance of a sample at various pH values was measured. A 200 mL aliquot of
sample(Mill A)was adjusted to pH 7.6 and filtered through a 0.8 µm membrane filter. A 25 mL
aliquot was taken from the filtrate and transferred to a beaker. The initial pH and absorbance were
National Council for Air and Stream Improvement

Technical Bulletin No. 803 5
measured. The sample pH was then adjusted from 7.0 to 8.4 in increments of 0.2. Absorbance was
measured at each pH level and color values were calculated based on these measurements. This
experiment was repeated with a biologically treated effluent from Mill C. The results of the
experiments are illustrated in Figure 4.2. The color values for Mill A showed a consistent increase
across the range of pH values tested. The color values for Mill C appeared to be somewhat stable
between pH 7.6 and 8.0. Color values measured at pH 8.2 and 8.4 indicate a sharp increase,then
decrease, which could not be effectively explained. The percent increases in the color values
determined from pH 7.6 to 8.4 were 7.2%and 2.7%for Mill A and Mill C,respectively, while the
percent decreases in the color values determined from pH 7.6 to 7.0 were 6.5%and 4.0%for Mill A
and Mill C,respectively.
This experiment demonstrates the importance of stabilizing the pH of pulp mill effluent samples at a
given value and recording the value at which color assessments are determined.
Mill A Effluent Mill C Effluent
450 260
440
430 T 255
a 420 0250 1
410
> 400 � 245 \
0 390 c 240
v 360 T U
i
235 -
370
360 i 230 I I
O N K t0 CG O N V O N C t0 m O N
pH pH
Figure 4.2. Effects of Sample pH on True Color Value Determined.
4.4.2 pH Stabilization Experiments
Given the importance of pH stabilization,NCASI investigated different buffering systems in an effort
to stabilize the pH of samples,and thereby reduce errors in color measurement associated with
fluctuations in pH. Several buffering systems were examined,including a phosphate buffer solution
(dibasic sodium phosphate and monobasic sodium phosphate,pH 7.6) which was found to stabilize
the pH of pulp mill effluents during research conducted by NCASI in 1981 (NCASI 1981).
Additional buffers investigated include a dry phosphate buffer in the form of a capsulated powder
(dibasic sodium phosphate and monobasic potassium phosphate,pH 7.0), and a biological buffer
solution of beta,beta-dihydroxy-1,4-piperazinebis(propanesulfonic acid) dihydrate(POPSO,
pH 7.2 to 8.5) (Ferguson et al. 1980)prepared at a concentration of 3 g/L in organic free reagent
grade deionized water(Barnsteadr"'water).
Each buffer was studied for its effectiveness in stabilizing the pH of the samples during the filtration
process and over time. Four 50 mL aliquots of an effluent sample from Mill H with a color value in
the range of 99 to 176 PCU were prepared for use in this experiment. The first aliquot was not treated
with a buffer,the second was treated with 1 mL of the pH 7.6 phosphate buffer solution,the third was
treated with 0.60 grams of the pH 7 phosphate buffer capsule,and the fourth was treated with 1 mL of
the POPSO buffer solution. Each sample was then adjusted to pH 7.6±0.05 using a 20% sodium
hydroxide solution or 10%hydrochloric acid solution, and filtered through a 0.8 µm membrane filter.
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6 Technical Bulletin No. 803
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To determine the stability of sample pH,the pH was recorded initially, during adjustment, after
filtration,at 15-minute intervals for one hour, and then hourly for three hours. After filtration the
absorbance of each aliquot was measured using a spectrophotometer set at a wavelength of 465 71m.
The color value was determined from the measured absorbance and the equation derived from the
calibration curve.
As indicated in Figure 4.3,the pH of the sample containing no buffer and the sample containing the
POPSO buffer increased following filtration and continued to gradually increase over the three-hour
period. In comparison,the pH of the samples buffered with phosphate remained relatively constant.
The fluctuation in pH observed between the buffered and non-buffered solutions represents a 77%
increase in the color values determined immediately following filtration of the sample.
-A No Buffer tPhosphate Buffer Solution — Phosphate Buffer Capsule x POPSO
8.3
8.2
8.1
8 176 PCU
y
x 7.9
7.s
7.7
7.6
7.5
99 PCU
7.4
N
e 0
'time (hours)
Figure 4.3. pH Stabilization Using Various Buffers in an Effluent Sample
with a Color Value of Approximately 100 PCU.
This experiment was repeated using a biologically treated effluent from Mill A with a color value in
the range of 362 to 420 PCU. The experiment followed the procedure outlined above, with two
exceptions. The pH was measured every hour for four hours,then once again after a period of
24 hours. The results of this experiment are presented in Figure 4.4,and follow the same general
trends in this effluent using the various buffers. The fluctuation in pH between the phosphate
buffered and non-buffered samples represents a 16%increase in the color values determined
immediately following filtration.
Based on the results of these experiments, the color procedure was modified to include the addition of
a phosphate buffer prior to filtration. The phosphate buffer capsule proved to be a convenient and
effective method for stabilizing the pH of effluent and influent samples. Additional experiments were
conducted to determine if pH 7 or pH 8 phosphate buffer capsules stabilized the sample pH more
effectively. The use of pH 7 or pH 8 buffer capsules followed by fine adjustment of the final pH to
7.6±0.05 with NaOH or HCl resulted in the stabilization of the sample pH at 7.6±0.05 following
filtration. It was observed that the pH 7 buffer capsule dissolved more readily into the effluent
samples;therefore it was utilized throughout the remainder of this study.
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Technical Bulletin No. 803 7
�No Buffer--M—Phosphate Buffer Solution —,A Phosphate Buffer Capsule POPSO
8.3
8.2
8.1
8 41y PCU
7.9
S
78
7.7
7.6 —
7.5
362 PCU
7.4
6
O
9 c Time(hours)
a
Figure 4.4. pH Stabilization Using Various Buffers in an Effluent Sample
with a Color Value of Approximately 360 PCU.
4.5 Turbidity Removal Experiments
The presence of turbidity in a sample can cause light scattering and/or increase the absorption,
thereby increasing the resultant color value. True color is the color due to dissolved substances that
absorb light. The objective in this research was to determine a reliable method for removing a
majority of sample turbidity with the smallest corresponding change in the true color value. Due to
the nature of the multi-component matrix and the different methods used for assessing true color and
turbidity, this can be a very difficult task.Several techniques for the removal of turbidity were
investigated as part of this work. Experiments were conducted to examine the effects of a pre-
filtration step, centrifugation vs. filtration, and filter porosity on the true color value of pulp mill
wastewater samples.
4.5.1 Pre-filtration Experiments
Clogging of filters has been observed during filtration of pulp mill wastewater samples using the
recommended 0.8 µm membrane filters (NCASI 1971). This can result in artificially low color
values because clogging effectively reduces the pore size of the filter,resulting in the removal of true
color bodies from the sample. Slow sample filtration can also increase the time required to process
samples, and require the use of multiple 0.8 µm membrane filters. It is sometimes useful to remove
large particulate matter by pre-filtering the sample through a 1.0 µm glass fiber filter. This allows the
sample to pass more readily through the smaller porosity membrane filters, and reduces the likelihood
that the filter will plug and remove true color along with turbidity.
An experiment to investigate pre-filtration was simultaneously conducted with the buffer comparison
experiment. Samples were treated with the buffers as described in Section 4.4.2, but one set of
samples was filtered with a 1.0 µm glass fiber filter before treatment, and one set of samples was not
pre-filtered before treatment with the various buffers. As indicated in Table 4.2,less than 4.6%
variation was observed in all cases between the results with and without pre-filtration with a 1.0 µm
glass fiber filter.
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8 Technical Bulletin No. 803
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The color values were slightly higher in the samples that were pre-filtered,indicating that the pre-
filtration of samples may have decreased clogging of the 0.8 µm membrane filters, resulting in less
true color removal.
Table 4.2. Effects of Pre-filtration vs.No Pre-filtration on True Color
Phosphate Phosphate
No Buffer Buffer POPSO
Buffer Solution Capsule Buffer
Filtration Technique Added Added Added Added
Pre-filtered 1.0 µm GFFa then 0.8 µm NW 419 396 362 396
0.8 µm MFe 402 379 346 396
Relative percent difference (RPD) 4.0% 4.4% 4.6% 0%
a GFF is a glass fiber filter.
" MF is a membrane filter.
4.5.2 Centrifugation Experiments
Centrifugation was also investigated as an alternative to filtration for the removal of turbidity from
pulp mill wastewater samples. Samples of biologically treated effluent from Mills A,F, G, and H
were utilized to determine the effectiveness of centrifugation vs. filtration through a 0.8 µm
membrane filter for the removal of sample turbidity. Color values were also determined. The initial
turbidities of the effluent samples were determined by measuring duplicate samples and calculating
the average turbidity of the two samples. Then,200 mL aliquots were buffered (pH 7 phosphate
buffer capsule) and the pH was adjusted to 7.6±0.05 using a 10% sodium hydroxide solution. The
aliquots were split into four aliquots of 50 mL each. Two aliquots were filtered using a 0.8 µm
membrane filter,and the absorbances were measured at 465 ilm. The true color values were
determined for the samples using the absorbance measurements. The turbidity of each aliquot was
also measured. The remaining two aliquots were centrifuged for 30 minutes at 2100 revolutions per
minute(rpm), and the absorbances and turbidities of the supernatant layer were measured. The
results are presented in Figure 4.5, which shows the average color value determined for the duplicate
samples from each mill on the Y axis. The color values are represented by bars, and the percent
decreases in sample turbidity after each treatment are represented by lines, with corresponding values
on the right axis.
OFiltered Centrifuged 0 Filtered —0—Centrifuged
800 100
�r 700
80
U 600 `o
500 60F
400
x
A 40 z
3003 H2'
d
o u i
U 200 20100 ? ;0 as 0
Mill A Mill F Mill G Mill H
Mill Code
Figure 4.5. Effects on Sample Turbidity and Color: Filtration vs. Centrifugation.
National Council for Air and Stream Improvement

• Technical Bulletin No. 803 9
The percent decrease in turbidity was consistently higher for aliquots treated using filtration through a
0.8 µm membrane filter than for samples treated using centrifugation for 30 minutes at 2,100 rpm.
The resultant color values were consistently higher for the samples that were centrifuged to remove
turbidity. The average increase in the color values determined for the centrifuged samples relative to
the filtered samples was 21%, with a range of 2 to 32%.
4.5.3 Filter Porosity Verification Experiments
NCASI Method 253 recommends the use of a 0.8 µm membrane filter for removal of turbidity. To
verify that this filter porosity is still appropriate for low color effluents,an experiment was conducted
to evaluate the amount of color and turbidity being removed using filters of various porosities. This
involved filtering the same 50 mL aliquot of sample through successively smaller filters to observe
the change in color and turbidity determined with each filtration. The filtration series included 2.7,
1.5, and 1.0 µm glass fiber filters,followed by 0.8, 0.65,0.45, and 0.22 µm membrane filters.
Absorbance and turbidity were measured after each filtration. The macromolecules that constitute the
true color in a pulp mill wastewater sample are in the range of 0.1 to 0.7 microns (NCASI 1971),
therefore the color observed above 1 µm was assumed to represent color due to suspended and
dissolved components (apparent color) as well as true color(dissolved components only). Figures 4.6
(effluent,Mill B) and 4.7 (influent,Mill C) illustrate the changes in sample color and turbidity
following filtration through the 1 to 0.22 µm membrane filters (x-axis);the values for the 2.7 and
1.5 µm glass fiber filters are excluded. The graph on the left illustrates the changes in color observed
following each filtration, while the graph on the right shows the effects on sample turbidity. The
percentage of the initial turbidity removed following each filtration is indicated above the bars of the
graph on the right. In all cases,as the filter porosity decreased,the resulting color value decreased.
Due to the interactive nature of light scattering(due to turbidity) and absorbance(due to true color),
this would be the anticipated trend.
88% "
150
149 1.4
i
145 142 1.2
U 139 q 1
140 136 0.8
135 132 :2 0.6 95%
c 1
130 `0 0.4 97%
125 F 0.2
0
120
1 0.8 0.65 0.45 0.22 1 0.8 0.65 0.45 0.22
Filter Porosity(pm) Filter Porosity (pm)
Figure 4.6. Filter Porosity Effects on Mill B Effluent Turbidity and Color.
It is difficult to determine whether the continual decrease in the color values was due to an increase in
the turbidity removed or to the removal of color bodies from the samples by the filters. For the
Mill B effluent sample,filtration below 0.8 µm resulted in a difference of 7% in the resultant color
value,down to a filter porosity of 0.22 pm. Between the I µm and 0.8 pm filtrations, 95% of the
color remained while 50% of the remaining turbidity was removed; and between the 0.8 pm and
0.65 µm filtrations,97% of the color remained while 14%of the remaining turbidity was removed.
Following filtration through the 0.8 µm filter, 94% of the initial turbidity was removed, as indicated
by the numbers above the bars. The initial measurement of turbidity was 4.1 mu.
National Council for Air and Stream Improvement

10 Technical Bulletin No. 803
Successive filtration continued to remove portions of the turbidity,but in smaller increments. This
may be due to the removal of color bodies by the smaller porosity filters. A regression analysis of the
change in turbidity vs. color did not show a significant relationship between the two (Appendix A,
Section A2). In other words, an incremental change in turbidity did not correlate to an incremental
change in color. Therefore,it is more likely that the changes noted in the color values were related to
the removal of color bodies from the samples than to the removal of additional turbidity.
250 221 198 6 98.5%
U 200 188 181 175 5
a
y 150
TO fl 3 99.4%
100 a
c 2 99.6% j
U 50 F 1 ! 99.8% 99.9%
0 0 '
1 0.8 0.65 0.45 0.22 1 0.8 0.65 0.45 0.22
Filter Porosity(pm) Filter Porosity(pin)
Figure 4.7. Filter Porosity Effects on Mill C Influent Turbidity and Color.
For the Mill C influent sample,filtration below 0.8 µm resulted in a difference of 12%in the resultant
color value,down to a filter porosity of 0.22 µm. Between the 1 µm and 0.8 µm filtrations, 90%of
the color remained while 60%of the remaining turbidity was removed; and between the 0.8 pm and
0.6 µm filtrations, 95% of the color remained while 43% of the remaining turbidity was removed.
The overall decrease in the color value determined between the 0.8 µm and 0.22 µm filtrations was
13%,but the majority of the turbidity in the initial sample(99.4%) was removed following filtration
through the 0.8 µm membrane filter. A regression analysis of the change in turbidity vs. color for the
Mill C influent did not show a significant relationship between these two variables (Appendix A,
Section A2). These results indicate that the 0.8 µm membrane filter removed the bulk of sample
turbidity while having a minimal effect on the dissolved color bodies within the sample.
4.5.4 Comparison of Filter Types
There are several brands and types of membrane filters on the market, therefore this work included an
evaluation of various types of filters. Comparative experiments were conducted using three brands of
filters: Gelman MetricelT", Gelman Supor 8007"", and Nucleopore Membra-FilTM filters. Both
Gelman Metricel and Nucleopore Membra-Fil filters are made of mixed cellulose esters. The Gelman
Supor 800 filter is a hydrophilic polysulfone membrane filter.
A 400 mL aliquot of a biologically treated effluent sample from Mill D was adjusted to pH 7.6,then
50 mL portions were filtered through each membrane filter. Experiments involved three replicates
using Supor filters and three replicates using Metricel filters. The samples were not buffered prior to
pH adjustment.
The Nucleopore Membra-Fil was utilized because of the wide range of porosities commercially
available for this filter type. An experiment was conducted to compare the Nucleopore Membra-Fil
filter to the Gelman Metricel filter. A 400 mL aliquot of a biologically treated effluent sample from
Mill F was adjusted to pH 7.6,then 50 mL portions of this sample were filtered through each
membrane filter. Experiments involved three replicates using Nucleopore Membra-Fil filters and
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Technical Bulletin No. 603 11
three replicates using Metricel filters. The absorbances were measured and statistically compared for
differences.
The results for these two filter comparison experiments were evaluated using analysis of variance
(alpha=0.05)to determine if filter type affected color value. The results, shown in Table 4.3,do not
reveal a statistically significant impact of filter type on measured color.
Table 4.3. Comparison of Various Membrane Filters
Comparison p-value
Metricel and Supor 0.13
Metricel and Nucleopore Membra-Fil 0.42
The Metricel filters were used in the majority of the color experiments. The Nucleopore Membra-Fil
filters were used during the successive filtration experiments because they were available in a wider
range of porosities.
4.5.5 Investigations of Possible Turbidity Agents
NCASI examined several different turbidity agents potentially present in pulp mill wastewaters which
may interfere with the determination of true color. The purpose of these experiments was to
determine if a 0.8 µm membrane filter was effective in removing the turbidity agent while having a
minimal effect on true color, and to determine how different turbidity agents might interfere with the
determination of true color in biologically treated effluents. The turbidity agents explored included
precipitated calcium carbonate,titanium dioxide, lime mud,fiber,and green liquor dregs.
Each of these agents was added to separate aliquots of water in an amount adequate to achieve
approximately 25 to 50 mu of turbidity when 500 µL of the solution was spiked into a 50 mL volume.
These spiking stocks were spiked into 50 mL of deionized water, which was then buffered,pH
adjusted to 7.6±0.05, and filtered through a 0.8 µm membrane filter(Sample A). The same spike
amount of the turbidity agent solution was then added to 50 mL of an effluent sample(Mill A),
buffered,pH adjusted, and filtered(Sample B). Finally,50 mL of an effluent sample without the
added turbidity agent was buffered,pH adjusted, and filtered(Sample Q. The absorbance and
turbidity values were measured and recorded for each sample (A,B,and C) initially, after the addition
of buffer and pH adjustment, and after filtration. The experiment was conducted with three replicates
of each sample type (A,B, and Q.
The average turbidity of each set of three replicates was calculated. The average value calculated for
Sample C(no turbidity added) and Sample A(turbidity spike in water)were added together. This
value was then compared to the turbidity value of Sample B,the turbidity-spiked effluent. This
comparison was conducted to determine if the turbidity value was affected by the sample matrix. The
turbidity values determined for Sample C plus Sample A were equivalent to the turbidity values
measured for Sample B,indicating that the turbidity agent spike was not affected by the sample
matrix.
An additional component of this experiment was to determine whether some turbidity agents are more
readily removed by filtration than others. The presence of turbidity in the samples following filtration
can cause erroneously high color values due to light scattering. Figure 4.8 illustrates the average true
color value determined for the three replicates of each sample type following filtration through the
0.8 µm membrane filter. The color values are indicated on the y-axis,while the x-axis lists the
turbidity agent used. The black bars represent the average true color value determined for Sample C
(effluent only) and the white bars represent the average color value determined for Sample B (effluent
National Council for Air and Stream Improvement

12 Technical Bulletin No. 803
plus turbidity agent). The percentage of the turbidity removed by filtration is indicated above each
set.
25% 97% 92% 98% 96%
600 T
550
500
`0 450
V 400
Titanium Fiber Dregs Lime Mud Calcium
Dioxide Carbonate
(PCC)
Figure 4.8. Turbidity Agent Removal Results:Effluent Sample.
The results indicate that the 0.8 µm membrane filter effectively removes the turbidity introduced by
the indicated agents,with the exception of titanium dioxide. The results also indicate that the true
color values determined for the samples with and without added turbidity varied by less than 3%
following filtration through a 0.8 µm membrane filter.
The experiment was repeated using a solution of lignin which served as a surrogate for pulp mill
wastewater true color to examine the trends in a solution that contained no other source of turbidity
except the spiked turbidity agent. As indicated in Figure 4.9, turbidity was effectively removed for all
of the agents tested except the titanium dioxide. In addition,the true color values determined for the
lignin sample with and without added turbidity from fiber,dregs, lime mud,and precipitated calcium
carbonate varied by less than 7%,although in general the color values determined in the turbidity
agent spiked lignin samples resulted in slightly increased color values. The true color values
determined for the lignin sample with and without added titanium dioxide varied by 25%.
350
U 300 j 23% 97% 93% 95% 95%
250 T
200 T
150
`0 100 -F
U 50
0 ,
Titanium Fiber Dregs Lime Mud Calcium
Dioxide Carbonate
(PCC)
Figure 4.9. Turbidity Agent Removal Experiments:Lignin Solution Sample.
National Council for Air and Stream Improvement

Technical Bulletin No. 803 13
4.6 Sample Volume Selection
It was previously observed that the volume chosen for filtration by each analyst can significantly alter
the final color reported for the sample and may account for increased variability in observed results
(NCASI 1971). This occurrence is usually related to filter plugging that can occur when filtering a
larger sample volume. The filter plugging reduces the effective filter pore size, which can remove
some of the components contributing to the true color of a sample. To investigate this observation,
duplicates of four aliquots of sample with volumes of 25,50, 100,and 200 mL were treated
identically (i.e.,buffered, pH adjusted, and filtered through 0.8 µm membrane filter). This
experiment was repeated using biologically treated effluents from Mill A and Mill B and an influent
to the treatment system from Mill B. If the filtering rate slowed or foaming was observed, the
filtration was stopped and another filter was used to complete the filtration of the total aliquot of
sample. The results of this experiment are shown in Table 4.4. The percent relative standard
deviation of the color values determined using the 25,50, 100,and 200 mL volumes ranged from 0.7
to 5.6%,indicating that when using this technique, sample volume did not effect the overall color
value determined. Therefore,a 50 mL sample volume was chosen for ease in manipulation and
filtering, and the appropriate filtration technique is specified in the updated method (Appendix B).
The 50 mL sample volume was selected over a 25 mL sample to allow for easier pH adjustment of the
initial sample without changing the sample volume by more than 1%.
Table 4.4. Effects of Sample Volume on the True Color Value Determined
25 mL 50 ml 100 mL 200 mL Average RSD°
Sample (PCU) (PCU) (PCU) (PCU) (PCU) M
Mill A Effluent 617 580 597 583
603 603 580 b 595 2.2
Mill B Effluent 173 176 176 176
176 173 176 176 175 0.7
Mill B Influent 189 186 186 206
193 176 203 209 194 5.6
Relative standard deviation expressed as a percent.
b This determination was not available due to a limited sample availability.
4.7 Effects of Various Light Path Lengths on Resultant Color Values
An experiment was conducted to investigate the effect of light path length on the determined color
value. Samples from five different mills (Mills A,E,F, G, and H)were measured to determine the
color value of each matrix using a 10, 20,25, 50, and 100 mm light path length cell. The samples
were analyzed in replicates of three, and the color values were calculated using the equations in
Table 4.5 for each specific light path length cell. These calibration curve equations were obtained by
analyzing a calibration curve ranging from 10 to 500 PCU using a curvette with the light path length
indicated in Table 4.5.
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14 Technical Bulletin No. 803
Table 4.5. Calibration Curves for Various Light Path Length Cells
Linear Equation y = mx +b R-squared Light Path Length(mm)
y=0.0003x—0.0003 1.000 10
y = 0.0005x+0.0028 0.9988 20
y=0.0006x—0.0004 0.9999 25
y=0.0014x—0.0003 1.000 50
y =0.0027x+0.0018 1.000 100
The average color values determined for the various samples,the range of color values reported, and
the relative standard deviations of these averages expressed as a percent are presented in Table 4.6.
Table 4.6. Summary of Light Path Length Experiments
Average Color Value Range of Color Values Relative Standard Deviation
Mill Code (PCU) (PCU) M
A 514 486-547 5
E 184 178 - 190 — 3
F 78 75 - 81 3
G 274 265 -288 4
H 1186 1112- 1271 6
Figure 4.10 illustrates the results of this experiment. The color values of the samples used in this
experiment ranged from 75 to 1,271 PCU. The values plotted in Figure 4.10 are the average PCUs
determined for the three replicates using the indicated light path length cells. Due to limited sample
volumes,Mill H was not measured in the 100 mm light path length cell.
♦Mill A ■Mill E ♦Mill F A Mill G *Mill H
1400
1200
*
v 1000
a
g 800
c 600
�j 400
A A A A
200
0 ,
0 10 20 30 40 50 60 70 80 90 100
Light Path Length(nun)
Figure 4.10. Color Units (PCU) of Five Effluent Samples Using Various Light Path Length Cells.
The relative standard deviations (RSD),expressed as percents, are similar to the intra-and inter-
laboratory relative standard deviations determined for replicate analyses(Section 5.6). The RSDs are
also below EPA's color method precision criteria of 10% listed in the Federal Register(Federal
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Technical Bulletin No. 803 15
Register 1997),indicating that for color value determinations of samples within the range of 70 to
1,300 PCU, cell light path length is not likely to be important.
5.0 UPDATED METHOD COLOR 71.01 VALIDATION AND QA/QC
The previous sections of this bulletin presented.the results of experiments conducted to optimize the
NCASI color measurement method in pulp mill wastewaters. This section presents information
relating to the validation of the updated method (NCASI Method Color 71.01)and development of
quality control and quality assurance criteria.
5.1 Brief Description of NCASI Method Color 71.01: The Updated Color Method
The updated procedure involves adding half of a pH 7 buffer capsule to a 50 mL sample of
wastewater or water to stabilize the pH, adjusting the pH to 7.6±0.05 with HCl or NaOH(such that
the volume change of the sample is less than I%), and filtering the aliquot through a 0.8 µm porosity
membrane filter pre-rinsed with distilled water. A portion of the filtered sample is then transferred to
an absorption cell and the absorbance is measured at 465 vim using a spectrophotometer with a
tungsten lamp-source and 10 rim spectral slit width.—The spectrophotometer capabilities should
include an operating range of 400 to 700 rim and an ability to emit light at a selectable wavelength of
465 rim, The color units for the sample are determined by comparing the absorbance reading with a
standard curve prepared using dilutions of a platinum cobalt stock solution. A full description of the
updated method can be found in Appendix B.
5.2 Preparation of the Calibration Curve
The linearity of the spectrophotometer used for this work was assessed by analyzing a five-point
calibration curve that ranged in concentration from 25 to 500 PCU. The calibration curve was
prepared using a stock platinum cobalt solution with an initial color value of 500 in volumes of 2.5,
10, 20,and 25 mL. These volumes were diluted with BamsteadTm deionized water to 50 mL in a
volumetric flask. The corresponding color unit values of these solutions were 25, 100,200,and
250 PCU. In addition, an aliquot of the undiluted stock platinum cobalt solution with a color value of
500 PCU was measured and included in the curve. The absorbances of these solutions were measured
at a wavelength of 465 rlm on a Spectronic 21D spectrophotometer with a tungsten lamp light source.
The various curves analyzed in this research utilized cuvettes with 10,20,25,50, or 100 min light
paths. Calibration curves were prepared using the results of these measurements by plotting the
absorbance values against the color units of each of the standards measured. A linear regression
equation was generated for each curve and used to calculate the color units of the samples from their
measured absorbances. Calibration criteria(Appendix B, Sections 10 and 17) were determined by
measuring several curves and developing acceptable criteria based on the coefficient of determination
(r-squared) from the linear equations generated for each curve. Throughout the course of this study,a
total of thirteen calibration curves were generated, with the results displayed in Appendix B,Table 6.
All of the curves analyzed had an r-squared value greater than0.9968.
5.3 Daily Calibration Verification
Virtually all instrumental analysis methods require that some type of calibration verification be
conducted at the beginning of each day or prior to analysis of samples. One objective of this project
was to bolster the QA/QC requirements of the color method (NCASI 1971). Therefore, a mechanism
for accomplishing daily calibration checks was employed during this investigation. The results from
these experiments form the basis for daily calibration criteria incorporated in the updated color
method(Appendix B, Section 9.2).
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16 Technical Bulletin No. 803
For all of the color analyses conducted as part of this project, the validity of the instrument calibration
curve was verified prior to sample preparation. Different calibration points were selected on each day
in order to verify the calibration over the full range of the curve. The results of the calibration
verification were calculated by dividing the measured concentration by the known concentration of
the standard and were reported as percent recovery.
During the course of this work, calibration verifications were completed on 47 occasions using
various light path length cells and color ranges from 25 to 500 PCU. The results of these calibration
verifications yielded an average percent recovery of 95%, a range of 88 to 118%, and a standard
deviation of 6.7. The distribution of percent recovery results can be used to suggest limits around
which the analyst should consider further evaluation of instrument performance or re-calibration of
the instrument. For this method,warning and action limits were calculated as the mean plus and
minus two standard deviations and three standard deviations,respectively. These limits are shown in
Table 5.1. When warning limits are exceeded,the analyst should investigate possible instrument
problems,perform a calibration verification of the instrument as recommended by the instrument
manual, check for contamination and evaporation of standard solutions, examine glassware for
scratches,re-zero the spectrophotometer, and reanalyze the standard. When the action limits are
exceeded,the analyst should likewise investigate potential problems,prepare a new calibration curve,
and reanalyze the curve as recommended in Section 5.2.
Table 5.1. Summary of Daily Instrument Calibration Checks
Average Warning Action Minimum Maximum Color Unit
Recovery' Standard Limits` Limitsd Recovery Recovery Range
(%) Deviation° (%) (%) (%) (%) (PCU)
94.9 6.7 81 - 108 75 - 115 88 118 25 -500
' Average recovery for 47 daily calibration checks.
s Standard deviation of the recoveries for 47 daily calibration checks.
Average recovery plus and minus two times the standard deviation.
d Average recovery plus and minus three times the standard deviation.
5.4 Single Laboratory Precision
5.4.1 Instrument Precision
The instrument precision of the Spectronic 21D, which was utilized throughout the single laboratory
validation of the updated method at NCASI's West Coast Regional Center,was verified by the
analysis of the midpoint of the calibration curve a total of seven times over an eight-hour period. The
results of the instrument precision experiment yielded a relative standard deviation of 1.4%for the
seven replicates of the 100 PCU standard.
5.4.2 Method Precision
The precision of the method was characterized and continuously monitored using duplicate analyses.
Throughout the single laboratory assessment of precision, a total of twelve different duplicate sample
pairs of both biologically treated effluent and treatment system influent from the mills listed in
Table 4.1, were analyzed. The relative percent differences for the duplicates ranged from 0.4 to -
14.1% for the biologically treated effluents,with an average relative percent difference of 2.8%. The
color values of the samples utilized in this assessment ranged from 81 to 1,112 PCU,indicating that
the precision of the method is consistent over a wide range of color values. The relative percent
differences observed for the treatment system influent duplicate pairs ranged from 0.1 to 13.2%,with
an average relative percent difference of 7.1%. The average relative percent differences for the
National Council for Air and Stream Improvement

Technical Bulletin No. 803 17
effluent and influent sample duplicates,were below EPA's standardized quality assurance and quality
control acceptance criteria of 10% for precision in color methods listed in the Federal Register
(Federal Register 1997).
5.5 Comparison of Updated NCASI Method Color 71.01 to NCASI Method 253
A comparison of the updated method and NCASI Method 253 was made using data from two
different NCASI laboratories. This comparison was done using biologically treated effluents from
Mills A and B,influents to the treatment system from Mills A and B, a prepared lignin solution,and a
receiving water sample collected below the discharge of Mill D. Trends that suggest there may be
some method differences were observed. The color values determined in five of the six matrices
tested were lower using the updated procedure(Figure 5.1). This lower color value often
corresponded to an observed difference in the post-filtration pH between the two methods
(Figure 5.2). In the matrices tested, a pH of 7.6±0.05 was achieved using the updated method,but
NCASI Method 253 samples were not buffered, and the post-filtration pH increased. The influent
sample from Mill A was an exception to this trend. This sample yielded a higher color value using
Color 71.01,although the pH of the sample remained at 7.6±0.05 using this method.
■Color-71.01 ❑Method 253
830
; 730
a 630
530
430
330
c 230
U 130
30 .
x
Sample Matrix
Figure 5.1. Comparison of Resultant Color Values in Different Sample Matrices
Using NCASI Methods 253 and Color 71.01.
The statistical difference between the two methods was evaluated through the use of F-tests and p-
values. The statistical calculations used for this evaluation utilized a one-tailed F test to determine if
the updated Method Color 71.01 was more precise than Method 253. The F-test considers the ratio of
the squares of the two sample standard deviations such that calculated F is always greater than one. If
the F-ratio is less than the critical value of F,the variances are assumed to be equal (precision of the
two methods is similar). The p-values were utilized to determine if the two methods generated
comparable color values. The F-ratios,p-values (a=0.05), and critical values for F are presented in
Table 5.2. The p-values were calculated assuming equal variances as justified by the F-test results. If
the calculated p-values are less than the selected alpha of 0.05 for a 95%confidence level, the mean
color values are not considered to be significantly different. A full report of the statistical analysis
can be found in Appendix A, Section A3, along with definitions of the statistical terms.
National Council for Air and Stream Improvement

18 Technical Bulletin No. 803
■Color-71.01 ❑Method 253
8.10
x 8•00
7.90
7.80
i 7.70
w 7.60
y 7.so
0
0. 7.40
7.30
Iagnin Mill A Mill B Mill A Mill B Mffi D
Effluent Effluent Influent Influent Receiving
Water
Sample Matrix
Figure 5.2. Comparison of Post-Filtration pH in Different Sample Matrices
Using NCASI Methods 253 and Color 71.01.
As the results indicate, a significant difference in the resultant color determinations was observed for
the influent from Mill B and the receiving water from Mill D, with higher color values reported when
using Method 253.
Table 5.2. Summary of the Statistics Comparing NCASI Methods 253
and Color 71.01 in Different Matrices
Sample Matrix F-Ratio Critical Value of F p-Value
Lignin Solution 0.098 9.27 0.572
Effluent Mill A 0.229 9.27 0.961
Effluent Mill B 0.304 9.27 0.655
Influent Mill A 0.159 9.27 0.053
Influent Mill B 1.52 9.27 0.009
Receiving Water Mill D 1.46 9.27 0.019
5.6 Inter-Laboratory Investigation of NCASI Method Color 71.01
In an effort to assess the ruggedness and precision of the updated method,an inter-laboratory study
was conducted which included industry and NCASI laboratories. A total of eight laboratories
participated in a study to determine the intra-and inter-laboratory precision of the updated color
procedure using several matrices. The samples included biologically treated effluents from Mills A
and B, influents to the treatment system from Mills A and B,portions of a prepared lignin solution, a
receiving water sample collected from the discharge stream of Mill D,and a platinum cobalt color
standard. Mill personnel collected the influent(24-hour composites),effluent,and receiving water
(grab) samples into one-gallon amber glass bottles with Teflon"l-lined screw caps. NCASI received
the iced samples from the mills via overnight delivery.
To minimize the potential for bias,the samples were thoroughly mixed and split into separate 100 mL
portions. This step ensured that any differences in study results could be attributed to analytical
method variables and not to sampling or compositing procedures. The samples were then shipped on
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Technical Bulletin No. 803 19
ice via overnight carrier to the eight participating laboratories along with a study plan, analytical
procedures, and a data sheet(Appendix Q. The participating labs received the samples blind, along
with a calibration check standard prepared at a color value of 125 PCU. The check standard was
prepared by diluting a 500 PCU color standard using Bamsteadrm deionized water. The color units
and percent recoveries of the QA/QC check standard analyses are presented in Table 5.3. Each
laboratory also received replicates of the various matrix types so that the intra-laboratory precision
could be assessed. The laboratories were asked to analyze the samples on the date of receipt
according to the procedure and study plan presented in Appendix-C, and report the data on the data
sheet also included in the appendix.
The inter-laboratory data were evaluated statistically using Youden matched pairs of similar matrices
(Youden and Steiner 1975). The sample results are summarized in Table 5.4. The codes Ll through
L8 identify the participating laboratories, and each matrix type is designated by a letter code. The
table also includes information on the light path length of the cells used at each laboratory, although
the use of a specific light path length was not part of the study plan.
- Table 5.3. Summary of the True Color Values and Percent Recoveries
for the QA/QC 125 PCU Standard
Laboratory Code Color Units (PCU) Recovery (%)
Ll 106 85
L2 145a 116
L3 106 85
L4 113 90
L5 129 103
L6 123 98
L7 118 94
L8 103" 82
Average 118 94
Standard Deviation 13.2 10.6
Relative Standard Deviation(%) 11.2 11.3
a Although this value is high in relationship to the other laboratory results,it was not an outlier based on
Grubb or Dixon tests.
s Although this value is low in relationship to the other laboratory results,it was not an outlier based on Grubb
or Dixon tests.
The Youden matched pair analyses were initiated by preparing an xy plot of the data points for each
sample type using one pair of data for the x-axis and one pair of data for the y-axis. Appendix D,
Figures D 1 through D6,present the sample plots for each matrix. This analysis is conducted in order
to assess bias in the data and identify outlying data points. The average value obtained for the y-axis
data is represented by the horizontal line and the average of the data plotted on the x-axis is represent
by the vertical line. Random variability is demonstrated if the data are evenly distributed within the
four quadrants around the intersection of the x and y averages. The closer the data points are to the
intersection,the better the analytical precision. High and low laboratory bias is demonstrated when
the sample results from a given laboratory are at an extreme along the 45-degree line of the graph.
Points distant from the 45-degree line indicate a lack of agreement between results from the same
laboratory. Careful review of these plots indicate that although the majority of data points lie near
the intersection of the average values,some laboratory bias exists. Examination of the plots indicate
that Labs 2 and 3 were biased high, while Lab 4 was biased low. Cochran's, Grubb's, and Dixon's
outlier tests were utilized to determined the significance of these laboratory biases (AOAC 1989).
National Council for Air and Stream Improvement

20 Technical Bulletin No. 803
Table 5.4. Inter-laboratory Study: Summary of Results (Color Values Reported in PCU)
Laboratory Code: Ll L2 L3 1-4 L5 L6 L7 L8
Light Path 10 mm 10 mm 10 mm 10 mm 28 mm 100 mm 16 mm 10 mm
Length a: (sq.)
Sample Type
Lignin 1 49 90 140 46 59 57 75 43
Lignin 2 49 70 105 51 54 58 68 43
Effluent Mill A-1 509 695 745 454 646 605 515 509
Effluent Mill A-2 516 745 830 440 621 607 515 496
Effluent Mill B-1 162 290 305 147 199 194 195 153
Effluent Mill B-2 159 295 260 141 196 173 168 143
Influent Mill A-I 712 1040 970 556 811 746 640 623
Influent Mill A-2 686 990 1000 533 771 678 638 589
Influent Mill B-1 89 205 210 83 154 141 110 96
Influent Mill B-2 89 205 300 87 132 144 168 89
RW"Mill D-I 136 220 180 112 169 149 180 116
RW"Mill D-2 132 215 240 113 167 165 140 116
a All cells utilized in this study were cylindrical unless otherwise noted.
" RW is receiving water.
Dixon's test evaluates the occasional aberrant average value. Cochran's test is applied to test for the
removal of laboratories showing significantly greater intra-laboratory variability than the other
laboratories in the study for a given matrix type. Grubb's test is applied to assess whether a
laboratory has an extreme average value. If no outliers are determined using a single Grubb's test,
which is a determination of a single laboratory with high or low bias, then a double Grubb's test is
performed to determine if the outliers are masked by the presence of both high and low extremes. Of
the five pairs of data plotted,Lab 3 consistently fell outside the range of averages using the Dixon's
test. These results may be due to the lack of experience of the analyst performing the measurements
at this laboratory, since it was the analyst's first experience conducting measurements of color in pulp
mill matrices. In addition,Lab 2 data fell outside the range of averages using the Dixon's tests for the
Mill B effluent,Mill A influent, and Mill B receiving water samples.
Once the outliers were removed, statistical calculations were performed to assess the intra-laboratory
(repeatability,r) and inter-laboratory (reproducibility,R)precision of the method. The intra-
laboratory repeatability is a measure of the closeness of agreement between successive results
obtained with the same method on identical matrices under the same conditions and is calculated
based on the sum of squares of the laboratory ranges between the two duplicate samples (refer to
Appendix A for definitions). The inter-laboratory reproducibility is the variation arising from
different operators in different laboratories using different apparatus and is composed of the total
within-sample variation. It is calculated by combining the between-laboratory variation,the
laboratory-sample interaction,and the between-replicate variance(refer to Appendix A for
definitions). Table 5.5 lists the results for the Youden pair analyses, which includes the mean of the
laboratory averages,the repeatability and reproducibility standard deviations,and the repeatability
and reproducibility relative standard deviations. The results indicated that the intra-laboratory
precision (agreement of replicate values within a particular laboratory) of the method ranged from 2.3
to 13.8%. The inter-laboratory precision(agreement in values among laboratories)of the method
ranged from 13.1 to 35%. The influent Mill B samples (35%) and the lignin stock solutions (24%)
resulted in the largest variations.
National Council for Air and Stream Improvement

Technical Bulletin No. 803 21
Table 5.5. Results of the Inter-laboratory Study Youden Pair Analyses
Receiving
Lignin Effluent Effluent Influent Influent Water
Parameter Solution Mill A Mill B Mill A Mill B Mill D
Number of labs 7a 73 6b 6 b 7a 6
Mean of lab averages 58.0 562 169 665 128 141
s (r)repeatability standard 5.8 17.2 7.1 15.4 17.6 13.2
deviation
s (R) reproducibility standard 13.9 95.2 22.1 87.7 44.8 25.6
deviation
RSD (r)repeatability relative 10.0 3.1 4.2 2.3 13.8 9.3
standard deviation
RSD (R)reproducibility 24.0 16.9 13.1 13.2 35.0 18.1
relative standard deviation
a Lab 3 was an outlier and was removed prior to completing the calculations in this table.
b Labs 2 and 3 were outliers and were removed prior to completing the calculations in this table.
6.0 SUMMARY AND CONCLUSIONS
The purpose of this study was to evaluate and optimize NCASI Method 253 when used on
biologically treated effluents and treatment plant influents from low color pulp mill effluents. This
work has resulted in a well-defined and documented method for the measurement of true color which
includes quality control and quality assurance criteria. Appendix B contains the updated color
method,NCASI Method Color 71.01,that was prepared as a result of this work.
The selection of a wavelength to measure sample absorbance influences the accuracy and precision of
color measurements; therefore,the wavelength of 465 ilm used in NCASI Method 253 was verified in
current sample matrices. Optimum overlap of absorbance curves for a 200 platinum cobalt standard,
wastewater treatment system influent, and biologically treated effluent occurred in the range of 460 to
470 tlm,indicating that the use of a wavelength of 465 ilm was valid in modem mill effluents.
The color of pulp mill effluents is highly pH dependent, and the pH adjustment procedure included in
Method 253 sometimes resulted in less than optimum stability of pH during the analytical procedure.
As sample pH increases, the measured absorbance value increases,resulting in higher color values.
One objective of updating Method 253 was to examine techniques to stabilize sample pH. Several
buffering systems were examined,including a phosphate buffer solution, a dry phosphate buffer
capsule,and a biological buffer solution. The buffer capsule(dibasic sodium phosphate and
monobasic potassium phosphate,pH 7.0) stabilized the sample pH most effectively. The buffer
capsule stabilized the sample pH at 7.6±0.05 for the duration of a 24-hour experiment. In addition,it
is a convenient technique for pH stabilization that does not contribute to sample dilution.
Experiments to investigate methods for the removal of sample turbidity while minimizing effects on
true color were also conducted. Pre-filtration of samples with a 1 µm glass fiber filter was
determined to help reduce problems associated with clogging of the 0.8 µm membrane filter.
Experiments to assess turbidity removal using centrifugation vs.filtration indicate that filtration using
a 0.8 µm membrane filter removed a larger percentage of the turbidity in wastewater samples. These
experiments also indicate that higher color values were determined in centrifuged samples.
Successive filtration experiments using a range of filter porosities between 1.0 and 0.22 µm indicate
that the majority of sample turbidity,94 to 99.4%,was removed using the 0.8 µm membrane filter. In
addition,experiments to investigate the removal of turbidity agents including precipitated calcium
National Council for Air and Stream Improvement

22 Technical Bulletin No. 803
carbonate, titanium dioxide,lime mud,fiber, and green liquor dregs indicate that 92 to 98% of the
turbidity was removed using the 0.8 µm membrane filter for each agent except titanium dioxide (23 to
25%removal). Therefore, the 0.8 µm membrane filter was verified as an effective method for the
removal of turbidity in modern pulp mill wastewater samples. Several types of 0.8 µm membrane
filters are available commercially. A comparison of color values determined using three different
types of 0.8 µm membrane filters did not reveal a statistically significant impact of filter type on
measured color value.
The volume of sample selected for filtration was investigated. It was determined that when using the
techniques recommended in the updated method, sample volume did not effect the overall color value
determined. Therefore, a 50 mL sample volume was chosen for ease of manipulation and filtering.
Samples from five different mills were used to investigate the effect of the light path length on the
resultant color value. It was demonstrated that color values varied by a relative standard deviation of
less than 6% when measured using light path lengths of 10, 20,25, 50, and 100 mm.
Method ruggedness,precision, and accuracy of the updated method (Color 71.01) were determined at
the single laboratory level. Instrument precision,expressed as the percent relative standard deviation
of seven replicates of a 100 PCU color standard, was determined to be 1.4%. Precision was
calculated in both biologically treated effluents and treatment plant influents. At the single laboratory
level,the average relative percent difference in duplicate analyses for biologically treated effluents
was 2.8% (n= 12 duplicate/sample sets), and for treatment plant influents it was 7.1% (n= 12
duplicate/sample sets). Calibration curves prepared using light path lengths of 10 to 100 mm yielded
r-squared values of greater than 0.9968 for twelve different calibration curves. The average recovery
for 43 daily calibration checks was 94.9%, with a standard deviation of 6.7.
Eight laboratories participated in a multi-laboratory study to assess the ruggedness, accuracy and
precision of the updated color measurement procedure. The samples included biologically treated
effluents from Mills A and B,influents to the treatment systems from Mills A and B,portions of a
prepared lignin solution, a receiving water sample collected from the discharge stream of Mill D, and
a platinum cobalt color standard. The platinum cobalt color standard data were utilized to assess
method accuracy, and yielded an average recovery of 94% and a relative standard deviation of 11.3%.
The precision for the inter-laboratory assessment resulted in a relative standard deviation of 15% for
biologically treated effluents, 24.1% for treatment plant influents, and 18.1%for the receiving water
sample. The intra-laboratory precision(agreement of replicate values within a particular laboratory)
was also assessed during this multi-laboratory study and resulted in a relative standard deviation of
3.6% for biologically treated effluents, 8.1%for treatment plant influents, and 9.3%for the receiving
water sample.
The precision and accuracy of NCASI Method 253 was determined to be similar for effluents from
Mills A and B, a lignin solution, an influent from Mill A, and a receiving water from Mill D when
compared to the NCASI Method Color 71.01 during studies conducted at two different laboratories.
The only exception was found in an influent sample from Mill B which gave higher color values
when NCASI Method 253 was utilized.
REFERENCES
Association of Official Analytical Chemists (AOAC). 1989. Guidelines for Collaborative Study
Procedures. Journal of the Association of Official Analytical Chemists 72(4):701-4.
Ferguson,W.J.,K. I.Braunschweiger,W. R. Braunschweiger,J.R. Smith,J.J.McCormick, C. C.
Wasmann,N.P.Jarvis,D.H.Bell, and N. E. Good. 1980. Hydrogen ion buffers for biological
research. Analytical Biochemistry 104:300-10.
National Council for Air and Stream Improvement

Technical Bulletin No. 803 23
Federal Register. 1997. Volume 62,No. 123.40 CFR Parts 126 and 141. Guidelines Establishing
Test Procedures for the Analysis of Pollutants and National Primary Drinking Water Regulations;,
Flexibility in Existing Test Procedures and Streamlined Proposal of New Test Procedures;
Correction,Announcement of Meetings and Extension of Comment Period. June 26.
Hach Company. 1991. Hach Ratio Turbidimeter Model 18900-00 Manual. Loveland,CO: Hach
Company.
Ingle,J.D., and S.R. Crouch. 1988. Spectrochemical analysis.Englewood Cliffs, NJ:Prentice Hall.
Kringstad,K., and K.Lindstrom. 1984. Spent liquors from pulp bleaching. Environmental Science
and Technology 18(8):236A-48A.
National Council for Air and Stream Improvement, Inc. (NCASI). 1971. An investigation of
improved procedures for measurement of mill effluent and receiving watercolor. Technical
Bulletin No.253. Research Triangle Park,NC: National Council for Air and Stream
Improvement, Inc.
. 1981. Further investigations of the color measurement procedure to improve its utility.
NCASI Report. Research Triangle Park,NC: National Council for Air and Stream
Improvement,Inc.
Standard Methods for the Examination of Water and Wastewater. 20`h Edition. 1998.Washington,
DC: American Public Health Association. 2-1 to 2-8.
United States Environmental Protection Agency (USEPA). 1971. Color Method 110.2
(Colorimetric-Platinum Cobalt). 110.2-1 to 110.2-3.
1978. Color Method 110.1 (Colorimetric,ADMI). 110.1-1 to 110.1-3.
Youden,W.J. and E.H. Steiner. 1975. Statistical Manual of the Association of Official Analytical
Chemists. Benjamin Franklin Station,Washington,DC: Association of Official Analytical
Chemists.
National Council for Air and Stream Improvement

Technical Bulletin No. 803 At
APPENDIX A
STATISTICAL DATA
Al. DEFINITIONS AND DESCRIPTIONS OF STATISTICAL TERMS
The statistical procedures and tests utilized throughout this technical bulletin are defined as follows.
Relative Standard Deviation(RSD). A measure of the spread or dispersion of data expressed as a
percentage.
Relative Percent Difference (RPD). A measure of the spread or dispersion of a sample and
duplicate pair expressed as a percentage.
F-ratio. A ratio of the two sample set variances (i.e.,the ratios of the squares of the standard
deviations).
p-value.The probability that the difference in means is due to random variability of samples pulled
from a normal distribution.
West. A test that determines whether two means from two independent, normally distributed samples
differ.
Cochran's test. A statistical test for homogeneity of variance. The hypothesis is that the variances
across different levels are equal;if the significance levels are greater than 0.05,do not reject the
hypothesis that the variances are not different.
Grubb's test. A test that is applied to assess whether a laboratory has an extreme average value.
Dixon's test. A statistical test for assessing suspect measurements. Examines the ratio of the suspect
value minus the value nearest it and the difference between the highest and lowest measurements.
Repeatability variance(s(r)^2). Sum of the squares of the laboratory ranges divided by two times
the number of participating laboratories minus one.
Reproducibility variance (s(R)^2). The true variance between replicate determinations (60 2)plus
the true variance between laboratories (aL2).
CFO 2. Sum of squares of individual replicates minus one divided by the number of replicates times the
sum of the squares of the replicate totals, all divided by the number of participating laboratories times
the number of replicates minus one.
aO. Determined by finding the mean square of the between-laboratory variance which is
MSS=r6L2+oo2 and using the result from above(oo2),rearranging the equation and solving for
6L2.
MSL. One divided by the number of replicates times the sum of the squares of the replicate totals
minus one divided by the number of participating laboratories times the number of matrices times the
number of replicates all times the square of the grand total of the results for all replicates divided by
the number of participating laboratories minus one.
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A2 Technical Bulletin No. 803
A2. REGRESSION ANALYSIS OF THE CHANGE IN TURBIDITY VS. COLOR VALUE
Effluent Mill B
Dependent variable-Color value(PCU)
Independent variable-Change in turbidity
Parameter Estimate Standard Error t-statistic p-value
Intercept 136.2 5.8 23.7 0.0018
Slope 0.03 0.17 0.20 0.8599
Analysis of Variance
Source Sum of squares Df Mean square F-ratio p-value
Model 1.08 1 1.08 0.04 0.8599
Residual 53.7 2 26.8
Total (corr.) 54.75 3
Influent Mill C
Dependent variable-Color value(PCU)
Independent variable-Change in turbidity
Parameter Estimate Standard Error t-statistic p-value
Intercept 164.4 30.6 5.4 0.0329
Slope 0.44 0.62 0.69 0.5566
Analysis of Variance
Source Sum of squares Df Mean square F-ratio p-value
Model 57.6 1 57.6 0.49 0.5566
Residual 235.4 2 117.7
Total (corr.) 293.0 3
National Council for Air and Stream Improvement

Technical Bulletin No. 803 A3
A3. SUMMARY OF F-TEST AND T-TEST STATISTICS
Method 253 Compared to Method Color 71.01
Lignin Solution Method 253 Color 71.01
Mean 51.3 52.7
Variance 2.3 22.9
Standard Deviation 1.5 4.8
Observations 4 4
df 3 3
F 0.098
p-value of F 0.883
t -0.598
p-value of t 0.571
Effluent Mill A Method 253 Color 71.01
Mean 575 573
Variance 1144 4992
Standard Deviation 33.8 70.6
Observations 4 4
df 3 3
F 0.229
p-value of F 0.257
t 0.051
p-value of t 0.961
Effluent Mill B Method 253 Color 71.01
Mean 185 179
Variance 139 459
Standard Deviation 11.8 21.4
Observations 4 4
df 3 3
F 0.304
p-value of F 0.354
t 0.469
p-value of t 0.655
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A4 Technical Bulletin No. 803
Influent Mill A Method 253 Color 71.01
Mean 672 745
Variance 509 3201
Standard Deviation 22.6 56.6
Observations 4 4
df 3 3
F 0.159
p-value of F 0.165
t 2.40
p-value oft 0.052
Influent Mill B Method 253 Color 71.01
Mean 213 116
Variance 1601 1053
Standard Deviation 40.0 32.4
Observations 4 4
df 3 3
F 1.52
p-value of F 0.738
t 3.77
p-value oft 0.009
Receiving Water Mill Method 253 Color 71.01
D
Mean 151 125
Variance 162 ill
Standard Deviation 12.7 10.5
Observations 4 4
df 3 3
F 1.46
p-value of F 0.761
t 3.15
p-value of t 0.019
National Council for Air and Stream Improvement

Technical Bulletin No. 803 B1
APPENDIX B
NCASI METHOD COLOR 71.01
COLOR MEASUREMENT IN PULP MILL WASTEWATERS
BY SPECTROPHOTOMETRY
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B2 Technical Bulletin No. 803
Acknowledgments
This method was prepared by Diana Cook,Senior Research Chemist,and Nikki From,Research Associate,
at the NCASI West Coast Regional Center.
For more information about this method,contact:
Diana Cook Reid Miner
NCASI West Coast Regional Center NCASI
P.O.BOX 458 P.O.BOX 13318
Corvallis, OR 97339 Research Triangle Park,NC 27109-3 3 1 8
[phone] [phone]
[e-mail] [e-mail]
For information about NCASI publications,contact:
NCASI
P.O.Box 13318
Research Triangle Park,NC 27709-3318
[phone]
[e-mail]
National Council for Air and Stream Improvement,Inc.(NCASI). 1999. Methods Manual. NCASI
Method Color 71.01: color measurement in pulp mill wastewaters by spectrophotometry. Research
Triangle Park,NC:National Council for Air and Stream Improvement,Inc.
© 1999 by the National Council for Air and Stream Improvement,Inc.
NCASI's Mission
To serve the forest products industry as a center of excellence for providing technical information and
scientific research needed to achieve the industry's environmental goals.
Disclaimer
The mention of trade names or commercial products does not constitute endorsement or recommendation
for use.
This method is included in the NCASI Methods Manual as an update to NCASI Method 253. The purpose
of including this updated method in the NCASI Methods Manual is to make it known that a method
revision is under development and to solicit comments regarding the technical merit and applicability of the
revised method. Those electing to apply the method are strongly encouraged to conduct rigorous QA/QC
or validation so that the quality of the data generated can be evaluated.
National Council for Air and Stream Improvement

Technical Bulletin No. 803 B3
NCASI METHOD COLOR 71.01
COLOR MEASUREMENT IN PULP MILL WASTEWATERS
BY SPECTROPHOTOMETRY
1.0 Scope and Application
1.1 This procedure utilizes a spectrophotometer to measure the absorbance of light as
it passes through a sample. The color is determined by comparison of the
absorbance of the sample to the absorbance of colored solutions of known
concentrations. The colored solutions used in this procedure are platinum cobalt
stocks. The unit of color is the color produced by 1 mg platinum/liter in the form
of the chloroplatinate ion, or PCU.
The term "color"represents the true color of an aqueous sample from which
turbidity has been removed (1). Turbidity can cause the color value determined
for a sample to be elevated due to an increase in light scattering. In this
procedure, filtration is used to remove turbidity from the sample. The optimal
method for removing turbidity without affecting the color value determined has
not been found, but filtration using a 0.8-micron (µm) membrane filter has been
demonstrated to be effective for most pulp mill effluent samples.
The color value determined for a specific sample is pH dependent and increases
as the pH of an aqueous sample increases. Therefore, a buffer is used to stabilize
pH during the filtration and measurement process.
1.2 This method has been validated at the single and inter-laboratory level in
wastewater treatment plant influents,biologically treated effluents from kraft pulp
and paper mills, and receiving waters. Demonstration of method performance for
specific matrix types is recommended. _
1.3 The estimated method detection limit(MDL) achievable is instrument and light
path length.dependent and was found to be 4 PCU for a river water sample using a
10-mm light path length (2). The MDL determined in a kraft mill treated effluent
was found to be 7 PCU using a 10-mm light path length. These values are
provided as guidance. Due to improvements in instrumentation and changes in
matrix effects, each laboratory should establish its own MDL. The lower
instrument calibration limit (LCL) for this method is approximately 10 PCU.
Lower calibration levels can be obtained by using an increased light path length.
The concentration range used during the single and inter-laboratory method
validation was from 10 to 500 PCU. Sample values above 500 PCU may be
determined by quantitative dilution.
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B4 Technical Bulletin No. 803
2.0 Summary of Method
2.1 Biologically treated effluents and wastewater influents
Place a 50-mL aliquot of unpreserved influent (effluent) into a 100-mL beaker.
Measure the initial pH of the sample and add approximately one-half of the solid
from a pH 7 buffer capsule. Dissolve the buffer capsule completely using a
mechanical stir plate and stir bar. Add an appropriate amount of sodium
hydroxide solution (NaOH) or hydrochloric acid (HCl) to adjust the pH to 7.6
±0.05. Filter the sample through a 0.8-µm membrane filter. If the analyst cannot
filter the sample through the membrane because of significant clogging, a pre-
filtration step may be added prior to pH measurement and adjustment. To verify
pH stability, periodically measure the post-filtration pH.
2.2 Quantitative analysis
Assess the color load by measuring the absorbance of the solution in a
spectrophotometer set at a wavelength of 465 nanometers (rlm).' Calculate the
color units using the linear regression equation developed in Section 12.L
2.3 Quality assurance
Quality is assured through reproducible calibration and testing of the sample
preparation and spectrophotometer system. A method blank is analyzed with each
sample set (samples started through the process on a given day, to a maximum of
20, along with sample duplicates to ensure quality data). A complete description
of quality control procedures, calculations, and method performance criteria are
listed in Sections 9.0 and 10.
3.0 Definitions
3.1 These definitions are specific to this method, but conform to common usage as
much as possible.
3.1.1 PCU—platinum cobalt color unit
3.1.2 May—this action, activity, or procedural step is neither required nor
prohibited
3.1.3 May not—this action, activity, or procedural step is prohibited
3.1.4 Must—this action, activity, or procedural step is required
3.1.5 Should—this action, activity, or procedural step is suggested, but not
required
4.0 Interferences
4.1 Reagents, glassware, and other sample processing hardware may contribute
analytical interferences resulting in inaccurate absorbance readings. Run method
blanks initially and with each subsequent sample set to demonstrate that the
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Technical Bulletin No. 803 B5
reagents, glassware, and other sample processing hardware are free from
interferences under the conditions of the method.
4.2 Turbidity causes the measured color value to be greater than the true color value.
Therefore, it is necessary to remove turbidity in the sample prior to measuring the
sample's absorbance in a spectrophotometer. Interferences will vary considerably
from source to source, depending on the diversity of the site being sampled. This
procedure recommends the use of a 0.8-µm membrane filter to remove turbidity
prior to measuring the absorbance in the spectrophotometer. As needed,the
analyst can pre-filter the sample with a 1.0 µm glass fiber filter or use more than
one 0.8-µm membrane filter if clogging prevents the sample from readily passing
through the membrane filter.
4.3 The color value determined for a given sample is highly pH dependent. As pH
increases the color value determined for the sample also increases. Therefore,
stabilization of the pH at a given value for all measurements is required. This
procedure is conducted with the sample at a pH of 7.6 ±0.05 to maintain
consistency with standard methods currently in use.
4.4 All glassware must be clean and free of scratches. In addition, the cells used for
spectrophotometric measurement of the samples must be free of all oil or residue
that may cause interference in the absorbance measurement. It is recommended
that the same cell be utilized for the measurement of the calibration curve, daily
calibration checks,blanks, and samples.
5.0 Safety
5.1 Each chemical compound should be treated as a potential health hazard.
Exposure to these compounds should be reduced to a level protective of human
health. This method does not address all safety issues associated with its use.
The laboratory is responsible for maintaining a current awareness file of OSHA
regulations regarding the safe handling of the chemicals specified in this method.
A reference file of data handling sheets should also be made available to all
personnel involved in these analyses.
5.2 The platinum cobalt solution is corrosive and a suspected carcinogen.
Hydrochloric acid(HCl) and sodium hydroxide (NaOH) are also corrosive and
should be handled with caution. Take appropriate measures to avoid contact with
the chemicals by wearing chemical-resistant gloves, eye protection, and other
protective clothing.
5.3 As with all samples,precautions should be taken to avoid exposure to potentially
toxic, caustic, or nuisance odor compounds. Samples should be handled with
gloves and opened in a fume hood.
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B6 Technical Bulletin No. 803
6.0 Equipment and Supplies
Note: Brand names, suppliers, and pan numbers are cited for illustrative
purposes only. No endorsement is implied. Equivalent performance may be
achieved using equipment and materials other than those specified here, but
demonstration of equivalent performance that meets the requirements of this
method is the responsibility of the laboratory.
6.1 A spectrophotometer with a tungsten lamp source and a 10-r)m spectral slit width
is required. The instrument must be capable of emitting light at a selectable
wavelength of 465 rlm with an operating range of 400 to 700 r)m. Verify that the
spectrophotometer is calibrated correctly by following the directions from the
manufacturer for your specific instrument.
6.2 Do not use glassware with any star fractures, cracks, or severe scratches. All
glassware should be washed with detergent, rinsed with tap water, then rinsed
with reagent grade water prior to use.
6.3 Equipment for sample preparation
6.3.1 Filtration apparatus consisting of a flask, a vacuum source, and a filtration
holder that will accommodate a 47-min filter
6.3.2 Pasteur pipettes
6.3.3 50-mL graduated cylinder
6.3.4 TeflonTM'-coated stir bar
6.3.5 100-mL beaker
6.3.6 47-mm, 1.0-µm glass fiber filters for pre-filtration
6.3.7 47-mm, 0.8-µm membrane filters
6.4 Other apparatus
6.4.1 pH meter calibrated using a two-point calibration procedure at pH 7 and
pH 8 using the appropriate buffer solutions
6.4.2 Magnetic stirrer
6.4.3 Sample cuvettes (absorption cell) for the measurement of absorbance, cell
path length is determined by the required MDL, refer to Table 1 for the
path length specific MDLs (3)
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Technical Bulletin No. 803 B7
7.0 Reagents and Standards
7.1 Reagents
7.1.1 Metrepak pHydrion buffer capsules, or an equivalent supplier(dibasic
sodium phosphate and monobasic potassium phosphate,pH 7.0), to
stabilize sample pH
7.1.2 Organic-free reagent water in which color is not detected by this method
7.2 Standards
7.2.1 Fisher or an equivalent supplier, platinum cobalt color standard, 500 PCU
stock
7.2.2 If a reliable source of platinum cobalt color standard is not available,
prepare a solution of potassium chloroplatinate. Dissolve 1.246 g of
potassium hexachloroplatinate, K2PtC16 (Aldrich or an equivalent
supplier), and 1.00 g of crystallized cobalt (II) chloride hexahydrate,
COC12.6 HZO (Aldrich or an equivalent supplier), in a portion of organic
free reagent water containing 100 mL of concentrated HCL Dilute this
solution with distilled water to the desired color value. For example,
dilution to 1000 mL will provide a standard with a color value of
500 PCU. Dilution to 500 mL will provide a standard with a color value
of 1000 PCU.
7.2.3 Prepare a five-point calibration curve encompassing the sample
concentration range. Prepare a calibration curve by diluting 5, 10, 20, and
50 mL of 500 color unit stock solution of platinum cobalt in 100 mL of
deionized water. Include the absorbance measurement of the 500 color
unit stock solution of platinum cobalt in the curve. The prepared
calibration standards will have color units of 25, 50, 100,250, and 500. It
is necessary to prepare a calibration curve that brackets the expected
values of color in the samples.
7.2.4 Stock solutions of the color standards do not need to be refrigerated,but
care should be taken to protect the standards from evaporation, light, and
contamination when not in use. Remember that the color standard
solutions have pHs less than 2.0 and should be handled with care. Stock
solutions of all standards should be checked for signs of concentration or
formation of precipitates prior to the preparation of calibration or
performance test standards. Replace the stock solutions if a change in
concentration is indicated by the inability to meet the criteria specified in
Sections 9.2 and 10.3.
7.3 Reagents for sample preservation and pH adjustment
7.3.1 Sodium hydroxide, ACS reagent grade, is used to adjust sample pH during
processing. Prepare a 20% solution by adding 20 grams of sodium
hydroxide pellets very slowly to 100 mL of reagent grade water using a
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B8 Technical Bulletin No. 803
stir bar and stir plate. Because this reaction is exothermic, take care that
the heat generated by the addition of the NaOH to the water does not break
the glassware.
7.3.2 Hydrochloric Acid, ACS reagent grade, is used to adjust sample pH during
processing. Prepare a 10% solution by adding 10 mL of concentrated HCl
to approximately 85 mL of reagent grade water using a stir bar and stir
plate. Bring the volume to 100 mL once the heat has dissipated.
8.0 Sample Collection, Preservation, and Storage
8.1 Sample collection
Collect grab or composite samples using clean sampling containers that are free
from contaminants which may interfere with the analyses. Composite samples
should be refrigerated during the sampling period. The color determination
should be made as soon as possible following sample collection. An assessment
of sample stability should be done on a matrix specific basis since biological
changes which can occur during storage may affect the color and alter the pH of
the sample.
8.2 Sample preservation
Samples are not preserved prior to analysis, as a change in pH can greatly affect
the resulting color determination. Samples should be refrigerated prior to
analyses (4°C). Sample refrigeration should occur as soon as possible after
sample collection.
9.0 Quality Control
9.1 Each laboratory that uses this method should operate a formal Quality Assurance
Program. The minimum requirements of this program consist of an initial
demonstration of laboratory capability, and ongoing analyses of standards and
blanks as a test of continued performance. Laboratory performance is compared
to established performance criteria to determine if the results of analyses meet the
performance characteristics of the method.
9.2 Spectrophotometer performance and calibration verification
9.2.1 Fill the sample cuvette with reagent grade water and place it in the
spectrophotometer. Adjust the absorbance reading to zero..Verify zero
after every four to six samples using the same process.
9.2.2 Determine that the spectrophotometer system is operating within
acceptable parameters by conducting a calibration check before each set of
analyses (samples started through the measurement process on a given
day). The calibration check involves reanalyzing one of the standard
calibration solutions used to prepare the calibration curve (Sections 7.2.3
and 10.3). The percent recovery determined for the calibration check
should be within the calculated warning limits (Section 17, Table 2). The
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Technical Bulletin No. 803 B9
color determination may be sensitive to spectrophotometer and cell
conditions such as dirty glassware. If the calibration check fails to meet
the acceptance criterion, locate a new sample cuvette or perform
appropriate maintenance and reanalyze the calibration check sample. If
this fails to correct the calibration verification difficulties, the calibration
curve should be re-prepared and analyzed.
9.2.3 Verify that the spectrophotometer is calibrated properly by periodically
measuring an independent color standard check sample. If all calibration
checks and adjustments fail to correct the problem, calibrate the
instrument electronically. Electronically calibrate the instrument by fast
selecting the transmittance option and setting the wavelength to 450 Tlm.
With'the 100% T/Zero control, set the display to read 100.0, insert an
occluder in the sample well, and close the cover. Adjust the %T
adjustment knob to read exactly 0.0 and remove the occluder.
9.3 Frequency
One sample per analytical batch of no more than twenty samples of similar matrix
type should be allocated for quality control (i.e., duplicate analyses). A
representative sample from each new or untested source or sample matrix should
be treated as a quality control sample.
9.4 Blanks
9.4.1 Demonstrate that the analytical system is free of color by preparing and
analyzing a blank with each sample set (20 samples or less). Prepare a
method blank using the same procedure outlined in Section 11.0 utilizing
reagent grade water for the sample.
9.4.2 If color is found in the blank at a value greater than 10% of the method
detection limit or the lowest calibration limit, analysis of samples is halted
until the source of contamination is eliminated and a blank shows no
evidence of contamination at this level.
9.5 Sample and duplicate precision
Analyze a sample and duplicate for each matrix type with each set of samples to
assess the precision of the analyses. Calculate the relative percent difference
(RPD) in color for each sample and duplicate pair using Equation 1. The
calculated RPD should be less than 14%.
Equation 1
Relative Percent Difference=(Highest Color Value —Lowest Color Value) x 100
Average Color Value of the sample and duplicate
A summary of the precision determined in the single laboratory validation is
provided in Section 17, Table 3 for treatment system influent and biologically
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B10 Technical Bulletin No. 803
treated effluent samples. The average relative standard deviation for the single
laboratory precision was 2.8% in biologically treated effluents and 7.1% in
treatment plant influents. A summary of the accuracy and precision determined
during an inter-laboratory validation is provided in Section 17, Tables 4 and 5 for
treatment system influent,biologically treated effluent, and a receiving water
sample.
9.6 Field replicates and field spikes
Depending on specific program requirements, field replicates may be required to
assess the precision and accuracy of the sampling and sample transporting
techniques.
10.0 Calibration and Standardization
10.1 Zero the spectrophotometer (Section 9.2.1) and establish the operating conditions
outlined below. Use the same operating conditions to analyze all samples, blanks,
calibration curves, and calibration verification samples.
10.2 Quantitation
10.2.1 Analyze the calibration standards (Section 7.2.3) at a wavelength of
465 Tim using the procedure described in Section 11.2.3. Construct a
calibration curve by plotting the absorbances and the color units of the
calibration curve points. An example of a calibration curve plot is located
in Section 17, Figure 1.
10.2.2 If the r-squared value determined for the curve is 0.991 or greater, the
calibration curve is assumed to be linear and acceptable. The linear
equation determined from the curve can then be used to calculate sample
color(Section 12.1). If the curve is not linear, evaluate the problem,
undertake the appropriate remedial action, and reanalyze the calibration
curve solutions. If remedial actions and reanalysis fail to produce an r-
squared value of at least 0.991,prepare new calibration curve solutions
and analyze them. The statistics for calibration curve linearity determined
during a single laboratory validation of this method are included in
Section 17, Table 6.
10.3 Verify calibration prior to the analysis of each set of samples (Sections 9.2).
Analyze one of the calibration standards (Section 7.2.3) prior to the analysis of
each set of samples. It is recommended that the selected calibration standard vary
over time in order to verify the calibration of the instrument over the full
calibration range of the method. Recalibrate if the percent recovery for the color
standard of the analyzed calibration solution is outside of the warning criteria
(Table 2).
10.4 Process a blank with the curve to confirm that the glassware, sample cuvette,
reagents, and other components are free from contamination. Prepare the blank
with deionized water using the procedure for the preparation of the samples
(Section 11).
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Technical Bulletin No. 803 B11
10.5 Demonstrate that color is detectable at the minimum level using the lowest level
calibration curve solution and the same path length of the sample cuvette that will
be used to analyze all curve points, calibration verifications, and samples.
11.0 Procedure
This section includes the procedures used to adjust pH, and filter the treatment plant
influent and biologically treated effluent samples. The pH adjustment and filtering
procedures are used for all types of samples and method blanks.
11.1 pH adjustment of the sample
11.1.1 Remove the sample from the refrigerator and allow the sample to come to
room temperature. Calibrate the pH meter using a two-point calibration
with pH 7 and pH 8 buffer solutions. Shake the sample to ensure
homogeneity and immediately measure 50 mL of the sample using a 50-
mL graduated cylinder. For method blanks, measure 50 mL of reagent
grade water.
11.1.2 Measure and record the sample pH (initial pH). Gently open a pH 7
Metripak pHydrion (or equivalent) buffer capsule and add approximately
one-half of the contents (powder only) to the sample. Stir until all of the
buffer has dissolved. Reserve the remaining half of the buffer for the next
sample. Adjust the sample pH to 7.6±0.05 by adding a small volume of
sodium hydroxide solution (preferably 20%) dropwise. If the pH is
adjusted slightly too high, hydrochloric acid (preferably 10%) may be
added dropwise to readjust the sample pH. The sample aliquot must be
discarded and re-prepared if the sample volume changes by more than 1%
before the pH is within the desired range. Differing strength acid and/or
base solutions may be used to meet this criteria. Record the adjusted pH.
11.1.3 Assemble an aspiration-type filtering apparatus and pre-wet a 0.8-µm
membrane filter with approximately 1 mL of deionized and/or distilled
water on each side of the membrane. Gently shake off the excess water,
place the filter onto the filter support, secure the filter holder/funnel in
place, turn the aspirator on, and slowly add the sample. A rapid decline in
the rate of flow through the membrane or foam coming off the membrane
filter, can indicate filter plugging. If the filter plugs, immediately replace
the filter with a new filter pre-wet with deionized and/or distilled water,
and continue filtering the remaining sample.
11.1.4 If filtration through the 0.8-µm membrane filter is excessively difficult,
the 50 mL of sample can be pre-filtered through a 1.0-µm glass fiber filter
prior to sample manipulation. Transfer the sample filtrate to a 100-mL
beaker equipped with a Teflon stir bar. Place the beaker on a mechanical
stir plate and gently stir the sample. Buffer, adjust pH, and filter through a
0.8-µm membrane filter as described in Sections 11.1.2 and 11.1.3.
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B12 Technical Bulletin No. 803
11.2 Spectrophotometer analysis
11.2.1 The spectrophotometer conditions should be set according to the criteria
described in Section 9.2.3.
11.2.2 Perform the calibration verification as outlined in Section 9.2.2.
11.2.3 Verify that the spectrophotometer is zeroed (Section 9.2.1). Rinse the cell
with a small amount of the filtered sample. Discard the rinse. Transfer
enough of the filtered samples to the sample cuvette, filling to the
reference line. Measure and record the absorbance at 46511m and discard
the sample. Rinse the cell thoroughly with deionized and/or distilled
water. Periodically verify that the spectrophotometer is zeroed.
12.0 Data Analysis and Calculations
12.1 Quantitation
12.1.1 The linear regression equation from the calibration curve (Section 10.2) is
used to calculate the corresponding color value of the samples. Calculate
the color value in the sample using Equation 2.
Equation 2
y=ntx+b
where:
y is the absorbance
m is the slope
b is the y-intercept
x is the calculated color value
Calculate the color units for each sample by utilizing the measured
absorbance value and the linear equation derived from the calibration
curve (Section 10.2).
12.1.2 The calibration curve slope and y-intercept will vary depending on the
light path length of the sample cuvette used in each different
spectrophotometer. Therefore it is important to use the same light path
length for all measurements. The following is an example calculation
from a calibration curve prepared in one laboratory.
Example Calculation:
Absorbance measured for the sample (y) 0.039
Equation y =0.0003x +0.0016
x= y-0.0016
0.0003
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Technical Bulletin No. 803 B13
Substitution x = 0.039 - 0.0016
0.0003
Calculated Color Units (x) x = 125 PCU
12.2 Data review requirements .
12.2.1 Review the data to assess the accuracy and precision of the determined
color value, spectrophotometer problems, interferences, and bias using the
guidance provided in Section 9.0 and 10.0. Correct any problems prior to
reporting the analytical results.
12.2.2 Assess the need for sample dilutions. The procedure for conducting
sample dilutions and reanalysis is described in Section 12.3.
12.2.3 Resolve inconsistencies between duplicates as necessary.
12.2.4 If review of the data shows any problems which could affect subsequent
analyses, discontinue the analyses until the problems are resolved.
12.3 Results outside the calibration range
If the calculated color value exceeds the highest color calibration point, dilute an
aliquot of the sample with reagent grade water prior to sample processing to bring
the concentration within the calibration range of the method and continue the
sample preparation process from Section 11.
13.0 Method Performance
Single laboratory performance for this method is detailed in Section 17,Tables 2,
3, and 6. Acceptance criteria were established from an inter-laboratory study
using the draft method. The data from this study are given in Tables 4 and 5.
14.0 Pollution Prevention
Pollution prevention approaches have not been evaluated for this method.
15.0 Waste Management
15.1 It is the laboratory's responsibility to comply with all federal, state, and local
regulations governing waste management,particularly the hazardous waste
identification rules and land disposal restrictions, and to protect the air, water, and
land by minimizing and controlling releases from fume hoods and bench
operations. Compliance with all sewage discharge permits and regulations is also
required.
15.2 Instructions for sample and waste handling and disposal
15.2.1 Dispose of all samples as required by federal, state and local regulations.
15.2.2 Neutralize the sodium hydroxide solution and pour it down the drain with
copious amounts of water.
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B14 Technical Bulletin No. 803
15.2.3 Neutralize the calibration standard solutions to pH 7 and pour the aqueous
portion of the extracted sample aliquot down the drain with copious
amounts of water.
15.3 For further information on waste management, the Environmental Protection
Agency suggests you consult The Waste Management Manual for Laboratory
Personnel, and Less is Better: Laboratory Chemical Management for Waste
Reduction. Both are available from the American Chemical Society's Department
of Government Relations and Science Policy, 1155 16th Street NW,Washington,
DC, 20036.
16.0 References
1. Standard Methods for the Examination of Water and Wastewater, 20`h Edition,
American Public Health Association, Washington, DC, 1998, 2-1 to 2-8.
2. Federal Register, "Appendix B to Part 136-Definition and procedure for the
determination of the method detection limit-revision 1.11."Vol. 49, No. 209.
October 26, 1984.
3. National Council for Air and Stream Improvement, Inc. (NCASI). 1971. An
investigation of improved procedures for measurement of mill effluent and
receiving water color. Technical Bulletin No. 253. Research Triangle Park, NC:
National Council for Air and Stream Improvement, Inc.
17.0 Tables, Diagrams, Flowcharts, and Validation Data
Table 1. Minimum Detectable Color for Various Light Path Length Sample Cuvettes
Sample Cuvette Light Path Length Minimum Detectable Color Units
30 1
20 5
10 7a
5 10
1 25
a Determined using a treated effluent from a kraft mill.
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Table 2. Daily Calibration Verification Criteria
Average Standard Warning Action Limits Color Unit Range
Recovery'(%) Deviation Limits`(%) M (PCU)
94.9 6.7 81 - 108 75 - 115 10 - 500
a Average recovery for 47 daily calibration checks.
b Standard deviation of the recoveries for 47 daily calibration checks.
e Average recovery plus or minus two times the standard deviation.
d Average recovery plus or minus three times the standard deviation.
Table 3. Single Laboratory Precision: NCASI Color-71.01
Sample Type' Range RPDb Average RPD`
Effluent 0.4 - 14.1% 2.8%
Influent` 0.1 - 13.2% 7.1%
a Precision of the target analytes native to treatment system influents and
biologically treated effluents.
b Range of relative percent differences observed between a sample and a duplicate.
e Pooled average relative percent difference for all sample and duplicate pairs
analyzed.
d Range and average RDP for 12 duplicate pairs.
e Range and average RDP for 12 duplicate pairs.
Table 4. Inter-Laboratory Accuracya
Average Percent Standard Relative Standard
Recovery Deviation Deviation (%)
94 10.6 11.3
a Summary of the percent recoveries for a 125 PCU color standard analyzed by eight
different laboratories using eight different spectrophotometers.
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B16 Technical Bulletin No. 803
Table 5. Results of an Inter-Laboratory Study Youden Pair Analyses
to Assess Intra- and Inter-Laboratory Precision
Receiving
Lignin Effluent Effluent Influent Influent Water
Parameter Solution Mill A Mill B Mill A Mill B Mill D
Number of Labs 7 7 6 6 7 6
Mean of Lab Averages 58.0 562 169 665 128 141
s( r) repeatability 5.8 17.2 7.1 15.4 17.6 , 13.2
standard deviation
s( R ) reproducibility 13.9 95.2 22.1 87.7 44.8 25.6
standard deviation
RSD (r)repeatability 10.0 3.1 4.2 2.3 13.8 9.3
relative standard
deviation'
RSD ( R )reproducibility 24.0 16.9 13.1 13.2 35.0 18.1
relative standard
deviation
a Infra-laboratory(repeatability)precision of the method. _
b Inter-laboratory(reproducibility)precision of the method.
Table 6. Calibration Curve Linearity
Linear Equation y=mx+b R-squared Light Path Length (mm)
y= 0.0153x-0.0108 0.9981 10
y= 0.0003x + 0.0052 0.9968 10
y=0.0003x + 0.0016 0.9999 10
y=0.0003x + 0.0010 0.9997 10
y= 0.0005x + 0.0014 0.9999 20
y = 0.0003x + 0.0004 1.0000 10
y= 0.0005x + 0.0004 0.9999 20
y= 0.0003x + 0.0003 0.9999 10
y= 0.0003x-0.0030 1.0000 10
y=0.0005x+ 0.0028 0.9988 20
y=0.0006x-0.0004 0.9999 25
y= 0.0014x-0.0003 1.0000 50
y=0.0027x+ 0.0018 1.0000 100
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Technical Bulletin No. 803 B17
0.16
0.14
0.12
$ 0.1
m
a 0.06
0
N
a 0.06
0.04
0.02 y=0.0003x+0.0016
F?=0.9999
0
0 100 200 300 400 500 600
Color Units
Figure 1. Typical Calibration Curve.
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Technical Bulletin No. 803 C1
APPENDIX C
INTER-LABORATORY STUDY PLAN,PROCEDURE,AND DATA SHEET
1.0 SCOPE
This study is intended to evaluate the precision and accuracy of an updated color method when
applied to pulp mill effluents. The following sections describe the sample collection, analysis
requirements, and data reporting requirements for the study.
2.0 SAMPLE COLLECTION,STORAGE,AND SHIPMENT
Grab samples of pulp mill treatment system influents and final effluents will be collected from two
kraft mills equipped with secondary biological treatment. Sample matrices will represent mills
pulping hardwood and softwood, utilizing oxygen delignification and high chlorine dioxide
substitution. In addition to the above samples,a receiving water sample will also be assessed. The
samples will be collected and shipped via overnight FedEx on ice to the NCASI West Coast Regional
Center where they will be homogenized and split into sample containers for shipment to the
participating laboratories. In addition to the effluent and influent samples,a color reference material
solution and platinum cobalt standard solution (color standard solution)will also be included in the
shipment. All samples will be unpreserved and should be stored at 4°C until analyzed. Sampling will
be scheduled to ensure sample shipment to each of the participating labs on the same day (Target
Date:February 17). Upon receipt,the laboratory must maintain the samples at 0 to 4°C and analyze
for color within 24 hours using the NCASI Updated Color Measurement Procedure(see attached).
A total of twelve samples and one color solution check standard will be sent to each laboratory. For
those laboratories that do not routinely measure color,a set of calibration curve solutions will also be
included in order for the lab to measure a standard curve prior to sample analyses.
3.0 SAMPLE ANALYSIS REQUIREMENTS
Each sample matrix will be analyzed for color using the attached NCASI Updated Color
Measurement Procedure. Since the objective of this study is to compare the results obtained using the
procedure;it is important that the laboratory strictly adhere to the method requirements. These
requirements are clearly defined in the attached procedure.
3.1 Method Requirements
All instruments should be zeroed using reagent grade water prior to standard and sample readings.
The calibration check standard(Bottle 1) should be.read prior to the samples. Each sample should be
measured using the attached procedure. Please provide the information specified on the attached data
sheet for each sample measured.
3.2 Data Deliverables
Complete the attached NCASI Color Measurement Study Data Sheet with the information requested
and return it to our laboratory in the enclosed envelope. We realize that some laboratories utilize
spectrophotometers with software programs that do not provide the option of viewing the calibration
curve equation. If possible,we request that you provide NCASI with the absorbance readings for the
calibration points measured. If this is not an option,leave this portion of the sheet blank. We also
recognize that you may only be able to provide color units for samples A through J,but request that
you also include the measured absorbance when possible. It would be helpful to include any
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observations that you feel may have had an effect on your results (condition of cells,instrument
function, clogging of filters, etc.) in the comment section.
3.3 Data Evaluation
The data will be evaluated for the following information:
• Completeness of the data sheet,including all data deliverables requested
• Correct reporting units and significant figures
• Results for the calibration check standard
• Results for the average concentration, standard deviation,and relative standard deviation
for each sample matrix analyzed by the procedure
• Inter-and intra-laboratory precision using Youden pair analyses
• Method precision using ANOVA statistics
3.4 Report of Findings
The analytical results and statistical evaluation will be summarized in a report. Codes will be used to
identify results associated with each lab. The names of the participating labs will not be identified.
This study is not intended to endorse or verify a laboratory,but rather to evaluate the inter-and intra-
laboratory precision using the updated color procedure. Participating laboratories will be provided
with a final copy of the report when it is completed.
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Technical Bulletin No. 803 C3
NCASI UPDATED COLOR MEASUREMENT PROCEDURE
1.0 GENERAL DISCUSSION
This procedure utilizes a spectrophotometer to measure the absorbance of light as it passes through a
sample. The color is determined by comparison of the sample to colored solutions of known
concentrations. The color solutions used in this procedure are platinum cobalt stocks. The unit of
color is the color produced by 1 mg platinum/liter in the form of the chloroplatinate ion, PCU.
The term"color"represents the true color of an aqueous sample from which turbidity has been
removed. Turbidity can cause the color value determined for a sample to be elevated due to an
increase in light scattering. In this procedure,filtration is used to remove the turbidity in the sample
which may interfere with the determination of color. The optimal method for removing turbidity
without affecting the color value determined has not been found,but filtration using a 0.8 µm
membrane filter has been demonstrated to be effective for most pulp mill effluent samples.
The color value determined for a specific sample is pH dependent and increases as the pH of the
aqueous sample increases. Therefore,a buffer is used to stabilize the pH during the measurement
process.
2.0 EQUIPMENT AND SUPPLIES
2.1 Equipment
• Spectrophotometer with a tungsten lamp source and 10 gm spectral slit width;the operating
range should include 400 to 700 Tlm and the instrument should be capable of emitting light
at a selectable wavelength of 465 rlm
• pH meter
• Mechanical stir plate
• TeflonTm stir bar
• Filtration system that will accommodate a 47 min filter
• Pasteur pipettes
• 50-mL graduated cylinder
• 100-mL beaker
2.2 Supplies provided by NCASI in the sample kit
• 47 mm, 1.0 µm glass fiber filters from Gelman for prefiltration
• 47 mm,0.8 µm membrane filters from Nucleopore,Membra-Fil
• pH 7 buffer capsules to stabilize sample pH
• Color standard calibration check solution
• Set of calibration standard stock solutions(if your lab requested them)
2.3 Reagents laboratories will need to supply
• Sodium hydroxide solution(preferably 20%,but 10% may be sufficient)
• Hydrochloric acid(preferably 4%,but a more dilute solution may be sufficient)
3.0 CALIBRATION STANDARDS
The calibration curve standards were prepared by making dilutions of a 500 color unit stock solution
of platinum cobalt. The prepared calibration standards have color units of 10,25, 50, 100,250,and
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500 PCIJ. Refrigeration of the calibration standard solutions is not necessary,but care should be
taken to protect the standards from evaporation and contamination when not in use.
4.0 CALIBRATION CURVE
4.1 All calibration standard and sample measurements must be conducted with the
spectrophotometer set at a wavelength of 465 Tlm.
4.2 Make sure that the cell to be used is clean and free of scratches, oils, and/or dirt. It is
recommended that the cell be placed in the spectrophotometer in the same position for each
reading. This can be accomplished by orienting a mark on the tube in the same position for
each reading. Allow the spectrophotometer to warm up as recommended in the instrument
manual. Zero the spectrophotometer using deionized and/or distilled water.
4.3 Rinse the cell with a small amount of the color calibration standard to be measured. Discard
this rinse and transfer a portion of the color calibration standard to the cell. Measure the
absorbance of the sample in the spectrophotometer and record the reading. Repeat this
process for each of the six calibration standards.
4.4 Plot the absorbance vs. the color value of the six calibration standards and fit the curve using
a linear regression model. Record the R-squared value(correlation coefficient) and the
equation on the data sheet. The curve is considered linear if the correlation coefficient is
greater than or equal to 0.991. If the curve does not meet this criteria,the procedure should
be repeated until this criteria is met.
4.5 The pH of the calibration stock solutions is below 2;therefore these solutions should be
neutralized prior to disposal.
5.0 MEASUREMENT OF COLOR STANDARD CALIBRATION CHECK
5.1 Make sure that the cell to be used is clean and free of scratches,oils, and/or dirt. Allow the
spectrophotometer to warm up as recommended in the instrument manual. Zero the
spectrophotometer using deionized and/or distilled water.
5.2 Rinse the cell with a small amount of the color standard calibration check(Bottle#1)to be
measured. Discard this rinse and transfer a portion of the color standard calibration check to
the cell. Measure the absorbance of the sample in the spectrophotometer and record the
reading. Calculate the color value of the color standard calibration check using the process
described in Section 7.0. Record the value on the data sheet.
6.0 MEASUREMENT OF SAMPLES
6.1 Remove the sample bottles (Samples A through J)from the refrigerator and allow the
samples to come to room temperature. Calibrate the pH meter using a two-point calibration
with pH 7 and pH 8 buffer solutions.
6.2 Invert the sample bottle several times to re-suspend the solids that may have settled during
storage. Measure 50 mL of the sample using a 50-mL graduated cylinder.
6.3 Pre-filter the 50 mL of sample through a 1.0-µm glass fiber filter prior to sample
manipulation. Transfer the sample filtrate to a 100-mL beaker equipped with a Teflon stir
bar. Place the beaker on a mechanical stir plate and gently stir the sample.
6.4 Measure and record the sample pH(initial pH). Gently open a buffer capsule and add
approximately one-half of a pH 7 Metripak, pHydrion buffer capsule(powder only); stir until
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Technical Bulletin No. 803 C5
all of the buffer has dissolved. Reserve the remaining half of the buffer for the next sample.
Adjust the sample pH to 7.6±0.05 by adding a small volume of sodium hydroxide solution
(preferably 20%)dropwise or hydrochloric acid (preferably 4%), depending on the initial pH
of the sample. The sample aliquot must be discarded and re-prepared if the sample volume
changes by more than 2%before the pH is within the desired range. Differing strength acid
and/or base solutions may be used to meet this criteria. Record this adjusted pH on the data
sheet.
6.5 Assemble an aspiration-type filtering apparatus and pre-wet a 0.8 Nm membrane filter with
approximately 1 mL of deionized and/or distilled water on each side of the membrane.
Gently shake off the excess water,place the filter onto the filter support, secure the filter
holder/funnel in place,turn the aspirator on, and slowly add the sample. Watch for a rapid
decline in the rate of flow through the membrane or foam coming off the membrane filter,
which can indicate filter plugging. If the filter plugs,immediately replace the filter with a
new filter pre-wet with deionized and/or distilled water and continue filtering the remaining
sample. Record the number of filters used to prepare each of the samples on the data sheet.
6.6 Verify that the spectrophotometer is still zeroed. Rinse the cell with a small amount of the
filtered sample. Discard the rinse. Transfer a portion of the filtered sample to the cell and
measure the absorbance at 465 tlm. Transfer all of the filtered sample back into the original
beaker. Measure and record the sample's pH and record this value on the data sheet as the
post-filtration pH. Rinse the cell thoroughly with deionized and/or distilled water. Verify
once again that the spectrophotometer is zeroed.
7.0 CALCULATIONS AND REPORTING
7.1 Calculate the color units for each sample by utilizing the measured absorbance value and the
linear equation derived from the calibration curve (Section 4.0) in your lab. The following is
an example calculation from a calibration curve prepared in our laboratory.
7.2 The calibration curve slope and y-intercept will vary depending on the light path length of the
cell used in each different spectrophotometer. Therefore it is important to use the same cell
for all measurements.
Example Calculation:
Absorbance 0.039
Equation y=0.0003x+0.0016
x=y-0.0016
0.0003
Substitution x=0.039-0.0016
0.0003
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1
C6 Technical Bulletin No. 803
NCASI COLOR MEASUREMENT STUDY DATA SHEET
Participating Company
Address
Phone Number Contact Person
Apparatus:
Instrument Manufacturer Model
Wavelength Used Cell Path Length
Calibration Curve:
Standard Level (CU) Absorbance
10
25
50
100
250
500
**If your lab uses a spectrophotometer that stores calibration curve data, please record the
stored absorbances or color units if possible.
Calibration Curve Equation RZ Value
Calibration Check:
Absorbance and/or color units of color standard calibration check
Date Analyzed
Samples:
Sampl Initial Adjuste Post- Number of Absorbanc Color Date
e Code pH d pH Filtration membranes a Units Analyze
pH used (PCU) d
A
B
C
D
E
F
G
H
I
J
K
L
Comments:
National Council for Air and Stream Improvement

Technical Bulletin No. 803 Dt
APPENDIX D
YOUDEN PAIR STATISTICAL ANALYSIS PLOTS
Figure Dl illustrates the raw data received for the two lignin samples analyzed as part of the inter-
laboratory study. The plots are made by using the results for one sample as abscissa,and the results
of the other sample as ordinate. The average of all the data points for Lignin 1 and Lignin 2 are
represented by the vertical and horizontal lines in the middle of the graph. The ideal situation would
result in data points found along the 45-degree line of the graph with the data clustered near the
intersection of the two average lines. The closeness of the individual points to the 45-degree line
reflects the within-laboratory precision, and the overall spread in either the abscissa or ordinate
direction reflects the overall precision or reproducibility. The data from laboratory L3 is biased high,
as indicated by its location removed from the other laboratory results to the high extreme on the x and
y axes. Dixon's test for outliers indicated that the results from L3 could be removed from the data
set.
140
120
U 100 /
80 i
♦ �; L7 • L2
60­
40 L8 I
20
40 60 80 100 120 140
Ugnin 2(PCU)
Figure Dl. Youden Pair Plot for Lignin 1 and Lignin 2.
National Council for Air and Stream Improvement

D2 Technical Bulletin No. 803
C
J
Figure D2 illustrates the raw data received for the two effluent samples (Mill A) analyzed as part of
the inter-laboratory study. The data from laboratory L3 is biased high, as indicated by its location
removed from the other laboratory results to the high extreme on the x and y axes. Dixon's test for
outliers indicated that the results from L3 could be removed from the data set.
800
U 750 ♦ L2 • L3
R 700
Q 650 L7
600 *-L6
550
wI11
500 A'L8�
W 450 ♦ L4
400
400 500 600 700 800 900
Effluent Mill A-2 (PCU)
Figure D2. Youden Pair Plot for Effluent Mill A-1 and Effluent Mill A-2.
Figure D3 illustrates the raw data received for the two influent samples (Mill A) analyzed as part of
the inter-laboratory study. The data from laboratories L3 and L2 are biased high, as indicated by their
locations removed from the other laboratory results to the high extreme on the x and y axes. Dixon's
test for outliers indicated that the results from L3 and L2 could be removed from the data set.
1100
U 1000 T • L3 ♦ L2
a
Q 00 .LS
° 600 L6
°' Ly
C � �
r. 500 ! LA ,
.
500 600 700 800 900 1000 1100
Influent Mill A-2 (PCU)
Figure D3. Youden Pair Plot for Influent Mill A-1 and Influent Mill A-2.
National Council for Air and Stream Improvement

Technical Bulletin No. 803 D3
� 1
Figure D4 illustrates the raw data received for the two effluent samples (Mill B) analyzed as part of
the inter-laboratory study. The data points plotted from laboratory L3 and L2 are biased high, as
indicated by their locations removed from the other laboratory results to the high extreme on the
x and y axes.Dixon's test for outliers indicated that this bias was significant and these laboratories
were removed from the data set.
300
U • L3
250
Pa
200
•150 L]
♦ L41 8
W
100 I
140 160 180 200 220 240 260 280 300 320
Effluent Mill B-2 (PCU)
Figure W. Youden Pair Plot for Effluent Mill B-1 and Effluent Mill B-2.
Figure D5 illustrates the raw data received for the two influent samples (Mill B) analyzed as part of
the inter-laboratory study. The data from laboratory L3 is biased high, as indicated by its location
removed from the other laboratory results to the high extreme on the x and y axes. Dixon's test for
outliers indicated that this bias was significant and this laboratory was removed from the data set.
300 L3
I
� t
250 j
M 200 —; L2
+ 13
150 j L6 BLS I
100 J* L44L+ L8
a
o-r
50
80 100 120 140 160 180 200 220
Influent Mill B-2 (PCU)
Figure D5. Youden Pair Plot for Influent Mill B-1 and Influent Mill B-2.
National Council for Air and Stream Improvement

D4 Technical Bulletin No. 803
Figure D6 illustrates the raw data received for the two receiving water samples (Mill D) analyzed as
part of the inter-laboratory study. The data points plotted from laboratory L3 and L2 are biased high,
as indicated by their location removed from the other laboratory results to the high extreme on the
x and y axes. Dixon's test for outliers indicated that this bias was significant and these laboratories
were removed from the data set.
240
220
oV L2
200
180
Ca
160 � L6 '�' ♦ 1 5
140 �L1 • L7
94 120 ]14L8
100
100 120 140 160 180 200 220
RW Mill D-2 (PCU)
Figure D6. Youden Pair Plot for Receiving Water Mill D-1 and Receiving Water Mill D-2.
l
National Council for Air and Stream Improvement

.*£D Sri
f0 UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
' REGION 4
ATL.ANTA FEDERAL CENTER
t' 02 61 FORSYTH STREET
YT44 PROIS ATLANTA, GEORGIA 30303-3960 RECEIVED
WY 16 2001 NOV 2 6 2001
N.C. ATTORNEY GENERAL
Environmental Dlvision
Mr. Gregory J. Thorpe, Ph.D.
Acting Director,Division of Water Quality �] D
North Carolina Department of Environment and Natural Resources =- 3
1617 Mail Service Center
Raleigh, North Carolina 27699-1617
WATER pHALITY SECTION
Dear Dr. Thorpe:
ASHEVILLE REGIONAL OFFIC€
The purpose of this letter is to provide the results of Environmental Protection Agency's
(EPA's) Clean Water Act Section 303(c) review of the State's action to reissue the variance for
instream color for the Blue Ridge Paper Products, Inc. (Blue Ridge Paper) discharge to the
Pigeon River.
The variance for instream color was reissued by the State on October 10, 2001, with an
effective date to be the same as the effective date for reissuance of National Pollutant Discharge
Elimination System permit No. NC0000272. The October 2001 color variance was certified as
"duly adopted in accordance with N.C.G.S. §143-215.3(e) and 15A 2B.0226, following notice,
public hearing and consideration by the NPDES Committee of the Environmental Management
Commission" in a letter dated October 16, 2001 from Francis W. Crawley, Special Deputy
Attorney General, Commission Counsel to the EPA Region 4 Regional Administrator. The
basis of the State's 2001 modification to the variance is that "further reductions in color cannot
be made at this time in an economically reasonable manner, and, if required, would produce
serious hardship without equal or greater benefits to the public." [Color Variance, October 10,
2001, page 101
EPA's initial approval of the variance, which was adopted by the State on July 13, 1988,
was based on the provisions of 40 C.F.R. §131.10(g)(6), which state:
States may remove a designated use which is not an existing use, as defined in
§131.3, or establish subcategories of a use if the State demonstrates that attaining
the designated use not feasible because . . . Controls more stringent than those
required by Section 301(b) and 306 of the Act would result in substantial and
widespread economic and social impact.
Since the State's original adoption of the variance, more restrictive color limitations have
been established, and the point of compliance with instream color requirements has been moved
IWOM t Aad-s5(JPL)• ht1D!r'WNW.bt'2 got
1'.•:.r:�r..i:.sala4ln.:•r and aAh\:•rp.,VA. 1 nl Ne;wl Ir,Ys vn Rey tl:•d o. r..:y
Y 1 rd[hnr.:us,',.r..

2
further upstream to a location closer to the Blue Ridge Paper outfall. Also, the 1996 and 1997
modifications of the variance required further evaluation and reporting of the technical,
economic, and operational feasibility of color minimization, color removal, and color treatment
(on both a continuous or intermittent basis), which served as the basis for incremental reductions
of color discharged to the Pigeon River. In regard to compliance with these historical and
current conditions of the variance, the previous discharger(Champion International) and its
successor (Blue Ridge Paper) have complied with all terms of the original variance and the 1996
and 1997 modifications of the variance.
EPA's review of the color variance reissued by the State on October 10, 2001 is based on
the provisions of 40 C.F.R. §131.20, which require the following:
Any water body segment with water quality standards that do not include the uses
specified in Section 101(a)(2) of the Act shall be reexamined every three years to
determine if any new information has become available. If such new information
indicates that the uses specified in Section 101(a)(2) of the Act are attainable, the
State shall revise its standards accordingly.
In 1997, several groups signed an agreement which established specific requirements for
the operation of the Blue Ridge Paper mill and for the wastewater treatment operations at the
mill, and governed certain actions of regulatory agencies relating to the Blue Ridge Paper facility.
This 1997 Settlement Agreement established that the Technology Review Workgroup
(Workgroup) would study available color reduction technologies and report on those
technologies prior to reevaluation of the variance in 2001. The 1997 Settlement Agreement
also recognized that the EPA Technology Team would study options for color reduction at the
Blue Ridge Paper mill, and prepare a report for the Workgroup's use in their evaluations. The
Workgroup's analysis presents a summary of the analysis of available color reduction
technologies that may be employed.at the Mill as well as a summary of the estimated economic
impact of the cost of implementing those technologies. The report included review and input
from North Carolina, Tennessee, the Clean Water Fund of North Carolina, Liebergott and
Associates and GL&V Pulp Group, Inc., and Blue Ridge Paper. The report also addresses
relevant technologies evaluated in the Bleach Environmental Process Evaluation and Report.
The Workgroup identified five process improvements capable of further reducing color
discharged from the Blue Ridge Paper Mill, and reviewed the technical feasibility, capital and
operating costs, and potential color reduction capacity of each. Due to the potentially high initial
capital investment costs and ongoing operating expenses of end-of-pipe treatment technologies,
the Workgroup focused on pollution prevention approaches such as color reduction in low flow,
highly color-concentrated waste streams, through manufacturing changes or in-process treatment.
The Workgroup reviewed the EPA Technology Team report, reviewed reports submitted
by Blue Ridge Paper, conducted a site visit to the Blue Ridge Paper Mill in March 2001,
reviewed the Bleach Environmental Process Evaluation and Report dated June 8, 2001, and

e
3
considered comments from environmental interests and other stakeholder groups in reaching
their conclusions and recommendations. Among other conclusions, the Workgroup found that
the EPA Technology Team report "represents an appropriate evaluation of the potential for
additional color reduction at the Mill over the next permit cycle."
The Workgroup considered these five process improvements for specific inclusion for
implementation or further study as terms of the variance as well as the recommendation of the
Bleach Environmental Process Evaluation and Report for process optimization on both the
hardwood and softwood fiber lines. Two of these five process improvements (improvements in
bleach filtrate recycle reliability and leak and spill prevention and control - best management
practices) and the process optimization option recommended in the Bleach Environmental
Process Evaluation and Report were concluded to have the "highest certainty for technical
feasibility and color reduction." Implementation activities for these three activities are required
in the conditions of the variance.
The Workgroup identified two other process improvements (ozone addition to an existing
chlorine dioxide bleaching stage on the hardwood fiber line and adding a second stage to the
current oxygen delignification system on the softwood fiber line) as having a "reasonable
certainty for technical feasibility and color reduction."
The variance requires an evaluation of these two technologies as well as a requirement for
Blue Ridge Paper to submit a proposed schedule for implementation of these two process
improvements or installation of technologies required to achieve an effluent color reduction of
3,000 - 8,000 pounds per day over and above the color reduction of the "highest certainty"
improvements. The incremental range of color reduction of 3,000 to 8,000 pounds per day is
commensurate with the range of color reduction identified by the Workgroup as possible with the
implementation of the "reasonable certainty" improvements.
The Workgroup also identified a fifth process improvement (color treatment for the
chloride removal process (CRP) purge stream) as having potential for additional color reduction.
Based on the results of previous laboratory trials of color precipitation, Blue Ridge Paper
concluded that lime treatment is not a feasible option for the CRP purge stream. However, the
EPA Technology Team recommended "additional review of other innovative technologies for
treatment of color in the CRP purge stream, such as the application of the X-Filter process
recently implemented at a totally chlorine free (TCF) mill." Based on the Workgroup's
recommendation, the variance requires that Blue Ridge Paper: (1) complete an evaluation of the
technical, economic, and operational feasibility of implementing color reduction technologies
associated with the CRP waste stream, and (2) prepare a report on those investigations, unless
Blue Ridge Paper identifies a feasible technology for treatment of this waste stream, in which
case the obligation to research additional technologies will be waived.
The conclusions of the Workgroup serve as the basis for the inclusion of color reduction
technologies and targeted ranges of color reduction as requirements in the variance, as well as the

4
inclusion of future steps to be completed prior to the next review of the variance.
In addition, EPA used three measures of financial health (gross profit test, discounted
cash flow, and Altman's Z) "to assess the impact of air emissions control technologies and
devices and wastewater compliance costs." Based on analysis of that assessment and the
conclusions reached by the Workgroup, the underlying rationale for EPA's approval of the July
13, 1988 variance has not changed, and there is no information presented which would serve as a
basis to conclude that Section 101(a)(2) uses, i.e., Class C uses and the supporting water quality
criteria for instream color, are attainable at the present time.
EPA initiated informal consultation with the U.S. Fish and Wildlife Service (Service) on
October 12, 2001, under Section 7(a)(2) of the Endangered Species Act. Section 7(a)(2) requires
that federal agencies, in consultation with the Service, insure that their actions are not likely to
jeopardize the existence of federally listed species or result in the adverse modification of
designated critical habitats of such species. Upon completion of consultation, EPA will notify
the State of the results.
Considering the above, the requirements of the Clean Water Act and 40 C.F.R. Part 131 `
in relation to attainability and the continued progress to meet the full Section 101(a)(2) use have
been met, and the State's action to continue the color variance is approved subject to the results
of consultation under Section 7 of the Endangered Species Act.
If you have questions concerning this matter, please contact me at 404/562-9326.
Sincerely,
Beverly H. Banister, Director
Water Management Division
cc: Francis W. Crawley

OPERATING EXPERIENCE WITH AN 1.2
OZONE-BASED ECF BLEACHING E t.0
SEQUENCE " _ •
W n 0.8 anil ` ■ ♦ ♦ • Aspen
Fred Munro,Manager Technical Services,Domtar Inc., o a 0.6 o ♦ =sof wood
Eddy Specialty Papers Division g • ♦ Aspen
D 0.4 Softocd
John Griffiths,Senior Process Engineer,Dom 6
tar Inc., •
Eddy Specialty Papers Division
Y �
0.0
ABSTRACT 0 s tc is 20 25
A medium consistency ozone stage was incorporated Black liquor carryover(kg Conn)
in a(ZD)configuration as part of a complete hardwood fibre
line modernization at the Espanola mill.The major Fig.1 Effect of COD carryover on ozone stage
expectations from ozone were improved bleaching economy,a delignification(Pilot plant results)
higher brightness ceiling,and reduced environmental impact.
Operating results have exceeded expectations. Ozone BLEACHING SEQUENCE DEVELOPMENT
has a chlorine dioxide replacement ratio of 3.5 (1 kg/t ozone In 1996 the Espanola mill began a project to
replaces 3.5 kg/t chlorine dioxide)on hard to bleach species modernize the hardwood pulping and bleaching line.The
and a replacement ratio of 2.5 on easily bleached species, objective was to build a pulping line to economically produce
significantly improving bleaching economy.Effluent AOX, world-class hardwood pulps with low environmental impact.
COD, and colour have decreased significantly. Pulp The old bleaching sequence was ODcEDnD. The
extractives and TOX content have decreased.Pulp cleanliness decision to retain the existing towers constrained the new
is exceptional.Pulp strength and viscosity have been sequence to four bleaching stages.The ozone pilot plant work,
maintained with the new bleaching sequence. in conjunction with Air Liquide's research on(ZD)bleaching
and extensive lab trials at PAPRICAN,identified the
INTRODUCTION OA(ZD)EDnD sequence as the best choice to maximize
The Espanola pulp mill has two complete pulping and brightness,maintain pulp physical properties,and minimize
bleaching lines,one producing softwood and the other chemical cost and environmental impact.
producing hardwood.Total production is 1000 ADMT/day of Although the pilot plant trials showed that acid pre-
fully bleached pulp.Weak black liquor from both lines is treatment did not improve an ozone stage,the A(acid)stage
combined and processed through a single recovery boiler and was installed to strip metals from the pulp and eliminate
recausticizing plant.Two integrated paper machines produce calcium-based scaling on the bleaching equipment.The acid
200 ADMT/day of specialty,packaging,and fine papers. charge required for the ozone stage is actually added to the A
Effluents from all areas are combined and treated in an aerated stage,extending the usefulness of the sulphuric acid.This
stabilization basin. stage has been successful in eliminating scale throughout the
In the late 1980s,environmental concerns arose with bleach plant.
dioxin and chlorinated organic compounds(measured as AOX) The ozone stage was installed in a(ZD)
in pulp mill effluent.In response,the Espanola mill began configuration.The stage is configured such that ozone is
investigating several chlorine-free bleaching alternatives, reacted,the residual oxygen is removed from the pulp,and
among which was ozone.A partnership was established with chlorine dioxide is added and reacted.The pulp is then
Kamyr Inc. and Canadian Liquid Air to install an ozone pilot washed.The Do segment is sized large enough to carry the
plant in the Espanola mill and use it to investigate ozone entire bleaching load of this stage.
bleaching on Espanola's oxygen delignified softwood and There were several reasons for the choice of a(ZD)
hardwood pulps. stage.We assumed(correctly,as it turned out)that there would
be some start-up difficulties with the ozone system,and
OZONE PILOT PLANT wanted the full Do backup to maintain pulp quality.In addition,
The 5 TPD ozone pilot plant was commissioned in our research had shown that there were no adverse quality
April 1992 and operated for 14 months. Early in the program effects on the pulp if ozone was utilized in a(ZD)
the effort was focused on medium consistency bleaching.The configuration,whereas more care had to be taken with a full
pilot plant work showed that ozone.was a powerful, ozone stage(ZZ).The(ZD)configuration was chosen to
economical bleaching agent that could be applied without protect our pulp customers from adverse changes in physical
degrading pulp quality.Two of the key findings from the pilot properties.
plant work were:
• An ozone stage is sensitive to carryover(see.Fig.1) HARDWOOD LINE MODERNIZATION
• Espanola's northern hardwood pulps can absorb large Once the bleaching sequence was chosen,the
ozone doses without degradation in physical properties. modernization was designed around the unique requirements
of an ozone stage.

Primary concerns were: with 20 seconds retention time.At the top of this tube an
♦ Good brownstock screening for shive removal Ahlstrom degas unit removes 50%of the entrained gas and
♦ Good brownstock washing for low carryover into stabilizes the pressure in the tube.The pulp discharges from
the ozone stage. the degas unit through a pressure control valve into the
A 4 stage brownstock screening system was installed, standpipe of the second MC°pump.The remainder of the
using a Pl/P2 configuration.The first primary screen uses entrained gas is taken off the top of the standpipe and,along
0.060"hole baskets,followed by the second primary barrier with the gas from the degas unit,is passed through a fibre
screen with 0.006"slots. scrubber and into the ozone destruct unit.The pulp is pumped
Brownstock washing was designed with three to the CIO,chemical mixer and into the Da tower.
washing devices ahead of the oxygen stage(2 IMPCOO CB The ozone stage operates at 1035 kPa and 50 C.Stock
filters, 1 IMPCO®wash press)and three washing devices pH is controlled to 2.5—3.5.The ozone charge is fixed at 6
following the oxygen stage (1 IMPCO®CB filter, I IMPCO® kg/ADMT and the CIO,charge to the Do stage is varied to
Coru-Dek IV°vacuum drum filter, 1 IMPCO®wash press— compensate for incoming kappa number variations.
see Fig.2).The wash press was installed ahead of the ozone
stage as a thermal barrier for the ozone stage and a chloride OZONE STAGE PERFORMANCE
barrier for the recovery process. The hardwood line produces three pulps: aspen,
We commissioned the modernized hardwood line in maple,and birch.Aspen is the easiest to bleach and birch the
three stages—brownstock washing and upgraded most difficult.These two species were used to evaluate the
centricleaning in September 1997,brownstock screening in performance of the ozone stage.
April 1998,and the bleach plant in September 1998.The
ozone stage was commissioned in May 1999.
ftmh N@7&5@@9Iwo :
yam.
Knotbo
®®I _
t
} Chip Bho a. Chip PH=
BrorroatadlWu6hp IiatehDlpaatan
a
&wardti8 �.
01Qglt1 Deuptiftroan
s s
TDPUU
AIACHINE
}3 n{ppp F C&"Dlwdd*Sbtpa
3 i 5 j t
I
Chlorhta Cbddell4atdra0raft 5hpa
Chlatim Claws Stop
Fig.2 Modernized hardwood line
The primary determinant of medium consistency
OZONE GENERATION ozone stage performance is the ability of the system to mix and
Ozone is purchased"across the fence"from Air react the ozone gas.A measure of this ability is the ozone
Liquide.The 3.6 tonne/day ozone plant consists of two consumption at a given ozone charge.As can be seen from
generators and two liquid ring compressors and is designed to Fig.3,ozone consumption decreases as the ozone charge
deliver 12.5%ozone at 1140 kPa to the ozone mixers. exceeds 4 kg/t,but remains above 94%even at high charges
The data scatter results from operating variations in carryover,
OZONE STAGE OPERATION incoming Kappa number,and pH.
The ozone stage consists of two Ahlstrom AMZTm
mixers fed by an MC©pump.Ozone is fed to each mixer, but
the majority of the flow(80%)goes to the first mixer.The
second mixer discharges into a vertical flow stabilization tube

Selectivity
r- 100 �C• •e The selectivity of the ozone stage(measured as
g d 99 viscosity loss per kg/ADMT ozone charged)is strongly
o E 57 _ affected by the incoming viscosity(see Fig.5).
`w o 96
m U 95
g 'a94 ~ 0 1.8 -'
C °H 93 '_m 1.6
c O 92 •Aspen x i IA
O `\-e 91 •Birch a' n
0 2
90 1
m 1.0
0 2 4 6 8 m a i
a j 0.8
Ozone Charge(kg/ADMT) L 0.4 o.s
0 0
n
Eig.3 Effect of ozone charge on ozone mixer efficiency- 0 z o.x
February 2000 data
0.0
12 14 16 16 20 22
The effect of the following parameters on the Initial viscosity(cps)
performance of the ozone stage was evaluated:
♦ Reaction pH(2.5-5.5) 1 • 4.4k AOMTAPPRedO3-y=.0.0243xA2+0.9931X-7.9758
-
♦ Temperature(50-60`C) Fig.5 Selectivity vs.incoming viscosity-Birch pulp,4.4
♦ Ozone charge(1 -6 kg/ADMT) kg/ADMT ozone charge,48eC,2.5 pH
Ozone stage performance was evaluated using two
parameters: - Ozone charge,reaction temperature,or reaction pH does not
♦ Delignification efficiency(Kappa drop/kg 03 applied) significantly affect the selectivity(see Fig.6).The data in
♦ Selectivity(Viscosity drop/kg 03 applied) Fig.6 have been corrected for variations in incoming viscosity.
Delignification Efficiency 2.0
As ozone charge increases,the delignification 1.6
efficiency(measured as Kappa drop per kg/ADMT ozone a 1.6
charged)decreases(see Fig.4). Lack of available lignin at m $ 1A
higher ozone charges does not appear to explain this decrease 0 0 12
because data from a high input Kappa trial falls right on the 3 a 08
0.6, ■
curve(Fig.4).The effect may be due to reaction kinetics and c ;; o.s
the retention times in Espanola's particular system,since o 1 0.4
raising the reaction temperature to 60 C appears to increase the 02 ■
delignification efficiency back to 1.0 and increasing the pH to 0.0
5.5 appears to decrease the delignification efficiency. 0 1 2 3 4 5 6 7
Ozone Charge(kg 03/AOMT)
■50C,2.5 pH A 50C 4.5 H A We 5.5 pH•55C 2.6. H high Viscomny In A 60C.2.6 cHl.
1.6 Fig.6 Selectivity vs.ozone charge,temperature,and pH-
r m 1A ■ Birch pulp,corrected to 14 cps incoming viscosity.
m - ■
- < 12
w 0 1.o ■ OZONE STAGE ECONOMY
o.e • _ The economy of an ozone stage is mill dependent and
oos ■ is determined by the relative costs of ozone and chlorine
m a o,4. ■ ' dioxide and by the ozone replacement ratio.
c x 02 Used in a(ZD)configuration,ozone replaces some of
0.0 - the chlorine dioxide normally used in the first stage.The
0 1 2 3 4 5 6 2 kg/ADMT of chlorine dioxide replaced by I kg/ADMT of
Ozone Charge(kg 03/AOMT) ozone at equivalent final brightness is called the replacement
■ 56C.2.5pH • socyHcs • 56onH5.5 •ratio(i.e. a replacement ratio of 2.5 means that 1 kg/t of ozone
e 55c. H2.e."a I...... n 60CAH 2.6 -WC2.5 PH replaces 2.5 kg/t of chlorine dioxide).
Fig.4 Delignification efficiency vs.ozone charge, The hardest to bleach pulps have the highest replacement ratio.
temperature,pH,and incoming kappa number-Birch Aspen is the easiest to delignify and has a replacement ratio of
pulp,9.2 Kappa In,50eC,2.5 pH 2.5,while birch,the most difficult to bleach,has a replacement
ratio of 3.5. In all cases,ozone ECF is more economical than
C102 ECF with Espanola's chemical cost structure.
Stoichiometrically,ozone has a replacement ratio of
1.7.The higher replacement ratios achieved in practice are
likely due to the increased efficiency of the bleaching sequence

once ozone has been introduced,since ozone reacts with more upgraded at the pulp machine.As a result of these changes, all
lignin structures than CIO,. hardwood pulps have no measurable din content(see Fig.9)
The modem design of the new hardwood line reduced
ECF bleaching chemical cost by 23%in spite of an increase in
final brightness(see Fig.7).Addition of ozone to the sequence 5000 ---
reduced bleaching chemical cost by another 8%and further 4500
increased brightness.The average bleached brightness is now 4000 ---_
1.5%ISO higher than that from the old bleach plant at a 3500
reduction in chemical cost of 31%. 3000
m
'c 2500
a` 2000 T
'u 100 - 91.0 1500 Fe
O
m
90 -90.5 0 1000
85 - 500
c m 80 90.0 v 0 -
u e 75 � c
io 70 89.5 m 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
m 65 e m TAPPI Dirt(ppm)
_> 60 a 89.0 at
a 55 = a LL Fig.9 Hardwood pulp cleanliness histogram-1999 Data
rc 50 88.5
Old Line New Line New Line
ECF ECF Ozone ECF Extractives Content
Relative Bleachin Chemical cost©Final Brightness Ozone bleaching has reduced the DCM extractive
content of the pulp by 30-50%compared to conventional ECF
Fig.7 Impact of modernized pulping line and ozone stage bleaching,and by 70-80%compared to high substitution
on final brightness and chemical cost-1997-1999 averages bleaching on the old hardwood line(see Fig.10).The majority
of the improvement between the old line and new line ECF is
OZONE ECF PULP QUALITY attributed to the better brownstock washing with the new
equipment.
Physical Properties
To protect Espanola's pulp customers,ozone ECF
was brought on-line in stages and the pulps evaluated
internally prior to release to market.Ozone charges began at 1 0.25
kg/ADMT on pulp and were increased in a series of trials
which were lab evaluated and evaluated for performance in € 0.20 ClAspeon;mhn
Domtar paper mills.No significant differences were found °o
between the ozone ECF pulp and conventional ECF pulp in n 0.15
any of the hardwood species in lab PFI analysis(see Fig.8)or
in actual paper machine performance. a aut
0.0s
9.0
0.00
Old Line New Llne New Line
x 8.0 6e%Substitution ECF Ozone ECF
7.0 ` Bleaching Sequence
\ v Fig.10 Impact of hardwood modernization and ozone stage
6.0 r- on DCM extractives
5.0 Viscosity
The final viscosity of the fully bleached pulp was not
a.o affected by the use of ozone(see Fig.11).Although viscosity is
100 80 60 Tensile 40 20 0 lost across the ozone stage,the viscosity loss in subsequent
-�eirch ECF 1999 Aey. tBirch Ozone ECF 1999 Avg. bleaching stages is reduced,resulting in a fully bleached
Aspen Ozone ECF 1999 Av viscosity equivalent.to conventional ECF.
Fig.8 Tear/tensile relationship ECF vs.ozone ECF- 1999 TOX Content
averages Conversion to ECF bleaching reduced the Total
Cleanliness Organic Halide(TOX)content of bleached aspen pulp by 60%
The chive bleaching ability of ozone was an early and birch pulp by 80%.Adding ozone to the ECF sequence
reduced the aspen pulp TOX by 51%and the birch pulp TOX
concern in the project,so the screen room was designed with a by 69% (see Fig.12).
0.006"slot barrier screen and the centricleaner system was

COD
18 The use of ozone reduced the COD content of the acid
16 effluent by 33%N.The alkaline effluent COD content did not
,a 1412 change significantly(see Fig.14).
10
8 ■ECF
° 18.00
6
j - OZ ECF
q 16.00g DAcid Effluent
2 k•-" 14.00 DAlkaline Effluent
0 12.00
Aspen Birch p
10.00
Species m
8.00
Fig.11 Impact of ozone stage on full bleached viscosity- 0
1999 averages 0 6.00
4.00
2.00
1000 0.00
900 ❑BLch ECF Z ECF
600 OAS en
100 Fig.14 Impact of ozone stage on bleach plant effluent COD
E 600
u 500 Colour
0 400 The colour of the treated effluent results from the
300 colour contribution of both softwood and hardwood bleaching
200 line effluents and other liquor losses from the mill.Installation
100 of the new hardwood line equipment reduced total effluent
° colour by 21%,a considerable decrease considering the
Old Line New Line New Line
60%Subslilulion ECF Ozone ECF improvement was in one bleaching line only.The use of ozone
Bleaching Sequence reduced the total effluent colour by a further 27%,another
considerable decrease.Note that the conversion of the
Fig.12 Bleached hardwood pulp TOX content softwood bleach plant from high substitution to ECF bleaching
ENVIRONMENTAL IMPACT did not impact effluent colour.
The hardwood bleach plant effluents are segregated
into acid and alkaline streams.Each stream is processed 1000
through a fibre filter for fibre recovery prior to discharge to the n e00
effluent treatment system. ; 800
700
AOX fi00
The majority of the hardwood bleach plant effluent S00 -
AOX is found in the acidic filtrate.The use of ozone reduced 400
the AOX in this stream by 65%(see Fig.13). ' 300
0 200
V
0.50 1a
0.45 °
Acid Effluent SW60%Subsutubon SW6 Sub& SW 60%sub& SW ECF&
0.40 &HW Old Line HWNee,We ECF HWNew Llne HWNew Line
®Alkaline Effluent (60%SubSWutlon) Ozone ECF Ozene ECF
0.35
a 0.30 Fig.15 Impact of hardwood modernization and ozone stage
#0.25 on treated effluent colour
x _
x 0'20 CONCLUSIONS
< 0.15 '±`. Ozone has proven to be a practical,powerful
0.10 bleaching reagent.When incorporated into an ECF sequence,
0.05 ozone improved bleaching economy and pulp quality while
0.00 significantly reducing environmental loading.The medium
ECF Ozone ECF consistency ozone stage itself has a reasonable capital cost,a
Bleaching Sequence small footprint,and can easily be retrofitted into an existing
sequence.There are high potential capital costs,however,if
Fig.13 Impact of ozone stage on hardwood bleach plant washing and screening have to be upgraded to maximize the
effluent AOX benefits from ozone.

The(ZD)stage incorporated in Espanola's hardwood
modernization has improved bleaching economy,improved
pulp quality,and reduced the effluent load from the bleach
plant.Incorporation of ozone into the ECF bleaching sequence
has:
• Reduced ECF bleaching chemical cost by 8%
while increasing final brightness by 0.5%ISO
• Reduced pulp DCM extractives content by 30-
50%
• Reduced pulp TOX content by 50—70%
• Had no impact on pulp mechanical strength or
viscosity
• Reduced hardwood bleach plant effluent AOX by
65%
• Reduced hardwood bleach plant effluent COD by
18%
• Reduced total mill effluent colour by 27%

A
i
1213119 7 ArPDES Pernih and Modified Variance Compliance Timeline
Date: Requirements. Limitations & Details:
January I, 1998 Monthly average discharge of true color will not exceed 95,000 lbs/day
March 1, 1998 Status Report Due to NPDES Committee on the analyses prepared for other
permitting agencies concerning the effects of the BFRTm technology on air
emissions
June I, 1998 Report Due to Technology Review Workgroup(TRW)and NPDES Committee
which will identify a STRATEGY and TIMELINE for implementing the
following color reduction measures until the target effluent limitations are met or
all measures have been fully implemented:
• Further upgrading and integrating of sewer monitoring
— additional flow measurement and sampling stations
— substantially improve the mass balance
• Automated mill process control systems with operational
procedures and management oversight to reduce black liquor leaks
and spills.
• Continued operator training
• Identifying and implementing additional controls for known but,
unmeasured sources of liquor losses
— evaporator set
— knot rejects bins
• Modifying digester area to facilitate capturing of leaks and spills
• Diverting clean water discharges
. • Capturing and recycling liquors during fiber line disruptions:
— detailed scheduling of planned outages
— contingency planning for unplanned outages
• Thoroughly evaluate additional measures to modify its process
operations and controls to remove or reduce sewer generated color
The report will include an explanation of and rationale for both the
implementation strategy and proposed time line. The report will also identify
those measures which will be implemented in the event the effluent limitations of
December 1, 1998 are not met
June 1, 1998 Fully implement the following four BMPs:
• Installation of replacement digester recirculation pumps and a spill
collection sump
• Installation of a pine courtyard Parshall flume slide gate
• Installation of weak black liquor containment
• Other measures including:
— Correction of evaporator set demister clogging
— Installation of condensate instrumentation and sampling ports
for the evaporator set
— Assurance of continued dry conveying of knot rejects
•

re
October 1. 1998 If TRW determines,and NPDES Comminee agrees,that there are overwhelming
technical. economic or operational barriers to the permittee's ability to attain the
60.000 Ibs/dav annual average and 69,000 Ibs/day monthly average color loading
limits,the TRW shall recommend to the NPDES Committee the alternate
interim limits to become effective 12/l/98. TRW shall also recommend to the
NPDES Committee a new effective date for achieving annual average color
loading limit of 60,000 Ibs/day.
December 1, 1998 Submit to TRW a contingency plan, corresponding to periods of river flow less
than 330 cfs at Hepco gauging station, for mitigating the occurrence and degree
of potential exceedences of 50 true color units at Hepco by evaluating:
• scheduling of maintenance
• intermittent treatment
• production curtailment
• any other temporary measures
NOTE: The model limitation may be extended beyond 1211198 if the NPDES
Committee establishes interim limits which require the model to be used to
assure compliance with 50 true color units at the state line.
Monthly average discharge of true color shall not exceed 69,000 Ibs/day
Annual average discharge of true color shall not exceed 60,000 Ibs/day
Pigeon River color at Hepco gage shall be less than 50 true color units whenever
monthly average flows are greater than 330 cfs.
January 1, 1999 Begin implementation of Eo recycle on the hardwood fiber line
February 1, 1999 TRW will recommend to the NPDES Committee either approval of or
modification to the plan.
March 1, 1999 The low flow contingency plan shall become effective upon approval
December 1, 1999 Report Due to TRW and NPDES Committee on:
• Evaluation of color reduction benefit gained from Eo recycle on
the hardwood fiber line
• Potential color reduction benefit to be gained from full
implementation of the BFRTM technology on hardwood fiber line
--- NOTE. All of the above color related work is referred to as the NEAR-TERMPACKAGE--
June 1,2000 Anticipated that Poll implementation of Near-Term Package could be effectuated
January 1,2001 Report Due to TRW and NPDES Committee on the feasibility of achieving a
target annual average color loading limit within the range of 48,000-52,000
lbs/day on Poll implementation of the Near-Term Package.

March 1,2001 A) Evaluate and report on end-of-pipe color reduction technologies in
conjunction with the Triennial Review of NC Water Quality Standards. This
evaluation shall include:
• Incremental color improvement analysis
• Technical, economic and operational feasibility of the application
of these technologies on a continuous or intermittent basis
(specifically at periods of low river flow)
• Economic and Implementation issues associated with the
incremental improvement of color levels expected by installing
these technologies
• Projection of the expected additional color reduction for each
technology and the maximum color reduction possible
B) Updated report on the results of all ongoing and any additional planned color
reduction activities.
April 1,2001 TRW shall recommend to the NPDES Committee and other Settlement
Agreement parties,considering the feasibility report submitted on January 1,
2001 and the demonstrated performance of the mill,the lowest achievable annual
average and monthly color loading effluent limitations.
May 1,2001 The recommended limits,if within the target range(48,000-52,000 Ibs/day),
shall become effective
June 1,2001 • Submit Report to the NPDES Committee and NCDENR, Division of Water
Quality, on the comparative evaluation of the above collaborative efforts as
part of the Variance review process.
• Statistically evaluate the monthly average color discharge, annual average
color discharge and performance of the mill in relation to color discharged.
• Results used to make recommendations to the 1997 permit for the 2002 permit.
November 30,2001 Permit shall expire at midnight
GENERAL The mill's pulp production capacity will not be increased during the
PROVISION permit unless this can be done in a way that also reduces color loading.

Canton Mill Secondary Effluent Color Performance
Annual Averages: 1988 - 2000 (through Sep.)
400,000 Including Permit Limitations
Permit Limitations:
350,000 1-258,945 Wd Monthly Ave.eff.4/14/94
2-172.368#/d Annual Ave.eff.4114194
3-125,434#/d Monthly Ave.all.12/12196
4-98,168#/d Annual Ave eff.12/12/96
5-95,000#/d Monthly Ave eff.111198
300,000 6-69,000#/d Monthly Ave.eff.1211198
T 7-60,000#/d Annual Ave.all.1211/98
tp 8-48,000-62.000#/d Target Annual Ave
9
N
c 250,000
`0 1
0
U
200,000
LU
W
a2
150,000
c
0
0
r n 3
100,000
4 5
50,000 6
7 8
1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000
Permit Urnitaions 0 SE Color Annual Ave.Wd
Blue Ridge Paper Products, Inc.
Canton, NC MSH 12/12/00

TN 140 & SLc
Actual Measured Color in the Pigeon River
at the NC/TN Line for the Canton Mill
225 Including Background River Color (Upstream of Mill
Monthly Averages from 1188-10100
200
175
..I
E 150
c
0
125
c
100
0
U
`0 75
0
U
50 —
25
0
9� 'bq bq qFj 4' �� Q� a a qb qb q'� q" qb qb (:P CP oJA 0A CP 4� 4° Q� (�
-w-ACTUAL MEASURED TN140 CLR ST mg1I mon avg - Canton Color
Blue Ridge Paper Products, Inc.
Canton, NC MSH 12/12/00

Blue Ridge Paper Products, Inc. - Canton, North Carolina
Monthly Average Secondary Effluent COD (kg/tonne)
January 1991 - October 2000
60.0
50.0
40.0 Proposed Cluster Rule Limitations for
/ Bleached Papergrade Kraft Mills
30.0 t----------------- -- - - ---------------------—-----------------------......................................
20.0
10.0
0.0
N N N N r7 r7 r ) -41- Ln U-) Ln Ln CO c0 C0 I, r n r` 00 CO 00 CO O� O� M O O O O
Q7 Q) 07 Q7 Q7 O) Q7 O) D7 D7 a7 O) Q7 Q7 O Q7 Q7 Q7 Q7 Q7 Q7 D7 Q7 O) Q7 Q7 Q) Q7 Q7 Q7 Q7 O O O O O O
I I I I I I I I I I I I I I I I I I I I I I I
>
� ¢ O O Ln
SE COD COD kg/kkg COD Option A (Conv Delig w/ 100% sub) - - - COD Option B (02 Delig w/ 100% sub)
MSH 12/12/00

Blue Ridge Paper Products, Inc. - Canton, North Carolina
Monthly Average Secondary Effluent BOD (kg/tonne)
January 1988 - October 2000
4.00
3.50 I
Proposed Cluster Rule Limitations for
3.00 Bleached Paperlgrade Kraft Mills
2.50
2.00 -
1.50 -
1.00
0.50
0.00
00 00 00 00 0)0) MCD 00--��NNNNMI"7M��a' �U-)LnLnC CDC I--nnt 00 00 00 00 0�0�M 0 C=) CD
00 00 00 00 00 00 00 co 010)MQ)0"�0�0�Oa70)0�0)M 0 M 0�0)M M M M M M 0)M M M O M M0> 0�000000
I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I
o N U 0 �¢zl��Vl 07¢�0 N N N 0� " ��¢z4�..7(n� U
O� Q O�
EE —SE BOD kg/tonne �BOD�Opfion �Avgof �rrulls - - - BOD Option 2 Avg of best 50% of mills
MSH 12/12/00

Blue Ridge Paper Products, Inc. - Canton, North Carolina
Monthly Average Secondary Effluent TSS (kg/tonne)
January 1988 - October 2000
8.00
7.00
6.00
Proposed Cluster Rule Limitations for
5.00 Bleached Papergrade Kraft Mills
4.00 -
3.00
2.00
1.00
0.00
co 0000000�M 0�rn O C 0C ) NNNNM�"7M�d"-d-CCU L-�Ln Ln CD c0 CO r, 00000000MC"0�0000 0�•—
COC000 00 00 00 00 00 0�0)0)OO�O)O)0)00010�0�0�0�0)0�O)d7mO)0>O)0>OO)O�O)0�0�0)0�0�0�rn0)00000
C » >.8 w O C U C Cl�O O N N O =(J CO O-�0 U N N O n
�¢�ZIi�LCn� �0�¢ �O��QZti�N�
--SE TSS kg/tonne TSS Option 2 Avg of best 90% of mills - - - TSS Option 1 Avg of best 50% of mills
MSH 12/12/00