NC0084573_Renewal (Application)_20200116

ROY COOPER
Gowmoir
MICHAEL S. REGAN
Secretary
LINDA CULPEPPER
Director
Lincoln County
Attn: Donald V. Chamblee, Jr.
5291 Crouse Rd
Crouse, NC 28033
Subject: Permit Renewal
Application No. NCO084573
Lincoln County WTP
Lincoln County
Dear Applicant:
NORTH CAROLINA
Environmental Quality
January 16, 2020
The Water Quality Permitting Section acknowledges the January 15, 2020 receipt of your permit renewal application and
supporting documentation. Your application will be assigned to a permit writer within the Section's NPDES WW permitting
branch. Per G.S. 150B-3 your current permit does not expire until permit decision on the application is made.
Continuation of the current permit is contingent on timely and sufficient application for renewal of the current permit. The
permit writer will contact you if additional information is required to complete your permit renewal. Please respond in a
timely manner to requests for additional information necessary to allow a complete review of the application and renewal
of the permit.
Information regarding the status of your renewal application can be found online using the Department of Environmental
Quality's Environmental Application Tracker at:
https://deg.nc.gov/permits-regulations/permit-guidance/environmental-application-tracker
If you have any additional questions about the permit, please contact the primary reviewer of the application using the
links available within the Application Tracker.
Sincerely, (�,
_.NaA �'� ►'��y
Wren Thedford
Administrative Assistant
Water Quality Permitting Section
cc: Central Files w/application
ec: WQPS Laserfiche File w/application
North Corot no Department of Envsronmenta Qua;rty I D;vsron of Water Resources
Mooresv i+e RegonaOff .oe 161O East Center Avenue, Surte 3011 Mooresv' *,North Carovne 28115
7D4-M4699

Wren Thedford
NC DENR/DWR/NPDES Unit
1617 Mail Service Center
Raleigh, NC 27699-1617
January 07, 2020
Re: NPDES Permit NCO084573 Renewal Request
Dear Wren Thedford,
LINCOLN COUNTY PUBLIC WORKS
CHRIS HENDERSON
SENIOR ENGINEERING ASSOCIATE
RECEIVED
JAN 15 2020
NCDEIDONRINPDES
I am writing this letter to you to formally request the renewal of our WTP NPDES
Permit, NC0084573. You should find the permit application filled out completely with
all pertinent information and diagrams requested. Since our last NPDES permit
renewal, Lincoln County is in the process of expanding the current Water Treatment
Plant from 3.99 MGD to 8.0 MGD under Water System #NC0155035 ATC Serial #17-
01100 (dated January 31, 2018).
The Operator in Responsible Charge is Mr. Adam Jolicoeur and his contact information
is:
Adam Jolicoeur
7674 Tree Farm Road
Denver, NC 28037
(704) 483 — 7070 Office
(704) 483 — 7072 Fax
[e-mail]
If you have any further questions, please feel free to contact me at your convenience.
Sincerely,
�C
Chris Henderson
Senior Engineering Associate
o. 704-736-8495 [e-mail]
O f. 704-736-8499
O 115 WEST MAIN STREET I LINCOLNTON NC 28092

NPDES PERMIT APPLICATION - SHORT FORM C - WTP
For discharges associated with water treatment plants
Mail the complete application to:
NCDEQ / DWR / NPDES
1617 Mail Service Center, Raleigh, NC 27699-1617
NPDES Permit Number INCO084573
If you are completing this form in computer use the TAB key or the up - down arrows to move from one
field to the next. To check the boxes, click your mouse on top of the box. Otherwise, please print or type.
1. Contact Information:
Owner Name Lincoln County
Facility Name Lincoln County WTP
Mailing Address 115 West Main Street
ix Lc D
City Lincolnton
State / Zip Code NC 28092
JAN 137 0 0
Telephone Number [phone]
KDEWWRIMES
Fax Number [phone]
e-mail Address [e-mail]
2. Location of facility producing discharge:
Check here if same as above ❑
Street Address or State Road 7674 Tree Farm Lane
City Denver
State / Zip Code NC 28037
County Lincoln
3. Operator Information:
Name of the firm, consultant or other entity that operates the facility.
(Note that this is not referring to the
Operator in Responsible Charge or ORC)
Name Lincoln County
Mailing Address 115 West Main Street
City Lincolnton
State / Zip Code NC 28092
Telephone Number [phone]
Fax Number [phone]
4. Ownership Status:
Federal❑ State ❑ Private ❑ Public X❑
Page 1 of 3 Version 6/2017

NPDES PERMIT APPLICATION - SHORT FORM C - WTP
For discharges associated with water treatment plants
5. Type of treatment plant:
X❑ Conventional (Includes coagulation, flocculation, and sedimentation, usually followed by
filtration and disinfection)
❑ Ion Exchange (Sodium Cycle Cationic ion exchange)
❑ Green Sand Filter (No sodium recharge)
❑ Membrane Technology (RO, nanofiltration)
Check here if the treatment process also uses a water softener ❑
6. Description of source water(s) (i.e. groundwater, surface water)
Surface Water
7. Describe the treatment process(es) for the raw water:
Conventional Treatment. The Raw Water is taken from Lake Norman and injected with alum and
sodium hypochlorite (Miox). It then passes through the flocculators, across sedimentation
basins. Then it's filtered through multi -media filters. Prior to the filters, sodium hypochlorite
(Miox) is injected. The Finished Water is injected with sodium hypochlorite (Miox), sodium
hydroxide, fluoride, and orthophosphate.
8. Describe the wastewater and the treatment process(es) for wastewater generated by the
facility:
The Backwash Water and Sludge from the sedimentation basins are sent to the thickeners. The
solids are settled out; the supernate is discharged to the lake. From the thickners, the sludge is
mixed with polymer, and then it's processed through the Huber Screw Press. The dried cake is
transferred by conveyor to a dumpster; once full it is sent to the County Landfill for use as fill
dirt.
9. Number of separate discharge points: 1 Outfall Identification number(s) 1
10. Frequency of discharge: Continuous ❑ Intermittent X❑
If intermittent:
Days per week discharge occurs: Daily Duration:
2 hours
11. Plant design potable flowrate 8.0 MGD
Backwash or reject flow .09 MGD
12. Name of receiving stream(s) (Provide a map showing the exact location of each outfall, including
latitude and longitude):
Little Creek Cove -Lake Norman/Catawba River Basin
13. Please list all water treatment additives, including cleaning chemicals or disinfection
treatments, that have the potential to be discharged.
Alum / aluminum sulfate Yes X No
Page 2 of 3 Version 6/2017

NPDES PERMIT APPLICATION - SHORT FORM C - WTP
For discharges associated with water treatment plants
Iron sulfate / ferrous sulfate Yes No X
Fluoride Yes X No
Ammonia nitrogen / Chloramines Yes No X
Zinc -orthophosphate or Sweetwater CP1236 Yes No X
List any other additives below:
Orthophosphate, Sodium Hypochlorite, Sodium Hydroxide, Sodium Thiosulphate
14. Is this facility located on Indian country? (check one)
Yes ❑
No X❑
15. Additional Information:
Provide a schematic of flow through the facility, include flow volumes at all points in
the water treatment process. The plan should show the point[s] of addition for
chemicals and all discharges routed to an outfall [including stormwater].
Solids Handling Plan
16. NEW Applicants
Information needed in addition to items 1-15:
New applicants are strongly recommended to contact a permit coordinator with the
NCDENR Customer Service Center.
Was the Customer Service Center contacted? ❑ Yes ❑ No
Analyses of source water collected
Engineering Alternative Analysis
30 Discharges from Ion Exchange and Reverse Osmosis plants shall be evaluated using a
water quality model.
17. Applicant Certification
I certify that I am familiar with the information contained in the application and that to the
best of my knowledge and belief such information is true, complete, and accurate.
Donald V. Chamblee, Jr.
Printed name of Person Signing
Signature of Applicant
Director of Public Works
Title
Date
North Carolina General Statute 143-215.6 (b)(2) provides that: Any person who knowingly makes any false statement representation, or certification in any application,
record, report, plan, or other document files or required to be maintained under Article 21 or regulations of the Environmental Management Commission implementing that
Article, or who falsifies, tampers with, or knowingly renders inaccurate any recording or monitoring device or method required to be operated or maintained under Article 21
or regulations of the Environmental Management Commission implementing that Article, shall be guilty of a misdemeanor punishable by a fine not to exceed $25,000, or by
imprisonment not to exceed six months, or by both. (18 U.S.C. Section 1001 provides a punishment by a fine of not more than $25,000 or imprisonment not more than 5
years, or both, for a similar offense.)
Page 3 of 3 Version 6/2017

LINCOLN COUNTY WATER TREATMENT PLANT
PROCESS FLOW SCHEMATIC DIAGRAM
LAKE NORMAN
I
7WATER INTAKE &
PUMP STATION
8.0 MGD
Pre -Disinfection
ALUM
PRE -CAUSTIC
RAPID MIX
FLOCCULATION
SEDIMENTATION BASINS
1,000,000 gallons
WASTE (Alum Sludge)
SOLIDS 30
PRE -FILTER Disinfection
FILTER
FILTRATION
BACKWASH 30,
8 Filters
THICKENERS
ORTHOPHOSPHATE
FLOU RI DE
189,0000 189,0000
CAUSTIC
Gallons Gallons
POST Disinfection
Clearwel Is
1 1 1
Million Million Million
Gallon Gallon Galln
HIGH SERVICE PUMPS
(3) H.S. Pump 5 mgd
TO LINCOLN COUNTY
WATER DISTRIBUTON SYSTEM
SOLIDS DEWATERING
HUBER SCREW PRESS
I
LANDFILL OR LAND APPLICATION
DISPOSAL
NPDES Permit No. NCO084573
(Sodium Thiosulphate
W DISCHARGE TO LAKE
-� (Average flow 77,000 GPD)
Department of Public Works
Water Treatment

r
LINCOLN COUNTY
WATER TREATMENT PLANT
RESIDUALS MANAGEMENT PLAN
.dune 2012
Preparers by
GOODWYN, MILLS AND CAWOOD, INC.
2660 EastCkase Lane, Suite 200
Montgomery, Alabama 36117
1 0000WYN II ILLS C.AW00P
I'1 I F G'•A7 F 1+ I�:S+ 11•14r1FS V1; 0'•I N SOL Ii I I[7.15

TREATMENT MODIFICATIONS
The intent of the design of the proposed improvements is to comply with all requirements of DENR • Pu6lic Water
Supply Section 15Ao 18C.0300 - 18C.0700. The improvements do not modify the direct flow of the water through the
process, and will continue to follow the conventional surface water filtration process, The nota6le improvements to the
sludge handling facility are modifications to the gravity thickeners, new polymer feed system, installation of progressive
cavity pumps with smart stator technology followed 6y an energy -efficient screw press, and conveyors to transfer
dewatered solids to a durnpster or open Led truck. All filtrate and process wastewater is returned to the existing yard
drain pump station to be treated through the solids handling process, All decant from the gravity thickeners exits
through the floating decant arms and flow is hydraulically controlled 6y electrically actuated valves. Prior to final
discharge, all decant is dechlorinated with a dechlorinating agent to comply with current chlorine residual concentrations
per the existing NDPES permit.
Gravity Thickeners
The existing gravity thickeners are being retrofitted with a center column cage with two steel rake arms driven 6y a
continuous torque standard shaft I HP drive. The rake arms will have adjustable 304 stainless steel squeegees to
scrape the hottom of the tank. The existing tanks will 6e grouted to submerge the 8" withdrawal line and provide a
sump for sludge removal. The gravity thickeners will also receive floating decanters which consist of an 8" diameter
schedule 40, 304 stainless steel pipe with twenty (20) 2" diameter orifices with foam core floats attached to the
decant pipe. The decant pipe will float with the water level and primarily controlled 6y the electrically actuated valve.
The low water and high water level in the gravity thickener shall 6e 799.22' and 812.60', respectively, providing 1, of
free board in each thickener.
ProgressiveCavity Pumps
A sludge handling building will be constructed to house the dewatering feed pumps, dewatering mechanism and
conveyance system. As sludge exits the gravity thickeners, sludge can either enter the existing dewatering system
for redundancy or enter the new dewatering system 6y simply operating two manual valves outside the existing
sludge dewatering building. Sludge will enter the new sludge handling 6uilding into a header reducing down to 3"
prior to entering the feed pumps. The design will utilize progressive cavity pumps to pump the settled sludge from
the thickeners to a screw press. The progressive cavity pumps are designed to pump 6 to 20 GPM at a solids
content of 0.8 to 1.2% with a 3 HP motor.
Screw Press and Conveyance System
The screw press was piloted and studied extensively on -site at the Lincoln County Water Treatment Plant using
alum sludge from the current process in place for treated potable water. During the pilot, the feed solid
concentration to the screw press ranged from 0.8 to 1.2%. It was determined that at a flow rate of 4 GPM, the
screw handled 20 pounds per hour of dry solids. The cake produced was 24.6% dry solids. The maximum
throughput of the screw press is 45 pounds per dry solids at 8 GPM; however, the cake produced was only 20`Yo dry

solids. The screw press will be rated to handling 40 to 90 pounds per hour of dry solids at 8 to 16 GPM producing
20 to 25% drysolids. After the dewatering process, cake solids will 6e conveyed through a series of four (4) shafted
screw conveyors to lift the solids to he discharged into a dumpster in a cover Lay.
Chemical Feed System
Prior to sludge entering the screw press, polymer is introduced to assist with dewatering. Neat polymer will he
dosed into an aging tank with a peristaltic pump. A 500-gallon aging tank will 6e utilized to create Latches of dilute
polymer. The chemical feed system is outfitted with a mixer to provide a complete mix system as well as a site glass
to monitor consistency of dilute polymer make up. Dilute polymer will then be fed to the screw press with a
duty/standy-6y progressive cavity pump solely used for dilute polymer. The polymer will 6e injected downstream of
the sludge feed polymer pumps and prior to a 2" check valve designed specifically for mixing. A detention time of
45 seconds has Leen provided 6etween the point of polymer injection and the screw press inlet so that the polymer
can activate and optimally assist in dewatering.
CONCLUSION
All aforementioned equipment was installed to improve the current process of dewatering solids. The existing gravity
thickeners did not have a mechanical thickening mechanism; therefore, with this addition, it can he assumed that the feed
solids from the thickeners will he greater than the range observed in the pilot. Furthermore, the decanting arm will assist
in assuring that a quality clarified supernate in the thickener is decanted. Previously, the peripheral decant lines were
fixed withdrawing at a fixed elevation with no indication to the location of the sludge blanket. The progressive cavity and
screw press tandem was selected due to the performance displayed in the pilot, efficiency and relia6le operation as well
as ease of operation and maintenance. A shafted conveyor was selected to lift solids because of the simplicity of the
conveyors. The designed system provides redundancy as well as flexibility. All unit operations have a minimum of two
installations or the a6ility to he expanded to two installations. The sludge handling facility will 6e expanda6le and can
receive two additional progressive cavity pumps and screw presses as the need for solids handling increases. For the
interim, the existing sludge handling system will he left in full working order if back up is needed.
The proposed system was designed to meet the clients need with regard to redundancy, capacity, efficiency and
reliability for current and future demands. With this proposed system, the Lincoln County f u6}ic Works Lincoln
County Water Treatment Plant will ke able to produce the desired 3.999 MGD with a method for sludge dewatering
to handle the volume of sludge holing produced by the sedimentation and filtration processes.
Also, the existing vacuum drying Led will remain intact for redundancy of sludge removal. The existing quick disconnect
from the sludge thickeners will also remain in place. Thus, the operator can utilize the drying bed as necessary or may
haul wet sludge. The design will allow for a system where the operator has three (3) options of processing sludge.

Sludge Handling System
Lincoln County Water Treatment Plant Recommended Operations Protocol
1.0 OBJECTIVE
The intent of the sludge handling operations at the Lincoln County Water Treatment Plant is to
provide solids handling of alum sludge in an efficient manner. In addition, the sludge handling
system protocol shall provide the operations staff methods and recommended procedures to
properly and efficiently operate the system described herein.
2.0 SCOPE
The sludge handling system provided is a combination of unit operations including two solids
thickeners, one positive displacement feed pump, a polymer system, and one dewatering press,.
The previous method of dewatering was a vacuum drying bed; however the County determined
that it was critical that the process no longer be weather dependent. The new sludge handling
system provides a process that requires minimal power and delivers processed solids at a percent
solids concentration acceptable for delivery to the local landfill. The sludge must meet the
requirements of the landfill and pass the paint filter liquids test. Additional optimization of the
solids handling system shall be as determined to be sensible by the operator.
3.0 SYSTEM DESCRIPTION
The equipment basis of design for the sludge handling system consists of the following unit
operations:
1. Thickeners (Westech)
a. The thickeners allow the operator to improve the consistency and solids content of
the sludge prior to conveyance to the dewatering process
2. Progressive Cavity Pump (Seepex)
a. The progressive cavity pump provides the required positive displacement,
metered flow pattern required for sludge processing
3. Polymer Feed System (Acrison)
a. The polymer system is a batch makeup system that is controlled locally by level
b. The Huber programmable logic control (PLC) provides a signal for startup and for
the feed pumps to deliver the necessary polymer dose to the sludge
4. Screw Press (Huber)
a. The screw press dewaters the sludge to a cake product
5. Conveyance (Custom Conveyors)
a. The conveyors transport dewatered cake to an owner selected dewatering bin
The Westech thickeners, Seepex feed pump, Acrison polymer system, Huber screw press, and
Huber conveyors work together to provide a complete process.
4.0 OPERATION
2

Sludge Handling System
Lincoln County Water Treatment Plant Recommended Operations Protocol
4.1 Thickeners
The sludge thickener mechanisms and their operation are critical in the success of the solids
dewatering process. The thickeners are fit with mechanical thickening devices at the bottom of
the conical tanks. The bottom of the conical tanks, where the 8 inch diameter effluent sludge
pipe is located, is at approximate elevation of 780 feet. The grade elevation at the tanks is
approximately 798 feet, thus the depth at which sludge can accumulate is upward of 18 vertical
feet. In addition, the decant mechanism for the water allows for the decanting of the tank to a
low water level (LWL) of near elevation 799. The top of wall of the sludge thickeners is near
814.8 allowing for over 13 feet of wastewater from the water treatment plant to accumulate from
the backwashing of filters and the removal of solids in the sedimentation process.
The operation of the sludge thickeners is critical to the dewatering process. The operator
controls the thickness of the solids with the rotating thickener and the available pressure (head)
in the tanks. The water level in the tank feeding the sludge dewatering process provides
backpressure on the sludge feed pumps. The 8 inch diameter sludge feed line operated at flow
rates between 8 and 20 gallons per minute provides little frictional headless in the pipe due to
velocity. The velocity of the sludge in the 8 inch pipe at 20 gallons per minute is near 0.13 feet
per second. However, the thixotropic properties of the sludge may create difficulties when
starting the dewatering process, specifically when it has not been operational for periods greater
than 12 hours.
4.2 Progressive Cavity Pump and Polymer System
The sludge feed pump suction is located at approximate elevation of 801.5 feet. Thus, the
operator shall, at a minimum, allow for the pumps to have a flooded suction. For operation of
the dewatering system, the tank from which the operator elects to process solids should have a
water level sufficient to overcome the head loss, which is minimal due to the low velocity in the
8 inch pipe, and the viscous/thixotropic properties of the sludge._ The pressure of the tanks
should read on the pressure gauge on the suction side of the pump to indicate to the operator that
sufficient head is present for beginning the dewatering process. It is recommended that the tank
water level be at a minimum elevation of 805 feet for the startup of the dewatering system.
Continuous use by the operator and logging of startup data should allow the operator to increase
or decrease this water level for startup dependent upon the comfort level with the sludge
consistency and backpressure on the pump.
Upon process initiation, the sludge (plug) valve from the thickener which is to be utilized for
sludge dewatering shall be opened. The operator shall fluidize the influent sludge line by turning
on the water connection at the suction of the pump. The water will provide lubrication of the pipe
for improved sludge conveyance.
3

Sludge Handling System
Lincoln County Water Treatment Plant Recommended Operations Protocol
The pressure gauge on the suction side of the pump shall be utilized to determine when sufficient
head pressure has built up behind the pump for startup. The operator may replace the existing
pressure gauge with a combination vacuum gauge to insure that a vacuum has not been created,
thereby protecting the progressive cavity pumps from running dry. The operator may elect to
wait until adequate sludge consistency is being conveyed to the screw press before initiating
polymer system injection.
Reducing the polymer injection prior to the sludge becoming consistency may waste costly
polymer. Once the sludge is actively being conveyed in the piping system, the polymer injection
can be initiated. All water and inconsistent sludge content prior to polymer injection and the
dewatering of the sludge shall flow as designed to the yard drain pump station that recycles the
contents to the thickener.
Additional flushing quick connections near the thickener on the conveyance piping are
recommended should plugging of the line become frequent during shut down periods. Existing
connections to the 8 inch pipe make this connection easily constructed and the conveyance line
cleared with the water pressure of the line. The thickener level must be elevated to force the
water pressure to move and lubricated around the sludge travelling toward the pump, in lieu of
simply filling the tank where the pressure may be lower.
4.3 Screw Press and Conveyance
After initiation of the process and confirmation of active sludge movement with consistency, the
process may then be operated and controlled by the Huber controller. The controller is designed
to operate the polymer system, dewatering system and dried solids conveyance system.
5.0 SYSTEM TERMINATION
Process termination is another critical component of the operations. Due to the known properties
of water treatment sludge, issues may develop in the feed piping that cause difficulties during the
subsequent startup. Operators shall fluidize the sludge feed line, and process sludge to the drain
through the screw press._ The wasted water and sludge will then be recycled back to the
thickener through the yard drain pump station. The feed line pressure gauge shall be monitored
and the pressure supplied by the water should increase the pressure in the line to indicate good
fluidization.
6.0 TESTING AND REPORTING
It is recommended that multiple data entries be logged with each startup. These factors will aid
in the optimization of the process not only by present operators but by future operations staff.
The entries should include, but not be limited to:
1. Thickener utilized for dewatering process (I or 2);
4

Sludge Handling System
Lincoln County Water Treatment Plant Recommended Operations Protocol
2. Water elevation in thickener at startup;
3. Time between shutdown and startup;
4. Percent solids influent;
5. Polymer usage;
6. Average sludge flow rate;
7. Percent solids processed;
8. Process run time;
9. Faults encountered during processing;
10. Total sludge volume processed;
11. Thickener run times; and
12. Sludge line pressure.
Data logging, whether in the PLC or in tabular form, allows operators to constructively
troubleshoot. Process optimization is made more efficient, and quality information becomes
readily accessible to management purposes.- Many other data points should also be evaluated
and the operator should use good judgment in determining the necessary additional points to
monitor.
The operator shall utilize the data log to make decisions on the run times for the thickener
mechanisms._ It is likely that the thickener should not be run at all times, as the thickening of the
alum sludge when not processing solids may create a consistency that is difficult to convey and
process. _In addition, the solids may be forced into the lower elevations of the pipe between the
thickener and the feed pump and become consolidated creating problems for the subsequent
startup. Other actions that aids in the clearing of this sludge line are the flushing of the line prior
to process termination and utilizing the available head pressure in the tanks to feed the pumps.
Modifications to the sludge handling process operations protocol shall be made as data becomes
available for analysis. Improved comprehension of the specific installation through the data
collected shall provide improved operations.
u ►AUf
The sludge handling system shall be operated to meet the requirement for delivery of the
dewatered product to the local landfill. The operations staff must be cognizant of the
aforementioned items to provide a system that functions properly and efficiently as designed.
Data shall be recorded and tracked so that changes can be made to the sludge handling system. It
is recommended that process changes be made immediately when the sludge handling system is
not operating as intended. These changes shall be at the discretion of the operator responsible
for the system at that time. Efficient sludge handling operations at the Lincoln County Water
Treatment Plant is an integral process to the overall treatment process and shall be operated with
the recommendations provided, data collected and experience gained while the sludge handling
system is in operation.
5

LINCOLN COUNTY WATER TREATMENT PLANT
SLUDGE HANDLING SYSTEM
RECOMMENDED OPERATIONS PROTOCOL
Date: 5/15/14

Sludge Handling System
Lincoln County Water Treatment Plant Recommended Operations Protocol
1.0 OBJECTIVE
The intent of the sludge handling operations at the Lincoln County Water Treatment Plant is to
provide solids handling of alum sludge in an efficient manner. In addition, the sludge handling
system protocol shall provide the operations staff methods and recommended procedures to
properly and efficiently operate the system described herein.
2.0 SCOPE
The sludge handling system provided is a combination of unit operations including two solids
thickeners, one positive displacement feed pump, a polymer system, and one dewatering press,.
The previous method of dewatering was a vacuum drying bed; however the County determined
that it was critical that the process no longer be weather dependent. The new sludge handling
system provides a process that requires minimal power and delivers processed solids at a percent
solids concentration acceptable for delivery to the local landfill. The sludge must meet the
requirements of the landfill and pass the paint filter liquids test. Additional optimization of the
solids handling system shall be as determined to be sensible by the operator.
3.0 SYSTEM DESCRIPTION
The equipment basis of design for the sludge handling system consists of the following unit
operations:
1. Thickeners (Westech)
a. The thickeners allow the operator to improve the consistency and solids content of
the sludge prior to conveyance to the dewatering process
2. Progressive Cavity Pump (Seepex)
a. The progressive cavity pump provides the required positive displacement,
metered flow pattern required for sludge processing
3. Polymer Feed System (Acrison)
a. The polymer system is a batch makeup system that is controlled locally by level
b. The Huber programmable logic control (PLC) provides a signal for startup and for
the feed pumps to deliver the necessary polymer dose to the sludge
4. Screw Press (Huber)
a. The screw press dewaters the sludge to a cake product
5. Conveyance (Custom Conveyors)
a. The conveyors transport dewatered cake to an owner selected dewatering bin
The Westech thickeners, Seepex feed pump, Acrison polymer system, Huber screw press, and
Huber conveyors work together to provide a complete process.
4.0 OPERATION
2
I

Sludge Handling System
Lincoln County Water Treatment Plant Recommended Operations Protocol
4.1 Thickeners
The sludge thickener mechanisms and their operation are critical in the success of the solids
dewatering process. The thickeners are fit with mechanical thickening devices at the bottom of
the conical tanks. The bottom of the conical tanks, where the 8 inch diameter effluent sludge
pipe is located, is at approximate elevation of 780 feet. The grade elevation at the tanks is
approximately 798 feet, thus the depth at which sludge can accumulate is upward of 18 vertical
feet. In addition, the decant mechanism for the water allows for the decanting of the tank to a
low water level (LWL) of near elevation 799. The top of wall of the sludge thickeners is near
814.8 allowing for over 13 feet of wastewater from the water treatment plant to accumulate from
the backwashing of filters and the removal of solids in the sedimentation process.
The operation of the sludge thickeners is critical to the dewatering process. The operator
controls the thickness of the solids with the rotating thickener and the available pressure (head)
in the tanks. The water level in the tank feeding the sludge dewatering process provides
backpressure on the sludge feed pumps. The 8 inch diameter sludge feed line operated at flow
rates between 8 and 20 gallons per minute provides little frictional headless in the pipe due to
velocity. The velocity of the sludge in the 8 inch pipe at 20 gallons per minute is near 0.13 feet
per second. However, the thixotropic properties of the sludge may create difficulties when
starting the dewatering process, specifically when it has not been operational for periods greater
than 12 hours.
4.2 Progressive Cavity Pump and Polymer System
The sludge feed pump suction is located at approximate elevation of 801.5 feet. Thus, the
operator shall, at a minimum, allow for the pumps to have a flooded suction. For operation of
the dewatering system, the tank from which the operator elects to process solids should have a
water level sufficient to overcome the head loss, which is minimal due to the low velocity in the
8 inch pipe, and the viscous/thixotropic properties of the sludge._ The pressure of the tanks
should read on the pressure gauge on the suction side of the pump to indicate to the operator that
sufficient head is present for beginning the dewatering process. It is recommended that the tank
water level be at a minimum elevation of 805 feet for the startup of the dewatering system.
Continuous use by the operator and logging of startup data should allow the operator to increase
or decrease this water level for startup dependent upon the comfort level with the sludge
consistency and backpressure on the pump.
Upon process initiation, the sludge (plug) valve from the thickener which is to be utilized for
sludge dewatering shall be opened. The operator shall fluidize the influent sludge line by turning
on the water connection at the suction of the pump. The water will provide lubrication of the pipe
for improved sludge conveyance.
3

L__ f
Sludge Handling System
Lincoln County Water Treatment Plant Recommended Operations Protocol
The pressure gauge on the suction side of the pump shall be utilized to determine when sufficient
head pressure has built up behind the pump for startup. The operator may replace the existing
pressure gauge with a combination vacuum gauge to insure that a vacuum has not been created,
thereby protecting the progressive cavity pumps from running dry. The operator may elect to
wait until adequate sludge consistency is being conveyed to the screw press before initiating
polymer system injection.
Reducing the polymer injection prior to the sludge becoming consistency may waste costly
polymer. Once the sludge is actively being conveyed in the piping system, the polymer injection
can be initiated. All water and inconsistent sludge content prior to polymer injection and the
dewatering of the sludge shall flow as designed to the yard drain pump station that recycles the
contents to the thickener.
Additional flushing quick connections near the thickener on the conveyance piping are
recommended should plugging of the line become frequent during shut down periods. Existing
connections to the 8 inch pipe make this connection easily constructed and the conveyance line
cleared with the water pressure of the line. The thickener level must be elevated to force the
water pressure to move and lubricated around the sludge travelling toward the pump, in lieu of
simply filling the tank where the pressure may be lower.
4.3 Screw Press and Conveyance
After initiation of the process and confirmation of active sludge movement with consistency, the
process may then be operated and controlled by the Huber controller. The controller is designed
to operate the polymer system, dewatering system and dried solids conveyance system.
5.0 SYSTEM TERMINATION
Process termination is another critical component of the operations. Due to the known properties
of water treatment sludge, issues may develop in the feed piping that cause difficulties during the
subsequent startup. Operators shall fluidize the sludge feed line, and process sludge to the drain
through the screw press._ The wasted water and sludge will then be recycled back to the
thickener through the yard drain pump station. The feed line pressure gauge shall be monitored
and the pressure supplied by the water should increase the pressure in the line to indicate good
fluidization.
6.0 TESTING AND REPORTING
It is recommended that multiple data entries be logged with each startup. These factors will aid
in the optimization of the process not only by present operators but by future operations staff.
The entries should include, but not be limited to:
1. Thickener utilized for dewatering process (1 or 2);
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Sludge Handling System
Lincoln County Water Treatment Plant Recommended Operations Protocol
2. Water elevation in thickener at startup;
3. Time between shutdown and startup;
4. Percent solids influent;
5. Polymer usage;
6. Average sludge flow rate;
7. Percent solids processed;
8. Process run time;
9. Faults encountered during processing;
10. Total sludge volume processed;
11. Thickener run times; and
12. Sludge line pressure.
Data logging, whether in the PLC or in tabular form, allows operators to constructively
troubleshoot. Process optimization is made more efficient, and quality information becomes
readily accessible to management purposes.- Many other data points should also be evaluated
and the operator should use good judgment in determining the necessary additional points to
monitor.
The operator shall utilize the data log to make decisions on the run times for the thickener
mechanisms._ It is likely that the thickener should not be run at all times, as the thickening of the
alum sludge when not processing solids may create a consistency that is difficult to convey and
process. -In addition, the solids may be forced into the lower elevations of the pipe between the
thickener and the feed pump and become consolidated creating problems for the subsequent
startup. Other actions that aids in the clearing of this sludge line are the flushing of the line prior
to process termination and utilizing the available head pressure in the tanks to feed the pumps.
Modifications to the sludge handling process operations protocol shall be made as data becomes
available for analysis. Improved comprehension of the specific installation through the data
collected shall provide improved operations.
7.0 SUMMARY
The sludge handling system shall be operated to meet the requirement for delivery of the
dewatered product to the local landfill. The operations staff must be cognizant of the
aforementioned items to provide a system that functions properly and efficiently as designed.
Data shall be recorded and tracked so that changes can be made to the sludge handling system. It
is recommended that process changes be made immediately when the sludge handling system is
not operating as intended. These changes shall be at the discretion of the operator responsible
for the system at that time. Efficient sludge handling operations at the Lincoln County Water
Treatment Plant is an integral process to the overall treatment process and shall be operated with
the recommendations provided, data collected and experience gained while the sludge handling
system is in operation.
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