NC0081426_Permit Issuance_20110624

NCDENR
North Carolina Department of Environment and Natural Resources
Division of Water Quality
Beverly Eaves Perdue Coleen H. Sullins
Governor Director
June 24, 2011
Mr. Allan E. Williams, P.E., Water Resources Director
City of Greensboro
P. O. Box 3136
Greensboro, NC 27402-3136
Subject: Issuance of NPDES Permit NCO081426
City of Greensboro — N. L. Mitchell WTP
Guilford County
Dear Mr. Williams:
Dee Freeman
Secretary
Division personnel have reviewed and approved your application for renewal of the subject permit.
Accordingly, we are forwarding the attached NPDES discharge permit. This permit is issued pursuant
to the requirements of North Carolina General Statute 143-215.1 and the Memorandum of Agreement
between North Carolina and the U.S. Environmental Protection Agency dated October 15, 2007 (or as
subsequently amended).
This final permit includes no significant changes from the draft permit sent to you on April 13, 2011;
however, its terms are significantly different from those found in the current permit. You should read
the permit carefully, in order to help you maintain compliance with its terms and conditions.
Please note that North Buffalo Creek is listed as an impaired waterbody on the North Carolina 303(d)
Impaired Waters List. This means that the stream does not meet all water quality standards. Addressing
impaired waters is a high priority with the Division, and instream data will continue to be evaluated. If
there is noncompliance with permitted effluent limits and stream impairment can be attributed to your
facility, then mitigative measures may be required.
If any parts, measurement frequencies or sampling requirements contained in this permit are
unacceptable to you, you have the right to an adjudicatory hearing upon written request within thirty
(30) days following receipt of this letter. This request must be in the form of a written petition,
conforming to Chapter 150B of the North Carolina General Statutes, and filed with the Office of
Administrative Hearings (6714 Mail Service Center, Raleigh, North Carolina 27699-6714). Unless
such demand is made, this decision shall be final and binding.
Please note that this permit is not transferable except after notice to the Division. The Division may
require modification or revocation and reissuance of the permit. This permit does not affect the legal
requirements to obtain other permits which may be required by the Division of Water Quality or permits
required by the Division of Land Resources, the Coastal Area Management Act or any other Federal or
Local governmental permit that may be required.
1617 Mail Service Center, Raleigh, North Carolina 27699-1617
Location: 512 N. Salisbury St. Raleigh, North Carolina 27604 ' Noe Carolina
Phone: [phone] FAX: [phone] Customer Service:1-877-623-6748 Internet: www.newaterquality.org Natzmally
An Equal opportunity 1 Affirmative Action Employer

Mr. Alan Williams, P.E.
N. L. Mitchell WTP Permit Renewal 3011
p2
If you have any questions concerning this permit, please contact Bob Sledge at telephone number (919)
807-6398, or via e-mail at [e-mail].
Si r y,
Coleen H.
cc: Central Files
/� y
Sullins
Winston-Salem Regional Office/Surface Water Protection Section
NPDES File
ec: Aquatic Toxicology Unit
Barry Parsons
Shamika Collins

Permit NCO081426
STATE OF NORTH CAROLINA
DEPARTMENT OF ENVIRONMENT AND NATURAL RESOURCES
DIVISION OF WATER QUALITY
PERMIT
TO DISCHARGE WASTEWATER UNDER THE
NATIONAL POLLUTANT DISCHARGE ELMNATION SYSTEM
In compliance with the provision of North Carolina General Statute 143-215.1, other lawful standards
and regulations promulgated and adopted by the North Carolina Environmental Management
Commission, and the Federal Water Pollution Control Act, as amended, the
City of Greensboro
is hereby authorized to discharge wastewater from a facility located at the
N. L. Mitchell WTP
1041 Battleground Avenue
Greensboro
Guilford County
to receiving waters designated as North Buffalo Creek in the Cape Fear River Basin
in accordance with effluent limitations, monitoring requirements, and other conditions set forth in Parts
I,11, III and IV hereof.
This permit shall become effective August 1, 2011.
This permit and authorization to discharge shall expire at midnight on June 30, 2016.
Signed this day June 24, 2011.
G
COIW5. Sullins, Director
Division of Water Quality
By Authority of the Environmental Management Commission

• Permit NC0081426 •
SUPPLEMENT TO PERMIT COVER SHEET
All previous NPDES Permits issued to this facility, whether for operation or discharge are hereby
revoked. As of this permit issuance, any previously issued permit bearing this number is no longer
effective. Therefore, the exclusive authority to operate and discharge from this facility arises under the
permit conditions, requirements, terms, and provisions included herein.
The City of Greensboro
is hereby authorized to:
1. Continue to discharge filter -backwash wastewater from a conventional water treatment plant. This
facility is located at the N.L. Mitchell WTP at 1041 Battleground Avenue, in Greensboro, in
Guilford County.
2. Discharge from said treatment works at the location specified on the attached map into North
Buffalo Creek, classified C=NSW waters in the Cape Fear River Basin.
11

I N
DY I

► Permit N000811426
A. (1.) EFFLUENT LIMITATIONS AND MONITORING REQUIREMENTS - FINAL
During the period beginning on the effective date of this permit and lasting until expiration, the
Permittee is authorized to discharge from outfall 001. Such discharges shall be limited and monitored
by the Permvttee as specified below:
EFFLU;ENT-1 ...
CHARAGTERiSTICS
+ _ LIMITS
MONITORING REQUIREMENTS
Monthly
. Avera e < .
_ Dai
.Maximum° .
Measurement
__.._ ..
Fre eenc . .
Sample Type,
Sample" Locations
Flow
Continuous
Recording
Effluent
Total Suspended Solids
30.0 mg/L
45.0 mg/L
Weekly
Grab
Effluent
pH
z 6.0 s.u. ands 9.0 s.u.
Weekly
Grab
Effluent
Total Residual Chlorine'
17 /uglL
Weekly
Grab
Effluent
Turbidity
Weekly
Grab
Effluent
Aluminum
QuarterV
Grab
Effluent
Total Iron
Quarterly2
Grab
Effluent
Total Copper
Quarterly2
Grab
Effluent
Manganese
Quarterly2
Grab
Effluent
Fluoride
Quarterly2
Grab
Effluent
Ammonia Nitrogen
Quarterly2
Grab
Effluent
Total Phosphorous (TP)
Quarterly2
Grab
Effluent
Total Nitrogen (TN)
Quarterly2
Grab
Effluent
Whole Effluent Toxicity
Monitorin
Quarterly
Grab
Effluent
Footnotes:
1. The Division shall consider all effluent TRC values reported below 50 µg/L to be in compliance
with the permit. However, the Permittee shall continue to record and submit all values reported by
a North Carolina certified laboratory (including field certified), even if these values fall below 50
µme• ,
2. Monitoring should be performed in conjunction with toxicity testing.
3. Ceriodaphnia dubia 7day pass/fail test @ 90% concentration. See Condition A. (2.) for toxicity
testing requirements. Toxicity testing should be performed during the months of March, June,
September and December, and sampling should coincide with sampling for parameters covered by
footnote 2.
All samples must be collected from a typical discharge event.
There shall be no discharge of floating solids or visible foam in other than trace amounts.

Permit NCO081426
A. (2.) CHRONIC TOXICITY MONITORING (QUARTERLY)
The permittee shall conduct guarterl chronic toxicity tests using test procedures outlined in the "North
Carolina Ceriodaphnia Chronic Effluent Bioassay Procedure," Revised February 1998, or subsequent
versions.
The effluent concentration defined as treatment two in the procedure document is 90 %. The testing
shall be performed as a Ceriodaphnia dubia May pass/fail test. The tests will be performed during
the months of March, June, September and December. Effluent sampling for this testing shall be
performed at the NPDES permitted final effluent discharge below all treatment processes.
All toxicity testing results required as part of this permit condition will be entered on the Effluent
Discharge Monitoring Form (MR-1) for the month in which it was performed, using the parameter
code TGP3B. Additionally, DWQ Form AT-1(original) is to be sent to the following address:
Attention: NC DENR / DWQ / Environmental Sciences Section
1621 Mail Service Center
Raleigh, N.C. 27699-1621
Completed Aquatic Toxicity Test Forms shall be filed with the Environmental Sciences Section no
later than 30 days after the end of the reporting period for which the report is made.
Test data shall be complete and accurate and include all supporting chemical/physical measurements
performed in association with the toxicity tests, as well as all dose/response data. Total residual
chlorine of the effluent toxicity sample must be measured and reported if chlorine is employed for
disinfection of the waste stream.
Should there be no discharge of flow from the facility during a month in which toxicity monitoring is
required, the permittee will complete the information located at the top of the aquatic toxicity (AT) test
form indicating the facility name, permit number, pipe number, county, and the month/year of the
report with the notation of "No Flow" in the comment area of the form. The report shall be submitted
to the Environmental Sciences Section at the address cited above.
Should the permittee fail to monitor during a month in which toxicity monitoring is required, then
monthly monitoring will begin immediately. Upon submission of a valid test, this monthly test
requirement will revert to quarterly in the months specified above.
Should any test data from this monitoring requirement or tests performed by the North Carolina
Division of Water Quality indicate potential impacts to the receiving stream, this permit may be re-
opened and modified to include alternate monitoring requirements or limits.
If the Permittee monitors any pollutant more frequently then required by this permit, the results of such
monitoring shall be included in the calculation & reporting of the data submitted on the DMR & all AT
Forms submitted.
NOTE: Failure to achieve test conditions as specified in the cited document, such as minimum control
organism survival, minimum control organism reproduction, and appropriate environmental controls,
shall constitute an invalid test and will require immediate follow-up testing to be completed no later
than the last day of the month following the month of the initial monitoring.

News & Record
Published by
News & Record, Inc.
Greensboro, North Carolina
North Carolina, Guilford County
AFFIDAVIT OF
Before the undersigned, a Notary Public of said County and State, duly commissioned, qualified and authorized by law to
administer oaths, personally appeared the Publisher's Representative who being first duly sworn, deposed and says:
1. That he/she is the Publisher's Representative of the Greensboro News & Record, Inc. a corporation, engaged in the
publication of newspapers known as 'News & Record", published, issued and entered as second class mail in the City of
Greensboro in said County and State.
2. That he/she is authorized to make this affidavit and sworn statement; that the notice or other legal advertisement,
a copy of which is attached hereto, was published in the News & Record on the dates listed below.
3. That the said newspaper (or newspapers) in which such notice, paper, document, or legal advertisement was published
was, at the time of each and every such publication, a newspaper meeting all of the r,p4uirements and qualifications of
Section 1-597 of the General Statutes of North Capolina and was a qualifigd'n�wspa er wi hin the meaning of Section 1-59;
of the General Statutes of North Carolina. ( ) V 1
Publisher's Representative ,1. L:Lc J ��\0%t 11111111/I,,
Sworn to and subscribed befoor� this O(� day �ofl2011
+ Y+
Notary Public
Name
Ad #
Date
Edition
NCDENR DWQ NPDES
34211420
04/20/11
News & Record
Class PO Ad Copy
44 ���''%
v OTA/1
My Comm. Exp.
6/15/2014
i '°UBLIG
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covesN
400 Lake Townsen Public NoticeNorth Carolina Environmenta

Ad ID 134211420 Date 04/18/2011 Time 11:50 AM
Public Notice
Noah Carolina Emnronmertal
Management Go.... DrY
NPDES Unit
1617 Mail Serwce Center
Rafe'gl% NC 27699-1617
Notice of Intent to Isne a NPDB
Wastexeter Pemft
The North Carolina Environmental
Management Cnmmun proposes
to sam a NPDESwastewater
discharge permit to the person(s)
listed below
Written oomrerts regarding the
proposed permit wF be ao:epted
until 30 days after the publish date al'
this notice. The Director of the NC
Division of Water Quality (CIM) mey
hold a public headno should there be
oormnents and'or
s requests to DhQ atthe
non NPDES per rds and
my be found on our
The Cty of Greensboro requested
renewal of permit NC0081671 forthe
WE Townsend WrP in Guilford
Cnumy, this permitted decharW ls
tmeatEdfiterbadswah westewaterto
Reedy Fork Creek n the Cape Fear
Bier Basin
The Cis; of Greensboro requested
rerewalof pemrft NC0081426forthe
N.L Mitchell WIP in Gui ford County,
thispe— it ddrehage "streated
filter -backwash wastewaterw North
Buffalo Creek in the Cape Fear River
Basin.
Guilford County Schools requested
renewal of permit
NC003B164NathanaelGreene
Elementary. Fadrlydkchages
treated wastmaterto an unmmed
trbutaryto North Prong Stinking
Quarter CmeldCape Fear Rher Bain
Currently BOD, ammonia nitrogen,
d'ssoked otygen, fecal wliformard
total residual chlonne are water
quality linited
Qwrtersmne Farm HOArequested
renewal of permit
NC006696dQuartersbsne Farm
WAnRIGuilfond County. Fadiily
d'schagestmated wastewiterto
Buffab CreekdCape Fear Rier Ban.
Cumenthy am onia nitrogen, feral
coffonrl total nitrogen and WWl
phosphorus are walerquality limod .
Ad shown is not actual print size

FACT SHEET FOR EXPEDITED PERMIT RENEWALS
This form must be completed by Permit Writers for all expedited permits which do not require
full Fact Sheets. Expedited permits are generally simple 100% domestics (e.g., schools, mobile
home parks, etc) that can be administratively renewed with minor changes, but can include
facilities with more complex issues (Special Conditions, 303(d) listed water, toxicity testing,
instream monitoring, compliance concerns).
Basic Information for Expedited Permit Renewals
Permit Writer/Date
Bob Sledge 4/12/2011
Permit Number
NCO081426
Facility Name
City of Greensboro — N. L. Mitchell WTP
Basin Name/Sub-basin number
Cape Fear River/ 03-06-02
Receiving Stream
North Buffalo Creek
Stream Classification in Permit
C-NSW
Does permit need Daily Max NH3 limits?
No — Monitoring only
Does permit need TRC limits/language?
Yes: Add TRC language below
Does permit have toxicity testing?
Added this cycle
Does permit have Special Conditions?
Nutrients Reo ener? , 164d
Does permit have instream monitoring?
No
Is the stream impaired (on 303(d) list)? For
whatparameter?
Yes? Biological Integrity & Fecal Coliform
Any obvious compliance concerns?
No
Any permit mods since last permit?
Dechlorination
Current expiration date
June 30, 2011
New expiration date
June 30, 2016
Comments received on Draft Permit?
Yes No If Yes, discuss response with
Supervisor
Most Commonly Used Expedited Language:
• 303(d) language for Draft/Final Cover Letters: "Please note that the receiving stream
is listed as an impaired waterbody on the North Carolina 303(d) Impaired Waters List.
Addressing impaired waters is a high priority with the Division, and instream data will
continue to be evaluated. If there is noncompliance with permitted effluent limits and
stream impairment can be attributed to your facility, then mitigative measures may be
required".
• TRC language for Compliance Level for Cover Letters/Effluent Sheet Footnote:
"The Division shall consider all effluent TRC values reported below 50 µg/L to be in
compliance with the permit. However, the Permittee shall continue to record and submit
all values reported by a North Carolina certified laboratory (including field certified),
even if these values fall below 50 µg/L.."
BIMS Compliance Download: Queries>Reports>Violations>Monitor Report Violations>Limit
Violations for Past 3 Years
Reminder: Permits that are not subject to expedited renewal include the following: 1) Major
Facility (municipal/industrial); 2) Minor Municipals with pretreatment program; 3)
Minor Industrials subject to Fed Effluent Guidelines (lb/day limits for BOD, TSS, etc); 4)
Limits based on reasonable potential analysis (metals, GW remediation organics); 5)
Permitted flow > 0.5 MGD (requires full Fact Sheet); 6) permits determined by Supervisor to be
outside expedited process.
Note: This sheet is located on NPDES Server/CurentVersions/Expedited Fact Sheet May2010

Sledge, Bob
From:
Parsons, Barry[[e-mail]]
Sent:
Monday, March 28, 2011 2:27 PM
To:
Sledge, Bob
Cc:
Collins, Shameka; Drew, Steve
Subject:
RE: NPDES Permits: Mitchell S Lake Townsend WTPs
Attachments:
MSDS Corrosion Inhibitor AquaPure.doc; Discharge Flows 2010.x1sx
Bob,
The following are some answers to your questions:
1. The backwash water is chlorinated and fluoridated.
2. We do not use a zinc compound in our corrosion inhibitor. I will attach an MSDS to this email.
3. We will be feeding ammonia and chlorine tentatively starting July 25", 2011.
4. Attached are flow discharge values for Townsend filtration Plant and Mitchell Filtration Plant. Mitchell uses
decanters and sanitary sewer.
1 hope this information is helpfull Thank you.
Barry K Parsons, Interim Water Supply Manager
Department of Water Resources
City of Greensboro, NC
Desk (336)-373-7643
Main (336)-373-5855
Fax: [phone]
From: Sledge, Bob rmailto:bob.siedaeArx:denr.aovl
Sent: Monday, March 28, 20117:53 AM
To: Parsons, Barry
Subject: NPDES Permits: Mitchell & Lake Townsend WTPs
HI Mr. Parsons,
My name is Bob Sledge and I work in a compliance and permitting unit within the Division of Water Quality. I've
been given the task of managing the reissuance of the wastewater discharge permits for your two facilities. The
reissuing of these permits should be pretty easy, but the final results will be different from earlier permits
because the Division has instituted a new strategy for permitting of discharges from conventional water
treatment plants. To that end, I was hoping you could answer a few questions regarding operations at these
plants. I've looked at the diagrams you provided in the renewal applications, but wanted to make sure of a few
things instead of making wrong assumptions.
Do these plants use finished, potable water for the backwashing of filters? Is the backwash water chlorinated
and/or fluoridated?
Do these facilities use zinc orthophosphate (or any other zinc compound) as a corrosion inhibitor?
Do these facilities ever use chloramines as a secondary form of disinfection?
It appears that each of these facilities discharge to their receiving streams just downstream of the dam release
from the reservoir. Do you know if a minimum release rate has been established from the reservoirs to ensure
there is a constant flow downstream? If so, can you provide me with those flow values?
With your answers, I should be able to send you draft versions of the permits within the next few weeks. Thank
you for your help in these matters.
Bob
Bob Sledge
Environmental Specialist
Compliance & Expedited Permits Unit
NC Division of Water Quality
bob.sledeeC ncderingov
[phone]
E-mail correspondence to and from this address may be subject to the North Carolina (Public Records Law and
may be disclosed to third parties.
Please note that email sent to and from this address is subject
to the North Carolina Public Records Law and may be disclosed to
third parties.

r City of Greensboro
, I North Carolina
December 6, 2010
Dina Sprinkle
NC DENR/DWQ/Point Source Branch
1617 Mail Service Center
Raleigh, NC 27699-1617
Dear Mrs. Sprinkle:
This letter is to request renewal of an existing NPDES permit. Please find enclosed a completed
permit renewal package for the City of Greensboro's N.L. Mitchell Water Treatment Plant —
NPDES permit, No. NC0081426. Since the current permit was issued, the plant has converted to
ferric sulfate as the primary coagulant.
If you should need any additional information, please contact Interim Water Supply Manager at
336-373-7643.
Sincerely,
Allan E. Williams, PE
Director of Water Resources
Cc: COGWR File
Enclosures
P.O. Box 3136 Greensboro, NC 27402.3136 www.greensboro-ne.gov (336) 373-CITY (2489) TTY # 333-6930

NPDES PERMIT APPLICATION - SHORT FORM C - WTP
For discharges associated with water treatment plants
Mail the complete application to:
N. C. Department of Environment and Natural Resources
Division of Water Quality I NPDES Unit
1617 Mail Service Center, Raleigh, NC 27699-1617
NPDES Permit Number INCO081426
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
City of Greensboro
Facility Name.
N.L. Mitchell Water Treatment Plant
Mailing Address
PO Box 3136
City
Greensboro
State / Zip Code
North Carolina 27402-3136
Telephone Number
[phone]
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 1041 Battleground Avenue
City
Greensboro
State / Zip Code
North Carolina 27408
County
Guilford
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. Barry Parsons
Mailing Address 6268 Bryan Park Road 4 '
City Brown Summit
State / Zip Code North Carolina 27214-9755
Telephone Number [phone] —�
Fax Number [phone]
4. Ownership Status:
Federal ❑ State ❑ Private ❑ Public
5. Type of treatment plant:
Page 1 of 3 C-WTP 03105

NPDES PERMIT APPLICATION - SHORT FORM C - WTP
For discharges associated with water treatment plants
® 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 (Lake Brant)
7. Describe the treatment process(es) for the raw water:
The treatment process is coagulation floculation using ferric sulfate as the primary
coagulant entering sedimentation basins, followed by filters and then disinfected with
sodium hypochlorite.
S. Describe the wastewater and the treatment process(es) for wastewater generated by the
facility:
Settling and Decanting
9. Number of separate discharge points: 1
Outfall Identification number(s) 001
10. Frequency of discharge: Continuous ® Intermittent ❑
If intermittent:
Days per week discharge occurs: Duration:
11. Plant design potable flowrate 24 MGD
Backwash or reject flow 180,567 MGD
12. Name of receiving stream(s) (Provide a map showing the exact location of each outfall, including
latitude and longitude
North Buffalo Creek Outfall is at: N 36degrees 04.876, W 079degrees 48.216'
13. Please list all water treatment additives, including cleaning chemicals or disinfection
treatments, that have the potential to be discharged.
Page 2 of 3 C-WTP 03/05

NPDES PERMIT APPLICATION - SHORT FORM C - WTP
For discharges associated with water treatment plants
Ferric Sulfate
Sodium Hypochlorite
Sodium Hydroxide
Hydrofluoricic Acid
Calcium Hydroxide
14. Is this facility located on Indian country? (check one)
Yes ❑ No
15. Additional Information:
Provide a schematic of flow through the facility, include flow volumes at all points in
the treatment process, and point of addition of chemicals.
Solids Handling Plan
16. NEW Applicants
Information needed in addition to items 1-15.
New applicants must 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
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.
Allan E. Williams, PE Water Resources Director
Printed name of Person Signing Title
Signature of
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 C-WTP 03/05

0 0.3 0.6 0.9 1.2 1.5 km
G
0 0.2 0.4 0.6 0.8 1 mi
Map center is UTM 17 607727E 3993629N (WGS84/NAD83)
Greensboro quadrangle M=-8.088
Projection is UTM Zone 17 NAD83 Datum G=0.705
L a C:-A71Q1V-, IV 361" 04. 8'761
W 07TO 4!9.,2 i6'

itchell Water Treatment
Lake Brandt Pumping
Lake Brendl Statbn
Raw Water Source Sodium
Permanganate
uorlde Chlorine
Bulk
] �
a storage Storage
Seminole
Sedimentation
Basins
Settled
Sample
Point
Lake Dan
11 Million Gallon
Storage
0
Water to
Floc
Sample
Pant
Filters 1.6
f lter
3ainple
Poim
Calcium Thiosulfato
Lake Dan
Mitchell Ptnnpi g
Station
from Lake Dan
Filters 7.12
Phosphate
Lime
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Air Harbor
Settli
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Chemical Feed
To All Filters
Caustic
Q Chlorine
Battleground
SedknernWOtt
Basins
ISetllod
Sample
Point
Floc
Sample
Point
Raw
Sample
Point
Clearvxg
3 Million Gallon
Storage
Chemical Feed Pants
Sodium Permanganate
Q
Aluminum Sulfate (Alum)
Q
Sodium Hypochlorilo {Chlorine)
Sodium Hydroxide (Caustic)
Q
Hydroflu°rosilcic Acid (Fiuonde)
®
Common Inhibitor (Phosphate)
Q
Umo Slurry (Lime)
Q
Ammonia (Future)
Q
Potyaiuminum Chloride (PAX 18)
Calcium Thiosulfate

FA_
City of Greensboro
L I North Carolina
Addendum
Sludge Management Plan
The City of Greensboro's Mitchell Water Treatment Plan is a conventional surface water
treatment facility permitted to treat (filter) 24 million gallons of water per day (MGD). The water
produced by the facility meets all applicable State and Federal standards. The current average
daily production at the facility is 14 MGD.
All filter backwash wastewater from the facility flows to a settling basin on the plant site. Filter
backwash flow is intermittent based on plant treatment rate and raw water quality conditions.
The wastewater -settling basin allows for gravity settling of captured solids and is equipped with
four floating decanters, which removes fine solids prior to discharge. As filter backwash flows
through the settling basin, solids removed during the treatment process (consisting primarily of
Ferric Sulfate precipitate and the captured turbidity causing materials from the untreated raw
water) settle to the bottom of the basin leaving a clear supernatant which meets the NPDES
permit requirements.
Sludge solids generated from the treatment process are drawn off the settling basin bottom on a
daily basis and discharged directly to the City's North Buffalo/Metro system of wastewater
reclamation plants via sanitary sewer. At the wastewater reclamation plant, sludge solids from
the water plant are blended with other wastewater solids and then thickened, dewatered, and
incinerated.
P.O. Box 3136 : Greensboro, NC 27402-3136 , www.greensboro.nc.gov : (336) 373-CITY (2489) : TTY# 333-6930