NC0026441_Performance Summary_20221107

TOWN OF SILER CITY WWTP
TREATMENT PERFORMANCE EVALUATION
TOWN OF SILER CITY
CHATHAM COUNTY, NORTH CAROLINA
David L. Honeycutt, PE
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5 Regional Circle, Suite A
Pinehurst, North Carolina 28374
910.295.3159
Firm License No.: C-0459
NOVEMBER 2022

Siler City WWTP
TREATMENT PERFORMANCE EVALUATION
TABLE OF CONTENTS
1. Introduction
2. Existing Influent Parameters and Facility Performance
3. Pretreatment Program
4. Existing Wastewater Treatment Facilities
5. Potential Effluent Limits
APPENDIX
1. Town OF Siler City NPDES Permit
2. Mountaire Farms Industrial User Permit
3. MTS Design Data Sheet (1992)

1.0 Introduction
This evaluation is prepared for the Town of Siler City Wastewater Treatment Plant
(WWTP) to review the existing treatment system and operation to evaluate facility
performance as required for the Special Order by Consent process. The Town currently
operates the WWTP under NPDES Permit No. NC0026441 at a capacity of 4.0 MGD.
The WWTP effluent has exceeded permit limits numerous times in the past two years
and the facility has been placed under a Moratorium by the North Carolina Department
of Environmental Quality (NCDEQ). The Town is seeking to enter a Special Order by
Consent (SOC) to define a plan to address the deficiencies in the facilities and bring the
plant back into consistent compliance with the NPDES permit.
There are a number of factors that appear to be impacting the plant performance. These
factors include, high strength influent wastewater, toxicity and inhibition, solids
management and significant industrial users. This report is formatted to provide a
summary of the current influent and effluent data for the facility, Pretreatment Program,
evaluation of the treatment components included in the facility, and an estimate of the
effluent limits the facility could be expected to meet during the term of the SOC.
Siler City WWTP Treatment Performance Evaluation Page 1

2.0 Existing Influent Parameters and Facility Performance
Influent and effluent data from January 2021 through September 2022 was
reviewed for the purposes of this evaluation. A summary of the data is provided
in Table 2.1 and 2.2 below. Averages for each year and 95th percentiles of the
data were utilized for comparison. It is noted that the average influent BOD rose
approximately 15% from 299 to 345 mg/I from 2021 to 2022. TN and ammonia
values were slightly lower in 2022 than 2021.
Table 2.1 Siler City WWTP Influent Data
Siler City WWTP Influent Measurements
Flow
(MGD)
BOD
(mg\L)
TSS
(mg\L)
TN
(mg\L)
NH3
(mg\L)
TP
(mg\L)
2021 Average
2.77
299.31
207.98
40.09
31.9
4.52
2022 Average
2.65
345.23
232.28
38.02
24.32
4.82
2 Year Average
2.72
323.74
220.91
17.16
10.86
4.66
2-Year Maximum
Month Average
4.65
393.70
332.25
46.70
35.09
11.7
2021-951h Percentile
I 4.41
428.00
485.80
19.52
21.69
7.55
2022-951h Percentile
I 4.28
491.00
498.00
51.79
38.96
7.82
*Based on DMR data from January 1, 2021 - September 30, 2022
The plant is currently operating under the 4.0 MGD permit with the modification became
effective on November 1, 2022. Table 2.3 is an excerpt from A.(1.) of the NPDES
permit.
Siler City WWTP Treatment Performance Evaluation Page 2

Table 2.2 — Siler City WWTP Effluent Limitations and Monitoring at 4.0 MGD
EFFLLT—NT CFLARACTERISTIC
LLiiITS
NIONZTORTNG REQLIREhiENIS
Parametff Code
hionthh- Weeur Daih-
Measurement Sample Sample Lxadon
Average Aver:ti}e Varimum
Frequeno- Tspe
Flow
50050
4.0 MGD
CoBunuous
Recording
Influent Effiuentt
Total Monthly Flow
52220
Monitor and Report
Monthly
Recording
Influent or
(qG-o)
or Calculated
Fiffiueat
BOD, 5-day, 20°C i
5.0 mg.L
7.5 mglL
Daily
Composite
Tulluent and
-April 1— October 31
CO3I0
Fiffiueat
BOD, 5-*, 20°C 2
.g1L
104 m
15.4mgIL
Daily
Composite
Influent and
November 1 —March 31
Effiuent
Total Suspended Solids
I
C0530
30.0 mg1L
45.0 mgiL
Dailti•
Composite
hitluent and
(TSS)
Effiuent
-Ammonia p4$s as Nj
1.0 mgfL
3.0 mglL
Dailti•
Composite
Effiu at
-April 1 — October 31
CQ62 0
AmD14°ia as N)
2.0 mgfL
6.0 mg1L
Dailti
Composite
Effiuent
November 1 — March 31
Fecal Coliform
(geometrx mean)
31616
2001100 mL
4OR400 niL
Daily
Grab
Effluent
T�C�Residual Chlorine
50050
17.0 µpL
Daily
Grab
Effiuent
Temperature CC)
00010
Monitor and Report
Daily
Grab
Fiffiueat
Dissolved Oxygen (DO)
00300
Daily Average > 6.0 m&L
Daily
Grab
Effiuent
pH
00400
Between 6.0 and 9.0 Standard Units
Day
Grab
E.ffiumt
C'onducti%.* (mihoslca�
00094
Monitor and Report
Daily
Grab
Effiuent
NOS N +NOON (mgQ
00630
Monitor and Report
Weekly
Composite
Effiuent
Tffi4 (mg1L)
00625
Monitor and Report
weekly
Composite
Effluent
Total Nitrogen CM, mg1L 4
C0600
Monitor and Report
Weekly
Calculated
Effiuent
Qtid600
Momtoi and Deport Wmo) (permit cyde)
Monthly
OI600
182,646 b'yr (efE ibar * 1.2l3112022)
Annually
IN Load
OI600
146,1171bipr(eff. Ulf2023-12131f2423)
Annually
Calculated
E:ffiBmt
OI600
115,675lbiyr (eff. 11U202412131t2424) 7
?annually
O1600
54,WO lbdyi (eff: 11112025) t
Annually
Total Phosphorus CM a
-April 1 — October 31
C0665
4.5 nrglL (quarterly average)
Weekty
Composite
Effiueat
Total Phosphorus CM s
C 0665
2.0 mg-IL[quarterly average)
tiLreel L}'
Composite
Effiuent
November 1 — March 31
T� Hardness (as CaCO3),
00900
Mourtar and Report
Quarterly
Grab
Effiuent
Total Cadmium (as Cd)
01027
1.61iF/L I I 142 ug+L
Monthly
Composite
E lumt
fatal Capper (as Cu)
01042
Monitor and Report
Monthly
Composite
Effiuent
fatal Selemt= (as Se)
01147
Monitor and Report
Quarterly
Composite
Effiuent
Total Silver (as Ag)
01077
Monitor and Report
Quarterly
Composite
Effluent
C'hloaide (as Cl)
00940
233 mgiL
Monthly
Composite
Effluent
Total Zinc (as Zu)
01092
Monitor and Repoat
Quarterly
Composite
Effiuent
Bis (2--thylhesyU phthalate
39100
Monitor and Report
Quartelty
Grab
Effiuent
l,d-DioBane H
8238$
Monitor and Report
Monthly
Grab
Effiuent
PFAS
various
Footnote 12
Footnote 12
Grab
Effluent
ChronicTofficityii
TGP31i
PassrFail Catsadaphraa dtrbia at 90°fo
effiuent
Quarterly
Composite
Effluent
Effiuent Pollutant Scan
AVOi
Monitor and Report
Footnote 14
Footnote 14
Effiuent
Siler City WWTP Treatment Performance Evaluation Page 3

Table 2.3 WWTP Effluent Data
Siler City WWTP Effluent Data
Flow
BOD
TSS
TN
NH3
TP
(MGD)
(mg\L)
(mg\L)
(mg\L)
(mg\L)
(mg\L)
2.77
8.98
5.00
8.35
4.93
0.28
2021 Average
2022 Average
2.65
9.36
7.90
10.94
5.35
0.36
2 Year Average
2.72
9.19
6.54
9.11
5.11
0.32
2-Year Maximum
4.65
51.69
39.91
26.78
19.49
1.06
Month Average
2021-95th
4.41
27.39
17.41
19.52
21.75
0.73
Percentile
2022-95th
4.28
34.39
12.50
30.16
21.38
1.90
Percentile
*Based on DMR data from January 1, 2021 - September 30, 2022
Effluent data from WWTP indicate that the plant has had significant challenges
meeting limits for BOD and Ammonia during this period. Total Nitrogen on
average has been relatively as the plant is typically operating at a very low DO
level. Ammonia that reaches nitrification is then de -nitrified typically resulting in
good TN removal. When oxygen levels in the WWTP are too low to provide
adequate removal of the BOD and achieve nitrification these constituents pass
through to the effluent. Inhibition is also suspected of contributing to this
performance issue due to high iron content and chlorine in the influent. At over
24 hours the plant has more than adequate retention time in the oxidation ditches
however the effluent performance is being impacted by other factors. Further
discussion on the plant components is included in Section 4.0.
Siler City WWTP Treatment Performance Evaluation Page 4

3.0 Pretreatment Program
3.1 Current Industrial Users
The Town of Siler City currently has two permitted Significant Industrial
Users (SIU), Mountaire Farms and Brookwood Farms. Both are meat
processing facilities however, Mountaire Farms is a substantially higher
wastewater production than Brookwood Farms. Mountaire Farms started
operations at the beginning of 2019 and holds a permit to discharge up to
1.25 MGD. Brookwood Farms has a permit to discharge up to 0.035 MGD.
Effluent data was reviewed for the two industrial users from 2021 to 2022
and compared to permit limits as shown below.
Table 3.1 Mountaire Farms Permit Limits
Parameter
Daily
Max
Monthly
Average
Flow MGD
1.65
1.25
BOD m /I
540
450
TSS m /I
180
150
TN (mg/1)
100
75
NH3 m /I
50
40
TP m /I
7.2
6
Until May 2022 Monitoring was completed weekly by Mountaire and
Monthly by the Town. In 2022 monitoring frequency was increased to 5
days per week by the Town per NCDEQ requirements. Mountaire flows
are approximately 35% of the total average flow to the Town's WWTP and
therefore are a very heavy influence on the influent loading seen by the
Town's Wastewater Treatment Plant. There have been significant
discrepancies between the data recorded by the Towns sample
information and Mountaire Farms self -monitoring. The Town and
Mountaire have looked into this issue and utilized split samples with 3rd
party laboratories as well to try to determine the source of these
discrepancies, but it has not been determined at this time. As shown in the
following table the Town's data shows that the 2021 average effluent BOD
was 561 and is a similar 560 mg/I to date in 2022. These values are
approximately 24% above the monthly average permit limit of 450 mg/I for
BOD. The average influent BOD to the Town's WWTP was 323 mg/I which
is a strong wastewater for a municipal facility. Impacts of high BOD are
discussed further in Part 4.0 with the oxidation ditch performance.
Town operators have also noted that the Mountaire Facility has sent
wastewater containing significant chlorine residual. Limited data is
Siler City WWTP Treatment Performance Evaluation Page 5

available to include details of this information, but it is likely that chlorine
residual can cause both inhibition and toxicity at the WWTP. Mountaire's
pretreatment system was designed to include de -chlorination to remove
chlorine residual prior to discharge. Once this issue was discovered the
Town notified Mountaire and de -chlorination has resumed. The chlorine
residual likely has impacted the Town's WWTP performance in the past
year, however it is anticipated that these impacts should be reduced or
eliminated with Mountaire's operational correction.
Table 3.2 Mountaire Farms Effluent Data
Mountaire Pre -Treatment
Flow
BOD
TSS
TN
NH3
TP
(MGD)
(mg\L)
(mg\L)
(mg\L)
(mg\L)
(mg\L)
Self
Town
Self
Town
Self
Town
Self
Town
Self
Town
2021 Average
0.979
283.92
561.00
23.65
20.74
15.59
68.47
5.84
41.48
0.83
5.18
2022 Average
0.930
251.67
559.66
1 28.07
47.23
12.60
70.82
6.19
35.41
0.65
3.80
2 Year Average
0.957
269.63
559.84
25.63
43.57
14.27
70.51
5.99
36.20
0.75
3.90
2-Year Maximum
1.242
362.00
745.00
38.50
78.50
21.68
98.20
13.58
75.60
1.38
9.30
Month Average
2021-95th
1.192
388.80
717.50
38.51
38.08
27.20
95.89
9.66
68.29
1.52
6.68
Percentile
2022-95th
1.076
360.60
806.70
44.64
111.90
18.06
88.08
16.53
57.62
1.11
6.84
Percentile
Brookwood Farms also has the potential to discharge high concentrations of BOD and
TN, Ammonia and TP to the Town's WWTP. The data for Brookwood for 2021 and 2022
was reviewed as well to determine potential for impact from their discharges to the
Town's performance. Although the permit allows discharge up to 800 mg/I BOD, the
average BOD over the past two years has only been 58 mg/I and 28 mg/I respectively.
The TN concentration is higher at 116 and 137 mg/I however it is noted that the flow
from Brookwood is only 20,000 to 30,000 gallons per day and nitrogen load is therefore
less than 5% of the plant influent loading. Therefore it does not appear that Brookwood
Farms wastewater is a significant contributor to the violations at the Town of Siler City
WWTP.
Table 3.3 Brookwood Permit Limits
Parameter
Daily Max
Flow MGD
0.035
BOD (mg/1)
800
TSS (mg/1)
450
TN m /I
150
TP m /I
Monitor
Siler City WWTP Treatment Performance Evaluation Page 6

Table 3.4 Brookwood Effluent Data
Brookwood Pre -Treatment
Flow
(MGD)
BOD
(mg\L)
TSS
(mg\L)
TN
(mg\L)
NH3
(mg\L)
TP
(mg\L)
Permit Limit
0.035
800
450
150
2021 Average
0.0216
57.83
135.24
115.79
23.10
10.77
2022 Average
0.0292
27.55
102.96
136.78
14.70
13.65
3.2 Water Treatment Plant
The Town of Siler City Water Treatment Plant is a 4.0 MGD plant which
currently utilizes conventional treatment consisting of coagulation,
flocculation, sedimentation, and filtration. The plant produces process
wastewater from backwash of the filters, cleaning the sedimentation
basins and other miscellaneous uses. This water is initially sent to a
circular equalization tank and then pumped to a sludge lagoon where
solids are both settled and stored. Water is then drained from the end of
the lagoon to a lift station with duplex submersible pumps which pumps
the wastewater to the Town's sewer collection system and eventually the
WWTP. Effluent from the lagoon is frequently high in solids due to
inadequate settling in the lagoon, surges in flow from frequent
backwashes, and basin cleaning required to keep the water treatment
plant in operation. The plant uses Ferric Chloride as the primary coagulant
and therefore these solids are very high in iron. The iron content
measured at the influent to the WWTP has varied substantially and
reached values of over 200 mg/I. Iron is not specially listed as a pollutant
of concern for inhibition in a WWTP within Pretreatment Program
spreadsheets however literature values list a range of potential inhibition
levels. EPA guidance lists a range of 5-500 mg/I. Iron accumulates in the
mixed liquor at the WWTP and creates challenges for operations and
biological activity in the plant. The Town has begun collecting samples
influent regularly and should utilize this data in conjunction with
performance data to determine the level of iron that causes interference
specific to the Siler City WWTP. A cursory review indicates a target
influent value of 50 mg/I or less is likely appropriate.
The Town has already installed baffles in the lagoon which are improving
the settling efficiency. They should continue to remove sludge frequently
to prevent slug loads of sludge from being washed out of the lagoon to the
pump station and WWTP.
Siler City WWTP Treatment Performance Evaluation Page 7

4.0 Existing Wastewater Treatment Facilities
4.1 Influent Pump Station
Influent pump station includes 4 duty and 1 standby self -priming suction lift
pumps. Each pump has a capacity of 3,250 gpm or 4.68 MGD. This gives
the pump station a firm capacity of 14.04 MGD with one pump out of service.
There is not a flow meter at the pump station and the configuration of the
wetwell is not conducive to drawdown testing. Influent pumps have not been
reported to have failed to keep up with the influent flow or otherwise
contributed to the issue so no further evaluation of these facilities appears
to be necessary at this time.
4.2 Flow Equalization
The plant has four (4) flow equalization zones, with capacities as follows:
FLOW EQ
ZONE
BASIN QUAN.,
SHAPE
TOTAL VOLUME
GAL
1
1, RECT.
159,070
2
1, RECT
951,550
3
2, ROUND
507,580
4
1, RECT.
396,365
TOTAL: 2,014,565
These zones are connected such that they are capable of receiving flow
from multiple points in the treatment process from after the headworks all
the way to the backwash from the tertiary sand filters.
Flow equalization tankage noted above is functional and aeration systems
are in working order. A second rectangular tank in Zone 4 is not in service
due to structural issues. The performance of flow equalization tanks does
not appear to be contributing significantly to the systems failure to provide
adequate treatment.
4.3 Oxidation Ditches
The plant has parallel oxidation ditches, each with a volume of
approximately 2.2 MG. Both basins provide approximately 26.4 hours of
detention time at the 4.0 MGD design flow. Each basin is equipped with jet
aerators to supply oxygen to the ditch. Three blowers are operational, each
with 150 hp motor.
According to data sheets from MTS per the original design the plant is
designed to run with two duty blowers and one standby. The aeration
Siler City WWTP Treatment Performance Evaluation Page 8

system is sized to provide treatment for a BOD5 of 350 mg/I and influent
ammonia of 45 mg/I with effluent of 5 mg/I and 1 mg/I respectively. This
design is based on an oxygen transfer efficiency of 28.6% for the jet
aeration system.
Per visual observations of the bubble pattern and surface flow patterns in
the oxidation ditches the aeration system does not appear to be functioning
properly. It is suspected that the jets are deteriorated to the extent that they
are not providing the directional mixing and air entrainment that is intended
for this system. Therefore, the transfer efficiency is substantially reduced.
Further evidence of this is noted in the operators DO measurements for the
oxidation ditches which are conducted both manually and via four (4) online
DO meters in the oxidation ditch basins. Although the facility is designed to
run with 2 of the 3 blowers in service, operators have been running with all
3 blowers in service to try to maintain DO levels to the extent feasible. The
DO values vary, however, the average is typically less than 0.5 mg/I within
the basins.
Based on the performance of the plant this value is adequate to meet the
BOD and provide nitrification under the current average conditions. At
higher peak BOD and ammonia conditions the plant the DO levels have
been depressed to the extent that BOD removal is inadequate and
nitrification is not complete. This results in violations of the NPDES
permit for BOD and Ammonia. Elevated ammonia values are also
suspected to be a significant contributor to effluent toxicity and failure of
toxicity testing required by the permit.
As noted above, operators are typically running all three blowers to attempt
to maintain DO levels in the oxidation ditches. Repair of the jet aerators is
impractical as it requires an oxidation ditch to be removed from service. At
current flows both basins are needed to provide adequate treatment
volume.
Solids levels within the oxidation ditch are also likely contributing to the
issues with maintaining DO levels. The system was designed to run at 4,000
mg/I per the MTS data sheets and MLSS concentrations have varied up to
6,000 to 7,000 mg/I. These high values cause additional endogenous
respiration which consumes DO and can reduce transfer efficiency by
depressing the alpha value of the mixed liquor. It is recommended for
operators to keep MLSS levels to less than 5,000 mg/I and target operation
near 4,000 mg/I to minimize the impacts of high solids concentrations.
Siler City WWTP Treatment Performance Evaluation Page 9

4.4 Clarifiers
A clarifier splitter box directs flow to the two existing 90-foot diameter
clarifiers. The splitter box has the ability of mixing Lime or alum to the
wastewater prior to entering the secondary clarification stage. Mixed liquor
suspended solids (MLSS) are divided into two (2) secondary clarifiers for
sludge settling. The clarifiers have suction tube -type sludge removal
mechanisms with full surface skimmers. The clarifier loading rate is 314.4
gpd/sf based on a 90-foot diameter handling 2 MGD average daily flow. This
value is within the range recommended by Metcalf and Eddy, Wastewater
Engineering 4th edition pg 687 (300-500 gpd/SF)
Check solids loading at 4,000 mg/I MLSS. At a RAS flowrate of 75%,
solids loading for each clarifier is calculated as follows:
(2.0 MGD (design flow) + 1.5 MGD RAS) * 8.34 * 4,000 mg/I = 116,760
Ibs/day = 4865 Ibs/hr
4,865 Ibs/hr / 6,372 SF = 0.76 Ibs/hr/sf at average condition.
Metcalf and Eddy4th edition pg. 687 recommends 1-1.5 for BNR, OK at
average with 4,000 mg/I
(2.0 MGD (design flow) + 1.5 MGD RAS) * 8.34 * 7,000 mg/I = 204,330
Ibs/day = 8513.75 Ibs/hr
8,513.75 Ibs/hr / 6,372 SF = 1.34 Ibs/hr/sf at average flow with high solids.
Metcalf and Eddy4th edition pg. 687 recommends 1-1.5 for BN., Based on
this calculation the solids loading rate is acceptable with the high MLSS
value of 7,000 mg/I however it is noted that with higher flows the value is
more likely to cause issues with efficient settling in the clarifiers.
4.5 Filters
The plant utilizes Greenleaf sand filters with four (4) zones. The gravity -
based sand filter is used to filter any suspended solids remaining after the
clarification process. The filters have a total area of 2304 SF which gives a
loading rate of 1.2 GPM per square foot at the plant ADF of 4 MGD and 3
GPM per square foot at peak flow.
These loading rates are within current design parameters for similar
equipment. Filter media has been replaced in 2021 and is therefore
understood to be in good condition.
Siler City WWTP Treatment Performance Evaluation Page 10

4.6 Chlorine Disinfection
The plant has two (2) chlorine contact basins. Chlorine feed is supplied
from one -ton cylinders maintained on site. After the wastewater has been
disinfected it flows to a de -chlorination basin where Sulfur dioxide is added
for de -chlorination. Chlorine contact basin is approximately 84,000 gallons
and provides 30 minutes detention time at 4.0 MGD average daily flow.
4.7 Post Aeration
Disinfected water flows via gravity to the 23 feet long cascade aerator.
The cascade aerator generates utilizes the fall to induce turbulent flow and
introduce air into the treated effluent.
The post -aeration mechanism appears to be working effectively and the
effluent DO concentrations are consistently in compliance with permit
requirements.
4.8 RAS/WAS Pump Station
The RAS/WAS Pump Station contains three (3) RAS/WAS pumps, each
rated 15 HP, 1,200 gpm at 25 ft of total dynamic head (TDH). Valves are
utilized to direct sludge flow to waste or return per operator selection.
RAS/WAS pumping capacities are meet typical design criteria and are
adequate for sludge removal from the clarifiers.
4.9 Sludge Holding and Digestion Facilities
Waste sludge is directed to two aerobic digester tanks, previously
secondary clarifiers, where it is able to settle and thicken prior to storage
in the aerated thickened sludge storage tanks. Decant pumps can remove
additional water from the thickened sludge storage tanks which is returned
to the head of the plant. Each aerobic digester provides a volume of
280,000 gallons. The sludge holding tanks include a volume of
approximately 1,350,000 gallons for a total sludge storage volume of
1,910,000 gallons. The Town can also utilize flow eq zone 4 for sludge
storage when needed which provides an additional 396,000 gallons.
4.10 Sludge Disposal
The Town has a contract with Synagro land apply sludge under Land
Application permit WQ0003226. The capacity of the permitted fields is
1,325 dry tons per year. In 2020 a total of 617.13 dry tons was applied. In
Siler City WWTP Treatment Performance Evaluation Page 11

2021 a total of 467.34 dry tons was applied. The Town has adequate
disposal capacity in the land application permit for the sludge produced.
Due to wet weather and freezing temperatures land application is limited
during the winter months and the Town is unable to store solids
adequately at the WWTP for the extended period to control sludge levels
in the treatment basins. The Town has utilized a dewatering belt press
recently to better control those levels and is expected to need to continue
to do so until a permanent dewatering or alternative disposal system is in
place.
5.0 Potential Effluent Limits
Based on the historical data reviewed and current facilities, the plant
performance is anticipated to continue to fall short of consistently meeting the
final effluent limits. There are expected to be periods of time where the facility
meets effluent limits but when the facility is inhibited due to influent iron, and
chlorine concentrations, receives excessive BOD or 1/1 these factors are likely to
continue to cause the plant to exceed the effluent limits. These issues are
outside of the operations staff control and may vary throughout the year. Based
on the ongoing efforts previously discussed it is anticipated that the periods of
violation will continue to be shortened to minimize impacts of these exceedances
of the effluent limits.
Per review of the performance over the past two years and the improvements
that have been completed to date the plant is expected to meet the following
effluent limits prior to completion of the expansion to 6.0 MGD. Performance
does not vary substantially from winter to summer and therefore a single value is
indicated below. It is noted that occasional exceedances of these levels may still
occur due to extraordinarily high 1/I, influent loading, or plant upsets.
Parameter
W ekly Avg
Monthly Avg
BOD5
15
10
NH3-N
10
5
Note: Parameters not included are expected to be in compliance with the final effluent limit for the
4.0 MGD flow (Part A. (1)).
The plant has also had several toxicity failures in recent sampling. Due to the
complexity of toxicity testing and inconsistency within the plant's performance a
compliance level for toxicity has not been estimated. It is however anticipated
that some failures of toxicity will continue, particularly during abnormal conditions
for influent flows or loading.
Siler City WWTP Treatment Performance Evaluation Page 12

DocuSign Envelope ID: BE4B49F0-FCB3-4935-8395-089B8438A007
STATE OF NORTH CAROLINA
DEPARTMENT OF ENVIRONMENTAL QUALITY
DIVISION OF WATER RESOURCES
PERMIT
TO DISCHARGE WASTEWATER UNDER THE
NATIONAL POLLUTANT DISCHARGE ELIMINATION SYSTEM
In compliance with the provisions 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
Town of Siler City
is hereby authorized to discharge wastewater from a facility located at the
Siler City WWTP
198 Utility Drive
Siler City, NC 27344
Chatham County
to receiving waters designated as Loves Creek in the Cape Fear River Basin in accordance with effluent
limitations, monitoring requirements, and other conditions set forth in Parts I, II, III and IV hereof.
This permit shall become effective November 1, 2022.
This permit and authorization to discharge shall expire at midnight on May 31, 2027.
Signed this day September 28, 2022.
Do'c'fu.Si-gne'Id byy:� A A
E
Nl/�/�'�N A'WKhJstVfJ
C464531431644FE...
for Richard E. Rogers, Jr., Director
Division of Water Resources
By Authority of the Environmental Management Commission

DocuSign Envelope ID: BE4B49F0-FCB3-4935-8395-089B8438A007
Permit NCO026441
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 issuedpermit 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 Town of Siler City is hereby authorized to:
1. Continue to operate an existing 4.0 MGD wastewater treatment system consisting of the following:
• Automatic and manual bar screens
• Grit collection unit
• Influent pump station
• Influent Equalization Basin (Zone 2)
• Dual oxidation ditches with surface jet aeration
• Flow Splitter Box
o Alum feed station
o Lime feed station
• Dual secondary clarifiers
• Dual Aerobic digesters
• Return Activated Sludge
• Sludge Transfer Station
• Dissolved Air Flotation Unit (Used as needed)
• Sludge Thickener Basin
• Influent equalization or Sludge Storage Basins (Zone 3 A & B used as needed)
• Four (4) tertiary filters
• Filter Backwash Basin
• Gaseous Chlorine Disinfection
• Chlorine contact chamber
• Gaseous Sulfur Dioxide Dechlorination
• Step -Aeration
The facility is located at the 198 Utility Drive, Siler City, in Chatham County;
2. After receiving an Authorization to Construct from the Division, construct a 6.0 MGD wastewater
treatment system; and after the Division receives the Engineer Certification of construction completion,
operate above system. The draft upgraded system includes the following upgraded/additional
components:
• Upgraded headworks including duplex mechanical bar screens and grit removal
• Upgraded influent pump station (firm capacity 18 MGD)
• Two (2) 100 hp blowers
• One additional oxidation ditch with baffles, aeration and mixing equipment to create aerobic,
anaerobic and anoxic zones
• One additional clarifier
• Effluent denitrification filters
• UV disinfection system
• Solids handling facility with filter press
3. Discharge from said treatment works at the location specified on the attached map into Loves Creek,
classified C waters in the Cape Fear River Basin.
Page 2 of 19

DocuSign Envelope ID: BE4B49F0-FCB3-4935-8395-089B8438A007
Permit NCO026441
PART I
A. (1.) EFFLUENT LIMITATIONS AND MONITORING REQUIREMENTS (4.0 MGD)
[15A NCAC 02B .0400 et seq., 02B .0500 et seq.]
Grade IV Biological Water Pollution Control System [15A NCAC 08G .0302]
a. During the period beginning on the effective date of the permit and lasting until expansion to 6.0 MGD (and
receipt of the Engineer's Certificate of completion) or until expiration, the Permittee is authorized to discharge
treated domestic and industrial wastewater from Outfall 001. Such discharges shall be limited and
monitored' by the Permittee as specified below:
EFFLUENT CHARACTERISTICS
LIMITS
MONITORING REQUIREMENTS
Monthly
Weekly
Daily
Measurement
Sample
Sample Location
Parameter Code
Average
Average
Maximum
Frequency
Type
Flow
50050
4.0 MGD
Continuous
Recording
Influent or
Effluent
Total Monthly Flow
82220
Monitor and Report
Monthly
Recording
Influent or
(MG/mo)
or Calculated
Effluent
BOD, 5-day, 20°C 2
5.0 mg/L
7.5 mg/L
Daily
Composite
Influent and
April 1 — October 31
C0310
Effluent
BOD, 5-day, 20°C 2
10.0 mg/L
15.0 mg/L
Daily
Composite
Influent and
November 1 — March 31
Effluent
Total Suspended Solids
(TSS)
C0530
30.0 mg/L
45.0 mg/L
Daily
Composite
Influent and
Effluent
Ammonia (NH3 as N)
1.0 mg/L
3.0 mg/L
Daily
Composite
Effluent
April 1 — October 31
C0610
Ammonia (NH3 as N)
2.0 mg/L
6.0 mg/L
Daily
Composite
Effluent
November 1 — March 31
Fecal Coliform
31616
200/100 mL
400/100 mL
Daily
Grab
Effluent
(geometric mean)
Total Residual Chlorine
(TRC)
50050
17.0 µg/L
Daily
Grab
Effluent
Temperature (°C)
00010
Monitor and Report
Daily
Grab
Effluent
Dissolved Oxygen (DO)
00300
Daily Average > 6.0 mg/L
Daily
Grab
Effluent
pH
00400
Between 6.0 and 9.0 Standard Units
Daily
Grab
Effluent
Conductivity (µmhos/cm)
00094
Monitor and Report
Daily
Grab
Effluent
NO2-N +NO3-N (mg/L)
00630
Monitor and Report
Weekly
Composite
Effluent
TKN (mg/L)
00625
Monitor and Report
Weekly
Composite
Effluent
Total Nitrogen (TN), mg/L 4
C0600
Monitor and Report
Weekly
Calculated
Effluent
QM600
Monitor and Report (lb/mo) (permit cycle)
Monthly
QY600
182,6461b/yr (eff. through 12/31/2022)
Annually
TN Loads
QY600
146,1171b/yr (eff. 1/1/2023-12/31/2023) 6
Annually
Calculated
Effluent
QY600
115,6781b/yr (eff. 1/l/2024-12/31/2024)
Annually
QY600
54,800 lb/yr (eff. 1/l/2025) s
Annually
Total Phosphorus (TP) 9
April 1 — October 31
C0665
0.5 mg/L (quarterly average)
Weekly
Composite
Effluent
Total Phosphorus (TP) 9
November 1 — March 31
C0665
2.0 mg/L (quarterly average)
Weekly
Composite
Effluent
Total L Hardness (as CaCO3), 10
00900
Monitor and Report
Quarterly
Grab
Effluent
Page 3 of 19

DocuSign Envelope ID: BE4B49F0-FCB3-4935-8395-089B8438A007
Permit NCO026441
EFFLUENT CHARACTERISTICS
Parameter Code
LIMITS
MONITORING REQUIREMENTS
Monthly
Average
Weekly
Average
Daily
Maximum
Measurement
Frequency
Sample
Type
Sample Location
Total Cadmium (as Cd)
01027
1.6 µg/L
10.2 µg/L
Monthly
Composite
Effluent
Total Copper (as Cu)
01042
Monitor and Report
Monthly
Composite
Effluent
Total Selenium (as Se)
01147
Monitor and Report
Quarterly
Composite
Effluent
Total Silver (as Ag)
01077
Monitor and Report
Quarterly
Composite
Effluent
Chloride (as Cl)
00940
233 mg/L
Monthly
Composite
Effluent
Total Zinc (as Zn)
01092
Monitor and Report
Quarterly
Composite
Effluent
Bis (2-ethylhexyl) phthalate
39100
Monitor and Report
Quarterly tGrab
Effluent
1,4-Dioxane 11
82388
Monitor and Report
Monthly
Grab
Effluent
PFAS
various
Footnote 12
Footnote 12
Grab
Effluent
Chronic Toxicity 13
TGP3B
Pass/Fail Ceriodaphnia dubia at 90%
effluent
Quarterly
Composite
Effluent
Effluent Pollutant Scan
NCO]
Monitor and Report
Footnote 14
1 Footnote 14
Effluent
Footnotes:
1. Submit discharge monitoring reports electronically using NC DWR's eDMR application system. See Section A. (15.).
2. The monthly average effluent BOD5 and TSS concentrations shall not exceed 15% of the respective influent value (85%
removal).
3. The facility shall monitor TRC when using chlorination for disinfection. The Division shall consider all effluent total
residual chlorine 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.
4. Total Nitrogen (TN) is defined as NO3-N+NO2-N + TKN, where NO3-N is nitrate nitrogen, NO2-N is nitrite nitrogen,
and TKN is total Kjeldahl Nitrogen.
5. TN Load is the mass quantity of Total Nitrogen discharged in a given period of time. See Section A. (7.), Calculation of
Total Nitrogen Loads.
6. Limit to be applied if the facility does not complete upgrade to 6.0 MGD by 12/31/2023.
7. Limit is the combined mass of the interim load limit of 146,117 lb/yr from 1/l/2024-8/31/2024 and final load limit of
58,800 lb/yr from 9/l/2024-12/31/2024, to be applied for calendar year 2024 only.
8. The Permittee shall follow the schedule to upgrade the facility to 6.0 MGD. See A. (9.).
9. Compliance with the Total Phosphorus limits shall be based on a calendar -quarter average of weekly samples.
10. Effluent Total Hardness sampling should be performed in conjunction with testing for hardness -dependent metals
(cadmium, copper, lead, nickel, silver, and zinc).
11. Samples must be reported to a minimum of PQL < 1 µg/L using EPA Method 624.1.
12. See Special Condition A. (14.).
13. Whole Effluent Toxicity will be monitored using the Pass/Fail Ceriodaphnia dubia at 90% effluent. Samples shall be
taken in March, June, September and December. See Section A. (5.).
14. The Permittee shall perform three Effluent Pollutant Scans during the term of this permit. See Section A. (6.).
b. There shall be no discharge of floating solids or visible foam in other than trace amounts.
Page 4 of 19

DocuSign Envelope ID: BE4B49F0-FCB3-4935-8395-089B8438A007
Permit NCO026441
A. (2.) EFFLUENT LIMITATIONS AND MONITORING REQUIREMENTS (6.0 MGD)
[15A NCAC 02B .0400 et seq., 02B .0500 et seq.]
Grade IV Biological Water Pollution Control System [15A NCAC 08G .0302]
a. During the period beginning upon receipt of the Engineer's Certificate of completion for expansion to 6.0
MGD and lasting until expiration, the Permittee is authorized to discharge treated domestic and industrial
wastewater from Outfall 001. Such discharges shall be limited and monitored 1 by the Permittee as specified
below:
EFFLUENT CHARACTERISTICS
LIMITS
MONITORING REQUIREMENTS
Monthly
Weekly
Daily
Measurement
Sample
Sample Location
Parameter Code
Average
Average
Maximum
Frequency
Type
Flow
50050
6.0 MGD
Continuous
Recording
Influent or
Effluent
Total Monthly Flow
82220
Monitor and Report
Monthly
Recording
Influent or
(MG/mo)
or Calculated
Effluent
BOD, 5-day, 20°C 2
5.0 mg/L
7.5 mg/L
Daily
Composite
Influent and
April 1 — October 31
C0310
Effluent
BOD, 5-day, 20°C 2
10.0 mg/L
15.0 mg/L
Daily
Composite
Influent and
November 1 — March 31
Effluent
Total Suspended Solids
(TSS)
C0530
20.0 mg/L
30.0 mg/L
Daily
Composite
Influent and
Effluent
Ammonia (NH3 as N)
1.0 mg/L
3.0 mg/L
Daily
Composite
Effluent
April 1 — October 31
C0610
Ammonia (NH3 as N)
1.9 mg/L
5.7 mg/L
Daily
Composite
Effluent
November 1 — March 31
Fecal Coliform
31616
200/100 mL
400/100 mL
Daily
Grab
Effluent
(geometric mean)
Total Residual Chlorine
(TRC)
50050
17.0 ❑g/L
Daily
Grab
Effluent
Temperature (°C)
00010
Monitor and Report
Daily
Grab
Effluent
Dissolved Oxygen (DO)
00300
Daily Average > 7.0 mg/L
Daily
Grab
Effluent
pH
00400
Between 6.0 and 9.0 Standard Units
Daily
Grab
Effluent
Conductivity (µmhos/cm)
00094
Monitor and Report
Daily
Grab
Effluent
Total Organic Nitrogen
00605
3.0 mg/L
4.5 mg/L
Weekly
Composite
Effluent
April 1 — October 31
NO2-N +NO3-N (mg/L)
00630
Monitor and Report
Weekly
Composite
Effluent
TKN (mg/L)
00625
Monitor and Report
Weekly
Composite
Effluent
Total Nitrogen (TN), mg/L a
C0600
Monitor and Report
Weekly
Calculated
Effluent
QM600
Monitor and Report (lb/mo)
Monthly
TN Load'
QY600
115,6781b/yr (efi 1/l/2024) 6
Annually
Calculated
Effluent
QY600
54,800 lb/yr (efi 1/l/2025)
Annually
Total Phosphorus (TP) 7
C0665
0.5 mg/L (quarterly average)
Weekly
Composite
Effluent
April 1 — October 31
Total Phosphorus (TP) 7
C0665
2.0 mg/L (quarterly average)
Weekly
Composite
Effluent
November 1 — March 31
Tmot L Hardness (as CaCO3),
00900
Monitor and Report
Quarterly
Grab
Effluent
Page 5 of 19

DocuSign Envelope ID: BE4B49F0-FCB3-4935-8395-089B8438A007
Permit NCO026441
EFFLUENT CHARACTERISTICS
Parameter Code
LIMITS
MONITORING REQUIREMENTS
Monthly
Average
Weekly
Average
Daily
Maximum
Measurement
Frequency
Sample
Type
Sample Location
Total Cadmium (as Cd)
01027
1.6 µg/L
10.2 µg/L
Monthly
Composite
Effluent
Total Copper (as Cu)
01042
Monitor and Report
Monthly
Composite
Effluent
Total Selenium (as Se)
01147
Monitor and Report
Quarterly
Composite
Effluent
Total Silver (as Ag)
01077
Monitor and Report
Quarterly
Composite
Effluent
Total Zinc (as Zn)
01092
Monitor and Report
Quarterly
Composite
Effluent
Chloride (as Cl)
00940
232 mg/L
Monthly
Composite
Effluent
Bis (2-ethylhexyl) phthalate
39100
Monitor and Report
Quarterly
Grab
Effluent
1,4-Dioxane v
82388
Monitor and Report
Monthly
Grab
Effluent
PFAS
various
Footnote 10
Footnote 10
Grab
Effluent
Chronic Toxicity 11
TGP3B
Pass/Fail Ceriodaphnia dubia at 90%
effluent
Quarterly
Composite
Effluent
Effluent Pollutant Scan
NC01
Monitor and Report
Footnote 12
Footnote 12
Effluent
Footnotes:
1. Submit discharge monitoring reports electronically using NC DWR's eDMR application system. See Section A. (15.).
2. The monthly average effluent BOD5 and TSS concentrations shall not exceed 15% of the respective influent value (85%
removal).
3. The facility shall monitor TRC when using chlorination for disinfection. The Division shall consider all effluent total
residual chlorine 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.
4. Total Nitrogen (TN) is defined as NO3-N+NO2-N + TKN, where NO3-N is nitrate nitrogen, NO2-N is nitrite nitrogen,
and TKN is total Kjeldahl Nitrogen.
5. TN Load is the mass quantity of Total Nitrogen discharged in a given period of time. See Section A. (7.), Calculation of
Total Nitrogen Loads.
6. Limit is the combined mass at the interim load limit of 146,117 lb/yr (i.e., 97,411 lb) from 1/ 1/2024-8/3 1/2024 and final
load limit of 58,800 lb/yr (i.e., 18,267 lb) from 9/l/2024-12/31/2024, to be applied for calendar year 2024 only.
7. Compliance with the Total Phosphorus limits shall be based on a calendar -quarter average of weekly samples.
8. Effluent Total Hardness sampling should be performed in conjunction with testing for hardness -dependent metals
(cadmium, copper, lead, nickel, silver, and zinc).
9. Samples must be reported to a minimum of PQL < 1 µg/L using EPA Methd 624.1.
10. See Special Condition A. (14.).
11. Whole Effluent Toxicity will be monitored using the Pass/Fail Ceriodaphnia dubia at 90% effluent. Samples shall be
taken in March, June, September and December. See Section A. (5.).
12. The Permittee shall perform three Effluent Pollutant Scans during the term of this permit. See Section A. (6.).
b. There shall be no discharge of floating solids or visible foam in other than trace amounts.
Page 6 of 19

DocuSign Envelope ID: BE4B49F0-FCB3-4935-8395-089B8438A007
Permit NCO026441
A. (3.) INSTREAM MONITORING REQUIREMENTS [15A NCAC 0213.0500 et seq.]
During the period beginning on the effective date of the permit and lasting until expiration, the Permittee shall
conduct instream monitoring as specified below:
PARAMETER
SAMPLE TYPE
LOCATION'
MEASUREMENT
Parameter Code
FREQUENCY'
Total Hardness (as CaCO3), mg/L3
00900
Grab
LCU
1/Quarter
Dissolved Oxygen (DO), mg/L
00300
Grab
LCU, LCD, RRU, RRD
3/Week (June — September),
1/Week (October -May)
Temperature (°C)
00010
Grab
LCU, LCD, RRU, RRD
3/Week (June — September),
1/Week (October -May)
Fecal Coliform (cfu/100 mL)
31616
Grab
LCU, LCD, RRU, RRD
1/Month
Conductivity (µmhos/cm)
00094
Grab
LCU, LCD, RRU, RRD
3/Week (May — September),
1/Week (October —April)
Total Phosphorus (mg/L)
C0665
Grab
LCU, LCD, RRU, RRD
3/Week (June — September),
1/Week (October -May)
TKN (mg/L)
00625
Grab
LCU, LCD, RRU, RRD
3/Week (June — September),
1/Week (October -May)
NO2 + NO3 (mg/L)
00630
Grab
LCU, LCD, RRU, RRD
3/Week (June — September),
1/Week (October -May)
Ammonia (NH3 as N)
C0610
Grab
LCU, LCD, RRU, RRD
3/Week (June — September),
1/Week (October -May)
pH
00400
Grab
LCU, LCD, RRU, RRD
3/Week (June — September),
1/Week (October -May)
Footnotes:
1. LCU = Loves Creek, upstream of the discharge; LCD = Loves Creek, downstream of the discharge and above the
confluence with the Rocky River; RRU = Rocky River, upstream of the confluence with Loves Creek; RRD = Rocky
River, downstream of the confluence with Loves Creek.
2. All monitoring is required to be performed at the above -mentioned monitoring locations.
3. The Permittee shall sample instream Total Hardness, upstream of the facility's discharge. The sample shall be
representative of the hardness in the receiving stream.
Page 7 of 19

DocuSign Envelope ID: BE4B49F0-FCB3-4935-8395-089B8438A007
Permit NCO026441
A. (4.) INSTREAM ASSESSMENT OF BIOLOGICAL INTEGRITY (Annual)
[15A NCAC 02B .0200 et seq.]
a. By April 30, 2023 (180 days after the permit effective date), the Permittee shall submit a study plan to
annually assess biological integrity in the receiving water via benthic macroinvertebrate (benthos)
sampling and analysis. The study plan shall include methodologies consistent with DWR-approved
assessment methodologies' and propose an annual assessment schedule and sampling location(s). The
study plan shall be submitted to the Division at the address listed under (d.) of this section. Once DWR-
NPDES approves the study plan, it shall be used for all assessments unless a study plan modification is
approved/recommended by the Division. Instream biological integrity assessments shall be conducted by
a laboratory or entity that is NC -certified for the procedure.
b. By November 1, 2023 (one year from the permit effective date) and November 1 of every subsequent year
until permit expiration, the Permittee shall conduct an instream benthos assessment annually.
c. With each planned assessment, the Permittee shall provide the Division sufficient notice of sampling so
that Division personnel may attend and share samples collected.
d. The Permittee shall submit instream biological integrity assessment reports within 60 days of completion.
All reports shall include the owner's name, NPDES permit number and Permittee contact person, and
shall be submitted to:
(1) NCDEQ / Division of Water Resources
NPDES Permitting — Municipal Branch
1617 Mail Service Center
Raleigh, NC 27699-1617
(2) NCDEQ / Division of Water Resources
Raleigh Regional Office - WQRO
3800 Barrett Drive
Raleigh, NC 27604
e. If it is determined by the Division that the permitted discharge from the facility is not causing stream
degradation resulting in water quality standards violations, including narrative standards, the Permittee
may request that the instream assessments be terminated.
f. The addition of instream biological integrity assessment requirement does not preclude the Division from
taking any action necessary to resolve any ongoing compliance activity or effluent violations.
Footnote.
1. NC Department of Environmental Quality. 2016. Standard Operating Procedures for the Collection and Analysis
of Benthic Macroinvertebrates. Division of Water Resources. Raleigh, North Carolina. February 2016.
Page 8 of 19

DocuSign Envelope ID: BE4B49F0-FCB3-4935-8395-089B8438A007
Permit NC0026441
A. (5.) CHRONIC TOXICITY PERMIT LIMIT (Quarterly) [15A NCAC 02B .0200 et seq.]
The effluent discharge shall at no time exhibit observable inhibition of reproduction or significant mortality to
Ceriodaphnia dubia at an effluent concentration of 90% at 4.0 MGD and 6.0 MGD.
The permit holder shall perform at a minimum, quarterly monitoring using test procedures outlined in the "North
Carolina Ceriodaphnia Chronic Effluent Bioassay Procedure," (Revised December 2010, or subsequent versions)
or "North Carolina Phase II Chronic Whole Effluent Toxicity Test Procedure" (Revised December 2010, or
subsequent versions). The tests will be performed during the months of March, June, September, and
December. These months signify the first month of each three-month toxicity testing quarter assigned to the
facility. Effluent sampling for this testing must be obtained during representative effluent discharge and shall be
performed at the NPDES permitted final effluent discharge below all treatment processes.
If the test procedure performed as the first test of any single quarter results in a failure or ChV below the
permit limit, then multiple -concentration testing shall be performed at a minimum, in each of the two
following months as described in "North Carolina Phase II Chronic Whole Effluent Toxicity Test
Procedure" (Revised -December 2010, or subsequent versions).
All toxicity testing results required as part of this permit condition will be entered electronically using the
Division's eDMR system for the months in which tests were performed, using the parameter code TGP3B for the
pass/fail results and THP3B for the Chronic Value. Additionally, DWR Form AT-3 (original) is to be sent to the
following address:
North Carolina Division of Water Resources
Water Sciences Section/Aquatic Toxicology Branch
1621 Mail Service Center
Raleigh, NC 27699-1621
Or, results can be sent to the email, [e-mail].
Completed Aquatic Toxicity Test Forms shall be filed with the Water 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, accurate, include all supporting chemical/physical measurements and all
concentration/response data, and be certified by laboratory supervisor and ORC or approved designate signature.
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 Water Sciences Section at the
address cited above.
Should the permittee fail to monitor during a month in which toxicity monitoring is required, monitoring will be
required during the following month. Assessment of toxicity compliance is based on the toxicity testing quarter,
which is the three-month time interval that begins on the first day of the month in which toxicity testing is
required by this permit and continues until the final day of the third month.
Should any test data from this monitoring requirement or tests performed by the North Carolina Division of
Water Resources indicate potential impacts to the receiving stream, this permit may be re -opened and modified
to include alternate monitoring requirements or limits.
Page 9 of 19

DocuSign Envelope ID: BE4B49F0-FCB3-4935-8395-089B8438A007
Permit NC0026441
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.
Page 10 of 19

DocuSign Envelope ID: BE4B49F0-FCB3-4935-8395-089B8438A007
Permit NCO026441
A. (6.) EFFLUENT POLLUTANT SCAN AND SECOND SPECIES TOXICITY TESTING
[G. S. 143-215.1(b)]
The Permittee shall perform a total of three (3) Effluent Pollutant Scans for all parameters listed below. One scan
must be performed in each of the following years: 2024, 2025, and 2026. Analytical methods shall be in
accordance with 40 CFR Part 136 and shall be sufficiently sensitive to determine whether parameters are present in
concentrations greater than applicable standards and criteria. Samples should be collected with one quarterly toxicity
test each year, and must represent seasonal variation [i.e., do not sample in the same quarter every year]. Unless
otherwise indicated, metals shall be analyzed as "total recoverable."
Ammonia (as N)
C0610
Trans-1,2-dichloroethylene
34546
Bis (2-chloroethyl) ether
34273
Chlorine (total residual, TRC)
50060
1, 1 -dichloroethylene
34501
Bis (2-chloroisopropyl) ether
34283
Dissolved oxygen
00300
1,2-dichloropropane
C0541
Bis (2-ethylhexyl) phthalate
CO100
Nitrate / Nitrite
00630
1,3-dichloropropylene
77163
4-bromophenyl phenyl ether
34636
Kjeldahl nitrogen
00625
Ethylbenzene
34371
Butyl benzyl phthalate
34292
Oil and grease
00556
Methyl bromide
34413
2-chloronaphthalene
34581
Phosphorus
C0665
Methyl chloride
34418
4-chlorophenyl phenyl ether
34641
Total dissolved solids
70295
Methylene chloride
34423
Chrysene
34320
Hardness
00900
1,1,2,2-tetrachloroethane
81549
Di-n-butyl phthalate
39110
Antimony
01097
Tetrachloroethylene
34475
Di-n-octyl phthalate
34596
Arsenic
01002
Toluene
34010
Dibenzo(a,h)anthracene
34556
Beryllium
01012
1, 1, 1 -trichloroethane
34506
1,2-dichlorobenzene
34536
Cadmium
01027
1,1,2-trichloroethane
34511
1,3-dichlorobenzene
34566
Chromium
C0034
Trichloroethylene
39180
1,4-dichlorobenzene
34571
Copper
01042
Vinyl chloride
39175
3,3-dichlorobenzidine
34631
Lead
01051
Acid -extractable compounds:
Diethyl phthalate
34336
Mercury (Method 1631E)
COMER
P-chloro-m-cresol
34452
Dimethyl phthalate
34341
Nickel
01067
2-chlorophenol
34586
2,4-dinitrotoluene
34611
Selenium
01147
2,4-dichlorophenol
34601
2,6-dinitrotoluene
C0626
Silver
01077
2,4-dimethylphenol
34606
1,2-diphenylhydrazine
34346
Thallium
01059
4,6-dinitro-o-cresol
34657
Fluoranthene
C0376
Zinc
01092
2,4-dinitrophenol
34616
Fluorene
34381
Cyanide
00720
2-nitrophenol
34591
Hexachlorobenzene
C0700
Total phenolic compounds
32730
4-nitrophenol
34646
Hexachlorobutadiene
C0702
Volatile ormanic compounds:
Pentachlorophenol
39032
Hexachlorocyclo-pentadiene
34386
Acrolein
34210
Phenol
34694
Hexachloroethane
34396
Acrylonitrile
34215
2,4,6-trichlorophenol
34621
Indeno(1,2,3-cd)pyrene
34403
Benzene
34030
Base -neutral compounds:
Isophorone
34408
Bromoform
32104
Acenaphthene
34205
Naphthalene
34696
Carbon tetrachloride
32102
Acenaphthylene
34200
Nitrobenzene
34447
Chlorobenzene
34301
Anthracene
CO220
N-nitrosodi-n-propylamine
34428
Chlorodibromomethane
34306
Benzidine
39120
N-nitrosodimethylamine
34438
Chloroethane
85811
Benzo(a)anthracene
C0526
N-nitrosodiphenylamine
34433
2-chloroethyl vinyl ether
34576
Benzo(a)pyrene
34247
Phenanthrene
34461
Chloroform
32106
3,4 benzofluoranthene
34230
Pyrene
34469
Dichlorobromomethane
32101
Benzo(ghi)perylene
34521
1,2,4-trichlorobenzene
C0551
1,1-dichloroethane
34496
Benzo(k)fluoranthene
34242
1,2-dichloroethane
32103
Bis (2-chloroethoxy) methane
34278
Reporting. Test results shall be reported electronically using the Division's eDMR system or on DWR Form
DMR-PPA-1(or on a form approved by the Director) by December 3 1 " of each designated sampling year. The
Page 41 of 19

DocuSign Envelope ID: BE4B49F0-FCB3-4935-8395-089B8438A007
Permit NC0026441
Permittee must at least report completion of the test in the eDMR system by entering "1" or "Y" for parameter
code NCO - Annual Pollutant Scan. If utilizing the DWR Form submit to the following address:
NC DEQ / DWR / NPDES Files, 1617 Mail Service Center, Raleigh, North Carolina 27699-1617.
Or the form may be uploaded at: https://edocs.deq.nc.gov/Forms/NPDES_WW-EDMR-Supplemental-Form
Additional Toxicity Testing Requirements for Municipal Permit Renewal. Please note that Municipal
facilities that are subject to the Effluent Pollutant Scan requirements listed above are also subject to additional
toxicity testing requirements specified in Federal Regulation 40 CFR 122.210)(5). The US EPA requires four (4)
toxicity tests for a test organism other than the test species currently required in this permit. The multiple species
tests should be conducted either quarterly for a 12-month period prior to submittal of the permit renewal
application, or four tests performed at least annually in the four and one half year period prior to the application.
Samples should be collected with one quarterly toxicity test each year, and must represent seasonal variation
[i.e., do not sample in the same quarter every year]. These tests shall be performed for acute or chronic toxicity,
whichever is specified in this permit. The multiple species toxicity test results shall be filed with the Aquatic
Toxicology Branch at the following address:
North Carolina Division of Water Resources
Water Sciences Section/Aquatic Toxicology Branch
1621 Mail Service Center
Raleigh, North Carolina 27699-1621
Or, results can be sent to the email: ATFonns.ATBkncdenr.gov.
Contact the Division's Aquatic Toxicology Branch at 919-743-8401 for guidance on conducting the additional
toxicity tests and reporting requirements. Results should also be summarized in Part E (Toxicity Testing Data) of
EPA Municipal Application Form 2A, when submitting the permit renewal application to the NPDES Permitting
Unit.
Page 12 of 19

DocuSign Envelope ID: BE4B49F0-FCB3-4935-8395-089B8438A007
Permit NCO026441
A. (7.) CALCULATION OF TOTAL NITROGEN LOADS [G.S. 143-215.1(b)]
a. The Permittee shall calculate monthly and annual TN Loads as follows:
i. Monthly TN Load (lb/mo) = TN X TMF X 8.34
where:
TN = the average Total Nitrogen concentration (mg/L) of the composite
samples collected during the month;
TMF = the Total Monthly Flow of wastewater discharged during the month
(MG/mo); and
8.34 = conversion factor, from (mg/L X MG) to pounds
Annual TN Load (lb/yr) = Sum of the 12 monthly TN Loads for the calendar year.
b. The Permittee shall report monthly Total Nitrogen results (mg/L and lb/mo) in the appropriate discharge
monitoring report for each month and shall report each calendar year's results (lb/yr) with the December report
for that year.
A.(8.) NITROGEN OPTIMIZATION INCLUDING PRETREATMENT PROGRAM UPDATES [G.S.
143-215.1(b)]
Nitrogen Removal Optimization Requirements
a. By January 30, 2023 (90 days after the permit effective date), the Permittee shall:
i. Implement recommendations outlined in the Total Nitrogen Removal Optimization report, submitted
to the Division in November 2020.
ii. Submit a quarterly report to the Division documenting implementation of the optimization report
recommendations and describing expected results. The Permittee shall report any noncompliance
events as required by Standard Conditions (Part II).
iii. This requirement will terminate upon receipt of the Engineer's Certificate of completion for
expansion to 6.0 MGD.
b. Reports shall be submitted to:
NCDENR / DWQ / NPDES Permitting
1617 Mail Service Center
Raleigh, NC 27699-1617
Pretreatment Program Updates [15A NCAC 021-1.09001
a. By December 1, 2022 (30 days after the permit effective date), the Permittee shall:
i. Update and submit for Division approval any draft Industrial User Permit(s) (IUPs) and any future
IUP(s) including nutrient limits to be aligned with the NPDES compliance schedule [See A. (9.)].
ii. Issue the above IUP(s) within 30 days of Division approval.
iii. Issue an IUP to the Town's Water Treatment Plant with TSS, Total Iron and any other applicable
limits to address pass through and interference with the WWTP.
iv. Submit all SIU permit changes as required in Special Conditions for Municipal Facilities Part IV
Section C — Municipal Control of Pollutants from Industrial Users.
Page 43 of 49

DocuSign Envelope ID: BE4B49F0-FCB3-4935-8395-089B8438A007
Permit NCO026441
A. (9.) COMPLIANCE SCHEDULE FOR FACILITY EXPANSION TO 6.0 MGD AND TOTAL
NITROGEN LOAD LIMITATIONS [G.S. 143-215.1(b)]
1. By November 30, 2022, the Permittee shall complete design and submit an Authorization to Construct
(AtC) Permit application to the Division for expansion to 6.0 MGD.
2. By February 1, 2023, the Permittee shall submit a report to the Division summarizing actions taken since
the permit effective date through December 2022 toward expansion construction and compliance with the
TN Load limitations.
3. By December 31, 2023, the Permittee shall achieve compliance with the interim TN limit of 146,117 lb/yr
(for the 2023 calendar year).
4. By February 1, 2024, the Permittee shall submit a report to the Division summarizing actions taken during
the 2023 calendar year toward expansion construction and compliance with the TN Load limitations.
5. By August 31, 2024, the Permittee shall complete construction of the third treatment train with a capacity
of 2 MGD.
6. By December 31, 2024, the Permittee shall complete construction of the 6.0 MGD expansion and submit
to the Division an Engineer's Certificate of completion.
7. By December 31, 2024, the Permittee shall achieve compliance with the weighted TN limit of 115,678
lb/yr [combined mass of an eight -month load at 146,117 lb/yr (i.e., 97,411 lb) from 1/l/2024-8/31/2024
and a four -month load at 58,800 lb/yr (i.e., 18,267 lb/yr) from 9/l/2024-12/31/2024].
8. The Permittee shall achieve compliance with the final TN Load limit of 54,800 lb/yr by December 31,
2025 (for the 2025 calendar year).
All reports shall include the owner's name, NPDES permit number and Permittee contact person, and shall be
submitted to:
(1) NCDEQ / Division of Water Resources NPDES
Permitting
1617 Mail Service Center
Raleigh, NC 27699-1617
A. (10.) NUTRIENT REOPENER [G.S. 143-215.1(b)]
(2) NCDEQ / Division of Water Resources
Raleigh Regional Office
3800 Barrett Drive
Raleigh, NC 27604
In the event that Permittee proposes to accept future industrial process wastewater, including additional
wastewaters from Mountaire Farms, and that wastewater is expected to contain concentrations of Total Nitrogen
(TN) and/ or Total Phosphorus (TP) greater than typical domestic wastewater concentration (i.e. greater than 40.0
mg/L TN or greater than 5.0 mg/L TP), the Permittee shall notify the NPDES Municipal Permitting Unit of the
Division at 1617 Mail Service Center, Raleigh, NC 27699 and the Raleigh Regional Office at 3800 Barrett Drive,
Raleigh, NC 27609 within 30 days of knowledge that the Town is considering accepting new industrial process
wastewater containing excess nutrients. The notification shall contain information regarding the proposed
discharge flow, composition, and amenability to treatment at the Siler City WWTP. Changes in effluent
characteristics may require a permit modification, so notification should be at least 180 days prior to the start of
the proposed discharge.
Based on information provided by the Town regarding a potential new industrial process wastewater with high
nutrient concentration, and pursuant to N.C. General Statute Section 143-215.1 and the implementing rules found
in Title 15A of the North Carolina Administrative Code, Subchapter 2H, specifically, 15A NCAC 2H.0112(b) (1)
and 2H.0114(a), and Part II, Conditions B-12 and B-13 of this permit, the Director of DWR may then reopen this
permit to require supplemental nutrient limits for Total Nitrogen and/or Total Phosphorus in accordance with the
current Basin Plan for the Cape Fear River Basin.
Page 14 of 19

DocuSign Envelope ID: BE4B49F0-FCB3-4935-8395-089B8438A007
Permit NCO026441
A. (11.) NUTRIENT WATER QUALITY MODELING REOPENER [G.S. 143-215.1(b)]
Pursuant to N.C. General Statutes Section 143-215.1 and the implementing rules found in the North Carolina
Administrative Code at 15A NCAC 2H.0112 (b) (1) and 2H.0114 (a) and Part II sections B-12 and B-13 of this
permit, the Director of DWR may reopen this permit to require supplemental nutrient monitoring of the discharge.
The purpose of the additional monitoring will be to support water quality modeling efforts within the Cape Fear
River Basin and shall be consistent with a monitoring plan developed jointly by the Division and affected
stakeholders. In addition, the results of water quality modeling may require that limits for total nitrogen and total
phosphorus be imposed or modified in this permit upon renewal.
A. (12.) MERCURY MINIMIZATION PLAN (MMP) [G.S. 143-215.1 (b)]
The Permittee shall maintain and continue to implement the Mercury Minimization Plan (MMP) developed in the
previous permit term. The MMP shall continue to be available for inspection on -site. The MMP should place
emphasis on identification of mercury contributors and goals for reduction. Results shall be summarized and
submitted with the next permit renewal. Performance of the MMP will meet the requirements of the TMDL (Total
Maximum Daily Load) for mercury approved by USEPA on October 12, 2012, unless and until a Waste Load
Allocation specific to this facility is developed and this NPDES permit is amended to require further actions to
address the Waste Load Allocation.
A. (13.) 1,4-DIOXANE RE -OPENER [NCGS 143-215.1 (b)]
Pursuant to N.C. General Statutes Section 143-215.1 and the implementing rules found in the North Carolina
Administrative Code at 15A NCAC 2H.0112 (b) (1) and 2H.0114 (a) and Part II, Sections B-12 and B-13 of this
permit, the Director of DWR may reopen this permit to modify permit requirements to address 1,4-Dioxane
monitoring, treatment and/or compliance upon evaluation of collected monitoring data for potential effluent limits.
A. (14.) PFAS MONITORING REQUIREMENT [G.S. 143-215.l(b.)]
This reporting requirement for the per- and polyfluoroalkyl substances (PFAS) parameters listed under Table 1 of
the Final Method 1633 takes effect the first full calendar quarter following six (6) months after EPA publishes a
40 CFR part 136 Final PFAS Method for wastewater in the Federal Register. Monitoring will be at a quarterly
frequency.
Find the current parameters listed under Table 1 of the August 2021 Draft Method 1633 Analysis of Per- and
Polyfluoroalkyl Substances (PFAS) in Aqueous, Solid, Biosolids, and Tissue Samples by LC-MS/MS at:
https://www.epa.gov/system/files/documents/2021-09/method_1633_draft_aug 2021.pdf
Page 45 of 49

DocuSign Envelope ID: BE4B49F0-FCB3-4935-8395-089B8438A007
Permit NCO026441
A. (15.) ELECTRONIC REPORTING OF MONITORING REPORTS [G.S. 143-215.1(b)]
Federal regulations require electronic submittal of all discharge monitoring reports (DMRs) and program reports.
The final NPDES Electronic Reporting Rule was adopted and became effective on December 21, 2015.
NOTE: This special condition supplements or supersedes the following sections within Part II of this permit
(Standard Conditions for NPDES Permits):
• Section B. (11.) Signatory Requirements
• Section D. (2.) Reporting
• Section D. (6.) Records Retention
• Section E. (5.) Monitoring Reports
1. Reporting Requirements [Supersedes Section D. (2.) and Section E. (5.) (a)1
The permittee shall report discharge monitoring data electronically using the NC DWR's Electronic Discharge
Monitoring Report (eDMR) internet application.
Monitoring results obtained during the previous month(s) shall be summarized for each month and submitted
monthly electronically using eDMR. The eDMR system allows permitted facilities to enter monitoring data
and submit monthly DMRs electronically using the internet. The eDMR system may be accessed at:
https:Hdeq.nc.gov/about/divisions/water-resources/edmr.
If a permittee is unable to use the eDMR system due to a demonstrated hardship or due to the facility being
physically located in an area where less than 10 percent of the households have broadband access, then a
temporary waiver from the NPDES electronic reporting requirements may be granted and discharge
monitoring data may be submitted on paper DMR forms (MR 1, 1. 1, 2, 3) or alternative forms approved by
the Director. Duplicate signed copies shall be submitted to the following address:
NC DEQ / Division of Water Resources / Water Quality Permitting Section ATTENTION:
Central Files
1617 Mail Service Center
Raleigh, North Carolina 27699-1617
See "How to Request a Waiver from Electronic Reporting" section below.
Regardless of the submission method, the first DMR is due on the last day of the month following the issuance
of the permit or in the case of a new facility, on the last day of the month following the commencement of
discharge.
Starting on December 21, 2025, the Permittee must electronically report the following compliance monitoring
data and reports, when applicable:
Sewer Overflow/Bypass Event Reports;
Pretreatment Program Annual Reports; and
Clean Water Act (CWA) Section 316(b) Annual Reports.
The permittee may seek an electronic reporting waiver from the Division (see "How to Request a Waiver from
Electronic Reporting" section below).
Page 16 of 19

DocuSign Envelope ID: BE4B49F0-FCB3-4935-8395-089B8438A007
Permit NC0026441
2. Electronic Submissions
In accordance with 40 CFR 122.41(1)(9), the permittee must identify the initial recipient at the time of each
electronic submission. The Permittee should use the EPA's website resources to identify the initial recipient
for the electronic submission.
Initial recipient of electronic NPDES information from NPDES-regulated facilities means the entity (EPA or
the state authorized by EPA to implement the NPDES program) that is the designated entity for receiving
electronic NPDES data [see 40 CFR 127.2(b)].
EPA plans to establish a website that will also link to the appropriate electronic reporting tool for each type
of electronic submission and for each state. Instructions on how to access and use the appropriate electronic
reporting tool will be available as well. Information on EPA's NPDES Electronic Reporting Rule is found at:
https://www.federalre ig s�gov/documents/2015/10/22/2015-24954/national-pollutant-discharge-
elimination-system-nodes-electronic-renorting-rule.
Electronic submissions must start by the dates listed in the "Reporting Requirements" section above.
3. How to Request a Waiver from Electronic Reporting
The Permittee may seek a temporary electronic reporting waiver from the Division. To obtain an electronic
reporting waiver, a permittee must first submit an electronic reporting waiver request to the Division. Requests
for temporary electronic reporting waivers must be submitted in writing to the Division for written approval
at least sixty (60) days prior to the date the facility would be required under this permit to begin submitting
monitoring data and reports. The duration of a temporary waiver shall not exceed five (5) years and shall
thereupon expire. At such time, monitoring data and reports shall be submitted electronically to the Division
unless the Permittee re -applies for and is granted a new temporary electronic reporting waiver by the Division.
Approved electronic reporting waivers are not transferrable. Only permittees with an approved reporting
waiver request may submit monitoring data and reports on paper to the Division for the period that the
approved reporting waiver request is effective.
Information on eDMR and the application for a temporary electronic reporting waiver are found on the
following web page:
http://deq.nc.gov/about/divisions/water-resources/edmr
4. Signatory Requirements [Supplements Section B. (11.) (b) and Supersedes Section B. (11.) (d)1
All eDMRs submitted to the permit issuing authority shall be signed by a person described in Part II, Section
B. (11.)(a) or by a duly authorized representative of that person as described in Part II, Section B. (I 1.)(b). A
person, and not a position, must be delegated signatory authority for eDMR reporting purposes.
For eDMR submissions, the person signing and submitting the DMR must obtain an eDMR user account and
login credentials to access the eDMR system. For more information on North Carolina's eDMR system,
registering for eDMR and obtaining an eDMR user account, please visit the following web page:
http://deq.nc. gov/about/divisions/water-resources/edmr
Certification. Any person submitting an electronic DMR using the state's eDMR system shall make the
following certification [40 CFR 122.22]. NO OTHER STATEMENTS OF CERTIFICATION WILL BE
ACCEPTED:
7 certify, under penalty of law, that this document and all attachments were prepared under my direction or
supervision in accordance with a system designed to assure that qualified personnel properly gather and
evaluate the information submitted. Based on my inquiry of the person or persons who manage the system,
Page 17 of 19

DocuSign Envelope ID: BE4B49F0-FCB3-4935-8395-089B8438A007
Permit NCO026441
or those persons directly responsible for gathering the information, the information submitted is, to the best
of my knowledge and belief, true, accurate, and complete. I am aware that there are significant penalties for
submitting false information, including the possibility of fines and imprisonment for knowing violations. "
5. Records Retention [Supplements Section D. (6.)]
The Permittee shall retain records of all Discharge Monitoring Reports, including eDMR submissions. These
records or copies shall be maintained for a period of at least three (3) years from the date of the report. This
period may be extended by request of the Director at any time [40 CFR 122.4 1].
Page 18 of 19

DocuSign Envelope ID: BE4B49F0-FCB3-4935-8395-089B8438A007
Permit NCO026441
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Page 19 of 19

o°
MASS TRANSFER SYSTEMS, INC.
100 Waldron Road, Fall River, MA 02720-4732
MT7_7�'s
Tel. [phone] ® Fax [phone]
JET AERATION AND
MIXING SYSTEM
SUBMITTAL DATA
FOR
TOWN OF SILER CITY, NORTH CAROLINA
WASTEWATER TREATMENT
PLANT EXPANSION
SRF NO. CS370427-04
SPECIFICATION SECTION 12
-OXIDATION DITCHES-
-SLUDGE HOLDING TANKS-
-FLASH MIXING TANK-
MTS#M91-143
JUNE 2, 1992
ENGINEER:
HOBBS, UPCHURCH & ASSOCIATES
290 S.W. BROAD STREET
SOUTHERN PINES, NC 28388
CONTRACTOR:
STATE UTILITY CONTRACTORS, INC.
MONROE, NC
MTS REPRESENTATIVE:
COMBS & ASSOCIATES, INC.
P. O. BOX 32185
CHARLOTTE, NC 28232-2185
[phone]

I W.1 Iola offU 1► I Diem 9
I. SYSTEM DESCRIPTION
11. MATERIAL SPECIFICATION
III .DRAWINGS AND DETAILS

as 11 will a na V to)g
OXIDATION DITCHES
The Mass Transfer Systems, Inc. Jet Aeration System is designed to provide
oxygen transfer and mixing for the specified application described in the
following design parameters located in this section.
The aeration equipment supplied for each oxidation ditch consists of three
(3) MT2JM-30 jet aeration manifolds. Refer to Scope of Supply provided in this
section for additional information about material being supplied by MTS for this
project.
Each jet aeration manifold system recirculates the liquid contents of the
oxidation ditch. The liquid is recirculated through each jet aeration manifold
using a recirculation pump. As the liquid enters the jet aeration manifold it
pressurizes, and is then dispersed into the jet aeration nozzles which consist of a
primary (inner) and secondary (outer) jet nozzle. As the liquid passes through
the primary nozzle it comes in contact with the low pressure air that is passing
through the secondary jet nozzle. The result is a fine bubble stream discharged
horizontally across the bottom of the basin or tank at equally spaced intervals.
This provides oxygen transfer and mixing throughout the oxidation ditches.
Refer to MTS Design Parameters provided in this section for additional design
criteria.

SILER CITY, NORTH CAROLINA
DESIGN PARAMETERS --OXIDATION DITCHES
Process
Number
of Basins
Basin Dimensions (ft.)
Overall Length
Channel Width
S.W.D.
Basin Volume (Mil. Gallons)
Design
Flow Rate (m.g.d.)
Design
Influent BODE (mg/l)
Design
Effluent BOD5 (mg/1)
Design
Influent NH3-N (mg/1)
Design
Effluent NH3-N (mg/1)
lb 02/lb
BOD Removed
lb 02/lb
NH3-N Removed
Alpha
Beta
Residual D.O. (mg/1)
Theta
Temp. (°C)
Elevation (ft.)
SRT (days)
F/M
Design MLSS Concentration (mg/1)
Influent Alkalinity (mg/1)
Stoichiometric Alkalinity Required (mg/1)
Net Alkalinity Requirement (mg/1)l
Domestic Wastewater - Oxidation Ditch
2
200
40
20
2.2
4.0
350
5
45
1
1.3
4.6
0.70
0.95
2.0
1.024
20
600
17
0.085
4000
105
321
112
1 Assumes 40-50 mg/l in effluent and denitrification regain

SILER CITY, NORTH CAROLINA
MTS DESIGN SUMMARY OXIDATION DITCHES
Actual Oxygen Required (lbs/d)
per Basin 10,857
Total 21,714
Standard Oxygen Required (lbs/hr)
per Basin 866
Total 1732
MTS Jet Aerators Required
per Basin 3@MT2JM-30 Jet Manifolds
Total 6@MT2JM-30 Jet Manifolds
Airflow Required (SCFM)
per Aerator 869/11851
per Basin' 2923
Total 5846
Approximate Compressor Discharge
Pressure (psig)(2)
9.0
Oxygen Absorption Efficiency (%)
28.6
Liquid Recirculation Required (gpm)
per Aerator
5490
per Pump
5490
per Basin
16,470
Total Power Required (BHP)
Compressors(3)
315
Pumps(4)
200
Total
515
Oxygen Transfer Efficiency (lbs Std. 02/BHP-hr)
3.4
Power Density (BHP/MG)
117
Horizontal Bulk Fluid Velocity (ft/sec)
1.2
(1) 2 headers @ 869 SCFM, 1 header @ 1185 SCFM
(2) Assumes 1.0 psig loss -compressor inlet to basin edge
(3) Assumes 900F, 600 ft. elevation
(4) Assumes 2 ft. losses from pump suction to aerator, 75% efficiency