NC0026441_Nutrient Optimization Report (Q1 2024)_20240430

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Public Works and Utilities
NPDES#NC0026441
WWTP Nutrient Removal Optimization
Quarterly Report: 1st Quarter 2024
Introduction
In accordance with NPDES Permit requirements this report is provided to document implementation of the optimization
report and performance of the WWTP during the 1st quarter of 2024. The primary focus of this information is nutrient
removal, however data on plant operations for other parameters are included as they influence the nutrient removal
performance.
Phosphorus (TP) removal is achieved with chemical precipitation and performance has been consistently good with
effluent TP averaging less than 0.03 mg/I during the Vt quarter 2024. Therefore, no further review of TP operation is
included.
Optimization Report Recommendations
The optimization report was prepared in 2020 based on data from January to September of 2020. Operating parameters
at the time are shown in Table 1 below.
Table 1: Influent Wastewater during Optimization Study
Daily Daily Average
Parameter Average during for 3rd Quarter
Optimization 2023
2020
Flow (mgd) 3.26 3.12
BOD (mg/1) 228 222
NH3(mg/1) 19.5 20
TN (mg/1) 35.0 42.5
TKN (mg/L) 34.1
TSS (mg/1) 167
TP (mg/1) 3.34 1.8
The report recommends utilizing Simultaneous Nitrification/Denitrification (SNDN) to achieve nitrogen reduction.The
recommended parameters include maintaining dissolved oxygen (DO) in the oxidation ditches between 0.8 to 1.2 mg/I
and maintaining a FM ratio of 0.04 to 0.05 Ibs BOD/Lbs MLVSS with MLVSS between a concentration of 3,400 to 4,200
mg/l.
Optimization Implementation
During the 1st quarter of 2024 the overall performance of the Siler City WWTP has was mixed with relatively good
months in January and March and poor performance in February. The influent BOD has remained relatively low,similar
to the 2023 and influent TN concentrations were slightly lower this quarter.
During February excessive solids were received from the Water Treatment Plant with high iron concentrations which
caused a plant upset. The Town commenced higher frequency of pressing sludge and hauling sludge from the WTP
Chris McCorquodale
Director of Public Utilities [e-mail]
PO Box 769.311 N.Second Avenue Phone:[phone]•Fax:[phone]
Siler City,NC 27344-0769 www.silercity.org
To advance a framework for our success through balanced rdovernance,dynamic partnerships,and an en,da9ed community.

directly to the WWTP to sludge holding to minimize the potential for sludge in the biological process.The Town also
received two loads of mixed liquor from the Sanford WWTP to help reestablish the biology and worked with Hazen for
additional testing to get the plant back in shape.The plant was able to recover by approximately March 4, 2024 and
March testing indicates improved results.
The effluent TN concentration has come down some from previous quarters but remains somewhat higher than
desirable at an average of 15.66 mg/I for the quarter.The MLVSS concentration averaged 3,200 mg/I which is just below
the range recommended by the optimization report.
The performance for TN is above the optimization report target of 15 mg/I for two of the three months but is very close
with an average of 15.66 for the quarter. Flow during this quarter has increased, likely due to winter rainfall impacts.
The average mass TN discharged in Quarter 1 was approximately 12,200 Ibs/month with a total quarter mass of 36,673
lbs. Further optimization will be needed in 2024 to comply with the reduced annual limit.
Table 2: Nutrient Removal Performance for 1st Quarter 2024.
Influent I Effluent
Janua February_ March Average January February March Average
Flow 3.29 2.77 3.31 3.12
BOD 195 239 233 222 3.51 16.73 1.30 7.18
NH3 20 20 21 20 3.38 6.15 0.54 3.35
TN 39.6 41.8 46.1 42.5 15.10 17.70 14.17 15.66
TP 1.49 1.95 2.06 1.8 0.02 0.03 0.05 0.03
1. All concentrations reported in mg/I. Flow reported in MGD
Table 3: Operating Parameter Summary
anuary February March Average
MLSS (mg/1) 4465 4996 4976 4812
MLVSS (mg/1) 3154 3207 3267 3209
Ditch 1 DO (mg/1) 4.22 3.53 2.20 3.32
Ditch 2 DO (mg/1) 3.42 2.75 1.41 2.52
Conclusion
Overall plant performance during January and March was good but upsets in February resulted in high BOD and
ammonia during that period.The plants are continuing to prioritize sludge handling and solids levels in the basins are
close to optimization report recommendations.The performance during this period for Total Nitrogen was ok but is
slightly above the annual limit level if it continues at this pace.
Thank you,
Town of Siler City
ell
Chris McCorquodale
Chris McCorquodale
Director of Public Utilities [e-mail]
PO Box 769.311 N.Second Avenue Phone:[phone]•Fax:[phone]
Siler City,NC 27344-0769 www.silercity.org
To advance a frame work for our success through balanced governance,dynamic partnerships,and an engcWed community.