PERMIT RATIONALE FOR REISSUANCE
Coahoma POTW
Coahoma County
Coahoma, Mississippi
Water NPDES No. MS0044237
October 2025

I.	CLASSIFICATION –Municipal NPDES Minor 

II.	DESCRIPTION OF WASTEWATER – Domestic / Municipal Wastewater

III.	DESCRIPTION OF WASTEWATER TREATMENT – Wastewater is collected and treated by means of activated sludge system followed by disinfection. The effluent is further treated via sand filters. No increase in flow is proposed within the application.

IV.	RECEIVING WATERS – Mill Creek. The receiving water is located within the Yazoo River Basin, and is classified as Fish and Wildlife.  These waterbodies do not appear on the current State of Mississippi 303(d) list of impaired waterbodies. The discharge is listed in a pathogen TMDL. The facility disinfects the effluent in order to comply with State criteria for pathogens (fecal coliform), which complies with the TMDL. The discharge is also listed in a nutrient and organic enrichment / low do TMDL. The TMDL does recommend nutrient monitoring for Total Nitrogen and Total Phosphorus. This condition has been included in the permit.

At the point of discharge the 7Q10 for the receiving stream is 0.09 cfs.  The instream wastewater concentration at the point of discharge can be determined by the following calculation:

IWC = {(Qw)/(Qw + Qr)}*100

	Where, Qw = Design flow of the wastewater treatment facility, 0.05 MGD or 0.078 cfs
		 Qr = Receiving stream 7Q10, 0.09 cfs.

IWC = {(0.078 cfs)/(0.078 cfs + 0.09 cfs)}*100 = 46%

I.	APPLICABLE GUIDELINES – 11 Mississippi Admin Code pt. 6, Municipal Facility Guidelines (Technology), State of Mississippi Water Quality Criteria (MSWQS), Wasteload Allocation (WLA)

II.	SUMMARY OF LIMITATIONS –
Parameter				Flow					Basis
Flow					0.05 MGD				Design
BOD5					10 mg/l (Max Monthly Average)	WLA
BOD (Percent Removal)		85% Minimum				Technology
TSS					30 mg/l (Max Monthly Average)	Previous Permit
TSS (Percent Removal)			85% Minimum				Technology
E. Coli					126 Col./100 ml				WLA
pH					6.0 – 9.0 SU				WLA
Chlorine, Total Residual	 	0.024 mg/l / 0.041 mg/l			WLA
Dissolved Oxygen 	 		6.0 Minimum				WLA
NH3-N					2.0 mg/l (Max Monthly Average)	WLA
Nitrogen, Total 				Report					WLA
Phosphorus, Total			Report					WLA