PERMIT RATIONALE FOR REISSUANCE
Decatur POTW, Number 2
Newton County
Decatur,, Mississippi
Water NPDES No. MS0020621
June 2026

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 an aerated lagoon and a mixed-batch reactor for ammonia removal. The facility disinfects by chlorinating.  No increase in flow is proposed within the application.

IV.	RECEIVING WATERS – Anderson Branch thence into Okahatta Creek. The receiving waters are located within the Pascagoula River Basin, and are classified as Fish and Wildlife. Anderson Branch does not appear on the current State of Mississippi 303(d) list of impaired waterbodies. The discharge complies with the conditions of the TMDL by disinfecting the effluent in order to meet the water quality criteria for Fecal Coliform.

At the point of discharge the 7Q10 for the receiving stream is 0.0 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, 0.09 MGD or 0.14 cfs
		 Qr = Receiving stream 7Q10, 0.0 cfs.

IWC = {(0.14 cfs)/(0.14 cfs + 0.0 cfs)}*100 = 100%

V.	APPLICABLE GUIDELINES – 11 Mississippi Admin Code pt. 6, Wasteload Allocation (WLA)

VI.	SUMMARY OF LIMITATIONS –
Parameter			Flow					         Basis
Flow				0.09 MGD				         Design
BOD5				11.0 mg/l (Max Monthly Average)	         WLA
BOD (Percent Removal)	65% Minimum				         Admin Code
TSS				90 mg/l (Max Monthly Average)	         Admin Code
TSS (Percent Removal)		65% Minimum				         Admin Code
E. Coli				126 Col./100 ml	 (Max Monthly Average)        Admin Code	
Chlorine, Total Residual	0.011 mg/l 		                                   Admin Code, IWC
Dissolved Oxygen		6.0 Minimum				         WLA
pH				6.0 – 9.0 SU				         Admin Code
NH3-N	(Phase I)		2.0 mg/l (Max Monthly Average)	         WLA
NH3-N	(Phase II)		1.37 mg/l (Max Monthly Average)	        Ammonia Toxicity
Total Nitrogen			Report mg/l				         WLA
Total Phosphorus		Report mg/l				         WLA

Waste Load Allocation