PERMIT RATIONALE FOR REISSUANCE
Prentiss POTW
Jefferson Davis County
Prentiss, Mississippi
Water NPDES No. MS0029033
May 4, 2017

I.	CLASSIFICATION – Municipal NPDES

II.	DESCRIPTION OF WASTEWATER – Domestic Wastewater

III.	DESCRIPTION OF WASTEWATER TREATMENT – Domestic wastewater is collected and treated biologically by means of an aerated lagoon.  No increase in treated effluent flow is proposed within the application.  

IV.	RECEIVING WATERS – Big Whitesand Creek.  The receiving stream is located within the Pearl River Basin and is classified as Fish and Wildlife.  At the point of discharge the receiving stream does appear on the current State of Mississippi 303(d) list of evaluated or impaired waterbodies.  Specifically, waterbody ID 516111 is listed for biological impairment.  The listing is from the confluence of Little White Sand Creek to the Pearl River.  The discharge is listed in a completed Total Maximum Daily Load for Mercury in the Pearl River.  The 7Q10 of the receiving stream at the point of discharge is 7.1 cfs.  The instream wastewater concentration at the point of discharge is determined by the following calculation:

IWC = {(Qw)/(Qw + QR)}*100 
	Where:
	Qw = Design flow of the wastewater treatment facility, 0.604 MGD or 0.93 cfs
	QR = Receiving stream 7Q10, 7.1 cfs

IWC = {(0.93 cfs)/(0.93 cfs + 7.1 cfs)}*100 = 11.6 %

Only one discharge to surface waters is described within the application, with no increase in treated effluent flow proposed.  

V.	APPLICABLE GUIDELINES –State of Mississippi Wastewater Regulations,11 MS admin code part 6

VI.	SUMMARY OF LIMITATIONS –
	Parameter	Value				Basis
	Flow					0.604 MGD		Design
	BOD5					30 mg/l		Modeled
	TSS					90 mg/l		Technology
	Ammonia Nitrogen			Report mg/l		11 MS admin code part 6
	Dissolved Oxygen			> 6.0 mg/l		11 MS admin code part 6
	E.Coli	 				126 Col/100 ml		11 MS admin code part 6
	Chlorine, Total Residual		0.095 mg/l		WLA	
	pH					6.0 – 9.0 SU		11 MS admin code part 6
	
E. Coli will now be the bacterial indicator used for all freshwaters in MS designated as Recreation, Fish and Wildlife Support, and /or Public Water supply (replacing the use of fecal coliform).