PERMIT RATIONALE FOR REISSUANCE
Okolona POTW, South
Chickasaw County
Okolona, Mississippi
Water NPDES No. MS0025631
September 2019

I.	CLASSIFICATION –Municipal NPDES Minor 

II.	DESCRIPTION OF WASTEWATER – Domestic / Municipal Wastewater

DESCRIPTION OF WASTEWATER TREATMENT – Wastewater is biologically treated by means of a conventional lagoon followed by sand filtration.  Effluent is disinfected by means of ultra-violet light. No increase in flow is proposed within the application.

III.	RECEIVING WATERS – Unnamed Tributary of Mattubby Creek. The receiving waters are located within the Tombigbee River Basin, and are classified as Fish and Wildlife. The receiving stream does not appear on the current 303(d) List of Impaired Water Bodies. The discharge is included in a completed TMDL for Biological Impairment due to Nutrients and Organic Enrichment / Low Dissolved Oxygen for Mattubby Creek. As permitted this permit will comply with the existing TMDL. In addition, the discharge is listed in the Fecal Coliform TMDL for Mattubby Creek, which the facility complies with via disinfection. 

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. 66 MGD or 1.02 cfs
		 Qr = Receiving stream 7Q10, 0.0 cfs.

IWC = {(1.02 cfs)/(1.02 cfs + 0.0 cfs)}*100 = 100%

IV.	APPLICABLE GUIDELINES – 11 MS Admin Code, Municipal Facility Guidelines (Technology), 2019 Wasteload Allocation (WLA)

V.	SUMMARY OF LIMITATIONS –
Parameter				Flow					Basis
Flow					0.66 MGD				Design
BOD5					10 mg/l 					Previous Permit
BOD (Percent Removal)			85% Minimum				Technology
TSS					30 mg/l 					Previous Permit
TSS (Percent Removal)			85% Minimum				Previous Permit
*E. Coli					126 Col./100 ml				Admin Code
Dissolved Oxygen 			6.0 mg/l Minimum			Previous Permit
pH					6.0 – 9.0 SU				Admin Code
NH3-N					2 mg/l 					TMDL
Nitrogen, Total				63.3 lbs/day 			 	TMDL
Phosphorus, Total 			28.62 lbs/day 				TMDL		
	
*E. Coli has replaced Fecal Coliform as the Pathogen Indicator and seasonal Limitations have been removed. Accordingly, please note updated numeric limitations in the Summary of Limitations section of the permit.