PERMIT RATIONALE FOR REISSUANCE
Purvis POTW
Lamar County
Purvis, Mississippi
Water NPDES No. MS0036536
August 2023

I.	CLASSIFICATION – Municipal Minor NPDES 

II.	DESCRIPTION OF WASTEWATER – Domestic Wastewater

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

IV.	RECEIVING WATERS – Unnamed creek thence to Myers Bay Creek.  At the point of discharge the receiving stream is located within the Pascagoula River Basin and is classified as Fish and Wildlife.  At the point of discharge the receiving stream does not appear on the State of Mississippi 303(d) list of evaluated or impaired waterbodies nor has the receiving stream had a TMDL placed on it.  The 7Q10 of the receiving stream at the point of discharge is 0.1 cfs.  Therefore, the instream wastewater concentration (IWC) at the point of discharge is 88.56 %. Only one discharge to surface waters is described within the application with no increase in flow proposed.  

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

VI.	SUMMARY OF LIMITATIONS –
	Parameter					Value		Basis
	Flow					0.5 MGD		Design
	BOD5					10 mg/l		WLA
	BOD (Percent Removal)		65%		Admin Code
	TSS					30 mg/l 		Technology Based
	TSS (Percent Removal)		65%		Admin Code
	Ammonia Nitrogen	(Phase I)		2.0 mg/l 		WLA
	Ammonia Nitrogen	(Phase II)	1.53 mg/l 		WLA
	Dissolved Oxygen				> 6.0 mg/l 		Admin Code
	Chlorine, Total Residual		0.011 mg/l 		Admin Code
	pH					6.0 – 9.0 SU		Admin Code
	e. Coli					126 #col/ml		Admin Code
	Total Nitrogen					Report mg/l		WLA
	Total Phosphorus				Report mg/l		WLA

VII. 	CHANGES TO PERMIT

•	Ammonia Nitrogen has been phased from 2 mg/L to 1.53 mg/L in accordance to the most updated Wasteload Allocation. 

The following condition has been added to the permit to address phased limitations:

The permittee shall achieve compliance with the effluent limitations specified for discharge in accordance with the following schedule:

Upon issuance of this permit, the permittee shall achieve compliance with the effluent limitations specified for the parameters noted as Phase I; Phase II parameters shall not apply at this time.  Beginning upon completion and start-up of improvements needed to comply with the Phase II parameters, or by three (3) years after permit issuance, the facility shall comply with the parameters noted as Phase II ; Phase I parameters shall not apply at this time. The permittee shall notify our office orally at least 24 hours prior to start-up and in writing no later than 48 hours after start-up of the needed improvements