PERMIT RATIONALE FOR REISSUANCE
Durant POTW
Holmes County
Durant, Mississippi
Water NPDES No. MS0048127
October 2025

I.	CLASSIFICATION – Municipal Minor Toxic

II.	DESCRIPTION OF WASTEWATER – Municipal/Domestic Wastewater

III.	DESCRIPTION OF WASTEWATER TREATMENT – Wastewater is collected and treated biologically by means of a 3-cell lagoon followed by disinfection with chlorination. No increase in flow is proposed within the application. 

IV.	RECEIVING WATERS – Big Black River. At the point of discharge, the Big Black River is not listed on the current State of Mississippi 303(d) List of Impaired Waterbodies. The facility is listed in a TMDL for Fecal Coliform. The facility complies with the TMDL via disinfection.  The discharge is also listed on a TMDL for low pH, which the permit addresses with numeric pH limitations. The receiving water is located within the Big Black River drainage basin, and is classified as Fish & Wildlife. 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, 1.47 cfs.
	Qr = Receiving stream 7Q10, 26 cfs.

IWC = {(1.47 cfs) / (1.47 cfs + 26 cfs)}*100 = 5.35 %

V.	APPLICABLE GUIDELINES – 11 MS Admin Code pt. 6, Municipal Facility Guidelines, 2019 Wasteload Allocation (WLA)

VI.	SUMMARY OF DISCHARGE LIMITATIONS – 

Parameter				Value				Basis
Flow				0.95 MGD			Design
BOD5				30 mg/l				WLA
BOD5 (Percent Removal)	65% Minimum			Technology
TSS				90 mg/l (Monthly Average)		Technology
TSS (Percent Removal)		65% Minimum			Technology
NH3-N				Report				WLA
Dissolved Oxygen			6.0 mg/l (Minimum)			WLA
E. Coli     				126 Col./100 ml			WLA
pH				6.0 – 9.0 S.U.			WLA
Chlorine, Total Residual	0.205 / 0.354 mg/l			WLA
Total Nitrogen				Report 				WLA
Total Phosphorus			Report				WLA
C. dubia				IC25>5.35%			WET
P. promelas					IC25>5.35%			WET

BIOASSAY AND CHEMICAL SPECIFIC EVALUATION

BIOASSAY

In accordance to 11 Mississippi Admin Code pt. 6, Durant POTW is required to perform Whole Effluent Toxicity (WET) tests as part of the renewal application.  The applicant should test in accordance with Short – Term Methods for estimating the Chronic Toxicity of Effluents and Receiving Water to Freshwater Organisms.  Short-term chronic WET tests should be performed on Ceriodaphnia dubia (invertebrate) and Pimephales promelas (vertebrate). Durant POTW submitted the following test results:

QTR 1
Ceriodaphnia dubia IC25 = 2.42%
Pimephales promelas IC25 >21.4%

QTR 2
Ceriodaphnia dubia IC25< 21.4%
Pimephales promelas IC25 >N/A

QTR 3
Ceriodaphnia dubia IC25 = 21.4%
Pimephales promelas IC25 =21.4%

QTR 4
Ceriodaphnia dubia IC25 >21.4%
Pimephales promelas IC25 >21.4%

All of the inhibition concentrations were not reported as greater than 5.35% IWC. Therefore, the WET monitoring and limitations are added to the proposed draft permit.

CHEMICAL SPECIFIC ANALYSIS

	Minor Toxic municipalities shall determine the toxic characteristics of their wastewater by analyzing for the toxic pollutant listed in Table III of appendix D of 40 CFR 122.  Chemical specific analysis shall be for total recoverable metals.  Municipalities shall submit twelve influent and effluent samples collected.  Chemical specific limits shall be placed in a permittee’s permit if any of the parameters evaluated in the toxic screening procedure indicated that reasonable potential for violations of the appropriate criteria (acute, chronic, and human health).

	The facility submitted no chemical specific lab data, therefore, the facility will be required to submit additional sample results.

Chemical specific analysis for Volatile Organics Compounds, Acid-Extractable Compounds, and Base-Neutral Compounds and Results 

Facility did not submit labs results of Volatile Compounds, Acid-Extractables, and Base-Neutrals

VII.	CHANGES FROM LAST REISUANCE

The following condition was added as a condition to the permit because of no submittal of chemical specific data:

“Mississippi Wastewater Regulations require that the influent to and the effluent from the wastewater treatment facility must be analyzed twice per month for a 6 month period for the chemicals listed below. The facility is required to submit a total of twelve (12) samples

Total Recoverable Antimony 
Total Recoverable Arsenic 
Total Recoverable Beryllium 
Total Recoverable Cadmium 
Total Recoverable Chromium 
Chromium (Hex) 
Total Recoverable Copper 
Total Recoverable Lead 
Total Recoverable Mercury 
Total Recoverable Nickel (Freshwater) 
Total Recoverable Selenium 
Total Recoverable Silver 
Total Recoverable Thallium 
Total Recoverable Zinc 
Free Cyanide 
Phenol 
Pentachlorophenol 
Hardness (in mg/l as CaCO3)

Please be aware that the chemical specific analysis must be performed by a method listed in 40 CFR 136 and with a Method Minimum Level (ML) at or below the level of the applicable water criterion for the measured pollutant parameter or the method has the lowest ML of the EPA approved analytical for the measured pollutant parameter. 

Sampling shall be initiated after 30 days of issuance of the permit and results shall be compiled and submitted to Mississippi Environmental Quality Board, POSTMARKED NO LATER THAN THE 28TH DAY OF THE MONTH FOLLOWING THE COMPLETION OF THIS MONITORING.”

Condition L-1 was added to proposed draft permit:

“The Permittee shall perform monitoring of and submit for all pollutants in order to complete Table C. Effluent Parameters for Selected POTWs, of the Form 2A application. Monitoring shall initiated no later than 30 days after issuance, and performed monthly until three (3) samples have been obtained from the effluent of each parameter. Mississippi results shall be compiled and submitted to Mississippi Environmental Quality Board. POSTMARK NO LATER THAN THE 28TH DAY OF THE MONTH FOLLOWING THETHIRD MONTH OF THIS MONITORING.”

Attachment No. 1