PERMIT RATIONALE FOR REISSUANCE
Winona POTW
Montgomery County
Winona, Mississippi
Water NPDES No. MS0021024
January 2025

I.	CLASSIFICATION – NPDES Major Municipal

II.	DESCRIPTION OF WASTEWATER – Municipal Wastewater

III.	DESCRIPTION OF WASTEWATER TREATMENT – Wastewater is biologically treated by means of an oxidation ditch. Disinfection is provided by chlorination. Dechlorination and post-aeration are also provided prior to discharge. The current design capacity of the facility is 1.2 MGD. See Attachment No. 1 for flow diagram.  Only one discharge to surface waters is described in the application with no increase in treated effluent flow proposed.  

IV.	RECEIVING STREAM – Hays Creek.  The receiving waters are located within the Big Black River Basin and is classified as Fish and Wildlife. See Attachment No. 2 for discharge location map.  At the point of discharge, the receiving stream does not appear on the State of Mississippi current Section 303(d) List of Impaired Waterbodies.  The discharge appears on a completed Total Maximum Daily Load (TMDL) for Pathogens (December 2006). The discharge also appears on a completed TMDL for pH (January 2018). These TMDLs do not propose any new limitations for this facility.

The 7-day, 10-year minimum flow (7Q10) of the receiving stream is 0.2 cfs. The Instream Wastewater Concentration (IWC) at the point of the discharge is determined by the following calculation:

IWC = {(QW)/(QW + QR)}*100
	Where:
	QW = Design flow of the wastewater treatment facility, 1.2 MGD or 1.86 cfs.
	QR = Receiving stream 7Q10, 0.2 cfs.

IWC = {(1.86 cfs)/(1.86 cfs + 0.2 cfs)}*100 = 90.28 %

V.	APPLICABLE GUIDELINES – 11 Mississippi Admin Code pt. 6, Municipal Facility Guidelines (Technology), Wasteload Allocation (WLA, see Attachment No. 3) Mississippi State Water Quality Standard (MSWQS)

VI.	CHANGES FROM PREVIOUS PERMIT –

Phase I CBOD has been removed from proposed draft permit. New ammonia limit added to the proposed draft.

Zinc permit reporting limitations has been added to the proposed draft permit (See Chemical Specific Analysis section).

Condition S-1 added to the proposed draft permit which requires facility to submit a study that re-evaluates its Copper WER study due no later than expiration of permit..

Condition L-1 has been added to the proposed draft permit that requires Winona to submit additional metals samples.

Condition M1-M6 added requiring Winona to submit additional WET tests. Condition L-6 added.

VII.	SUMMARY OF LIMITATIONS –

	Parameter				Value				Basis
	Flow					1.2 MGD			Design
	CBOD5 				9 mg/l				WLA	
TSS					30 mg/l 			Technology
	Phase I Ammonia Nitrogen		2.0 mg/l			WLA
	Phase II Ammonia Nitroegen		1.5 mg/l			WLA
	Dissolved Oxygen, Minimum				6.0 mg/l 			WLA
	E. coli								126 col./100 ml		WLA	
	Chlorine, Total Residual				0.012 mg/l 			WLA
	pH								6.0 – 9.0 SU			WLA
	Total Nitrogen							Report lbs/day			WLA		
	Total Phosphorus						Report lbs/day			WLA
	Copper, Total Recoverable				0.018 mg/l			Translator Study
	Zinc, Total Recoverable				Report, mg/l			Calculations/MSWQS
	C. Dubia							90.28% Minimum		MSWQS/IWC
	P. Promelas							90.28% Minimum  		MSWQS/IWC
		
The minimum and maximum values for Dissolved Oxygen in the aeration unit and the 30-minute sludge settleability in the aeration unit must be reported.

Phase 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 without a phase designation and for the parameters noted as Phase I; Phase II limitations shall not apply at this time.

Beginning upon completion and start-up of improvements needed to comply with Phase II limitations or three (3) years after the issuance of the permit, whichever comes first, the permittee shall achieve compliance with the effluent limitations specified for the parameters without a phase designation and for the parameters noted as Phase II; Phase I limitations shall no longer apply at this time. Phase II limitations shall apply as soon as the treatment system has demonstrated compliance with the Phase II limitations, but no longer than three (3) years after the issuance of the permit.

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.

The Permittee shall Submit an engineering report: Due within one year (365 days) after permit effective date The Report shall describe how the wastewater treatment system will come into compliance with the Phase II limitations.  The report, implementation schedule, and interim milestones will be enforceable conditions of the permit.

The Permittee shall Submit progress report: Due annually - every 1 year after effective date. Said report shall update the Permittee's progress in addressing needed upgrades to the wastewater treatment facility in order to meet the site's Phase II limitations. Said report should also include an updated schedule for completing these activities.

	Copper Requirements

In further establishing the Copper criteria the permittee developed a site specific biological translator that relates the existing water quality standard to a specific permit limit using the Water Effects Ratio (WER), as described in EPA guidance (No. 823-B-94-001), and 11 Mississippi Administration Code. Pt. 6. The study demonstrated that a WER of 7.0 would protect the designated use of the receiving stream. The opinion was to limit the WER to 3.8 in order to cap the existing Copper load. A WER of 3.8 would both protect designated use of the receiving stream, and cap the existing Copper load. Winona POTW will be required to re-evaluate the site-specific biological translator no later than permit expiration date.
	
BIOASSAY AND CHECMICAL SPECIFIC EVALUATIONS

BIOASSAY

In accordance to State Regulation 11 Mississippi Admin Code pt. 6, VI.B.2b., Winona POTW is required to perform a Whole Effluent Toxicity (WET) evaluation as part of the renewal application. The applicant was to have tested in accordance with Short – Term Methods for estimating the Chronic Toxicity of Effluents and Receiving Water to Freshwater Organisms.  Short – term chronic WET tests were performed on Ceriodaphnia dubia (invertebrate) and Pimephale promelas (vertebrate). Facility submitted one (1) out of four (4) quarterly bioessays:

June 2024
C. Dubia								IC25>90.25%	
P. promelas								IC25>90.25%

Winona submitted one (1) of the four (4) bioessays required. Faciility will be required to submit three more bioessays for a total of four to assess water toxicity.

CHEMICAL SPECIFIC ANALYSIS

Chemical specific analysis has been performed in accordance with State Regulations 11 Mississippi Admin Code pt. 6, V1.B1.  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.  The results are tabulated in Attachment No. 4.  The reported values are then analyzed and compared to water quality criteria (see Attachment No. 5) to determine any possible toxic effect to the receiving waters.  A synopsis of these calculations is listed in Attachment No. 6.  A column by column description of the calculations in Attachment No. 6 is hereby provided:

Column No. 1 – Maximum concentration.  The highest effluent reading of the parameter

Column No. 2 – The maximum concentration mixed with the receiving water IWC.  This is 			calculated by the following equation:

		{Maximum Concentration (Column 1) * IWC %} / 100

Column No. 3 – Acute allowable – Chemical Specific State Water Quality Criteria                                   
	Column No. 4 – Pass or Fail. If column 2 > column 3 water quality criteria is exceeded                                		and failure occurs.

Column No. 5 – Long term average (LTA) of all tests.  The summation of the 12 samples divided                                         by 12.

Column No. 6 – The long term average concentration mixed with the receiving water                                		 	IWC.  This is calculated by the following equation:

		{LTA Concentration (Column 5) * IWC%} / 100

Column No. 7 – Chronic allowable – Chemical Specific State Water Quality Criteria                                   
Column No. 8 – Pass or Fail. If column 6 > column 7 water quality criteria is exceeded                               			and failure occurs.

Column No. 9 – Human health determination.  Long term average (Column 5) is mixed                  		with the mean annual flow IWCMA .  This is calculated by the following equation:

{LTA Concentration (Column 5) * IWCMA %} / 100

Column No. 10 – Human health allowable – State Water Quality Criteria   Note: Organisms only                              column is used if receiving waters are not drinking water supply. 

	Column No. 11 – Pass or Fail.  If column 9 > column 10 water quality criteria is exceeded                       	         	 and failure occurs.

Chemical specific analysis for Metals and Results

Major municipalities shall determine the toxic characteristics of their wastewater by analyzing for toxic pollutants listed in Table III of Appendix D of 40 CFR 122.  Metal 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 indicate the reasonable potential for violation of the appropriate criteria (acute, chronic, and human health). 

For Winona POTW, the chemical specific data results of three (3) out of twelve (12) sample sets submitted with the reapplication indicated the reasonable potential for violation of the appropriate criteria by the power of 10 rule
 (Copper - acute, chronic and Zinc-acute, chronic) in Table III of Appendix D of CFR 122. See Attachment No . 6 for Chemical Specific Screening sheet and results. The facility will be required to submit additional nine (9) sample sets. 

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

The following Volatile Organic compounds were detected and evaluated for a potential to violate Human Health Criteria: 

Bromodichloromethane
Avg. Daily Concentration = 0.706 μg/L 

According to EPA’s National Recommended Water Quality Criteria, the Human Health Criteria (consumption of organism only) for the following compound(s) are shown below: 

Bromodichloromethane
Recommended Water Quality Criteria = 21 μg/L
 
Multiplying the average daily concentration above by 10 (due to a data set of less than 12 samples) determines the reasonable potential of the compound’s concentration to violate the Human Health Criteria. 
[0.706 ug/L * 10]= 7.06 μg/L 
17.06 μg/L < 27 μg/L 

The above results demonstrate that the average concentration(s) for Bromodichloromethane do not present a reasonable potential to violate Human Health Criteria.

Chloroform
Avg. Daily Concentration = 1.71 μg/L 

According to EPA’s National Recommended Water Quality Criteria, the Human Health Criteria (consumption of organism only) for the following compound(s) are shown below: 

Chloroform
Recommended Water Quality Criteria = 2000 μg/L
 
Multiplying the average daily concentration above by 10 (due to a data set of less than 12 samples) determines the reasonable potential of the compound’s concentration to violate the Human Health Criteria. 
[1.71 ug/L * 10]= 17.1 μg/L 
17.1 μg/L < 2000 μg/L 

The above results demonstrate that the average concentration(s) for Chloroform do not present a reasonable potential to violate Human Health Criteria.

Bromomethane
Avg. Daily Concentration = 14.23 μg/L 

According to EPA’s National Recommended Water Quality Criteria, the Human Health Criteria (consumption of organism only) for the following compound(s) are shown below: 

Bromodichloromethane
Recommended Water Quality Criteria = 10, 000 μg/L
 
Multiplying the average daily concentration above by 10 (due to a data set of less than 12 samples) determines the reasonable potential of the compound’s concentration to violate the Human Health Criteria. 
[14.23 ug/L * 10]= 140.23 μg/L 
1140.23 μg/L < 10,000 μg/L 

The above results demonstrate that the average concentration(s) for Bromomethane do not present a reasonable potential to violate Human Health Criteria.

The chemical specific data results submitted had no detects for Acid-Extractable and Base-Neutral Compounds.

ATTACHMENTS

Attachment No. 1 – Flow Diagram
Attachment No. 2 – Discharge Location Map
Attachment No. 3 – Wasteload Allocation
Attachment No. 4 – Tabulated Metals Testing Data
Attachment No. 5 – MS State Water Quality Standards
Attachment No. 6 – Synopsis of Metals Results

Attachment No. 1 – Flow Diagram

	
Attachment No. 2 – Discharge Location Map

Attachment No. 3 – Wasteload Allocation

Attachment No. 4 - Tabulated Metals Testing Data

Attachment No. 5 - MS State Water Quality Standards

Attachment No. 6 - Synopsis of Metals Results