PERMIT RATIONALE FOR MODIFICATION
Ripley POTW
Tippah County
Ripley, Mississippi
Water NPDES No. MS0020958
September 2023

I.	CLASSIFICATION –Municipal NPDES Major 

II.	DESCRIPTION OF WASTEWATER – Municipal/ Domestic Wastewater

III.	DESCRIPTION OF WASTEWATER TREATMENT – Wastewater is collected and treated by means of a n activated sludge followed by UV disinfection.  No increase in flow is proposed within the application.   

IV.	RECEIVING WATERS – Phyfer Creek thence to South Tippah Creek (Discharge Location, Topography Map, Attachment # 2).  The receiving waters are located within the Yazoo River Basin, and are classified as Fish and Wildlife.  Neither waterbody appears on the updated State of Mississippi 303(d) list of impaired waterbodies, or a completed TMDL. At the point of discharge the 7Q10 for the receiving stream is 0.0 cfs.  The instream wastewater concentration at the point of discharge IWC is 100% and is calculated as follows:

IWC = {(Qw)/(Qw + Qr)}*100

	Where, Qw = Design flow of the wastewater treatment facility, 2.0 MGD or 3.10 cfs
		 Qr = Receiving stream 7Q10, 0.00 cfs.

IWC = {(3.10 cfs)/(3.10 cfs + 0.00 cfs)}*100 =100 %

V.	APPLICABLE GUIDELINES –– 11 Mississippi Admin Code pt. 6 (Admin. Code), Wasteload Allocation (WLA, Attachment # 3), and Municipal Facility Guidelines (Technology)

VI.	SUMMARY OF LIMITATIONS –
Parameter				Flow				Basis
Flow 					2.0 MGD			Design
BOD5 					18 mg/l 			WLA			
BOD % Removal 			85% Minimum		Technology
Minimum DO				6 mg/l				WLA
TSS 					30 mg/l 			Technology
TSS % Removal 			85% Minimum		Technology
Copper, Total Recoverable		0.005 mg/l			Attach #7
E. Coli	 				126 Col./100 ml		WLA
	Ammonia Nitrogen Phase I 		2.5 mg/l 			WLA
	Ammonia Nitrogen Phase II		1.37 mg/l			WLA
	Nitrogen, Total 			Report, lbs./ day		WLA
	Phosphorus, Total 			Report, lbs./ day		WLA	
pH 				6.0 – 9.0 SU			WLA
Chlorine 			0.011 mg/L			WLA

The minimum and maximum values for Dissolved Oxygen in aeration unit, and 30-Minute Sludge Settleability in aeration unit must be reported.

VII.	CHANGES FROM PREVIOUS PERMIT –

2023 Waste Load Allocation has established a new ammonia limit based on ammonia toxicity. The new ammonia limit has been added onto the draft permit to reflect WLA. . Copper limitations have been added to the proposed draft permit based on facility’s potential to impact water quality for that parameter.

“Backup Disinfection” permit condition has been added to the propose draft permit and states as follows:
	
Chlorination may be utilized by facility in the event the ultraviolet (UV) system is not available for disinfection. When chlorine is used as the method for disinfection, the facility must comply with the Chlorine, Total Residual limitations provided in the permit.  If chlorination is not being utilized, the permittee shall report NODI_CODE 9 (Conditional Monitoring - Not Required This Period) in the quarterly Discharge Monitoring Report (DMR)

“Phase Conditions” have been added to the permit, thus stating the below:

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. 

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 engineering report: Due once within 6 months (180 days) after effective date. Said report shall outline the improvement activities needed to upgrade the wastewater treatment facility to comply with the site's Phase II limitations and shall include a proposed schedule for those improvement activities.

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.

BIOASSAY AND CHEMICAL SPECIFIC EVALUTION

BIOASSAY

	In accordance to State Regulation 11 Mississippi Admin Code, pt. 6, VI.B.2b., Ripley 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 are to be performed on Ceriodaphnia dubia (vertebrates) and Pimephales promelas (invertebrates). Lab data sheets reported the following results of the four (4) bioessays submitted:

April 2022
Ceriodaphnia dubia									IC23 >100%
Pimephales promelas									IC23 >100%

May 2022
Ceriodaphnia dubia									IC23 >100%
Pimephales promelas									IC23 >100%

September 2022
Ceriodaphnia dubia									IC23 >100%
Pimephales promelas									IC23 >100%

December 2022
Ceriodaphnia dubia									IC23 >100%
Pimephales promelas									IC23 >100%

Chemical Specific Analysis

	Major 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). For this reissuance, The facility have submitted a full sample set of 12  required and was shown to have a reasonable potential of concern for Copper (Attachment #^6)

Acid Extractables, Base-Neutrals, and Volatiles

Majors shall also perform monitoring of and submit results for all compounds denoted under the heading of Volatile Organic Compounds, Acid-Extraction Compound, and Base-Neural Compounds. Limitations shall be placed in the permit if results indicate a potential for violation.
Lab results indicate none detects for Acid Extractable Compounds, Base-Neutral Compounds, and Volatile Organic Compounds.

ATTACHMENTS

	Attachment # 1 – Flow Diagram 
	Attachment # 2 – Discharge Location Topography Map 
            Attachment # 3 – Wasteload Allocation
	Attachment # 4 – Chemical Specific Analysis
	Attachment # 5 – MS Water Quality Numerical Criterion
	Attachment # 6 – Toxicity Screen
	Attachment # 7 – Copper Limitation Calculation

Attachment # 1- Flow Diagram

Attachment # 2- Discharge Location Topography Map

Attachment # 3- Wasteload Allocation 

Attachment # 4 – Chemical Specific Analysis

Attachment # 5 – MSWQ Numerical Criterion (11 Mississippi Admin Code pt. 6 Ch.2)

Attachment # 6

Attachment # 7 – Copper Calculations

Calculation of Copper Acute Limit 

CuC = CA / IWC 
Where: 

CuA =Acute Copper limit to be placed in proposed draft permit 

CA= Acute Allowable Criteria for Copper in fresh water (0.007 mg/l) 

IWC= Chronic Instream Waste Concentration (100%) 

CuA = (0.007 mg/l) / (1.00) = 0.007 mg/l 

Calculation of Copper Chronic Limit 

CuC = CuC / IWC 
Where: 

CuA =Chronic Copper limit to be placed in proposed draft permit 

CA= Chronic Allowable Criteria for Copper (0.005 mg/l) 

IWC= Chronic Instream Waste Concentration (20.62%) 

CuA = (0.005 mg/l) / (1.00) = 0.005 mg/l