PERMIT RATIONALE FOR REISSUANCE
Waynesboro POTW
Wayne County
Waynesboro, Mississippi
Water NPDES No. MS0024228
November 2022

I.	CLASSIFICATION – NPDES Major Municipal

II.	DESCRIPTION OF WASTEWATER – Domestic/Municipal Wastewater

III.	DESCRIPTION OF WASTEWATER TREATMENT – Municipal wastewater is collected and treated biologically by means of an activated sludge plant/oxidation ditch followed by chlorine disinfection prior to discharge.  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 – Patton Creek thence into Chickasawhay River.  The receiving waters are located within the Pascagoula River Basin and are 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 2022 State of Mississippi 303(d) list of evaluated or impaired waterbodies.  The discharge does not appear on a completed Total Maximum Daily Load (TMDL).

The 7-day, 10-year minimum flow (7Q10) of the receiving stream is 1.21 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, 2.25 MGD or 3.48 cfs.
	QR = Receiving stream 7Q10, 1.21 cfs.

IWC = {(3.48 cfs)/(3.48 cfs + 1.21 cfs)}*100 = 74.2 %

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

VI.	CHANGES FROM PREVIOUS PERMIT – 

Ammonia Nitrogen limits of 1.8 mg/l have been added to the draft permit based on the State of Mississippi Water Quality Standards for Ammonia toxicity and adjusted for the facility’s IWC. The limit will be phased in on a 3-year schedule. 

VII.	SUMMARY OF LIMITATIONS –
	Parameter				Value				Basis
	Flow					2.25 MGD			Design
	BOD5 					20 mg/l 			WLA
	TSS					30 mg/l 			Technology
	Ammonia Nitrogen			
-	Phase I				2.0 mg/l			Previous Permit
-	Phase II			1.8 mg/l			WLA, MSWQS
	Dissolved Oxygen 						> 6.0 mg/l 			WLA
	E. coli								126 col./100 ml		MSWQS
	Chlorine, Total Residual				0.015 mg/l 			WLA, MSWQS
	pH								6.0 – 9.0 SU			MSWQS
	Total Nitrogen							Report lbs/day			WLA		
	Total Phosphorus						Report lbs/day			WLA
	Copper, Total Recoverable				0.00667 mg/l			Application Data
	
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.

BIOASSAY AND CHECMICAL SPECIFIC EVALUATIONS

BIOASSAY

In accordance to State Regulation 11 Mississippi Admin Code pt. 6, VI.B.2b., Waynesboro 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).  The results of the wet tests are as follows:

March 2022
		Ceriodaphnia dubia		IC25 		>100%
		Pimephales promelas		IC25		>100%

		June 2022
		Ceriodaphnia dubia		IC25 		>100%
		Pimephales promelas		IC25		>100%

September 2022
		Ceriodaphnia dubia		IC25    	 	>100%
		Pimephales promelas		IC25		>100%

		October 2022
		Ceriodaphnia dubia		IC25 		>100%
		Pimephales promelas		IC25		>100%

All of the inhibition concentrations were greater that the predicted IWC of 74.2%. Based on the results of the WET testing, chronic bioassay requirements will not be placed in the permit.

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 Waynesboro POTW, the chemical specific data results submitted with the reapplication indicated the reasonable potential for violation of the appropriate criteria (Copper - acute, chronic) in Table III of Appendix D of CFR 122. See Attachment No. 6 for Chemical Specific Screening sheet and results, and Attachment No. 7 for a calculation of the Copper limit included in the draft permit.

Waynesboro POTW failed to submit influent and effluent samples for the following parameters: Nickel. As a condition of the draft permit, Waynesboro POTW will be required to begin the chemical specific monitoring within 10 days of the date of permit issuance and complete the required testing within one year following the effective date of the permit for the parameters listed above. Upon receipt of the above data, pending the results, the permit will be reopened to make any modifications needed.  

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

For Volatile Organic Compounds, the permittee had an average daily concentration for the following compounds: 

		Dibromochloromethane - Average Daily Concentration: 0.38 µg/L		

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

		Dibromochloromethane - Human Health Criteria: 21 µg/L
	
Multiplying the average daily concentrations 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.

		Dibromochloromethane - [0.38 µg/L*10] = 3.8 µg/L < 21 µg/L

The above results demonstrate that the average concentrations for Dibromochloromethane do not present a reasonable potential to violate Human Health Criteria.

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

ATTACHMENTS

Attachment No. 1 – Flow Diagram
Attachment No. 2 – Discharge Location Map
Attachment No. 3 – Wasteload Allocation
Attachment No. 4 – Chemical Specific Tabulated Results
Attachment No. 5 – MS State Water Quality Standards
Attachment No. 6 – Chemical Specific Screening
Attachment No. 7 – Calculation of Copper Limit

Attachment No. 1 – Flow Diagram

	

Attachment No. 2 – Discharge Location Map

Attachment No. 3 – Wasteload Allocation

Attachment No. 4 - Chemical Specific Tabulated Results

Attachment No. 5 - MS State Water Quality Standards

Attachment No. 5 - MS State Water Quality Standards (cont.)

Attachment No. 6 – Chemical Specific Screening

Attachment No. 7 – Calculation of Copper Limit