PERMIT RATIONALE FOR REISSUANCE
Pontotoc, City of, Activated Sludge Facility
Pontotoc County
Pontotoc, Mississippi
Water NPDES No. MS0058581
January 2024

I.	      CLASSIFICATION -  Municipal Major

II.	     DESCRIPTION OF WASTEWATER – Domestic/ Municipal Wastewater

III.	      DESCRIPTION OF WASTEWATER TREATMENT – Wastewater is collected and treated biologically by means of an activated sludge process followed by Ultraviolet disinfection.

IV.	     RECEIVING WATERS- Unnamed Tributary of Lyon Creek.  The receiving stream is located within the Yazoo River Basin.  Lyon Creek at the point of discharge is classified as Fish and Wildlife.  The receiving stream at the point of discharge does appear on the Updated State of Mississippi 303(d) list for Impaired Waterbodies with monitoring data for Aquatic Life Support due to Biological Impairment. The discharge does not appear on any TMDL.  One discharge to surface waters is described within the application with no increase in flow.  

At the point of discharge, the 7Q10 for the receiving stream is 0.00 cfs.  The instream wastewater concentration at the point of discharge can be determined by the following calculation:
IWC = {(Qw)/(Qw + Qr)}*100

Where, Qw = Design flow of the wastewater treatment facility, 1.5 MGD or 2.32 cfs
		 Qr = Receiving stream 7Q10, 0.08 cfs.

IWC = {(2.32 cfs)/(2.32 cfs + 0.00 cfs)}*100 = 100 %

V.	  APPLICABLE GUIDELINES – 11 Mississippi Admin Code pt. 6, Municipal Facility Guidelines (Technology), State of Mississippi Water Quality Criteria (MSWQS), Wasteload Allocation (WLA)

VI.	  	SUMMARY OF LIMITATIONS –

		Parameter			Value		 		Basis
		Flow				1.5 MGD		 	Design
		BOD5				6.0 mg/l			WLA 	
BOD5 (Percent Removal)	85% Minimum		Technology
		TSS				30 mg/l 			Technology
TSS (Percent Removal)	85% Minimum		Technology 
E. Coli				126 Col./100 ml		WLA
		Phase I NH3-N		2.0 mg/l 			Previous Permit
		Phase II NH3-N		1.37 mg/l			WLA
		Phosphorus, Total 		Report mg/l 			WLA
		Nitrogen, Total 		Report mg/l 		 	WLA
		Dissolved Oxygen		> 6.0 mg/l 			WLA	
		pH				6.0 – 9.0 SU		   	WLA
		Chlorine, Total Residual	0.011/ 0.019 mg/l		WLA
		Copper 			0.02/0.03 mg/l			WLA
		Zinc				0.298/0.298 mg/l		WLA
	
VII.	CHANGES FROM PREVIOUS PERMIT

Wase Load Allocation established a new ammonia limit based on ammonia toxicity. The new ammonia limit was added to the proposed draft permit.

Conditions added:

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 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. 

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 monthly Discharge Monitoring Report (DMR).

WHOLE EFFLEUNT TOXICITY AND CHEMICAL SPECIFIC EVALUATION

WHOLE EFFLEUNT TOXICITY EVALUATION

In accordance to State Regulation 11 MS Admin Code pt. 6, VI.B.2b., a whole effluent toxicity evaluation was performed 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 test were performed on ceriodaphnia dubia (invertebrate) and pimephales promelas (vertebrate). The facility submitted (4) bioessays and the results are thereby given:	 

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

February 2023
Ceriodaphnia dubia					IC25	>100%
Pimephales promelas				IC25	>100%

June 2023
Ceriodaphnia dubia					IC25	>100%
Pimephales promelas				IC25	>100%

August 2023
Ceriodaphnia dubia					IC25	>100%
Pimephales promelas				IC25	>100%

All of the inhibition concentrations were greater than the predicted IWC of 100%. Based upon the results of the WET testing, chronic bioassay requirements will not be placed within the permit.  

Chemical Specific Analysis

Chemical specific analysis has been performed in accordance with State Regulations WPC-1 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. 2.  The reported values are then analyzed and compared to water quality criteria (attachment No. 4) to determine any possible toxic effect to the receiving waters.  A synopsis of these calculations is listed in attachment No. 3.  A column by column description of the calculations in attachment No. 5 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 II 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).

City of Pontotoc Activated Sludge Facility submitted a full set of 12 metal samples required for reissuance.
	
The chemical specific data results submitted did indicate the reasonable potential for violation of the appropriate criteria in Table III of Appendix D of CFR 122 for acute and chronic copper, and acute zinc. Therefore, the facility will keep its copper and zinc permit limits. 
 
Chemical specific analysis for Volatile Organics Compounds, Acid-Extractable Compounds, and Base-Neutral Compounds and Results

The chemical specific data results submitted had no detects for Volatile Organics Compounds, Acid-Extractable Compounds, Base-Neutral Compounds	

Attachments
Attachment 1	See Application
Attachment 2	See Application
Attachment 3	Waste Load Application 
Attachment 4	Tabulated Metals Results 
Attachment 5	Synopsis of Metals Results 
Attachment 6 	MS State Water Quality Criteria 
Attachment 7 	Hardness/ Chemical Translator Study Results

Attachment 3

Attachment 4

Attachment 5

Attachment 6

Attachment 7