PERMIT RATIONALE FOR REISSUANCE
Water Valley POTW
Yalobusha County
Water Valley, Mississippi
Water NPDES No. MS0022331
March 2019

I.	CLASSIFICATION – Major Municipal

II.	DESCRIPTION OF WASTEWATER – Domestic/Municipal Wastewater

III.	DESCRIPTION OF WASTEWATER TREATMENT – Wastewater is collected and treated biologically by means of a multi-celled aerated lagoon followed by chlorine disinfection then de-chlorination prior to discharge. See Attachment No. 1 for a flow diagram. The treatment capacity of the facility is 1.4 MGD. Only one discharge to surface waters is described in the application with no increase in treated effluent flow proposed. 

IV.	RECEIVING WATERS – Otoucalofa Creek. The receiving waters are located within the Yazoo River Basin and are classified as Fish and Wildlife. See Attachment No. 2 for discharge location map. At the point of discharge, the receiving waters do not appear on the current State of Mississippi 303(d) List for Impaired Waterbodies.  The discharge does appear on a completed Total Maximum Daily Load (TMDL) for Fecal Coliform in Otoucalofa Creek (January 2003). The facility utilizes chlorine disinfection, which complies with the conditions of the TMDL. The discharge also appears on a completed TMDL for Mercury in Yocona River and Enid Reservoir (January 2003). Based on the results of the mercury monitoring required by the TMDL, the facility does have a reasonable potential to contribute to the mercury load. A mercury minimization plan was developed as part of a previous permitting action, which complies with the conditions of the TMDL. 

The 7-day, 10-year minimum flow (7Q10) of the receiving stream is 5.3 cfs. The Instream Wastewater Concentration (IWC) at the point of the discharge is determined by the following calculation:
IWC = {(Qw)/(Qw + Qr)}*100

Qw = Design flow of the wastewater treatment facility, 1.4 MGD or 2.17 cfs
Qr = Receiving stream 7Q10, 5.3 cfs.

IWC = {(2.17 cfs)/(2.17 cfs + 5.3 cfs)} * 100 = 29 %

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

VI.	CHANGES FROM PREVIOUS PERMIT – 

E. coli has replaced fecal coliform as the bacterial indicator for all freshwaters in MS designated as Recreation, Fish and Wildlife Support, and/or Public Water supply. 

VII.	SUMMARY OF LIMITATIONS –

Parameters				Value		Basis
Flow					1.4 MGD		Design
BOD5 					26 mg/l		WLA
BOD5 (Percent Removal)		65% Minimum		Technology
TSS					90 mg/l		Technology
TSS (Percent Removal)		65% Minimum		Technology
Ammonia Nitrogen			4 mg/l 		WLA
E. coli					126 Col./100 ml		Admin Code
Dissolved Oxygen			6.0 mg/l (Minimum)	WLA
pH 					6.0 – 9.0 S.U.		Admin Code
Nitrogen, Total			Report lbs/day		WLA
Phosphorus, Total			Report lbs/day		WLA
	Oil and Grease					10 mg/l		Previous Permit

In accordance with 40 CFR Part 133.101(g), the facility is eligible for equivalent to secondary standards, and BOD5 and TSS percent removal rates of  > 65% have been applied based on the following:

1.	The principal wastewater treatment process is a waste stabilization pond.

2.	The BOD5 and TSS concentrations consistently achievable with proper operation and maintenance exceed secondary treatment requirements. 

3.	The facility consistently provides significant biological treatment of wastewater (BOD5 removal >65%).

Further, DMR data indicates the facility cannot consistently achieve equivalent to secondary standards of 45/65 mg/l for TSS through proper operation and maintenance. Therefore, Alternative State Requirements for TSS of 90/135 mg/l have been applied in accordance with 40 CFR Part 133.103(c). 

After a stream study is completed for the site, the permit may be reopened based on Condition T-60(1) if the results of the study indicate the need for more stringent or additional permit limits to protect water quality.

BIOASSAY AND CHECMICAL SPECIFIC EVALUATIONS

BIOASSAY

In accordance to State Regulation 11 Mississippi Admin Code pt. 6, VI.B.2b., Water Valley 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:

September 2016
		Ceriodaphnia dubia		IC25 		>100%
		Pimephales promelas		IC25		>100%

		December 2016
		Ceriodaphnia dubia		IC25 		>100%
		Pimephales promelas		IC25		>100%

		February 2017
		Ceriodaphnia dubia		IC25      	>100%
		Pimephales promelas		IC25		57.03%

April 2017
		Ceriodaphnia dubia		IC25 		>100%
		Pimephales promelas		IC25		 62.4%

All of the inhibition concentrations were greater that the predicted IWC of 29 %. Based on 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 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 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).
	
For Water Valley POTW, the chemical specific data results submitted with the reapplication did not indicate the reasonable potential for violation of the appropriate criteria in Table III of Appendix D of CFR 122.  See Attachment No. 6 for Chemical Specific Screening sheet and results.  Therefore, chemical specific limits have not been placed in the permit.  

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

The chemical specific data results submitted had no detects for all Volatile Organic Compounds, 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 – 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

Plant Location

Outfall 001

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