PERMIT RATIONALE FOR REISSUANCE
Indianola POTW
Sunflower County
Indianola, Mississippi
Water NPDES No. MS0024619
April 2018

I.	CLASSIFICATION – NPDES Major Municipal

II.	DESCRIPTION OF WASTEWATER – Domestic/Municipal Wastewater

III.	DESCRIPTION OF WASTEWATER TREATMENT – Wastewater is collected and treated via a baffled 55-acre facultative lagoon followed by chlorine disinfection, dechlorination, and post-aeration prior to discharge. See Attachment 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 WATERS – Big Sunflower River. See Attachment 2 for discharge location map. The receiving water are located within the Yazoo River Basin and are classified as Fish and Wildlife.  The receiving waters do not appear on the current State of Mississippi List of Evaluated or Impaired Waterbodies.  The discharge does appear on the Delta Large River Nutrient Total Maximum Daily Load (TMDL1, June 2008) and on the TMDL for Organic Enrichment, Nutrients and Sediment for the Big Sunflower River (TMDL2, June 2003). Total Nitrogen and Total Phosphorus limits prescribed in TMDL1 and minimum Dissolved Oxygen limits satisfying TMDL2 have been incorporated into the draft permit.

The 7-day, 10-year minimum flow (7Q10) of the receiving stream is 30 cubic feet per second (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, 2.25 MGD or 3.48 cfs
Qr = Receiving stream 7Q10, 30 cfs.

IWC = {(3.48 cfs)/(3.48 cfs + 30 cfs)} * 100 = 10.4 %

V.	APPLICABLE GUIDELINES – 11 Mississippi Admin Code Pt. 6, Wasteload Allocation (WLA), Total Maximum Daily Loads (TMDLs1,2), Municipal Facility Guidelines (Technology)

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 DISCHARGE LIMITATIONS – 
Parameter			Value				Basis
Flow				2.25 MGD			Design
BOD5				45 mg/l			WLA	
BOD5 (% Removal)		65% Minimum		Technology
TSS				90 mg/l			Technology
TSS (% Removal)		65% Minimum		Technology
Ammonia Nitrogen		Report				WLA
Dissolved Oxygen		6.0 mg/l Minimum		WLA, TMDL2
E. coli				126 col/100 ml 		Admin Code
Chlorine, Total Residual	0.106 mg/l			WLA
Total Phosphorus		97.6 lbs/day			TMDL1
Total Nitrogen			215.9 lbs/day			TMDL1
pH	 			6.0 – 9.0 S.U.			Admin Code

The facility is eligible for equivalent to secondary limits based on the satisfaction of the conditions set forth in 40 CFR part 133.101(g).

The monitoring and reporting requirements of the draft permit are consistent with State Municipal Guidelines, Section B (All Lagoons).

BIOASSAY AND CHECMICAL SPECIFIC EVALUATIONS

Bioassay

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

August 2017
		Ceriodaphnia dubia		IC25 		>100%
		Pimephales promelas		IC25		>100%

		December 2017
		Ceriodaphnia dubia		IC25 		>100%
		Pimephales promelas		IC25		>100%

Due to less than 4 WET tests being completed, as a condition of the draft permit, Indianola POTW will be required to begin the WET testing monitoring within 10 days of the date of permit issuance and complete the required testing within one year following effective date of the permit.  Indianola POTW has a water salinity of less than 1,000 mg/l, so freshwater testing organisms will be used.  Indianola POTW should use a dilution ratio of 10.4 % when performing the Whole Effluent Toxicity testing.  Regulations require that those facilities with an IWC of than or equal to 1% performs a chronic whole effluent toxicity evaluation.  This test should be performed in accordance with Short-Term Methods for Estimating the Chronic Toxicity of Effluents and Receiving Water to Freshwater Organisms (EPA/600/4-91/002) or most recent addition.  The chronic WET tests should be performed on Ceriodaphnia dubia (invertebrate) and Pimephales promelas (vertebrate).

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 4.  The reported values are then analyzed and compared to water quality criteria (see Attachment 5) to determine any possible toxic effect to the receiving waters.  A synopsis of these calculations is listed in Attachment 6.  A column by column description of the calculations in Attachment 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 Indianola 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.  

Indianola POTW submitted influent and effluent samples outside of the acceptable holding times for the following parameters: Hexavalent Chromium, Cyanide. As a condition of the draft permit, Indianola POTW will be required to begin resampling 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 compound(s): 

		Chloroform - Average Daily Concentration: 7.25 µg/L

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

		Chloroform - Human Health 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.

	Chloroform - [7.25 µg/L*10] = 72.5 µg/L < 2000 µg/L

The permittee also had an average daily concentration for the following compound:

	3 & 4 Methylphenol – Average Daily Concentration: 1.36 µg/L. 

According to the Material Safety Data Sheets (MSDS) for 3 & 4 Methylphenol, the most stringent criteria for toxicity to aquatic life is shown below: 

	3 & 4 Methylphenol – Aquatic Life Criteria: 1.4 mg/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 Aquatic Life Criteria.

	3 & 4 Methylphenol - [1.36 µg/L*10] = 13.6 µg/L < 1.4 mg/L

The above results demonstrate that the average concentrations for Chloroform and 3 & 4 Methylphenol do not present a reasonable potential to violate Water Quality Criteria.

Indianola POTW submitted influent and effluent samples outside of the acceptable temperature ranges for the following parameters: All Volatile Organic Compounds. As a condition of the draft permit, Indianola POTW will be required to begin resampling within 10 days of the date of permit issuance and complete the required testing within three months 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.

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

ATTACHMENTS

Attachment 1 – Flow Diagram
Attachment 2 – Discharge Location Map
Attachment 3 – Wasteload Allocation
Attachment 4 – Tabulated Metals Testing Data
Attachment 5 – MS State Water Quality Standards
Attachment 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

   *Denotes sample that did not pass QA/QC criteria. Resampling conditions for the affected parameters are included in the draft permit. 

Attachment No. 5 – MS State Water Quality Standards
Attachment No. 6 – Synopsis of Metals Results