PERMIT RATIONALE FOR REISSUANCE
Hancock County Utility Authority, S5 Kiln Northern Regional WWTP
Hancock County
Kiln, Mississippi
Water NPDES No. MS0061239
April 2019

I.	CLASSIFICATION – NPDES Municipal Major

II.	DESCRIPTION OF WASTEWATER – Municipal Domestic

III.	DESCRIPTION OF WASTEWATER TREATMENT – Wastewater is biologically treated by means of an oxidation ditch wastewater treatment facility followed by UV disinfection prior to discharge. The design capacity of the treatment facility is 1.5 MGD.

IV.	RECEIVING STREAM – Jourdan River. The receiving stream does not appear on the current State of Mississippi 303(d) List of Impaired Waterbodies nor is the discharge listed on any completed TMDLs. The receiving waters are located within the Coastal Streams Basin and are classified as Recreational.  The instream wastewater concentration at the point of discharge is determined by the following calculation:

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

Where,
QW = Design flow of the wastewater treatment facility, 2.32 cfs
Qr = Receiving stream 7Q10, 14.9 cfs.

IWC = {(2.32 cfs)/(2.32 cfs + 14.9 cfs)}*100 = 13.48%

V.	SUMMARY OF DISCHARGE LIMITATIONS – 

Parameter			Value					Basis
Flow				1.5 MGD				Design
BOD5 	(Phase I)		10.0 mg/l (Monthly Avg.)		WLA
BOD5 	(Phase II)		8.0 mg/l (Monthly Avg.)		WLA
BOD5 (Percent Removal)	85% Minimum				Technology
TSS				30.0 mg/l (Monthly Avg.)		Technology
TSS (Percent Removal)		85% Minimum				Technology
NH3-N				2.0 mg/l (Monthly Avg.)		WLA
Dissolved Oxygen		6.0 mg/l, Minimum			WLA
E. Coli				126 Col./100 ml (Monthly Avg.)		WLA
Enterrococci			35 Col./100 ml (Monthly Avg.)		MS WQS
Nitrogen, Total			Report (Monthly Avg.)			TMDL
Phosphorus, Total		Report (Monthly Avg.)			TMDL
pH				6.0 – 9.0 SU				MS WQS

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

MS WQS = Mississippi State Water Quality Standards
WLA = Wasteload Allocation dated April 8, 2019

VI.	CHANGES FROM PREVIOUS PERMIT

1.	The proposed draft permit contains Phase I and Phase II BOD5 effluent requirements.   The Phase I requirements are the same from the previous permit. The Phase II limitations reflect the limitations proposed in the Wasteload Allocation for the site dated April 8, 2019.

2.	The proposed draft permit contains updated Enterocci limitations. The limitations have been changed from 35/70 to 35/130 Monthly Average and Maximum Weekly Average, respectively, to conform with 11 MS Admin Code pt. 6, Ch. 2.

3.	Quarterly influent monitoring requirements for Nutrients (Total Nitrogen and Total Phosphorus) have been added to the draft permit.  The effluent monitoring sampling frequency has been changed from monthly to quarterly to be consistent with the influent sampling schedule. 

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 noted as Phase I; Phase II limitations shall not apply at this time
 
 Beginning upon completion and start-up of wastewater treatment units designed to meet the Phase II parameters denoted in this permit 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 noted as Phase II; Phase I limitations shall no longer be in effect at this time.  The permittee shall notify our office orally at least 48 hours prior to start-up of the wastewater treatment units designed to meet the Phase II parameters and in writing no later than 5 days after start-up

The permittee shall submit an engineering report that describes how the facility will come into compliance with the Phase II limitations.

VII.	WET TESTING EVALUATION 

Bioassay

In accordance to State Regulation 11 MS Admin Code, VI.B.2b, S5 Northern Regional WWTP 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 should be performed on Ceriodaphnia dubia (invertebrate) and Pimephales promelas (vertebrate).

July 2018
Ceriodaphnia dubia					IC25	>100%
Pimephales promelas					IC25	>100%

August 2018
Ceriodaphnia dubia					IC25	>100%
Pimephales promelas					IC25	>100%

November 2018
Ceriodaphnia dubia					IC25	>100%
Pimephales promelas					IC25	>100%

December 2018
Ceriodaphnia dubia					IC25	>100%
Pimephales promelas					IC25	>100%

All of the inhibition concentrations were greater that the predicted IWC of 13.48%. Based upon the results of the WET testing, chronic bioassay requirements will not be placed within the permit.

VIII.	CHEMICAL SPECIFIC ANALYSIS

Chemical specific analysis has been performed in accordance with State Regulations 11 MS Admin Code, 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

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).

The chemical specific data results submitted did not demonstrate a reasonable potential for violation of the appropriate criteria in Table III of Appendix D of CFR 122.

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 and Acid-Extractable Compounds.

The following Base-Neutral compound was detected and evaluated for a potential to violate Human Health Criteria:
Dimethyl Phthalate
Avg. Daily Concentration= 1.7 µg/L

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

Dimethyl Phthalate
           2,000 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.
	[1.7 ug/L * 10]= 17  µg/L
            17  µg/L < 2000  µg/L

The above results demonstrate that the average concentration(s) for do not present a reasonable potential to violate Human Health Criteria.

Attachments
Attachment 1	Waste Load Allocation
Attachment 2	Tabulated Metals Results 
Attachment 3	Synopsis of Metals Results 
Attachment 4 	MS State Water Quality Criteria
Attachment 1

Attachment 2

Attachment 3

Attachment 4