PERMIT RATIONALE FOR REISSUANCE
Bruce POTW
Calhoun County
Bruce, Mississippi
Water NPDES No. MS0042129
March 2020

I.	CLASSIFICATION – Minor Municipal NPDES

II.	DESCRIPTION OF WASTEWATER – Domestic/Municipal Wastewater 

III.	DESCRIPTION OF WASTEWATER TREATMENT – Wastewater is collected and treated via an aerated lagoon, followed by chlorine disinfection. After disinfection the wastewater is dispersed through a land application/overland flow system. Overflow from the land application system is then discharged from four (4) outfalls. No increase in flow is proposed within the application. 

IV.	RECEIVING WATERS – Skuna River. At the point of discharge the receiving water does appear on the updated  State of Mississippi 303(d) List of Impaired Waterbodies for aquatic life support due to biological impairment. The facility is mentioned in a completed TMDL for Grenada Lake Watershed for Mercury. This proposed draft permit contains requirements for Mercury monitoring, which complies with the conditions of the TMDL. The receiving water is located in the Yazoo River drainage basin, and is classified as Fish & Wildlife. At the point of discharge the 7Q10 for the receiving stream is 2.48 cfs. The instream wastewater concentration of discharge can be determined by the following calculation:

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

Where, Qw = Highest flow of the wastewater treatment facility, 0.5 MGD or 0.775 cfs
		 Qr = Receiving stream 7Q10, 2.48 cfs.

IWC = {(0.775 cfs)/(0.775 cfs + 2.48 cfs)}*100 = 23.8%

V.	APPLICABLE GUIDELINES – 11 MS Admin Code pt. 6,  Wasteload Allocation (WLA), Municipal Facility Guidelines, Whole Effluent Toxicity Evaluation (WET) Test Results

VI.	SUMMARY OF DISCHARGE LIMITATIONS – 
For Outfall 001, 002, 003, 004

Parameter		Value					Basis
Flow			Report					Design
BOD					
•	May-Oct	15 mg/l (Monthly Average) 		WLA	
•	Nov-Apr	30 mg/l (Monthly Average)		WLA
•	Influent		Report					Municipal Guidelines
•	% Removal	85%  Minimum				Municipal Guidelines
TSS			
•	Jan-Dec		30 mg/l	(Monthly Average)		Municipal Guidelines
•	Influent		Report					Municipal Guidelines
•	% Removal	85% Minimum				Municipal Guidelines
Ammonia
•	May-Oct	6 mg/l (Monthly Average)		WLA
•	Nov-Apr	10 mg/l (Monthly Average)		WLA
•	Influent		Report					Municipal Guidelines
Dissolved Oxygen	6 mg/l (Minimum)			WLA
pH			6.0 to 9.0 S.U.				Admin Code
Chlorine		0.011 mg/l				Admin Code

Combined Limitations for All Four (4) Outfalls

Parameter		Value					Basis
Flow						
•	May-Oct	0.337 MGD				Design
•	Nov-Apr	0.5 MGD				Design
BOD					
•	May-Oct	42 lbs/day (Monthly Average)		WLA	
•	Nov-Apr	125.0 lbs/day (Monthly Average)	WLA
•	Influent		Report					Municipal Guidelines
TSS			
•	May-Oct	84 lbs/day (Monthly Average)		WLA
•	Nov-Apr	125 lbs/day (Monthly Average)		WLA
•	Influent		Report					Municipal Guidelines
Ammonia
•	May-Oct	17.0 lbs/day (Monthly Average)		WLA
•	Nov-Apr	42.0 lbs/day (Monthly Average)		WLA
•	Influent		Report					Municipal Guidelines
E. Coli
•	Jan-Dec		126 Col./100 ml				Admin Code
Rainfall			Report Inches				Previous Permit
	Pimephale promelas		23.8% Minimum		Admin Code, WET
	Ceriodaphnia dubia		23.8% Minimum		Admin Code, WET
	Total Nitrogen			Report					WLA
	Total Phosphorus			Report					WLA

BIOASSAY AND CHEMICAL SPECIFIC EVALUATION

BIOASSAY

In accordance to State Regulation, 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 Pimephale promelas (vertebrate). The results of the wet tests are as follows:

March 2017
Ceriodaphnia dubia IC25 = 48.4%
Pimephales promelas IC25 = 48.4%

June 2017
Ceriodaphnia dubia IC25 =48.4%
Pimephales promelas IC25 =26.3%

August 2017
Ceriodaphnia dubia IC25 =9.71%
Pimephales promelas IC25=48.4%

October 2017
Ceriodaphnia dubia IC25 =48.4%
Pimephales promelas IC25=48.4%

Based on the results of the WET testing, inhibition concentrations were not greater that the predicted IWC of 23.8%. Chronic bioassay requirements will be placed in the permit.

CHEMICAL SPECIFIC ANALYSIS

Minor Toxic 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.  Chemical specific 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 indicated that reasonable potential for violations of the appropriate criteria (acute, chronic, and human health). 

The chemical specific data results (Attachment No. 4) submitted did not demonstrate a reasonable potential for violation of the appropriate criteria in Table III of Appendix D of CFR 122. See Attachment No. 5 for the Toxicity Screening.

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,  Acid-Extractable, and Base-Neutral Compounds.

	

Attachments

Attachment No. 1 – Wastewater treatment flow diagram – See Application
Attachment No. 2 – Discharge location map – See Application
Attachment No. 3 – Wasteload Allocation (WLA)
Attachment No. 4 – Chemical Specific Analysis
Attachment No. 3 – Toxicity Screening

Attachment 3

Attachment 4

Attachment 5