PERMIT RATIONALE FOR REISSUANCE
New Albany POTW
Union County
New Albany,, Mississippi
Water NPDES No. MS0062651
Date
I.	CLASSIFICATION – Municipal NPDES Major

II.	DESCRIPTION OF WASTEWATER – Municipal Wastewater

III.	DESCRIPTION OF WASTEWATER TREATMENT – The City of New Albany is constructing a new oxidation ditch followed by UV disinfection with an average design capacity of 4.0 MGD. Upon operation, the new plant will replace New Albany’s current wastewater treatment system. See attachment no. 1 for flow diagram.  

IV.	RECEIVING WATERS – Little Tallahatchie River.  See attachment no. 2 for discharge location map.  The receiving waters are located within the Yazoo River Basin and are classified as Fish and Wildlife.  At the point of discharge the receiving stream does appear on the current State of Mississippi 303(d) list of evaluated or biological impaired waterbodies. MDEQ’s Surface Water Division has developed a computer model, based on instream data of the Little Tallahatchie River, to address the impairment. The limitations included in the permit for nutrients and biological oxygen demand are based on the model. The proposed discharge, as permitted, will not further degrade the receiving waters.  The discharge is also listed in a Total Maximum Daily Load for Pathogens in the Little Tallahatchie River.  The proposed discharge will be disinfected by UV light prior to discharge to comply with the TMDL. At the point of discharge the receiving stream 7Q10 is 2.032 cfs.  The instream wastewater concentration is determined by the following calculation:

IWC = {(Qw)(Qw + QR)}*100

	Where:
	Qw = Design flow of the wastewater treatment facility 4.0 MGD or	6.19 cfs
	QR = Receiving stream 7Q10, 2.032 cfs

IWC = {(6.19 cfs)/(6.19 cfs + 2.032 cfs)}*100 = 75.29 %

	Only one discharge to surface waters is described within the application. 

V.	APPLICABLE GUIDELINES – State of Mississippi Water Quality Criteria & “Wastewater Regulations for National Pollutant Discharge Elimination System Permits, Underground Injection Control Permits, State Permits, Water Quality Based Effluent Limitations, Water Quality Criteria (MSWQC), Water Quality Certifications”

VI.	SUMMARY OF LIMITATIONS –
	
	Parameters			Value				Basis
	Flow				4.0 MGD			Design
	BOD5				7 mg/l (Monthly Avg.)	Modeled
	TSS				30 mg/l (Monthly Avg.)	Technology
	Ammonia Nitrogen		2 mg/l (Monthly Avg.)	MSWQS
	Dissolved Oxygen		> 6.0 mg/l 			MSWQS
	E. Coli				126 Col./100 ml		MSWQS
	Nitrogen, Total 		357.424 lbs/day		MSWQS
	Phosphorus, Total		94.086 lbs/day			MSWQS
	pH				6.0 – 9.0 SU			MSWQS
	
The minimum and maximum values for dissolved oxygen and 30 – minute sludge settleability in the aeration unit must be reported.
	
	Note: MSWQS – Mississippi State Water Quality Standards		

	See modeling data results attachment no. 3.
	
BOD5, NH3-N and DO limits are based on the wasteload allocation and modeled for oxygen depletion in the receiving stream.  The toxicity limit for NH3-N was determined for the parameters that are potentially acute and chronic toxicity.  The more stringent of the modeled limit and the toxicity limit (for NH3-N) is what is given in the wasteload allocation, to meet water quality based effluent limitations (WQBELs).

An anti-degradation was done and submitted to our office for the expansion. MDEQ reviewed the anti-degradation and approved the expansion for the facility to discharge to the same receiving stream.   

BIOASSAY AND CHEMICAL SPECIFIC EVALUATION

BIOASSAY

	The permit includes limitations requiring the facility to perform the testing required in order to perform the Whole Effluent Toxicity Testing, which will meet the requirements of the Form 2A application.   The applicant shall 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 are to be performed on Ceriodaphnia dubia (invertebrates) and Pimephales promelas (vertebrates).  Monitoring shall be required once per quarter for a period of one year.  Monitoring shall begin within 90 days after the facility has been in operation for a period of one year.  The chronic toxicity value is equivalent to the facilities instream waste concentration (IWC) which is 75.29%.  Should any of the analysis demonstrate amounts that violate water quality standards a reopener clause has been included in permit.

CHEMICAL SPECIFIC ANALYSIS

	The permit includes limitations requiring the facility to perform the testing required in order to perform the chemical specific analysis screening, which will meet the requirements of the Form 2A application.  Monitoring shall be conducted twice per month for a six month period for total recoverable metals, free cyanide, phenol, pentachlorophenol, and hardness.  Sampling is to be conducted on the influent to and effluent form the treatment works. Additionally, monitoring shall be required for all other pollutants listed in Table C of the 2A application.  Sampling for these pollutants shall be performed once per month for a three month period.  Sampling is to be conducted on the effluent only.  Monitoring shall begin within 90 days after the facility has been in operation for a period of one year.  Should any of the analysis demonstrate amounts that violate water quality standards a reopener clause has been included in permit.

Attachments

Attachment No. 1 – See application
Attachment No. 2 – See application
Attachment No. 3 – Wasteload Allocation (WLA)
Attachment No. 4 – MS state water quality criteria

Attachment 3 – Wasteload Allocation

Attachment 4