PERMIT RATIONALE FOR REISSUANCE
Lowndes County Industrial Development Authority
Lowndes County
Columbus,, Mississippi
Water NPDES No. MS0034525
10/7/2025

I.	CLASSIFICATION – Industrial NPDES

II.	DESCRIPTION OF WASTEWATER – Domestic and Process Wastewater.

III.	DESCRIPTION OF WASTEWATER TREATMENT – The Lowndes County Industrial Development Authority collects and treats process/sanitary wastewater via a mechanical treatment plant. The current design capacity of the treatment plant is 3 MGD. Outfall 001, as designated in the permit, is the internal outfall of the effluent from the treatment plant. Cooling water from Weyerhaeuser is combined with the effluent from the treatment plant. Outfall 002, as designated in the permit, is the internal outfall for cooling water from Weyerhaeuser.  The average flow of cooling water from Outfall 002 is 200,000 gallons per day. The combined wastewater is further treated by aeration and UV disinfection before discharging into the receiving waters. Outfall 003, as designated in the permit, is the final discharge into the Unnamed Tributary of Gilmer Creek. 

IV.	RECEIVING WATERS – Unnamed Tributary thence Gilmer Creek. Gilmer Creek is in the Tombigbee drainage basin and is classified as Fish and Wildlife. Gilmer Creek does appear on the current State of Mississippi 303(d) list of impaired waterbodies for biological impairment. This permit can be reopened and modified if a completed TMDL requires additional or more stringent monitoring based on the listed impairment. The permitted discharge is in the watershed included in the Tombigbee River (Aliceville Reservoir) TMDL. The limitations generated by the wasteload allocation comply with the conditions of the TMDL.

V.	APPLICABLE GUIDELINES – State of Mississippi Wastewater Regulations (11 MS admin code part 6), State of Mississippi Water Quality Criteria (11 MS admin code part 6), Wasteload Allocation (WLA), Total Maximum Daily Load (TMDL)

VI.	CHANGES FROM PRIOR PERMIT – Changed “3.2 MGD” to “report only” for Outfall #3.

VII.	SUMMARY OF DISCHARGE LIMITATIONS – 

Outfall 001
Parameter			Value					Basis
Flow			3.0 MGD			            Design
BOD			10 mg/l (Monthly Average)		WLA
Ammonia Nitrogen		2 mg/l (Monthly Average)		WLA
TSS			30 mg/l (Monthly Average)		Technology
pH			6.0-9.0 S.U. (Monthly Average)	11 MS admin code part 6
Dissolved Oxygen		> 6.0 mg/l			            11 MS admin code part 6
Nitrogen, Total		Report (Monthly Average)		WLA
Phosphorus, Total 		Report (Monthly Average)		WLA

Dissolved Oxygen in aeration unit, and 30-Minute Sludge Settleability in aeration unit must be reported

Outfall 002
Parameter		Value					Basis
Flow		Report					BPJ
Dissolved Oxygen	Report mg/L (Monthly Average)	BPJ
Temperature 		Report ºF (Monthly Average)	BPJ
pH		6.0-9.0 S.U.				11 MS admin code part 6

Outfall 003
Parameter		Value					Basis
Flow		3.2 MGD			                            Design 001 & Avg Flow 002
BOD		Report (Monthly Average)	BPJ
Ammonia Nitrogen	Report (Monthly Average)	BPJ
Dissolved Oxygen	6.0 mg/l (Monthly Average)	WLA
TSS		Report mg/l (Monthly Average)         BPJ
E Coli		126 # col / 100 ml	                            11 MS admin code part 6
pH		6.0-9.0 S.U. (Monthly Average)	11 MS admin code part 6
Nitrogen, Total	Report					BPJ
Phosphorus, Total	Report					BPJ

Outfall 001 is also required to adhere to the wasteload allocated limits in order to insure that the treatment system effluent would comply with water quality limitations, before being blended with Outfall 002. 

BOD5, NH3-N and DO limits are based on the Wasteload Allocation and modeled for oxygen depletion in the receiving stream, and the toxicity limit for NH3-N was determined for the parameters that are potentially acutely and chronically toxic. 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).

WHOLE EFFLEUNT TOXICITY AND CHEMICAL SPECIFIC EVALUATION

WHOLE EFFLEUNT TOXICITY EVALUATION

In accordance to State Regulation WPC – 1 VI.B.2b, 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 tests were performed on Ceriodaphnia dubia (invertebrate) and Pimephales promelas (vertebrate). The results of the wet tests are as follows:

July 2024
Ceriodaphnia dubia					IC25	>100%
Pimephales promelas				IC25	>100%

September 2024
Ceriodaphnia dubia					IC25	>100%
Pimephales promelas				IC25	>100%

April 2025
Ceriodaphnia dubia					IC25	>100%
Pimephales promelas				IC25	>100%

June 2025
Ceriodaphnia dubia					IC25	>100%
Pimephales promelas				IC25	>100%

All of the inhibition concentrations were greater that the predicted IWC of 100%. Based upon 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 WPC-1 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

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).
	
The chemical specific data results submitted did not indicate the 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, Acid-Extractable Compounds, Base-Neutral Compounds	

Attachments
Attachment 1	See Application
Attachment 2	See Application
Attachment 3	Waste Load Application 
Attachment 4	Tabulated Metals Results 
Attachment 5	Synopsis of Metals Results 
Attachment 6 	MS State Water Quality Criteria 
Attachment 7 	Hardness/ Chemical Translator Study Results

Attachment No. 3

Attachement No. 4

Attachement No. 5

Attachement No. 6