PRETREATMENT RATIONALE FOR MODIFICATION

Weyerhaeuser NR Company, Philadelphia Facility
Neshoba County
Philadelphia, MS
Water Branch II

MSP091379
SIC: 2421
January 30, 2023
Permit Engineer: Rajeev Gupta

Weyerhaeuser NR Company, Philadelphia has applied for a modification of their Pretreatment Permit No. MSP091379 for an increase in the volume of process wastewater discharge from their facility into the Philadelphia POTW.  Currently, the facility discharges 30,000 gallons per day of kiln condensate and ash bin drainage to the POTW.  As a result of the proposed addition of a third Continuous Direct Fired Kiln, the facility has applied to discharge an average flow of 50,000 gallons per day.  As part of this project, Weyerhaeuser has submitted plans and specifications for an aerated lagoon with a maximum holding capacity of 704,000 gallons.  Philadelphia Utilities has agreed to accept the increased flowrate once the aeration basin is completed.  As can be seen below, the POTW should be able to adequately treat the discharge.  In the existing permit, the facility is allowed to meet pH limits after mixing with the facility’s sewage.  This condition is being removed from the permit and the facility will be required to meet the pH limits prior to mixing with unregulated wastewater.  Two special conditions of the permit shall be as follows:  

1.  Within 180 days after the commencement of discharge from the third Continuous Direct Fired 
	Kiln, the permittee shall submit a complete a Form 2P Application to Mississippi 	Environmental Quality Permit Board.

2.	The permittee shall notify MDEQ within fifteen (15) days after the commencement of discharge 		from the third Continuous Direct Fired Kiln.

The existing permit contains only limitations for pH.  No other modifications to the existing permit are being proposed than those above.  A public notice will be required for this permitting action.

 

ADEQUACY OF TREATMENT

	Date:  January 30, 2023                  
Permit Writer:  Rajeev Gupta
Proposed Site:  Weyerhaeuser NR Company, Philadelphia Facility          
Pretreatment Permit No. MSP091379 
Neshoba County  
Proposed Hydraulic Loading:  0.050 MGD 
Proposed Organic Loading:  300 mg/L (The facility is planning to add secondary treatment to reduce BOD5 concentration of wastestream to domestic sewage levels)
0.050 MGD*8.34*300 mg/L = 125.1 lb/day 

Philadelphia POTW, NPDES Permit No. MS0021156, AI No. 13336   
Permitted Flow:	3.2 cfs = 2.1 MGD.  The effluent shall not be discharge to the receiving stream when the stream flow is less than 16 cfs. A dilution ratio of 5 to 1 (steam flow to discharge) shall be maintained until such time as the stream flow is equal to or greater than 44 cfs.  
12 Months Flow:	1.229 Monthly avg. value (from January – December 2022 DMRs)
12 Months BOD5: 	300 mg/L representative influent value 
Design BOD5:	2.1 MGD*8.34*300 mg/L = 5254 lb/day  
Potential Max. BOD5:  1.229 MGD*8.34*300 mg/L = 3075 lb/day

Evaluation of Flow
2.1 MGD permitted – 1.229 MGD actual = 0.871 MGD 
0.871 MGD available vs. 0.020 MGD increase proposed

Evaluation of BOD5
5254 lb/day available – 3075 lb/day potential max. = 2179 lb/day
2179 lb/day available vs. 125.1 lb/day proposed