Site Visit Story—Avoid a Big SAC

Story: Metal Treaters, Inc., of St. Paul, a commercial heat treater that processes a variety of metal parts, added a new line with water intensive cleaning tanks that increased water use by 4.5 million gallons a year. Following a review by the public wastewater treatment facility, the company learned it would need to purchase 66 more Service Availability Charge (SAC) units—at a one-time cost of nearly $75,900—unless it reduced water use.

Ed Barcikowski, metallurgist, called MnTAP for assistance. Randy Cook and Karl DeWahl, MnTAP engineers, visited Metal Treaters to help identify opportunities to reduce water use, including filtration technology and an automatic system to maintain water levels in rinse tanks.

Results: Working with an outside vendor, Metal Treaters designed a portable wastewater filter system to remove contaminants, allowing the number of batch discharges to be reduced. Drag-out reduction techniques extended the life of cleaning tanks and reduced demand for cleaning chemicals. The company also installed automatic filling systems with timers to maintain water levels in rinse tanks. Metal Treaters decreased water use by 90 percent, reducing its SAC to six units, saving $66,000. Additional savings resulted from lower water and chemical use.

Prevention Tips: Drag-out reduction techniques such as allowing for drip time and using air blow-off and rinse aids will reduce carry over. Add fresh water in the form of fog or mist to rinse off carry over. Cover heated tanks between use to reduce evaporation. Use conductivity sensors to measure contaminant levels and use an automatic filling system with timers to control water flow to the tanks.

Request a visit from a MnTAP engineer or scientist to get suggestions customized to your operation, call 612/624-1300.