Dissolved Air Flotation Treatment Ideal for Removing FOG
In 1998, a major food service company in Wisconsin learned its wastewater discharge contained high concentrations of fats, oils and grease (FOG). This posed a serious threat, both to the environment and its bottom line.
The local sewerage district had the authority to retroactively fine the company up to $10,000 for each violation day for exceeding acceptable limits, but chose not to assess the company for non-compliance discharges if it agreed to address the problem.
“Pre-treatment was needed to process the plant’s 732,350 gallons per day of outfall so that the level of FOG was consistently less than the 300mg/l limit,” explains Matt Gage, operations director at MSB Corp. “The company contracted with MSB for expert engineering and the proper equipment to get the situation resolved.”
MSB determined that an ordinary sedimentation process would have been too large for the space available and probably not as effective. Dissolved air flotation (DAF) would be an suitable treatment alternative to remove the FOG.
A pretreatment system was implemented, which consisted of an 8,000 gallon equalization pit of two Rotostrainer screens for large solids removal. The solids drop into 1,500 lb. tote containers for daily removal by a third-party renderer. The filtrate water flows to two DAF systems for clarification and the DAF float is pumped into a 11,200 gallon storage tank for pump out removal, also contracted by a third party renderer. The clean water is then discharged to the sewerage district’s publically owned treatment works (POTW).
Studies on the MSB Dissolved Air Flotation showed a reduction of FOG in the waste stream up to 92.3%, consistently beneath the sewerage district’s 300mg/l limit.
To view full article, click here.