Kiel is a town of 3,500 people located on the banks of the Sheboygen river in Wisconsin, 70 miles north of Milwaukee. The town is also a major cheese processing hub.
The Kiel wastewater treatment plant (WWTP) is an activated sludge plant that uses a coarse bar screen, aerated grit removal, and a fine screen followed by two primary clarifiers. Following the clarifiers is aeration, secondary clarifiers, sand filters, chlorine contact and post aeration. The clarifier solids go to anaerobic digesters and the methane is flared off.
The plant treats high strength wastewater from cheese production operations. The cheese waste is received by truck, stored at the facility in bulk, and then dosed into the plant’s residential wastewater influent stream during low flows.
The Dissolved Oxygen (DO) is closely monitored during this time; in the event that the DO drops to unacceptable levels, the cheese waste influent is turned down or shut off.
A week-long pilot trial of a Hydro-Industrial MicroScreen was conducted to explore alternative methods of treating the cheese waste.
A submersible pump was placed in the splitter box that feeds the two primary clarifiers. The effluent from the Hydro-Industrial MicroScreen flowed by gravity into aeration.
On the first day the solids were compressed, and passed the paint filter test - making them acceptable to transport direct to landfill. For the following four days the solids were not compacted but pumped to digestion at 2-3% solids.
The Hydro-Industrial Microscreen reduced total suspended solids (TSS) by 13% and biochemical oxygen demand (BOD) by 16%, exceeding the performance of the existing primary clarifier.
As a result of the pilot study, it was determined that the Hydro-Industrial MicroScreen would:
• Allow the plant to process 5x more cheese waste • Allow the plant to accept waste from septage haulers • Increase heat recovered in anaerobic digestion • Increase plant loading capacity for TSS and BOD • Increase hydraulic loading capacity of activated sludge process • Reduce sludge production and disposal costs
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