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HANDLING HIGH STRENGTH LIQUIDS
Waste Management's new Anaerobic Pretreatment Center receives liquid waste streams with high COD and fats, oils and grease.
THE CID Recycling and Disposal Facility, operated by Waste Management, Inc., is located at its closed MSW landfill in Calumet City, Illinois, about 20 miles from Chicago. Waste Management is creating an environmental complex that houses a single stream materials recovery facility (MRF), a soil remediation operation, a biological liquid treatment center using the sequencing batch reactor (SBR) technology, and landfill gas recovery with a power generation station. The most recent addition to the CID facility is an anaerobic digester - the Anaerobic Pretreatment Center (APC) - that began operating in late spring. Methane gas produced by the digester is fed into the same landfill gas recovery line that feeds two CAT reciprocating gas engine generators. Enough electricity is created to power 8,000 homes.
The APC is designed to process high strength liquid waste streams, primarily from commercial and industrial customers. It is permitted to accept wastewaters and offspec material from the food, dairy, beverage, pharmaceutical and personal care industries; grease trap wastes from the food, dairy, beverage and personal care industries; portable sanitation wastes; and septage.
The digester was designed by a consultant to Waste Management, and built using commercially available pumps, a tank and related components. It has a working volume of 1.5 million gallons. "The digester can handle a wide range of liquid residual streams," says William Schubert, Director of Environmental Engineering for Waste Management's Midwest Group. "If we can pump it and it is organic, it is acceptable to this technology. Then it becomes an issue of residence time."
Jean LaPlanche, Manager of the APC, adds that the digester has 60,000 mg/L/day (50,000 Ibs/day) of chemical oxygen demand (COD) capacity in its original design. "As long as the mixture isn't over that COD level, our standard operating procedures and residence time will be fine. If it is more than that, we need to increase the residence time." In general, waste streams with the following characteristics can be handled: Low to...