Modifying One of the Nation's Most Successful Biosolids Lime Stabilization Operations

by Randy Naef, CH2M Hill, Portland, United States,
Ronald J. Matheson, CH2M Hill, Portland, United States,
Mike Guthrie, CH2M Hill, Portland, United States,
Tracy Cork, CH2M Hill, Portland, United States,

Document Type: Proceeding Paper

Part of: Critical Issues in Water and Wastewater Treatment


Since 1978, the Vallejo, California, Sanitation and Flood Control District has managed a tremendously successful biosolids program consisting of lime stabilization and agricultural land application. In-plant biosolids processing consists of lime stabilization of sludges in conjunction with gravity thickening, followed by vacuum filtration dewatering. These processes evolved primarily from facilities from the plant's original physical/chemical wastewater treatment process configuration, as subsequently modified to conventional secondary treatment. Facilitating land application was the District's farsighted purchase in 1983 of a remote 1,850-acre land application site. The plant biosolids processing facilities are nearing the end of their useful life and have inadequate redundancy. In 1992, the District undertook an evaluation of its solids facilities to identify necessary modifications. Evaluations included methods of lime stabilization, thickening, and dewatering. An extensive pilot-plant testing program was performed to confirm and refine criteria used in the analysis of process alternatives and to quantify secondary impacts (utility requirements, recycling, etc.). This paper reviews the following pilot-plant results: 1) determination of lime requirements for stabilization of raw liquid sludges prior to dewatering and on dewatered raw sludges, 2) a comparison of centrifuge and belt filter press dewatering of raw and lime-stabilized sludge feedstocks, 3) evaluation of the new 14-pressure roll belt press configuration currently being marketed in the United States, and 4) dewatering recycle characteristics.

Subject Headings: Lime | Solid wastes | Sludge | Water treatment plants | Dewatering | Wastewater treatment plants | Recycling | United States | California

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