Primary Digester Rehabilitation
Client
Union Sanitary District (USD)
Location
Union City, CA
Union Sanitary District operates six anaerobic digesters with a combined total volume of 5.3 million gallons. All six digesters are typically in operation, but one is taken out of service every eight years for routine cleaning. Each digester has a dedicated heating and mixing system to support a mesophilic digest process which allows them to run independent from each other. This project includes the rehabilitation of Primary Digester No. 2 as well as additional improvements to the plant and pump station operations.
Updates to the digester includes structural and coating repairs, replacement of foam insulation cover and guardrails, repairs to the overflow box, modification to gas piping, and replacement of the overflow box piping, heat exchanger, recirculation pump, and 18-inch diameter valves on the digester sludge lines.
Additional rehabilitation items located in other areas of the plant include: deck modifications and replacement of waterlines for two thickeners; coating and structural repair of the mechanisms and walkways of two primary clarifiers; replacement of the effluent screen bearings and repair on the secondary effluent pipeline of the chlorine contact tanks; repairs to concrete beam at the building of four primary clarifiers; and repairs to the exterior wall and overflow box of a secondary digester.
