At the 60-mgd Metropolitan Wastewater Treatment Plant (Metro WWTP), the City currently thickens a blend of primary sludge (PS) and waste activated sludge (WAS) at two separate facilities using dissolved air floatation thickeners (DAFTs) from each of their liquid process trains (Train #1 and Train #2). The existing DAFTs have reached their useful service life and are experiencing poor capture efficiencies, resulting in solids recycling. To provide reliable solids thickening and processing capacity, the City is planning to construct a new sludge thickening facility, associated sludge storage, and screening as part of the Columbia Metro WWTP Thickening Improvements Project. The proposed Thickening Improvements Project at the City’s Metro WWTP consists of the following new structures and components: New reinforced concrete, multiple-story, non-enclosed structure to house mechanical sludge thickening equipment to thicken a blend of primary sludge (PS) and waste activated sludge (WAS). The top floor contains gravity belt thickeners (GBTs) housed under a structural canopy. The bottom floor contains the GBT feed pumps and an enclosed room with polymer storage tanks, polymer mix pump, polymer preparation systems, and non-potable water booster pumps. New rectangular, reinforced concrete, closed top, PS storage tank. The structure has a divided wet well, each with a dedicated mixer. New reinforced concrete, multiple-story, non-enclosed structure to house mechanical screening equipment to screen PS. The top floor contains PS screens housed under a structural canopy. The bottom floor contains PS screen feed pumps and a 20 CY dumpster area to capture the PS screenings. New rectangular, reinforced concrete, open top, blended sludge storage tank. The structure has a divided wet well, each with a dedicated mixer. New exterior, aluminum, access stairway to interconnect the GBT structure with the PS storage tanks and screening structure, and the blended sludge storage tanks. New odor control system to capture and treat foul air from the PS storage tanks, PS screening structure, blended sludge storage tanks, and GBTs. The odor control system will be constructed on a reinforced concrete slab on-grade. New air conditioned, brick and CMU block building to house the new electrical equipment to provide power to the new structures and process equipment. New reinforced concrete electrical ductbank consisting of 1,300 LF of twelve (12), 4-inch PVC conduit with low voltage conductors. Foundation support for all new facilities will be Aggregate Piers. The Aggregate Piers will be delegated design. A geotechnical report will be supplied upon completion.
