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3~ EXISTING WASTEWATER FACILITIES TABLE 3.2.2-1 WPCF Pretreatment Facility Unit Processes and Equipment MWMC Facilities Plan, Eugene-Springfield Capacity, (each/total Equipment Type Quantity firma/totalb) Screenings Grinder Inline (rated at 150 cubic feet of screenings 2 1,000/1,000/2,000 gpm per hour) Grit Removal Aerated Grit Chambers (101,000 gallons 4 58.3/175/233 mgd each; design criteria of 2.5 minutes detention time at peak flow) Grit Slurry Pumps Recessed Impeller 4 300/900/1,200 gpm Preaeration Chambers (152,000 gallons each; design 4 14.6/43.8/58.4 mgd criteria of 15 minutes detention time at average flow) Screenings Impeller Washer 2 2,000/2,000/4,000 gpm Washer/Compactor Shafted Screw Conveyor and Compactor Compacted Shaftless, Dual-Drive, Reversing Screenings/Grit Grit 2 900/900/1,800 lb/hr Conveyor Screenings 2 1,400/1,400/2,800 lb/hr Solids Loadout Conveyor Shaftless Screw Grit 2 900/900/1,800 lb/hr Screenings 2 1,400/1,400/2,800 lb/hr Grit Separation Cyclones 4 300/900/1,200 gpm Classifiers 2 600/600/1,200 gpm Notes: a Total firm capacity is with largest unit out-of-service. b Total capacity is with all units in service. Primary Treatment The MWMC WPCF currently uses a total of four primary clarifiers to treat screened and degritted raw sewage. The existing primary clarifiers are circular, have outboard launders, and are 135 feet in diameter. Each clarifier receives effluent from the plant's existing headworks through a dedicated 60-inch-diameter pipe. Primary sludge is accumulated at the bottom of the clarifier and thickened through compaction. Primary sludge solids are drawn off with intermittent sludge pumping and a thin sludge blanket is maintained within the clarifier. Table 3.2.2-2 summarizes the primary treatment processes and equipment. MWMC_3.0_REV11.DOC 3-9