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3 EXISTING WASTEWATER FACILmES <br /> <br />Effluent Disposal <br />Current effluent disposal practices consist of discharging plant effluent L~to the Willamette <br />River. The WPCF has historically met all regulatory requirements for secondary effluent <br />disposal with one exception. On May 17, 1991 the dally mass lflxfit was exceeded for TSS and <br />BOD. Effluent is preferentially d~sposed of through a submerged dffkzser h~ the Willamette <br />River. The NPDES perm/t requires the use of the submerged dfffi, zser from May 22 through <br />October 31. Peak wet weather flows over 103 mgd consist of blended primary and <br />secondary disinfected effluent. The wet weather hydraulic capacity of the WPCF is <br />estimated at 175 mgd, although higher flow rates approaching 215 mgd have been achieved. <br />The current prac~ce for discharging peak wet weather flows in excess of the submerged <br />diffuser ouffall capacity is to overflow into a bankside outfalL These overflows occur at a <br />weir located at the ouffall control structure. The current NPDES peru-fit allows the bankside <br />ouffall to be used from November 1 through May 21 to accormmodate peak wet weather <br />flows. <br /> <br />Thickening <br />WAS is currently thickened at the WPCF with the use of GBTs. The GBT facility houses <br />3-meter gravity belts, a polymer distribution system, and the thickened WAS pumps. WAS <br />flows either by gravity or pumped flow from the RAS control structure to the GBT facility, <br />The WAS flow rate is metered and controlled with flow control valves at the PAS and/or <br />GBT control structure. Prior to tbJckening, the WAS is conditioned with a cationic polymer. <br />Thickened WAS is bfpically around 5 percent solids and is pumped directly to the digester <br />for anaerobic digest/on. Table 3.2.2-5 summarizes the waste activated sludge unit process <br />and associated equipment. <br /> <br />TABLE 3.2.2-5 <br /> WPCF Waste Activated Sludge Thickening Unit Processes and Equipment <br /> MWMC Facilities P~an, Eugene-Springfield <br /> <br /> Capacity, (each/t~ta~ <br /> Equipment Type Quantity fi~ma/tota~~) <br /> <br /> Gravity Belt Thickeners 3-meter, 95% solids capture, 5% so/ids, 2 45,250148,250/96,500 lb/day <br /> MWWW SLR= 2010 lb/hr, MWWW HLR = <br /> 120 gpm/m <br /> <br /> WAS feed pumps Screw centrifugal with adjustable frequency 2 800/800/1,600 gpm <br /> dr'rye (AFD), 15 hp <br /> <br /> Thickened Waste P regressive cawty w~th AFD, 20 hp. 2 120/120/240 gpm <br /> Achvated Sludge Pumps <br /> <br /> Polymer System Liquid tote polymer system, 17 lb/ton 2 17/17/34 lb/ton <br /> capacity <br /> <br /> Notes: <br /> a Total firm capacity is with largest unit out of service. <br /> bTotal capacity is with all un~ts in service. <br /> <br /> Anaerobic Digestion <br /> Three primary anaerobic digesters located at the WPCF stabilgze primary, sludge and <br /> secondary WAS. Each digester is 85 £eet/n diameter and contains a fixed cover. Table 3.2,2-6 <br /> summarizes the anaerobic digestion unit processes and associated equipment. <br /> <br /> MWMC_3.0_flEVH DOC <br /> <br /> <br />