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3. EXISTING WASTEWATER FACILITIES <br /> <br />weir gates. Return sludge flows by gravity to the return activated sludge (RAS) pump <br />station. Four vertical turbine pumps lift the activated sludge to a control structure where the <br />RAS is distributed back to the aeration basins through four parallel pipes. Activated sludge <br />is then subsequently distributed to each aeration basin through a submerged diffuser <br />header. The waste activated sludge (WAS) flow rate is controlled using flow meters and <br />control valves. The WAS flows by gravity to the gravity belt thickener (GBT) and receives <br />subsequent digestion. <br /> <br />Table 3.2.2-3 summarizes the secondary treatment unit processes and equipment at the <br />WPCF. <br /> <br />TABLE 3.2.2-3 <br />WPCF Secondary Treatment Unit Processes and Equipment <br />MWMC Facilities Plan, Eugene-Springfield <br /> <br /> Capacity, (each/total <br /> Equipment Type Quantity firma/totalb) <br /> <br />Aeration Basins Complete mix or plug flow activated sludge 2 (8 cells) MMDW 24.5/43/49 MGDc <br /> cells, 135 ft x 135' x 16 ft sidewater depth, MMWW 21/63/75 mgd <br /> Volume = 2.2 MG each, Total Volume = PWWF 111 mgd <br /> 17.6 MG <br /> <br />Fine Bubble Aeration 7-inch membrane disc diffusers, 0.28 sq in 3 10,353/20,706/32,538 scfm <br /> each, diffusers, Basin I = 4017, Basin 2 = <br /> 4014, Basin 3 = 4490. <br /> <br />Coarse Bubble Coarse bubble stainless steel air diffusers, 5 15,000/60,000/75,000 scfm <br />Aeration 24-inch <br /> <br />Aeration Blowers Centrifugal multi-stage blowers, 1000 hp 6 17,000/85,000/102,000 scfm <br /> <br />Secondary Clarifiers 130-foot-diameter, 14-foot side water depth, 8 WWMM 9/66/75 mgd <br /> inboard launder, rapid sludge withdrawal DWMM 6/43/49 mgd <br /> mechanism, 44-inch influent column PWWF 111 mgd <br /> <br />RAS Pump Station Vertical Turbine Pumps - 30-inch 2 23(12)/58/70 mgd <br /> Vertical Turbine Pumps - 24-inch 2 <br /> <br />Waste Activated One 8-inch gravity wasting, with 6-inch 2 MMDW = 0.41 mgd <br />Sludge magnetic flow meter and 6-inch flow control MrvlWW = 0.44 mgd <br /> valve PWWF = 0.78 mgd <br /> <br />Secondary Scum Vertical centrifugal 2 1,200/1,200/2,700 gpm <br />Pumps <br /> <br />Notes: <br />a Total firm capacity is with largest unit out --of service. <br />b Total capacity is with all units in service. <br />c Capacity noted is current rated capacity in NPDES permit. <br /> <br />Disinfection <br />Chlorine is delivered to the plant in 1-ton cylinders. Chlorinators dispense chlorine in the <br />desired quantities to each application point. The primary use of chlorine at the WPCF is <br />effluent disinfection. Chlorine is occasionally used to control filamentous bulking organisms <br />through addition to the RAS line. <br /> <br />MWMC_3.0_REV11.DOG 3-I I <br /> <br /> <br />