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2.0 PRETREATMENT SYSTEM <br /> The pretreatment system is located upstream of the Flow Equalization <br /> Basin. A flow diagram of the pretreatment system is given in Figure 1. <br /> The pretreatment system will receive water supply from the existing <br /> storm water collection sump. The water supply is collected from storm <br /> water runoff of the 16 acre asphalt-paved North Yard facility. The <br /> influent storm water will be treated for turbidity and arsenic reduction <br /> to specified limits. The treated water will flow by gravity to the <br /> existing Flow Equalization Basin. Water from the Flow Equalization <br /> Basin will be pumped through the existing ion exchange treatment system <br /> for final treatment prior to discharge to the Stockton Diverting Canal. <br /> The pretreatment system consists of an inclined plate (lamella) settler <br /> with flash mix and flocculation tank, caustic (sodium hydroxide) feed <br /> equipment, coagulant (ferric chloride or alum) feed equipment, polymer <br /> feed equipment, sludge pumps, control panel, and associated piping, <br /> valves and controls. <br /> 2.1 PRETREATMENT PROCESS FLOW <br /> The untreated stream enters the primary flash compartment of the <br /> Flash/Floc Tank where dilute caustic is dispersed using a flash mixer. <br /> The untreated water then flows into the baffled flocculation <br /> compartment. A more gentle mixing of the water will control the <br /> collision of smaller particles into the larger, more settleable floc. <br /> The speed of the floc mixer is remotely adjustable to provide the <br /> optimum energy input by changing mixing intensity. Varying mixer speed <br /> will control floc mass, which will govern settling characteristics. <br /> Polymer is injected into the floc compartment, if necessary, to further <br /> promote agglomeration of smaller particulate into larger floc. The <br /> 11654 2-1 <br /> VLS120588 <br />