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1 . 2 Description of Pretreatment System This system is designed to receive selected waste streams of platting and cleaning rinses from the metal processing area , at a max . flow rate of 80 GPM and remove metals to a level required by federal pretreatment requirements . Concentrated dumps will be transferred to a collection feed tank and metered into the rinse stream to prevent overwhelming the system' s treatment capacity. The rinse water will be directed to a in-ground sump for collection . The collected liquor will then be pumped to an above ground pre-treatment system for further processing . The first stage of the pre-treatment process will include a PH adjustment system controlled by a panel mounted - pH meter connected to a pH prove in the treatment station. The probe will sense the pH of the incoming liquor and initiate the flow of caustic necessary to maintain a pH of 6 . 0 - 10.0 in the reactor vessel . The pH adjustment process will precipitate the insoluble metallic hydroxides and then overflow to the second stage of the treatment process , flocculation. Flocculation is necessary to coagulate the precipitated metallic hydroxide to a larger particle for more efficient settling . This is accomplished by the addition of organic polymer and slow mixing of the liquid to prevent disassociation of the coagulate once formed. The polymer feed system will feed a liquid polymer into a water filled system for mixing and injection into the flocculation reactor. After coagulation , the liquor will overflow to a clarifier in which the coagulated particles will settle to the bottom and clear water will overflow to the sewer. Sludge collected in the clarifier will be removed by an automatic sludge withdrawal system operating from two ( 2 ) timers . The first timer is utilized to control the frequency of Pludge removal . The second, initiated by the first timer, is utilized to control the duration of the sludge removal process . Duration control. is necessary to provide more efficient sludge dewatering by the filter press . Sludge dewatering is accomplished by pumping the thickened sludge at a high pressure through a recessed plate filter press. The sludge will be retained to form a semi-dry cake approx . 40 - 50 % by weight solids . The dry cake will be manually removed and transferred to a holding container for disposal to an approved landfill . The filter press has 4 cubic foot capacity with an automnt.ir opening and closing device . This 4 cubic foot dry cake will be collected in a 5 cubic foot rolling dumpster to transfer the sludge from the press to the holding container. All control instruments have an audible alarm with flashing lights to signal an out of control condition of high level in the tanks .