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F • • <br /> Process Description <br /> A process flow diagram is shown in appendix B . The continuous <br /> flow treatment system is designed to operateat 50 gpm. It is <br /> proposed to operate the system using two, 12—hour shifts per day <br /> manned by one foreman and one technician each shift . <br /> Incoming flow will be metered using a flow indicating totalizer <br /> and be manually controlled at 50 gpm. It is assumed that water <br /> may be transferred from the elevated cooling water tower drain <br /> line to the treatment system without the use of additional pumps . <br /> Chromium in the cooling water will be reduced in reactor No. 1 . <br /> This tank will be provided with an agitator and sized for 15 <br /> minutes retention. Secondary containment will be provided. The <br /> tank's contents will be maintained at pH 2 . 5 to 3 . 0 using <br /> sulfuric acid additions controlled by a pH meter . Secondary <br /> containment will also be provided for sulfuric acid containers . <br /> A sodium metabisulfite solution will be added as the reductant . <br /> Addition will be controlled by an ORP meter. Water from reactor <br /> No. 1 will flow by gravity to reactor No. 2 . <br /> Reactor No. 2 will be used to adjust the pH to approximately 8 . 5 <br /> using sodium hydroxide . The tank will be agitated and sized for <br /> a 15 minute retention time . Secondary containment will be <br /> provided for the tank and for the sodium hydroxide containers . <br /> The sodium hydroxide additions will be controlled by a pH meter . <br /> Water from reactor No . 2 will flow by gravity to pump tank No. 1 <br /> which will be used to transfer the water to a clarifier . A <br /> flocculant will be injected into the water stream just prior to <br /> the mixing section of the clarifier . Flocculant addition will be <br /> adjusted based upon the incoming water flow. <br /> The clarifier will consist of a rapid mix section for coagulation <br /> and a slow mix section for flocculation. Water from the slow mix <br /> section will pass through an inclined plate section where solids <br /> will settle to the bottom of the clarifier and the clear effluent <br /> will overflow into a pump pit and be transferred into several <br /> 21 , 000 gallon capacity portable storage tanks . The temporary <br /> tankage is required to allow surge capacity prior to discharge to <br /> the POTW. <br /> Sludge from the clarifier will be pumped to a 21, 000 gallon <br /> sludge storage tank . Overflow from the tank will be routed back <br /> to the clarifier. Sludge from the storage tank will be batch <br /> Processed in a plate and frame filter press after water <br /> processing has been completed. Based on laboratory tests, less <br /> than 15 cubic yards of dewatered sludge will be generated from <br /> treatment of the entire cooling water system. <br />