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STOCKTON PLATING, INC. <br /> CAD 009 212 929 <br /> TREATMENT UNIT OPERATION <br /> FTU 1 - Chromium Reduction <br /> Hexavalent chrome bearing wastewaters are collected in the in-ground sump <br /> where chrome reduction is continuously performed. Sulfuric acid is piped into the <br /> tank as the reducing agent. The pH is kept at around two (2) to ensure a <br /> complete reduction. The minimum reaction time is five (5) minutes. The <br /> hexavalent chromium is reduced to the less toxic trivalent chromium and then <br /> pumped to the combined heavy metal waste sump. <br /> FTU 2 - Heavy Metal Holding tank <br /> All the waste water containing metals are pumped to an in-ground tank before <br /> being pumped to the heavy metal holding tank. In the holding tank the pH is <br /> continuously monitored and adjusted to between 6 and 11. The water is next <br /> pumped to the flocculant tank. <br /> FTU 3 - Clarifier Tank <br /> Metal hydroxides settle out under force of gravity to form a sludge in the baffled <br /> two part clarifier. The water is continuously fed from the first tank to the second <br /> tank. The clarified water then passes to the final pH adjust tank. The sludge is <br /> pumped from the bottom of the tank to the sludge press. <br /> FTU 4 - Filter Press <br /> The metal hydroxide sludge is pressed into a filter cake using one of two Filter <br /> Presses and manifested off-site for disposal. <br /> FTU 5 - Container Rinsing <br /> Approximately 20 drums a month are rinsed per month. About half are returned <br /> to the chemical supplier and about half are crushed and disposed of offsite as <br /> non hazardous waste. <br />