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Sludge Dewatering <br />The metal hydroxide sludges will have a water content of about <br />95% when they come out of the clarifier. This water content is <br />too great for the sludges to be suitable for sale or disposal. <br />These sludges, therefore, must be dewatered as much as possible <br />before they can be stored, disposed of, or sold. <br />The conventional plate -and -frame filter press is the most <br />effective filtration apparatus available. While other <br />dewatering devices such as vacuum filters can only attain a <br />water content of 70%, the plate and frame press can reduce <br />water content from 95% to 50%. <br />Sludges that cannot be sold through the secondary metals market <br />will be fixated with a Portland cement mixture and disposed. <br />Portland cement is a good fixation agent and contingent upon <br />the hazardous waste delisting procedure, the material produced <br />may be disposed of in sanitary landfills. <br />Copper Recovery <br />Copper will enter the Facility in five forms. Bulk shipments <br />of concentrated copper in acidic wastewater are treated by <br />electrolytic recovery. Bulk shipments of chelated copper <br />compounds in wastewater are first passed through an activated <br />carbon column to remove the chelating agents and then are <br />treated by electrolytic recovery. Copper concentrated on ion <br />exchange resins during the treatment of copper wastewaters is <br />flushed during resin regeneration with water, sulfuric acid and <br />caustic soda. The resin regenerant solution containing copper <br />is treated by electrolytic recovery. Copper cyanide complexes <br />concentrated on ion exchange resins are treated in a similar <br />manner. The resin is regenerated using caustic soda and water. <br />The regenerant solution containing copper cyanide complexes is <br />treated with sodium hypochlorite and caustic soda to oxidize <br />the cyanide and then treated by electrolytic recovery. Finally <br />bulk shipments of waste water containing copper cyanide <br />complexes are treated to oxidize the cyanide and then <br />transferred to the electrowinning tanks for electrolytic <br />recovery. <br />Wastewater from any and all of these treatments is neutralized <br />and filtered to remove suspended solids before discharge to the <br />sewer. <br />Any wastewater containing copper that is too contaminated for <br />economical electrolytic recovery is precipitated as copper <br />hydroxide and resold. <br />