Plating Wastewater Systems Management

astewaters from all processes w are collected by gravity flow into acid-alkali (rinses), chromate, cyanide, spenttstripping acids, and cleaner sumps. The acid concentrates and cleaner concentrates are gradually fed into chromate and acid-alkali (rinse) sumps, respectively. Cyanide destruction is achieved by oxidation with sodium hypochlorite whereas hexavalent chrome is reduced to trivalent chrome with sodium metabisulfite. The oxidized cyanide and reduced chrome are sent to the neutralization tank; the pH is raised with sodium hydroxide for metal hydroxide precipitation. The treated wastewater is then mixed with an anionic polymer at the rate of 1 to 5 ppm to promote flocculation. Clarification is achieved through a slope plate clarifier, followed by final sand filter polishing prior to discharge into the sewer. The dewatering of sludge is achieved with a five cubic foot plate and frame filter press and is then removed and collected for landfill disposal.