REMOVAL OF METAL CONTAMINANTS FROM AQUEOUS HAZARDOUS WASTES PRIOR TO BIOLOGICAL TREATMENT.

Laboratory studies were conducted to develop improved techniques to remove metals from industrial wastewaters. A representative wastewater sample was subjected to metals precipitation using sodium hydroxide, commercial lime, by-product lime, and lime plus sodium sulfide additions. The resultant slurries were examined for sludge settling rate, sludge volume, ease of filtration and filter cake quality. Filtrates were analyzed for chromium (total), copper, iron, nickel and zinc. The most efficient metals precipitation method studied involved neutralization of the wastewater with by-product lime, followed by addition of sodium sulfide. To assess its reliability, this treatment scheme was applied to eight weekly samplings of wastewater streams from a commercial facility (CECOS International, Inc. ). Filtrates were analyzed for residual copper, nickel and zinc levels, and sludges were examined for filterability and handling characteristics.