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TREATMENT OF METAL FINISHING WASTES BY SULFIDE PRECIPITATION
Citation:
Schlauch, R. AND A. Epstein. TREATMENT OF METAL FINISHING WASTES BY SULFIDE PRECIPITATION. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/2-77/049 (NTIS PB267284), 1977.
Description:
This project involved precipitating heavy metals normally present in metal finishing wastewaters by a novel process which employs ferrous sulfide addition (Sulfex), as well as by conventional treatment using calcium hydroxide for comparison purposes. These studies consisted of laboratory jar tests and bench scale tests to determine the chemical and physical requirements for the precipitation of the heavy metals and the subsequent dewatering of the resulting sludges. Following the laboratory tests, pilot plant tests were made to confirm the validity of the laboratory test results and provide realistic operating data. As a result, it was demonstrated that Sulfex is a technically viable process that is superior to conventional hydroxide precipitation for removal of copper, cadmium, nickel, and zinc from a given influent. And, when operated in the pH 8-9.0 range, the Sulfex process will remove total chromium to a concentration which is less than or equal to that from a conventional hydroxide precipitation process. Hexavalent chromium can be removed by Sulfex in a one-step operation. The effluent quality from either process is dependent on the type and concentration of complexing agents present in the influent.