COMPOSITION AS WATER PURIFYING AGENT FOR WASTE WATER CONTAINING HEXAVALENT CHROMIUM

摘要

PURPOSE:To obtain a compsn. as a water purifying agent having such characteristic that one-stage treatment of waste water contg. hexavalent chromium is enabled and enabling simultaneous treatment of org. pollutants by preparing an aq. iron salt soln. contg. ferrous ions and ferric ions in a specified ratio. CONSTITUTION:Hexavalent chromium in waste water is reduced to harmless trivalent chromium with ferrous ions, the pH of the waste water is adjusted to a nearly neutral range to convert the trivalent chromium into hydroxide together with ferric ions and org. pollutants are flocculated, settled and separated. At this time, the ratio between Fe2+ and Fe3+ in a compsn. as a water purifying agent is regulated to 1:=2. COD and suspended solids(SS) as well as Cr6+ are removed and iron ions are insolubilized, settled and removed. Since the waste water is treated in only one stage with only the purifying agent, the cost of treatment is reduced and equipment is simplified. Post-treatments such as separation of sediments and dehydration of sludge are advantageously carried out.