| Abstract |
The study obtained field data on the inorganic contaminants and constituents in residuals produced by Water Treatment Plants (WTPs). Eight WTPs were studied based on treatment technology, contamination or suspected contamination of raw water, and efficiency in the removal of contaminants. Two WTPs obtained raw water from rivers and the remining six from groundwater sources. Suspected contaminants included arsenic, radium, and uranium. Treatment technologies included coagulation and flocculation, lime softening, filtration, adsorption on chemically coated sand, anion exchange, and reverse osmosis. The residuals produced by the treatment technologies included sludge, brine, backwash, rinse water, and reject streams. The results demonstrated that non-radioactive inorganic contaminants accumulated in WTP residuals. Chemical coagulation sludges (lime, alum, ferric sulfate) apparently limit the mobilization of inorganic contaminants from sludge solids into surrounding liquids. Metals were rarely detected in the extracts of sludges tested in accordance with the toxicity characteristics leachate procedure (TCLP). The metal levels in the TCLP extracts were well below the maximum concentration levels and thus were not characteristic of a hazardous waste. Radium was detected in the sludges, brines, reject waters, and backwashes of WTPs. |
