AWWA JAW30300

As a result of increased speculation that the total residual concentration of chlorine dioxide and its inorganic species will soon be regulated, supplemental studies were performed to determine the effectiveness of various reducing agents for reducing or eliminating chlorine dioxide and chlorite ion residuals in finished water. Three kinds of experiments were conducted: 1) pilot plant studies with sulfur dioxide, 2) bench-scale studies with SO2, sodium metabisulfite and sodium thiosulfate, and 3) jar tests with reduced iron chloride. The effectiveness of ferrous iron in achieving the desired reductions is examined along with promising results obtained with sodium thiosulfate. Specific difficulties encountered with the sulfur dioxidesulfite ion method of chlorite ion reduction are also presented. Includes 21 references, tables, figures.