AWWA ACE93164

Pilot plant studies were done to: develop a correlation between color removal and ozone dose at different treatment configurations to determine the ozone doses required to achieve finished water color values of 10 pcu and 5 pcu; determine the effect of lower pH values on the required ozone dose; and identify the necessary design criteria. The results of the pilot study led to the following conclusions: the use of a preoxidant for sulfide oxidation significantly reduces the ozone dose required to achieve a color of 5 pcu; assuming preoxidation, a transferred ozone dose of 8 mg/L at a softened water pH of 10 will achieve a true color of 5 pcu. A transferred ozone dose of 6 mg/L at softened water pH of 9 will achieve a true color of 5 pcu; in the absence of residual disinfectant, color reformed following ozonation; the ozone contactors should be designed to allow for the addition of ozone in multiple cells to prevent the reformation of color within the ozone contactor; the ozonated water should be treated with residual disinfectant immediately after ozonation to control the reformation of color; use of chloramines as residual disinfectant should be continued to prevent the formation of excessive THMS.