(56a) Comprehensive Testing of Hydrogen Peroxide to Replace the Chlorine Pre-Oxidant Feed at the Rapid Mix in a Drinking Water Filter Plant

During two years of plant optimization testing with a state of the art mobile Pilot Plant, a myriad of treatment optimization test were conducted. The reason for optimization testing was to reduce the Disinfection By-Product (DBP) formation that takes place through the reaction of Chlorine and DBP precursors. DBP's are regulated by the EPA and state agencies as and are suspected carcinogens. Typical DBP precursors are in the form of Total Organic Carbon (TOC) The focus of the optimization testing was to improve upon the 40 percent reduction of the TOC present in the finished water. The reduction of TOC leads to the reduction of DBP precursors further leading to the reduction of DBP's. Another aspect of the optimization testing focused on replacing the Chlorine feed at the rapid mix. That Chlorine feed was used as a pre-oxidant to oxidize iron and manganese as well as a deterrent to algal growth in the sedimentation basin. Algal growth in the sedimentation basin leads to poor filter performance through the granular media filters as well as taste and odor issues in the finished drinking water. While Chlorine residuals are required for drinking water, minimizing the contact time between DBP precursors and Chlorine reduces the amount of DBP's. Reducing the contact time leads to replacing any Chlorine feed that takes place before the final disinfection after the filters. Hydrogen Peroxide has been gaining favor as an algal controller in drinking water filter plants therefore its effectiveness was evaluated as a replacement to the rapid mix Chlorine feed. The determination of the Hydrogen Peroxide's effectiveness was based on DBP formation, TOC removal, turbidity removal, iron and manganese residuals, taste, odor, pH stability, settled turbidity, coagulant dose, finished water Chlorine demand, filter headloss development, filter effluent turbidity, and filter runs times. DBP testing used standard methods for Simulated Distirbution System 0 and 7 day sampling. The 0 and 7 day sampling allowed for simulation of DBP formation once the finished water was pumped into the distribution system. Parameters such as pH stability, settled turbidity, TOC, finished effluent turbidity, algal growth, filter headloss development, and filter run times showed no positive or negative effects. Iron and Manganese residuals showed increases in approximately 70 percent of the samples. Color, taste, and odor were not affected. However DBP formation actually increased in over 60 percent of the samples at doses 1ppm and less of Hydrogen Peroxide. Increasing the Hydrogen Peroxide dose above 1ppm increased the finished Chlorine demand to the point that it significantly increased the DBP formation above existing conditions.