AWWA ACE68625

This powerpoint presentation begins by providing a brief overview of the Mystic Water System. The problem statement includes the following: compliance with Stage 2 Disinfectant/Disinfection Byproduct (D/DBP) Rule; and, control of Mn and Fe. The study objectives include the following: evaluate impacts of pre-filter chlorine on DBP levels; and, investigate options to decrease DBP formation while maintaining Fe and Mn removal. The Scope of Work includes the following: full-scale studies of sampling across plants at various prefilter Cl₂ doses, DBP and metals analyses, collecting filter media cores; and, bench-scale studies of chlorine demand, kinetics, DBP formation, chloramination, jar and column experiments. Presentation conclusions indicate that: pre-filter Cl₂ and KMnO₄ rapidly oxidized iron and manganese (with pH controlled at 7.0-7.2); a low pre-filter chlorine dose (2 mg/L) produces similar filter influent water quality conditions as that of a high prefilter chlorine dose (6-8 mg/L); plant effluent DBP formation directly proportional to prefilter chlorine dose; decreasing the pre-filter chlorine from 8 mg/L to 2 mg/L resulted in 70-90% decrease in plant effluent DBP formation and short term control of Mn and Fe; after 35-55 days low pre-filter chlorine (2.0 mg/L) resulted in an apparent release of Mn; and, increasing pre-filter chlorine to 4-5 mg/L prevents Mn release, but increases DBP formation. Includes figures.