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DISINFECTION BY PRODUCTS IN ALASKAN WATER SYSTEMS by. Lee Johnson, P.E. ADEC Drinking Water Program Northern Program 907-451-2179 Lee.johnson@alaska.gov. COMPARISON OF TOTAL SYSTEMS AND SYSTEMS WITH DBP ISSUES. SYSTEMS THAT DISINFECT. DISTRIBUTION OF WATER SYSTEMS WITH DBP ISSUES.
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DISINFECTION BY PRODUCTS IN ALASKAN WATER SYSTEMSby Lee Johnson, P.E. ADEC Drinking Water Program Northern Program 907-451-2179 Lee.johnson@alaska.gov
MEMBRANES & DIATOMACEOUS EARTH • Membranes are classified as Alternate Filtration under LT1 • Membrane filtration systems are meeting the DBP mcl’s • Only 1 DE filtration plant in Alaska. DE plant is meeting the DBP mcl’s.
IS THE ISSUE TTHM’s OR HAA5’s? • Approximately 36 systems are currently exceeding standards or have had samples over the limit. • 11% have only TTHM issue. • 8% have only HAA5 issue. • 81% have both a TTHM and HAA5 issue.
IS DETENTION TIME THE ISSUE? • Of the 36 systems evaluated only 6 were fill and draw. • Fill and draw systems are those that do not routinely filter on a daily basis but rather filter to storage and meet distribution demand off storage. • Time periods between filtering can range from every few days to a year or more.
WHAT HAVE SYSTEMS BEEN TRYING? • Controlling detention times • Converting treated water storage to raw water storage • Flushing distribution system • Controlling disinfection levels • Cleaning raw water reservoir • Trying different coagulants/flocculants • Piloting new filtration technology • GAC filter media • Different disinfectants • Adding PAC • Looking at other water sources