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Disinfection Challenges and DBP Issues in Alaskan Water Systems

This document examines disinfection methods and disinfection byproduct (DBP) issues in Alaskan water systems, with a focus on systems exceeding regulatory standards. It discusses various water filtration methods, including conventional and membrane filtration, and their impact on total trihalomethanes (TTHMs) and haloacetic acids (HAA5) levels. The report evaluates 36 systems facing DBP challenges, the role of detention times, and strategies being implemented to manage disinfection levels and improve water quality, including new technologies and maintenance practices.

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Disinfection Challenges and DBP Issues in Alaskan Water Systems

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  1. DISINFECTION BY PRODUCTS IN ALASKAN WATER SYSTEMSby Lee Johnson, P.E. ADEC Drinking Water Program Northern Program 907-451-2179 Lee.johnson@alaska.gov

  2. COMPARISON OF TOTAL SYSTEMS AND SYSTEMS WITH DBP ISSUES

  3. SYSTEMS THAT DISINFECT

  4. DISTRIBUTION OF WATER SYSTEMS WITH DBP ISSUES

  5. IS SOURCE TYPE THE ISSUE?

  6. IS FILTRATION TYPE THE ISSUE?

  7. CONVENTIONAL FILTRATION PACKAGE PLANT

  8. DIRECT FILTRATION

  9. BAG FILTER SYSTEM

  10. CARTRIDGE & BAG FILTER SYSTEM

  11. 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.

  12. MAXIMUM DBP’S BY FILTRATION TYPE

  13. 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.

  14. 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.

  15. LONG DETENTION TIMES?

  16. 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

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