DISINFECTION BY PRODUCTS DISINFECTION BY PRODUCTS IN IN

ALASKAN WATER SYSTEMSALASKAN WATER SYSTEMS

byby

Lee Johnson, P.E.Lee Johnson, P.E.ADEC Drinking Water ProgramADEC Drinking Water Program

Northern ProgramNorthern Program

907-451-2179907-451-2179Lee.johnson@alaska.govLee.johnson@alaska.gov

COMPARISON OF TOTAL SYSTEMS AND COMPARISON OF TOTAL SYSTEMS AND SYSTEMS WITH DBP ISSUESSYSTEMS WITH DBP ISSUES

0

100

200

300

400

500

600

700

800

TOTAL WATER SYSTEMS DISINFECT WITH DBP ISSUES

SYSTEMS THAT DISINFECTSYSTEMS THAT DISINFECT

NO DBP ISSUES

90%

DBP ISSUES

10%

DISTRIBUTION OF WATER SYSTEMS DISTRIBUTION OF WATER SYSTEMS WITH DBP ISSUESWITH DBP ISSUES

Northern36%

Southeast42%

South Central and Western

22%

IS SOURCE TYPE THE ISSUE?IS SOURCE TYPE THE ISSUE?

DBP ISSUES BY SOURCE TYPE

SURFACEWATER

GROUNDWATER

11 %

89 %

IS FILTRATION TYPE THE ISSUE?IS FILTRATION TYPE THE ISSUE?

DBP ISSUES BY FILTRATION TYPE

DIRECT27%

ALTERNATE30%

UN

FIL

TE

RE

D 6%

SLO

W S

AND

6%

CONVENTIONAL31%

CONVENTIONAL FILTRATION PACKAGE PLANTCONVENTIONAL FILTRATION PACKAGE PLANT

DIRECT FILTRATIONDIRECT FILTRATION

BAG FILTER SYSTEMBAG FILTER SYSTEM

CARTRIDGE & BAG FILTER SYSTEMCARTRIDGE & BAG FILTER SYSTEM

MEMBRANES & DIATOMACEOUS EARTHMEMBRANES & DIATOMACEOUS EARTH

Membranes are classified as Alternate Membranes are classified as Alternate Filtration under LT1Filtration under LT1

Membrane filtration systems are meeting the Membrane filtration systems are meeting the DBP mcl’sDBP mcl’s

Only 1 DE filtration plant in Alaska. DE Only 1 DE filtration plant in Alaska. DE plant is meeting the DBP mcl’s.plant is meeting the DBP mcl’s.

MAXIMUM DBP’S BY FILTRATION TYPEMAXIMUM DBP’S BY FILTRATION TYPE

0

100

200

300

400

500

600

700

800

900

1000

ALTERNATE SLOW SAND DIRECT CONVENTIONAL

FILTRATION TYPE

UG

/L

TTHM HAA5

IS THE ISSUE TTHM’s OR HAA5’s?IS THE ISSUE TTHM’s OR HAA5’s?

Approximately 36 systems are currently Approximately 36 systems are currently exceeding standards or have had samples exceeding standards or have had samples over the limit.over the limit.

11% have only TTHM issue.11% have only TTHM issue. 8% have only HAA5 issue.8% have only HAA5 issue. 81% have both a TTHM and HAA5 issue.81% have both a TTHM and HAA5 issue.

IS DETENTION TIME THE ISSUE?IS DETENTION TIME THE ISSUE?

Of the 36 systems evaluated only 6 were fill Of the 36 systems evaluated only 6 were fill and draw.and draw.

Fill and draw systems are those that do not Fill and draw systems are those that do not routinely filter on a daily basis but rather routinely filter on a daily basis but rather filter to storage and meet distribution filter to storage and meet distribution demand off storage.demand off storage.

Time periods between filtering can range Time periods between filtering can range from every few days to a year or more.from every few days to a year or more.

LONG DETENTION TIMES?LONG DETENTION TIMES?STORED WATER DBP'S

50

100

150

200

250

12/1

3/20

06

1/13

/200

7

2/13

/200

7

3/13

/200

7

4/13

/200

7

5/13

/200

7

6/13

/200

7

7/13

/200

7

8/13

/200

7

DATE

UG

/L

TTHM SYSTEM A

HAA5 SYSTEM A

TTHM SYSTEM B

HAA5 SYSTEM B

WHAT HAVE SYSTEMS BEEN TRYING?WHAT HAVE SYSTEMS BEEN TRYING?

Controlling detention timesControlling detention times– Converting treated water storage to raw water storageConverting treated water storage to raw water storage– Flushing distribution systemFlushing distribution system

Controlling disinfection levelsControlling disinfection levels Cleaning raw water reservoirCleaning raw water reservoir Trying different coagulants/flocculantsTrying different coagulants/flocculants Piloting new filtration technologyPiloting new filtration technology GAC filter mediaGAC filter media Different disinfectantsDifferent disinfectants Adding PACAdding PAC Looking at other water sourcesLooking at other water sources