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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
[email protected]@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
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%
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