“Minimizing Disinfection By-products by Switching to Chloramines”
Batesville Water & Gas, Batesville, IN
Background
Batesville Water & Gas has uses surface water. Last year started out as a nightmare as far as DBP’s (TTHM’s & HAA5’s) were concerned. Batesville had historically used pre-chlorine in an attempt to reduce the algae coming into their plant. This resulted in DBP’s that started to climb in early May. The TTHM’s left the plant tap (POE) at 52.91 ug/L and increased to 218.5 ug/L in the distribution system. In July Batesville switched from pre-chlorine at their intake to EarthTec, a copper sulfate liquid solution to control the algae. TTHM’s were reduced to 42.39 ug/L at the Plant Tap (POE). This helped slightly, but they still had problems in the system.
The Disinfection By-Products Rule has caused serious problems for many surface water plants. Starting in the early spring and extending into late summer in 2008, Batesville Water & Gas had continual problems. The changes in the rule as far as sampling locations and the new “rolling averages” were difficult enough, but there seemed to be higher levels of algae and other organics coming into the raw water intakes. This made things even more difficult.
Solution
Water Solutions Unlimited began working with Batesville on the DBP problem in January of 2008. Their first recommendation was to change from just testing DBP’s in the distribution system, to also testing at the Plant Tap (POE). This helped them evaluate where the DBP’s were forming in their system both at the plant and in the distribution system.
The second recommendation was to switch from free chlorine to chloramines. This required the feed of ammonium sulfate in conjunction with the post-chlorine feed point at the clarifier to form a mono-chloramine molecule for disinfection. Don Morrison, an engineer with Main Stream (formerly Ecologistics Limited) of West Lafayette, IN was consulted to determine exactly where all chemicals should be fed to still provide proper CT values.
The permit was submitted and approved and all equipment and taps were made. A two hour training session on chloramination was provided by WSU to all Batesvuille Water & Gas operators.
Within days TTHM levels were reduced to 2.9 ug/L at the Plant Tap (POE) and 29.95 at the end of the distribution system. This was a reduction of 86 %. Batesville is looking forward to being on chloramines during the entire year in 2010.
Total Tri-Halo-Methane (TTHM) Results In Micrograms per Liter (ug/l)
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Pre-chlorination at Reservoir Intake & Re-chlorination at Point of Entry
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Date
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Location
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TTHM in ug/l
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February 12, 2008
|
Reservoir Intake
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60.8
|
|
May 13, 2008
|
Reservoir Intake
|
125
|
|
May 13, 2008
|
Point of Entry
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52.91
|
|
May 13, 2008
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Far End of Distribution
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218.5
|
|
|
|
Switched to Earth Tec from Pre-chlorination (July 1, 2008)
& Continued Chlorination at Point of Entry
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|
Date
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Location
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TTHM in ug/l
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|
July 1, 2008
|
Reservoir Intake
|
73.9
|
|
August 12, 2008
|
Reservoir Intake
|
71.6
|
|
August 12, 2008
|
Point of Entry
|
42.39
|
|
November 12, 2008
|
Reservoir Intake
|
30
|
|
|
|
Continued Earth Tec &
Switched to Chloramination from Free Residual Chlorine (November 25, 2008)
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|
Date
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Location
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TTHM in ug/l
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|
November 25, 2008
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Reservoir Intake
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5.0
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|
December 16, 2008
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Reservoir Intake
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4.0 / 3.9
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|
December 16, 2008
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Point of Entry
|
2.9
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|
December 16, 2008
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Far End of Distribution
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29.95
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