Connecticut Water Utility Successfully Removes 45% Of Trihalomethanes (THMs) With Quick-Turnaround Clearwell Intervention

While the addition of chlorine is one of the safest and most effective means for water disinfection, under certain circumstances chlorine in combination with naturally occurring organic compounds in water can lead to the formation of undesirable disinfection- byproducts (DBPs). One of the most common DBPs is a family of volatile compounds called trihalomethanes (THMs) which are regulated in the United States (U.S.) to a level of 80 ppb (parts per billion) by the U.S. Environmental Protection Agency. As water age increases (the time from water treatment in a plant to ultimate use), THM formation progresses with water utility operators closely monitoring their system’s locational running annual average (LRAA) for THMs.

In the past several years, Aquarion Water Company had been monitoring their system’s THM formation and attempting to lower them through treatment and distribution system changes. THM formation typically peaks as water temperatures increase seasonally and with increasing water age. During this time Connecticut was also experiencing severe drought which resulted in a reduction in water use and a subsequent increase in water age in their system. Aquarion engineers decided that reducing THM formation in the Laurel High Service Clearwell at the Stamford Water Treatment Plant (WTP) would eliminate concerns of elevated THM formation in the distribution system served by theWTP.