City of Bloomington Officials Report Second Quarter 2018 Disinfection Byproduct Levels

Bloomington, Ind. - Disinfection byproduct (DBP) test results for the second quarter of 2018 have been released. Concentrations of DBPs were higher during this period than in the same quarter of 2017. The annual moving average concentrations continue to be below the maximum levels allowed by state and federal guidelines, and do not indicate that water has posed a health risk during this period. The two DBP categories, haloacetic acid (HAA5) and trihalomethane (TTHM), result from the reaction of chlorine disinfectant and naturally occurring organic material in the source water drawn from Lake Monroe.  For June 2018, the measured concentration of HAA5 levels at the eight testing sites ranged from 42 to 68 ppb. Total TTHM levels were between 58.5 ppb and 84.2 ppb. By contrast, June 2017 HAA5 results ranged from 29 to 39 ppb and TTHM, from 48.5 to 69.6 ppb.

“Source water quality in Monroe Lake has been very different this spring, with higher than average amounts of organic material,” said Utilities Director Vic Kelson. “Typically, these factors increase for a brief period in early spring, but this year they’ve remained elevated for several months, and well into June.”

June DBP concentrations at CBU’s sampling locations show a larger range of values than in most months. Samples were taken shortly after process changes at the Monroe Water Treatment Plant, notably the addition of powdered activated carbon (PAC) and a reduction in the disinfectant feed rate. CBU started adding PAC as a means of removing organic species that lead to taste and odor complaints in summer. DBP variation among sampling points is a function of the time required for treated water to travel from the Monroe plant to each of the eight sampling stations, which can range from two to seven days.

“Utilities staff continue to work proactively to keep our DBP numbers well within safe levels,” said Mayor John Hamilton. This spring’s unusual conditions remind us of our commitment to monitor and protect source water quality in Lake Monroe.”

Testing of CBU water is conducted by a private, independent laboratory. All water quality test results are available online at data.bloomington.in.gov under “Utilities.”


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