GENTRY -- Though the water is safe to drink, water customers in Gentry, Highfill and other communities receiving their water exclusively from the Benton/Washington County Regional Public Water Authority received public notice that "the level of total trihalomethanes, a disinfectant by-product, in the water exceeded the maximum contaminant level of 80 parts per billion." And another similar notice will likely need to be sent again later this year.
Trihalomethanes are a by-product of adding chlorine to water in the treatment process.
The Water Research Center's website states: "Trihalomethanes (THM) are a group of four chemicals that are formed along with other disinfection by-products when chlorine or other disinfectants used to control microbial contaminants in drinking water react with naturally occurring organic and inorganic matter in water."
According to the notice sent out to water customers in Gentry, the level of THMs was 82 ppb for the period of October through December and 87 ppb from January through March of this year. Current levels in Gentry are well below the maximum safe level -- at 51.7 ppb -- but, because the levels are averaged over four quarters, those average numbers are expected to remain above the safe level through most of 2016 and another public notice is expected to be issued late this summer.
According to the Arkansas Department of Health, "there is no immediate health risk from consuming the water." The notice said that the failure to meet the 80 ppb requirement did "not mean the water was unsafe" or that alternative water sources should be used.
The cause of the problem, according to David McNair, Gentry's Public Works director and also board member and chairman on the Benton/Washington County Regional Public Water Authority board, is connected to the heavy rain events in the summer of 2015 and again in November and December of 2015 which caused increased levels of organic material in Beaver Lake and caused the need for the use of additional chlorine in the water coming through the BWRPWA treatment plant to ensure the water would be safe for public consumption and to avoid the possible need for boil orders.
The lake still hasn't fully cleared, McNair said.
The need for the use of additional chlorine in the water treatment reduced the health risk associated with drinking water with higher levels of organic material but raised the levels of THMs.
BWRPWA also had alternative primary coagulants on hand at all times and used mixers and adjusted the operating levels in tanks to decrease water age in the system, according to the notice.
McNair explained that the Environmental Protection Agency set the standards based on a possible health risk to people if they consume excessive amounts of THMs over long periods of time. The notice said some people drinking water with high levels of THMs over many years may experience problems related to the liver, kidneys or the central nervous system and may have an increased risk of cancer.
"If a person were to drink three liters of water a day over a period of 70 years, they might be at a higher risk," McNair explained, adding that the spike in levels was a brief, short-term event, and the water is well below the maximum safe level now but it will take time to bring the averages back down because of high readings in the third and fourth quarters of 2015.
According to the Water Research Center website, "THM levels tend to increase with pH, temperature, time and the level of 'precursors' present. Precursors are organic material which reacts with chlorine to form THM's."
Coagulants are used to remove organic material before chlorination to keep THM levels down, according to the website.
The public notices are required under the Safe Drinking Water Act, a federal law which requires the EPA to set drinking water standards for all public water systems.
General News on 03/16/2016