Elevated levels of haloacetic acids again detected in city water; plant upgrades expected to reduce the levels
The Great Falls drinking water supply has again exceeded the maximum contaminant level for haloacetic acids.
The elevated levels were detected again in the fourth quarter of 2018, which was October through December.
The elevated levels of haloacetic acids, or HAA5, were also detected in the second and third quarters of 2018.
HAA5 are five haloacetic acid compounds that form when chlorine reacts with natural organic matter present in the source water which for Great Falls is the Missouri River.
City officials have speculated that the cause of the elevated HAA5 was wildfires further up-stream since that can increase organic matter, but officials at the Montana Department of Environmental Quality said it’s very difficult to pinpoint the cause since river conditions are complex and always changing.
“The Missouri River watershed is extensive, so to pinpoint the main source of the organics can become challenging,” said Brian Hogenson, disinfection byproducts rule manager at DEQ.
Hogenson said HAA5 is formed when source water organics come in contact with chlorine but there’s a seasonal component to it based on water conditions, temperature and ph levels.
IHAA5 is also a relatively new contaminant and science is still identifying these compounds, Hogenson said, though DEQ has been regulating them since the early 2000s.
The size of the Great Falls drinking water system requires eight sample sites for the contaminants and during the fourth quarter, the HAA5 levels fell from the third quarter, but two sites still exceed the limit of 60 parts per billion. Those sites had 69 and 61 parts per billion of HAA5, according to the city’s sampling report submitted to DEQ.
Under the regulations, if one site exceeds the HAA5 limit, the entire system is considered out of compliance, according to DEQ.
Eugene Pizzini, the section supervisor for water supply at DEQ, said that when a public water system identifies they have a problem, they’re supposed to maximize efforts to remove the precursors. So if wildfires created more carbon in the source water, a system would need to take efforts to mitigate that.
Hogenson and Pizzini said Great Falls is in the middle of a significant upgrade to the water treatment plant and are also making changes to the disinfectant process to address to elevated levels of HAA5.
Hogenson said Great Falls uses chloramine as secondary disinfectants and those are a combination of chlorine and ammonia. The benefit, he said, is those don’t break down as quickly as chlorine, extending their disinfectant lifespan in the water.
It’s also important, Pizzini said, because when ammonia is attached to chlorine, the chlorine molecules are no longer looking to attach to organics and reacting to form HAA5.
But the city also pre-chlorinates water before it goes through the treatment process and the DEQ officials said there’s discussion of changing that process to see if it reduces the HAA5 levels.
Earlier in January, the city sent a notification letter to users of the drinking water system of the HAA5 levels. In the letter, city officials state that new chemical feed and ultra violet systems at the water plant are scheduled for completion in February.
“The chemical feeder will enable us to control our chlorination/chloramination process with more precision. In general, this should reduce the amount of chlorine that is available in our process to react with source water(s) natural organic matter, thus reducing the initial formation of HAA5’s. Once implemented, the new treatment system upgrades are likely to reduce the HAA5 concentrations,” according to the city’s letter.
HAA5 is a health threat and that’s why it’s regulated, Pizzini said, but right it’s not an acute contaminant and would have to be consumed over a long period of time to potentially cause serious health problems.
There’s no need to boil the water and since it’s a chemical compound, it’s not a recommended treatment option, according to the DEQ officials.
The city has issued the public notices as required by DEQ and city officials update the City Commission on the situation during public meetings each time the levels are elevated.
Other public water systems, primarily surface water systems, in Montana are exceeding the levels of allowable disinfectant byproducts. Most of those systems are having trouble with a different group of byproducts though, trihalomethanes, which are limited to 80 parts per billion and are carcinogenic.