On Sept. 22, the Columbia Water and Light Department resumed disinfecting the city’s water with chloramine after using only chlorine for the past three months. Chloramine, which is made by combining ammonia and chlorine, will stop the formation of chemical byproducts during disinfection.

During the summer months, only chlorine is added to the water to clear nitrate buildup in the distribution system, according to the [city website](http://www.gocolumbiamo.com/WaterandLight/Water/WaterQualityReport.php). For the other nine months of the year, the city uses the compound chloramine to disinfect the water supply.

Chlorine is added to water to kill germs and viruses in more than 20 percent of water sources in the nation. If the chlorine level in water exceeds four milligrams per liter, it is considered unsafe, according to the [Environmental Protection Agency](http://www.epa.gov/safewater/disinfection/chloramine/pdfs/all29_q.pdf). In Columbia’s 2015 [Water Quality Report](https://www.gocolumbiamo.com/WaterandLight/Water/WaterQualityReport.php), the city had 2.41 milligrams of chlorine per liter of water.

Columbia Water and Light spokesperson Connie Kacprowicz said Columbia has been using chlorine disinfection for a long time, starting not long after Water and Light formed in 1904. The agency began adding ammonia to the water in 2009 due to high levels of trihalomethanes, a chemical compound that increases the risk of cancer.

Organic materials already present in the water react with added chlorine to form trihalomethanes. In 2008, the city’s water exceeded the safe levels of trihalomethanes of 80 micrograms per liter.

To reduce byproducts like trihalomethanes, the Department of Natural Resources recommended that Columbia Water and Light add ammonia to the treatment process, Kacprowicz said. Since then, trihalomethane level went down by 50 percent, she said.

“There’s not any one perfect disinfection method,” Kacprowicz said. “All of them have their good points and their bad points.”

The downside to adding ammonia is the buildup of nitrates in pipes, which can cause bacteria growth. The water is treated first with chlorine and then a small amount of ammonia — the equivalent of six grains of salt to a gallon of water — is added, Kacprowicz said.

Kacprowicz said the agency stops adding ammonia during the summer months because water usage peaks and more chlorine-treated water can be flushed through the system, reducing the buildup of nitrates.

The added ammonia makes the water taste and smell more neutral, Kacprowicz said. She said some residents complain about the harsher taste of water only treated with chlorine.

Todd Houts, the director of MU’s Environmental Health and Safety, said whether or not water tastes good is based on what one is used to drinking.

“Every water supply tastes different,” he said. “People judge water based on what they grew up with and how their water tasted. Our water is pretty much about as natural as it can get.”

City water is not used by the university, which has its own water source. Houts said the university’s water is only treated with chlorine because it is so pure, and nitrification is not a problem.

“There are some minerals in it that you would expect to find in any water supply,” he said. “Chlorine is the standard for just disinfection.”