COLUMBIA — Organic matter in nine out of 14 of Columbia's wells is contributing to the formation of a carcinogen in the city's drinking water, a new study by MU researcher Enos C. Innis has found. The study was funded by Columbia Water and Light in response to elevated levels of trihalomethanes, which are carcinogenic, reported in the city's drinking water in 2007.
In the new report, which was released after three months of testing, the wells indicate high levels of organic matter that contribute to the formation of trihalomethanes, said Connie Kacprowicz, spokeswoman for Columbia Water and Light.
Trihalomethanes are the product of a reaction between organic matter and the chlorination process used to disinfect well water before it enters the distribution system.
"There is a high level of organic components in the wells," Kacprowicz said.
Also, elevated levels of chloride found in the wells in previous studies indicate that the organic matter might be seeping underground from nearby wetlands at the Eagle Bluffs Conservation Area. Wastewater treated in city-operated wetlands is used to flood the state-owned conservation wetlands, located near city wells in the Missouri River bottoms near McBaine.
Chloride levels, used to trace organic components, have increased since the city started flooding the Eagle Bluffs wetlands with treated wastewater. Though it isn't definitive, the timeline of these effects is a cause for concern that wastewater is infiltrating the well system.
"Organic matter can come from a number of sources, such as rainwater, river water, aquifers or treated wastewater effluent," Kacprowicz said. "The higher chloride levels can be a result of any of these factors.
"I don't think we're in the position to say one way or another that the source is Eagle Bluffs," she said. "We need to see more research, but it is a possibility."
John O'Connor, an environmental engineering consultant and former MU water engineering professor, is more uneasy. He would rather see "a more urgent treatment" than a full year's worth of testing.
He said adding ammonia to neutralize the chlorine's instability could reduce the levels of trihalomethane. He said many other cities use this approach and that it actually decreases the chlorine taste in the water.
The city has considered the use of ammonia, but more testing needs to be done, Kacprowicz said.
Levels of trihalomethane in the city's drinking water have exceeded the threshold set by the federal government.
Chlorine is necessary to get rid of bacteria and other water-borne diseases. The city, in response to the higher trihalomethane levels, decreased the amount of chlorine used in the treatment process.
"It's a balancing act," O'Connor said. "You need to keep a residual amount of disinfectant in order to control microbial growth, but then there's going to be trihalomethanes. You walk a tightrope."