MARYVILLE, Mo. — In a press release Wednesday, Maryville City Manager Greg McDanel said that an increase in a naturally occurring compound in Mozingo Lake is what’s been causing a distinct taste and smell for some water users.
“We do have increased geosmin, which is impacting the taste and odor,” McDanel said at last week’s City Council meeting.
According to the city’s press release, geosmin is caused by bacteria in soil and algae found in surface water. In cases where it affects drinking water, typically cold temperatures kill off algae in the water source, and the dead algae release geosmin. The compound is particularly noticeable to humans even at extremely low levels, but is not harmful.
The general threshold for human detection of geosmin is about 15 nanograms per liter, but for some more sensitive people can be as low as 5 nanograms per liter.
Consequently, some may notice the taste and others may not.
When geosmin or other algae-related compounds are noticeable, the city’s press release suggested customers may chill the water in a refrigerator or add a few drops of lemon juice to improve the taste and reduce odors. Conversely, heating the water increases the volatility of the compound, so the smell may be more noticeable in the shower or when used for hot beverages.
McDanel said that adjustments in the water treatment process are being made, and include adding powdered activated carbon to reduce the levels of geosmin.
“We are, unfortunately, maxed out at our powdered activated carbon amount at the plant, so we’re hoping for a little bit of maybe cooperation with the weather to drive down those geosmin numbers,” McDanel said at last week’s Council meeting.
In the press release, McDanel added that the PAC applications are able to reduce levels by 88-90 percent, but the remaining percentage is impossible to remove through the current technology at the water treatment plant. Additionally, applying too much PAC can damage treatment membranes, and other adjustments could cause high turbidity levels.
Later this month, McDanel said that it’s likely a report from contractor HDR Engineering will be presented to the City Council. HDR was awarded a contract in June to produce a feasibility study analyzing all options available to the city to overhaul its water systems from source management to new filtration infrastructure. In the press release, McDanel said that recommendations are expected to range from additional algicide applications at the lake to construction of a new multi-million-dollar water treatment plan with updated technologies.
Those efforts will join the city’s existing initiatives that focus on the source water from the Mozingo Lake watershed area to improve the quality of the raw water.