DENVER — If you've noticed that your tap water tastes or smells a little off, it may be affected by a common, and harmless, seasonal affliction. The sun and consistent heat are to blame.
Treatment manager for Denver Water's south system facilities Russell Plakke says the earthy odor and smell is from geosmin.
Geosmin is a natural bacterial product that is responsible for the earthy taste of beets and the dirt-like smell after it rains, according to the American Chemical Society.
In water, Plakke said it is produced by bacteria known as blue green algae. People can detect it by taste and smell in tiny quantities, about four or five ppt (parts per thousand).
The algae is found primarily in lower-elevation reservoirs like the Marston Reservoir in Southwest Denver. Plakke explained that these reservoirs tend to get warmer from the sun than higher-elevation reservoirs.
“Higher level reservoirs are deeper and cooler. They don't get quite as much heating from the afternoon sun. There's less nutrients that travel into those reservoirs,” he said.
Plakke also says that the nutrients that travel to and gather in these reservoirs can be from weather events like fires.
“Nutrients can be released into the water streams and are transported downward all the way out to the oceans. These nutrients can collect in certain areas and increase the chances of an algae bloom,” he said.
These blooms are a common occurrence and come around every year.
Denver Water says it is currently using water from different reservoirs. They also said it can remove the algae, but the residuals can still affect taste and smell.
Plakke also says that they do have solutions, which include blending reservoir water with mountain sources to dilute it and adding powdered activated carbon that helps neutralize the taste. Both processes take some time.
If you’re wondering if geosmin is affecting your water, the taste is commonly described at straw-like or grassy. Plakke said that for him, it tastes like water out of a hose.
Denver Water said stale tasting water is a sign there may not be enough disinfectant. For homeowners, flushing water lines can help remove stagnate water, as well as filters on your tap.
Councilman Kevin Flynn said in a Facebook post that the taste and smell should return to normal within the next week or two.