Geosmin and 2-Methylisoborneol (MIB)

Geosmin and 2-Methylisoborneol (MIB) are naturally occurring compounds that have an earthy/musty taste and odor. Some kinds of algae present in our source waters naturally produce geosmin and MIB. An increase in this production typically happens during the summer. When this algae grows and multiply in the water supply, they excrete small amounts of harmless chemicals, geosmin and MIB, into the water that cause the musty taste and odor.

Geosmin and MIB do not pose a public health risk, but their presence can cause concern about the quality of drinking water. Utilities around the country may receive high numbers of customer complaints whenever a geosmin or MIB outbreak occurs in their water supply. Although these chemicals are harmless, the human senses of taste and smell are extremely sensitive to them and can detect them in the water at concentrations as low as five parts per trillion (nanograms per liter).

Columbia Water routinely monitors for geosmin and MIB in the drinking water supply. Activated carbon is effective in reducing taste and odor issues, and Columbia Water adds it to the treatment process when geosmin and MIB are detected in source waters at elevated levels. Columbia Water has also taken additional steps to improve the treatment process by modifying the carbon feed system piping at the Lake Murray Treatment Plant to accommodate simultaneous feeds at multiple injection points. This allows plant operators to more effectively add it to the treatment process. Operating staff also perform daily threshold odor tests to attempt to detect unusual scents at various treatment stages in the plant. If any unpleasant odors are detected in the filtered or finished water, the carbon dosage can be changed quickly to remove additional by-products that may be entering the plant.

When geosmin and MIB are noticeable, customers can add lemon juice and chill water in the refrigerator to improve the taste and reduce odors.