Geosmin and Methyl-Isoborneol (MIB) are naturally occurring compounds in surface water systems such as lakes and rivers. The compounds produce a very strong, earthy or moldy taste and odor. In fact, Geosmin provides the characteristic earthy flavor in red beets and may be found in other fruits and vegetables providing a musty flavor. Geosmin can be detected by humans as low as 10 nanograms per liter. A nanogram is one millionth of a milligram. Or in other words, as small as one cent of ten billion dollars. These compounds are usually associated with aquatic plants in lakes and reservoirs during certain times of the year. The compounds can sometimes pass through a water treatment plant and become noticeable.
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Seasonal environmental conditions including, but not limited to, rain, drought, temperature and growth of aquatic plants in the water source can contribute to changes in taste and odor in the drinking water. Geosmin and Methyl-Isoborneol (MIB) are common reasons that contribute to an earthy taste and odor.
Geosmin and MIB produce a musty, earthy smell and taste in drinking water. Both compounds are not harmful at levels present in drinking water.
Some kinds of algae and bacteria present in lake and river water naturally produce Geosmin and MIB. An increase in this production typically happens during late spring to early fall when water temperatures are warm.
Geosmin and MIB are removed during the water treatment process but at times may still be noticeable. Water treatment facilities that provide water to Chesterfield County employ activated carbon that is effective in reducing Geosmin and MIB levels. Adjustments to treatment systems are done but sometimes Geosmin and MIB may still remain noticeable in the water system for several days to weeks.
While the drinking water can be aesthetically unpleasing, the water is safe to drink. This is a harmless and temporary condition which can affect a surface water system at any time.
The water treatment facilities that provide drinking water the Chesterfield County perform multiple tests on a regular basis. Such tests range from monitoring the quality of water in lake and river water sources to testing treated drinking water leaving the plant and arriving to a customer’s location. When a taste or odor issue is detected by the treatment plant or reported by customers, adjustments to plant treatment such as adding more activated carbon and optimizing filtration processes occurs along with additional testing. The county’s Department of Utilities also sends crews out to flush areas where customers report a taste and odor issue. Line flushes help to remove older water in the lines and replace with fresher tasting water.
Optimizing the treatment process at a water plant to remove taste and odor compounds can take several days or longer due to multiple factors. Such factors include the type and amount of odor or taste compound present, the amount of water being treated and adjusting water treatment chemical additives to remove the taste and odor compounds. In addition, it can take a week or longer for the now optimized treated water to work through the miles of pipes connecting the water plant to our customers.
Customers can fill a pitcher or similar container with tap water and add some lemon juice (2-3 drops per 8-ounce glass) and chill the water in the refrigerator. The lemon juice and colder temperatures helps to balance out the taste and odor. In addition, using a drinking water filter that contains activated carbon can reduce odors and improve the taste.
If you have further questions or concerns about the quality of your water, contact the Chesterfield County Utilities Laboratory at 804-748-1310, option 2.