Taste and Odor in Drinking Water 

Geosmin and MIB 

Geosmin and Methyl-Isoborneol (MIB) are naturally occurring compounds that have a  earthy/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 levels of geosmin or MIB increase in their water supply. Geosmin and MIB are some of the most difficult compounds to remove during water treatment. 

The Cobb County-Marietta Water Authority (CCMWA) routinely monitors for geosmin and MIB in the drinking water supply. Additionally, CCMWA conducts monthly testing at seven sample sites on Lake Allatoona upstream of the intake for the treatment plant. Proactive sampling allows the Authority to be aware and provide additional treatment steps when we notice an increase in geosmin and MIB levels. Beginning in late spring and through late fall, during the time of year that the compounds are typically at higher levels, CCMWA tests for geosmin and MIB on a weekly basis.  

Generally, geosmin & MIB become a taste & odor issue for customers when levels are in the range of .01 nanograms per liter (ng/L, or 10 parts per trillion), but some people who are particularly sensitive may notice it at levels above .005 ng/l. To put it in simpler terms, that would equate to one-half of one cent  in a billion dollars.  

What are the Effects of Geosmin and MIB?  

Geosmin and MIB produce a musty, earthy smell and taste in drinking water, however both compounds are not harmful at levels present in drinking water.  

What Causes Increased Levels of Geosmin and MIB?  

Some kinds of algae and bacteria present in lake and reservoir water naturally produce geosmin and MIB. An increase in this production typically happens during late summer into early fall when lake levels are low and water temperatures are warm.  

What Can be Done About Geosmin and MIB?  

Geosmin and MIB cannot be removed from water using normal treatment processes; advanced treatment is required. During increased levels of geosmin or MIB, before source water enters our treatment facilities, Powdered Activated Carbon is added to reduce geosmin and MIB. Prior to the water being pumped into the distribution system from our Wyckoff Water Treatment facility, a portion of the treated water is further treated at our Granular Activated Carbon facility to further remove Geosmin and MIB compounds from the water.  

Can I do anything to my water taste better?  

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