Geosmin and 2- MIB
Geosmin is a naturally occurring organic compound produced by bacteria in soil, algae found in surface water, and a variety of other organisms. Geosmin has a very distinct earthy flavor and aroma and is responsible for the earthy taste of beets, spinach, and mushrooms. Geosmin is a contributor to the strong scent in the air when it has rained after a prolonged dry spell or when soil is disturbed. Geosmin is responsible for many taste and odor complaints in drinking water. Most people can detect Geosmin in water at levels as low as 15 parts per trillion (ng/L), with sensitive individuals detecting it as low as 4 parts per trillion (ng/L). Chemically it is a bicyclic alcohol with a formula of C12H22O.
2-Methylisoborneol (MIB) is an organic chemical with strong odor. The odor detection threshold is very low and this chemical can have major influences on water quality aesthetics. Various strains of algae, particularly blue-green algae (such as Anabaena) produce 2-MIB along with other odorous compounds such as Geosmin. This gives a musty or earthy odor that can be quite strong if an algal bloom is present. Subsequent death of the algae will also release any 2-MIB or Geosmin that is trapped in the cells. These compounds are detectable by the average person at very low levels, in the part per trillion range, and are responsible for many taste and odor issues in drinking water treatment and distribution.
Samples submitted to our contract laboratories confirm the presence of Geosmin, a naturally occurring compound, in our water supply reservoir at a concentration of 50 part per trillion. While the taste and odor are unpleasant, Geosmin is not toxic or harmful to your health, and the water remains safe to consume.
Geosmin is a naturally occurring compound produced by bacteria in soils and algae found in surface waters. Geosmin produces the odor of overturned rich soils and is present in foods such as beets, spinach, and mushrooms. Along with MIB, Geosmin is an organic molecule found in surface waters produced by blue-green algae. Bright sun, warm temperatures, and nutrients combine to create the ideal growing conditions for the algae. The compounds are produced inside the algal cells and are released when the algae die.
Apart from sunlight and higher summer temperatures, all algae require nutrients to grow. The area surrounding St Charles Mesa Water District is a highly agricultural area, the intense rains that have intermittently happened over the last few weeks have caused a lot of nutrients to be deposited in the reservoir that supplies the District.
While the taste and odor can be very unpleasant, Geosmin and MIB are not toxic or harmful and the water remains safe to drink.
Ongoing testing continues to demonstrate an absence of harmful bacteria or other pathogens in the water.
There are reports of an earthy/musty type of taste and odor coming from a variety of areas served by St Charles Mesa Water. Complaints have been reported primarily from the central portion of the service area.
It is impossible to predict the onset of an incidence of Geosmin, or how long it will last. Geosmin compounds have been shown to remain in lakes and reservoirs for days to months.
St Charles Mesa Water District regularly tests our water supply sources for various water quality standards, including Geosmin. 2021 sampling analysis test results for Geosmin were below detection level through June, in July the measured result was 51 ng/L (nanograms per liter) or 51 Parts per Trillion.
For perspective, a typical person can sense Geosmin at levels around 15 parts per trillion, and a sensitive person can detect as low as 4 parts per trillion. This is why some of our customers detect it, while others do not.
A part per trillion is equal to:
1 ounce in 7.5 billion gallons of water
1 square inch in 250 square miles
1 second in 32,000 years
To make your water taste better, try chilling it, adding ice cubes, a slice of lemon, or a few drops of lemon juice. Hot water use will intensify the taste and odors associated with Geosmin, thus showering, clothes washing, and coffee makers will increase the offending tastes or odors.
Geosmin typically creates a musty or earthy smell similar to the odor of overturned rich soils, and is present in some foods such as beets, spinach, and mushrooms.
The human nose is extremely sensitive to Geosmin. If a teaspoon of Geosmin was poured into the equivalent of 200 Olympic sized swimming pools, the odor would still be detectable.
The general threshold for human detection is 15 parts per trillion, and for sensitive people as low as 4 parts per trillion.
Heating the water will increase the volatility of this compound, which explains why it is more easily detected in the shower or when used to make hot beverages.
Geosmin cannot be removed from water using conventional treatment techniques. Ozone, Advanced Oxidation processes, biofiltration, as well as Powdered Activated Carbon (PAC) and Granular Activated Carbon have proven to be effective at reducing Geosmin levels.
St Charles Mesa Water District uses a PAC system in its treatment process, and dosages are being adjusted to optimize the usage of PAC as a treatment process for controlling and reducing Geosmin currently.
Geosmin and MIB are common in many jurisdictions across The United States, Canada, and elsewhere in the world. Locally, in Colorado, there are many water systems facing the same issues St Charles Mesa with regards to Geosmin.
Yes. While the tastes and odors associated with Geosmin are unpleasant they are only aesthetic properties. The water is still safe to use and consume. St Charles Mesa is ensuring that the water being distributed to all of our customers meet the primary drinking water standards and regulations expected by the Colorado Department of Health and Environment