Geosmin and Methylisoborneol (MIB) are harmless, naturally occurring compounds produced by bacteria in soil and algae found in surface water (lakes, rivers, streams, dams). They can produce an earthy, musty-type odor/taste, like that of overturned rich soils, and are present in foods such as beets, spinach, and mushrooms. Geosmin and MIB are NOT the result of pollution or contamination of our source waters and is not a result of a failure of treatment processes. It occurs through a natural process.
Frequently Asked Questions
Why Does the Drinking Water Have a Different Taste and Smell?
The change in taste and smell is caused by non-harmful byproducts of a naturally occurring algae in our source water called geosmin and MIB. Recent changes in source water quality, through natural processes combined with warm summer temperatures can promote algal growth, which can lead to the production of geosmin/MIB compounds. Communities whose water supply depends on surface water, like Pittsburgh, can periodically experience episodes of unpleasant tasting water when a sharp drop in the population of these bacteria releases geosmin/MIB into the water.
Is the Water Quality Effected?
Pittsburgh’s drinking water is safe and continues to meet or exceed all federal and state water quality standards. While the taste and odor can be unpleasant to some individuals, geosmin/MIB is not harmful. The taste and odor that results from geosmin/MIB is a palatability issue, not a health concern. On-going testing continues to show an absence of harmful bacteria and other pathogens in the water.
How Long Will the Taste and Odor Last?
It is not possible to predict the onset of an incidence of geosmin/MIB, or how long it will last. Since geosmin/MIB are naturally occurring, they will diminish in the water supply with time and weather changes. The temporary change is anticipated to last days to weeks but could last longer depending on surface water temperatures and the weather.
Why Do We Smell It?
The human nose is extremely sensitive to geosmin/MIB compounds. If you poured a teaspoon of geosmin into the equivalent of 200 Olympic-sized swimming pools, you would still be able to smell it. Heating the water increases the volatility of these compounds, which explains why the smell is more easily detected when you are in the shower or when used for hot beverages.
The general threshold for human detection of geosmin is about 15 nanograms per liter (15 nanograms per liter = 15 parts per trillion). However, some people can detect geosmin in drinking water at concentrations as low as 5 nanograms per liter. This explains why some residents notice the taste and odor, while others do not.
Can It Be Removed from the Drinking Water?
Geosmin/MIB is not removed by conventional water treatment processes like those used by Pittsburgh Water at the water treatment plant. Pittsburgh Water may implement an additional treatment process such as Powdered Activated Carbon (PAC) to remove these compounds when detected in the river water, but this treatment is not effective for geosim/MIB in the distribution system.
In your home water system, the following can reduce or remove taste and odors for sensitive individuals:
- Use a carbon filter at the tap or in a water pitcher. While the filter may not eliminate the taste entirely, using one can improve the palatability of the water.
- Cool or chill water in the refrigerator to improve taste and reduce odors.
- Add lemon to water when drinking.