Taste and Odor in Drinking Water

August 18, 2016

City of Houston 

Department of Public Works and Engineering

Public Utilities Division – Drinking Water Operations

What is in the water that has caused the recent change in taste or odor?

We have detected increased levels of geosmin and MIB in our untreated surface water supplies and these substances are known to produce earthy or musty taste or odor in drinking water.  Geosmin and MIB (2-methyl isoborneol) are naturally-occurring compounds sometimes produced by seasonal algae blooms.  The substances are detectable by the human nose even at very low concentrations.  

According to the Water Research Foundation, “There are hundreds of types of algae, but only a few produce chemicals that make water taste or smell unpleasant. When algae die, they release compounds. Two of the more troublesome by-products are MIB and geosmin. Both produce an earthy/musty taste. MIB mimics the smell of fresh dirt; geosmin is the compound that gives beets an earthy odor. Neither is harmful to people.” (AWWA Water Research Foundation, 2006)

What is the City of Houston doing to remedy the issue?

Since MIB and geosmin are naturally-occurring, they will naturally diminish in the upstream water supply with time and weather changes.  

How are you monitoring the situation?

We are taking additional water samples to better understand and track the levels of these substances, as well as maintaining our standard program of sampling and testing to assure that our drinking water is safe.

What if it does not naturally clear from the system?

Conventional water treatment is ineffective for removal of geosmin and MIB.  Treatments such as powdered activated carbon (PAC), ozonation and biofiltration have been effective for removal of these compounds.  However, the City of Houston system does not have treatment technologies that effectively reduce these taste and odor causing issues.


What can I do at home?

According to the Water Research Foundation, water is safe to drink when MIB and geosmin are present, but it may be unappealing when there are taste and odor problems. You can improve the taste and odor by refrigerating a pitcher of tap water. Additionally, standard home water filtration systems that contain carbon should mitigate the taste and odor of these substances.

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