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Increase in organic growth affects water taste, order but still safe to drink

Thursday, December 28 2017 2:42 PM

The Trinity River Authority, the City of Colleyville’s water treatment partner, notified the City that the raw water supply has experienced an increase in natural occurring organic growth, geosmin. This results in some undesirable taste and an “earthy” odor in the treated water. Geosmin is not toxic or harmful. The water remains safe for consumption and it is simply the aesthetic quality of the water that is affected. TRA is employing additional steps in the treatment process to address the taste and order concerns.

The City performs routine testing throughout the City’s water system to confirm the safety of the water supply.

Frequently Asked Questions
What is causing the taste and odor experienced by some customers served by the Colleyville water supply?
The City of Colleyville receives treated water from the Tarrant County Water Supply Project, which is owned and operated by the Trinity River Authority (TRA). The raw water supply is Lake Arlington, which is operated by the Tarrant Regional Water District (TRWD). Test results from Tarrant Regional Water District over recent weeks are showing an increase in the geosmin levels in Lake Arlington. Geosmin, even at low levels, can be detected by the average person.

What is geosmin?
Geosmin is a naturally occurring compound produced by bacteria in soil and algae found in surface water. Cold temperatures kill off algae in surface water, and the dead algae release the geosmin.

Where is the odor and taste occurring?
Because of the elevated geosmin levels in the raw water supply, residents of Colleyville (as well as all other customer cities of TRA) may experience a presence of the described "earthy" taste and odor in the drinking water.

Is the water quality affected?
While the taste and odor can be noticeable, geosmin is not toxic or harmful. The water remains safe to drink. 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 impossible to predict the onset of an incidence of geosmin, or how long it will last. Geosmin compounds have been detected in TRWD lakes and remain in lakes throughout the year at varying levels. The highest levels are typically detected in January and February. Tarrant Regional Water District regularly tests the water supply sources for various water quality parameters. To put this in context, the general threshold for human detection is about 15 nanograms per liter; however, people with sensitive pallets can detect geosmin in drinking water at concentrations as low as 5 nanograms per liter. This is why some customers notice the taste and odor while others do not.

Can the taste and odor be reduced at the tap?
To make the water taste better, try chilling it, adding ice cubes, a slice of lemon, or a few drops of lemon juice.

What does it smell like?
Geosmin typically produces an earthy or musty odor as is found in the odor of overturned rich soils, and is present in some foods such as beets, spinach, and mushrooms.

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City of Colleyville | 100 Main Street, Colleyville, Texas 76034 | 817-503-1000 | Contact the city