Water Quality-Lake Weatherford
Taste and Odor-Frequently Asked QuestionsSeveral customers have recently reported an earthy taste and odor in Weatherford's water supply. The taste and odor that customers are experiencing is a result of a naturally occurring algal bloom that is very common in lakes, and typically happens twice per year- a summer algal bloom and then a winter algal bloom. Algal blooms can occur anytime there are sufficient nutrients in the water, but particularly whenever warm water and calm weather conditions exist.
What causes the taste and odor changes?
During an algal bloom, two natural organic compounds are produced- MIB (methylisoborneol) is produced during the algae's life cycle, and then when the algae dies off it releases geosmin. Both MIB and geosmin cause an earthy taste and odor in the water, and both of these can be detected by people at very low concentrations.
Summer Algal Blooms
In Lake Weatherford, the summer bloom usually occurs in late-July or August when high temperatures warm the reservoirs, little or no rainfall has occurred, and sunlight penetrates the water allowing photosynthesis to occur. When these conditions are present, the blue green algae species Nostoc and Anabaena will reproduce or "bloom."
Winter Algal Blooms
A winter algal bloom can also create taste and odor changes in the water supply during cooler weather patterns. When winter algal blooms occur, an earthy or metallic taste and/or odor might be noticeable in the water supply. The highest levels of geosmin can usually be detected in January or February, commonly after colder temperatures cause the algae to start to die off.
The City's primary water supply is Lake Weahterford. However, during times of drought, the City also pumps water from Benbrook Lake into Lake Weatherford as an additional source of water supply. Because different lakes have their own unique water qualities, customers may be able to detect a difference in taste when the City changes from one source to another.
Is the water safe to drink?
Yes, the water is safe to use with no health risks. The taste and odor that results from geosmin and MIB is a palatability issue and although it may be unpleasant, it is not a health concern.
What are Weatherford's sources of water supply?
How long will the taste and odor last?
It is impossible to predict the onset of an algal bloom, or how long it will last. Algal blooms have been detected in Lake Weatherford that remain in the lake throughout the year at varying levels. The highest levels of geosmin are typically detected in January and February, although we see sometimes see spikes in July and August. Although there is a usually a small amount of geosmin in the water year-round, very high levels of geosmin usually only last for a couple of weeks before dissipating naturally.
The City of Weatherford regularly tests the water supply sources for various water quality parameters. Since mid-July, the geosmin level in Lake Weatherford was 92 nanograms per liter. 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.
To make the water taste better, try chilling it, adding ice cubes, a slice of lemon, or a few drops of lemon juice.
Can the taste and odor be reduced at the tap?
During an algal bloom, laboratory analysis of raw water samples can show high levels of geosmin. Unfortunately, since these types of events are beyond our control, utilizing current treatment processes, such as oxidation (diffusers) and injecting taste and odor measures (i.e. chlorine dioxide, Earthtec (copper sulfate), and sodium permaganate), can reduce but not eliminate the taste and odor that we are currently experiencing.
Can it be removed from the drinking water?
The City of Weatherford Water Utilities will continue to analyze the potential causes of taste and odor episodes, the source of heightened levels of geosmin, and additional methods to address the issue.