A blue-green algae bloom in Lake Austin may cause a fishy or musty taste and odor in the water supply in the coming weeks. Although the algae is not harmful, Austin Water Utility is taking steps to prevent consumers from noticing the changes in their water supply.

“The algae is very unpredictable,” said utility representative Kevin Buchman. “We see it as often as once a year to as infrequently as every two to three years.”


photo by Michael Baldon

The taste is not caused by the live algae but by compounds released when it dies, Buchman said. Standard tests conducted by Austin Water show higher levels of algae in the water supply toward the end of the summer. In an effort to stave off the unfamiliar taste, Austin Water has started an active charcoal treatment in addition to its normal treatment processes at city water plants.

“We could tell by our sampling that we were seeing an effect of the bloom, so we decided to take a proactive approach and start the charcoal treatment,” Buchman said.

Adding a simple active carbon compound to water as it is being treated helps absorb the parts of the algae that cause a change in the water’s features.

These kinds of blooms are normal and usually die back under natural circumstances, said Bonnie O’Neil, an assistant research scientist at UT’s Culture Collection of Algae.

“They go in cycles, so depending on the light and temperature there may be a bloom,” O’Neil said. “It basically just takes up space that other organisms could be living in. It’s like a fast-forward version of any organism in the ecosystem. It builds that niche and then dominates for a brief time.”

O’Neil said something like the growth of other plants or a change in temperature usually causes the algal bloom to die out.

Stephen Peña, a member of the culture collection staff, said consumers should not be concerned about drinking tap water, since the charcoal treatment has been proven to effectively deal with the results of algal blooms like this one.

“Tap water is treated before it’s used, so there’s not much of a chance of there being a problem,” Peña said. “Few blue-green algae are toxic. They usually just cause a fishy taste.”

Austin Water will continue the charcoal treatment until algae levels return to normal. The process is the most common method for dealing with natural situations that impact the flavor and smell of water.