City says MIB found in water, leading to taste and odor complaints

After receiving complaints about an unusual taste and odor in Laredo’s water supply, the Laredo Utilities Department said Friday that laboratory results point to conditions in the Rio Grande as the source.

Samples collected from raw Rio Grande water entering the city’s treatment plants contained 2-methylisoborneol, or MIB, a naturally occurring organic compound associated with earthy or musty tastes and odors.

According to the U.S. Geological Survey, MIB can be produced by cyanobacteria and certain filamentous bacteria found in soil and water.

“This confirms that the compound entered the system with the Rio Grande water,” the Utilities Department said. “Summer heat and seasonal changes in natural organic material in the river can contribute to these conditions.”

The department emphasized that the compound affects the water’s taste and smell but does not make it unsafe to drink.

“Most importantly, Laredo’s water remains safe to drink,” the department said. “MIB is a taste-and-odor (aesthetic) issue and does not make the water unsafe.”

The taste and odor are expected to gradually lessen as conditions in the Rio Grande improve. However, some neighborhoods may notice them longer because treated water moves through storage tanks and water lines before reaching homes.

The department said ongoing monitoring shows Laredo’s water continues to meet applicable Texas Commission on Environmental Quality and U.S. Environmental Protection Agency drinking-water requirements.

“Our experienced operators, laboratory staff and engineers continue to monitor the river and adjust treatment as needed,” the department said.

The city is also evaluating design options for activated-carbon treatment and other plant upgrades that could help manage similar seasonal taste-and-odor events in the future.