City of Napa residents might have noticed earthy, musty or moldy tastes and smells in their water this past week.
The city of Napa draws the bulk of its local water supply from Lake Hennessey.
Algae Responsible for Potentially Strange Odors and Tastes in Water as City of Napa Switches to Lake Hennessey as Primary Water Source
Sep 18, 2021 at 11:35am
The water is still perfectly safe to drink, despite the potential for olfactory or gustatory unpleasantness, officials say.
Algae is the culprit behind the changes in taste and odor, said Joy Eldredge, the city’s deputy utilities director. With warmth and sunlight, algae blooms seasonally upon Lake Hennessey. The algae, when they die, release odor compounds. And, though algae is removed during water treatment, those odors can stick around.
Residual bits of algae are potentially detectable through taste or smell because the city of Napa switched to Lake Hennessy as its primary source of water on Sept. 12. Algae compounds weren’t previously detectable because the city was using water drawn from the Sacramento–San Joaquin River Delta through the State Water Project, Eldredge said.
The city does apply PAK 27 algaecide to the lake, an oxygenator that quickly breaks down the compounds of the algae. Without using the algaecide, the lake would see exponentially more algae and residents would detect a much greater change in taste and odor, according to Eldredge.
“It’s so challenging because it’s two or three parts per trillion that are noted,” Eldredge said. “Even though the algae is removed in our treatment process, if there’s any residual compound in there, it’s detectable.”
Continue reading the article from Napa Valley Register here.