Some students living off-campus can thank algae and heavy rainfall for their possibly odorous and odd-tasting tap water this week.

The culprits are anabaena algae, which accumulated on the surface of the Hoover Reservoir before spilling over the dam due to rising water levels caused by the recent increase in rainfall. The blue-green algae then made their way down Big Walnut Creek toward the Hap Cremean Water Plant intake.

Affected areas include parts of Columbus receiving water from Hap Cremean, which provides drinking water to some areas north of Interstate 70, including parts of Ohio State campus and some off-campus neighborhoods.

George Zonders, a spokesman for the Columbus Department of Public Utilities, said that although the drinking water in some areas may be undesirable to the senses, it does not pose a health risk.

“While it may taste or smell a bit off, it’s completely not a health issue,” he said. “If it were, we would definitely let you know about it.”

The odor and taste, which Zonders said could be considered comparable to that of pond water, is the result of a compound released by dead algae during the disinfection stage of the water treatment process.

Although anabaena has the ability to produce a harmful toxin, that toxin was not detected after tests were performed by the city, Zonders said.

He said it is difficult to pinpoint how long it will take for any odor or taste to fully dissipate, but expects the contamination to work its way out of the system soon.

The city received about 100 complaints or inquiries this week, with just two calls concerning water taste or odor on Friday, Zonders said.

Taste and odor issues from the dead blue-green algae can be detected by some individuals consuming water contaminated in the single digit parts-per-trillion range.

Zonders said he believed the Hap Cremean anabaena contamination that occurred in December 2013 measured closer to 50 parts-per-trillion.

The current water treatment process essentially consists of three stages. First, powdered, activated carbon absorbs compounds left by dead algae. Then, the algae are gathered after coagulating and settling at the bottom of the tank. Finally, the water is disinfected with chlorine and filtered.

Hap Cremean is currently in the process of upgrading its facilities, which will include a “biologically active filtration,” creating an additional treatment barrier, Zonders said, adding he expects the filtration to be implemented next year.

“Having quality water kind of seems like a joke, if it’s stinky or kind of tastes bad, so we’re doing everything we can to address this now and in the future,” he said.