Although water coming from Gahanna taps might have a bad taste and smell, it's safe to drink.
Gahanna service director Dottie Franey emphasized to Gahanna City Council on Jan. 13 that the water is safe to consume.
"We have that from two EPA sources," she said. "We contacted the EPA. They're involved in it. The city of Columbus had a meeting on Friday (Jan. 10) to talk about this. They also confirmed the EPA has been involved."
Since early November, Franey said, numerous people have detected an earthy odor and taste in the water supply.
Gahanna purchases water from Columbus that's treated at the Hap Cremean water plant on Morse Road. That plant supplies water to about half of Columbus' 1.1 million customers and covers most of the Columbus service area north of Interstate 70, with the exception of Hilliard.
Hap Cremean is supplied mostly by Hoover Reservoir and supplemented by Alum Creek Reservoir.
Seventy percent of Hoover's runoff is from agricultural land, Franey said.
Nutrients from the runoff -- mainly nitrates and phosphorus -- allow algae to bloom and grow in the water, she said. The type of algae and characteristics of the bloom depend on the nitrate/phosphorus ratio.
"The other thing Columbus wanted to make clear is algae are always present in water," Franey said. "The type that's there now doesn't produce toxins."
The current algae bloom is called anabaena, which includes organic compounds geosmin and methylisoborneol. Those compounds cause the smell and taste people have detected in the water, she said.
Franey said Columbus is adjusting the gates at Hoover to draw from the water levels that are least affected by the algae bloom.
"They're increasing the amount of powdered activated carbon, adjusting the PH (acidity levels) and increasing the chlorination," she said. "That's what I notice. It smells like a swimming pool."
Franey said it's costing Columbus $10,000 a day to treat the water.
Columbus estimates a 60-percent taste and odor removal rate is being achieved thus far.
The components that cause the taste and smell could be detected at 5 to 10 parts per trillion (ppt), Franey said.
She said geosmin peaked at 150 ppt and is now at 50 ppt. Methylisoborneol peaked at 300 ppt and is now at 5 ppt, she said.
By 2016, Franey said, upgrades are expected to be completed at Hap Cremean that include the use of ozone and biological filters to treat algae.
Council member Michael Schnetzer asked what led to the current problem with the water.
"Temperatures can play a part," Franey said. "Although we had a cold snap, we haven't had a long freeze. That would kill all algae underneath."
Deputy service director Matt Holdren said the latest incident has been attributed to the warmer weather.
"The cold helps the algae to not bloom," he said.
Updates about the water issue are posted online at publicutilities.columbus.gov and on Facebook under Columbus Public Utilities.
Residents also may call the Water Quality Assurance Lab at 614-645-7691 between 8 a.m. and 4 p.m. Mondays through Fridays.