Nitrate Advisory Continues For Columbus Tap Water
The water advisory issued by the city of Columbus remains in effect. It warns that pregnant women and infants younger than six months should not drink city tap water because it contains nitrates above allowable limits.
Update on Monday, June 22, 2015 at 2:10 p.m., the advisory has been lifted by the City of Columbus. The original story about the advisory is below.
WOSU’s Sam Hendren reports on the origins of the contamination and how the city produces its drinking water.
It’s one of the most picturesque spots in Central Ohio; water plunging down a rock ledge 30 feet into a pool at Hayden Falls Park just west of the Scioto River. Below the falls, the water flows into Griggs Reservoir then moves downstream in the Scioto toward intake valves at Columbus’ Dublin Road Water Treatment plant. Rod Dunn, head of the Water Quality Assurance Lab, explains how river water becomes city drinking water.
“The water is brought in from the river and it’s screened to remove any of the leaves and sticks,” Dunn says. “Then it goes into what we call alum coagulation where we use aluminum sulfate to pull out the mud and the silt. Then it goes through lime softening where we use lime to raise the ph and it precipitates all the calcium carbonate and that’s what causes the hardness of the water. We add carbon dioxide to bring the ph back down. And goes through sand and gravel filters. And then we add chlorine to kill the bacteria. Then it goes into large holding tanks to give the chlorine time to kill the bacteria and disinfect the water.”
From there that water is pumped to elevated storage tanks and eventually to customers.
Nitrates are inorganic compounds that can be found in lettuce, spinach, celery, and in processed meats like hot dogs and salami.
How did nitrates get into the city water supply? The Scioto River watershed is an area of about a thousand square miles. It stretches north and northwestward to Marion, Kenton and Bellefontaine. 80 percent of that region is agricultural. Dunn says farmers applied fertilizers just before a particularly heavy rain.
“We had a really dry May so it let all the farmers get into the field at one time. We didn’t have any rain events in the middle of May to wash off a little bit of the nitrates at a time. So when we saw the high intensity thunderstorms at the end of May it kind of washed it all off at one time,” Dunn says.
So instead of soaking into the soil, the rainwater laced with nitrates ran into streams that feed the Scioto and supply much of the water for the western portion of Columbus.
The city has two other water treatment plants. One treats water from Hoover Reservoir. The other treats water from an underground aquifer. Neither of those plants has elevated nitrate levels. But water from the Dublin Road plant continues to slightly exceed the EPA’s maximum level: 10 milligrams per liter.
Officials anticipate that the heavy rains that occurred Friday and Saturday will wash a lot of the remaining nitrates downstream past Columbus. But they’re still not certain when the advisory will be lifted.
Columbus is spending $35 million on an ion exchange system that will remove nitrates from drinking water but the system won’t be operational for another two years.
You can find a map of affected neighborhoods on the city of Columbus’ website.