Ion-Exchange Facility Seen As Solution To Columbus Nitrate Woes

High nitrate levels in the tap water in Ohio’s capital city triggered a warning for pregnant women and babies late last month.

Columbus officials lifted the warning, The Columbus Dispatch reported this week. Fertilizer and pollution runoff from north of the city are to blame, critics said in the report.

“In the affected area, women who were more than 30 weeks pregnant and infants younger than 6 months were advised not to drink tap water or consume it in infant formula, juice or cereal. High nitrate levels can be deadly for babies, causing symptoms including shortness of breath and blue coloring of the skin. More recent testing showed the levels had fallen,” the report said.

The city is upgrading its treatment infrastructure to prevent such advisories, according to The Dispatch. A $35 million ion-exchange facility is underway.

“The new building contains about a dozen tanks that [a city official] said function similar to water softeners, removing nitrates from millions of gallons of water a day. Construction is scheduled to wrap up by the end of 2017,” the report said.

The U.S. EPA characterizes ion exchange as a reversible chemical reaction designed to remove dissolved ions, according to the agency’s drinking water treatability database. The process is effective at treating nitrates as well as contaminants such as arsenic.

The technique does not come without its complexities, the EPA explains:

One of the primary concerns related to [ion-exchange treatment] is the phenomenon known as chromatographic peaking, which can cause [arsenic] and nitrate levels in the treatment effluent to exceed those in the influent stream. This can occur if sulfate are present in the raw water and the bed is operated past exhaustion. Because sulfate is preferentially exchanged, incoming sulfate anions may displace previously sorbed [arsenic] and nitrate.

That makes the level of sulfate a critical factor in the treatment process.

For similar stories visit Water Online’s Nutrient Removal Solutions Center.