Keep It Clean

    Hoover Crop  

Simple steps you can take at home to  prevent water pollution .

Take a Tour

Watershed Signage

Signage installed at Griggs, O'Shaughnessy & Hoover Reservoirs invites park visitors to  take a self-guided tour along the shoreline & learn about the green infrastructure installed there.

Rain gardens, porous pavement & more can improve the quality of storm water entering the reservoirs that supply our drinking water.

Non-point Source Pollution

Stormwater Runoff

Protect our Waterways
Illustration Courtesy of NCDENR

Elevated Nitrate Levels

Nitrate in Drinking Water

Visit our new Nitrate FAQs page.

In the rare event the Columbus Division of Water notifies the public about elevated nitrate levels in drinking water, many customers want to know:

Nitrate in drinking waterWhat causes elevated nitrate in drinking water?
Nitrogen occurs naturally and is essential for plant growth. That is why it is applied as fertilizer to farmland, lawns, and golf courses. During certain weather conditions, especially after heavy rains, nitrate can run off into streams and rivers where it reacts with water to form nitrate.

The Scioto River receives runoff from more than 1,000 square miles of land, 80% of which is agricultural, before reaching the Dublin Road Water Plant intake. Therefore, it is more susceptible to nitrogen runoff than the other water sources in Columbus.

How were acceptable nitrate levels established by EPA?
The acceptable level for nitrate in drinking water was established by the Environmental Protection Agency (EPA) as a safeguard to protect infants. Because of their immature digestive system, infants under six months of age cannot properly digest nitrates which interferes with the oxygen carrying capability of their blood. Therefore, the EPA established the “maximum contaminant level” for nitrate in drinking water at 10 milligrams per liter or 10 parts per million.

Who is affected . . .  who is not?
Levels of nitrate in Columbus drinking water pose no threat to the majority of people. Only infants less than six months of age are affected when the level of nitrate is above the standard. Pregnant or nursing women, or anyone with medical conditions, should consult with their doctor about limiting nitrate consumption. Many vegetables and processed meats contain nitrates. Water is generally a minor source of nitrate in the diet.

Why and how is the public notified?
Water suppliers are required to notify the public when nitrate levels are more than 10 parts per million in the drinking water. On rare occasions, the water from the Dublin Road Water Plant exceeds this standard. The Columbus Division of Water’s Water Quality Assurance Laboratory routinely tests surface water samples and determines when nitrate levels are rising.

A “Nitrate Advisory” is sent to newspapers, TV and radio stations and placed on our home page as the top feature and placed in our Document Library in the current year's "News Releases" section when the nitrate level exceeds 10 parts per million. Through the media, parents of infants are notified of the specific area impacted and are advised to buy bottled water for the baby’s needs until the advisory is lifted.  

Historically, only the Dublin Road plant has ever been affected by elevated levels of nitrate - an infrequent occurrence which tends to be limited to April through July. Water supplied to the rest of our system by the Parsons Avenue and the Hap Cremean water treatment plants does not experience elevated nitrate levels. 

To reduce the health risk to infants the City of Columbus recently added a treatment process, called anion exchange, to the Dublin Road Water Plant to remove nitrate. Anion exchange works like a giant water softener and pulls nitrate from the water as it flows through a bed of resin beads. Extensive water quality testing in the watershed upstream of the water plant by the Water Quality Assurance Laboratory helps to determine when we need to turn on the anion exchange system. Then additional water quality testing of the finished drinking water confirms that the nitrate level has been reduced below 10 ppm and is safe for infants. With this added treatment system in place, elevated nitrate is expected to be a thing of the past.

The Dublin Road Water Treatment Plant supplies water to ( see Distribution Map):  

Downtown Columbus  German Village
Upper Arlington  Grove City (portions)
West Columbus  Grandview
SW Columbus (to Scioto River)  Hilliard
Lincoln Village Marble Cliff


To receive informative brochures regarding Columbus Drinking Water Quality, call our Customer Service Center at 614- 645-8276 (weekdays 7 am - 6 pm), email [email protected], or view the annual drinking water quality report. For specific questions, call the Water Quality Assurance Laboratory at 614-645-7691 (weekdays 8 am - 4 pm), or email: [email protected].