DM Water Works forced to use nitrate-removal system for first time since 2017

Elevated nitrate concentrations in its water supply has forced the Des Moines Water Works to begin operating its nitrate-removal system for the first time in five years.

Des Moines Water Works utilizes various filtration procedures to manage issues, including nitrates, with its source water in order to provide safe drinking water to 600,000 central Iowans. The level of nitrate in the utility’s water supply fluctuates, and is attributable to excess nutrients on upstream farmland running off the land and entering Iowa’s rivers, lakes and streams.

The U.S. Environmental Protection Agency’s Safe Drinking Water Standard for nitrate is 10 milligrams per liter, and the nitrate levels in the rivers and groundwater used by the Des Moines Water Works have recently peaked at more than nine milligrams per liter.

As a result, the Water Works is now making use of its nitrate-removal system.

“This is a delicate time,” said Ted Corrigan, CEO and general manager of the Des Moines Water Works. “We are at that point where we are monitoring the nitrate level closely, and it is an hour-by-hour decision on which sources of water to use and how to blend the water source in order to reduce nitrate levels.”

The Water Works’ nitrate removal facility initially began operating in March 1992, but was last used in 2017. Drier conditions the past few years have limited the flow of nutrients into Iowa’s waterways, which has led to lower levels of nitrate in raw source water.

Use of the nitrate-removal system is significant not only because of what it means in terms of water quality, but because of the expense. It can cost up to $10,000 a day to operate the nitrate-removal system, the Des Moines Water Works says.

“While we are able to do the work downstream to remove nitrate to comply with drinking water standards, there is a financial cost to our ratepayers to do so,” Corrigan said. “The real solution is upstream. The landowners there are the solution-holders. They have the ability to make changes to the way they use their land in order to keep nutrients on the land and in the soil, which is where they belong.”

The utility’s nitrate-removal system captures nitrate ions in the water, similar to the way a home water softener removes calcium and magnesium ions. The nitrate-removal waste is then diverted to the Des Moines Metropolitan Wastewater Reclamation Authority where it is treated.

The Des Moines Water Works is Iowa’s largest drinking water utility and provides drinking water to one-fifth of the state’s population.