The drinking water utility that serves roughly 600,000 people in the Des Moines metro turned on its nitrate removal facility on Jan. 6 and expects to run the system intermittently over the coming weeks.
It’s due to nitrate levels in the Des Moines and Raccoon rivers, which Central Iowa Water Works (CIWW) said are uncommonly high this time of year. The last time the nitrate removal facility was used during the month of January was in 2015, according to Tami Madsen, executive director of CIWW.
Since last week, Madsen said the Fleur Drive Treatment Plant has operated three out of eight vessels in its sideline process to remove nitrates. At a minimum, the facility can operate two vessels; the maximum is seven, she added.
Operating the system at full capacity can cost upwards of $16,000 per day. CIWW relied on its facility over 100 days last spring and summer and implemented its first lawn watering ban to reduce pressure on the overall system.
Madsen said water produced by the utility continues to meet all state and federal drinking water standards.
The U.S. Environmental Protection Agency set the nitrate limit for public drinking water at 10 milligrams per liter decades ago to prevent a condition called methemoglobinemia, which causes severe oxygen-deprivation illness in infants.
But recent studies indicate lower levels can increase risks for certain types of cancer and birth defects.
High nitrate levels beyond the metro
Nitrate concentrations in streams and rivers are “unseasonably high” across the state, said Larry Weber, director of IIHR—Hydroscience and Engineering at the University of Iowa. The internationally renowned lab manages dozens of sensors that are part of the Iowa Water Quality Information System.
The sensors collect real-time data for nitrate, pH, flow and temperature, along with other parameters.
“Of the 50 or more water quality sensors that we normally have deployed during the spring, summer and fall, many of them are pulled out during the winter season to protect them against ice and freeze up conditions across Iowa,” Weber said. “However, the ones that remain out in some of our larger rivers or streams are reporting concentrations above 10 milligrams per liter.”
Other sensors monitoring small watersheds have recorded twice as much, he added. One at the Bloody Run Creek Headwaters showed nearly 27 milligrams per liter on Saturday.
“In much of the state, short of a couple isolated areas, there's really no frost in the ground right now,” Weber said. “The agricultural tile lines continue to run, and with the tiles flowing, they're bringing higher nitrate concentrations to our streams.”
Nitrates flushed from farm fields could stem from fall application of anhydrous ammonia and manure, as well as excessive amounts held in the soil over longer periods of time, Weber said.
Higher nitrate levels this winter are not the result of torrential rainfall or excess moisture, Weber noted. Half of the state is experiencing some level of dryness or drought, according to the latest U.S. Drought Monitor.
Deploying monitors across the state to collect science-based information is vital for the long-term health of Iowa’s waterways, Weber said.
The state Legislature diverted funding for Iowa’s water monitoring network in 2023. The Walton Family Foundation and Iowa Nutrient Research Center provided bridge funds to keep the University of Iowa sensors running through June of 2026.
Last October, Polk County supervisors voted to provide the network with $200,000, roughly a third of the annual budget. Weber said requests for support have been made to other county boards of supervisors.
