Home / Articles / Des Moines Water Quality: The Nitrate Capital of America and What It Costs

Des Moines Water Quality: The Nitrate Capital of America and What It Costs

March 20, 2026
Des Moines Iowa skyline along the Des Moines River

The Nitrate Problem No One Wants to Talk About

Des Moines Water Works (DMWW) serves approximately 600,000 people in central Iowa — and spends millions of dollars every year on something most American water utilities never have to think about: nitrate removal.

The city draws its drinking water from the Raccoon River and the Des Moines River, both of which flow through some of the most intensively farmed land on Earth. Iowa’s 30 million acres of corn and soybean — the same agricultural pressure that affects nearby Omaha and Fresno — production generate enormous quantities of nitrogen fertilizer that washes off fields, percolates through tile drainage systems, and ultimately flows into the rivers that Des Moines drinks from.

During spring and summer — when fertilizer application is highest and rain events flush nitrogen from fields — nitrate concentrations in the Raccoon River routinely exceed the EPA’s Maximum Contaminant Level of 10 mg/L (as nitrogen). In some years, raw water nitrate has peaked above 20 mg/L — double the federal limit.

To deal with this, DMWW operates the world’s largest nitrate removal facility: an ion exchange system that can process up to 10 million gallons per day. When river nitrate spikes, the facility kicks in — at a cost of up to $10,000 per day in chemicals and operations.

The Cost of Agriculture’s Externality

The financial burden on Des Moines is staggering. The utility has spent an estimated $100+ million on nitrate infrastructure and treatment since the early 1990s, when the problem became too severe for blending alone to manage. Annual nitrate removal costs can run $1.5 million or more in heavy years, and capital investments in treatment upgrades continue.

In 2015, DMWW took the unprecedented step of suing three upstream counties — Buena Vista, Sac, and Calhoun — arguing that agricultural drainage districts were effectively point sources of nitrate pollution that should be regulated under the Clean Water Act. The lawsuit was ultimately dismissed in 2017, with the court ruling that the drainage districts were not subject to Clean Water Act permitting.

The case drew national attention to a fundamental tension in American water policy: row crop agriculture is the largest source of nitrate contamination in U.S. waterways, but it’s largely exempt from the Clean Water Act regulations that apply to industrial and municipal dischargers.

Des Moines ratepayers continue to bear the cost of treating contamination they didn’t cause.

Beyond Nitrate: Other Challenges

While nitrate dominates the conversation, Des Moines faces other water quality challenges:

Atrazine and Pesticides

Atrazine — one of the most widely used herbicides in corn production — is routinely detected in Des Moines’s source water, particularly in late spring following field application. The EPA’s MCL for atrazine is 3 ppb, and DMWW monitors and manages levels through treatment timing and activated carbon.

Other agricultural chemicals including metolachlor, acetochlor, and various degradation products are also detected in the rivers, though typically at levels below regulatory limits.

Disinfection Byproducts

The high organic matter content of Iowa’s rivers — driven by agricultural runoff and natural sources — creates significant disinfection byproduct formation potential. DMWW uses a combination of treatment approaches to manage TTHM and HAA5 levels within EPA limits, but the organic-rich source water makes this an ongoing challenge.

Harmful Algal Blooms

Excess nitrogen and phosphorus in Iowa’s rivers fuel algal growth, including potential harmful algal blooms (HABs) that produce cyanotoxins. While Des Moines hasn’t experienced a major cyanotoxin event in its finished water, the utility monitors for microcystins and other algal toxins as part of its treatment protocol.

The nutrient loading that causes HABs comes from the same agricultural sources driving the nitrate problem — it’s all connected.

PFAS

DMWW has been testing for PFAS compounds under the EPA’s UCMR 5 program and the 2024 PFAS rule. Iowa is home to numerous potential PFAS sources, including the Iowa Air National Guard base at the Des Moines International Airport and industrial facilities. Results have been monitored, and the utility is evaluating treatment needs based on the new federal MCLs.

Iowa’s Groundwater: The Hidden Crisis

For Des Moines residents on the municipal system, the nitrate removal facility provides protection. But across Iowa, hundreds of thousands of people drink from private wells that have no treatment at all.

Iowa’s shallow alluvial and bedrock aquifers are heavily contaminated with nitrate. The Iowa Department of Natural Resources estimates that roughly 20% of private wells in the state exceed the EPA’s nitrate limit — and in some agricultural counties, the rate is much higher.

Unlike municipal systems, private wells aren’t required to test for contaminants or install treatment. Many Iowa families — particularly in rural areas — are drinking water with nitrate levels that would trigger regulatory action in a public system.

Research has linked chronic nitrate exposure to increased risk of colorectal cancer, thyroid disease, and adverse birth outcomes, even at levels near or below the current MCL. Some scientists argue the 10 mg/L standard is outdated and should be lowered.

What Residents Can Do

If you’re concerned about your water quality, a certified water treatment professional can test your water and recommend solutions appropriate for Iowa’s specific contamination challenges.

Sources