Polk County, Iowa: drinking water report. Polk County is Iowa's most populous county, with about 492,000 residents including Des Moines and its suburbs.
Polk County is Iowa's most populous county, with about 492,000 residents including Des Moines and its suburbs. Des Moines Water Works draws from the Raccoon and Des Moines Rivers and has operated one of the world's largest nitrate removal facilities since 1992 – a distinction the utility would prefer not to hold.
The Raccoon River carries nitrate from Iowa's intensive corn and soybean agriculture. According to Des Moines Water Works' 2024 operations data, raw water nitrate at the intake averaged 10.8 mg/L during March-June – above the MCL, requiring continuous operation of the nitrate removal system. The utility's annual nitrate treatment costs exceeded $1.5 million in 2024.
The Des Moines International Airport has documented AFFF use, and Iowa DNR's 2024 PFAS investigation found PFOS at 9 ppt in monitoring wells near the facility. The EPA's UCMR5 data also detected PFAS in the Des Moines Water Works system at levels requiring enhanced monitoring under the new federal rules.
Des Moines Water Works invests heavily in nitrate removal and delivers water that meets all standards. The treatment works, but it represents an ongoing cost of operating a water system in Iowa's agricultural landscape. Household filtration provides an additional layer beyond the plant-level treatment.
Start by checking your water for seasonal data at your address. A quality carbon filter addresses taste and disinfection byproducts. For comprehensive protection including PFAS, reverse osmosis goes further. Our water filter guide covers systems suited to treated river water. Get your detailed report for seasonal trends, and visit our Iowa page for statewide context.