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Peoria IL Water Quality: Illinois River Industry, Agricultural Runoff, and Infrastructure Challenges

March 23, 2026
Peoria Illinois skyline along the Illinois River

Peoria sits on the Illinois River in central Illinois, a mid-sized city of about 115,000 that has been a river town since its founding. The Illinois River is Peoria’s lifeblood and its drinking water source — and everything that happens upstream, from Chicago’s treated wastewater to the fertilizer applied on millions of acres of farmland, eventually flows past Peoria’s water intake.

That makes Peoria’s relationship with its water supply more complicated than most cities its size.

The Illinois River as a Water Source

The Illinois River drains approximately 29,000 square miles of Illinois, including parts of the Chicago metropolitan area and the most intensively farmed land in the state. By the time it reaches Peoria, the river has collected:

Agricultural runoff: Central Illinois is the heart of American corn and soybean production. Nitrogen fertilizer applied to these crops enters the river system through tile drainage, surface runoff, and groundwater discharge. Atrazine, the most commonly used herbicide on corn, spikes in the river during spring application season.

Chicago’s treated wastewater: The Metropolitan Water Reclamation District of Greater Chicago discharges billions of gallons of treated wastewater into the Chicago Sanitary and Ship Canal, which connects to the Des Plaines River and then the Illinois River. While this wastewater meets discharge permits, it adds nutrients, pharmaceuticals, and trace contaminants to the river system.

Industrial discharges: Multiple industrial facilities along the Illinois River corridor hold NPDES permits for wastewater discharge. Historical industrial activity — particularly in the Peoria area, which was a major distillery and manufacturing center — has left legacy contamination in river sediments.

Illinois American Water, which operates Peoria’s water system, treats the river water through a multi-step process including coagulation, sedimentation, filtration, granular activated carbon, and chloramine disinfection. The treatment plant handles the source water’s complexity effectively, meeting all EPA standards.

Nitrate and Agricultural Chemicals

The Illinois River’s nitrate levels are among the highest of any major river system east of the Mississippi, driven overwhelmingly by agricultural drainage. While Peoria’s treated water stays well below the EPA’s 10 mg/L maximum contaminant level for nitrate, the source water concentrations require active management:

Atrazine follows a similar seasonal pattern. Spring application creates concentration spikes that require activated carbon treatment to meet the EPA’s 3 μg/L annual average MCL. Like Des Moines, Iowa — which famously sued upstream agricultural counties over nitrate — Peoria faces the downstream-city dilemma: the pollution is generated elsewhere, but the treatment cost lands here.

Lead Infrastructure

Peoria’s housing stock includes significant pre-1950 construction, particularly in the city’s older neighborhoods south and east of downtown. Lead service lines and lead solder in older plumbing are present throughout these areas.

Illinois American Water conducts Lead and Copper Rule sampling and has maintained compliance with the 15 ppb action level. The utility uses corrosion control treatment to reduce lead leaching. Under the revised Lead and Copper Rule, the utility is conducting a service line inventory to identify and prioritize lead line replacement.

Illinois enacted a Lead Service Line Replacement and Notification Act in 2021, requiring all community water systems to develop replacement plans. This has accelerated inventory work in Peoria and other Illinois cities.

Contaminated Sites

Peoria’s industrial history — including distilleries, farm equipment manufacturing, and chemical production — has left contaminated sites throughout the area:

Peoria Manufactured Gas Plant sites: Several former manufactured gas plants in Peoria contaminated soil and groundwater with coal tar, PAHs, and heavy metals. Remediation at these sites is ongoing under Illinois EPA oversight.

Keystone Steel and Wire: This former steel manufacturing facility in nearby Bartonville generated soil and groundwater contamination from industrial operations. The site has been in various stages of assessment and remediation.

Agricultural chemical storage and handling: Central Illinois’s role as a hub for agricultural chemical distribution means numerous sites where pesticides, fertilizers, and fuel were stored and handled, some with resulting soil and groundwater contamination.

Emerging Contaminants

The Illinois River’s upstream connection to the Chicago metro means Peoria’s source water carries the chemical signature of a major urban area:

PFAS: Testing under EPA’s UCMR 5 has detected low levels of PFAS in the Illinois River and in treated water. Sources include upstream wastewater treatment plants, industrial discharges, and landfill leachate.

Pharmaceuticals and personal care products: Treated wastewater from Chicago and other upstream cities introduces trace levels of drugs, hormones, and personal care product chemicals. While concentrations are low, the long-term health implications of chronic low-level exposure are still being studied.

Microplastics: Research has found microplastics in the Illinois River, consistent with findings in major rivers worldwide. Current treatment processes remove some but not all microplastic particles.

What Peoria Residents Should Know

  1. Illinois American Water’s treated water meets all EPA standards. The utility’s granular activated carbon treatment provides an extra layer of protection against agricultural chemicals and organic compounds.
  2. If you’re in an older home, find out whether you have lead service lines. Contact Illinois American Water or check the utility’s service line inventory. Use a certified lead filter if your home has lead plumbing components.
  3. Flush before drinking after periods of non-use — 30 seconds to 2 minutes of running cold water clears pipe-contact water.
  4. Activated carbon filtration at the point of use provides additional removal of atrazine, PFAS, DBPs, and taste/odor compounds. Reverse osmosis adds nitrate and lead protection.

If you’re concerned about your water quality, a certified water treatment professional can test your water and recommend the right system. In a river city downstream of both industrial Chicago and corn country, that extra layer of knowledge is worth having.

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