A new era in NPDES permitting What PFAS means for Illinois wastewater facilities

They're often called forever chemicals – and unfortunately, the name fits.

Per- and polyfluoroalkyl substances (PFAS) are a large group of human‑made chemicals designed to resist heat, water and oil. That's why they show up in everyday items like nonstick cookware, food packaging, stain‑resistant fabrics, firefighting foam and countless industrial products. The problem is that those same qualities make PFAS extremely persistent once they enter the environment.

PFAS do not readily break down. Instead, they accumulate over time in water, soil, biosolids and in our bodies. Scientific research continues to link certain PFAS compounds to potential health concerns, including immune system impacts, developmental effects and increased cancer risk. Because of these risks, PFAS contamination has become a growing concern for drinking water supplies and surface waters nationwide.

As awareness grows, regulators are responding.

In Illinois, that response now directly affects wastewater treatment plants (WWTPs) through PFAS‑related special conditions added to National Pollutant Discharge Elimination System (NPDES) permits administered by the Illinois Environmental Protection Agency (EPA).

Why PFAS matters in Illinois wastewater
Throughout Illinois, wastewater treatment plants are rarely the original source of PFAS. Rather, they receive PFAS from a wide range of upstream contributors, including:

• Industrial and commercial users.
• Airports and firefighting training facilities.
• Landfills and landfill leachate.
• Consumer products that enter the sewer system during everyday use.

As a result, PFAS in wastewater influent and effluent has become a major area of regulatory focus.

Most conventional wastewater treatment processes were never designed for PFAS removal. Technologies like adsorption, granular activated carbon, ion exchange, high‑pressure membrane systems such as reverse osmosis and membrane filtration can remove PFAS, but they are expensive, energy-intensive and often impractical at the scale of a municipal WWTP.

Because of this, PFAS frequently pass through treatment systems into receiving waters or become concentrated in biosolids, raising concerns about PFAS contamination near sewage discharges and land‑applied biosolids. This creates potential downstream risks to surface water, groundwater and ultimately drinking water supplies.

That reality places WWTPs at a critical checkpoint for PFAS monitoring, occurrence tracking and source control.

Recognizing this role, the Illinois EPA added PFAS‑related special conditions to NPDES permits for major WWTPs – those that treat more than 1 million gallons per day.

That includes many WWTPs across Illinois. Several dozen have already received permits that include PFAS testing, inventory and reduction requirements. Additional facilities will receive these requirements as their NPDES permits are renewed during the permit cycle.

Whether a plant's permit renewal is approaching soon or still years away, the expectations are clear: planning needs to start now. The PFAS permitting process involves long timelines, detailed documentation, analytical testing and dedicated funding. Waiting until a permit is issued can put treatment facilities under unnecessary pressure.

Three new steps in the NPDES permitting process
Illinois' PFAS permitting framework follows a straightforward progression: monitor, identify and reduce. For WWTPs, that translates into three new core requirements.

1. PFAS sampling, monitoring and analytical testing. Facilities must begin PFAS monitoring after permit issuance using EPA Method 1633 (or the analytical method specified in the permit), sampling influent, effluent and biosolids on a required schedule. PFAS detections are expected and establish a baseline, but because testing involves extremely low detection limits, strict sampling protocols are critical to ensure reliable results.

2. PFAS inventory and source identification. Within 12 months of the permit effective date, facilities must identify potential PFAS contributors in their collection system through surveys, SDS reviews and targeted evaluation. This inventory documents potential PFAS sources and evaluates industrial users and other contributors within the service area to help determine where PFAS is entering the system.

3. PFAS reduction planning Within 24 months of the permit effective date, facilities must develop and implement a PFAS reduction initiative that focuses on source identification and reduction strategies rather than costly treatment technologies. These plans outline specific, measurable actions and require annual reporting to document progress and effectiveness.

Planning for NPDES changes is critical
Although PFAS requirements are tied to permit renewals, the internal deadlines are firm. Monitoring begins after permit issuance. Inventories are due within 12 months. Reduction plans must be implemented within 24 months of the permit effective date.

That means utilities should begin planning now, regardless of when their permit expires. Early preparation allows facilities to:

• Budget realistically for PFAS testing, analysis and consulting support.
• Understand potential source contributors and future treatment considerations.
• Reduce compliance risk and avoid last‑minute scheduling challenges.
• Build cooperative, solution‑focused relationships with industrial users.

Fehr Graham's wastewater experts understand Illinois' evolving PFAS regulatory limits, EPA testing requirements and the practical realities of wastewater operations.

We support clients through every stage of the PFAS process, from how to test for PFAS near wastewater plants to evaluating biosolids and PFAS concentrations, then developing realistic, facility‑specific reduction strategies.

Case in point: Fehr Graham worked with the City of Freeport through the PFAS permitting process by analyzing data in 2024 and 2025 – going beyond minimum requirements because of the City's commitment to public safety. The team also tested contributors identified in Freeport's PFAS inventory, allowing the City to pinpoint sources and tailor reduction plans to specific facilities.

Freeport's proactive approach required significant effort, but it established a strong model for other Illinois communities facing PFAS challenges.

Statewide, PFAS regulations will continue to evolve, but one thing is clear: Wastewater treatment plants will play a central role in protecting our communities from PFAS contamination. Starting early, planning carefully and partnering with experienced professionals can make this complex process more manageable – and more effective.