Sorry, No Swimming: Tackling PFAS, the Uninvited Guests in Wastewater, Under the CleanWater Act

Introduction

Per- and polyfluoroalkyl substances (PFAS) are one of the most consequential and complex environmental challenges facing publicly-owned treatment works (POTWs) and industrial and commercial dischargers. While regulatory attention on PFAS over the past decade has centered largely on drinking water issues and evolving federal and state standards and public health advisories, the focus is broadening to embrace wastewater discharges, including industrial pretreatment and effluent permitting under the Clean Water Act (CWA), 33 USC Section 1251 et seq.., and analogous state laws.

This evolution has placed POTWs (that neither manufacture nor intentionally use PFAS)—and by upstream dischargers—at the center of an expanding PFAS regulatory and liability regime. Through CWA National Pollutant Discharge Elimination System (NPDES) and State Pollutant Discharge Elimination System (SPDES) permits, pretreatment programs, sludge/biosolid management requirements and emerging federal cross-statute coordination, wastewater utilities (despite limited technological control over their influent sources) and those that discharge to them increasingly bear responsibility for monitoring, reporting and reducing PFAS discharges. This article examines the current legal and technical landscape, highlights key compliance challenges and operational risks and identifies strategic risk management considerations for utilities and regulated dischargers.

Federal PFAS Regulation and CWA Authority

POTWs occupy a uniquely vulnerable position within the PFAS management framework. PFAS enter wastewater systems through residential, commercial and industrial sources, yet conventional treatment processes are largely ineffective at removing them. As a result, PFAS pass through treatment systems into surface waters or accumulate in sewage sludge/biosolids, creating compliance and liability concerns under multiple programs.

To date, the EPA has not promulgated PFAS-specific CWA effluent limitation guidelines (ELGs) or categorical pretreatment standards. Nonetheless, federal activity strongly suggests a tightening regulatory trajectory. EPA is planning the next National Sewage Sludge Survey, coordinated with its POTW Influent PFAS Study (designed to survey PFAS entering POTWs from industrial and domestic sources), to collect updated national data on 40 PFAS using EPA Method 1633. EPA will also collect additional nationwide PFAS data through a voluntary submission portal.

In January 2025, the EPA released its Draft Sewage Sludge Risk Assessment for PFOA and PFOS, concluding that potential human and ecological risks may exceed acceptable thresholds at concentrations of approximately one part per billion (ppb) (exponentially higher than the parts per trillion (ppt) thresholds for federal and state drinking water standards). 90 Fed. Reg. 3859 (Jan. 15, 2025). While the assessment focuses on biosolids management rather than effluent discharges, its findings reinforce the EPA’s emphasis on upstream source control and the need for expanded monitoring. What this will look like when final is uncertain following extensive public comments, but the assessment foreshadows future regulatory action affecting pretreatment requirements, effluent limitations and sludge disposal.

The EPA’s broader PFAS strategy further underscores the convergence of federal legal regimes. The EPA identified April 2026 as a target for proposing a rule designating multiple PFAS compounds as hazardous constituents under the Resource Conservation and Recovery Act (RCRA). At the same time, PFAS reporting obligations have expanded through the Toxic Substances Control Act (TSCA) and the Toxics Release Inventory (TRI)/ Emergency Planning and Community Right-to-Know Act (EPCRA), with more than 200 PFAS now subject to annual disclosures. Collectively, these initiatives signal an increasingly integrated federal PFAS approach that will affect wastewater utilities through permitting, reporting and potential corrective action obligations, even in the absence of technology-based CWA PFAS effluent limits.

NPDES Permitting as the Frontline

In the absence of numeric federal CWA effluent limits, NPDES (and SPDES—see below) permitting has become the primary mechanism through which PFAS regulation of wastewater is implemented. EPA’s December 2022 memorandum encourages permitting authorities to require PFAS monitoring, identifies industrial sources and imposes pretreatment or best management practices (BMPs) where appropriate. See Memorandum from Radhika Fox, Assistant Administrator for Water, U.S. Environmental Protection Agency, to EPA Regional Water Division Directors, Addressing PFAS Discharges in NPDES Permits and Through the Pretreatment Program and Monitoring Programs (Dec. 5, 2022). The memorandum recommends quarterly monitoring for up to 40 PFAS using EPA Method 1633 and reporting through Discharge Monitoring Reports (DMRs), along with narrative permit conditions focused on pollution prevention and source reduction.

The EPA’s draft 2026 multi-sector general permit (MSGP), released in December 2024 and pending finalization, would require quarterly PFAS monitoring in 23 industrial sectors using EPA Method 1633A. Analysis of Per- and Polyfluoroalkyl Substances (PFAS) in Aqueous, Solid, Biosolids, and Tissue Samples by LC‑MS/MS, EPA‑820‑R‑24‑007 (Dec. 2024). Although EPA characterizes PFAS monitoring as “report-only,” the resulting data may be used to support CWA impairment listings, “reasonable potential” determinations that justify water-quality-based effluent limits and enforcement actions and other claims. Be cautioned—monitoring is just the start and a slippery slope; the data generated will undoubtedly become the baseline for the imposition of future permit requirements, including sector‑specific benchmarks or numeric discharge limits, as EPA develops a broader evidentiary record for PFAS regulation under the CWA. And all of the PFAS monitoring data will become public and can be used to support agency enforcement and/or private party litigation.

SPDES: State Innovation and Divergence

State CWA programs have moved faster and more aggressively than at the federal level, creating a patchwork of requirements that can complicate compliance and risk management. States such as Michigan, Wisconsin, Maine and New York require PFAS-specific monitoring/ minimization plans and, in some cases, impose numeric effluent limits in individual SPDES permits (such as for priority facilities in New York). Permits may include numeric limits, action levels, pollutant minimization programs or compliance schedules, especially for facilities discharging to drinking water source waters or handling biosolids. NYSDEC, TOGS 1.3.14—Permitting Strategy for Implementing Guidance Values for PFOA, PFOS, and 1,4-Dioxane (Dec. 2025).

Other states, including California, Washington, Vermont, Rhode Island and Connecticut, are imposing extensive sampling requirements primarily on POTWs, and in some cases on significant industrial users and other direct dischargers, designed to establish the data foundation for future regulatory action, including the likely setting of numeric PFAS effluent limits in permits. Nat’l Conf. of State Legislatures, Per- and Polyfluoroalkyl Substances, https://www.ncsl.org/environment-and-natural-resources/per-and-polyfluoroalkyl-substances (last visited April 15, 2026). State legislative activity continues to accelerate, with Virginia mandating PFAS monitoring in biosolids beginning in 2027 and many other states considering similar measures. Virginia Lawmakers Reach Agreement for First Steps to Monitor PFAS in Biosolids, Va. Mercury (March 2,2026), https://virginiamercury.com/2026/03/02/virginia-lawmakers-reach-agreement-for-first-steps-to-monitor-pfas-in-biosolids/. For owners/operators of multi-jurisdictional utilities, this patchwork increases operational complexity,costs and potential litigation exposure.

Pretreatment Programs

Understanding upstream contribution is a key first step toward developing an effective industrial pretreatment program, which has emerged as the most effective near-term mechanism for POTWs to reduce PFAS in discharges. Under 40 CFR Part 403, POTWs possess broad authority to regulate upstream dischargers through permits, ordinances and enforcement actions. In practice, PFAS pretreatment has relied less on numeric local limits, which are often difficult to justify in the absence of federal criteria, and more on BMPs, such as material substitution, chemical management practices and process optimization.

The EPA and state agencies are increasingly evaluating POTW pretreatment programs against quantifiable benchmarks, such as PFAS concentration reductions, industrial user compliance rates and responsiveness to exceedances, in NPDES permit proceedings, CWA enforcement actions and citizen suits under CWA Section 505. See 40 CFR Part 403; EPA, PFAS Strategic Roadmap: EPA’s Commitments to Action 2021–2024, at 16–18 (Oct. 2021). With several states reporting PFAS load reductions exceeding ninety percent through robust pretreatment initiatives, POTWs have a strong basis to exercise source control authority proactively, both to support good-faith compliance and penalty mitigation in enforcement proceedings, and to establish reasonable care in the event of claims by downstream users. See Mich. Dep’t of Env’t, Great Lakes, & Energy (EGLE), Industrial Pretreatment Program PFAS Initiative: Identified Industrial Sources of PFOS to Municipal Wastewater Treatment Plants 26 (Aug.2020, updated May 2025), (documenting PFOS reductions greater than ninety percent in seven of nine treatment plants through industrial source control); Draft Risk Assessment for PFOA and PFOS in Biosolids, 90 Fed. Reg. 5,236(Jan. 22, 2025) (noting that some state pretreatment programs have achieved a ninety-eight percent reduction in PFOS sewage sludge concentrations); EPA, Policy on Civil Penalties, EPA General Enforcement Policy No. GM–21(Feb. 16, 1984, as updated).

Analytical Uncertainty and Methodology Risks

One persistent challenge for permittees is the lack of a fully approved PFAS analytical method under 40 CFR Part 136. Although the EPA finalized Method 1633A in December 2024 and proposed the Methods Update Rule (MUR 22)to codify it, the rule remains pending. Until codified, permitting authorities must rely on the “any suitable method” provision of 40 CFR § 122.21(e)(3)(ii) where no EPA-approved analytical method exists for a given pollutant, raising questions about data comparability, laboratory capacity, cost and defensibility, which is even more concerning when dealing with complex matrices such as wastewater.

From a litigation perspective, the absence of a promulgated 40 CFR Part 136 method for PFAS creates significant exposure for POTWs. The “any suitable method” provision may result in incomplete or inconsistent datasets, which could nonetheless be used to support reasonable potential determinations or impairment listings; at the same time, shrewd litigants could attack the scientific underpinnings as unreliable or insufficiently validated.

RCRA and CERCLA Liability Implications

PFAS contamination in wastewater now implicates two key federal cleanup statutes, Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) and RCRA, each of which has undergone changes that reshape liability exposure for POTWs and other potentially responsible parties EPA’s designation of PFOA and PFOSas hazardous substances under CERCLA (currently being challenged) exposes POTWs to potential cost recovery and contribution claims for PFAS releases, including discharges authorized by NPDES permits (noting that EPA has indicated it doesn’t intend to enforce against entities, including POTWs, who appear to be innocent parties because they do not manufacture or use PFAS directly. EPA PFAS Enforcement Discretion and Settlement Policy under CERCLA (April 19, 2024)). 42 USC Section 9602; 89 Fed. Reg. 39,124 (May 8, 2024). Although industry groups have sought a statutory “passive receiver” exemption for utilities, no such protection has yet been granted.

Separately, RCRA corrective action authority presents additional risk to POTWs. If PFAS are designated hazardous constituents under RCRA, regulators may assert RCRA authority to require investigation and remediation of releases associated with wastewater treatment operations, including at sludge/biosolid handling units, storage areas and historical disposal sites. For utilities, this raises the prospect of long-term RCRA corrective action obligations independent of CWA permitting compliance.

Citizen Suits and Third-Party Litigation

PFAS monitoring and reporting requirements also increase exposure to citizen suits under CWA Section 505. Discharge monitoring data, narrative water quality standard violations and alleged failures to implement pretreatment requirements or BMPs may provide the basis for citizen suits and/or other third-party claims, even in the absence of required numeric effluent limits. In addition, downstream drinking water utilities and private plaintiffs will increasingly seek to obtain and use monitoring data to support their claims.

Strategic Considerations

In this evolving landscape, proactive strategy is essential. POTWs and industrial/commercial dischargers should work closely with their technical and legal teams to undertake a privileged PFAS risk management plan that emphasizes early source identification, evaluates potential pretreatment options and careful scrutiny of permit sampling and/or effluent limitations obligations being imposed by the EPA or states. Where possible, permits should include phased compliance schedules, adaptive management provisions and clear reopener language tied to changes in analytical methods or future standards. Strategic coordination of obligations under multi sectors (e.g., the CWA, RCRA, TSCA and TRI) will be increasingly important as EPA and state agencies align permitting and enforcement priorities.

Federal law does not yet impose numeric limits on PFAS in biosolids, but the EPA’s January 2025 Draft Sewage Sludge Risk Assessment identified human health risks exceeding acceptable thresholds for land-applied biosolids containing as little as 1ppb of PFOA or PFOS. This could serve as the basis for new limits under 40 CFR Part 503. Meanwhile, the April 2024 CERCLA hazardous substance designation of PFOA and PFOS has independently created potential strict liability for parties across the biosolids supply chain even in the absence of Part 503 standards. In the absence of federal limits for PFAS in biosolids, states have increasingly stepped in. See, e.g., ECOS, PFAS in Biosolids: A Review of State Efforts & Opportunities for Action (Jan. 2023). Maine is the only state so far to impose an outright ban on land application of biosolids from wastewater treatment plants, Me. Rev. Stat. Ann. tit. 38, Section 1306 (7) (2022), while Connecticut banned the sale of biosolids containing PFAS for land application, Conn. Gen.Stat. Section 22a-903c (2024). A growing number of other states have adopted a range of regulatory and monitoring strategies, including tiered concentration thresholds that restrict or prohibit biosolids land application at elevated PFOS and PFOA levels. See, e.g., Mich. Dep’t of Env’t, Great Lakes & Energy, Land Application of Biosolids Containing PFAS Interim Strategy (2024); Wash. Rev. Code Section 70A.226 (2025) (requiring PFAS sampling of biosolids); Md.S.B. 956, 2024 Leg., Reg. Sess. (Md. 2024) (requiring monitoring and regulation of PFAS in biosolids).

Conclusion

Federal and state PFAS requirements have effectively expanded from a drinking water-centric framework to now include a more aggressive wastewater-focused regime, placing POTWs at the center of regulatory oversight despite their limited control over influent sources and lack of proven treatment technologies. Through wastewater discharge permitting, pretreatment mandates, sludge/biosolid management requirements and expanding federal cross-statute authority, municipalities and their wastewater utilities are now expected to manage PFAS risks that originate largely upstream. At the same time, industrial and commercial dischargers are increasingly being drawn into this legal landscape and asked to assume a greater share of responsibility. This shift underscores the need for early and coordinated engagement by POTW owners/operators and industrial/commercial dischargers with experienced technical and legal environmental advisers, proactive source identification and control efforts, and strategic permitting and risk management planning in a regulatory environment advancing faster than available treatment options and as compliance requirements rapidly transform to cost and liability allocation among responsible parties.

Reprinted with permission from the May 4, 2026, issue of The Legal Intelligencer. Further duplication without permission is prohibited. All rights reserved.