The PFAS problem has shifted from removing it to destroying it

When a water utility says it has removed PFAS, the word is doing something specific and slightly misleading. The prevailing treatment technologies — granular activated carbon, ion exchange and high-pressure membranes — concentrate PFAS rather than destroying it, and in doing so generate residual streams that the review literature describes as problematic in their own right [s1].

The compound is not gone. It is somewhere else, in a smaller volume, at a much higher concentration, waiting for a disposal decision. A critical review published on 31 August argues that the field is undergoing a shift from sequestration to destruction, and — more usefully — tries to put the trade-off on a quantitative footing [s1].

Why destruction is hard

The chemistry is the whole problem. PFAS are held together by the carbon–fluorine bond, the strongest single bond in organic chemistry, which is exactly why the compounds persist and exactly why breaking them is energetically expensive [s1]. Decades of use in aqueous film-forming foam, industrial processes and consumer products have produced persistent, highly mobile groundwater plumes now detected on every inhabited continent [s1].

Getting them out of that groundwater is complicated by three physicochemical controls the review highlights: adsorption at air–water interfaces, transformation of precursor compounds into terminal PFAS, and interactions with the surrounding matrix [s1]. Together these govern how plumes evolve and make site characterisation harder than a single sample suggests — a plume can be generating new terminal compounds from precursors while it is being monitored.

The candidate technologies

The review appraises a suite of destruction routes against a common set of criteria: defluorination efficiency, by-product formation, energy demand and field readiness [s1]. The technologies assessed are electrochemical oxidation, UV/sulfite reductive defluorination by hydrated electrons, supercritical water oxidation, plasma-based treatment, sonolysis, and base-mediated low-temperature mineralisation [s1].

The multi-criteria comparison returns no winner. No single technology is superior across all criteria, and the review's conclusion is that separation and destruction are most rationally deployed as complementary stages of an integrated treatment train — concentrate first, then destroy [s1].

The energy argument

This is where the paper does something beyond synthesis. It develops a first-order energy model in which the total energy of a complete treatment train is the energy of separation plus the energy of destruction divided by the concentration factor achieved [s1].

The consequence is a design criterion rather than a preference: a technology-specific break-even concentration factor, given by the ratio of destruction energy to separation energy [s1]. Below that point, the destruction step dominates the energy budget. Above it, the separation step does [s1].

Stated plainly, the model says concentration is what makes destruction energetically viable in the first place — and that past a certain degree of concentration, further effort on the destruction technology stops being where the energy goes [s1]. The review is explicit that energy is not the sole determinant of technology choice, and applies the framework alongside defluorination extent, by-product formation, technology readiness, cost and matrix compatibility [s1].

Where the regulator currently is

This is not a settled area, and the US federal position is itself in draft.

The FY 2020 National Defense Authorization Act, signed on 19 December 2019, directs EPA to publish interim guidance on the destruction and disposal of PFAS and PFAS-containing materials, and to update it at least every three years as appropriate [s2]. On 28 April 2026 EPA released an update to its 16 April 2024 interim guidance for public comment [s2]. The updated document builds on information about technologies that may be feasible and appropriate for destruction or disposal — and, notably, identifies key data gaps and uncertainties that must be resolved before the agency can issue more definitive recommendations [s2].

That last clause is the honest summary of the regulatory state. Seven years after Congress asked for guidance, the guidance is still interim and still lists what it cannot yet say.

Two other proposals bear on the same question from different angles. The proposed sixth Unregulated Contaminant Monitoring Rule would require public water systems to collect national occurrence data for seven ultrashort organofluorine compounds, among other contaminants [s3] — and short-chain and ultrashort compounds are precisely what the review identifies as a priority research need, alongside validated destruction metrics and treatment-train optimisation [s1]. Separately, a draft EPA memorandum released on 6 July addresses reducing risk from PFOA and PFOS in biosolids, the sewage sludge applied to farmland; EPA states that it is non-binding and does not have the force and effect of law, and comments were open through 4 September 2026 [s4]. Biosolids are, in effect, another concentrated residual stream with nowhere obvious to go.

All three documents are proposals or drafts open to comment, not final rules.

What a reader should take from this

Three things, none of them reassuring and none of them alarming.

First, "PFAS removed" and "PFAS destroyed" are different claims, and current municipal treatment overwhelmingly delivers the first [s1]. Second, the destruction technologies exist and work to varying degrees, but none is superior across efficiency, by-products, energy and field readiness at once, which is why none has become standard [s1]. Third, the federal guidance on how to destroy or dispose of the concentrated residues remains interim by its own description, with acknowledged data gaps [s2].

The review's framing of the field's central challenge is worth restating in plain terms: the difficulty is no longer getting PFAS out of water, but converting it, affordably and verifiably, into fluoride [s1]. Verifiably is the operative word — a destruction process that fragments PFAS into unmeasured shorter-chain products has not solved anything, it has changed what needs measuring.

Sources

• [s1] From forever to fluoride: A critical review of PFAS occurrence, fate, and the transition from sequestration to destruction-based remediation in groundwater. Science of The Total Environment, 31 August 2026. https://doi.org/10.1016/j.scitotenv.2026.182278
• [s2] Interim PFAS Destruction and Disposal Guidance; Notice of Availability for Public Comment. US EPA, Federal Register 91 FR 22815, 28 April 2026.
• [s3] Revisions To Establish the Sixth Unregulated Contaminant Monitoring Rule (UCMR 6) for Public Water Systems. US EPA, Federal Register 91 FR 39952, 1 July 2026.
• [s4] Draft Guidance for Reducing Risk From PFOA and PFOS in Biosolids. US EPA, Federal Register 91 FR 41020, 6 July 2026.