PFAS contamination in wastewater poses challenges fundamentally distinct from those encountered in drinking‑water treatment. Complex effluents such as landfill leachate, tannery discharges, electroplating wastewater, and municipal secondary effluent typically contain high levels of dissolved organic carbon, surfactants, dyes, metals, oils, and PFAS precursors. These constituents interfere directly with the mechanisms on which conventional PFAS treatment technologies depend. Consequently, methods that perform well in clean water often fail in wastewater environments, becoming prohibitively expensive or generating secondary waste streams that are difficult to manage. Evidence from recent wastewater‑specific studies confirms that no single technology can reliably remove both long‑chain and short‑chain PFAS under practical operating conditions, underscoring the need for a new, multistage treatment architecture (Wei et al., 2019; Barisci & Suri, 2021; Malovanyy et al., 2023).

Activated carbon remains one of the most widely applied sorbents for PFAS, but its effectiveness in wastewater environments is severely limited. In tannery wastewater, only the highest powdered activated carbon (PAC) dose (300 mg/L) reduced PFAS concentrations below 500 ng/L, a result explicitly attributed to “competition phenomena for adsorption between the organics and the PFASs” (Gottardo et al., 2023). Similarly, in PFOSF washing wastewater, coexisting organics suppressed adsorption of perfluorinated carboxylates, with removal efficiencies following the order PFHxA < PFHpA < PFOA (Du et al., 2015). Full‑scale landfill leachate treatment plants using PAC showed no significant reduction in total PFAS, with reverse osmosis being the only process to achieve 98–99% removal (Chen et al., 2022). Comparative studies further demonstrated that PFAS breakthrough in granular activated carbon (GAC) and anion‑exchange columns occurred up to twenty‑seven times faster in leachate than in groundwater (Malovanyy et al., 2023). In municipal wastewater, small‑scale column tests confirmed that GAC could remove PFAS, but at a cost increase of approximately sixty percent relative to current treatment costs (Mortazavian et al., 2025). Collectively, these findings show that activated carbon is unsuitable as a primary PFAS treatment method in wastewater and should be limited to a polishing role following substantial pretreatment.

Ion‑exchange resins demonstrate high selectivity for PFAS in clean water, but their performance declines sharply in complex wastewater matrices. In chromium‑plating wastewater, pilot‑scale tests revealed markedly different breakthrough behaviours for PFOS and 6:2 FTS in anion‑exchange columns. Notably, “the replacement of 6:2 FTS by PFOS and other coexisting organic substances resulted in the concentrations of 6:2 FTS in the AER effluent reaching up to 3.8 times the influent concentrations” (Jiang et al., 2024). Earlier studies on simulated industrial wastewater showed that sulfate and hexavalent chromium interfered with PFOS sorption due to competitive occupation of exchange sites (Deng et al., 2010). While MIEX GOLD resin achieved high removal efficiencies and successful regeneration in relatively simple matrices (Tamanna et al., 2023), broader reviews of municipal and industrial wastewater conclude that both carbon adsorption and ion exchange are generally ineffective for short‑chain PFAS under real conditions. Furthermore, regeneration produces PFAS‑rich brines that require additional treatment or disposal (Woodard et al., 2018). Ion exchange is therefore unsuitable for full‑flow wastewater treatment and is best applied as a polishing step to small, pre‑concentrated streams.

Membrane technologies such as reverse osmosis (RO) and nanofiltration (NF) achieve high PFAS rejection, but their use in wastewater is limited by fouling and concentrate management. A cross‑sectional study of full‑scale landfill leachate treatment systems found that ponds, aeration tanks, PAC, and sand filtration produced no measurable reductions in total PFAS, whereas RO systems achieved 98–99% removal in the permeate (Chen et al., 2022). However, the resulting concentrate posed significant environmental and operational challenges. Recent work on mixed‑matrix membranes demonstrated that PFAS removal from wastewater can exceed 99% when the support matrix incorporates adsorbing components, though performance was strongly dependent on membrane composition and operating conditions (Zahmatkesh et al., 2024). Reviews of emerging membrane approaches highlight their potential but emphasise that cost, fouling, and concentrate management remain barriers to near‑term deployment (Das & Ronen, 2022). Consequently, membranes are unsuitable as a primary PFAS treatment step in wastewater and are best applied to small volumes of concentrated PFAS waste.

Alternative adsorbents such as biochar and composite materials have gained attention for their low cost and sustainability. Reviews of biochar‑based composites for PFAS removal from wastewater highlight their potential but note that many systems require long contact times and high doses to achieve meaningful removal (Kumar et al., 2025; Chavan et al., 2024). Sewage‑sludge‑derived biochars have demonstrated sorption capacities for PFOA comparable to commercial activated carbon at low concentrations (Katinka et al., 2023), while biosolids‑derived biochar has achieved over 80% removal of long‑chain PFAS from contaminated water (Kundu et al., 2020). However, short‑chain PFAS removal remains consistently low, typically in the range of 19–27% (Kundu et al., 2020). In landfill leachate, construction‑and‑demolition wood biochar achieved at best 29% PFAS reduction in batch tests, and one biochar even produced higher PFAS concentrations in column leachates, illustrating how complex wastewater matrices can undermine promising sorbents (Cerlanek et al., 2024). These findings indicate that biochar is unsuitable as a standalone PFAS treatment technology but may serve as a bulk sorbent for long‑chain PFAS and co‑contaminants in an upstream treatment stage.

Seaweed and algal biomasses do not directly adsorb PFAS, but they are highly effective at removing metals, dyes, surfactants, and other organic pollutants that interfere with PFAS‑specific processes. Reviews of seaweed‑based wastewater treatment highlight promising removal of dyes, nutrients, phenolic compounds, and heavy metals, attributing this to the presence of carboxyl, sulfate, hydroxyl, and amino functional groups on the biomass surface (Arumugam et al., 2018; Znad et al., 2022). Green and red seaweed‑based composites have demonstrated removal of dyes such as Congo Red and crystal violet from aqueous solutions (Hamd et al., 2022; AlSaeedi et al., 2023). These properties make seaweed‑derived media particularly well suited for preconditioning wastewater, reducing the load of co‑contaminants that would otherwise suppress PFAS removal downstream.

Foam fractionation has emerged as one of the most promising PFAS‑specific separation techniques for wastewater. A comparative study of landfill leachate treatment found that powdered activated carbon, granular activated carbon, anion‑exchange resin, nanofiltration, ozonation, and foam fractionation could each achieve more than 75% removal of long‑chain PFAS, though often with high resource consumption. Among these, foam fractionation and anion exchange offered the lowest treatment costs, below one euro per cubic metre for at least 90% reduction of PFOS and PFOA (Malovanyy et al., 2023). Additional studies confirm that PFAS strongly enrich at air–water interfaces and within foam, validating the mechanistic basis for foam‑based separation (Buckley et al., 2023). Foam fractionation is already applied in other wastewater contexts, such as pretreatment to reduce organic load in pharmaceutical effluent (Zhang et al., 2023), demonstrating its compatibility with complex matrices. However, foam fractionation is less effective for short‑chain PFAS, which remain in the aqueous phase and therefore require additional polishing.

Destructive technologies such as electrooxidation, plasma treatment, and advanced oxidation processes can mineralise PFAS but are energy‑intensive and highly sensitive to wastewater chemistry. Reviews of electrochemical PFAS destruction emphasise that these methods are best suited to high‑strength, low‑volume waste streams such as AFFF concentrates, ion‑exchange regenerates, and reverse‑osmosis rejects (Dong et al., 2026). Laboratory and pilot‑scale studies on investigation‑derived waste have demonstrated partial defluorination and significant PFAS removal, but at the scale of hundreds of litres rather than full‑flow wastewater (Yanagida et al., 2022). Plasma‑based destruction has shown similar promise for concentrates but remains impractical for bulk wastewater. These technologies therefore belong at the end of a treatment train, applied to small volumes of concentrated PFAS rather than to raw wastewater.

Taken together, the evidence shows that no single technology can meet the combined requirements of PFAS removal, matrix tolerance, cost‑effectiveness, and operational feasibility in wastewater environments. Activated carbon is limited by competition and cost; ion‑exchange by fouling, competitive displacement, and brine generation; membranes by fouling and concentrate management; biochar by short‑chain PFAS limitations and matrix sensitivity; and destructive technologies by energy demand and scale. Seaweed can remove co‑contaminants but not PFAS, while foam fractionation excels at long‑chain PFAS removal but requires pre‑conditioning and downstream polishing. This collective body of research establishes a clear need for a new, multi‑stage treatment system that separates the functions of bulk contaminant removal, PFAS concentration, and final polishing. A two‑stage process—combining natural media for co‑contaminant and long‑chain PFAS reduction with foam fractionation for PFAS concentration—directly addresses the limitations observed across existing technologies and provides a practical, scalable pathway for PFAS mass reduction in wastewater.