Forever chemicals (PFAS) in landfill leachate: Insights into fate, transport, and treatment strategies

Per- and poly-fluoroalkyl substances (PFAS) represent a class of persistent synthetic chemicals whose disposal in landfills creates a significant secondary source of environmental contamination via leachate. A critical challenge in leachate management is the transformation of PFAS precursors into more mobile and regulated terminal compounds, such as perfluorooctanoic acid (PFOA) and perfluoro octane sulfonate (PFOS), which complicates risk assessment and treatment. This review addresses the urgent need for a clear understanding of PFAS fate, transport, and remediation in landfill leachate by synthesizing the most recent scientific literature from 2018 to 2025. The novelty of this work lies in its critical evaluation of the concept shift from single-stage removal methods to integrated treatment trains, which couple separation technologies (e.g., foam fractionation, membrane filtration) with destructive technologies (e.g., electrochemical oxidation, supercritical water oxidation). We analyze global variations in leachate concentrations, which can exceed 200,000 ng/L, and critically assess the performance, techno-economic feasibility, and limitations of current remediation strategies. Key research gaps are identified, including the lack of pilot-scale validation for hybrid systems, the need for strong life-cycle assessments, and the ongoing challenge of removing persistent short-chain PFAS. This review provides a comprehensive framework for researchers, engineers, and policymakers to develop and implement sustainable and effective management strategies to mitigate the environmental and public health risks posed by PFAS contaminated landfill leachate.