Optimizing foam fractionation for PFAS removal from landfill leachate: treatment performance and operational insights

Per- and polyfluoroalkyl substances (PFAS) present in landfill leachate are a major concern due to their persistence, potential health and environmental impacts, and significant loading contribution to receiving wastewater treatment facilities, highlighting the critical need for effective treatment strategies. This study evaluates the effectiveness of five series of foam fractionation (FF) experiments in removing PFAS from landfill leachate and compares the performance of key operational parameters. Longer residence times generally improved the removal efficiencies of both long-chain and short-chain PFAS compounds. Baseline removal of short-chain PFAS (e.g., PFBS, PFHxA, PFBA) was modest, ranging from 10 to 40 %, but increased substantially with cationic surfactants such as CTAB or proprietary blends, achieving 50-90 % removal for select compounds. Long-chain PFAS (e.g., PFOS, PFOA, PFHxS) achieved high removal (>97-99 %) even without surfactant addition, reaching non-detect levels through proper optimization of residence time and FF staging. For the specific leachate tested, a 45-min residence time was found to be sufficient to achieve near-complete removal of long-chain PFAS compounds, whereas longer contact times (>100 min) led to decreased foam stability and diminished performance. Substituting ozone for air further enhanced overall PFAS removal (e.g., PFOS >95 % under comparable conditions) and improved foam stability, although at the expense of greater safety requirements, higher cost, and added operational complexity. Re-foaming primary foamate further concentrated PFAS by 93-143× and reduced treated volume by up to 180×, supporting efficient integration with volume-limited emerging destruction technologies such as supercritical water oxidation (SCWO) and electro-oxidation (EO). These results underscore the importance of customizing operational parameters, prioritizing residence time, surfactant dosage and type, carrier gas, and system configuration, through site-specific piloting to maximize PFAS removal efficiency and foamate production for downstream destruction. Future research should further explore the potential impacts and toxicity of co-surfactants in downstream biological treatment processes to ensure comprehensive and sustainable PFAS remediation strategies.