Leachate recirculation to reduce PFAS discharge from landfills

Given the persistent challenge of PFAS removal from chemically complex landfill leachate, this study investigates leachate recirculation to increase PFAS retention within landfilled materials. The lab-scale column reactor findings suggest that leachate recirculation enhances the sorption removal of anionic PFAS in landfill organics and plastics, leading to PFAS reduction. Using eleven PFAS compounds (i.e., nine carboxylates and two sulfonates) at different concentrations, we demonstrated that PFAS concentrations in landfill organics increased by 134-1000 times and on polyethylene plastics increased by 37-329 times after twelfth recirculation. PFAS removal was significantly higher as carbon chain length and Log K_oc values increased. No PFAS with eight or more carbons were detected in the recirculated leachate (except for PFOA: 88-96 % removal) after six and twelfth recirculation. Short-chain PFAS (C ≤ 7) were retained at 20-65 % after twelfth recirculation. The leachate PFAS levels either decreased or stayed the same after the twelfth recirculation, indicating no desorption of PFAS from organics and plastics under experimental conditions. Mass balance showed total PFAS in organics, leachate, and plastics matched initial reactor load. These findings demonstrate that extremely high concentrations of PFAS can be effectively removed from leachate through proper recirculation within landfills. However, future large-scale studies in real-world landfills are needed to assess the performance and feasibility of this approach.