Evaluating RemBind Amendments for Reducing the Leachability and Extractability of PFAS in Municipal Sludge-derived Pellets

Per- and polyfluoroalkyl substances (PFAS) accumulate in municipal sewage sludge and biosolids, creating a potential source of environmental release following land application. This study evaluated two sorbents, RemBind100 and RemBind100X, for limiting PFAS release from sludge-derived pellets. Bench-scale experiments were conducted using samples collected at different stages of the sludge-processing train and spiked with a mixture of 10 PFAS. Amendment performance was evaluated using the U.S. EPA Synthetic Precipitation Leaching Procedure to assess PFAS leachability and U.S. EPA Method 1633 A extraction to assess PFAS-sorbent binding strength. RemBind100X outperformed RemBind100, reducing Σ 10 PFAS leachability of 78.81±1.32% and 91.48±2.64% at 0.3% and 0.6% (w/w), respectively. Extractable Σ 10 PFAS also decreased by up to ~50% with increasing amendment dosage, indicating stronger PFAS retention. Amendment addition at the raw sludge stage provided the greatest immobilization efficiency compared to later stages of sludge processing. Short-term aging and sequential leaching tests demonstrated sustained PFAS retention. Both amendments also reduced the leachability of background ultrashort-chain PFAS present in sludge, indicating applicability to highly mobile PFAS species. These findings demonstrate the potential of sorbent amendments to reduce PFAS mobility in municipal sludge-derived pellets and highlight the influence of amendment dosage and point of amendment addition during sludge-processing on PFAS immobilization.