Summary

• This study evaluated the effectiveness of RemBind^® 100 and RemBind^® 100X in reducing PFAS leachability and extractability from municipal sludge at different stages of processing into pelletized biosolids.
• Bench-scale trials were conducted using raw sludge, sludge cake, and mixer solids collected from a municipal dewatering facility in Philadelphia, USA, spiked with a mixture of 10 target PFAS compounds.
• PFAS leachability was assessed using the U.S. EPA Synthetic Precipitation Leaching Procedure (SPLP), while PFAS-sorbent binding strength was assessed using U.S. EPA Method 1633A extraction.
• RemBind^® 100X outperformed RemBind^® 100, reducing PFAS leachability by 78.8% and 91.5% at 0.3% and 0.6% dosage rates, respectively, with RemBind^® 100 achieving up to 90% reduction at a 1.2% dosage rate.
• Amendment addition at the raw sludge stage (highest moisture content, 94.7%) provided substantially greater immobilization efficiency than addition at the later cake (30% moisture) or mixer-solids (80% moisture) stages, indicating the point of application is a key factor in performance.
• Short-term aging (30 days) and sequential leaching tests demonstrated sustained and improving PFAS retention over time, supporting the amendments’ suitability for storage prior to land application.
• Both amendments also reduced the leachability of ultrashort-chain PFAS (including TFA), a class of highly mobile compounds that are typically difficult to immobilise. These results should be interpreted as semi-quantitative, as isotopically labeled surrogate standards were not used for this portion of the analysis.
• The findings confirm that sorbent amendments can be effectively integrated into existing municipal sludge-processing systems to reduce PFAS mobility in the resulting biosolids pellets.