Behavior of Perfluoroalkyl Substance (PFAS) in Sludge Processing at Nine Canadian Sludge Handling Facilities

The occurrence of emerging organic contaminants such as poly- and per-fluoroalkyl substances (PFAS) has raised concerns with beneficial land application of biosolids. The purpose of this study was to examine the occurrence and removal/formation of thirteen PFAS occurring in sludge and biosolids from nine Canadian sludge treatment facilities employing alkaline stabilization (AS), pelletization (P), aerobic digestion (AE1, AE2), and anaerobic digestion (AN1 to AN5) processes. Perfluorodecanoate (PFDA) was the most frequently detected compound (>85%) in the biosolids followed by perflurorooctane sulfonate (PFOS) and perfluorododecanoate (PFDoA). The ΣPFAS-F mass flows in the raw sludge and biosolids were estimated to study the removal performance of different sludge treatment categories. There was a significant increase in mass flow of ΣPFAS-F during pelletization and alkaline stabilization. On the other hand, the mass loadings of ΣPFAS-F decreased at AE2, AN1, AN3, and AN4 by 10 ± 0.2%, 34 ± 0.2%, 10 ± 0.1%, and 38 ± 0.2% through aerobic and anaerobic digestion processes, respectively. Substantial variability in removal/formation characteristics was observed between the biological treatment systems. The findings from this study will better inform the risk assessment and management of exposure to PFAS through biosolids.