Per‐ and polyfluoroalkyl substances in untreated and treated sludge/biosolids from 27 water resource recovery facilities across the United States and Canada

Abstract Per‐ and polyfluoroalkyl substances (PFAS) are being studied in all environmental matrices because of their ubiquitous presence and adverse human health impacts. This study conducted a surveillance of 27 water resource recovery facilities throughout the United States and Canada to screen the range of PFAS concentrations in pre‐stabilized sludge and post‐stabilized product. Among the 27 water resource recovery facilities, 82% use anaerobic digestion and the rest use chemical stabilization and/or incineration for sludge stabilization. Forty PFAS compounds were evaluated by US Environmental Protection Agency Method SW846/537.1, and four and nine compounds were reported in the pre‐stabilized sludge and post‐stabilized product, respectively. Concentrations of reported compounds in pre‐stabilized sludge and post‐stabilized product varied from 5 to 33 ng/g dry basis and 2 to 220 ng/g dry basis, respectively. 3‐Perfluoropentylpropanoic acid (5:3 FTCA) and perfluorooctanesulfonic acid (PFOS) were the most frequently observed compounds, and PFAS concentrations in the post‐stabilized products were generally higher than the corresponding pre‐stabilized sludge. Practitioner Points Among the 40 target PFAS, four were above reporting limit in the pre‐stabilized sludge and nine in the post‐stabilized product. Incineration ash (post‐stabilized product) samples did not have any reportable PFAS. 5:3 FTCA and PFOS were the two frequently observed compounds; concentrations were higher in the post‐stabilized product compared to the pre‐stabilized sludge. PFPeA and PFHxA were the only two short chain perfluoroalkyl carboxylic acids reported. PFOA was reported in only one of the 54 samples evaluated.