The manufacture and common consumer uses of products ranging from non-stick surfaces to aqueous film-forming foams have resulted in PFAS detection in the influent and effluent of many water resource recovery facilities (WRRFs), along with detections in waste solids, with subsequent measured impacts to surface water and/or groundwater. Using bench-scale leaching tests of biosolids collected from WRRFs that use differing post-digestion treatment processes, this research assessed PFAS release from finished biosolids. Specifically, the release was examined as a function of PFAS loading in the finished biosolids, the post-digestion processing of the biosolids, and the age of the biosolids. This research may be the first to examine the impacts of both biosolids processing and biosolids aging on PFAS release, and provides a unique data set, as well as insights into the mechanisms that control PFAS leaching. Research Partners: San Francisco Public Utilities Commission, Massachusetts Water Resources Authority, Orange County Sanitation District, Great Lakes Water Authority, and North East Residuals & Biosolids Association. Published in 2022.