Conventional wastewater treatment has limited effectiveness in removing perfluoroalkyl and polyfluoroalkyl substances (PFASs) from aqueous waste streams, and therefore WWTPs act as most relevant point sources to the aquatic environment. Long-chain PFASs have a high affinity for organic carbon and proteins and, therefore, the sewage sludge produced in a WWTP may be an important sink of long-chain perfluoroalkyl sulfonic acids (PFSAs) and perfluoroalkyl carboxylic acids (PFCAs) entering WWTPs. Sewage sludge is the “archive” of a WWTP, integrating the mass-flow of sorbing pollutants entering a WWTP steadily or intermittently. To better identify point sources of perfluorooctane sulfonic acid (PFOS) and other PFASs to the aquatic environment, a survey of anaerobically stabilized sewage sludges from 46 municipal WWTPs in Switzerland (n=2-3) was performed to evaluate the levels of PFASs. The targeted selection of the WWTPs was based on the occurrence of potential industrial and commercial emitters in the catchment of the WWTPs. In 19 of 46 studied WWTPs (41%) PFOS concentrations were above 100 μg/kg. The application areas of metal plating and fire fighting foams (aqueous film-forming foam, AFFF) contributed the majority to the emissions of PFOS. PFOS is widely used in metal finishing processes as a foam suppressant and surfactant to reduce surface tension. Increased PFOS concentrations (up to 2’400 μg/kg) occurred in catchments of WWTPs were chromium electroplating industries are located. Individual WWTPs showed significant temporal variability of exposure because wastewaters are often released intermittently. However, the occurrence of metal plating industries in the catchment did not always correlate with higher PFOS concentrations. One reason could be that processes baths are not treated on-site. The use of PFOS in AFFF in Switzerland is allowed until 30.11.2014 for fire-fighting in operational situations. PFOS emissions from AFFF (up to 1’600 μg/kg) exhibited a large temporal and spatial variability in sewage sludge depending on the use on training grounds of fire brigades and the occurrence of major fires. Elevated levels of perfluorooctanoic acid (PFOA, 10‒87 μg/kg) were measured in catchments with potential emitters of PFCAs like textile and carpet protection companies and AFFF. Higher levels of PFCAs compared to PFSAs can be attributed to emissions from textile finishing companies. The high spatial and temporal variability of long-chain PFASs allowed to identify specific sources causing elevated sludge concentrations.