Department Environmental Chemistry

Occurrence of PFASs in Swiss Wastewater Treatment Plants

Photo: Christa McArdell, Eawag
Biological treatment at a WWTP

Per- and polyfluoroalkyl substances (PFASs) are a wide-ranging group of persistent organic pollutants characterized by the presence of high strength carbon-fluorine bonds with widespread use in industry and consumer products. Some PFASs have the potential to bioaccumulate and many have demonstrated toxicological effects. Low PFAS threshold values have been set in the EU drinking water directive, and freshwater quality standards are under consideration. When PFASs enter the water cycle, they often remain stable and are unable to be removed by natural or conventional water treatment processes. Wastewater treatment plants are an important point source for PFASs into aquatic systems, and they provide a representative indication of the types and amounts of different PFASs sourced from industry and municipalities within a defined catchment.

The aims of the project are to determine the occurrence of PFASs in Swiss wastewater treatment plants and to compare the concentrations today to historical measurements from the previous decade. A wide range of target substances will be assessed, and additional suspect and non-target screening is envisaged. Samples from wastewater influent, effluent, and sewage sludge will be analyzed to gain an understanding of contaminant occurrence and fate throughout the wastewater treatment process. These results will aid efforts to identify important PFASs present in wastewater streams and their potential sources, and they will provide crucial data to guide national use and discharge limits.

Publications

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      authors => protected'Chow, S. J.; Braxmaier, E.-M.; Haffter, F.; McArdell,&nb
         sp;C. S.; Hollender, J.' (109 chars)
      title => protected'Wide-spectrum target and total oxidizable precursor PFAS quantification with
          online enrichment and LC-HRMS: overcoming analytical and matrix complexity 
         in wastewater and sludge' (176 chars)
      journal => protected'Journal of Hazardous Materials' (30 chars)
      year => protected2026 (integer)
      volume => protected514 (integer)
      issue => protected'' (0 chars)
      startpage => protected'142842 (15 pp.)' (15 chars)
      otherpage => protected'' (0 chars)
      categories => protected'PFASs; high-resolution mass spectrometry; wastewater; sludge; total oxidizab
         le precursor assay; online solid-phase extraction; ion competition' (142 chars)
      description => protected'Monitoring chemically diverse per- and polyfluoroalkyl substances (PFASs) in
          complex environmental matrices requires robust, streamlined analytical work
         flows. This study developed a high-throughput peak-focusing online solid-pha
         se extraction (SPE) liquid chromatography high-resolution mass spectrometry 
         (LC-HRMS) workflow to quantify 63 PFASs (n<sub>CF</sub> = 1–17, excludin
         g trifluoroacetic acid) in wastewater, sludge, and total oxidizable precurso
         r (TOP) assay samples. Underreported analytical challenges including HRMS is
         obars and precursor leaching from micropipette tips were investigated. Co-ex
         tracted matrix constituents, tentatively identified as linear alkylbenzene s
         ulfonates and long-chain fatty acids, induced Orbitrap-specific ion competit
         ion that hindered quantification of long-chain PFASs in influent and sludge.
          Splitting the MS scan into two time- and mass-dependent ranges mitigated th
         ese effects and restored analyte sensitivity while maintaining full-scan cap
         abilities. Validation using contemporary samples from two wastewater treatme
         nt plants (WWTPs) and legacy NIST SRM 2781 sludge demonstrated high reproduc
         ibility (intra-batch precision 8–17% for 95% of analytes). Median matrix l
         imits of quantification were 2.5 ng/L (influent), 1 ng/L (effluent), and
          1 ng/g (sludge). WWTP measurements revealed zwitterionic 6:2 fluorotelome
         r sulfonamide alkylbetaine (6:2 FTAB) as a dominant precursor in wastewater 
         (max 405 ng/L) and sludge (max 60 ng/g), exceeding concentrations of ubi
         quitous perfluorocarboxylic acids (PFCAs), perfluorooctane sulfonic acid (PF
         OS), and other legacy PFASs. TOP assay results revealed substantial unknown 
         precursor gaps, particularly in sludges where &gt; 90% of oxidizable PFAS 
         mass could not be explained by target precursors. To fill such PFAS mass gap
         s, this scalable full-scan analytical approach can readily accommodate new t
         arget analytes and provide valuable HRMS data for retrospective screening.' (1974 chars)
      serialnumber => protected'0304-3894' (9 chars)
      doi => protected'10.1016/j.jhazmat.2026.142842' (29 chars)
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      originalId => protected13952 (integer)
      authors => protected'Alder,&nbsp;A.&nbsp;C.; van der Voet,&nbsp;J.' (45 chars)
      title => protected'Occurrence and point source characterization of perfluoroalkyl acids in sewa
         ge sludge' (85 chars)
      journal => protected'Chemosphere' (11 chars)
      year => protected2015 (integer)
      volume => protected129 (integer)
      issue => protected'' (0 chars)
      startpage => protected'62' (2 chars)
      otherpage => protected'73' (2 chars)
      categories => protected'PFAA; PFOS; PFOA; metal plating; AFFF; landfill leachate' (56 chars)
      description => protected'The occurrence and levels of perfluoroalkyl acids (PFAAs) emitted from speci
         fic pollution sources into the aquatic environment in Switzerland were studi
         ed using digested sewage sludges from 45 wastewater treatment plants in catc
         hments containing a wide range of potential industrial emitters. Concentrati
         ons of individual PFAAs show a high spatial and temporal variability, which 
         infers different contributions from industrial technologies and activities. 
         Perfluorooctane sulfonic acid (PFOS) was generally the predominant PFAA with
          concentrations varying between 4 and 2440 μg kg<SUP>−1</SUP> (median 75 
         μg kg<SUP>−1</SUP>). Elevated emissions were especially observed in catch
         ments capturing discharges from metal plating industries (median 82 μg kg<S
         UP>−1</SUP>), aqueous firefighting foams (median 215 μg kg<SUP>−1</SUP>
         ) and landfill leachates (median 107 μg kg<SUP>−1</SUP>). Some elevated p
         erfluoroalkyl carboxylic acids (PFCAs) levels could be attributed to emissio
         ns from textile finishing industries with concentrations up to 233 μg kg<SU
         P>−1</SUP> in sewage sludge. Assuming sorption to sludge for PFOS and PFCA
         s of 15% and 2%, respectively, concentrations in wastewater effluents up to 
         the low μg L<SUP>−1</SUP> level were estimated. Even if wastewater may be
          expected to be diluted between 10 and 100 times by the receiving waters, el
         evated concentrations may be reached at specific locations. Although sewage 
         sludge is a minor compartment for PFAAs in WWTPs, these investigations are h
         elpful for the identification of hot-spots from industrial emitters as well 
         as to estimate monthly average concentrations in wastewater.' (1656 chars)
      serialnumber => protected'0045-6535' (9 chars)
      doi => protected'10.1016/j.chemosphere.2014.07.045' (33 chars)
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Wide-spectrum target and total oxidizable precursor PFAS quantification with online enrichment and LC-HRMS: overcoming analytical and matrix complexity in wastewater and sludge

Monitoring chemically diverse per- and polyfluoroalkyl substances (PFASs) in complex environmental matrices requires robust, streamlined analytical workflows. This study developed a high-throughput peak-focusing online solid-phase extraction (SPE) liquid chromatography high-resolution mass spectrometry (LC-HRMS) workflow to quantify 63 PFASs (nCF = 1–17, excluding trifluoroacetic acid) in wastewater, sludge, and total oxidizable precursor (TOP) assay samples. Underreported analytical challenges including HRMS isobars and precursor leaching from micropipette tips were investigated. Co-extracted matrix constituents, tentatively identified as linear alkylbenzene sulfonates and long-chain fatty acids, induced Orbitrap-specific ion competition that hindered quantification of long-chain PFASs in influent and sludge. Splitting the MS scan into two time- and mass-dependent ranges mitigated these effects and restored analyte sensitivity while maintaining full-scan capabilities. Validation using contemporary samples from two wastewater treatment plants (WWTPs) and legacy NIST SRM 2781 sludge demonstrated high reproducibility (intra-batch precision 8–17% for 95% of analytes). Median matrix limits of quantification were 2.5 ng/L (influent), 1 ng/L (effluent), and 1 ng/g (sludge). WWTP measurements revealed zwitterionic 6:2 fluorotelomer sulfonamide alkylbetaine (6:2 FTAB) as a dominant precursor in wastewater (max 405 ng/L) and sludge (max 60 ng/g), exceeding concentrations of ubiquitous perfluorocarboxylic acids (PFCAs), perfluorooctane sulfonic acid (PFOS), and other legacy PFASs. TOP assay results revealed substantial unknown precursor gaps, particularly in sludges where > 90% of oxidizable PFAS mass could not be explained by target precursors. To fill such PFAS mass gaps, this scalable full-scan analytical approach can readily accommodate new target analytes and provide valuable HRMS data for retrospective screening.
Chow, S. J.; Braxmaier, E.-M.; Haffter, F.; McArdell, C. S.; Hollender, J. (2026) Wide-spectrum target and total oxidizable precursor PFAS quantification with online enrichment and LC-HRMS: overcoming analytical and matrix complexity in wastewater and sludge, Journal of Hazardous Materials, 514, 142842 (15 pp.), doi:10.1016/j.jhazmat.2026.142842, Institutional Repository

Occurrence and point source characterization of perfluoroalkyl acids in sewage sludge

The occurrence and levels of perfluoroalkyl acids (PFAAs) emitted from specific pollution sources into the aquatic environment in Switzerland were studied using digested sewage sludges from 45 wastewater treatment plants in catchments containing a wide range of potential industrial emitters. Concentrations of individual PFAAs show a high spatial and temporal variability, which infers different contributions from industrial technologies and activities. Perfluorooctane sulfonic acid (PFOS) was generally the predominant PFAA with concentrations varying between 4 and 2440 μg kg−1 (median 75 μg kg−1). Elevated emissions were especially observed in catchments capturing discharges from metal plating industries (median 82 μg kg−1), aqueous firefighting foams (median 215 μg kg−1) and landfill leachates (median 107 μg kg−1). Some elevated perfluoroalkyl carboxylic acids (PFCAs) levels could be attributed to emissions from textile finishing industries with concentrations up to 233 μg kg−1 in sewage sludge. Assuming sorption to sludge for PFOS and PFCAs of 15% and 2%, respectively, concentrations in wastewater effluents up to the low μg L−1 level were estimated. Even if wastewater may be expected to be diluted between 10 and 100 times by the receiving waters, elevated concentrations may be reached at specific locations. Although sewage sludge is a minor compartment for PFAAs in WWTPs, these investigations are helpful for the identification of hot-spots from industrial emitters as well as to estimate monthly average concentrations in wastewater.
Alder, A. C.; van der Voet, J. (2015) Occurrence and point source characterization of perfluoroalkyl acids in sewage sludge, Chemosphere, 129, 62-73, doi:10.1016/j.chemosphere.2014.07.045, Institutional Repository