ZeroPM removal workshop: PFAS in sewage sludge: occurrence, removal technologies and threats for the environment

3rd ZeroPM Workshop Achieving Zero Pollution of Persistent and Mobile Substances Removal through Technical Solutions October 7th and 8th, 2025 University of the Aegean Mytilene, Greece This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 101036756. PFAS in sewage sludge: occurrence, removal technologies and threats for the environment Nasos Stasinakis, Professor Department of Environment, University of the Aegean Structure of the presentation •What we know about PFAS occurrence and fate in Sewage Treatment Plants? •Is there any threat for the environment due to application of sewage sludge to the soil? •Are PFAS removed during conventional sludge treatment? •Which is the contribution of ZeroPM on PFAS and sewage sludge treatment? PFAS in Sewage Treatment Plants: first findings 2006 Detection in domestic wastewater (USA, NY) 2005 Detection in Sewage Sludge (USA, SF) Higgins et al (2005) https://doi.org/10.1021/es048245p ✓Digested and primary sludge from 11 STPs ✓[PFOS] in sludge: 14-2610 ng/g ✓[PFOS] in sediments: up to 3.8 ng/g ✓Existence of PFOS precursors in sludge samples: N-MeFOSAA, NEtFOSAA Sinclair and Kannan (2006) https://doi.org/10.1021/es051798v ✓Raw and treated WW from 6 STPs ✓[PFOA] > [PFOS] ✓[PFOA] in WW: 58-1050 ng/L Fate of PFAS along wastewater treatment line ➢Biotransformation of some precursors ➢No biotransformation of known PFAS ➢Sorption to activated sludge ➢Sorption to TSS ➢Accumulation to primary sludge ➢Increased [C] for some compounds (e.g. PFOA) ➢No change for other (e.g. PFOS, sorption = formation by precursors) ➢Need for extra treatment step PFAS sorption to sludge Arvaniti et al (2014) https://doi.org/10.1016/j.chemosphere.2014.03.087 •Partitioning coefficients increase with increased fluoroalkyl chain length •PFSA compounds had higher sorption capacities compared to PFCA compounds •Lower pH and higher [Ca2+] increased PFAS sorption Ca2+ Na+ Ebrahimi et al (2021) https://doi.org/10.1016/j.chemosphere.2020.129530 Trends in PFAS concentrations found in STPs (USA) Thompson et al (2022) https://doi.org/10.1021/acsestwater.1c00377 Treated wastewater •Declined concentrations of long chain PFAS over time ➢Average [PFOA] : 68.9 ng/L (data 1998-2020) ➢Average [PFOA] : 12.8 ng/L (data 2013-2020) •Increased concentrations of short chain PFAAS •Higher concentrations in case that industrial WW are discharged to the STP Sludge •Average [PFOA] : 23.8 ng/g (data 1998-2020) •Average [PFOS] : 233 ng/g (data 1998-2020) Correlations between log-transformed wastewater effluent PFOA and PFBA concentrations and sample year in the US without stated industrial sources. Occurrence of PFAS in sewage sludge worldwide 20151 •Number of PFAS detected in sludge: 19 •PFCAs (C4 to C18); PFSAs (C4 to C10); perfluoroalkyl sulfonamides, FASA •[C]: few ng/g to some hundred ng/g •Most analytical methods focused to 6 to 10 PFAS 1Arvaniti & Stasinakis (2015) https://doi.org/10.1016/j.scitotenv.2015.04.023 2Arvaniti et al (2024) https://doi.org/10.1186/s12302-024-01031-3 20242 •Number of PFAS detected in sludge: 178 •Ultrashort- (C<4); new generations PFAS (e.g. GenX); PFAS precursors •PFOS, PFDS, EtFOSA, PFOA at the highest C •Analytical methods available for >40 PFAS Sludge management and threats from PFAS detection •8.3 million tonnes per year of sewage sludge (as DS) are produced in EU •In EU 50% of the produced sludge is disposed to soil (agriculture + composting) •In US 43% of the produced sludge is disposed to soil •Important amounts are also disposed to landfills Lab experiments: hydrothermal carbonization •With exception of PFOS and PFUdA, high removal (>85%) of PFAS under all tested conditions •Detection of trace amounts of some PFAS in the gas phase Removal efficiencies based on analysis of dissolved & particulate phase and application of mass balance Altiparmaki et al. (2024) Setac Europe 34th Annual Meeting, 5–9 May 2024, Seville, Spain, 6.12P-Tu537 Pilot-scale experiments: 1st year of monitoring –Phases A, B and C Pilot-scale experiments: 1st year of monitoring –Phases A, B and C •25 out of 27 target PFAS are detected in raw sludge, at concentrations up to 16 ng/g •No important removal during conventional anaerobic digestion •Significant removal ranging between 40 and 100% during hydrothermal carbonization Removal efficiency: based on analysis of dissolved & particulate phase and application of mass balance 0 2 4 6 8 10 12 14 16 18 20 6:2FTS PFDA PFOS PFOA PFNA PFTeDA PFUdA PFHpA PFBS N-EtPFOSAA PFBA PFPeA N-… PFDoA PFOSA PFOSAA PFTrDA PFHxA 8:2FTS PFHxS PFPeS 4:2FTS GenX Adona PFNS Total concentration in raw sludge (ng/g dw) 0 20 40 60 80 100 120 PFHxA PFHpA PFOA PFNA PFDA PFUdA PFDoA PFTrDA PFTeDA Adona PFBS PFPeS PFHxS PFOS PFNS 6:2 FTS 8:2 FTS PFOSA PFOSAA N-MeFOSAA N-EtFOSAA Total removal in HTC (%) Pilot-scale experiments: 2nd year of monitoring –further steps •To investigate the role of GAC addition and voltage application in the AD •To test different experimental conditions on the operation of HTC •To study the characteristics of hydrochar and its sorption potential •To examine the characteristics and the treatment of hydrochar liquid Thank you for your attention Contact info Athanasios (Nasos) Stasinakis Department of Environment, University of the Aegean Email: [email protected]