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Results from a field trial commissioned for the Australian Department of Defence at the Army Aviation Centre Oakey evaluated the effectiveness of the Surface-Active Foam Fractionation (SAFF) process at removing per-and polyfluoroalkyl substances (PFAS) in groundwater. The study showed that the SAFF process is effective in removing ≥99.5% of the aggregate of perfluorooctane sulfonate (PFOS), perfluorohexane sulfonate (PFHxS), and perfluorooctanoic acid (PFOA) in PFAScontaminated groundwater, and consistently achieved the criteria for these PFAS species prescribed in the Australian PFAS National Environmental Management Plan (HEPA, 2020) water quality specification, and exceeded such by a factor of 3.3 over the 12-month study period. The field trial also demonstrated the sustainability attributes of SAFF since it requires no chemical reagents nor adsorbent media, other than air introduced to the foam fractionation vessels. However, when an anionic exchange (AIX) resin "polisher" was installed downstream of SAFF, all trace detectable PFAS species were removed. In addition, by reducing the PFAS loading, the SAFF process extends the AIX resin lifespan. The field trial demonstrated that the removal (i.e., separation and concentration) extent of PFAS species due to SAFF is closely correlated with the adsorption coefficient of the molecules at the gas-liquid interface. When the reported adsorption coefficient is greater than approximately 1.0 × 10 −6 m, practically all of the PFAS species, including PFOS, PFHxS, and PFOA, were removed by SAFF. Longer-chain PFAS species that benefit from higher adsorption coefficients are easier to remove than shorter-chain species that exhibit lower adsorption coefficient values. It is noted that the presence of dissolved electrolytes arising from the site groundwater being classified as hard is believed to enhance the adsorption coefficients, and so SAFF is likely to become still more effective in brackish, saline, and reverse osmosis reject waters. | INTRODUCTIONThe contamination of groundwaters by per-and polyfluoroalkyl substances (PFAS) has been suggested as a significant global environmental health crisis (Pelch et al., 2019). The epidemiological review of Rappazzo et al. (2017) has reported that PFAS may be associated with various adverse health outcomes in humans including thyroid diseases, testicular and kidney cancers and, in children, delayed onset of puberty. PFAS molecules exhibit environmental persistence due to the strength of their characteristic C-F bonds. There are many general sources of PFAS contamination in groundwater and surface waters arising from the historical use of Class B aqueous film-forming foams (AFFFs) used for firefighting and training purposes, particularly at global defense sites and larger

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