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Research article - Peer-reviewed, 2023

Foam fractionation for removal of per- and polyfluoroalkyl substances: Towards closing the mass balance

Smith, Sanne; Lewis, Jeffrey; Wiberg, Karin; Wall, Erik; Ahrens, Lutz

Abstract

Foam fractionation has recently attracted attention as a low-cost and environmentally benign treatment technology for water contaminated with per-and polyfluoroalkyl substances (PFAS). However, data on the mass balance over the foam fractionation process are scarce and when available, gaps in the mass balance are often identified. This study ver-ified the high treatment efficiency of a pilot-scale foam fractionation system for removal of PFAS from industrial water contaminated with aqueous film-forming foam. & sigma;PFAS removal reached up to 84 & DEG;A, and the removal of perfluorooctane sulfonic acid (PFOS) up to 97 & DEG;A,, but the short-chain perfluorobutanoic acid (PFBA) was only removed with a mean efficiency of 1.5 & DEG;A,. In general, mobile short-chain PFAS were removed less efficiently when the perfluo-rocarbon chain length was below six for carboxylic acids and below five for sulfonic acids. Fluctuations in treatment efficiency due to natural variations in the chemistry of the influent water were minor, confirming the robustness of the technology, but significant positive correlations between PFAS removal and influent metal concentration and conductivity were observed. Over all experiments, the mass balance closure did not differ significantly from 100 & DEG;A,. Nonetheless, PFAS sorption to the walls of the reactor was measured, as well as high PFAS emissions by the air exiting the reactor. PFAS emis-sions in aerosols correlated positively with mass balance closure. The elevated aerial PFAS concentrations measured in the experimental facility have implications for worker safety and prevention of PFAS-emissions to the atmosphere, and dem-onstrate the importance of installing appropriate filters on the air outlet of foam fractionation systems.

Keywords

Per-and polyfluoroalkyl substances (PFAS); Water treatment; Air emissions; Foam fractionation; Pilot-scale; Remediation

Published in

Science of the Total Environment
2023, Volume: 871, article number: 162050