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Doctoral thesis, 2023

Innovative treatment technologies for PFAS-contaminated water - Utilizing foam partitioning and exploring electrochemical oxidation

Smith, Sanne

Abstract

The presence of per- and polyfluoroalkyl substances (PFAS) in the aquatic environment has become a global cause for concern. PFAS are persistent anthropogenic chemicals, and certain PFAS are known to be mobile, bioaccumulative and toxic. PFAS are often found in landfill leachate, effluents from industrial and municipal wastewater treatment plants, and groundwater contaminated with aqueous film-forming foam (AFFF). Conventional wastewater treatment technologies are typically inefficient towards the removal of PFAS. Therefore, this thesis aimed to explore the effectiveness of foam fractionation (FF) and electrochemical oxidation (EO) for PFAS removal and degradation.

In FF, PFAS adsorb to rising air bubbles and are separated from the water as a concentrated foam. In this thesis, a continuous pilot-scale FF reactor was optimized for PFAS removal from landfill leachate, reaching ΣPFAS removal efficiencies of 60%. Gaps in the mass balance were identified, so a follow-up study assessed if emissions to air could explain this loss of PFAS. Here, FF could remove up to 84% of ΣPFAS from AFFF-contaminated industrial water. While the measured PFAS emissions to air were high, they did not contribute significantly to the mass balance.

EO was tested as a destructive technology for the treatment of fractionated foam produced from groundwater and landfill leachate. Treatment effectiveness was assessed with thorough analysis strategies, including target analysis, PFAS sum parameters and effect-based methods, and a coupled numerical model was developed to describe the PFAS degradation kinetics. While the total degradation was higher with EO only, the energy efficiency of the FF+EO system was higher.

Finally, the potential of integrating foam fractionation with existing treatment processes was investigated. Foam was sampled from ten different full-scale water treatment plants, and it was found that the ΣPFAS enrichment relative to the influent reached up to a factor of 105. However, no PFAS removal from influent to effluent was found, possibly because the foam was not actually removed in any of the processes. Altogether, this thesis contributes to an increased understanding of treatment options for PFAS contaminated water, with a particular focus on FF and EO.

Keywords

PFAS; wastewater treatment; foam fractionation; electrochemical oxidation

Published in

Acta Universitatis Agriculturae Sueciae
2023, number: 2023:53
ISBN: 978-91-8046-158-0, eISBN: 978-91-8046-159-7
Publisher: Swedish University of Agricultural Sciences

    UKÄ Subject classification

    Water Engineering
    Water Treatment

    Publication identifier

    DOI: https://doi.org/10.54612/a.6p8i5lbs8l

    Permanent link to this page (URI)

    https://res.slu.se/id/publ/122216