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Research article - Peer-reviewed, 2023

In‐situ application of colloidal activated carbon for PFAS‐contaminated soil and groundwater: A Swedish case study

Niarchos, Georgios ; Ahrens, Lutz; Berggren Kleja, Dan; Leonard, Gareth; Forde, Jim; Bergman, Jonny; Ribeli, Erik; Schütz, Matilda; Fagerlund, Fritjof


Soil and groundwater contamination by per‐and polyfluoroalkyl substances (PFAS) hasbeen a significant concern to human health and environmental quality. Remediation ofcontaminated sites is crucial to prevent plume expansion but can prove challenging due tothe persistent nature of PFAS combined with their high aqueous mobility. In this casestudy, we investigated the potential of colloidal activated carbon (CAC) for soilstabilization at the pilot scale, aiming to entrap PFAS and prevent their leaching fromsoil into groundwater. Monitoring of the site revealed the presence of two potentialsources of PFAS contamination at concentrations up to 23μgL−1for∑11PFAS ingroundwater. After CAC application, initial results indicated a 76% reduction of∑11PFASand high removal rates for long‐chain PFAS, such as perfluorooctane sulfonic acid andperfluorooctanoic acid. A spike in concentrations was noticed 6 months after injection ofCAC, showing a rebound of the plume and a reduction of treatment effectiveness. Basedon long‐term monitoring data, the treatment effectiveness for∑11PFAS dropped to 52%.The rebound of concentrations was attributed to the plume bypass of the barrier due tothe presence of high conductivity zones, which likely occurred because of seasonalchanges in groundwater flow directions or the CAC application at the site. Thisdemonstrates the need for a detailed and accurate hydrogeological understanding ofcontaminated sites before designing and applying stabilization techniques, especially atsites with high geologic and hydrologic complexity. The results herein can serve as aguideline for treating similar sites and help avoid potential pitfalls of remedial efforts.

Published in

2023, Volume: 33, number: 2, pages: 101-110