Sustainability Assessment of In Situ and Ex Situ Remediation of PFAS‐Contaminated Groundwater

ABSTRACT A life cycle assessment (LCA) was conducted to evaluate the environmental impacts of two approaches for remediating groundwater contaminated with per‐ and polyfluoroalkyl substances (PFAS): an in situ injectable sorption barrier using colloidal activated carbon (CAC) and an ex situ pump‐and‐treat (P&T) system utilizing a granular activated carbon (GAC) filter. The study was based on a real‐world PFAS‐contaminated site in which a CAC barrier was implemented downgradient of a PFAS source at a commercial airport. A theoretical design for a P&T system at the same site was created to facilitate a direct comparison. For both approaches, the assessment used cradle‐to‐grave boundaries while comparing the carbon footprint, total cost of ownership (TCO), and broader sustainability metrics. The results showed that the in situ CAC barrier emitted 98% fewer greenhouse gases (GHG) compared to the ex situ P&T system (56 metric tons of carbon dioxide‐equivalents, t CO 2 ‐eq, vs. 3922 t CO 2 ‐eq) over 15 years. With its passive design, the CAC barrier reduced waste and raw material usage by 95%, leading to a more favorable sustainability score (84 vs. 43), as determined from open‐access sustainable remediation assessment modeling tools. Additionally, the TCO for the CAC barrier was calculated to be approximately 40% of the estimated TCO of the P&T system ($1.6 M vs. $4.1 M). These findings highlight the potential environmental, economic, and societal advantages of using the in situ CAC approach to remediate PFAS‐contaminated groundwater.