Formatted Title
Piloting Nature-Based Solutions for Treatment of PFAS Contamination
Background/Objectives
Due to the resilience of most per- and polyfluoroalkyl substances (PFAS), many remedial technologies have proven ineffective, and current ex situ treatments are energy and/or resource intensive. Identifying innovative, nature-based solutions for treatment of PFAS is critical, to offer more sustainable strategies, carry forward industry lessons learned from traditional contaminants and treat commingled plumes. This presentation provides an overview of two recent pilot studies that utilize nature-based technologies for the treatment of PFAS and co-contaminants of concern.
Approach/Activities
Biogeochemical reactors (BGRs) and treatment wetlands are both green and sustainable remediation (GSR) technologies. Two unique above-ground, combination BGR and treatment wetland systems were piloted in California, USA and Victoria, Australia (Sites) for treatment of PFAS and co-contaminants (chlorinated volatile organic compounds [CVOCs] including 1,1-dichloroethene [DCE], 1,2-dichloroethane [DCA], trichloroethene [TCE], and vinyl chloride). The BGR technology has been used for the remediation of chlorinated solvents and other contaminants over the past decade but has only recently been piloted for PFAS and commingled plumes. BGRs utilize a variety of organic and inorganic amendments that are tailored to support biological treatment, biotransformation, and/or adsorption of contaminants. The use of locally sourced, non-refined or “waste” products in BGR construction, and the use of off-grid groundwater pumping, promote the GSR aspects of this technology.
Similarly, treatment wetlands are a GSR technology that utilize local wetland varieties to passively remove contaminants from surface and groundwater. The primary mechanisms for contaminant removal in treatment wetlands may include direct uptake by plants, bioaccumulation, adsorption, and transformation.
Each pilot study was constructed at the Sites using a series of two BGR microcosm reactors filled with treatment media, followed by three open-top drums to simulate treatment wetlands. Groundwater was pumped from nearby, onsite monitoring wells and gravity fed through two separate treatment trains, one aerated to simulate aerobic conditions and one anaerobic system. Pilot studies were conducted in 2022 and 2023 and are on-going in Australia.
Results/Lessons Learned
Performance results and lessons learned from these two combination BGR and treatment wetland pilot studies will be presented. Initial results show up to 97 percent specific PFAS concentration reductions were observed (6:2 FTS), although reductions were variable and some PFAS concentrations increased through PFAS precursor transformation. In Australia, where influent groundwater contained both PFAS and CVOCs, CVOCs were treated to non-detect during the study. Further research is warranted to optimize PFAS treatment and understanding of PFAS transformation mechanisms.