Field demonstration of coupling ion-exchange resin with electrochemical oxidation for enhanced treatment of per- and polyfluoroalkyl substances (PFAS) in groundwater

Schematic of the pilot-scale IXR-EO treatment train and sampling locations.
Elsevier, Chemical Engineering Journal Advances, Volume 9, 15 March 2022
Liang S., Mora R., Huang Q., Casson R., Wang Y., Woodard S. et al.
This pilot-scale field demonstration evaluated the remediation of poly- and perfluoroalkyl substances (PFAS) from groundwater contaminated with aqueous film-forming foam (AFFF) from a coupled regenerable ion exchange resin (IXR) and electrochemical oxidation (EO) treatment train. A pilot-scale IXR system was used that incorporates a novel resin regeneration process, and recovers and reuses the majority of the regenerant solution using distillation. The pilot system removed PFAS from ∼1,000,000 L (approximately 260,000 gallons) of contaminated groundwater from a fire training area, and treated effluent from the IXR system was non-detect for PFOA and PFOS. The concentrated waste stream (i.e., still bottom) from IXR was treated on-site by an EO system with Ti4O7 electrodes, achieving 80–98% destruction of PFOA and PFOS. The surface area normalized first-order rate constants (kSA) were 3.96 × 10−7 m s−1 and 7.92 × 10−7 m s−1 for PFOA and PFOS, respectively, with short-chain perfluoroalkyl acids (PFAAs) identified as intermediate degradation products. Based on the fluoride recovered and PFAS mass loss measured at the end of EO treatment, fluoride release ratios were 130% for still bottom sample 1 (SB1) and 215% for still bottom sample 2 (SB2), indicating mineralization of unquantified fluorinated compounds in the waste stream. Overall, the electric energy consumed per order of magnitude reduction in concentration (EE/O) for treating PFOA and PFOS in groundwater by the IXR-EO treatment train was 0.131–0.161 kWh/m3 for PFOA and 0.071–0.094 kWh/m3 for PFOS, which was orders of magnitude lower than the reported EE/O values for stand-alone electrochemical treatment. The results of this field demonstration show the promise of coupling regenerable IXR with EO for cost-effective removal, concentrating, and destroying PFAS from groundwater.