Field Demonstration of a Pilot-Scale Plasma Reactor for the Rapid Removal of Poly- and Perfluoroalkyl Substances in Groundwater

A pilot-scale plasma-based water treatment system containing two enhanced contact plasma reactors was deployed to a fire training area at Wright-Patterson Air Force Base to treat poly- and perfluoroalkyl substances (PFAS) in aqueous film-forming foam-impacted groundwater from two monitoring wells, wells B and C. Extracted water from both wells was treated through the plasma trailer in a semibatch mode at flow rates ranging from 2.4 to 8.4 L/min. Long-chain perfluoroalkyl acids (PFAAs; fluorocarbon chain of ≥6) and PFAS precursors were reduced by ≥90% for all flow rates in a single cycle through the reactors. Combined perfluorooctanoic acid and perfluorooctanesulfonic acid concentrations lower than the U.S. Environmental Protection Agency's health advisory level of 70 ng/L were achieved in fewer than three cycles through the reactors. Short-chain PFAAs (fluorocarbon chain of ≤5) were removed to a lesser extent (0–95%) due to their generation during plasma treatment of long-chain PFAAs and PFAS precursors and limited accumulation at the plasma–liquid interface of the reactor. To improve the destruction of short-chain PFAAs, batch mode experiments were performed with the addition of a cationic surfactant (cetrimonium bromide), resulting in an 88% reduction of all short-chain PFAAs within 120 min of treatment.