Formatted Title
An Innovative Plasma Technology for Treatment of AFFF Rinsate from Firefighting Delivery System
Background/Objectives
Aqueous film-forming foams (AFFF) have been widely used as a fire suppressant for firefighting efforts and training activities at hundreds of Department of Defense (DoD) installations nationwide. Historical formulations of AFFF contained a variety of per- and polyfluoroalkyl substances (PFAS), including perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS), short-chain PFAS, and other fluorinated derivatives. Based on their recalcitrant nature, potential toxicity, and ability to bioaccumulate in the environment, PFAS have received significant regulatory attention, with federal and many state agencies establishing stringent health advisory levels and other recommended criteria. For this class of chemicals, conventional groundwater and soil cleanup systems are largely proving to be ineffective. Several novel treatment approaches are being explored including some that are able to break down these compounds. However, to date, only few PFAS destructive technologies have been demonstrated in the field. Enhanced contact plasma reactors for PFAS destruction were initially developed at Clarkson University and are being commercialized by DMAX Plasma Inc. The systems have been installed into mobile trailers and successfully field demonstrated at several locations. This work presents the operation of a mobile plasma treatment system designed specifically for treating rinsates derived from aircraft rescue and fire-fighting (ARFF) vehicles stationed at Tyndall Air Force Base (AFB).
Approach/Activities
The plasma technology uses electricity to convert water into a mixture of highly reactive species (i.e., plasma) that rapidly and non-selectively degrade and a broad spectrum of PFAS including PFOA, PFOS, and short-chain PFAS. The plasma reactor can simultaneously oxidize and reduce organics by producing a mixture of OH radicals and aqueous electrons, the latter of which act as strong reducing agents and are the key species in removing PFAS and other non-oxidizable compounds. Additionally, the plasma process requires no chemical additions and produces no residual waste, although in some applications surfactants are added to enhance short and ultrashort chain removal. The enhanced contact electrical discharge plasma reactor (ECo-PRe™) uses multipoint gas discharges for the generation of plasma. Gas diffusers are positioned on the bottom of the reactor and argon gas is continuously pumped through the diffusers producing bubbles and forming a layer of foam on the liquid surface. This foam concentrates PFAS and enhances the contact between the liquid and the plasma, exposing the PFAS at the interface to reactive species in the plasma.
Results/Lessons Learned
The trailer had the capability to operate at flowrates of up to 10 gallons per minute, with the ultimate objective of degrading both long- and short-chain PFAS. Under the optimal operating conditions, the concentrations of PFOA and PFOS following the treatment decreased to below the detection limits of the instrument with the majority of C6 PFAS and perfluoroalkyl acids (PFAA) degraded. The treatment concurrently resulted in a significant reduction in the concentration of total organic fluorine. The work will present the trailer design and discuss the overall effectiveness of the plasma process in degrading PFAS and PFAS precursors. The impact of operational parameters on the treatment, treatment costs and implementation challenges will also be discussed.