The objective of this project is to develop and optimize an effective approach to treat per- and polyfluoroalkyl substances (PFAS) present in landfill leachate. The core concept of this technology will be to concentrate all PFAS using foam fractionation, and then test several different approaches, including electrochemical oxidation, sonolysis, plasma, and hydrothermal alkaline treatment, to destroy PFAS in the concentrate. Different oxidative steps will be evaluated after foam fractionation but prior to PFAS destruction to transform polyfluoroalkyl substances to more manageable perfluoroalkyl acids (PFAA). Elevated salinity and dissolved organic carbon levels typically present in leachates substantially limit the effectiveness of currently employed PFAS treatment technologies such as activated carbon, anion exchange resin, and filtration. Thus, the goal of this project is to provide a cost-effective solution for destructive PFAS treatment in the complex matrices that comprise landfill leachates.
This project will be executed via five main tasks. The initial task will entail characterization of leachates that will be utilized during the testing. All studies will be conducted with real leachates. Task 1 will entail analysis of each leachate for well characterized PFAS and for hundreds of other non-targeted (i.e., suspect) PFAS. The total oxidizable precursor assay also will be used to estimate total PFAS. The second task will assess concentration of PFAS from leachate via foam fractionation using a laboratory scale fractionation system. A number of different variables will be tested including (1) surfactant type and concentration; (2) influence of bubble size; (3) sparge intensity; and (4) overall sparge time. The types of surfactant (cationic, anionic, or both) required to improve stripping of short-chained compounds will be evaluated. Task 3 will be designed to evaluate approaches to pre-oxidize PFAS in leachate concentrate to primarily PFAA, a step that may improve the efficiency of subsequent PFAS destructive treatments. Task 4 will assess the ability of several different existing PFAS destruction technologies to treat the leachate concentrate from the fractionation process, including electrochemical oxidation, sonolysis, plasma, and hydrothermal alkaline treatment. Finally, in Task 5 treatment efficacy with and without PFAS pre-oxidation will be documented, and an analysis will be conducted to quantify the benefits (in terms of overall cost, energy requirements, and PFAS defluorination) of oxidizing the concentrated leachate prior to implementing destructive technologies.
The key benefit of this project will be to provide the Department of Defense, municipal, and commercial landfills with a cost-effective approach to remove PFAS from leachate. Solutions are required to prevent further environmental distribution of PFAS and subsequent liability, as leachates are often discharged to wastewater treatment plants, impoundments, wetlands or soils.