Dr. Thomas is a member of the Innovative Technology Group (ITG) at GHD based in Niagara Falls, New York. He has helped develop per and polyfluoroalkyl substances (PFAS) fact sheets and technical regulatory guidance for Interstate Technology and Regulatory Council (ITRC). He has provided guidance on acceptable and prohibited items in addition to helping to establish GHD PFAS sampling protocols. Ryan is leader to GHD’s North American Emerging Contaminants Work Group and co-leader to ITRC’s Fate and Transport, Physical and Chemical Properties, and Site Characterization subgroup. Within ITG, Ryan leads research and development studies towards PFAS removal and destruction technologies.
Laboratory Treatability Studies for PFAS-impacted Water
Ryan Thomas (GHD), Fred Taylor (GHD), Sophia Dore (GHD), Peter Nadebaum (GHD), Donald Pope (GHD), and Jennifer Wasielewski (GHD)
Per- and Polyfluoroalkyl substances (PFAS) are a class of anthropogenic compounds that are commonly found in drinking water, surface water, groundwater, soil, and landfill leachate. The USEPA has a health advisory limit of 70 ng/L for perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) for drinking water while some states have more conservative action levels. Treatment technologies to destroy PFAS are not proven effective or economic, while technologies that remove PFAS from waste streams are generally fully demonstrated. Numerous challenges are associated with PFAS sampling, analytical detection, and remediation. Innovative remediation technologies are necessary to provide options for PFAS treatment, particularly at complex sites where other contaminants are present and can inhibit treatment by competing for binding sites or reagents. The most common current technologies for PFAS treatment in water and leachate involve sorption of the PFAS onto media such as activated carbon or ion exchange resin creating a waste stream that must be further treated (e.g., thermal regeneration). Alternate technologies that destroy PFAS are currently being investigated. This presentation will provide a strategic overview of existing, novel, and integrated remediation technologies, along with the associated challenges and risks that need to be managed to deliver a successful project addressing short- and long-term performance and effectiveness. Results from bench-scale studies involving activated carbon, ion exchange resin, and advanced oxidative and reductive treatments will be evaluated and compared in terms of feasibility, effectiveness, and economics. One study has shown that PFOA and PFOS concentrations were significantly reduced after a low pH ozonation pre-treatment followed by an alkaline pH ozonation (Lin et al., 2012). Our study is evaluating the removal of PFOS, PFOA and other PFAS, as well as the effect of treatment time, and the formation of degradation products. In our work photo-oxidation methods for PFAS treatment in water are being investigated using persulfate under low pH conditions, and reductive methods using potassium iodide and humic acid. These and other destructive technologies are important since the ultimate way to mitigate associated risks is to breakdown these compounds to less bioaccumulative and persistent compounds. Design considerations being explored in the studies include length of contact time required in order for adequate PFAS treatment, the destruction mechanisms occurring with various oxidants and reducing agents, PFAS residuals, and water quality requirements for effective treatment.