Remediation of soils and groundwater impacted by per- and polyfluoroalkyl substances (PFAS) is particularly challenging due to the strength of the carbon-fluorine bond and the need to achieve extremely low drinking water levels. Currently, PFAS-impacted groundwater is managed using conventional “pump and treat” remediation approaches that rely on extraction and above-ground treatment with granular activated carbon (GAC) or ion exchange resin (IXR). However, the cost of GAC and IXR can be exorbitant, especially for pump and treat systems that may be operational for long periods of time. One potential approach to extend the lifetime of GAC or IXR and reduce costs is dissolved air flotation (DAF), which could be applied as a pre-treatment technology to remove PFAS due to their strong tendency to accumulate at the air-water interface. Although DAF holds promise as a cost-effective treatment technology for PFAS-impacted waters, low removal efficiencies have been reported for short-chain PFAS. To overcome this limitation and make the technology more feasible, the objectives of this research project are to: (1) evaluate polymers and other additives to increase accumulation of short-chain PFAS at the air-water interface; (2) assess the ability of polymer(s) or combinations of polymers to remove PFAS from water using DAF; and (3) develop a mathematical model to predict PFAS removal and design DAF systems for pilot-scale testing.
The technical approach is divided into three main tasks: (1) evaluation of polymers to enhance PFAS accumulation at the air-water interface; (2) performance assessment of DAF for PFAS removal from groundwater; and (3) mathematical modeling for prediction and design of DAF systems for PFAS removal. The research program will couple laboratory-scale experiments (Tasks 1 and 2) with mathematical model development and implementation (Task 3) to advance the fundamental understanding of PFAS accumulation at the air-water interface and refine the use of this process to reduce the costs of treating of PFAS-impacted water. The experimental studies will involve measurements of PFAS accumulation at the air-water interface and bench-scale DAF studies conducted with aerated water columns. The resulting experimental data will be used to develop and validate mathematical models, which can then be used to design DAF systems. The experimental findings and mathematical modeling tools will be disseminated to remediation practitioners, site managers, state and federal regulators, and the broader research community through journal publications, technical presentations at national and international conferences, webinars, and workshops.
The polymer-amended DAF process, if successful, will provide a cost-effective method to concentrate and remove a broad range of PFAS from groundwater, thereby by extending the life and reducing the costs associated with conventional GAC or IXR treatment technologies. Additionally, the polymer-enhanced DAF process could be coupled with destruction technologies to treat the PFAS concentrate. Key deliverables of this work include data on PFAS accumulation at the air-water interface, identification of polymers that improve DAF performance for short-chain FPAS, and mathematical modeling tools that can be used to predict PFAS removal from groundwater and design DAF systems. (Anticipated Project Completion - 2026)