Reactive Electrochemical Membrane (REM) Reactors for the Oxidation of Perfluoroalkyl Compound Contaminated Water
Brian Chaplin | University of Illinois at Chicago
Perfluoroalkyl substances (PFASs) are prevalent contaminants in the groundwater at Department of Defense (DOD) sites. These compounds were contained in aqueous film forming foams (AFFFs), which were used to suppress fires at hundreds of DOD sites. PFASs pose a serious human health risk, and thus the US Environmental Protection Agency has issued a drinking water health advisory level of 70 ng L-1 for six PFAS compounds. As a result, there has been extensive investigations of groundwater contamination at DOD sites, which generates a large volume of waste containing PFASs, which is termed investigation derived waste (IDW). PFAS removal from water is complicated by low volatility, general lack of reactivity to biodegradation and traditional oxidative treatment processes, and poor desorption kinetics from granular activated carbon and other sorbents. Therefore, novel and effective remediation technologies are needed to treat PFAS-contaminated IDWs, which would allow for on-site disposal options that would lower the overall cost of site management.
The overall objective of this work is to utilize a cost-effective reactive electrochemical membrane (REM) for the remediation of PFASs in IDWs. Specific technical objectives associated with this work include: 1) development of REMs for destructive PFAS removal in IDW water samples; 2) determination of the optimal operational mode; and 3) calculation of energy requirements for the REM-based system and comparison to those determined for granular activated carbon adsorption and other technologies.
The research team will be investigating the technical and economical feasibility of using REMs for treating IDWs containing PFASs. The REM is a novel electroactive membrane made of porous Ti4O7 with micron-sized pores. Anodic polarization of the REM results in degradation of PFASs through a combination of direct electron transfer reactions and reactions with hydroxyl radicals that are generated from water electrolysis. The small pore size and operation in flow-through mode allows for very fast mass transfer, and thus complete elimination of organic compounds in a single pass through the REM.
The work plan consists of REM synthesis, a series of bench-scale experimental studies that will determine optimal operating conditions for PFAS oxidation in groundwater samples, and a preliminary cost assessment. Experimental parameters that will be explored include: 1) adsorption capacity; 2) necessary residence time in the reactor; 3) needed membrane surface area per groundwater volume treated; and 4) energy usage (kWh/m3 water treated). The work is projected to end with proof of concept data that will determine if the REM is suitable for treatment of PFAS-contaminated IDW solutions.
The successful completion of this project will have numerous benefits to DOD and the scientific community. These expected benefits include 1) a better understanding of the use of electrochemical technologies for groundwater remediation; 2) the generation of proof of concept data that can be used to develop a field-scale prototype REM for the remediation of PFAS-contaminated groundwater; and 3) an energy cost assessment for using the REM technology at contaminated sites, which can be used by practitioners to assess the REM technology as a viable remediation option. (Anticipated Completion - June 2019)