Degradation of Per-and Polyfluoroalkyl Substances (PFAS) from Water Using Thermal Plasma Arc Discharge

Per- and polyfluoroalkyl substances (PFAS) are contaminants of emerging concern in the United States and worldwide. They have been used in a wide variety of household and industrial applications, including firefighting foams, and have found their way into the groundwater contaminating our drinking water supplies. Extremely high levels of these contaminants are also prevalent at many DoD sites. This project proposes to investigate a new approach to degrade PFAS simultaneously by exploiting a thermal plasma arc discharge system. The plasma arc discharge is submerged in water to create ions and free electrons by sustaining a current of many hundred amperes through the water. The interaction of plasma discharges with water creates multiple phenomena that have applications in water treatment. These include the generation of chemically active components including hydroxyl radicals, hydrogen peroxide, ozone and other active compounds, energetic electrons and ions, UV light, ultrasound waves and cavitation, and more. Since these phenomena are created simultaneously the effectiveness of each can be much higher and lead to synergistic contributions from short-living active species, charged particles and UV light. Solvent electrons seem to be effective in breaking the highly stable C-F bonds in PFAS. In a preliminary study we have seen PFAS to degrade at significant levels when exposed to a thermal plasma arc discharge in water. The goal of this project will be to evaluate the effectiveness and the technologic feasibility of the process for degrading contaminants like PFAS, for water purification and reuse. The submerged thermal plasma arc approach is scalable with no impact to the environment that can be easily adapted for point-of-use implementation by residential communities. Sustainable access to drinking water is a major public health issue and thus one of the great challenges for the 21st century. Over development, inadequate management of wastewater, climate change, and seasonal variation of weather make fresh water a scarce commodity. One obvious path to overcome this issue is to reuse water. However, to be reused in a meaningful way requires processing wastewater with advanced water treatment technologies. Of alarm are emerging contaminants of micropollutants from household products and industrial applications, like PFAS, that are not removed by conventional means and for which the health impact is not well understood.