The Effects of Water Conductivity on the Plasma Properties and Performance of a Plasma-Water Reactor for the Decomposition of Per- and Polyfluoroalkyl Substances

A plasma-water reactor featuring water dielectric barriers is being developed for the decomposition of per- and polyfluoroalkyl substances (PFAS). Experiments have shown that the reactor is capable of decomposing PFAS in contaminated groundwaters to below regulatory maximum contaminant levels. During the treatment process, the water conductivity increases as charged species from the plasma are transferred to the water. Using optical emission spectroscopy, the plasma density and gas temperature are determined as a function of the water electrical conductivity. Electrical and temperature diagnostics are used to investigate how the water conductivity affects the discharge voltage, discharge current, deposited power, and the fraction of power that goes into heating the water. Implications of these changes in plasma discharge properties are considered in the context of PFAS decomposition efficiency.