Improvement of efficiency for decomposition of organic compound in water using pulsed streamer discharge in air with water droplets by increasing of residence time

Water treatment using pulsed streamer discharge in water is studied currently, because the pulsed streamer discharge in water generates active species that decompose organic compounds in water. However, the system for generating streamer discharge in water needs big pulsed voltage supply for applying high voltage and high power, because the breakdown electric field of water is high. To solve this problem, we have studied the method spraying water droplets into discharge space in air whose breakdown electric field is lower than that in water, and have demonstrated that the method can decompose organic compounds faster in low energy consumption. In this paper, to obtain higher decomposition rate by increasing of residence time of water in the discharge space has been investigated. Two types of reactors were designed for increasing the residence time of water in discharge space in air. One of the reactors has pellets packed into a cylindrical electrode, and another has fluorocarbon wires weaving like many cobwebs into the cylindrical electrode. For 60 minutes treatment, the treatment rate of the reactor with packed bed of the pellets was 40 % lower than that without the pellets because the discharge space was narrow by the pellets. In contrast, for the 10∼60 minutes treatment, the treatment rate of the reactor weaving the fluorocarbon wire was 2∼10 % higher than that without the fluorocarbon wire. This is because the treated water was exposed to more streamer discharges by increasing of the residence time of water droplets and maintaining the discharge space size without the fluorocarbon wire.