Degradation and removal of environmental contaminants in water using high energy electrons and radicals

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The following results were obtained as the research from 1999 to 2001 fiscal years.(1) In low conductive water, two-step breakdown in the development of the total electrical breakdown in water were observed. The existence of this regime was limited by the water conductivity, applied voltage, and capacitance of the storage capacitor. The distortion of the electric field at the head and an increase of the leader channel resistance due to accumulation of the electrostatic charge on inside wall of the gaseous channel were most likely two mechanisms effective in the transient regime.(2) With changing electrode gap distance, three discharge modes were observed, i.e. streamer, spark with streamer, and spark discharges. The formation of active species and ultraviolet radiation, which are important chemical species and physical effects for degradation of organic pollutants were strongly dependent on the discharge mode.(3) It was found that the discharge modes, gas bubbling and chemical additives affected the degradation of phenol and dyes. In the case of streamer discharge, hydroxyl radicals were considered to be the dominant process. In the case of spark and spark with streamer discharge mode, the other physical effects such as shockwave and ultraviolet radiation may take place on the degradation process besides the hydroxyl radicals.(4) A large volume streamer corona discharge was generated around the ring electrode, and the discharge formation was greatly dependent on the electrode geometry, polarity and the water conductivity. It was found that the insulation technique of the ring electrode was the most important factor for decrease streamer initiation voltage.