Li Zhongjian

Characteristics of Electrode-Water-Electrode Discharge and its Application to Water Treatment

Atmospheric air discharge above the surface of water is an effective method for water treatment. The leakage current and Joule heating of water are reduced by the air gap, which raises the energy efficiency of the water treatment. However, the application of this kind of discharge is limited by a pair of conflicting factors: the chemical efficiency grows as the discharge gap distance decreases, while the spark breakdown voltage decreases as the gap distance decreases. To raise the spark breakdown voltage and the chemical efficiency of atmospheric pressure water surface discharge, both the high-voltage electrode and the ground electrode are suspended above the water surface to form an electrode-water-electrode discharge system. For this system, there are two potential discharge directions: from one electrode to another directly, and from the electrodes to the water surface. The first step in utilizing the electrode-water-electrode discharge is to find out the discharge direction transition criterion. In this paper, the discharge direction transition criterions of spark discharge and streamer discharge are presented. By comparing the discharge characteristics and the chemical efficiencies, the discharge propagating from the electrodes to the water surface is proved to be more suitable for water treatment than that propagating directly between the electrodes.

Inactivation of Bacteria in Oil Field Injected Water by a Pulsed Plasma Discharge Process

Pulsed plasma discharge was employed to inactivate bacteria in the injection water for an oil field. The effects of water conductivity and initial concentration of bacteria on elimination efficiency were investigated in the batch and continuous flow modes. It was demonstrated that Fe2+ contained in injection water could enhance the elimination efficiency greatly. The addition of reducing agent glutathione (GSH) indicated that active radicals generated by pulsed plasma discharges played an important role in the inactivation of bacteria. Moreover, it was found that the microbial inactivation process for both batch and continuous flow mode well fitted the model based on the Weibulls survival function.