Influences of discharge modes and gas bubbling conditions on E. coli sterilization by pulsed underwater discharge treatments

Underwater discharges are considered to be promising solutions to water disinfection problems. In this paper, the sterilization effects of different discharge modes and gas bubbling conditions on E. coli are investigated. The experimental results show that spark discharge owns a much higher sterilization efficiency than the streamer discharge. The larger discharge volume and stronger UV emission during spark discharge may play a more important role than the electric field and active species in the sterilization efficiency of discharge modes. To further increase the sterilization efficiency, two kinds of feeding gases, O2 and Ar, are introduced in underwater discharges, and experimental results show that O2 bubbling presents a greater promotion than Ar. Higher sterilization efficiency of O2 bubbling than that of Ar can be explained by the combination of physical and chemical reactions, while in the case of Ar, only physical interactions play a major role.