The aim of this work is to investigate the effects of a point-plane plasma reactor electrode design on the inactivation rate of E. coli (model microorganism) in water and the effects of electrode material on the inactivation rate in both direct plasma and post-plasma inactivation processes. For electrode design experiments, the inactivation rates associated with various combinations of electrode gap distance and ground electrode size were compared. Electrode gap distance and ground electrode size did not significantly impact the rate of E. coli inactivation; however, there existed an effective inactivation region in the reactor. For electrode material experiments, nickel chromium alloy, iron, copper, and silver were used as high voltage (HV) electrodes. An 8-log decimation of E. coli was achieved in three minutes with silver or copper as the HV electrodes, and was hypothesized to be associated with toxicity of metallic ions and nanoparticles (NPs) released from the electrodes during treatment. Significantly lower inactivation of E. coli was achieved for the nickel chromium or iron HV electrodes. Post-plasma inactivation experiments were conducted to test this hypothesis. Plasma activated water (PAW) was generated in the reactor without E. coli by discharging plasma into phosphate-buffered saline. Copper, silver, or tungsten (an inert material) were used as HV electrodes. After treatment, E. coli were added to PAW and left to react. Results suggest that the disinfection efficacy of PAW is significantly enhanced by the release of copper and silver ions and NPs, in comparison with the control experiment (tungsten case). This new type of PAW, which can be prepared in a simple manner, is a promising novel bactericidal solution.

Inactivation of E. coli by direct-in-liquid electrical discharge plasma: Effects of reactor electrode design and high voltage electrode material

256th National Meeting (2018)

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