Increasing Water Conductivity Research Articles

The effect of conductivity on streamer initiation and propagation between dielectric-coated sphere-plate electrodes in water

A dielectric-coated sphere-plane electrode system was designed and used for the generation of streamer discharges in water. To study the streamer initiation and propagation mechanisms, the effect of conductivity was investigated under pulse voltage. Increasing water conductivity caused the decrease of streamer initiation voltage and streamer formation time delay. Under the same applied voltage, the maximum streamer length was inversely proportional to water conductivity, whereas the streamer brightness was proportional to the water conductivity. The mean streamer velocities were dramatically different with different water conductivity and the influences of interactions between streamer branches on the streamer propagation were inevitable under high applied voltage. Based on the analyses of these experimental results, it can be concluded that streamer initiation in water is triggered by the microgap breakdown in the coating while streamer propagation may be a gaseous or electronic process, which is dependent on applied voltage and water conductivity.

Ultraviolet radiation from the pulsed corona discharge in water

Quantitative analysis of ultraviolet radiation from the pulsed corona discharge in water with needle-plate electrode geometry (∼1–3 J pulse−1) was performed using the potassium ferrioxalate actinometry. Photon flux J190–280 and radiant energy Q190–280 of the UV light emitted from the discharge at spectral region 190–280 nm was determined in dependence on the applied voltage (17–29 kV, positive polarity) and the solution conductivity (100–500 µS cm−1). The intensity of the UV radiation strongly increased with increasing water conductivity and applied voltage. Depending on the applied voltage the determined photon flux varied by more than two orders of magnitude within the range of solution conductivities 100–500 µS cm−1. It was found that photon flux from the discharge may be directly related to the discharge pulse mean power Pp as J190–280 = 44.33 (quanta pulse−1). A significant role of UV radiation in the production of hydrogen peroxide and bacterial inactivation by the corona discharge in water has been identified. As the solution conductivity increased the yield of H2O2 produced by the discharge decreased due to increasing photolysis of H2O2 accounting for up to 14% of the total decomposition rate of H2O2. As regards bactericidal effects, it was estimated that the UV radiation contributes about 30% to the overall inactivation of Escherichia coli.