Effect of discharge gas on water treatment using nanosecond pulsed power discharges

Abstract

Nowadays, water pollution is one of the environmental problems. We have studied a sewage treatment using nanosecond pulsed power discharges. The water treatment utilizes not only active species such as hydroxyl radical produced by electric discharges but also direct actions of discharges such as ultraviolet rays, shock wave and so on. In order to reduce the costs for treatment, treatment using air gas as a discharge gas was studied. The treatments using streamer discharges in simulated air gas, consisting of 20 % oxygen and 80 % nitrogen, and oxygen gas were evaluated. The surfactant treatment was assessed by the height of foam in the reservoir, which was one of the characteristics. The treatment by oxygen as discharge gas continued to reduce the height of foam in reservoir for 80 minutes treatment. On the other hand, the foam decreased rapidly for 0–20 minutes treatment. Under the presence of NO2, height of foam decreased rapidly because of increasing OH radical production. However, after 20 minutes, decrease of height of foam became slow because OH radical was consumed oxidizing NO2.