A Compact Plasma Flow-Bubbler for Decomposition of Organic compounds and Sterilization

Recently, Plasma production in and in contact with liquid has attracted much attention because of their applications to degradation of organic compounds, sterilization, water purification. UV, electron, ion and radical flows originated from a plasma and also shock wave induce physical and chemical reaction in a liquid, for example oxidation-reduction, electrolysis and reactive species production in a water. In particular, various reactive oxygen/nitrogen species generated at the plasma-liquid interface play an important role in oxidation and degradation of organic pollutants and bacteria. We have proposed the mild water treatment by ejecting the atmospheric-pressure $\mu$plasma (AP$\mu$P) flow into a water using a microbubble aerator or a porous ceramics bubbler. In this study, a compact plasma flow-bubbler made up of a $\mu$plasma source and a porous ceramics has been developed for the applications of water purification and sterilization. AP$\mu$P is generated between a thin metal pipe electrode and a GND plate by a pulsed high voltage, so that the O$_{2}$ $\mu$plasma can be obtained without adding He and Ar gases. Plasma flow is ejected into the water through a porous ceramics. Decolorization of an indigo carmine solution strongly depended on O$_{2}$ flow rate. Chemical probe method using terephthalic acid revealed that OH radicals are produced by the O$_{2}$ plasma gas bubbling. The inactivation for \textit{E. coli}, \textit{Bacillus subtilis} was attained by the O$_{2}$ plasma gas bubbling.