Surface-wave-sustained plasma torch for water treatment

Abstract

In this study the effects of water treatment by surface-wave-sustained plasma torch at 2.45 GHz are studied. Changes in two directions are obtained: (i) changes of the plasma characteristics during the interaction with the water; (ii) water physical and chemical characteristics modification as a result of the plasma treatment. In addition, deactivation of Gram positive and Gram negative bacteria in suspension are registered. A number of charged and excited particles from the plasma interact with the water. As a result the water chemical and physical characteristics such as the water conductivity, pH, H₂O₂ concentration are modified. It is observed that the effect depends on the treatment time, wave power, and volume of the treated liquid. At specific discharge conditions determined by the wave power, gas flow, discharge tube radius, thickness and permittivity, the surface-wave-sustained discharge (SWD) operating at atmospheric pressure in argon is strongly non-equilibrium with electron temperature T _e much higher than the temperature of the heavy particles (gas temperature T _g). It has been observed that SWD argon plasma with T _g close to the room temperature is able to produce H₂O₂ in the water with high efficiency at short exposure times (less than 60 sec). The H₂O₂ decomposition is strongly dependant on the temperature thus the low operating gas temperature is crucial for the H₂O₂ production efficiency. After scaling up the device, the observed effects can be applied for the waste water treatment in different facilities. The innovation will be useful especially for the treatment of waters and materials for medical application.