Effects of coaxial dielectric barrier discharge system on water treatment by water stream well mixed with air

Non-thermal plasma excited by pulsed strong electric fields can generate a large number of oxidants in water such as ozone, hydrogen peroxide and hydroxyl radicals. These active species play an important role on water treatment. In this paper, a water treatment processing system was constructed by means of pulsed dielectric barrier discharge with water stream well mixed with air. Coaxial structure was adopted in the plasma reactor. The downward water stream and the upward air flow up were well mixed. Degradation of indigo carmine solution was attempted by this system. The effects of discharge time, discharge peak voltage and frequency were studied. The ability to produce hydrogen peroxide and ozone was also investigated for the entire system. The energy efficiency factor, defined as the ratio between the energy for degradation of organic matter and the total input energy, is proposed. The experiments show that the indigo carmine solution with the initial concentration of 250 mg/L was 100% degraded in 10 minutes at the voltage of 25 kV and frequency of 200 Hz. The max energy efficiency factor was 40.2%.