Investigation Of Dying Wastewater Decolorization By Bipolar Pulsed Discharge

Water treatment by the direct electrical discharge in aqueous solutions is an innovative advanced oxidation technology of water treatment. A nonthermal plasma is produced during the discharge processes where a large amount of high energy electrons, active species (such as active radicals and molecules etc.) are generated. Those active species directly react with organic molecules dissolved in water and oxidize them or even get them completely mineralized. This technology has such advantages as high removal efficiency, nonselective, without secondary pollution and etc., and exhibits promising application perspective. And recently it has been one of the research issues in the water treatment field.Decolorization of the dying wastewater by the bipolar pulsed discharge in water-air mixture and solid-liquid-air mixture are proposed in this paper and two novel discharge water treatment systems have been designed, discharge characteristics of each system have been diagnosed. Water treatment performance of these systems has been investigated with Indigo Carmine (indigo-5, 5'-disulphonic acid, IDS) and Amaranth (Acid Red 27, AR27) served as target pollutants. In addition, inactivation performance of E.Coli in the three phase discharge reactor has been tested.The main contents and the research results are as follows:1. Match relationships between the bipolar pulsed power supply and the water-air mixture and also air-liquid-solid mixture discharge reactor have been investigated. Experimental results show that the bipolar pulsed power supply matches the reactor when the capacitance of the pulse capacitor Cp equals 3-10 Cr.2. Electrical and spectral diagnosis methods have been used to study the electrical discharge characteristics of the water-air mixture and also the solid-liquid-gas mixture. Effects of the peak to peak voltage, air flow rate and the initial solution conductivity on the electrical discharge characteristics have been studied. Experimental results show that electrical discharges in the water-air mixture and the air-liquid-solid mixture increases with the increase of the peak to peak voltage and the pulse repetitive rate, decreases with the increase of the solution conductivity. The electrical discharge increases quickly as the air flow rate increasing from 0 to 0.75m3/h, and the increase becomes slow when the air flow rate increase further.3. Removal of the indigo carmine in the water-air mixture discharge reactor has been investigated. Effects of the gap distance, parameter characteristics of the bipolar pulsed powersupply and the physical characteristics of the water solution have been studied. Experimental results show that color removal efficiency of IDS in the reactor increases with the increase of the peak to peak voltage and the pulse repetitive rate, decreases with the increase of the gap distance, the initial solution conductivity and initial solution concentration.4. Influence of different solid packing on the electrical discharge characteristics and the formation of the chemically active species in the solid-liquid-gas three phase discharge plasma reactor initiated by a bipolar pulsed power were studied. Experimental results show that addition of solid packing into the water-air two-phase discharge plasma reactor enhances the electrical discharges and chemical processes in the reactor. Concentrations of the gas phase ozone and liquid phase ozone and hydrogen peroxide increase greatly after the solid particles are packed into the reactor. Dielectric properties of the packing materials determine the degree of enhancement. Water treatment performance of the reactor with dielectric spheres is much better than that with conducting materials for the same experimental conditions. In addition, dielectric glass beads have stronger influence on the chemical enhancement process than ceramic spheres.5. Degradation of the azo dye amaranth in the three phase discharge reactor has been investigated. Effects of such parameters as gas flow rate, solution conductivity, pulse repetitive rate and etc., on color...