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The ability of a GA discharge to produce hydrogen peroxide (H 2 O 2 ), a potent oxidizer, was investigated to evaluate the optimum operational condition of the GA discharge for bacterial inactivation. The concentration of H 2 O 2 was measured in liquid phase, and its effective residual time was evaluated in a 200-W GA discharge system at different air and water flow rates. The concentration of H 2 O 2 was the highest at the least water flow rate. In addition, a 5-log reduction in the colony forming unit (cfu) number of E. coli was observed at a H 2 O 2 concentration of 100 mg/L in water.

The efficacy of gliding arc (GA) discharge for the generation of hydrogen peroxide (H2O2) and water with a low pH was studied because H2O2 combined with low-pH environment is known as a strong oxidizer that can be used for the bacterial inactivation. The ability of the GA discharge to inactivate Escherichia coli in water was tested experimentally, and the inactivation was found to increase with the plasma treatment time and rate of water injection flow to the GA discharge system. The best result showed a 2-log reduction of the number of colony-forming units of E. coli from 104 to 102 at a water injection flow rate of 180 mL/min. Furthermore, pH in the plasma-treated water was decreased from 6.0 to 3.55 after 25

The objective of the present study was to investigate the feasibility of stretching an arc discharge in produced water to increase the volume of produced water treated by plasma. Produced water is the wastewater generated by hydraulic fracturing of shale during the production phase in shale-oil or shale-gas exploration. The electric conductivity of produced water is in the range of 50-200 mS/cm, which provides both a challenge and opportunity for the application of plasmas. Stretching of an arc discharge in produced water was accomplished using a ground electrode and two high-voltage electrodes: one positioned close to the ground electrode and the other positioned farther away from the ground. The benefit of stretching the arc is that the contact between the arc and water is significantly increased, resulting in more efficient plasma treatment in both performance and energy cost.