Pulsed Corona Discharge in Water Treatment: The Effect of Hydrodynamic Conditions on Oxidation Energy Efficiency

Water treatment by gas-phase pulsed corona discharge (PCD) relies mainly on utilization of ozone and OH radicals as oxidizing agents. In a configuration where the treated solution is showered through the plasma zone, the gas-liquid contact surface is the primary OH-radical formation site and the interface in the mass transfer of ozone. Its significance to overall process efficiency is therefore notable. In this study, the effect of varying contact surface area at different discharge powers was investigated from the perspective of efficient utilization of the two prime oxidants in slow reaction with oxalate. It is seen that increasing the area of the contact surface improves OH-radical utilization up to the point where the pollutant oxidation efficiency abruptly decreases presumably because of unfavorable pulse energy distribution in the gas-liquid mixture. The existence of an optimal area for a given power has implications for future studies in the design of pulsed plasma applications for water treatment.