Sterilization of E. coli by underwater pulsed streamer discharges in a continuous flow system

Underwater pulsed streamer discharges using a wire‐to‐cylinder electrode contained in a 42‐mm‐diameter glass tube were investigated with respect to its spatial spread associated with voltage waveforms. A discharge reactor with a continuous flow system was employed to sterilize E. coli suspended in saline water (10 mS/m). The discharge electrode consisted of a 0.1‐mm‐diameter metal wire for the high voltage and a mesh cylinder for the ground electrode. Tens of disk‐shaped discharges emerged from the wire electrode and propagated toward the cylinder as long as the voltage lasted. The spatial expanse of the discharge was proportional to the cube of the pulse duration and to the amplitude of the voltage. The sterilization experiment showed that the survival ratio of bacteria over discharges was proportional to the average number of the exposures to the discharges while in the reactor. The minimum ratio of surviving bacteria was only 15% under 130 exposures, which corresponds to an energy expenditure of 35 J/ml.