Sterilization Mechanism of Escherichia Coli in Highly Conductive Aqueous Solution by Dielectric Barrier Discharge Treatment Using a Water Column Electrode

This paper describes the sterilization mechanism of Escherichia coli in highly conductive aqueous solution by dielectric barrier discharge (DBD) using water column electrode. NaCl aqueous solution, (NH
4
)
2
SO
4
aqueous solution are used as a hydroponic culture simulated solution for agriculture. E. coli DH10B is suspended in the aqueous solution at a concentration of 10
⁷
CFU/ml. 100 ml of the bacteria-containing aqueous solution is circulated by a micro pump. A thin water-column spraying from the pump nozzle is used as a ground electrode (water column electrode). DBD occurs between the water column electrode and the glass-coated rod electrode. The number of viable bacteria in the discharged aqueous solution is measured using the colony counting method. The viable E. coli ratio does not changed in the both aqueous solutions without the discharge treatment. In the NaCI aqueous solution, the viable ratio decreases with increasing discharge treatment time and increasing concentration. In the case of the (NH
4
)
2
SO
4
aqueous solution, the viable E. coli ratio is constant until the treatment time attain the critical value, but then it is exponentially decrease after the critical time. This means that the sterilization of E. coli in the (NH
4
)
2
SO
4
aqueous solution is produced after a formative process, such as changing in pH of water by the discharge treatment.