Steady-State Corona Discharges in Atmospheric Air for Cleaning and Decontamination

It is shown that high-voltage corona discharges in atmospheric air have significant potential for bacterial inactivation. Neutral reactive oxygen and nitrogen species and ions generated by the corona discharges act upon the target liquid or solid surfaces and produce chemical or biological effects. The concentration of ions and reactive species including ozone generated by these discharges defines the efficiency of the corona treatment. In this paper, the chemical (oxidation) effect of direct corona discharges (where ions act upon the target surface) and indirect corona discharges (where ions are screened by a grounded metallic mesh) in atmospheric air is studied by measuring the degree of decolorization of a blue dye dissolved in water. The biological effects of the direct and indirect discharges are studied by observing the degree of bacterial inactivation of gram-negative and gram-positive microorganisms, Escherichia coli and Staphylococcus aureus, seeded on agar plates. The relationship between the ozone concentration and biological efficiency of the corona treatment is evaluated. The obtained results can be used for optimization of cleaning and inactivation treatment processes based on the use of nonthermal plasma produced under dc energization conditions.