Possibilities of using a corona electric discharge generator in the processes of water and surface sterilization
Authors: Kuzina E.D. , Ivanova I.P. , Piskarev I.M. 
Published: October 2024

The work is devoted to the use of an electric discharge in the geometry of a point electrode – a plane surface for the sterilization of water and surfaces contaminated with bacteria. The relationship between the concentrations of oxidizing impurities and active species generated in an electric discharge is discussed. It is shown that if the concentration of active species is too high, they will interact predominantly with each other and die without producing any effect. Using the example of cyanide decomposition, it is shown that the highest decomposition efficiency is achieved at the maximum voltage on the discharge electrode and the minimum electric discharge current. Therefore, a corona electric discharge was chosen for work. In a corona electric discharge generator in air in the presence of water vapor, an ozone-hydroxyl mixture is formed, in which the lifetime of hydroxyl radicals is ~ 1 sec. This makes it possible to extract hydroxyl radicals from the discharge cavity and ensure their contact with the water flow. After treatment in the generator, the water is purified from impurities within the limits allowed by the release of active species concentration, saturated with ozone and air oxygen to the solubility limit at a given water temperature, and becomes oxygenated. For the experiments, a prototype of the corona electric discharge generator was made. The voltage applied to the discharge electrodes was minus 11 kV, and the total discharge current was 1.7 mA. The choice of parameters of the electrical circuit that forms and maintains the corona discharge is analyzed. The bactericidal effect of the generator was determined for a liquid contaminated with bacteria and for a contaminated surface. The bactericidal effect of the liquid was evaluated after passing it through the reactor of the corona discharge generator. Water flow 150 L/h. The energy costs for reducing CFU (Coli Forming Units) by 10 times for an aqueous solution containing the bacteria Escherichia coli, Enterobacter cloacae, Pseudomonas aeruginosa, Enterococcus faecalis at a concentration of 10–103 CFU per 100 ml of solution are 59±6 J/100 ml of solution for each type of bacteria. Surface sterilization was carried out by spraying the contaminated surface with water after its treatment in the generator reactor. The area of contaminated samples was 25 cm2. To reduce CFU by 10 times on a surface contaminated with gram-negative bacteria Escherichia coli and gram-positive bacteria Staphylococcus aureus at a concentration of 104 CFU/cm2, an energy of 100±11 J/cm2 was expended. High energy costs for surface sterilization are associated with the inefficient use of oxygenated water in this experiment, since the water was drained from the surface without losing its activity. Water retains noticeable activity up to 4 hours. Thus, the water produced by the generator can disinfect large surfaces, which will significantly reduce energy costs. For comparison, the solution was disinfected with UV radiation by irradiation in a Petri dish. A DKB-9 low-pressure mercury lamp emitting 253.7 nm photons was used. The energy spent on reducing CFU by 10 times was 1.6±0.2 and 0.7±0.1 J/cm2 for Staphylococcus aureus and Escherichia coli, respectively. The advantage of decontamination with oxygenated water is that contaminated objects can be washed from all sides, which is not possible using lamp radiation. The results obtained make it possible to calculate the modes of sterilization of a liquid and a contaminated surface using a corona discharge generator and oxygenated water depending on the concentration of microorganisms. Oxygenated water is an environmentally friendly disinfectant, since the active species formed during the generator treatment break down into water and oxygen over time.