Application of Ozone Generator in Space Sterilization

Ozone is a broad-spectrum and highly efficient disinfectant with strong oxidation and fast reaction rate, which has excellent disinfection and deodorization effects. Ozone has a significant killing effect on microorganisms in the air. When using 20mg/m3 concentration of ozone for 30 minutes, the killing rate of natural bacteria reaches over 90%. Currently, ozone sterilization is one of the recommended important sterilization methods in GMP in China.

2.1 Principle of Ozone Sterilization

The sterilization mechanism and process of ozone belong to biochemical processes, which oxidize and decompose the glucose oxidase necessary for the internal oxidation of glucose in bacteria. It can also directly interact with bacteria and viruses, damaging their organelles and ribonucleic acid, decomposing large molecular polymers such as DNA, RNA, proteins, lipids, and polysaccharides, and disrupting the metabolic production and reproductive processes of bacteria. It can also penetrate cell membrane tissue, invade the cell membrane and act on outer membrane lipoproteins and internal lipopolysaccharides, causing permeability distortion of cells and leading to cell lysis and death. And the genetic genes, parasitic strains, parasitic virus particles, bacteriophages, dendrites, and pyrogens (bacterial and viral metabolites, endotoxins) in the dead bacteria will be dissolved, denatured, and destroyed.

2.2 Advantages of Ozone Sterilization

(1) Has high diffusivity: O3 is a gas with good diffusion performance, no dead corners in the sterilization space, uniform concentration distribution in the space, and stable sterilization effect.

(2) The current "Disinfection Technical Specification" recognizes O3 as a broad-spectrum and highly effective fungicide: O3 has a good killing effect on various pathogenic microorganisms such as Escherichia coli, Salmonella, Staphylococcus aureus, hepatitis virus, fungi, etc. Scientific research has shown that O3 has a strong bactericidal and disinfectant effect, not only having a strong killing ability against various bacteria (including hepatitis virus, Escherichia coli, Pseudomonas aeruginosa, and other miscellaneous bacteria), but also effective against fungi. At present, there are no reports of O3 developing resistance to certain pathogenic microorganisms, overcoming the disadvantage of traditional chemical disinfectants developing resistance.

(3) After O3 disinfection, it naturally decomposes into O2, which is safe and residue free, and there is no possibility of secondary pollution.

(4) Only an ozone generator is needed, and the raw material is air. It only requires electricity for operation and is easy to operate.

(5) Sterilization at room temperature, with a wide range of applications.

For small car compartments, they can be separated or moved and placed in separate spaces. Generally, they should be placed at a high place because ozone has a higher density in the air and is prone to decrease. The main purpose of placing them at a high place is to facilitate the spread of ozone.

By using the circulating air of the HVAC system as the carrier of ozone, the ozone gas produced by the ozone generator is diffused to the entire clean area controlled by the pressure air source generated by the purification fan in the HVAC system, and the ozone concentration in the air is uniform. Without adding any disinfection equipment in the production environment of the clean area, the purpose of sterilization can be achieved. At the same time, it can also kill miscellaneous bacteria and mold in the HVAC system. Practice has found that this disinfection and sterilization method can also dissolve and guide bacteria in high-efficiency filters, extending their service life.

There are several methods for installing the ozone generator:

(1) Separate or mobile placement in a separate room (as mentioned above)

(2) Assembled in the air conditioning unit (this arrangement method usually installs the host after the medium efficiency filter or before the high-efficiency filter, but due to air pollution from the air conditioning supply, the ozone generator frequently malfunctions and cannot continue to operate, so this method is basically unnecessary)

(3) The ozone generator is placed outside the air conditioning unit, and the ozone pipeline is connected to the main air supply duct

Calculation method: When using the HVAC system for centralized dosing, the ozone generator should be selected according to the following method: first, calculate the actual ozone disinfection volume. The actual volume is divided into three parts: V=V1+V2+V3, V1 clean area space volume, V2 air purification system volume, and V3 air loss volume during circulation. In the actual calculation process, V3 is equal to 1.2% of the total air volume of the circulation system.

W=C*V/D

W: The actual output of the ozone generator used is in grams per hour;

V: Actual ozone disinfection volume;

D: The ozone depletion coefficient is 0.4208.

If the designed ozone concentration is 5ppm for airborne bacteria and the disinfection volume is 10000m3

Supply air flow rate 100000m3/h

V1=10000m3

V2=ignored

V3=100000*1.2%=1200

Actual ozone disinfection volume V=V1+V2+V3=11200m3

Ozone dosage

W=C*V/D=5*2.14*11200/0.4208=284.79g/h， The recommended output of the ozone generator is 300g/h.

(1) The sterilization effect K of ozone is the product of the actual concentration C of ozone and the action time T, that is, K=C × T. Ozone disinfection requires at least a threshold concentration to be reached. If the concentration is lower than the threshold concentration, the sterilization effect cannot be achieved, and if the concentration is too high, it will increase operating costs. Therefore, it should be calculated to select an ozone generating device with an appropriate range of concentration.

(2) The sterilization effect of ozone is most ideal under humidity conditions of 70-80%, and the effect is poor when the humidity is below 45%. Therefore, in general use, attention should be paid to increasing the humidity appropriately in the environment.

(3) Microbial species, temperature, organic matter pH、 The turbidity and color of water, as well as reducing substances in the disinfection space, may all affect the bactericidal effect of ozone, and should be controlled during use.

(4) Ozone is toxic to humans. When using ozone for sterilization, personnel are strictly prohibited from entering.

(5) Ozone is a strong oxidant that can damage various items. The higher the concentration, the more severe the damage. It can cause green rust spots on copper sheets, rubber aging, discoloration, reduced elasticity, brittleness, breakage, and bleaching and fading of fabrics. Attention should be paid when using it.

(6) Due to the fact that ozone can only be produced on-site, the most economical and technologically mature way to generate ozone is through corona discharge. Tubular ozone has the advantages of simple structure, reliable performance, low operating costs, and flexible regulation.

Ozone, as a new disinfection and sterilization method that started relatively late and has not been used for a long time in China, has the advantages of no dead corners, no residues, strong sterilization power, using air as raw material, simple operation, and low cost. Therefore, it is necessary and timely to explore its application in the space disinfection industry. However, due to certain issues in the design and application process of this system, further exploration and research by relevant technical personnel are needed.