The strongest ultraviolet absorption peaks of deoxyribonucleic acid (DNA), ribonucleic acid (RNA) and nucleoprotein in bacteria are in the range of 254-257nm.
After the bacteria absorb ultraviolet rays, it causes DNA strand breaks, causing the cross-linking of nucleic acids and proteins to rupture, killing the biological activity of nucleic acids and causing the death of bacteria.
Sterilization efficiency of ultraviolet rays on common bacteria and viruses (radiation intensity: 30000 μW/cm2)
The principle of ultraviolet sterilization:
It is the use of ultraviolet light of appropriate wavelength to destroy the molecular structure of DNA (deoxyribonucleic acid) or RNA (ribonucleic acid) in the cells of microorganisms, resulting in growth cell death and / or regenerative cell death, to achieve the effect of sterilization. After testing, the effective wavelength range of ultraviolet sterilization can be divided into four different bands: UVA (400 ~ 315nm), UVB (315 ~ 280nm), UVC (280 ~ 200nm) and vacuum ultraviolet (200 ~ 100nm). Among them, only the UVA and UVB parts can reach the earth's surface through the ozone protective layer and the cloud layer. In terms of sterilization speed, UVC is within the range of microbial absorption peaks, which can kill viruses and bacteria within 1 s by destroying the DNA structure of microbes, while UVA and UVB are outside the range of microbial absorption peaks, the sterilization rate is very slow. It often takes several hours to play a sterilizing role. During the hydraulic retention (irradiation) time of a few seconds in the actual project, this part is actually an invalid UV part. Vacuum ultraviolet light penetration is extremely weak, and lamps and sleeves need to use extremely high transmittance quartz. Generally, the semiconductor industry is used to degrade TOC in water, and it is not used for sterilization. Therefore, the ultraviolet disinfection in water supply and drainage engineering actually refers to UVC disinfection. Ultraviolet disinfection technology is based on modern epidemiology, medicine and photodynamics, and uses specially designed high-efficiency, high-strength and long-life UVC band ultraviolet light to irradiate flowing water to expose various bacteria, viruses, parasites and algae in the water. And other pathogens are directly killed to achieve the purpose of disinfection.
Studies have shown that ultraviolet rays mainly kill microorganisms by radiating damage to microorganisms (bacteria, viruses, spores and other pathogens) and destroying the function of nucleic acids, thereby achieving the purpose of disinfection. The action of ultraviolet rays on nucleic acids can lead to the breaking of bonds and chains, cross-strand cross-linking and the formation of photochemical products, etc., thereby changing the biological activity of DNA and preventing the microorganisms from replicating themselves. This ultraviolet damage is also a lethal damage.
Ultraviolet disinfection is a physical method. It does not add any substances to the water and has no side effects. This is where it is superior to chlorinated disinfection. It is usually used in combination with other substances. Common joint processes are UV + H2O2, UV + H2O2 + O3, UV + TiO2, so the disinfection effect will be better.
Link to this article：Sterilization method of ultraviolet sterilization lamp
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