Why does UV light sterilize?

Technical characteristics of UV disinfection

1. High-efficiency sterilization

2. Broad-spectrum sterilization

3. No secondary pollution

4. Simple operation and maintenance, low cost

5. Continuous large amount of water disinfection

6. Wide application fields

Ultraviolet rays refer to sunlight with wavelengths between 200nm and 380nm, including three categories: UV-A wavelengths of 315nm to 380nm, UV-B wavelengths of 280nm to 315nm, and UV-C wavelengths of 200nm to 280nm. The ultraviolet rays (290nm-2000nm) that reach the earth's surface account for about 13%, of which UV-A accounts for 97%, UV-B accounts for 3%, and UV-C is close to 0. Only UV-A and UV-B damage human skin. The UV-C ultraviolet lamp made by special process is used for disinfection and sterilization.

Among them, the real germicidal effect is uv-C wave ultraviolet rays, and the ultraviolet rays around 254nm are the best. Ultraviolet light can kill a variety of microorganisms, including bacterial propagules, spores, mycobacteria, viruses, fungi, rickettsia and mycoplasma, etc., with a broad spectrum.

The sterilization principle is to irradiate microorganisms such as bacteria and viruses with ultraviolet rays to destroy the structure of DNA (deoxyribonucleic acid) in the body, causing them to die immediately or lose their ability to reproduce. Quartz UV lamps have advantages, so, how to identify true and false. The sterilization ability of ultraviolet rays in different bands is different. Only short-wave ultraviolet rays (200-300nm) can kill bacteria. Among them, the sterilization power is the strongest in the range of 250-270nm. The cost and performance of ultraviolet lamps made of different materials are also different. A truly high-intensity, long-life UV lamp must be made of quartz glass. This lamp is also called a quartz germicidal lamp. It is divided into two types: high-ozone type and low-ozone type. High-ozone type is generally used in disinfection cabinets. A notable feature of quartz UV lamps compared to other UV lamps, in addition, it produces high UV intensity, which is more than 1.5 times that of high-boron lamps, and the UV radiation intensity has a long life. The most reliable way to distinguish is to use the 254 nm probe of the UV irradiance meter to measure. The same power, the highest UV intensity at 254 nm is the quartz UV lamp. The second is the high boron glass ultraviolet lamp. The ultraviolet light intensity of the high boron glass lamp is easily attenuated. After it is lit for hundreds of hours, its ultraviolet light intensity will drop sharply to 50%-70% of the initial value. In the user's hand, although the light tube is still lit, it may not be functional. The light attenuation of quartz glass is much smaller than that of high boron lamps. No matter what kind of glass is used for a lamp coated with phosphor powder, it is impossible to emit short-wave ultraviolet rays, and it is impossible to generate ozone, because the spectral line converted by the phosphor powder has the shortest wavelength around 300 nm, which is in the disinfection cabinet. What you can often see is the mosquito killer lamp, which can only produce the 365nm spectral line and part of the blue light. Its function has no disinfection effect at all except to attract mosquitoes. ----Comparing the appearance of high boron glass UV lamps and quartz UV lamps, quartz UV lamps generally cannot be equipped with aluminum caps. The production process of the round seal with a higher degree of automation can be used, and the process is the same as that of the fluorescent lamp production, and the aluminum lamp cap can be used.

Quartz glass has a high melting point and a low expansion coefficient. If it is heated in a fire at the same time, the melting point of high boron glass is low. After being heated, it is quenched in water at the same time, and it is quartz glass that will not break. For some so-called "ultraviolet lamps" made of ordinary glass tubes, which do not contain ultraviolet rays, a simple method is used to test: light this lamp next to a CFL or fluorescent lamp, it cannot excite the fluorescent powder inside the tube to emit light , it can be confirmed that it is a veritable fake and shoddy product.

The principle of ultraviolet sterilization and disinfection is to use ultraviolet rays of appropriate wavelengths to destroy the molecular structure of DNA (deoxyribonucleic acid) or RNA (ribonucleic acid) in microbial cells, causing growth cell death and/or regenerative cell death to achieve sterilization and disinfection. Effect. 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 protective layer of ozone and clouds. In terms of sterilization speed, UVC is within the range of microbial absorption peak, and can kill viruses and bacteria within 1s by destroying the DNA structure of microorganisms, while UVA and UVB are outside the range of microbial absorption peak, and the sterilization speed is very slow. It often takes several hours to play a sterilizing effect, and this part is actually an ineffective ultraviolet part during the hydraulic retention (irradiation) time of several seconds in the actual project. The penetration ability of vacuum ultraviolet light is very weak, and the lamp tube and sleeve need to use quartz with extremely high light transmittance. Generally, the TOC in the water is degraded by the semiconductor industry, and it is not used for sterilization. Therefore, the ultraviolet light disinfection mentioned in the water supply and drainage project actually refers to UVC disinfection. Ultraviolet light disinfection technology is based on modern epidemiology, medicine and photodynamics. It uses specially designed high-efficiency, high-intensity and long-life UVC band ultraviolet light to irradiate flowing water to remove 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 acid, so as to achieve the purpose of disinfection. The effect of ultraviolet rays on nucleic acids can lead to the breakage of bonds and chains, cross-linking between strands and the formation of photochemical products, etc., thereby changing the biological activity of DNA and making microorganisms unable to replicate themselves. This ultraviolet damage is also 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 chlorination disinfection. It is usually used in combination with other substances. Common combined processes include UV+H2O2, UV+H2O2 +O3, UV+TiO2, in this way, the disinfection effect will be better.

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