The ultraviolet germicidal lamp is actually a low-pressure Hg lamp. The low-pressure Hg lamp emits ultraviolet light by being excited by lower pressure Hg vapor (<10-2 Pa). There are two main emission spectral lines: one is 253.7nm wavelength; the other is 185 n m wavelength, both of which are naked eyes Invisible ultraviolet rays.
Only artificial Hg (alloy) light source can output enough UV C intensity for engineering disinfection. The tube of the ultraviolet germicidal lamp is made of quartz glass. The Hg lamp is divided into three types according to the Hg vapor pressure in the lamp tube after lighting and the difference of the ultraviolet output intensity: low-pressure low-intensity Hg lamp, medium-pressure high-intensity Hg Lamps and low-pressure high-intensity Hg lamps. The sterilization effect is determined by the radiation dose received by the microorganisms. At the same time, it is also affected by the output energy of ultraviolet rays, which is related to the type of lamp, light intensity and use time. As the lamp ages, it will lose 30%-50% of its intensity . Ultraviolet radiation dose refers to the amount of ultraviolet radiation of a specific wavelength when reaching a certain bacterial inactivation rate:radiation dose (J/m 2) = radiation time (s) × UV C intensity (W/m 2) The larger the radiation dose, the more efficient the disinfection. Because of the equipment size requirements, the general irradiation time is only a few seconds. Therefore, the UV C output intensity of the lamp tube becomes the most important parameter to measure the performance of the ultraviolet disinfection equipment. In the disinfection of urban sewage, the average radiation dose is generally above 300 J/m 2. Below this value, the phenomenon of light resurrection may occur, that is, the germs cannot be completely killed. When they flow out of the channel and receive visible light, they will be revived, reducing the sterilization effect. The higher the requirement for sterilization efficiency, the greater the radiation dose required. The main factor that affects the microbes receiving sufficient UV radiation dose is the light transmittance (at 254 n m). When the UV C output intensity and irradiation time are constant, the change in light transmittance will cause the actual dose of the microorganisms to change. Most UV devices use traditional low-pressure UV lamp technology, and some large water plants use low-pressure high-intensity UV lamp systems and medium-pressure high-intensity UV lamp systems. Due to the generation of high-intensity ultraviolet rays, the number of tubes may be reduced by more than 90%. The footprint is reduced, the installation and maintenance costs are saved, and the ultraviolet disinfection method is also applicable to the effluent with poor water quality.
Because ultraviolet rays can penetrate cells to make them die, be careful not to directly irradiate human skin, especially human eyes, when using ultraviolet rays. Glass, wear glasses to avoid eye damage. If you accidentally hurt your eyes, it is not a major problem in general. It is just like being burned by the sun. Serious eye drops or human milk can be used to help recover. Don't use ozone lamps when there are people. High ozone concentration can poison people.
Scope of application editing Voice Ultraviolet disinfection has a wide range of uses, such as hospitals, schools, nurseries,
cinemas, buses, offices, homes, etc., it can purify the air, eliminate musty odors, and also produce a certain amount of negative oxygen ions. The room that has been sterilized by ultraviolet light can clean the air. Especially fresh. In public places, ultraviolet disinfection can prevent some germs from spreading through the air or through the surface of objects.
Deoxyribonucleic acid (DNA), ribonucleic acid (RNA) and nucleoprotein in bacteria have the strongest ultraviolet absorption peak at 254~257nm.
After the bacteria absorb ultraviolet rays, the DNA strands are broken, causing the cross-linking of nucleic acids and proteins to rupture, killing the biological activity of nucleic acids, and causing the death of bacteria.
The sterilization efficiency of ultraviolet rays on common bacteria and viruses (radiation intensity: 30000μW/cm2)
Principle of UV sterilization It is the use of the appropriate wavelength of ultraviolet light to destroy the molecular structure
of DNA (deoxyribonucleic acid) or RNA (ribonucleic acid) in the cells of microorganisms, causing growth cell death and (or) regenerative cell death, achieving the effect of sterilization and disinfection. 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 clouds. As far as the sterilization speed is concerned, UVC is within the absorption peak range of microorganisms, and can kill viruses and bacteria by destroying the DNA structure of microorganisms within 1s, while UVA and UVB are outside the absorption peak range of microorganisms, so the sterilization speed is very slow. It often takes several hours to achieve a sterilization effect. In the actual project's hydraulic retention (irradiation) time of a few seconds, this part is actually an invalid UV part. 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 in the semiconductor industry, and it is not used forsterilization. Therefore, the UV disinfection in water supply and drainage engineering actually refers to UVC disinfection. Ultraviolet disinfection technology is based on modern epidemic prevention, 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 killed directly to achieve the purpose of disinfection.
Studies have shown that ultraviolet rays mainly kill microorganisms through radiation damage to microorganisms (bacteria, viruses, spores and other pathogens) and the function of destroying nucleic acids, thereby achieving the purpose of disinfection. The effect of ultraviolet rays on nucleic acids can lead to breakage of bonds and strands, cross-linking between strands and formation of photochemical products, etc., thereby changing the biological activity of DNA and making microorganisms unable to replicate themselves. This ultraviolet damage is also fatal.
Ultraviolet disinfection is a physical method. It does not add any substance 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 are UV+H2O2, UV+H2O2 +O3, UV+TiO2, in this way, the disinfection effect will be better.