Working principle of ultraviolet sterilization lamp

The ultraviolet sterilization lamp actually belongs to a low-pressure mercury lamp. The low-pressure mercury lamp emits ultraviolet light by using the low-pressure mercury vapor (< 10-2Pa), and its luminous spectrum has two main lines: one is 253.7nm wavelength; The other is 185nm wavelength, both of which are ultraviolet rays invisible to the naked eye.

The sterilization lamp does not need to be converted into visible light. The wavelength of 250nm-260nm can play a good sterilization role. This wavelength range can destroy its chromosome and play a photochemical role.

The strongest ultraviolet absorption peak of deoxyribonucleic acid (DNA), ribonucleic acid (RNA) and nuclear protein in bacteria is 254 ~ 257nm.

After bacteria absorb ultraviolet light, it causes DNA strand breakage, resulting in cross-linking rupture of nucleic acid and protein, killing the biological activity of nucleic acid and causing bacterial death.

Only artificial mercury (alloy) light source can output sufficient UVC intensity for engineering disinfection. The ultraviolet sterilization lamp tube is made of quartz glass. According to the different mercury vapor pressure in the lamp tube and the different ultraviolet output intensity, the mercury lamp is divided into three types: low-pressure low-intensity mercury lamp, medium pressure high-intensity mercury lamp and low-pressure high-intensity mercury lamp. The sterilization effect is determined by the irradiation dose received by microorganisms. At the same time, it is also affected by the output energy of ultraviolet rays, which is related to the type, light intensity and service time of the lamp. With the aging of the lamp, it will lose 30% - 50% of its intensity. Ultraviolet radiation dose refers to the amount of ultraviolet light at a specific wavelength when a certain bacterial inactivation rate is reached: irradiation dose (J / m2) = irradiation time (s) × The greater the irradiation dose of UVC intensity (w / m2), the higher the disinfection efficiency. Due to the size requirements of the equipment, the general irradiation time is only a few seconds. Therefore, the UVC output intensity of the lamp has become the most important parameter to measure the performance of UV disinfection equipment. In urban sewage disinfection, the average irradiation dose is generally more than 300 J / m2. Below this value, light resurrection may occur, that is, the bacteria cannot be completely killed. When they flow out of the channel and receive visible light irradiation, they will resurrect, reducing the sterilization effect. The higher the requirement of sterilization efficiency, the greater the irradiation dose required. The main factor affecting the microorganism to receive sufficient ultraviolet radiation dose is the light transmittance (at 254 nm). When the UVC output intensity and irradiation time are fixed, the change of light transmittance will cause the change of the actual received dose of microorganism.

Ultraviolet sterilization lamp can destroy the molecular structure of DNA (deoxyribonucleic acid) or RNA (ribonucleic acid) in microbial body cells by using ultraviolet light of appropriate wavelength, resulting in growth cell death and / or regenerative cell death, so as to achieve the effect of sterilization and disinfection. 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 UVA and UVB can reach the earth's surface through the ozone protective layer and clouds. In terms of sterilization speed, UVC is within the range of microbial absorption peak and can kill viruses and bacteria by destroying the DNA structure of microorganisms within 1s. However, 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 the role of sterilization. Within the hydraulic retention (irradiation) time of several seconds in the actual project, This part is actually an invalid UV part. The penetration ability of vacuum ultraviolet light is very weak. The lamp tube and sleeve need to use quartz with extremely high light transmittance. Generally, the semiconductor industry is used to degrade TOC in water, which is not used for sterilization and disinfection. Therefore, the ultraviolet 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 UVC band ultraviolet light with high efficiency, high intensity and long life to irradiate the running water to directly kill various bacteria, viruses, parasites, algae and other pathogens in the water, so as to achieve the purpose of disinfection.

Research shows that ultraviolet radiation can kill microorganisms by damaging the function of nucleic acid and damaging microorganisms (bacteria, viruses, spores and other pathogens), so as to achieve the purpose of disinfection. The effect of ultraviolet on nucleic acid can lead to bond and chain breaking, inter strand crosslinking and the formation of photochemical products, which can change the biological activity of DNA and make microorganisms unable to replicate themselves. This ultraviolet damage is also fatal.

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 joint processes include UV + H2O2, UV + H2O2 + O3 and UV + TiO2. In this way, the disinfection effect will be better.

Most ultraviolet devices use traditional low-voltage ultraviolet lamp technology, and some large water plants use low-voltage high-intensity ultraviolet lamp system and medium voltage high-intensity ultraviolet lamp system. Due to the generation of high-intensity ultraviolet, the number of lamps may be reduced by more than 90%, thus reducing the floor area and saving installation and maintenance costs, The ultraviolet disinfection method is also applicable to the effluent with poor water quality.

Ultraviolet disinfection has a wide range of uses. Hospitals, schools, nurseries, cinemas, buses, offices, families, etc. it can purify the air and eliminate the musty smell. In addition, it can also produce a certain amount of negative oxygen ions. The air in rooms disinfected by ultraviolet is particularly fresh. In public places, ultraviolet disinfection can prevent some bacteria from spreading through the air or through the surface of objects.

However, because ultraviolet rays can penetrate cells and kill them, when disinfecting with ultraviolet rays, pay attention not to directly irradiate human skin, especially human eyes. When the ultraviolet sterilization lamp is lit, do not look directly at the lamp tube. Because short wave ultraviolet rays do not pass through ordinary glass, wearing glasses can avoid eye injury. If you accidentally hurt your eyes, it's not a big problem in general. Just like being burned by sunlight, you can drop eye drops or human milk to help you recover. Do not use ozone lamps when there are person in the house. People can be poisoned when the concentration of ozone is high.