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.
Sterilization method
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.
Advantages: fast
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.
