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What is UV (Ultraviolet)?

With the pandemic we are experiencing, UV Light, especially Germicidal UV Light, has become a very curious topic. 

UV (ultraviolet) is called radiation with a Wavelength of UV Light ranging from 10 nm to 400 nm. Since the human eye can perceive rays above 400 nm wavelength, we cannot see UV rays. UV rays are divided into four according to their wavelengths. In the HVAC sector, UVC type short wave rays are used for disinfection.

Although UV light tubes seem like very new technology, their history is more than 100 years. Germicidal UV Light has been successfully applied for decades for disinfection in water treatment systems and food safety applications. 

UV rays, on the other hand, are much older. UV rays, which have existed since the creation of the universe, awaited to be discovered for a very long time. German scientist Johann Wilhelm Ritter was the first to discover the existence of ultraviolet rays.

The wavelength of UV Light

 

 

Definition

Wavelength

Area Of Use

UV-A

Long Wave UV

315-400 nm

Solarium

UV-B

Middle Wave UV

280-315 nm

Treatment

UV-C

Short Wave UV

200-280 nm

Disinfection

UV-V

Vacuum UV

100-200 nm

Ozone production, Odour Removal, Grease Filtration

Table 1. UV Types

UV Spectrum

Figure 1. Electromagnetic Spectrum

As can be seen from the graphic in Figure 2, the germicidal effect of UV light is in the wavelength range of 220-300 nm. The wavelength at which this effect is highest is 265 nm. Many UV-C lamps on the market are low-pressure mercury type lamps and mostly produce beams of 253.7 nm wavelength. Although the 253.7 nm value is close to the peak, it should be known that microbes are not killed with 100% efficiency. In addition, considering the losses caused by the ballasts of the lamps, it can be said that the efficiency of UV lamps is quite low. It is accepted that an average low-pressure mercury UV lamp produces UV light at a rate of approximately 25-35% of the declared electrical power.

Figure 2. Wavelength germicidal graphic [1]

WHAT is a UV Lamp?

Ultraviolet sterilization and disinfection lamp is a device with a low-pressure mercury lamp that can emit ultraviolet rays. Low-pressure mercury lamps are excited with low mercury vapour pressure (<10-2Pa) to emit ultraviolet radiation. The wavelength is between 10 ~ 400nm. The wave crest of the lamp is 253.7nm and the power is between 4W-100W. In addition, LEDs for UV lamps can be produced with today’s LED technology. It is mainly used for disinfection, sterilization and air purification. It is also used for post-dyeing drying of UV-based ink in the printing and dyeing industry.

How Does Germicidal UV Light Work?

UV rays cause photolysis and denaturing of bacterial proteins, disrupting and inactivating their cellular activities.

At the same time, when ultraviolet rays (a certain wavelength) pass through the air, the oxygen in the air is ionized to produce ozone, which increases the sterilization effect.

Can ozone be produced with UV?

There are two main spectral lines: one is 253.7nm (254nm) wavelength; the other is 185nm wavelength, both are invisible to the naked eye. Among them, 253.7nm ozone-free ultraviolet rays, 254nm ultraviolet rays kill bacteria by disrupting the DNA of microorganisms; 185nm ozone band is ultraviolet rays, 185nm wavelength can ionize the air to produce ozone (185nm ultraviolet can convert O2 to O3 in the air).

Ozone + 185nm short wave ultraviolet rays destroy DNA by irradiating bacteria and ionize oxygen in the air to produce ozone and kill bacteria. So it has a double sterilization effect.

12 Benefits of UV Light

  1. UV radiation has been proven to be effective against waterborne pathogenic microorganisms. UV Light is very effective to kill bacteria including those responsible for cholera, hepatitis, polio, typhoid, giardia, cryptosporidium and many other bacterial, viral and parasitic diseases
  2. Sterilizing with UV Light can be used to destroy chemical contaminants such as pesticides, hormones and other pharmaceuticals in drinking water or wastewater
  3. UV installations have low capital and operation cost
  4. UV technology is environmentally friendly
  5. UV installations are easy to operate and maintain
  6. UV radiation has no harmful effect when overdosed
  7. UV radiation works instantly and the effect does not depend on the water temperature
  8. UV disinfection is a physical process: no substances are added to the water
  9. UV disinfection is complementary to Chlorine disinfection: it deactivates organisms that are resistant to Chlorine such as giardia and cryptosporidium
  10. UV lamps can be easily regulated to optimise treatment for variations of water quality and for changing water flows
  11. UV radiation will keep the surface of reservoirs clean from biofilm
  12. The UV Light to Sterilize effectively is directly related to the UV dose (which is the product of intensity and exposure time of the micro-organisms) so its effectiveness can be simply measured once the system design is validated

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