Ultraviolet installations


   Ultraviolet radiation (ultraviolet, UV, UV) - is electromagnetic radiation, which occupies the range between the visible and X-ray emission (380-10 nm, 7.9-CH1014 3CH1016 Hz). The range is conventionally divided into short (380-200 nm) and far, or vacuum (200-10 nm) ultraviolet light. The latter is named so because it is intensively absorbed by the atmosphere and studied only by vacuum devices.

History of discovery

   The concept of ultraviolet light was first seen in the Indian philosopher of the XIII century Sri Mathavachariya. The atmosphere of described by him location Bhutakasha contains violet rays that can not be seen by the normal eye.

   Soon after infrared radiation was discovered, the German physicist Johann Wilhelm Ritter began searching for emission and at the opposite end of the spectrum with shorter length of wave than violet. In 1801, he discovered that silver chloride, that decomposes under the action of light, rapidly decomposes under the action of invisible radiation beyond the violet region of the spectrum. Then, many scientists, including Ritter, agreed that light is composed of three separate components: oxidative or thermal (infrared) components, lighting components (visible light) and recovery (UV) component. The ideas of the unity of the three different parts of the spectrum were first made public only in 1842 in the work of Becquerel, Mellon, etc.

Types of UV radiation

   Biological effects of ultraviolet radiation in three spectral regions differ significantly, so biologists sometimes singled out the following ranges as most important in their work:

  • Near ultraviolet light, UV-A rays (UVA, 315-400 nm). UV-B rays (UVB, 280-315 nm).
  • Far UV, UV-C rays (UVC, 100-280 nm).

   Virtually all UVC and approximately 90% UVB are absorbed by ozone and water vapor, oxygen and carbon dioxide during the passage of sunlight through the Earth's atmosphere. The radiation from the UVA range is rather poorly absorbed by the atmosphere. Therefore, radiation reaching the Earth's surface, largely contains near ultraviolet UVA, and, in a small percentage - UVB.

Natural sources

   The main source of UV – radiation on Earth is the Sun. The ratio of the intensity of UV- A and UV-B, the total amount of ultraviolet rays reaching the Earth's surface depends on the following factors:

  • the concentration of atmospheric ozone above the earth's surface,
  • the elevation of the sun,
  • the height above sea level,
  • from the atmospheric dispersion,
  • the state of the cloud cover,
  • the degree of reflection of UV rays from the surface (water, soil).

Artificial sources

   Through the creation and improvement of artificial sources of UV – radiation that ran parallel with the development of electric sources of visible light, today, professionals working with UV – radiation in medicine, prevention, sanitation and hygiene facilities are provided with significantly greater opportunities than using natural UV – radiation.

   Philips, Osram, Radium, Sylvania, companies etc. are currently involved in development and production of UV – lamps for plant photobiological action (UFBD). The range of UV – lamps for UFBD is very broad and diverse. So, for example, the world's leading manufacturer Philips has more than 80 types. In contrast to lighting sources, UV-radiation sources tend to have a selective range, designed to achieve maximum effect for a specific biological processes.

Disinfection of water

   Ultraviolet (s.c. quartz) lamps are used for disinfection of drinking water and recycled water in swimming pools. 86% of the radiation falls at the wavelength of 254 nm that agrees well with one of the two peaks in the curve of bactericidal effectiveness (i.e. efficiency of absorption of ultraviolet DNA molecules) in the most common low-pressure mercury lamps,. One of these peaks is near the wavelength equal to 265 nm, and the second – is 185 nm. Radiation with a wavelength of 185 nm has a greater effect on the DNA, but the quartz glass used for the manufacture of the bulb, as well as other natural substances (eg water) is less transparent to the waves of this range and more transparent to 265 nm wave.

   UV – disinfection is carried out under irradiation of microorganisms in the water by UV – radiation intensity in a certain period of time. As a result of irradiation, microorganisms die "microbiologically", because losing the ability to reproduce. UV – radiation, having a bactericidal wavelength of 260 nm or near wavelength, penetrates the cell wall of waterborne microorganism and is absorbed by DNA, called the genetic chain of microorganism, resulting in the reproduction of the organism ceases. Germicidal UV – radiation at these wavelengths causes dimerization of thymine in DNA molecules. The accumulation of such changes in the DNA of microorganisms leads to a slowdown in their reproduction and extinction. The method of disinfection using UV – radiation has proven its effectiveness in the decontamination of water-borne pathogens and viruses without compromising taste and smell of the water and without making any unwanted side products into the water.

   This method of disinfection is gaining popularity as an alternative or supplement to traditional disinfectants such as chlorine, because of its safety, efficiency and effectiveness. Due to the fact that these lamps affect only those microorganisms which are directly exposed to radiation, there is a problem of insufficient sterilization effect directly into the pool. It is for this reason, the quartz lamps are used only in combination with other methods of disinfection.

Why UV is needed

   Chlorination of water, held in the large scale, caused widespread resistance to chlorine of microorganisms, including many pathogens.

   The combination of UV – rays and chlorine in water treatment basin provides a high bactericidal effect against spore and chloride – stable forms of bacteria and viruses. In a joint water treatment with chlorine and bactericidal irradiation, chlorine consumption reduces in 2-3 drops, maintenance of equipment simplifies.

   A large number of organochlorine compounds, the toxicity of which exceeds the toxicity of the starting materials, appeares in the water treatment process. This can pose a real threat both to bathing people and support staff. UV – radiation causes photo-oxidation reaction, by which these compounds are decomposed into simple components - up to such as carbon dioxide and water. Together with chloramines and trigalogenmetanami unpleasant "chlorine" odor, allergic reactions and other unpleasant sensations associated with the use of chlorine disappear.

   Installation of UV – disinfection, manufactured by Philips company, have a body made of stainless steel. The inner surface is subjected to electrochemical polishing, that has very positive effect on the corrosion resistance and reflectivity of the device (lamp efficiency increases by about 30% at the same power).

   These settings can easily be built into the system of an existing water treatment equipment, they have small dimensions, they are easy to install and use, and compatible with all methods of water treatment and disinfection.

   After irradiation with UV – rays at a frequency of 253.7 nm metabolism of cells of microorganisms is disturbed, they lost the ability to reproduce (for 4-5 hours), which contributes to the destruction of them even with small concentrations of disinfectants. Dependence of the rate of growth of algae on the pH and the presence of phosphates is reduced. Water is saturated with oxygen additionaly, stand out as a result of photochemical reactions, resulting in better purity and freshness of the water. Ozone is formed (in trace), providing additional oxidative effects, including the dirt. UV – radiation increases the oxidizing capacity of chlorine or oxygen. The use of ultraviolet light in the treatment of water – is one of the most promising directions in search of alternative, environmentally friendly, reliable and inexpensive way to disinfect.