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Physical Disinfection by UV Radiation

	Physical Disinfection by UV Radiation Two important physical disinfection methods are ultraviolet (UV) radiation and boiling of water. UV radiation Electromagnetic radiation of ultraviolet range can be used to destroy microorganisms. This process is effective in certain small water supplies where the water is highly polished i.e., filtered and demineralised. The process is also used in industries. For example in breweries, pharmaceutical manufactures, fish hatcheries and aquariums
Actually irradiation must strike the organism to kill it. In this process some of the radiation energy is absorbed by the organism and other' constituents in the medium surrounding the organisms. So if sufficient dosage of UV reach the organisms water can be disinfected. The germicidal effect of ultraviolet energy is thought to be associated with its absorption by certain organic components essential for the functioning of cells. Dissipation of energy by excitation causes disruption of unsaturated, bonds, particularly of the purines and pyrimidines. And this leads to lethal biochemical changes.
UV treatment does not alter the water chemically. Only energy is added, which produces heat, resulting in a temperature rise in the treated water. UV rays can penetrate the cell walls of microorganisms. So the only requirement in disinfection by UV radiation is it must reach the organisms since the UV radiation absorbed by the organisms alone can kill them. This is, one of the main disadvantage of the UV process. Other disadvantages are lack of a field test to readily establish the efficiency of the process inability of UV irradiation to provide a residual disinfecting power high cost of the system.

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Disinfecion Drinking Water Chemical Disinfection Chemical Disinfection by Chlorine Chemical Disinfection by Ozone Chemical Disinfecion by Pottassium Permanganate Chemical Disinfection by Halogens Physical Disinfection by UV Radiation Germicidal Efficiency

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