Ultraviolet irradiation water disinfection

The single most important use of chlorine-containing compounds is water disinfection. About 98% of the drinking water in the US and 96% of the waste water is treated with chlorine. There are four technologies that could replace chlorination membrane filtration, ultraviolet irradiation, filtration on activated carbon bed and treatment with ozone (ozonolysis). All of them are more expensive than chlorination, and none of them were studied in as much detail as chlorination was. If ozone is used, the by-products formed in the reactions of ozone with organic compounds have to be removed in a separate step using activated carbon. Overall, there is no viable alternative to chlorination today. 

Over the years, public water systems have used various alternatives to chlorine disinfection. The more common alternatives include (1) chloramines, (2) Ozone, (3) Chlorine Dioxide, and (4) Ultraviolet irradiation. 

Physical disinfection of drinking water is mainly carried out through photodegradation by ultraviolet radiation (UV). Because many pharmaceuticals have chromophores that absorb UV wavelength, UV irradiation can lead to some transformation. Comparing to chemical oxidation, such as chlorination, UV disinfection has an advantage of minimizing the formation of DBPs [73]. However, at a... 

The physical agents of disinfection that have been used include ultraviolet light (UV), electron beam, gamma-ray irradiation, soniflcation, and heat (Bryan, 1990 Kawakami et al., 1978 Hashimoto et al., 1980). Gamma rays are emitted from radioisotopes, such as cobalt-60, which, because of their penetrating power, have been used to disinfect water and wastewater. The electron beam uses an electron generator. A beam of these electrons is then directed into a flowing water or wastewater to be disinfected. For the method to be effective, the liquid must flow in thin layers. 

Chlorine is the most commonly used disinfecting agent in the Asian cities. Other disinfectants are ozone, chlorine dioxide, and ultraviolet radiation. Some new disinfecting agents are now in advanced water treatment systems, like bactericides, surfactants, antibiotics, irradiation, sonification, and electric shock. 

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