Uses of UV disinfection UV radiation has disinfection properties that inactivate bacteria, viruses, and some other microorganisms. It effectively treats Giardia lamblia and Cryptosporidium cysts, which may also be removed from water by filtration. UV is not recommended if the untreated water contains very high levels of coliform, the indicator organism that is the basis for bacteriological water tests, or if there is substantial color or slide_3turbidity (cloudiness) in the water. UV is effective only if the light intensity reaches the organism in question; therefore, nothing should be present in the water that shields the organism from the radiation. Household UV treatment could conceivably be used for chlorinated water from a public supply if the home has a treatment device, such as an activated carbon filter, that removes chlorine (and thus allows bacterial growth). In this case, UV provides a final disinfection of the water supply.

Principles of UV disinfection UV radiation has three wavelength zones: UV-A, UV-B, and UV-C, and it is this last region, the shortwave UV-C, that has germicidal properties for disinfection. A low-pressure mercury lamp resembling a fluorescent lamp produces the UV light in the range of 254 nanometers (nm). A nm is one billionth of a meter (10-9 meter). Since most microorganisms are affected by radiation around 260 nm, UV radiation is in the appropriate range for germicidal activity. There are UV lamps that produce radiation in the range of 185 nm that are effective on microorganisms and will also reduce the total organic carbon (TOC) content of the water.