Ultraviolet Disinfection

Ultraviolet Disinfection

Over 100 years ago, German scientists discovered that the top surface of lake-water was sterile when exposed to sunlight. Investigation led to the discovery of Ultraviolet light. Situated in the electro- magnetic spectrum between X-rays and visible light, Ultraviolet (UV) light has many beneficial properties. UV light is split into four main categories, UV-A, UV-B, UV-C and Vacuum UV. The area between 240 and 280 nanometres (nm) is UV-C, commonly known as the germicidal region.

UVC light has the ability to cause permanent damage to a wide variety of nuisance organisms in water, air and other fluids. For industrial product and process fluids, these organisms can cause spoilage and reduced shelf life. For municipal drinking water, these organisms cause nuisance and in a number of instances can actually be pathogenic to humans. The 2000 outbreak of E coli 0157:H7 in Walkerton, Ontario killed 7 people and made 2500 ill.

Some organisms, such as Actinomycetes, can produce geosmin and 2-methylisoborneol (MIB), which are often described as producing an earthy-musty, camphor-like taste and odor in drinking water. Other species have now developed or adapted immunity to conventional disinfection techniques; Cryptosporidium Parvuum is one such "emerging" pathogen that chlorine cannot kill. An outbreak of Cryptosporidium in Milwaukee in 1993 made 400,000 people ill and hospitalized 4400 people. Another outbreak in Pitsford, UK left 300,000 homes without safe drinking water for two weeks.

UV light is a physical, non-intrusive method of ensuring that organisms, which are airborne or present in most fluids, are unable to replicate and thus remain inert. Correctly sized UV systems can also be used to de-chlorinate or de-ozonate process water and to assist in the removal of TOC and urea from ultra pure water.

UV does not affect the taste, colour, or pH of the fluid being disinfected and, as such, the technique is often used where conventional chlorine disinfection cannot be applied, such as within a brewery, soft drinks plant, pharmaceutical facility or fish farm. 

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