UVGI sterilization is an option to consider if you are filtering water that may be microbiologically unsafe to drink (i.e. lake water). UV-C sterilization consists of a UV-C lamp, housing and power supply. UV-C lamps should be replaced annually under normal use.
UV-A, UV-B, and UV-C are bands of ultraviolet radiation emitted by the sun. The atmospheric ozone layer absorbs almost all UV-B and UV-C, so 98.7% of the UV that reaches the Earth is UV-A. While the wavelengths of the visible spectrum of light are in range of 400-700nm (a nanometer is a billionth of a meter), UV-A represents the longest wavelengths, from 315-400nm, UV-B represents the medium wavelength of 280-315nm, and UV-C, or germicidal UV, represents the shortest wavelength, from 100-280nm, however the most effective wavelength is between 253 and 254nm, the wavelength used by manufacturers of UV-C lamps.
The most well known wavelengths of ultraviolet light are UV-A and UV-B, due to their effect on human skin, however all ultraviolet light can damage the eyes and skin and should never be viewed with the naked eye without protection. UV-B is also the wavelength of light that reacts with cholesterol in the skin to form Vitamin D.
UVGI, Ultraviolet Germicidal Irradiation utilizes the UV-C wavelength (known as germicidal UV) as a sterilizer as it kills viruses, bacteria and larger pathogens including Giardia and Cryptosporidium. UV-C/UVGI is an effective method of killing micro-organisms in water.
UV-C does not remove other contaminants, heavy metals, chlorine or fluoride, so it should be used in a water treatment systems that utilizes other filtration technologies, including sediment and activated carbon filtration. For UV-C to effectively kill microorganisms it is crucial that the water be clear, as cloudy or turbid water prevents it from being effective.
Commercial UV-C lamps that are incorporated into the design of water treatments systems use a low pressure mercury vapor discharge tube that resembles a quartz lamp to produce UV-C at 253-254nm, the most effective wavelengths for the destruction of micro-organisms. UV-C lamps require small amounts of electricity (4 – 40 watts) which has spawned the development of a growing number of portable battery powered UV-C sterilization products, including Steripen, an innovative portable water sterilization device not much larger than a ballpoint pen, the Zadro UV sterilizer, used to sterilize surfaces like food cutting boards, telephone handsets, and personal items like pillows, mattresses and footwear, and the Raycop Antibacterial Vacuum, an amazing new product that sterilizes bedding, pillows, and mattresses, while killing and removing dust mites and dust mite feces.