Ultraviolet light provides a non chemical, environmentally friendly treatment option for swimming pools.  Most microorganisms, even cryptosporidium, are inactivated in less than a second by high doses of UV light, leaving no undesireable chemical residues.  The photochemical benefits of UV treatment have proven to significantly increase pool water quality, with very low combined chlorine levels and excellent clarity.  Due to their compact size, low ownership costs and simple maintenance requirements, UV disinfection units have been installed worldwide in many swimming pools.