Ultraviolet (UV) technology has been marketed as a purifier to disinfect contaminated drinking water for many years. Low pressure mercury lamps have a very strong UV emission at 254 nanometers.

Bacteria, viruses and cysts represent the three types of microbiological contaminants that may be found in water. Following this occurrence pattern, the NSF task group on microbiological standards has proposed a requirement that bacteria reduction claims are accompanied by tested claims of virus reduction and cyst reduction.