It has been known, for well over a century, that sunlight can disinfect drinking water by permanently killing or inactivating bacteria, spores and viruses. Scientists have found that the most effective disinfection wavelength of the UV spectrum is 260nm.

Although similar to fluorescent lamps, UV lamps are actually made with a quartz tube, rather than a glass tube, to hold the mercury gas inside. The quartz tube lets the UV light transfer through the tube to disinfect the water.

UV light is generated when an electrical current is applied to the cathode and anode of the UV lamp. The mercury inside the lamp turns from liquid to gas and the mercury atoms produce UV light. The wavelength of the UV light produced by low pressure UV lamps is 254 nanometers (nm). The quartz tube used for water purification applications allows 93% of the UV light produced to pass to the outside.