Radiation emitted from ultraviolet (UV) light sources has been used to a limited extent since the early 1900s for disinfection of water supplies.Primarily used on high -quality water supplies at first , new interest has recently focused on the use of ultraviolet light as a waste water disinfectant.A porper dosage of ultraviolet radiation has shown to be an effective bacteriocide and virucide while not contributing to the formation of toxic compounds.

Ultraviolet light is aphysical rather than a chemical disinfecting agent.Radiation with a wavelength of around 254 nm penetrates the cell wall of the microorganism and is absorbed by cellular materials including DNA and RNA, which either prevents replication or causes death of the cell to occur.Because the only ultravioletradiation effective in destroying bacteria is that which reaches the bacteria, the water must be relatively free from turbidity that would absorb the ultrviolet energy and shield the bacteria.It has also been reported that ultraviolet light is not an effective disinfectant on wastewaters that contain high solids concentrations.For practical purposes,the inactivation of bacteria by UV radiation can be described using first order kinetics.