Total Internal Reflection of Deep-Ultraviolet Light in a Water Waveguide and Its Application to Water Disinfection Technologies

We propose a new disinfection technology based on a novel concept involving the use of a small, deep-ultraviolet light-emitting diode (DUV-LED); the 265-nm DUV light is coupled to a running-water stream and is guided to a distant position without diffusion due to the total internal reflection of the DUV light inside the water stream. We demonstrate here the effect of the water waveguide disinfection technique by showing significant inactivation of a contaminated surface with indicator bacteria; this was verified by comparing the results of three disinfection methods: (i) disinfection with DUV light, (ii) disinfection with running water, and (iii) disinfection with the water-waveguide method. We believe that the marriage of the point-source nature of DUV-LED emission and the water-waveguide effect paves the way towards new applications such as water washing technologies that can reduce water consumption more than one order of magnitude without using additional chemicals in a simple manner.