The human eye can detect wavelengths from 380nm to 700nm.  Ultraviolet light falls below the 380nm wavelength and is divided into four segments. 

100nm ~ 200nm is vacuum UV or ozone.   

200nm ~ 280nm is UV-C or Far-UV.
280nm ~ 315nm is UV-B and 315~ 400nm is UV-A. 

UV-C radiation is scientifically proven to break the DNA of bacteria, viruses and spores.  More recently it has been proven effective at eliminating coronavirus from surfaces and potentially air & water.  It is a proven technology that can be used for multiple purposes including in water & air treatment but is primarily employed as a disinfection process that inactivates micro-organisms without the need for harmful chemicals.