What is Ultraviolet Water Disinfection? Ultraviolet Water Disinfection disables harmful germs in water. UV light inactivates microorganisms by damaging their nucleic acid. Reproduction is voided. If not disabled, bacteria will form colonies, viruses form plaques, and protozoan cysts attack a host or tissue culture. Among the results of unaffected germs that travel in water include Gastroenteritis, bacillary dysentery, amoebic dysentery, Hepatitis, and much more.