Ultraviolet reactors are used for a disinfection of water without chemicals.
In preparing drinking water a bacterially blameless drinking water must be permanently guaranteed (see regulations on drinking water), an emergence of pathogenic agents must be prevented. Disinfection is here one of the most important treatment processes. There is only a limited choice of methods.
In the field of industrial water the water bearing systems offer ideal living conditions for microorganisms. An unimpeded growth often results in disturbances of the operation and damages. Many organic biocide agents can be applied only to a limited extend due to their aquatic toxicity - especially with regard to the sensitive luminous bacteria test which is compulsory for direct discharging according to the water balance law. For air moistening by air cleaners, too, the application of bactericide chemical agents is very much limited by their toxical effects (see VDI 6022).

An alternative to the usual methods of disinfection is the ultraviolet disinfection, which has got a cytotoxic effect on the bacteria in the UV-irradiated water. That is why the populations of microorganisms die off within a short period of time without chemically changing the other contents of water, without producing by-products, without influencing smell and taste.

But the disadvantage is that the bacterial cultures can continue growing outside of the reactor, therefore, the circulating water must always be kept in a condition with very few germs in order to avoid sediments of settled bacteria.
Due to its compact design the ultraviolet disinfection can be easily fitted into existing plants.
Moreover, the process is very cost-efficient because of the low operation costs.