EVALUATION OF THE EFFICIENCY OF PLANTS FOR UV-DISINFECTION OF DRINKING-WATER

The increasing application of UV-radiation for disinfection of drinking water in Austria makes it necessary to prove the effectiveness of UV-disinfection plants. For this purpose the dose applied to the water must be measured, a form of a UV-dosimeter has to be used. Until some years ago various strains of microorganisms were added to the water and the inactivation caused by the disinfection plant was measured. This method, however, gives no reliable information about the UV-dose attained, as the applied uncalibrated microorganisms may have varying UV-susceptibility. Therefore the results were not comparable. The application of biodosimeters, for instance spores of Bacillus subtilis, the UV-susceptibility of which has been measured exactly in a laboratory irradiation device, gives the possibility to obtain quantitative information about the UV-dose produced by disinfection plants for drinking water. Commercially available UV-disinfection units were tested using a biodosimeter, their disinfection capability and permissible working parameters were determined. The influence of a serial arrangement of two irradiation chambers upon the overall dose was measured.