UV-DISINFECTION OF TREATED WASTE-WATER - POSSIBLE EFFECTS ON SURFACE WATERS

UV-irradiation as an effective method of diminishing germs in the outl et of wastewater treatment plants was studied in a half-scale pilot-pr oject sponsored by the State of Bavaria/BRD for a period of 3 years. T echnical, physical and biological parameters capable of influencing th is process were examined. The possibility to improve the hygienic and also the ecological structure of receiving waters was put to discussio n. Possible effects of formed by-products upon the water biocoenosis o f rivers were pointed out. The results demonstrated that W-irradiation can diminish the number of germs in the outlet of a treatment plant t o an extent which is sufficient to guarantee the maintenance of the ba cteriological and presumably also the virological values set by the EC Bathing Water Directive. Nevertheless the W-treatment process require s further technological development and research work concerning i.e. the improvement of hydraulic conditions, coat-forming on the quartz sl eeves of the lamps, photochemical forming of by-products, after-growth and effects upon the localised benthic flora and fauna of the receivi ng water. It has to be stressed that a significant improvement of the bacteriological structure of flowing waters is only attainable, if the influx from non-point sources can be reduced simultaneously.