[Inactivation of viruses and bacteria in sewage sludge by gamma radiation (author's transl)].

The kinetics of inactivation and the resistance to gamma radiation of microorganisms usually to be found in raw sludge were examined with five viruses, three bacteria and a fungus serving as prototypes in comparative studies. All these infectious agents could reliably be inactivated by gamma rays in raw sewage sludge but they were clearly more resistant to gamma rays compared to irradiation in a liquid suspension. The reduction of the virus content required a much higher radiation dose compared to bacteria and the fungus used, excluding Streptococcus faecalis which was exceptionally resistant. Considering the content of pathogenic viruses and other agents in raw sewage sludge, the required radiation dose necessary to comply with average to strict demands for the hygienisation of sewage sludge is discussed. The radiation dose of 500 to 1,000 krad seems therefore to be sufficient.