Disinfection of sewage sludges by gamma irradiation and alternative methods

Sewage sludges generally maintain high concentrations of pathogens. For their safe reutilization on agriculturally used areas a disinfection treatment is necessary. Conventional methods for this purpose are e.g. heat-treatment (pasteurization), composting and lime-treatment. A new technique for sludge disinfection is the irradiation treatment by gamma-rays or by accelerated electrons. The first practical plant for gamma-irradiation of sewage sludges has been in operation since 1973 in Geiselbullach, near Munich, Federal Republic of Germany. This paper summarizes the existing and projected plants for the sewage sludge disinfection by irradiation and names the conventional alternative methods with their main advantages and disadvantages. The techniques for irradiation and sludge handling in irradiation plants are described. Broad research work in Geiselbullach with the aim of operational and economic optimization led to a combined treatment of irradiation and oxygenation: the oxiradiation-treatment. The costs for gamma-irradiation and alternative treatments for sewage sludge disinfection are given. Finally the problems with gamma irradiation plants are discussed. (author). 1 ref., 2 figs, 1 tab