Bacteriological control of various methods of sewage sludge hygienization

: As a result of extensive parallel investigations in a water treatment plant it was found that the fresh sludge pasteurization or prepasteurization with ensuing sludge digestion gives a product which is unobjectionable from an epidemiological hygienic point of view. The result were confirmed by investigations in a second plant. Similarly satisfactory results were obtained with the composting of previously desiccated sludge, with the aerobic-thermophilic fermentation of liquid sludge or with the drying of sewage sludge. An alternative to these thermal processes is the application of gamma rays or accelerated electrons.