Abstract: The process for the disinfection of sewage sludge prior to introducing same into an anaerobic sewage sludge processing step involving the recovery of methane gas by heating the sewage sludge in a preceding disinfection step at from 50.degree. C. to 70.degree. C., and preferably at from 55.degree. C. to 65.degree. C., for a period of from 1 to 72 hours, and preferably of from 12 to 36 hours, while throughly mixing the sewage sludge with an oxygen-containing gas is carried out by using, as the oxygen-containing gas, a mixture comprising from 10 to 70% by volume of fresh air and 30 to 90% by volume of vent gas from the disinfection step, the oxygen contents of the gas mixture being maintained within the range of from 5 to 15% by volume, and preferably of from 7 to 12% by volume.

Abstract: A spiral tube aerator for waste aeration which includes a shaft rotatably driven by a motor, the shaft carrying a mixing chamber, an air channel extending along the shaft and opening through at least one outlet of the mixing member, a blower for delivering air through the air channel, the mixing chamber being submerged in waste water at least to a depth of 50 cm below the waste water upper surface, and the blower providing a pressure in the range 0-35 mbar lower than the pressure exerted by the waste water at the outlet.