Process for sludge reduction in an aerobic sludge generating waste treatment system

Abstract

This invention relates to an improved process for the treatment of municipal waste and particularly to the reduction of organic sludges generated in the biological digestion of organic material. In the conventional processes the waste containing organic matter is contacted with an oxygen-containing gas in the presence of biologically active organisms under conditions to produce biomass which, on separation, forms a sludge. A portion of the sludge often is returned to the aerobic digestion process. This invention relates to an improvement for sludge reduction in these processes wherein a portion of the sludge is hydrolyzed and then subjected to biological digestion in an autothermal aerobic digestion zone. The effluent from the autothermal aerobic digestion zone usually is returned to the initial aerobic digestion process or submitted for disposal. In another embodiment of the invention, the hydrolyzed sludge is charged to an autothermal anaerobic digestion process wherein a substantial portion of the organic matter is converted into methane and the effluent from the autothermal anaerobic digestion process subsequently charged to the autothermal aerobic digestion process for effecting final reduction of organic matter. By these combinations one can generate a preselected value of sludge and, in some cases, one can operate under conditions such that there is no net generation of sludge.

Dependencies are inferred from the claim text.