Process for the further processing of raw sludge taken off from a biological waste water (effluent) purification plant

摘要

Process for the further processing of raw sludge taken off from a biological waste water purification plant to give, on the one hand, digestion gas and, on the other hand, a landfillable and/or utilisable product in a biological sludge treatment plant having a first anaerobic treatment stage operated as an acidification stage and a second anaerobic treatment stage operated as a methanation stage. The acidification and methanation are carried out in structurally separate plant sections each having downstream, covered and insulated settling tanks for external biomass retention. The return sludge circulations are separate and the cultivation and enrichment of support-immobilised biomasses is carried out in independent reactors. The raw sludge to be introduced into the acidification stage is adjusted by thickening and/or decanting to a dry matter content of 5 to 12%, preferably about 9%. In the acidification stage and in the methanation stage, biomass return is carried out. Because of the very different residence times in the acidification reactor and methanation reactor, different biocoenoses can be cultured and optimal environmental conditions can be employed. A plant for carrying out the process is depicted below (Fig. 1). An extension of the plant by additional internal biomass circulation is likewise depicted below.