Abstract: The present invention relates to a device and a process for thickening and conveying waste water sludges, especially with a centrifuge. Here, the centrifuge has at least one lysis device for the breaking down of cells of organisms contained in the waste water sludges. The lysis device of the device of the invention may take the form, for example, of a friction grinder (100; 200) with grinding discs (161, 162) or a milling cone, a shaped rasp, a roller crusher, a passing drum, a cutting unit with rows of rotary cutters or a pin grinder with rows of rotating pins. The device of the invention is capable of the lysis of cells, especially those of bacteria and protozoons so that their cell content discharges into the surrounding medium which then acts as a simulation reagent for the bacteria still present in the sludge, so that on the one hand the total quantity of sludge can be greatly reduced and on the other the bio-gas yield is considerably increased.