The formation of sludge is an inevitable consequence of wastewater treatment processes. Their disposal and utilization requires knowledge on technology and engineering. The application of pretreatment processes/conditioning allows to obtain better mechanical properties of sludge. In the last decade a lot of research from around the world focused on new methods of conditioning of sludge can be noticed, i.e. The processes of disintegration, of which the destruction of the mechanical, chemical and biological. Despite different activities of each method (introduced energy, thermal phenomena, chemical reactions, mechanical), their common goal is the destruction of activated sludge floc structure and micro-organisms, which result in changes of properties in sediment and supernatant liquid. The influence of the disintegration of the microwave and freezing/thawing dry ice on selected properties of gravitational surplus activated sludge were presented. Characteristic parameters determined sludge sedimentation processes, i.e. the rate of descent and compaction density index sediment and sludge volume index and changes in the supernatant liquid. The study showed the efficacy of selected methods of sludge disintegration with regard to improving the properties of gravity and becoming a contribution to the determination of the effective methods of deposits’ preconditioning.