Sewage sludge is produced in every sewage treatment plant and its properties depend on a number of factors. Type, origin and parameters of treated sewage and the applied treatment technology are the main factors influencing sludge properties. Produced sewage sludge can be submitted to treatment processes which condition its final use. For example sludge produced in small treatment plants, treating mainly domestic sewage, can be used for agricultural purposes. This paper presents the results of own research on the susceptibility of sludge originating from several municipal sewage treatment plants to selected treatment processes and changes in properties as a result of carried out processes. The obtained results confirm that the ultrasonic field as a physical method of sewage sludge modification is a factor intensifying the drainage processes. In most cases, the investigations have shown better results of the dewaterability of sludge treated with ultrasonic field in relation to raw sediments. For the tested sediments, it is justified to use the centrifugation process as a method of mechanical compaction.