A major influence in the biological treatment of wastewater is the aeration of the suspension of wastewater and activated sludge in reactors, that is, the efficiency of oxygen transfer from the gaseous phase to the suspension. Conventional systems of aeration of activated sludge suspension and wastewater, in reactors with diffusers that disperse air into fine bubbles, show a relatively inefficient transfer of oxygen from the gaseous phase to the activated sludge suspension because most of the supplied oxygen does not dissolve but goes unused into the atmosphere. Therefore, the pressurized aeration system (Supersaturated Dissolved Oxygen, SDOX) is proposed as an alternative for supplying dissolved oxygen. The aim of this work is to investigate how aeration at elevated pressure affects the process of removing nitrogen from wastewater through the processes of nitrification and denitrification, advanced biological removal of phosphorus from wastewater (EBPR), clogging of submersible membranes in a membrane bioreactor (MBR), sedimentation of active sludge and activated sludge particle size. The research will contribute to a better understanding of the impact of aeration at elevated pressure on the biological activity of activated sludge in wastewater treatment, on the efficiency of separating activated sludge from treated water by sedimentation in settling tanks, as well as a better insight into the problems of membrane clogging in MBR.