This paper describes an improvement to the aeration control at the Ljubljana wastewater treatment plant. Several changes were made to the existing aeration control. An adjustment to the parameters of the common air pressure controller contributes to a more responsive operation of the compressors. The introduction of the air pressure set-point controller adjusts the air pressure in the common air rail according to the changes in the plant load. The introduction of the airflow controllers reduces the variation in the oxygen concentrations in the aerobic reactors and, consequently, enables a reduction in the oxygen set-points. With the improved aeration control, savings of up to 10% in the electricity used for aeration are achieved on a yearly basis.