The region just downstream of the brush aerators is aerobic so nitrification occurs. As the liquor travels downstream and the oxygen is consumed, an anaerobic zone is formed. The mixed liquor then contacts another brush aerator so that the organic nitrogen produced by the denitrifying bacteria is oxidized. The number of anaerobic zones and aerators required is a design parameter that depends on the capacity and loading of the plant. Denitrifying oxidation ditches are capable of extremely high efficiencies.
Oxidation ditches are also one of the easiest wastewater processes to operate and maintain.
Land is often simply too expensive in high density population regions that could benefit from the high efficiency rates associated with a modern oxidation ditch.