Abstract: A system for treating wastewater wherein the need for the addition of an external carbon source during the denitrification step is reduced or eliminated. In accordance with the system, the centrate is removed from the centrifuge at the end of the treatment process and is fed back into the denitrification zone, where it serves as a carbon source during the denitrification reaction. By eliminating the need for an external carbon source, the operating costs of the system are dramatically reduced. Furthermore, since the centrate is not fed into the wastewater stream entering the plant and is therefore not subjected to unnecessary processing, the process is more efficient than existing methods.