The Wilderness Wastewater Treatment Plant (WWTP) located in Orange County, Virginia is a four concentric ring oxidation ditch activated sludge system with a rated capacity of 1,935 m(3)/day. The three outer rings are used for wastewater treatment and the inner ring is used as an aerobic digester. The flow capacity has been increased from 1,935 to 3,760 m(3)/d, however, the desired design capacity has since been increased to 3,870 m(3)/d, and there are plans to eventually expand to approximately 4,840 m(3)/d with improved nitrogen removal. The design goal for the planned upgrade is to discharge an effluent that contains less than 10 mg/l total nitrogen (TN) at all times, with an annual average of 8 mg/l or less. In this study, the pre-upgrade performance of the Wilderness Wastewater Treatment Plant was evaluated and several modifications were recommended for the incorporation of biological nutrient removal (BNR).