| A two-year nutrient removal study was conducted at McDowell Creek Wastewater Treatment Plant in Charlotte, North Carolina. The overall objective of the research was to evaluate performance and operational costs for three biological nutrient removal schemes implemented at the plant, including documenting and monitoring effluent nitrogen and phosphorus levels for each configuration, and tracking the operations and chemical input costs for operation. The nutrient removal schemes evaluated included the University of Cape Town/Virginia Initiative Plant (UCT/VIP) process, the Charlotte North Carolina (CNC) process, and the modified Orange Water and Sewer Authority (OWASA) process. All processes were successful in removing phosphorus and nitrogen from the wastewater to meet permit limits of 1 mg/L and 10 mg/L, respectively. All processes required supplemental acetic acid feed to assist in anaerobic phosphorus release. Problems with process stability were encountered due to the plant expansion underway, and it was discovered that each process must be closely monitored to ensure efficient removal. Low levels of alum addition for phosphorus precipitation were necessary to meet regulatory limits during periods of instability. |
