Enhanced Biological Phosphorus Removal Performance of the Traverse City MBR

The Traverse City (Michigan) Regional Wastewater Treatment Plant has been successfully converted from a conventional plant into a membrane bioreactor-based facility. When commissioned in July 2004, the plant was the largest Membrane Bioreactor (MBR) facility in North America (32,000 m3/day, 8.5 mgd, during the maximum month). The facility is designed to achieve strict effluent Phosphorus requirements using a combination of Enhanced Biological Phosphorus Removal (EBPR) and chemical precipitation. This paper presents the results of the investigation of EBPR design and operational principles at the Traverse City MBR facility. Robust EBPR was established for an eight week period, and a total phosphorus concentration of 0.05 mg/L to 0.1 mg/L was achieved during that time with minimal use of metal salt chemicals within the plant. Excursions to higher phosphorus concentrations have continued to occur on occasion, and possible causes are identified and evaluated. The paper includes evaluation of seasonal temperature effects, available Volatile Fatty Acid (VFA) concentrations, and recycles from the anaerobic digester dewatering and decanting operations.