| Many wastewater treatment plants (WWTP) in the United States are facing new and previously unregulated phosphorus discharge limits from government regulatory agencies. While conventional enhanced biological phosphorus removal (EBPR) design criteria is proven and easily incorporated into the construction of new WWTPs, pre-existing WWTP often have site and capital constraints that make conventional EBPR designs costly and difficult to implement. A full-scale novel side stream EBPR configuration was implemented and tested at Metro Wastewater Reclamation District's Robert W. Hite Treatment Facility in Denver, Colorado. By design, the side stream EBPR configuration shows advantage over mainstream EBPR configurations because the integrity of the anaerobic zone is protected from downstream electron acceptors and high suspended solids concentrations in the side stream reactor allows for a minimal footprint. The results from an eight month 106 MGD demonstration showed excellent EBPR process performance. The attributes that make this EBPR configuration unique are the carbon requirement for anaerobic volatile fatty acid uptake is satisfied with gravity thickener overflow and the configuration required minimal construction and modifications to existing infrastructure for implementation. During the proof-of-concept test phase the novel EBPR configuration produced an average effluent total phosphorus concentration equal to 0.58 mg-P/L and a phosphate concentration of 0.11 mg-P/L. Evaluation of the novel EBPR configuration involved a detailed characterization of the gravity thickener overflow and extensive phosphate profiling throughout the secondary treatment complex. The design of the side stream EBPR configuration, process considerations, results of the study and future design considerations are discussed. |
