Between a Rock and a Hard Place: Microfiltration and Reverse Osmosis To Achieve Ultra-Low Total Phosphorus Concentrations

A one-year Demonstration Study conducted by the Regional Municipality of York (York Region) demonstrated the ability of membrane technology including microfiltration (MF) and reverse osmosis (RO) following biological treatment of municipal wastewater to consistently and reliably achieve an ultra-low total phosphorus (TP) concentration of less than 20 micrograms phosphorus per liter (μg P/L). The study provided valuable data and operational insight which was previously unavailable. Key design and operational parameters of the membrane systems included flux, recovery, normalized permeability, chemical usage, and backwash/cleaning regimes and frequencies. The majority of TP concentrations in MF permeate samples were less than 40 μg/L, and TP concentrations in approximately 70 percent of the RO permeate samples were reported as less than the Method Detection Limit of 2 μg/L.While the sustainability case for advanced treatment is unique to the project circumstances, York Region's Demonstration Study of MF and RO helps to advance all aspects of the Region's preferred alternative for wastewater servicing. In addition to use of advanced treatment processes to produce an ultra-low TP concentration, the preferred alternative includes alternative methods to reduce phosphorus loading such as water reuse and project-specific phosphorus offsets.