Direct\nand Complete Phosphorus Recovery from Municipal\nWastewater Using a Hybrid Microfiltration-Forward Osmosis Membrane\nBioreactor Process with Seawater Brine as Draw Solution

Abstract

We\nreport a hybrid microfiltration-forward osmosis membrane bioreactor\n(MF-FOMBR) for direct phosphorus recovery from municipal wastewater\nin the course of its treatment. In the process, a forward osmosis\n(FO) membrane and a microfiltration (MF) membrane are operated in\nparallel in a bioreactor. FO membrane rejects the nutrients (e.g.,\nPO₄^3–, Ca²⁺, Mg²⁺, etc.) and results in their enrichment in the bioreactor. The nutrients\nare subsequently extracted via the MF membrane. Phosphorus is then\nrecovered from the nutrients enriched MF permeate via precipitation\nwithout addition of an external source of calcium or magnesium. The\nuse of seawater brine as a draw solution (DS) is another novel aspect\nof the system. The process achieved 90% removal of total organic carbon\nand 99% removal of NH₄⁺–N. 97.9% of phosphate\nphosphorus (PO₄^3––P) was rejected\nby the FO membrane and enriched within the bioreactor. >90% phosphorus\nrecovery was achieved at pH 9.0. The precipitates were predominantly\namorphous calcium phosphate with a phosphorus content of 11.1–13.3%.\nIn principal, this process can recover almost all the phosphorus,\napart from that assimilated by bacteria for growth. Global evaluation\nshowed an overall phosphorus recovery of 71.7% over 98 days.