Direct phosphorus recovery from municipal wastewater via osmotic membrane bioreactor (OMBR) for wastewater treatment

•Direct phosphorus recovery from municipal wastewater.•Sequesters phosphorus at the beginning of wastewater treatment.•Obviates the need for biological phosphorus removal.•Phosphorus recovery without addition of Mg2+ and Ca2+.•Potential complete phosphorus recovery from municipal wastewater.

This work reports, for the first time, a new approach to direct phosphorus recovery from municipal wastewater via an osmotic membrane bioreactor (OMBR). In the OMBR, organic matter and NH4+ were removed by biological activities. PO43−, Ca2+, Mg2+ and unconverted NH4+ were rejected by the forward osmosis (FO) membrane and enriched within the bioreactor. The resultant phosphorus-rich supernatant was then used for phosphorus recovery. By adjusting the pH to 8.0–9.5, PO43− was recovered via precipitation with Ca2+, Mg2+ and NH4+. The OMBR showed up to 98% overall removal of TOC and NH4+-N. At pH 9.0, more than 95% PO43−-P was recovered without addition of magnesium and calcium. The precipitates were predominantly amorphous calcium phosphate (ACP) with phosphorus content >11.0%. In principal, this process can recover almost all the phosphorus, apart from the portion assimilated by bacteria. The global phosphorus recovery efficiency was shown to be 50% over 84 days.

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