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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