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

Abstract

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. PO4(3)(-), Ca(2+), Mg(2+) 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, PO4(3)(-) was recovered via precipitation with Ca(2+), Mg(2+) and NH4(+). The OMBR showed up to 98% overall removal of TOC and NH4(+)-N. At pH 9.0, more than 95% PO4(3)(-)-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.

Keywords: Amorphous calcium phosphate (ACP); Municipal wastewater; Osmotic membrane bioreactor (OMBR); Phosphorus recovery; Struvite.