Forward osmosis membrane bioreactor for wastewater treatment with phosphorus recovery

• A forward osmosis membrane bioreactor (OMBR) was tested with TFC membrane.
• Flocculated sludge and aerobic granules were the seeds to OMBR.
• The OMBR showed 96%, 43% and 100% removals of PO43--P, NH4+-N, TOC.
• Phosphorus in supernatant was recovered by pH adjustment.
• At pH 8.5 with 2.65–2.71 g 3 M NaOH/g-P, 814–817 mg-P/L was recovered.

A forward osmosis membrane bioreactor (OMBR) with a thin film composite membrane was seeded with flocculated sludge and aerobic granules to treat a synthetic wastewater with 1 M NaCl as draw solution. The tested OMBR showed 96%, 43% and 100% removal of PO43−-P, NH4+-N, and total organic carbon. Salinity was accumulated in OMBR principally owing to membrane rejection and salt leakage from draw solution. At high salinity level membrane fouling could be induced. Intermittent withdrawal and replenishment of supernatant from OMBR maintained its operation stability, while phosphorus in withdrawn supernatant was recovered by pH adjustment. The OMBR enriched phosphorus concentration from 156 mg/L in feed solution to 890–990 mg/L. At pH 8.5 with 2.65–2.71 g 3 M NaOH/g-P, 814–817 mg-P/L was recovered in the form of sodium hydrogen phosphite hydrate. The OMBR is a volatile wastewater treatment unit with capability for enrichment and recovery of phosphorus at reduced chemical costs.

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