(324e) Hybrid Osmotic Membrane Bioreactor for Municipal Wastewater Treatment, Water Reclamation and Resource Recovery

Osmotic membrane bioreactor (OMBR) technology, which integrates forward osmosis (FO) and biological treatment, is receiving increasing attention in recent years. Compared to membrane bioreactor, OMBR shows unprecedented advantages, such as low membrane fouling, potential low energy consumption, high product water quality and enhanced removal of emerging pollutants, which extremely favorable for water reclamation. Additionally it offers the advantage in nutrient removal and recovery. Unfortunately, salt accumulation is a major drawback of this novel process. In this work, a hybrid OMBR was developed by combining a microfiltration membrane within the reactor for the control of salinity buildup. Cellulose triacetate (CTA) FO membrane and thin-film composite (TFC) FO membrane were used for comparison. With raw municipal wastewater (COD, NH₄⁺-N and PO₄^3--P concentrations at 350-500 mg/L, 40-55mg/L and 5.0-8.0 mg/L, respectively) as an influent and 1M NaCl as a draw solution (DS), both reactors (employing CTA FO membrane and TFC FO membrane, respectively) achieved >90% removal of organic matter and 99% removal of NH₄⁺-N. Up to 99% PO₄³⁺-P was rejected by the FO membranes and was recovered as calcium/magnesium phosphates in a side stream phosphorus recovery process without addition of an external source of calcium or magnesium. Compared to the CTA membrane, TFC membrane showed significantly higher (around 50%) water flux and lower (around 50%) salt leakage, which resulted in a lower (up to 30%) steady-state salt concentration in the bioreactor. Additionally, TFC FO membrane showed higher rejection to both organic matters and nitrogen (especially, NO₂^--N and NO₃^--N), which resulted in lower TOC and NO₃^--N concentrations in the DS.

Keywords: Osmotic membrane bioreactor (OMBR); microfiltration; Cellulose triacetate (CTA) membrane; thin-film composite (TFC) membrane; municipal wastewater treatment; water reclamation.