Osmotic Membrane Bioreactor and Its Hybrid Systems for Resource Recovery from Wastewater

Abstract

Osmotic membrane bioreactor (OMBR), which integrates forward osmosis (FO) with biological treatment process, has been recently developed to advance wastewater treatment and reuse. During OMBR operation, biologically treated water transports from the mixed liquor into a highly concentrated draw solution, through a semi-permeable FO membrane and driven by osmotic pressure gradient. Compared to conventional MBR, OMBR has several advantages, including better product water quality, lower fouling propensity, and higher fouling reversibility. OMBR can be operated in the osmotic dilution mode when the draw solution, such as liquid fertilizers or seawater, can be reused or discharged directly. In most cases, OMBR is integrated with an additional process, commonly including nanofiltration, reverse osmosis, membrane distillation, and electrodialysis, to form hybrid systems for sustainably reconcentrating draw solutions and producing clean water for reuse. In addition, several membrane processes, such as microfiltration, ultrafiltration, microbial fuel cell, and electrodialysis, are combined with OMBR to address its inherent issue, salinity build-up in the bioreactor, and 72achieve resource (e.g., nutrients and energy) recovery. Despite the promise of OMBR and its hybrid systems, several key factors should be optimized and/or addressed for their further development to recover resources from wastewater. These include salinity build-up in the bioreactor, membrane properties, draw solution types and concentration, and contaminant accumulation in the draw solution.