Salinity build-up in osmotic membrane bioreactors: Causes, impacts, and potential cures

• Published in: Bioresource technology Vol. 257; pp. 301 - 310
• Main Authors: Song, Xiaoye, Xie, Ming, Li, Yun, Li, Guoxue, Luo, Wenhai
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.06.2018
• Subjects: Biological treatment; Draw solution; Forward osmosis (FO); Osmotic membrane bioreactor (OMBR); Salinity build-up; Osmotic membrane bioreactor (OMBR); Draw solution; Biological treatment; Forward osmosis (FO); Salinity build-up
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2018.02.101

•Fundamentals and potential of OMBR to advance water reuse is reviewed.•Mechanisms of salinity build-up in OMBR are elucidated.•Impacts of salinity build-up on OMBR performance are delineated.•Proposed strategies to mitigate salinity build-up in OMBR are evaluated.•OMBR optimization and modification are emphasized for managing salinity build-up. Osmotic membrane bioreactor (OMBR), which integrates forward osmosis (FO) with biological treatment, has been developed to advance wastewater treatment and reuse. OMBR is superior to conventional MBR, particularly in terms of higher effluent quality, lower membrane fouling propensity, and higher membrane fouling reversibility. Nevertheless, advancement and future deployment of OMBR are hindered by salinity build-up in the bioreactor (e.g., up to 50 mS/cm indicated by the mixed liquor conductivity), due to high salt rejection of the FO membrane and reverse diffusion of the draw solution. This review comprehensively elucidates the relative significance of these two mechanisms towards salinity build-up and its associated effects in OMBR operation. Recently proposed strategies to mitigate salinity build-up in OMBR are evaluated and compared to highlight their potential in practical applications. In addition, the complementarity of system optimization and modification to effectively manage salinity build-up are recommended for sustainable OMBR development.