Membrane bioreactor technology for greywater treatment: A review

This review critically evaluates membrane bioreactor (MBR) technology for greywater treatment, focusing on greywater characterization, MBR configurations, treatment processes, and reuse applications. MBR systems achieve high treatment efficiencies, with COD and TSS removal rates often exceeding 90% and 95%, respectively. The distinct characteristics of light and dark greywater, stemming from their varying pollutant loads, significantly influence MBR performance and must be considered during system design and operation. Most studies have been conducted at laboratory and pilot scales, with submerged and flat sheet membranes being the most commonly employed configurations. However, approximately 60% of the studies did not specify the membrane material, and 18% utilized PVDF membranes. Treatment-focused studies dominate the literature, while cost analyses and life cycle assessments (LCA) remain limited, revealing a significant gap in economic and environmental evaluations. Comparative analyses demonstrate that MBR systems outperform conventional methods, such as constructed wetlands and filtration, in terms of effluent quality and spatial efficiency. Pre-treatment processes, including sedimentation and fine filtration, are effective in mitigating membrane fouling, while post-treatment methods, such as UV disinfection and chlorination, ensure effluent suitability for reuse. Recent advancements, including gravity-driven MBRs, offer promising solutions for reducing energy consumption, making MBRs more suitable for decentralized applications. Reuse of treated greywater for irrigation, toilet flushing, and cleaning provides a sustainable approach to alleviate freshwater demand. However, further research is required to address operational challenges, optimize system performance, and develop regulatory frameworks that support the widespread implementation of greywater reuse with MBR technology.