5 - Membrane bioreactors for water treatment

Abstract

Membrane bioreactor (MBR) technology combines the biological degradation process with micro- and ultrafiltration and is widely regarded as an effective tool for water treatment and water reuse owing to its high-quality water product and low footprint. MBR technology–treated water is of high clarity and is significantly reduced in germs so that it is ideally suited for being discharged to sensitive receiving waters such as natural reserve areas or for being reused in a variety of applications such as irrigation or industrial processes. Aerobic MBRs, which make use of the aerobic-activated sludge process, are widely used to treat municipal and industrial wastewater, and a variety of membranes are commercially available. Because of their robustness and flexibility, submerged MBR systems are increasingly preferable. Because of increasing water scarcity, the aerobic MBR market is witnessing strong growth worldwide, particularly in large-scale applications. In addition to aerobic MBRs, anaerobic MBRs (AnMBR) have become the focus of attention in research and development because these systems have the ability to provide biogas for energy production. Membrane fouling and water flux decline are the most important issues in MBR application. In general, membrane fouling problems are more pronounced in AnMBRs; this hampers the widespread application of full-scale reactors. In addition to the common pressure-driven MBRs, the combination of forward osmosis and biological degradation has aroused the interest of researchers in recent years owing to its superior water quality and the fact that no pump energy is needed to drive the membrane separation process. This chapter highlights the fundamentals of MBRs. In addition, areas of application, factors affecting the process, and case studies of aerobic and AnMBR processes for water treatment and reuse in the laundry and food industry are addressed. The case studies demonstrate the technical benefits of MBR technology but also show the economical viability of this technology.