Membrane design for extractive membrane bioreactor (EMBR): Mass transport, developments, and deployment

Economic development throughout the world is generating harmful contaminants which are progressively damaging water reservoirs, groundwater, soil, ecosystems, and organisms. Thus, there is an urgent need to remove these pollutants economically and in an eco-friendly way before their discharge to the environment. The novel extractive membrane bioreactor (EMBR) system requires less energy, produces high-quality water, and presents higher removal efficiency with zero by-products and thus has attracted attention as a somewhat niche but potentially viable alternative to traditional technologies. The EMBR has been progressed in recent years with new design of membranes and configurations for removing a variety of emerging pollutants. However, the practical use of EMBR technology remains a challenge due to two factors: (i) the availability of appropriate membranes and (ii) membrane fouling issue. In this review, the principles of the EMBR process are explained. Then, the performance of membranes for pollutant extraction is discussed based on various experimental results and theoretical considerations. State-of-the art membrane manufacturing techniques are also reviewed to assist with an assessment of the long-term sustainable development of the EMBR process. To achieve an economical process, there will need to be not only technological progress but also an appropriate evaluation of the environmental benefits.