Nanofiltration-Based Membrane Bioreactor Operated under an Ultralow Flux: Fouling Behavior and Feasibility toward a Low-Carbon System for Municipal Wastewater Reuse
Chu Zhou, Senlin Shao, Keying Xiong, Chuyang Y. Tang
Abstract
Compared to a conventional membrane bioreactor (MBR) with a porous microfiltration (MF) membrane (MBR MF ), a nanofiltration (NF)-based MBR (MBR NF ) shows highly attractive features such as high permeate water quality. However, the practical applications of MBR NF are often hindered by the high driven pressures and severe membrane fouling. To address these two critical issues, this study investigated the feasibility of operating MBR NF at an ultralow flux (ULF, e.g., <5 L·m –2 ·h –1 ) toward the reuse of municipal wastewater in a single step. We operated the ULF MBR NF at a flux of 2 L·m –2 ·h –1 and benchmarked its performance against a conventional system using a MBR MF followed by a subsequent NF treatment (MBR MF + NF, both at a constant flux of 20 L·m –2 ·h –1 ). The results show that the ULF MBR NF achieved substantial removal of most pollutants, with low negative impacts of ultralow fluxes on pollutant rejections. Besides, the ultralow-flux operation led to a very low fouling rate (0.18 kPa·d –1 ). More importantly, the ULF MBR NF reduced carbon emissions by 45.2% compared with the MBR MF + NF, mainly due to less energy consumption by pumping. Our findings highlight the simplicity and great potential of ULF MBR NF for wastewater reuse.