Consequently, the key to improve the performance of the mainstream combination of AD and nitritation–anammox is to ensure sufficient biomass to offset the slow growth rate of AD and anammox bacteria under ambient temperature. Adopting MBR into the mainline combination of AD and nitritation–anammox can facilitate rapid start up process and high growth rate of slow-growing bacteria with complete biomass retention. As a result, MBR can provide an alternative strategy for low-strength wastewater treatment, with the potential for high biogas recovery and high-quality effluent [13],