Gravity-Driven High Flux Filtration Behaviors and Microbial Community of an Integrated Granular Activated Carbon and Dynamic Membrane Bioreactor

Two gravity-driven dynamic membrane bioreactors (DMBRs) without and with granular activated carbon (GAC) addition (named as C-DMBR and G-DMBR) were operated under constant pressure filtration mode (using 20 cm water head) for real domestic wastewater treatment. During the stable operation period, the treatment performance, DM filtration behaviors and mechanism as well as microbial properties were comparatively studied. Both DMBRs showed stable removal of chemical oxygen demand (COD) and ammonia (NH 4 + -N) with average removal rates of 88% and 98% respectively. GAC addition effectively enhanced dynamic membrane (DM) permeability with a stable flux of 17-65 L/m 2 h, which was approximately four times higher than that in the C-DMBR without GAC addition. Filtration resistance analysis indicated the DM formation can be divided to three stages: the formation of the initial DM layer, the development of mature DM layer and dynamic equilibrium stage of the DM layer. Filtration model analysis illustrated that added GAC could be the skeleton of the DM, resulting in a more porous and incompressible DM layer. Additionally, microbial community analysis revealed that in the G-DMBR several fouling-causing phyla including Proteobacteria reduced while other phyla preferring attached growth such as Bacteroidetes and Gemmatimonadetes increased. Thus, adding GAC to the DMBR can be an effective strategy for achieving stable and high-flux operation by modifying sludge properties and regulating DM formation process and structure.