Performance and mechanism of gravity-driven membrane bioreactor for rural wastewater treatment

Abstract:

Gravity-driven membrane bioreactor (GDMBR) confers the process characteristics of low energy consumption, low maintenance and stable effluent. However, there is limited research on the direct treatment of rural domestic wastewater. This study investigates the pattern of flux variation and removal efficiency of pollutants using GDMBR process to treat domestic wastewater, as well as the influence of different membrane pore sizes on the treatment of domestic wastewater using GDMBR. The results indicate that the membrane flux of GDMBR process can be maintained at a steady state without any cleaning procedures during the long-term filtration in treating the domestic wastewater, with a steady flux of 1.3-1.5 L/(m²·h). This is attributed to the formation of loose and porous structure within the bio-cake layer attached on the membrane surface, resulting in extremely low concentration of pollutants deposited within the membrane pores. With relatively low sludge concentration, the GDMBR process achieves high removal efficiency of COD and UV₂₅₄. The removal rates of 78% and 85%, respectively, while effectively retaining the nitrogen and phosphorus sources in the wastewater. Furthermore, different membrane pore sizes exhibits minimal effects on the removal efficiency of GDMBR process. However, the steady fluxes of the GDMBR system configured with microfiltration membranes are slightly higher than the GDMBR system integrated with ultrafiltration membranes.