Formation and performance of self-forming dynamic membrane (SFDM) in membrane bioreactor (MBR) for treating low-strength wastewater

Abstract

This study introduces a self-forming dynamic membrane (SFDM) with large-pore mesh filter materials instead of conventional MF/UF membranes for wastewater treatment. Development of SFDM on the mesh filter surface plays a major role in reducing the wastewater turbidity and its performance in a self-formation dynamic membrane bioreactor (SFDMBR). To evaluate formation of the dynamic membrane, biological and hydrodynamic parameters, including mixed liquor suspended solids (MLSS) and aeration rate, were examined. The experimental results showed that with elevation of MLSS in the bioreactor (up to MLSS = 9,000 mg/L), the effluent turbidity diminishes with rapid formation of SFDM, with the shortest formation time (5 min) obtained in SFDM operations, though it results in increased membrane fouling. SFDM was well formed at low aeration rates of 2.5 L/min and 5 L/min, due to very low shear stress on the mesh filter surface, given the results of turbidity in comparison with aeration rates of 10 L/min and 15 L/min. The filtration performance of SFDM in treatment of synthetic wastewater was tested under a constant operational flux (58 L/m2 h). Total chemical oxygen demand (COD) and NH4-N removals were 88-93% and 96-98.8%, respectively. These results indicated that the treatment process can be performed effectively by SFDMBR.