Revealing the fouling characteristics in membrane-based primary treatment (MPT) of municipal wastewater and the antifouling mechanism of influent conditioning

Abstract

Membrane-based technology is becoming an attractive option for primary treatment of municipal wastewater (MW) due to its superior organic retention capacity and footprint savings. However, limited understanding of fouling mechanisms still hampered its practical application. This study aims to investigate the fouling characteristics in MPT and analyze anti-fouling mechanisms of influent conditioning. In the meantime, the differences between microfiltration (MF) and ultrafiltration (UF) are also discussed. Dozens of filtration experiments with different membranes (0.1 μm and 100 kDa), MW conditioning methods (coagulation and adsorption) were conducted. Results indicated that a hallmark of MPT is the protective ability of particulate matters present in the raw MW. The irreversible fouling rate was 2–4 times higher in the absence of particulates. Besides, the main irreversible foulant types and the cake growth patterns differed with different pore sizes. As for influent conditioning, coagulation and adsorption collaborate effectively in regulating cake characteristics. Polymeric aluminum chloride reduces the tendency of binding between foulants and membrane, while activated carbon increases the porosity of the cake layer.