Ultrasonication-assisted fouling control during ceramic membrane filtration of primary wastewater under gravity-driven and constant flux conditions

Abstract

This study investigated the feasibility of using ultrasonication as a ceramic microfiltration membrane fouling control strategy during gravity-driven membrane (GDM) filtration and constant flux filtration of primary municipal wastewater. The fouling model fitting curves revealed that initial intermediate pore blocking was dominant in the GDM system, followed by cake filtration; while cake filtration was dominant during constant flux filtration with a continuously increasing pattern. In the GDM system, periodic ultrasonication cleaning achieved higher cake resistance reduction (∼60 % vs ∼ 26 %) and led to lower specific cake resistances (0.2–2.0 × 107vs 29.6–59.3 × 107 m/mg) compared to periodic backwash. Ultrasonication-facilitated fouling mitigation effectiveness was related to cake properties (such as cake foulant density and porosity) and improved with extending ultrasonication duration. The foulant examination indicated that ultrasonication may result in porous cake nature by cake expansion and facilitate detaching particulate foulants and soluble organics (such as biopolymers) from the membrane. Cost analysis revealed that with commercial ceramic membranes, ultrasonication-facilitated GDM systems are economically feasible for treating wastewater at a household scale (∼1.1 EUR/m3 water), while ultrasonication-facilitated constant flux filtration systems are favorable at a small-community scale (∼0.5 EUR/m3 water). Furthermore, it was predicted that the use of low-cost recycled ceramic membranes would allow GDM systems as economical decentralized wastewater treatment processes due to their lower water production cost (∼0.16 EUR/m3 water) with easy operation and maintenance.