Rejection of viruses and mobile genetic elements by ceramic ultrafiltration membranes: impacts of operational conditions and implications for water reuse system performance validation

Virus removal by ultrafiltration (UF) membranes is crucial for ensuring safe water reuse practices as part of a multi-barrier system, yet removal efficiency can vary as a function of operational conditions. This study investigated the removal of viruses and mobile genetic elements by a ceramic UF membrane, focusing on the influence of zeta potential and transmembrane pressure interactions, and evaluating the effects of different pretreatment strategies, including coagulation and ozonation. Laboratory-scale experiments demonstrated that bacteriophage removal (MS2 and PhiX174) varies strongly as a function of the state of the filtration cycle and degree of fouling. Under pre-fouled conditions, the removal efficiency decreased notably as compared to non-fouled conditions, especially for PhiX174, as electrostatic charge interactions were diminished due to the fouling cake layer. Pilot-scale validation confirmed these trends, revealing that virus removal efficiencies varied depending on the duration of the filtration cycle, the wastewater matrix composition and its influence on fouling, and the coagulation effectiveness. These findings emphasize the need for a dynamic validation framework to consider a broader range of surrogates with diverse surface properties, or, at a minimum, be based on worst-case removal performance. This ensures regulatory compliance and proper virus retention in ceramic UF-based reuse systems.