A critical review of electromagnetic fields, ultrasound, and nanobubbles for membrane fouling control and cleaning: Mechanisms, applications, challenges and opportunities

Membrane technologies are increasingly pivotal in advancing the circular economy by enabling efficient water recovery and supporting stricter environmental regulations through the reduction of emerging pollutant emissions. However, membrane fouling remains a critical barrier to optimal performance, long-term durability, and sustainability. To overcome this challenge, physical treatment devices (PTDs) including magnetic fields (MFs), electric fields (EFs), electromagnetic fields (EMFs), ultrasound (US), and micro/nanobubbles (MNBs) have emerged as environmentally friendly and sustainable alternatives to conventional chemical cleaning. This review critically examines the current state of research on these physical treatments, particularly focusing on their distinct and shared fouling control mechanisms, integration into membrane system configurations, and practical applications. Based on mechanistic analysis, this review highlights the potential synergistic effects of combining two different PTDs to enhance cleaning efficacy, reduce chemical dependence, and lower energy demand. Notably, combinations such as EFs with MNBs or EFs with US have demonstrated substantial improvements in fouling control, however, other combined configurations such as EMFs or US with MNBs remain underexplored and need further investigation. Furthermore, this review outlines the current research limitations and identifies key directions for future investigation, particularly regarding biofouling, its interactions with other fouling types, fouling control mechanisms, system-level optimization, synergistic effects from combined PTDs and engineering applications. Addressing these knowledge gaps is essential to fully unlock the potential of physical treatment and advancing more efficient, sustainable, and cost-effective membrane-based water treatment solutions. • PTDs are sustainable, chemical-free strategies for membrane fouling control. • Interconnected mechanisms of EMFs, US, and MNBs in fouling mitigation are elucidated. • Synergistic effects from combined PTD applications are highlighted. • Future directions are proposed to support scalable PTD integration.