Recent advances of membrane fouling characterization in membrane based wastewater treatment

Membrane technology has become an important technology in the water treatment industry due to its advantages of high separation efficiency， stable performance and good effluent quality.　However， membrane fouling—leading to membrane flux decline， shortened operational cycles， and increased treatment costs—remains a critical bottleneck hindering the further development of this technology. To accurately analyze pollutant composition， elucidate the spatial structural characteristics of fouling layers， dynamically monitor pollution evolution patterns， and clarify underlying mechanisms， the scientific selection and application of membrane fouling characterization methods are essential. This review focuses on membrane fouling issues in membrane-based wastewater treatment. Based on the spatiotemporal resolution of characterization techniques， fouling characterization methods are classified into three categories： ex-situ characterization， in-situ characterization， and real-time monitoring. The principles， technical advantages， and application limitations of each method are systematically reviewed and compared. By discussing applicable scenarios for each method， this work provides insights to deepen the mechanistic understanding of membrane fouling and advance the development of fouling control strategies.