Toward in situ characterization for advancing membrane performance in water treatment processes

• Membrane technology greatly improved water treatment efficiency was illustrated. • Ex situ characterization techniques enhanced membrane behaviors was reviewed. • In situ characterization techniques for behavior enhancement were discussed. Membrane technology has significant potential for addressing global water crises because membranes, with precisely defined pore structures at the molecular level and multifunctional groups, serve as selective permeation barriers. Over the past few decades, ex situ characterization techniques (e.g., scanning electron microscopy) have been employed to examine the morphology and chemical composition of membranes. However, the rise of in situ characterization methods, such as in situ transmission electron microscopy, is a promising frontier. These techniques allow for the real-time investigation of membrane structure and performance on relevant temporal and spatial scales, with the potential to significantly enhance membrane efficiency. This study elucidates the challenges and opportunities associated with in situ characterization, which provides critical information on membranes within their actual operating environments, eliminating the need for dedicated sample preparation. By focusing on in situ characterization techniques, our goal is to substantially improve membrane performance through a deeper understanding and optimization of membrane fabrication, filtration, and cleaning processes, which can ultimately contribute to carbon footprint reduction.