Advanced hybridization of coagulation–ultrafiltration systems: A critical techno-economic review of integration strategies

Coagulation pretreatment has become indispensable for low-pressure membrane processes, together forming a cost-effective and efficient water treatment solution, particularly beneficial for developing economies. A critical techno-economic evaluation of advanced hybridization of the traditional coagulation ultrafiltration (CUF) process to overcome its limitations and address emerging challenges in the field is presented in this review. Confusion persists regarding nomenclature, process selection, and categorization of such hybrid treatment processes. This study seeks to critically review and organize recent works shaping the outlook of fifteen key hybrid CUF processes to establish a systematic framework within the seemingly disordered array of recent literature. Key factors influencing the combined C + UF process are analyzed, opportunities are identified, and effective strategies for integration are proposed. Future research may prioritize the investigation of underexplored parameters such as sustainability metrics, toxic by-product formation potential (TBP-FP), pulse dosing strategies, intralayer floc charge distribution, temperature-superparamagnetism, interfacial free energy, specific gas nanobubbles, tailored hybrid flocculants, and scalability. This review highlights the cascading influence of several such factors on hybrid CUF system performance and aims to delineate pathways for advancing system efficiency, sustainability, and adaptability.