A review of combined fouling on high-pressure membranes in municipal wastewater reuse: Behaviors, mechanisms, and pretreatment mitigation strategies

High-pressure membrane technology has demonstrated remarkable efficacy in municipal wastewater reuse. However, membrane fouling remains a bottleneck hampering its development and widespread implementation. Given the coexistence of various organic, inorganic, and biological foulants in wastewater, their individual and combined fouling behaviors are complicated and could influence the fouling mitigation performance of pretreatment strategies. Herein, we provided a comprehensive review of the combined fouling behaviors on high-pressure membranes and the fouling mitigation performances of various pretreatment strategies. Initially, the membrane fouling behaviors and mechanisms of single types of foulants and their combination were discussed in-depth, along with a detailed examination of the complex fouling resulting from actual secondary effluent. Subsequently, the impact of the conventional pretreatment techniques on high-pressure membrane fouling was carefully evaluated, from both the positive and negative aspects. The influence of the coexistence and interaction of various types of foulants was particularly emphasized. Finally, the challenges that high-pressure membrane processes still confront and the future research directions in this field were highlighted.