Membrane fouling is an inevitable consequence of the membrane operation process. Coagulation/flocculation is simple, effective, and low-cost membrane pretreatment method. The performance of coagulation/flocculation, including its coupling processes with other pretreatment technologies, in controlling pressure-driven membrane fouling has been reviewed in detail according to fouling type (including inorganic, organic, and microbial fouling) in this paper. The development prospects of this technology are also explored to further improve its application performance. Coagulation/flocculation generally shows high efficiency in removal of insoluble inorganic, organic and microbial colloids in effluents by charge neutralization, bridging and sweeping effects to thus mitigate membrane fouling. For soluble matter, especially for low molecular-weight ones, the mitigation effect highly depends on the selected coagulant/flocculant, in addition to the coupling pretreatment technologies. A desired coagulant/flocculant can effectively bind to and transform the solute from hydrophilic to hydrophobic by some valid interactions, and cause an easy destabilization, aggregation and final formation of large and loose flocs. The resultant flocs can be trapped on the membrane and further form loose and porous cake layer, thus increasing membrane flux, decreasing membrane resistance, and alleviating membrane fouling. Based on an improved understanding of the membrane fouling and also coagulation/flocculation mechanisms at the molecular levels, designing and selecting an advanced coagulant/flocculant, with the advantages of high performance, environmental friendliness and low cost, is crucial to achieve the desired pretreatment effect.
中文翻译：
在膜分离过程中，通过混凝/絮凝作为预处理来缓解压力驱动膜污染的综述
膜结垢是膜作过程中不可避免的结果。混凝/絮凝是一种简单、有效、成本低廉的膜预处理方法。本文根据结垢类型（包括无机、有机和微生物结垢）详细综述了混凝/絮凝及其与其他预处理技术的耦合过程在控制压力驱动膜结垢方面的性能。并探讨了该技术的发展前景，以进一步提高其应用性能。混凝/絮凝通常表现出较高的效率，通过电荷中和、桥接和扫地作用去除出水中不溶性无机、有机和微生物胶体，从而减轻膜结垢。对于可溶性物质，特别是低分子量物质，除了偶联预处理技术外，缓解效果在很大程度上取决于所选择的混凝剂/絮凝剂。所需的混凝剂/絮凝剂可以通过一些有效的相互作用有效地结合溶质并将其从亲水性转化为疏水性，并容易导致不稳定、聚集并最终形成大而松散的絮凝体。所得絮凝物可以捕获在膜上，进一步形成松散多孔的滤饼层，从而增加膜通量，降低膜阻力，减轻膜结垢。在对膜结垢和分子水平的混凝/絮凝机理的加深认识的基础上，设计和选择具有高性能、环保和低成本等优点的先进混凝剂/絮凝剂对于达到预期的预处理效果至关重要。
