Sulfate-assisted coagulation mitigates ultrafiltration membrane fouling by regulating the structure of the cake layer

Abstract

The ultrafiltration process has been widely used in drinking water treatment, but membrane contamination remains a major problem limiting its application. In this study, we investigated the impact of sulfate ions (SO₄^2-) on coagulation performance and subsequent ultrafiltration (UF). The results indicated that 0.5 mM sulfate with PACl₂₅-based coagulation significantly mitigates transmembrane pressure (TMP) development during continuous UF operation. Since the removal efficiency of organic matter was unaffected by the addition of sulfate, the variation in fouling observed in the experiment was mainly attributed to the changes in floc properties. The results showed that a moderate amount of sulfate ions promoted the formation of larger, looser floc particles, as well as the generation of a more crystalline filter cake layer. These microstructural changes not only helped to reduce membrane fouling but also made it easier to remove contaminants from the membrane surface by backwashing, thereby improving the operational efficiency and stability of the membrane filtration system. The findings of this study contributed to a deeper understanding of coagulation and membrane fouling processes in water treatment. Additionally, it provided theoretical support and practical guidance for optimizing membrane filtration.