Sulfate-Assisted Coagulation Mitigates Ultrafiltration Membrane Fouling by Regulating the Structure of Cake Layer

Abstract

The ultrafiltration process has been widely used in the treatment of drinking water, but membrane contamination remains a major problem limiting its application. In this study, we investigated the impact of sulfate ions (SO42-) on the performance of the coagulation and subsequent ultrafiltration (UF). The results indicated 0.5 mM sulfate in conjunction with PACl25-based coagulation significantly mitigate 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 not only contribute to a deeper understanding of the physicochemical processes of coagulation and membrane fouling in water quality treatment, but also provide theoretical support and practical guidance for optimizing the membrane filtration process.

Keywords: coagulation, sulfate, ultrafiltration, Membrane fouling, nano-scale primary particles