Enhanced ultrafiltration of Chlorella-laden water by far-ultraviolet irradiation-activated permanganate

Chlorella blooms in water bodies caused by eutrophication can pose a potential membrane fouling problem for ultrafiltration. In this study, an innovative combination of far-ultraviolet light (Far-UVC) and permanganate (Mn(Ⅶ)) mild pre-oxidation was proposed to mitigate ultrafiltration membrane fouling primarily induced by Chlorella pollutants. With 30 min Far-UVC/Mn(Ⅶ) treatment, the final J/J 0 surged by 0.65 compared with that of raw water, indicating a good improvement in flux, with R r and R ir respectively decreased by 98.8 % and 76.8 %. The results of the model fitting showed that membrane fouling changed from complete clogging to the cake filtration stage, and the clogging of membrane pores was significantly reduced. Meanwhile, the increase in interfacial free energy also made it difficult for pollutants to adhere to the membrane surface. Mechanism analysis revealed that HO· and reactive manganese (RMnS, including Mn(Ⅲ) and Mn(Ⅴ)) produced during combined pretreatment fulfilled a vital role in the removal of algal foulants. In addition, in situ formation of MnO 2 promoted the aggregation of algal cells, further reducing the fouling load. Under the electrostatic action of MnO 2 , the zeta potential of flocs declined from −21.1 mV to −4.7 mV, indicating a decrease in electrostatic repulsion, which could promote Chlorella cell aggregation. Simultaneously, the content of fluorescent components was also significantly reduced by the oxidation of HO· and RMnS. Far-UVC/Mn(Ⅶ) pretreatment maintained the integrity of Chlorella cells without causing significant damage, thereby preventing the release of intracellular organic matter and effectively reducing the accumulation of algal-related contaminants on the membrane surface. This work provides an effective way to alleviate membrane fouling induced by Chlorella -laden water and advances the practice of Far-UVC oxidation processes.