Oxidation and coagulation/adsorption dual effects of ferrate (VI) pretreatment on organics removal and membrane fouling alleviation in UF process during secondary effluent treatment

• Published in: The Science of the total environment 2022-12, Vol.850, p.157986-157986, Article 157986
• Main Authors: Ding, An, Ren, Zixiao, Hu, Lei, Zhang, Rourou, Ngo, Huu Hao, Lv, Dongwei, Nan, Jun, Li, Guibai, Ma, Jun
• Format: Article
• Language: English
• Subjects: Membrane fouling mechanism; Oxidation/coagulation; Potassium ferrate; Ultrafiltration; Wastewater reuse
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2022.157986

Ultrafiltration (UF) has been widely used in water and advanced sewage treatment. Unfortunately, membrane fouling is still the main obstacle to further improvement in the system. Fe (III) salt, a type of traditional coagulant, is often applied to mitigate UF membrane fouling. However, low molecule organic weight cannot be effectively removed, thus the water quality after single coagulation treatment does not effectively meet the standard of subsequent water reuse during secondary effluent treatment. Recently, it has been found that potassium ferrate (Fe (VI)) has multiple functions of oxidation, sterilization and coagulation, with other studies proving its good performance in organics removal and membrane fouling mitigation. However, the respective contributions of oxidation and coagulation/adsorption have not yet been fully understood. The oxidation and coagulation/adsorption effects of Fe (VI) during membrane fouling mitigation were investigated here. The oxidation effect of Fe (VI) was the main reason for organics with the MW of 8–20 kDa removal, and its coagulation/adsorption mainly accounted for the smaller amounts of molecular organics removed. The oxidation of Fe (VI) was the main method for overcoming membrane fouling in the initial filtration; it largely alleviated the standard blockage. The formation of a cake layer transformed the main membrane fouling alleviation mechanism from oxidation to coagulation/adsorption and further removed smaller amounts of molecule organics with the increase of filtration cycles and Fe (VI) dosages. The main fouling mechanism altered from standard blocking and cake filtration to only cake filtration after Fe (VI) treatment. Overall, the mechanism of the oxidation and coagulation/adsorption of Fe (VI) were differentiated, and would provide a reference for future Fe (VI) pretreatment in UF membrane fouling control during water and wastewater treatments. [Display omitted] •Fe (VI) was applied to UF process for secondary effluent treatment and reuse.•Oxidation and coagulation/adsorption effects of Fe (VI) on fouling control were distinguished.•Oxidation was the main method for retarding pore blocking in the initial filtration.•The contribution of coagulation/adsorption improved with increases of filtration period and Fe (VI) dosage.•Fe (VI) may replace common coagulants for pollutant removal and UF fouling control.