Yao Tangchun,Chen Yichao,Wu Wenting,Jin Binbin,Xiao Hua,Wang Qing,Wang Ao,Xu Hang
In this study, we utilized direct ultrafiltration (UF) and integrated microflocculation–ultrafiltration (MF–UF) processes to treat raw water from four distinct sources, covering both dry and heavy rainfall periods. We assessed the effectiveness of microflocculation (MF) as a pretreatment to enhance treatment efficiency under complex water conditions, focusing on its role in mitigating membrane fouling. The results demonstrated the superior adaptability of UF membranes when combined with MF pretreatment, particularly in managing high turbidity during heavy rainfall, a challenge for standalone UF processes in meeting regulatory standards. This integrated approach notably improved UV254 removal efficiency from approximately 60–80%. Additionally, excitation–emission matrix spectroscopy revealed that while the MF–UF process is effective in removing dissolved organic matter (DOM), it faces limitations with high DOM concentrations in raw water. Comparative analysis of membrane flux between the two methods showed that MF pretreatment reduces filtration time, enhances flux rates, and significantly decreases membrane fouling. Finally, scanning electron microscopy further provided insights into the structure and morphology of UF membrane surface filter cakes, illustrating how MF pretreatment contributes to the sustained efficiency of membrane flux. The different water quality conditions were studied. The MF–UF process was studied in realistic conditions. Organic matter and hard particulate matter were studied. Elucidating mechanisms to the MF–UF membrane flux efficiency.
Lei Xu,Chaocheng Wei,Muhammad Saboor Siddique,Wenzheng Yu
Membrane fouling is an inevitable drawback of the membrane based long-term operations. In this study, we investigated a spontaneous galvanic process for membrane fouling mitigation, which termed as the in-situ galvanic micro-coagulation (GMC) process. Results demonstrated that the GMC contributed to a lower transmembrane pressure development in contrast with the control system (7.15 vs 14.11 KPa/LMH/cP for about 1200 h operation). Significantly, a reduced concentration of extracellular polymeric substances (EPS) in terms of polysaccharides and proteins was observed for the GMC system on both the membrane surface and membrane pores, in comparison with the control system i.e. (134.09 ± 7.37 vs 379.55 ± 9.64 μg/cm 2 of polysaccharides and 27.48 ± 2.48 vs 35.87 ± 3.53 μg/cm 2 of proteins) and (70.46 ± 1.93 vs 120.46 ± 3.21 μg/cm 2 of polysaccharides and 17.96 ± 1.39 vs 20.52 ± 2.12 μg/cm 2 of proteins) respectively. Additionally, higher accumulation of EPS on the membrane surface of control system results in higher roughness of biofilm, lower porosity, robust and thicker biopolymer microstructure as compared to the GMC system. This kind of morphology and biofilm structure formed on the membrane surface of control system directly contributed to the higher transmembrane pressure. Overall, this work shows a potentially feasible and promising approach for membrane fouling mitigation, especially for the decentralized system with relatively low permeate flux .
Due to seasonal algal outbreaks in source water, the sand filtration (SF) suffering high load exhibited poor performance in turbidity and organic matter (OM) removal. However, the filtration performance is highly dependent on the state of contaminants. This study aims to improve removal efficiency of turbidity, algae and DOM by coupling a novel green titanium sulfate-chitosan (TS-CTS) compound filter aids with/without ferrate (VI) pre-oxidation. The results indicated that the turbidity decreased to 0.25 NTU and chlorophyll a removal up to 73.5% with TS/CTS (0.8/0.3 mg/L) filter aids were utilized, while the filtration cycle was not significantly shortened. The introduced Fe(VI) (5 mg/L, 10 min) before micro-flocculation realized moderate pre-oxidation and formed in-situ Fe(III), improved algae cells removal and effectively controlled of 2-methylisoborneol (＜10 ng/L) as well as the disinfection by-product precursors as polysaccharides and amino acid-like proteins. Positively charged in-situ Fe(III) as a dual-coagulant facilitated Ti hydrolysis and promoted the clustering, cross-linking, formed Ti-AOM/NOM-Fe complexes. Under the adsorption bridging and adsorption electro-neutralization of TS-CTS and in-situ Fe(III), the microflocs were formed, migrated, adhered and ultimately retained in filter layer media. This study can provide guidance for technological and agent selection in algae-laden surface water treatment.
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