Variations in dissolved organic matter and analysis of membrane fouling in densadeg-ultrafiltration-based advanced treatment process
This study investigates the composition and variation of Dissolved Organic Matter(DOM)during the advanced treatment process of municipal wastewater,employing various technologies including Ultraviolet-Visible Spectroscopy(UV-Vis),Three-Dimensional Excitation-Emission Matrix(3D-EEM),Fluorescence Regional Integration(FRI),Size Exclusion Chromatography(SEC),Fourier Transform Infrared Spectroscopy(FT-IR),and Scanning Electron Microscopy(SEM).The findings of this study revealed that the advanced treatment process effectively eliminated various organic substances.Specifically,the concentrations of Dissolved Organic Carbon(DOC)in the effluent from the secondary sedimentation tank,high-density sedimentation tank,and ultrafiltration process were measured at 7.43 mg/L,5.98 mg/L,and 3.32 mg/L,respectively.Notably,the ultrafiltration process achieved a remarkable DOC removal rate of 44.5％.Furthermore,the advanced treatment process exhibited significant reductions in the peak fluorescence intensity of organic protein components and humic substances in the secondary effluent.The distinctive peaks associated with the hydroxyl group(—OH)found in polysaccharides,the amide group(—CO—NH—)present in proteins,and the carboxyl group(—COOH)present in humic substances were detected on the surface of the fouled membrane.Proteins and polysaccharides present in the effluent from the high-density sedimentation tank were identified as the primary culprits responsible for membrane fouling,persisting on the membrane surface even after multiple filtration and backwashing cycles.The results revealed that the organic matter mass on the membrane surface was predominantly protein(1.04 mg),polysaccharide(0.32 mg)and humic(0.07 mg)in descending order.This study utilized simulated wastewater to investigate the membrane fouling mechanism caused by typical dissolved organic foulants from the high-density sedimentation tank effluent.The findings indicated that the membrane-specific flux of the simulated wastewater containing polysaccharides and proteins decreased by 71％and 72％at the onset of the second and third cycles,respectively,compared to the initial cycle.The study proposes that the membrane fouling mechanism during the advanced treatment process is strongly linked to Dissolved Organic Matter(DOM).The synergistic effect of polysaccharides and proteins may contribute to more pronounced membrane fouling,as it leads to the formation of a thick and dense cake layer.
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