高密沉淀-超滤深度处理过程有机物变化及膜污染分析

Variations in dissolved organic matter and analysis of membrane fouling in densadeg-ultrafiltration-based advanced treatment process

超滤技术被广泛应用于城镇污水深度处理,但膜污染导致的通量衰减问题始终是制约超滤处理效率的主要瓶颈之一。研究利用生化池、二沉池、高密池和超滤出水探究了城镇污水深度处理过程中溶解性有机物(Dissolved Organic Matter,DOM)的组成和变化,采用紫外光谱、荧光光谱、傅里叶变换红外光谱等多种技术手段对高密沉淀-超滤组合工艺的超滤膜污染进行化学结构、污染物组成分析研究。结果显示,深度处理可去除多种有机物,二沉池出水、高密池出水、超滤出水的溶解性有机碳(Dissolved Organic Carbon,DOC)质量浓度分别为7.43 mg/L、5.98 mg/L、3.32 mg/L,超滤对DOC截留率达44.5%。此外,深度处理工艺可以显著降低二级出水中蛋白质组分和腐殖质的荧光强度。在模拟废水条件下,探究了高密池出水典型污染物的膜污染机制。高密池出水中的蛋白质和多糖是造成膜污染的主要物质,在经过多批次过滤、反洗试验后依然残留于膜表面,其中残留质量由大到小依次为蛋白质(1.04 mg)、多糖(0.32 mg)、腐殖酸(0.07 mg)。研究表明,深度处理过程的膜污染机制与DOM密切相关,多糖与蛋白协同作用可导致更为严重的膜污染并形成致密且不易脱落的滤饼层,含多糖和蛋白质的模拟废水在第二和第三周期开始时的膜比通量比第一周期开始时分别降低了71%和72%。

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.