【作者】 李永红；

【导师】 张晓健；

【作者基本信息】 清华大学 ， 土木工程， 2011， 博士

【摘要】 本论文针对微污染地表水源水中的粘土颗粒和有机物，在实验室条件下通过分析超滤过程中膜比通量的变化，并结合有机物分子量分布、树脂分级、扫描电镜（SEM）、能谱分析（EDS）、傅立叶红外光谱（FTIR）、三维荧光光谱（FEEM）等测试方法，分别研究了其对浸没式超滤膜的膜污染特性，并考察了混凝、粉末活性炭（PAC）吸附、混凝－PAC预处理工艺对其造成的各种膜污染（总膜污染、可逆膜污染、不可逆膜污染）特性的影响。有机物造成的膜污染过程包括膜比通量的快速下降、短期过渡、平稳下降以及反冲洗后上升四个阶段，主要属于不可逆膜污染。直接超滤处理含有机物的原水时，膜比通量的下降速率与原水有机物的浓度成指数关系，符合y=0.0157e0.0588x。有机物在过滤初期对超滤膜造成的膜孔窄化和孔内吸附堵塞，是导致其产生不可逆膜污染的主要原因。有机物造成的不可逆膜污染随过滤的进程呈线性增长。粘土颗粒造成的膜污染主要属于可逆膜污染。直接超滤处理含粘土颗粒的原水时，膜比通量的下降速率与原水浊度成线性关系。提高反冲洗的频率可以减轻可逆膜污染。试验用浸没式中空纤维超滤膜能耐受混合液的浊度在40000NTU以下。粘土颗粒的存在增加了有机物造成的总膜污染，降低了其不可逆膜污染。粘土颗粒和有机物共存时形成的滤饼层，增加了膜表层过滤微孔的开孔率，减小了膜孔内部吸附的有机物，从而降低了有机物造成的不可逆膜污染。混凝预处理有效降低了有机物产生的不可逆膜污染和总膜污染。选择合理的混凝停留时间、混凝剂投加量、曝气强度、反洗周期等运行参数，采用连续投加混凝剂的方式，均可以有效降低有机物产生的不可逆膜污染。投加粉末活性炭降低了有机物产生的不可逆膜污染，但会增加其总膜污染。采用一次投加PAC方式优于连续投加方式，更适宜于工程应用。联合使用混凝和PAC预处理工艺时，其对不可逆膜污染减轻的效果小于二者单独对不可逆膜污染减轻效果之和，并不是二者效果的简单叠加。投加混凝剂和PAC改善了膜表面的污染层结构，降低了有机物在过滤初期造成的膜孔窄化程度，这是降低其不可逆膜污染的关键。文中还对不可逆膜污染的定期化学清洗，进行了碱洗、酸洗条件的对比研究。以上研究成果对于深入了解超滤膜污染特性及其控制机理有重要参考价值。更多还原

【Abstract】 This paper was mainly conducted in laboratorary to study the characteristics ofimmersed ultrafiltration (UF) membrane fouling caused by clay particle and organicmatter in source water and investigate the influence of pretreatment, such as coagulation,adsorption of powdered activated carbon (PAC), coagulation-PAC on different type ofmembrane fouling (including total membrane fouling, reversible membrane fouling andirreversible membrane fouling). Based on the experimental filtration study, a morecomprehensive understanding of membrane fouling and the control mechnism wereobtained by the analysis of the molecular weight (MW) distributions of organic, XADresin fractionation, and scanning electron microscope (SEM), X-ray energy dispersivespectra (EDS), fourier transform infrared spectroscopy (FTIR) and fluorescenceexcitation-emission matrix (FEEM).The membrane fouling caused by organic matter is mainly irreversible. It includesfour courses of the membrane specific flux as quickly decline, the short-term steady,the smooth decline and increase after the backwash. The decline rate of membranespecific flux has an exponential relationship with TOC of source water in ultrafiltrationof organic matter: y=0.0157e0.0588x. The irreversible fouling caused by organic matteris mainly due to the narrowed membrane pore at the beginning of the filtration. Theirreversible fouling increased lineally with filtration time in the study.The membrane fouling caused by clay particle is mainly reversible due to cakelayer formation on the membrane surface. Experimental results demonstrate positivecorrelation between the turbidity of source water and the decrease rate of membranespecific flux. The predominant resistance was the cake resistance, which could beminimized by increasing the frequency of backwashing. The immersed hollow fiber UFmembrane could endure the mixture in membrane tank with turbidity below40000NTU. The existence of clay particle in the HA solution was found to be able to mitigatethe irreversible fouling caused by organic matter. However, the total membrane foulingby organic matter was increased. The SEM imagines demonstrated that cake layerformed by clay particle could prevent organics into the membrane pore hole andincreased the porosity of membrane surface, which greatly decreased irreversiblefouling. Coagulation pretreatment effectively decreased the total membrane fouling and theirreversible membrane fouling caused by organic matter. The irreversible membranefouling by organic matter was decreased by selecting appropriate operation parameters,such as coagulation retention time, dosage of coagulant, aeration strength, backwashingperiod and continuous dosing of coagulant.PAC pretreatment decreased the irreversible membrane fouling and increased thetotal membrane fouling caused by organic matter. Batch dosing of PAC was better andmore suitable for engineering application over continuous dosing. The combined effectof coagulant and PAC on irreversible membrane fouling was not the simple addition ofthe individual’s effect, but less than the sum of the individual’s effect. Addition ofcoagulant and PAC improved the structure of fouling layer on the membrane surface,declined the degree of membrane pore narrowed by organic matter at the early stage ofultrafiltration, which is the key reason to mitigate the irreversible membrane fouling byorganic matter.Regular chemical cleaning for removal of irreversible membrane fouling was alsoinvestigated with sodium hydroxide, hydrochloric acid and citric acid in this paper.The research results above would provide any insight into the characteristics ofimmersed ultrafiltration membrane fouling and the control mechanism in dringkingwater treatment.更多还原