分层型水源水库溶解性有机物性质及其膜污染特性

利用激发-发射矩阵(EEM)荧光光谱和紫外吸收光谱研究了深水型水源水库热分层期溶解性有机物(DOM)性质及其膜污染特性随水深的变化.结果表明,水体热分层导致DOM质量浓度和性质也表现出分层特征.变温层受光化学降解影响较大,DOM质量浓度较低,同时受藻类等浮游植物分泌的内源有机物影响,DOM芳香度较低,类富里酸有机物(C1组分)和类腐殖酸有机物(C2组分)荧光强度较低,但类色氨酸有机物(C3组分)荧光强度较高;斜温层DOM受径流输入影响较大,DOM质量浓度和芳香度较高,C1和C2组分荧光强度较高.膜污染方面,变温层DOM造成的总污染最大,但可逆性较好,斜温层和等温层DOM造成的总污染较低,但可逆性较差;对超滤过程中不同荧光组分迁移的分析表明,超滤膜对C3组分截留率较高,但反冲洗对被截留的C3组分去除效果较好,而被膜截留的C1和C2组分较难被反冲洗去除.

Characteristics and Fouling Potential of Dissolved Organic Matter in a Stratified Source Water Reservoir

Quantity and quality of dissolved organic matter (DOM) in source water are critical factors affecting both the drinking water quality and operation of the water treatment process. As major water sources for many cities, deep reservoirs usually suffer seasonal thermal stratification, which has a significant influence on the fate and transport of many contaminants including iron, manganese, ammonia and DOM. This study focuses on the variation of properties and the fouling potential of DOM in a deep-source water reservoir during the thermal stratification period. Excitation-emission matrix (EEM) fluorescence spectra and ultraviolet absorption spectra were used to characterize the DOM. The results indicate that the quantity and quality of DOM vary with the water depth due to thermal stratification. The DOC of epilimnion is lower than that of the metalimnion and hypolimnion due to photochemical degradation. Moreover, organic matter released by phytoplankton, such as algae, play an important role in the DOM composition. Therefore, the DOM of the epilimnion exhibits a lower aromaticity, lower fluorescence intensities of Component 1 (i.e., fulvic-like substance) and Component 2 (i.e., humic-like substance), and higher fluorescence intensity of Component 3 (i.e., tryptophan-like substance). The DOM of the metalimnion is dominated by runoff input and therefore the concentration, aromaticity, and fluorescence intensities of Components 1 and 2 are higher. In terms of membrane fouling, total fouling caused by the DOM of the epilimnion is the largest, but its reversibility is better. The DOM of the metalimnion and hypolimnion results in lower total fouling but poor reversibility. The analysis of the fate of different fluorescence components during ultrafiltration suggests that the UF shows a relative high rejection rate for Component 3, which could be readily removed by backwash, whereas Component 1 and Component 2 retained by the membrane are difficult to be removed by backwash.