活性污泥胞外聚合物的组成与结构特点及环境行为

在活性污泥处理系统中,微生物大多以污泥絮体的形式悬浮在水中。胞外聚合物(EPS)作为污泥絮体的重要组成部分,以其独特的聚合结构和化学组成,在污水生物处理系统中起到重要作用。为了更好的描述EPS的环境行为,文章综合了近年来国内外相关的研究成果,首先分析了EPS的来源、化学组成及结构分布,得出EPS中包含蛋白质、多糖、腐殖酸、核酸、糖醛酸及脂类大分子等化学物质,其中蛋白质和多糖之和占总有机物含量的70%~80%;在结构上,EPS分为SB-EPS、LB-EPS和TB-EPS,三者与细胞结合的紧密程度递增,其中所含化学成分比例的不同将使其具有不同的理化特性。其次,文章对EPS的理化特征对污水处理系统的影响,如对系统中微生物降解特性的影响、磷和重金属的吸附等进行了讨论,并总结了EPS中相关的官能团对上述环境行为的贡献。同时,文章还论述了EPS中官能团的亲疏水特性及化学成分对污泥絮体的脱水性、絮凝沉降性能的影响。

Chemical Structure and Environmental Behavior of Extracellular Polymeric Substances in Sludge: A Review

In the traditional activated sludge process, most of the microorganisms are existing as suspended flocs in the units of wastewater treatment plants. Extracellular polymeric substance (EPS), as a significant component in sludge flocs, plays a very important role in the sewage biological system for its unique polymeric structure and chemical composition. With the aim at describing the environmental behavior of EPS in a better way, on the basis of summarization of the typical results of various literatures, the origin, chemical composition and structure distribution of EPS is analyzed firstly. It is found out that protein, polysaccharide, humic acid, nucleic acid, uronic acid, lipids and other chemical substances are the main components of EPS, with protein and polysaccharide accounting for 70~80% of the total organic content. In the terms of structure, EPS are divided into SB-EPS, LB-EPS and TB-EPS. These three fractions are binding tightly with the cells and their various chemical compositions lead to different physical and chemical properties of EPS. Furthermore, the effects of the above characteristics of EPS on the sewage disposal process such as microbial degradability, phosphorus adsorption and heavy metals removal are discussed. Then, contribution of relative functional groups of EPS to the above environmental behaviors is summarized. Meanwhile, the effects of hydrophobic/hydrophilic features and chemical compositions of the functional groups of EPS on the dewaterbility and flocculation of sludge flocs are also illustrated.