Abstract: Extracellular polymeric substances（EPS） are a class of complex high-molecular-weight mixture of polymers，which have special form and structure，and are excreted by microorganisms. They are commonly found in microbial aggregates，and are critical substances for the formation and structural stability of bio-aggregates. They have serious impact on the sludge performance，and play an important role in the stable operation of biological wastewater treatment system. The composition，structural characteristics，biodegradability and absorption characteristics of EPS are reviewed in this paper. Especially，the influence of EPS’s composition with extracellular protein（PN），extracellular polysaccharide（PS），and structural characteristics with tightly bound EPS（TB-EPS） and loosely bound EPS（LB-EPS） are summarized for the microbial aggregates. It is concluded that appropriately raising the content of the PN and PS has contributed to the microbial aggregates flocculation，but excessive PS would be likely to have negative effects on the sludge sedimentation and dewatering. The article also analyzes the influence mechanism，i.e.，the reason why PN and PS can effectively promote the sludge flocculation could be due to the influence of surface electro-negativity，high hydrophobicity of the PN，the biological gel properties，and adsorption bridging by PS.

Key words: waste water, extracellular polymeric substances, biotechnology, biofilm, granulation

摘要： 胞外多聚物（extracellular polymeric substances，EPS）是一类具有特殊形态和结构的高分子化合物。EPS普遍存在于生物聚集体内，是生物聚集体形成与稳定的关键性物质，对废水生物处理系统的稳定运行具有重要作用。文章归纳总结了EPS的组分、结构特性、可生物降解性及其吸附特性等方面的研究成果；重点从EPS的主要组成物质胞外蛋白（extracellular protein，PN）和胞外多糖（extracellular polysaccharide，PS）以及结构特性中紧密附着型EPS（tightly bound EPS，TB-EPS）和松散附着型EPS（loosely bound EPS，LB-EPS）的研究出发，论述了EPS对生物聚集体的影响，适当升高PN和PS的含量有助于污泥絮凝，然而过多的PS含量将可能对污泥的沉降与脱水性能起负面影响。文章还分析了其影响机理，PN和PS能够有效促进污泥絮凝可能是由于PN表面电负性和高疏水性的影响以及PS的生物凝胶特性和吸附架桥作用。

关键词: 废水, 胞外多聚物, 生物技术, 生物膜, 造粒