关键词: 废水, 胞外多聚物, 生物技术, 生物膜, 造粒

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