城市污水厂活性污泥中胞外聚合物与工艺运行及污泥沉降性能的相关性分析

胞外聚合物(Extracellular polymeric substance,EPS)的组分及含量是影响活性污泥性能的重要因素之一.本研究在测定不同城市污水处理厂活性污泥中EPS的基础上,分析水质情况与运行条件对EPS组分的影响.结果表明:蛋白质为EPS的主要组分,约占25%~63%;腐殖酸次之,占21%~50%;DNA和多糖的含量较少.同是A~2O工艺的2个污水厂的污泥沉降性能和粒径分布差异较大.根据Pearson分析结果,在污泥微膨胀和正常状态下,EPS总量与污泥体积指数(Sludge Volume Index,SVI)及粒径分布没有明显的相关性,但腐殖酸和DNA均与SVI呈正相关.处理工艺的水力停留时间与EPS总量负相关,但污水中有机物含量对EPS的含量及组分没有影响.EPS中多糖含量与脱氮除磷过程显著相关,多糖可以作为脱氮除磷过程的有机碳源.污泥龄影响EPS中蛋白质与多糖的比值.因此,污水水质、工艺类型及运行条件不同程度的影响EPS的组分及含量,进而影响处理效果.

Correlation of extracellular polymeric substance (EPS) in Activated sludge of municipal wastewater treatment plants to process performance and sludge settleability

Extracellular polymeric substance (EPS) is a key factor affecting the property of activated sludge. In this study, the components of EPS in activated sludge of municipal wastewater treatment plants (WWTPs) were quantified, and the correlations of EPS components to wastewater characteristics and operational conditions were analyzed. Results indicated that protein was the main constituent accounting for 25%~63%, followed by humic acid with 21%~50%. DNA and polysaccharide were the least. Sludge settleability and particle size distribution was obviously different in two wastewater treatment plants even though the same process (A²O) was applied. According to the Pearson analysis, there is no correlation between EPS content and sludge volume index (SVI) or particle size distribution under normal and limited filamentous bulking conditions. Yet the content of DNA and humic acid both positively correlated with SVI. The hydraulic retention time (HRT) of the process negatively correlates with EPS content, but the content of organic matters in wastewater had no effect on EPS and components. The content of polysaccharide significantly correlated with biological nutrients removal, which could be used as carbon sources for biological nutrients removal. Sludge retention time (SRT) affected the ratio of protein to polysaccharide. Therefore, wastewater characteristics, process types and operational conditions affected the components and content of EPS and further affected the performance of WWTPs.