基于粒度分布的活性污泥胞外聚合物提取及凝聚特性分析

Extraction and functional analysis of extracellular polymeric substances based on granulometric distribution of activated sludge

胞外聚合物(EPS)在活性污泥的凝聚及结构方面起着重要的作用。现有研究一般根据分离难易程度及空间分布,将EPS分为溶解型EPS(SEPS),松散结合型EPS(LB-EPS)和紧密结合型EPS(TB-EPS)。本研究提出了根据EPS功能进行分类的概念,将EPS分为絮体EPS(extra-microcolony polymeric substances,EMPS)和菌胶团EPS(extra-cellular polymeric substances,ECPS)。以活性污泥粒度分布的演变为基础,采用阳离子交换树脂法作为一次提取法,甲醛加碱法和超声-高速离心法2种方法分别作为二次提取法,对EMPS和ECPS进行分离提取,并对其功能及凝聚特性进行分析。结果显示,阳离子交换树脂法可有效提取EMPS,而超声-高速离心法可有效提取ECPS。ECPS比EMPS含有更多的蛋白质和多糖,且ECPS比EMPS具有更强的疏水性。此外,EMPS和ECPS都表现出较强的带负电特性。结果表明,活性污泥絮体层级和菌胶团层级的聚合力不同,絮体层级的絮凝主要由二价阳离子的桥联作用引起,而菌胶团层级的凝聚则是由疏水作用等其他作用力引起。

Extracellular polymeric substances( EPS) play a crucial role in the formation and structure of activated sludge. According to the degree of separation and spatial distribution,EPS can be divided into soluble EPS( SEPS),loosely bound EPS( LB-EPS) and tightly bound EPS( TB-EPS) in existing study. This research puts forward the concept of classified according to the function of EPS,EPS can be divided into floc EPS( extramicrocolony polymeric substances,EMPS) and microcolony EPS( extra-cellular polymeric substances,ECPS).Based on the granulometric distribution evaluation of activated sludge,using the cation exchange resin( CER)method as the step 1 extraction method,and using the formaldehyde-alkaline method and ultrasonication-high speed centrifugation method as the step 2 extraction to separate the EMPS and ECPS and analyze the function.The results show that cation exchange resin treatment is efficient to extract the EMPS,however,ultrasonicationhigh speed centrifugation method is efficient to extract the ECPS. The protein and polysaccharides of ECPS was higher than that of EMPS. The contents of hydrophobic substances in ECPS were also higher than that of EMPS.Moreover,both types of EPS were found to be much negatively charged. It turned out that there are different aggregation forces of floc level and microcolony level of activated sludge. Divalent cation bridging interactions are more crucial in floc level flocculation,while the hydrophobic interactions are more important in microcolony level cohesion.