活性污泥胞外聚合物(EPS)的分层组分及其理化性质的变化特征研究

Study on the Stratification Components of Extracellular Polymeric Substances (EPS) in Activated Sludge and Their Variation Characteristics in Physicochemical Properties

针对活性污泥的胞外聚合物(EPS),采用阳离子交换树脂(CER)法和离心/超声波法对总EPS和分层EPS(由外至内依次为slime,LB-EPS,TB-EPS)分别进行提取,测定EPS中多糖(PS)、蛋白质(PN)和DNA的含量,并对各EPS溶液的理化特性随溶液条件的变化特征进行了探讨.结果表明,EPS的化学组分(PS、PN和DNA)在TB-EPS层中含量最高,其亲水性组分的含量高于疏水性组分,但PN的疏水比高于PS.各层EPS中PS/PN的值对其Zeta电位和等电点有重要的影响.其中,PS/PN越高,各层EPS的Zeta电位越小,分层EPS的等电点越高.各种EPS溶液pH的增加导致其Zeta电位基本呈下降趋势,对应的等电点分别为pH总EPS=2.9、pHslime=2.2、pHLB-EPS=2.3、pHTB-EPS=1.3.离子强度的增加可以导致EPS溶液的电导率呈直线上升,对应的Zeta电位却迅速增加然后趋于稳定,但并未出现电位逆转现象.此外,升高温度(<40℃)可以降低各种EPS溶液的表观黏度,并在40～60℃之间时逐渐趋于稳定.

To study extracellular polymeric substances（EPS） in activated sludge,EPS were extracted by cation exchange resin（CER） method as the total EPS,and stratified through centrifugation and ultrasound into three fractions： slime,LB-EPS and TB-EPS from the outside to the inside.The contents of proteins（PN）,polysaccharides（PS） and DNA were determined separately.Furthermore,their variation characteristics in physicochemical properties along with the solution conditions were also investigated.Results showed that the maximum contents of PN,PS and DNA were found in the TB-EPS fraction.The hydrophilic components of the total EPS and its fractions had a higher concentration than the hydrophobic components,and PN showed a higher hydrophobicity than PS.The PS/PN ratio had a great influence on Zeta potentials and isoelectric point values of EPS.That is to say,the greater PS/PN ratio of EPS was,the smaller Zeta potentials for the total EPS or its fractions and the higher isoelectric point values for EPS fractions were.All Zeta potentials of EPS solutions presented a general decrease trend with increasing pH.The corresponding isoelectric point values were 2.9 for the total EPS,2.2 for the slime,2.3 for the LB-EPS and 1.3 for the TB-EPS,respectively.The increase in ionic strength resulted in the tendency of straight climb with the increase in the conductivity of EPS solutions,while the corresponding Zeta potentials tended to reach stable negative values after a rapid increase.In addition,when temperature went up（40℃）,the apparent viscosity of EPS solutions decreased,then gradually kept unchanged in the range from 40℃ to 60℃.