Sun Xiu-Yue, Tang Zhu, Yang Xin-Ping
Department of Environmental Science and Engineering, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China.
Huan Jing Ke Xue. 2018 Jul 8;39(7):3306-3313. doi: 10.13227/j.hjkx.201711034.
Extracellular polymeric substances (EPSs) are biosynthetic polymers of microbial origin in the sludge activation process and crucially affect the properties of sludge in biological wastewater treatment reactors, such as the formation of sludge flocs, stabilization of sludge structure, and protection of microbes against noxious environmental conditions. However, the EPS extraction efficiency differs significantly according to the extraction method used. In this study, soluble EPSs and loosely bound EPSs can be extracted by centrifugation first and tightly bound EPSs in activated sludge require additional eight treatments for extraction, respectively. Three physical methods (centrifugation, sonication, and heating) and five chemical methods (cation exchange resin, NaOH, formaldehyde+NaOH, EDTA, and formaldehyde+EDTA) were tested, and the content and composition of TB-EPS were analyzed. Meanwhile, the functional groups and elements in TB-EPS were investigated. Results showed that the heating method did not introduce exogenous substances during the EPS extraction process and that the destruction of cells from this method was relatively slight. Heating was shown to be a gentle and efficient method in this study. The three-dimensional excitation and emission matrix (EEM) fluorescence spectroscopy showed that the cation exchange resin method had good extraction effect on humic-like and protein-like substances. As to fulvic-acid-like substances, NaOH was better than the other seven methods. Infrared spectroscopy showed that no notable difference appeared in the functional groups of the TB-EPS extracted by physical methods, whereas chemical methods induced big differences and showed particular bands that did not appear in the TB-EPS extracted by physical methods. Overall, the amounts of TB-EPS elements extracted using chemical methods were greater than those extracted using physical methods. In conclusion, a method must be selected and established for each case, taking into consideration the experimental purpose, and the most appropriate method should be chosen carefully.
胞外聚合物（EPSs）是污泥活化过程中微生物来源的生物合成聚合物，对生物废水处理反应器中污泥的性质有至关重要的影响，例如污泥絮体的形成、污泥结构的稳定以及微生物免受有害环境条件的影响。然而，EPS的提取效率根据所使用的提取方法有显著差异。在本研究中，可溶性EPS和松散结合的EPS可先通过离心提取，而活性污泥中紧密结合的EPS分别需要额外的八种处理方法进行提取。测试了三种物理方法（离心、超声和加热）和五种化学方法（阳离子交换树脂、NaOH、甲醛+NaOH、EDTA和甲醛+EDTA），并分析了紧密结合EPS（TB-EPS）的含量和组成。同时，对TB-EPS中的官能团和元素进行了研究。结果表明，加热法在EPS提取过程中未引入外源物质，且该方法对细胞的破坏相对较小。在本研究中，加热被证明是一种温和且高效的方法。三维激发发射矩阵（EEM）荧光光谱表明，阳离子交换树脂法对类腐殖质和类蛋白质物质具有良好的提取效果。对于类富里酸物质，NaOH比其他七种方法更好。红外光谱表明，物理方法提取的TB-EPS的官能团没有明显差异，而化学方法则引起了很大差异，并显示出在物理方法提取的TB-EPS中未出现的特定谱带。总体而言，化学方法提取的TB-EPS元素含量大于物理方法提取的含量。总之，必须根据实验目的为每种情况选择并建立一种方法，并应谨慎选择最合适的方法。
