活性污泥胞外多聚物提取方法的比较

活性污泥污水处理系统中胞外多聚物(extracellular polymeric substances,EPS)对污染物的去除及污泥的絮凝、沉降和脱水性能都有着重要作用,影响活性污泥工艺的运行稳定性,然而不同的提取方法可能导致EPS组分、数量有显著差异,直接影响相关实验结果.本文采用离心法提取溶解型和疏松型EPS后,采用文献经常报道的8种物理、化学方法提取紧密型EPS(tightly bound EPS,TB-EPS),研究TB-EPS数量及多糖、蛋白质、核酸等成分含量并进一步分析TB-EPS的基团组成,也分析了TB-EPS中15种元素含量.结果表明,8种方法中,加热法提取TB-EPS组分数量较多,对污泥微生物细胞破坏程度低,且在EPS提取过程不引入外源物质,是一种较为合适的EPS提取方法.阳离子树脂法对TB-EPS中芳香族蛋白质和腐殖酸类物质有较好的提取效果,Na OH法对富里酸类物质提取效果较好.物理法对TB-EPS红外光谱的官能团种类无明显影响,但化学法对TB-EPS官能团种类影响较显著,TB-EPS具有不同的特征吸附峰.总体上,化学法提取的TB-EPS中元素含量高于物理法.研究者应根据实验目的,选取适宜的EPS提取方法;或者建立EPS提取的标准方法,有助于实验结果间的比较.

Comparison of Extraction Methods of Extracellular Polymeric Substances from Activated Sludge

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.