胞外聚合物(EPS)是活性污泥的重要成分,其含量和组成对污泥的宏观物理性质有重要影响。在这项研究中,使用XAD树脂分馏系统研究了污泥中EPS对温度(-40-200°C)的响应,变温红外光谱(VTIS)和二维相关光谱(2D-COS)。还建立了EPS的分子结构与不同温度下废物活性污泥(WAS)的宏观物理性质(流变性能和脱水性能)之间的关系。在冷冻处理期间,生物聚合物的溶解和亲水官能团的破坏(羟基,氨基和羧基)导致产生小的有机物,增强了EPS的疏水性,减少了污泥的静电排斥,以及随后的脱水性能改善。对于水热处理,EPS转化显示两阶段反应,包括阶段I(70-120°C)和阶段II(>120°C)。第一阶段(70-120°C),大量的亲水官能团(羟基,通过生物聚合物的溶解暴露EPS中的氨基和羧基),增强了污泥的静电斥力和EPS的亲水性,以及污泥脱水性和流动性恶化的后果。然而,在阶段II(>120°C),高温导致大分子有机物完全水解,其中蛋白质的二级结构被破坏,导致肽链展开。此外,α-螺旋和β-折叠含量的降低和美拉德反应的加剧降低了污泥的静电斥力,从而提高了污泥的脱水性能和流动性。该研究丰富了基于温度调节的污泥处理优化控制的理论基础。
Extracellular polymeric substances (EPS) are important components of activated sludge, whose content and composition have important effects on the macro-physical properties of sludge. In this study, the response of EPS in sludge to temperature (-40-200 °C) was systematically investigated using XAD resin fractionation, variable-temperature infrared spectra (VTIS) and two-dimensional correlation spectroscopy (2D-COS). The relationships between the molecular structure of EPS and the macro-physical properties (rheological property and dewatering performance) of waste activated sludge (WAS) at varying temperature were also established. During the freezing treatment, the solubilization of biopolymers and destruction of the hydrophilic functional groups (hydroxy, amino and carboxyl) resulted in the production of small organic matters, which enhanced EPS hydrophobicity and reduced electrostatic repulsion of sludge, and subsequent dewaterability improvement. For the hydrothermal treatment, the EPS transformation showed a two-stages reaction including stage I (70-120 °C) and stage II (>120 °C). Stage I (70-120 °C), a plenty of hydrophilic functional groups (hydroxy, amino and carboxyl) in EPS were exposed via the solubilization of biopolymers, which enhanced electrostatic repulsion of sludge and EPS hydrophilicity, and subsequence in deterioration of sludge dewaterability and fluidity. However, at stage II (>120 °C), the high temperature caused hydrolyzation of macromolecular organic matters in completely, in which the secondary structure of the protein was destroyed, causing the peptide chain to unfold. In addition, the reduction of α-helix and β-sheet content and intensified Maillard reaction decreased electrostatic repulsion of sludge, thus resulted in the improvement of sludge dewaterability and fluidity. This study enriched the theoretical basis of the optimal control of sludge treatment based on temperature regulation.