硫酸盐还原菌活性污泥胞外聚合物对环丙沙星的吸附机制

胞外聚合物(extracellular polymeric substances,EPS)是微生物污泥的重要组成部分,在废水生物处理过程中起着至关重要的作用.通过上流式硫酸盐还原反应器(sulfate-reducing up-flow sludge bed,SRUSB)的连续运行和批次实验评价了硫酸盐还原菌(sulfate-reducing bacteria,SRB)活性污泥对环丙沙星(ciprofloxacin,CIP)的去除以及EPS在CIP去除过程中所起的重要作用.结果表明,SRB污泥可通过吸附和生物降解有效去除CIP,其中吸附是主要去除途径,EPS在吸附过程中起到重要作用.采用三维荧光光谱结合平行因子分析探究了SRB活性污泥的EPS与CIP结合的机制;采用傅里叶红外光谱分析鉴定了EPS中参与CIP结合的主要官能团.EPS主要通过静态猝灭与CIP结合形成EPS-CIP复合物,其中色氨酸和酪氨酸类蛋白质是EPS中主要参与CIP结合的物质,结合常数分别为1.43×104L·mol~(-1)和1.02×104L·mol~(-1);红外分析表明,羟基、氨基和羧基是EPS中主要参与CIP结合的基团.实验结果揭示了SRB污泥的EPS与CIP结合的机制,有助于更好地理解EPS在SRB污泥系统去除CIP,以及其他有机微污染物的过程中所起的重要作用.

Adsorption Mechanisms of Ciprofloxacin by Extracellular Polymeric Substances of Sulfate-reducing Bacteria Sludge

Extracellular polymeric substances (EPS) in microbial sludge, fulfils a key role in removal of micro-organic pollutants during biological wastewater treatment. In this study, the authors evaluated the removal of ciprofloxacin (CIP) by sulfate-reducing bacteria (SRB) sludge in a sulfate-reducing up-flow sludge bed (SRUSB) reactor, and examined the role of EPS on CIP removal in an SRB sludge system. The results indicated that CIP was removed efficiently through adsorption and biodegradation by SRB sludge, with adsorption the major removal pathway. EPS also played an important role in CIP adsorption by SRB sludge, and the adsorption mechanisms of CIP by EPS were investigated using the three-dimensional excitation-emission matrix fluorescence spectroscopy technologies combined with parallel factor analysis. The functional groups binding CIP onto EPS were identified through Fourier transform infrared (FTIR) spectra analysis. The results suggested that the static quenching of EPS following CIP adsorption led to formation of an EPS-CIP complex, and that the CIP was mainly bound with tryptophan and tyrosine-like protein substances in EPS with the binding constants of 1.43×10⁴ L·mol^-1 and 1.02×10⁴ L·mol^-1, respectively. The FTIR results suggested that hydroxyl, amino and carboxyl functional groups were mainly responsible for binding of CIP onto EPS. The results revealed the adsorption mechanisms of CIP by EPS in SRB sludge, and enhanced understanding of the role of EPS in sulfur-mediated biological processes for the removal of CIP and other organic micro-pollutants.