School of Environment, Nanjing Normal University, Nanjing, 210023, China.
College of Environment and Resources, Fuzhou University, Fujian, 350116, China.
Chemosphere. 2021 Jul;274:129798. doi: 10.1016/j.chemosphere.2021.129798. Epub 2021 Jan 27.
The extracellular polymeric substances (EPS) of activated sludge are a mixture of high molecular weight polymers secreted by microorganisms, which are mainly composed of proteins, polysaccharides and humic substances. It is widely accepted that EPS have a good adsorption ability for pollutants with different functional groups. However, recent studies showed the EPS had an inhibitory effect on pollutant sorption, which is contradictory to previous viewpoint. Therefore, in this study, three types of activated sludge with different EPS contents and compositions were used to investigate the role of EPS in an antibiotic-trimethoprim (TMP) sorption process at environmentally relevant concentration. The in situ experiments results showed the adsorption capacity of activated sludge for TMP were increased from 2.98, 5.37 and 28.33 μg/g VSS to 7.87, 12.93 and 150.24 μg/g VSS in nitrifying activated sludge, wastewater treatment plant activated sludge and anaerobic ammonia-oxidized activated sludge, respectively after EPS extracted. The adsorption process can be well described by the pseudo-second-order kinetic model. Results of zeta potential, contact angles and infrared spectrum showed TMP replacing proteins embedded into the cell membrane enhancing the TMP adsorption capacity of activated sludge after EPS extraction. Our results demonstrated that less proteins in EPS of activated sludge is more beneficial for TMP adsorption removal.
胞外聚合物（EPS）是微生物分泌的高分子聚合物混合物，主要由蛋白质、多糖和腐殖质组成。人们普遍认为 EPS 对具有不同官能团的污染物具有良好的吸附能力。然而，最近的研究表明 EPS 对污染物的吸附具有抑制作用，这与之前的观点相矛盾。因此，本研究使用三种具有不同 EPS 含量和组成的活性污泥，在环境相关浓度下研究 EPS 在抗生素甲氧苄啶（TMP）吸附过程中的作用。原位实验结果表明，EPS 提取后，硝化活性污泥、污水处理厂活性污泥和厌氧氨氧化活性污泥对 TMP 的吸附容量分别从 2.98、5.37 和 28.33μg/g VSS 增加到 7.87、12.93 和 150.24μg/g VSS。吸附过程可用准二级动力学模型很好地描述。zeta 电位、接触角和红外光谱的结果表明，EPS 中的蛋白质减少后，TMP 取代嵌入细胞膜的蛋白质，从而提高了活性污泥对 TMP 的吸附能力。我们的结果表明，活性污泥 EPS 中的蛋白质越少，越有利于 TMP 的吸附去除。
