摘要

      大型污水处理厂每年向地表水排放数百吨固体悬浮物。此外，在大雨期间，如果采用合流制下水道系统，则会有类似数量的下水道溢流到地表水中。随着沉积作用的进行，颗粒附着的微生物及其耐药基因（ARGs）被输送到受纳河流的河床中。为了更好地了解这一动力学过程，在间歇式反应器中加入了一部分颗粒废水，该反应器之前充满了天然河流沉积物和自来水。同时，使用抗生素（ABs）（红霉素、四环素、环丙沙星、罗红霉素、青霉素V和磺胺甲恶唑）来研究它们的耐药性选择能力。通过定量PCR技术对水体和沉积物中6种ARGs（ermB、tetM、blaTEM、sul1、CTX-M-32和qnrS）和细菌总数（16s rDNA）进行了连续两个月的监测。尽管持续暴露于ABs（每个5μg/L）中，ARGs的丰度仍然没有受到影响。废水颗粒物的加入导致水体（3-5个对数单位）和沉积物（1-4个对数单位）中的ARGs突然而强烈地增加，然而升高的ARGs经历了一个特殊而完全的衰减过程。结果表明，受纳河流中ARG含量的增加是污水处理厂排放或下水道溢流事件中ARG持续输入的结果。这些结果进一步说明如果去除ARG的持续输入，接受河流中ARG的升高将不复存在。这似乎只适用于在废水中引入的ARG，因为在本地人群中观察到了稳定的ARG背景浓度。

      Large-scale wastewater treatment plants (WWTPs) discharge hundreds of tons of total suspended solids (TSS) into surface waters every year. Additionally, a comparable amount is released by sewer overflows during heavy rain events in case of combined sewer systems. Along with sedimentation, particle-attached microorganisms and their antibiotic resistance genes (ARGs) are herewith transported to the riverbed of the receiving water. To better understand the dynamics of this process, a particulate wastewater fraction was added into batch reactors, which were previously filled with natural river sediments and tap water. In parallel, antibiotics (ABs) (erythromycin, tetracycline, ciprofloxacin, roxithromycin, penicillin V, and sulfamethoxazole) were spiked to investigate their capability to select for resistance. The abundance of six ARGs (ermB, tetM, bla_TEM, sul1, CTX-M-32, and qnrS) as well as total bacteria (16S rDNA) was monitored in waters and in sediments for a duration of two months using quantitative PCR. Despite a continuous exposure to ABs (5 μg/L each), the abundance of ARGs remained unaffected. Addition of wastewater particles resulted in a sudden and strong increase of ARGs in waters (3–5 log units) and sediments (1–4 log units), however, elevated ARGs underwent a particular and complete decay. Our results indicate that the increased ARG abundances in receiving rivers are the result of a continuous import of ARGs from WWTP discharges or sewer overflow events. They further imply that elevated ARGs do not persist in receiving rivers, if this continuous import is removed. This seems to be the case merely for ARGs introduced by wastewater, given that a stable background concentration of ARGs was observed for the native population.

      https://www.sciencedirect.com/science/article/pii/S0048969719358565