Abstract：
The increase in effluent discharge from wastewater treatment plants (WWTPs) into urban rivers has raised concerns about the potential effects on pathogen risks. This study utilized metagenomic sequencing combined with flow cytometry to analyze pathogen concentrations and antibiotic resistance in a typical effluent-receiving river. Quantitative microbial risk assessment (QMRA) was employed to assess the microbial risks of pathogens. The results indicated obvious spatial-temporal differences (i.e., summer vs. winter and effluent vs. river) in microbial composition. Microcystis emerged as a crucial species contributing to these variations. Pathogen concentrations were found to be higher in the river than in the effluent, with the winter exhibiting higher concentrations compared to the summer. The effluent discharge slightly increased the pathogen concentrations in the river in summer but dramatically reduced them in winter. The combined effects of cyanobacterial bloom and high temperature were considered key factors suppressing pathogen concentrations in summer. Moreover, the prevalence of antibiotic resistance of pathogens in the river was inferior to that in the effluent, with higher levels in winter than in summer. Three high-concentration pathogens (Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa) were selected for QMRA. The results showed that the risks of pathogens exceeded the recommended threshold value. Escherichia coli posed the highest risks. And the fishing scenario posed significantly higher risks than the walking scenario. Importantly, the effluent discharge helped reduce the microbial risks in the receiving river in winter. The study contributes to the management and decision-making regarding microbial risks in the effluent-receiving river.
摘要：
从污水处理厂（WWTP）排放到城市河流的废水增加，引起了人们对病原体风险的潜在影响的担忧。这项研究利用宏基因组测序结合流式细胞术分析了典型的污水接收河流中的病原体浓度和抗生素抗性。采用定量微生物风险评估（QMRA）评估病原体的微生物风险。结果表明明显的时空差异(即，夏天vs.冬季和污水vs.河流)在微生物组成中。微囊藻是导致这些变异的关键物种。发现河流中的病原体浓度高于废水中的病原体浓度，与夏季相比，冬季表现出更高的浓度。污水排放在夏季略微增加了河流中的病原体浓度，但在冬季却大大降低了病原体浓度。蓝藻水华和高温的综合作用被认为是抑制夏季病原体浓度的关键因素。此外，河流中病原体对抗生素的耐药性低于废水中的耐药性，冬季比夏季高。三种高浓度病原体（大肠杆菌，肺炎克雷伯菌,和铜绿假单胞菌）被选择用于QMRA。结果表明，病原体的风险超过了建议的阈值。大肠杆菌构成最高的风险。而钓鱼场景的风险明显高于步行场景。重要的是,污水排放有助于减少冬季接收河流中的微生物风险。该研究有助于有关污水接收河流中微生物风险的管理和决策。
