School of Environmental Studies, China University of Geosciences, Wuhan 430074, PR China; Hubei Key Laboratory of Environmental Water Science in the Yangtze River Basin, China University of Geosciences, Wuhan 430074, PR China.
School of Environmental Studies, China University of Geosciences, Wuhan 430074, PR China.
Water Res. 2024 Jan 1;248:120845. doi: 10.1016/j.watres.2023.120845. Epub 2023 Nov 8.
Several studies on COVID-19 pandemic have shown that the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) originating from human stool are detected in raw sewage for several days, leading to potential health risks for workers due to the production of bioaerosols and droplets during wastewater treatment process. In this study, data of SARS-CoV-2 concentrations in wastewater were gathered from literatures, and a quantitative microbial risk assessment with Monte Carlo simulation was used to estimate the daily probability of infection risk through exposure to viable infectious viral airborne particles of the workers during four seasons and under six environmental conditions. Inhalation of bioaerosols and direct ingestion of wastewater droplets were selected as exposure pathways. Spearman rank correlation coefficients were used for sensitivity analysis to identify the variables with the greatest influence on the infection risk probability. It was found that the daily probability of infection risk decreased with temperature (T) and relative humidity (RH) increase. The probability of direct droplet ingestion exposure pathway was higher than that of the bioaerosol inhalation pathway. The sensitivity analysis indicated that the most sensitive variable for both exposure pathways was the concentration of SARS-CoV-2 in stool. So, appropriate aeration systems, covering facilities, and effective ventilation are suggested to implement in wastewater treatment plants (WWTPs) to reduce emission concentration. Further to this, the exposure time (t) had a larger variance contribution than T and RH for the bioaerosol inhalation pathway. Implementing measures such as adding more work shifts, mandating personal protective equipment for all workers, and implementing coverage for treatment processes can significantly reduce the risk of infection among workers at WWTPs. These measures are particularly effective during environmental conditions with low temperatures and humidity levels.
几项关于 COVID-19 大流行的研究表明，在污水中可检测到源自人类粪便的严重急性呼吸综合征冠状病毒 2（SARS-CoV-2），在废水处理过程中，由于生物气溶胶和液滴的产生，这对工人造成了潜在的健康风险。在这项研究中，从文献中收集了污水中 SARS-CoV-2 浓度的数据，并使用带有蒙特卡罗模拟的定量微生物风险评估来估计工人在四个季节和六种环境条件下通过暴露于空气中具有传染性的活病毒颗粒而感染的风险的日概率。吸入生物气溶胶和直接摄入污水飞沫被选为暴露途径。使用 Spearman 秩相关系数进行敏感性分析，以确定对感染风险概率影响最大的变量。结果发现，感染风险的日概率随温度（T）和相对湿度（RH）的升高而降低。直接飞沫摄入暴露途径的概率高于生物气溶胶吸入途径。敏感性分析表明，对于两种暴露途径，最敏感的变量是粪便中 SARS-CoV-2 的浓度。因此，建议在废水处理厂（WWTP）中实施适当的曝气系统、覆盖设施和有效的通风系统，以降低排放浓度。此外，对于生物气溶胶吸入途径，暴露时间（t）比 T 和 RH 的方差贡献更大。增加更多班次、为所有工人强制佩戴个人防护设备以及对处理过程进行覆盖等措施，可以显著降低 WWTP 工人的感染风险。这些措施在温度和湿度水平较低的环境条件下特别有效。
