Laboratory of Environmental Engineering & Planning, Department of Civil Engineering, Aristotle University of Thessaloniki, Thessaloniki 54 124, Greece.
Department of Genetics, Development and Molecular Biology, School of Biology, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece.
Sci Total Environ. 2021 Feb 10;755(Pt 1):142855. doi: 10.1016/j.scitotenv.2020.142855. Epub 2020 Oct 12.
Detection of SARS-CoV-2 in sewage has been employed by several researchers as an alternative early warning indicator of virus spreading in communities, covering both symptomatic and asymptomatic cases. A factor that can seriously mislead the quantitative measurement of viral copies in sewage is the adsorption of virus fragments onto the highly porous solids suspended in wastewater, making them inaccessible. This depends not only on the available amount of suspended solids, but also on the amount of other dissolved chemicals which may influence the capacity of adsorption. On this account, the present work develops a mathematical framework, at various degrees of spatial complexity, of a physicochemical model that rationalizes the quantitative measurements of total virus fragments in sewage as regards the adsorption of virus onto suspended solids and the effect of dissolved chemicals on it. The city of Thessaloniki in Greece is employed as a convenient case study to determine the values of model variables. The present data indicate the ratio of the specific absorption (UV/DOC) over the dissolved oxygen (DO) as the parameter with the highest correlation with viral copies. This implies a strong effect on viral inaccessibility in sewage caused (i) by the presence of humic-like substances and (ii) by virus decay due to oxidation and metabolic activity of bacteria. The present results suggest days where many fold corrections in the measurement of viral copies should be applied. As a result, although the detected RNA load in June 2020 is similar to that in April 2020, virus shedding in the city is about 5 times lower in June than in April, in line with the very low SARS-CoV-2 incidence and hospital admissions for COVID-19 in Thessaloniki in June.
已经有几位研究人员将污水中的 SARS-CoV-2 检测作为一种替代方法，用于早期预警病毒在社区中的传播，包括有症状和无症状病例。一个可能严重误导污水中病毒拷贝定量测量的因素是病毒片段吸附到废水中高度多孔的悬浮固体上，使其无法被检测到。这不仅取决于悬浮固体的可用量，还取决于可能影响吸附能力的其他溶解化学物质的数量。有鉴于此，本工作提出了一个数学框架，涵盖不同空间复杂度的物理化学模型，该模型使定量测量污水中的总病毒片段合理化，涉及病毒对悬浮固体的吸附以及溶解化学物质对其的影响。希腊塞萨洛尼基市被用作方便的案例研究，以确定模型变量的值。目前的数据表明，特定吸收率（UV/DOC）与溶解氧（DO）的比值与病毒拷贝数具有最高的相关性。这意味着在污水中对病毒不可达性有很强的影响，原因是（i）腐殖质样物质的存在，以及（ii）由于细菌的氧化和代谢活性导致病毒衰减。本结果表明，在测量病毒拷贝数时应进行多倍修正。因此，尽管 2020 年 6 月检测到的 RNA 负荷与 2020 年 4 月相似，但与塞萨洛尼基市 6 月 SARS-CoV-2 发病率和 COVID-19 住院人数非常低一致，该市 6 月的病毒排放比 4 月低约 5 倍。
