SARS-CoV-2 virus in wastewater

T. G. Masaryk Water Research Institute together with the Research Institute of Veterinary Medicine in Brno, and with epidemiologists from the 1st Faculty of Medicine, Charles University, introduced a wastewater monitoring system in order to monitor the epidemic situation of the Covid-19 disease and predict its development. Monitoring is financed by the project VI04000017 "Use of wastewater monitoring as an early warning tool against the emergence of the epidemiological situation" programme 4. VS BV III. by institutional resources of the Ministry of the Environment through an internal TGM WRI grant 3600.52.33/2020. Sampling is performed by WWTP operators. The particular methodology was newly approved by the Ministry of Health of the Czech Republic.

What exactly do we monitor?

The principle of the system is the collection of untreated wastewater at selected wastewater treatment plants (WWTPs) suitable for the purpose, isolation of viral RNA, and quantitative detection of the number of the SARS-CoV-2 virus genomic units. Viral RNA is secreted into the wastewater by SARS-CoV-2 infected persons and therefore its amount correlates with their numbers in the areas connected to the monitored WWTPs. The results of the analyses show the good usability of the chosen method and thus the possibility of obtaining valuable objective epidemiological information at a disproportionately lower cost than with the help of clinical trials.

Where do we monitor?

The research team is currently performing continuous monitoring at four WWTPs in the Czech Republic and is analysing and evaluating the results of analyses of more than 550 samples taken at 66 WWTPs throughout the Czech Republic during all waves of the epidemic, and it is ready to offer cooperation to the healthcare sector for successful implementation of the European Commission recommendation on the introduction of systematic monitoring of SARS-CoV-2 in wastewater dated 17 March 2021. T.G. Masaryk Water Research Institute, p.r.i. ensures, independently or in cooperation with WWTP operators, wastewater sampling and, together with the Research Institute of Veterinary Medicine, p.r.i. in Brno, performs isolation and quantitative detection of SARS-CoV-2 RNA from wastewater in three laboratories.

What were the first results and what did they show?

The obtained results confirmed that the system is able to detect the onset of a new wave of the epidemic before it is proven by clinical tests. Ongoing regular monitoring of SARS-CoV-2 virus RNA in wastewater in 4 cities of the Czech Republic (Prague, Brno, Kladno, and Břeclav) at 5 WWTPs (Prague WWTP – the existing and the new water line, Brno WWTP, Vrapice-Kladno WWTP, and Břeclav WWTP) is a unique tool that allows capturing the current state of the occurrence of the coronavirus in the Czech Republic and the expected onset of the next epidemic wave. Wastewater monitoring is thus a functioning objective tool for monitoring the development of the virus in the population, which does not require testing of individuals.

And what the fresh results show (updated to Aug 3, 2022)?

The current state of monitoring the objective occurrence of the coronavirus in the Czech Republic, carried out using wastewater analysis, shows that the SARS-CoV-2 coronavirus is still present in the Czech Republic. We can currently observe a sharp increase in SARS-CoV-2 values ​​(to the level of values ​​that were observed in the spring of this year or in the fall of last year), which indicates another wave of covid-19 disease in the Czech Republic.

Brno WWTP – the content of virus particles in wastewater has reliably captured all waves of the epidemic to date. Data from the end of April and the beginning of May showed a decrease in the level of viral load in wastewater, accompanied by a gradual decrease in the number of people tested positive. The oscillating level of waste water load in May 2022 corresponds to approximately the number of people excreting viruses into waste water in autumn 2021. The end of May saw a decrease in the level of waste water load to between the detection method. During June, a gradual increase in the amount of viral RNA in the wastewater is recorded. In July, the amount of viral RNA continued to increase at the Brno WWTP. The latest figure from 26/07/2022 showed a decrease. Additional data will show whether this is a standard deviation or a downward trend.

Břeclav WWTP – the waste water from this WWTP caught all the previous waves of the epidemic. Data from May 2022 showed a decrease in the amount of viral particles in the wastewater – the level of viral RNA in the wastewater corresponded to the autumn values. At the end of May, the wastewater load decreased to between the detection method. During June, a gradual increase in the amount of viral RNA in the wastewater was recorded. As at the Brno WWTP, the amount of viral RNA continued to increase at the Břeclav WWTP in July. The latest figure from 26/07/2022 showed a decrease. Additional data will show whether this is a standard deviation or a downward trend.

Prague WWTP – on both the existing and the new water line, wastewater monitoring captured all waves of the epidemic very well. The level of viral RNA in wastewater in April and May 2022 corresponded to the values ​​found in autumn 2021. In June, as in other monitored WWTPs, an increase in the amount of viral RNA was detected. In the 28th week (July), there was a significant increase in the amount of viral RNA in the wastewater on both lines of the WWTP. The increase in the number of positive tests was only moderate.

Kladno WWTP – wastewater monitoring captured all waves of the epidemic very well. The level of viral RNA in wastewater in April and May 2022 corresponded to the values ​​found in autumn 2021. In June, compared to the previous period, an increased amount of viral RNA was detected in wastewater.

The results of wastewater monitoring in the above graphs are compared with the verified numbers of positively tested persons, from the ISIN system, continuously processed by the Department of Biostatistics of the SZÚ for specific monitored locations. Data on weekly numbers of positively tested individuals in the Czech Republic are obtained from the publicly accessible website of the European Center for Disease Prevention and Control. For the possibility of comparing current wastewater monitoring results (approx. for the last 1-2 months), freely available data from covid maps or publicly accessible websites for individual cities on the platform https://obce.nery.cz/ (in Czech) are used. Public data may contain errors and do not contain the number of inhabitants in the connected municipalities.

Fluctuations in the capture of RNA sought in wastewater can be caused by:

  • different amount of wastewater = different dilution of the amount of viral RNA fragments present,
  • by taking in another weekly regime (weekend),
  • inhomogeneity of the collected sample (waste water contains a number of other substances and particles, sampling is performed after mechanical removal of coarse impurities),
  • the volatile ratio of industrial and municipal wastewater.

You can learn more about the issue of coronavirus in surface and wastewater, and the possibilities of using the results as a diagnostic medium, in the articles of the VTEI journal here (in Czech) and here (in Czech). A Czech television (in Czech) report from Kateřina Sovová and an article in MF Dnes (in Czech) public journal from Hana Zvěřinová Mlejnková also deal with the topic.

Learn more about the ongoing project here.