Protecting citizens from epidemics by analysing wastewater
In response to the Covid-19 pandemic, SUEZ is offering a solution to screen wastewater networks for SARS-CoV-2 viral markers. The innovative system combines analysis of SARS-Cov-2 markers in sewer systems with a digital platform.
Local authorities can use this vital public health protection tool to track circulation of the virus in their areas, and thereby anticipate and adjust the necessary health measures at a district level.
A decision-making tool to help fight the pandemic
In their discussions with public health authorities, local authorities need reliable epidemiological data to track circulation of the virus, anticipate the potential outbreak of new clusters and introduce appropriate health measures for their local inhabitants.
Covid-19 City Watch is an effective monitoring system that tracks the spread of the virus in a city and anticipates potential outbreaks of new clusters within the population.
It is based on scientific research that has shown that the viral load present in wastewater is a relevant and early marker (two to five days) of its circulation in the population. The system warns of the emergence of new clusters as soon as the contamination phase begins, before symptoms start to appear.
Xavier Litrico, Group Chief Research & Science Officer at SUEZ, speaks about Covid-19 City Watch
Provided with these early indicators of change in the circulation of the virus within a given area, local public and health authorities are able to:
Monitor high-risk or critical facilities (care homes, hospitals and clinics, and buildings with a high occupancy rate);
Implement early preventive measures (screening tests, awareness campaigns for protective measures such as face coverings, etc.);
Limit access to certain sensitive facilities.
A flexible solution for epidemic outbreaks
By adopting a strategy for wastewater sampling and analysis that is adapted to the epidemic situation, local authorities can access optimal data for monitoring circulation of the virus in the population.
SUEZ offers a flexible solution that can adapt to changing circumstances:
A foundation with moderate surveillance, comprising a research element, which helps define the sampling strategy for different levels of surveillance, sampling and analysis at wastewater treatment plants and key sensitive sites for a set period decided in consultation with the local authority. The results of the analysis are viewed on a special platform and SUEZ provides a guide to interpreting the data.
Depending on how the epidemic evolves, optional modules can be added to this foundation. Strong or maximum surveillance modules have higher and more widespread sampling and analysis rates.
The following steps provide vital elements for local authorities and public health bodies to make the right decisions:
Collection of sewer system data, to identify and map impact zones, for example high wastewater output, river basins, etc.
Identification of sensitive areas: care homes and community health centres, schools, buildings with a high occupancy rate, recreational areas, etc.
Sectorisation of the sewer system: network data is used to compartmentalise districts and sub-districts to help locate potential clusters.
Sampling: automatic samplers take samples continuously over 24 hours to provide an average daily count.
Samples are taken every week to ensure reliable results.
Sample analysis: SUEZ laboratories analyse the samples using a protocol developed in conjunction with the OBEPINE network which involves identifying and quantifying the genetic markers of the SARS-CoV-2 virus responsible for COVID-19. Wastewater samples are first pre-concentrated then the RT-qPCR (Reverse Transcription quantitative Polymerase Chain Reaction) technique is used to detect and quantify SARS-CoV-2 RNA. At the same time, a special RT-qPCR analysis of F-specific RNA bacteriophages is also carried out to avoid a dry/rainy weather variation bias in municipal wastewater.
Visualisation of results on a dynamic map and data interpretation.
Outside of an epidemic, the appearance of a high concentration at a point in the network can signify the formation of a cluster. In this case, surveillance points can be increased to identify the epidemic cluster.
Generally speaking, trend analysis can identify areas in which the epidemic risk is either increasing or decreasing.
Health experts at SUEZ provide help in interpreting the data.
Modular levels of surveillance
Absence of an epidemic signal and/or presence of a “background” indicator: MODERATE surveillance through sampling:
- at wastewater treatment plant inflow
- at sensitive sites (care homes, community health centres, schools, etc.)
Detection of a growing quantity of viral markers at wastewater treatment plant inflow or at sensitive sites: switch to MAXIMUM surveillance
- Increase in number of samples
- Sampling of district collectors
- Focus on the infected district(s)
Stabilisation or decrease in the concentration of viral markers in wastewater: switch to HIGH surveillance
- Reduction in number of samples
- Stop focus on the infected district(s)
- Continue sampling of district collectors
End of epidemic: switch to MODERATE surveillance
- Reduction in number of samples
- Stop sampling of district collectors
The number and location of sample points for each option are decided in consultation with local authority services during the sectorisation study.
The options are decided in consultation with the local authority, depending on how the epidemic evolves.