Wastewater is water that has been contaminated by domestic and/or industrial use. It can be divided into two types:

• domestic wastewater, including:

  • household water (resulting from its use for personal hygiene, laundry, dishwashing, and floor cleaning),

  • toilet water (water used to flush toilets and consequently contaminated with feces and urine);

• non-domestic wastewater (runoff from rainwater, industrial sources, etc.).

Wastewater contains a range of physical, chemical, and biological contaminants of human, environmental, and/or industrial origin related to the activities and uses of a group of people and/or establishments.

In the case of public sewer systems, wastewater is conveyed via sewers (combined or separate, depending on whether stormwater is conveyed together with wastewater) to a wastewater treatment plant, where it is treated before being discharged into the environment.

Understanding the circulation of SARS-CoV-2 in the population through wastewater surveillance

In the context of the COVID-19 pandemic, surveillance of the SARS-CoV-2 virus in wastewater through the detection of its RNA began at the start of the pandemic on an exploratory basis in France and in many other countries. Indeed, several initiatives and research projects emerged in France as early as 2020 in both the public and private sectors. Thus, in April 2020, the Epidemiological Wastewater Observatory (OBEPINE), a consortium of research teams, was established. Other entities are also very active in this field, including those in the public sector (research teams, departmental fire and rescue services) and the private sector.

This surveillance complements other health monitoring systems already in place. It enables the detection and tracking of disease spread within a population and can be conducted independently of existing testing strategies. The primary benefit is the ability to detect early warning signs, such as the presence of the SARS-CoV-2 genome and emerging variants.

With this in mind, on March 17, 2021, the European Commission issued a recommendation urging Member States to adopt a common approach to establishing surveillance for the presence of SARS-CoV-2 and its variants in wastewater.

Strong mobilization of health agencies and partners

In this context, a national wastewater surveillance system is being implemented under the leadership of the ministries responsible for health and the environment, with health agencies mobilized:

• The Nancy Hydrology Laboratory of the French Agency for Food, Environmental and Occupational Health & Safety (ANSES) has been designated as the national reference laboratory for monitoring SARS-CoV-2 in wastewater and sewage sludge, primarily to ensure the quality of analyses.

• Santé publique France, the national public health agency responsible for monitoring COVID-19, is specifically tasked with producing and interpreting indicators related to the detection of the SARS-CoV-2 genome in wastewater for public health and management support purposes.

To this end, a surveillance protocol was developed in 2021 to:

• define the objectives of wastewater surveillance from a public health perspective,

• define a sampling strategy based on the objectives and phases of the epidemic,

• make recommendations on the interpretation of wastewater surveillance indicators, combined with other available health data sources.

It is based on experiments conducted in France and other countries, as well as recommendations from the WHO, the U.S. CDC (Centers for Disease Control and Prevention), the Netherlands, and the European Commission (EU 2021/472 of March 17, 2021).

Given its contribution to the establishment of the national system for virological surveillance of SARS-CoV-2 in wastewater, Santé publique France will be notably involved in the national steering committee and in the standardization of analytical methods (Afnor process).