Wastewater is primarily of domestic origin, but a certain percentage of it may be of industrial origin, according to the local industry. In view of its composition (presence of pathogenic microorganisms and/or chemicals that are a risk for human health), this water is collected and treated before it is discharged into the natural environment. In most cases this waste is collected, transported to and treated in sewage plants (mains sewage); in a smaller number of situations the discharge is treated in individual sewage systems.
ANSES’s expert appraisal work covers three areas:
- supporting the authorities in order to assess the risks for sensitive uses (swimming, shellfish farming) located downstream of sewage discharges;
- assessing projects for the construction of sewage plants or the discharges originating from them;
- assessing the effectiveness of non-mains wastewater treatment systems.
Sensitive activities downstream of sewage discharges
Activities such as swimming, shellfish farmingor the production of drinking water are particularly sensitive to the quality of surface water and may be indirectly affected by discharges associated with sewage. These discharges may originate from non-mains sewage systems or from a collection network and wastewater treatment plant.
The quality of treated wastewater discharged by these plants depends on the performance of the treatment systems used. In addition, the wastewater collection network and/or treatment plants may suffer malfunctions resulting in the discharge of untreated or only partially-treated wastewater that contaminates the environment (particularly when there is heavy rainfall).
In this context the Agency, in support of the authorities, is responsible for assessing the risks for sensitive uses located downstream of these discharges as well as monitoring and inspection plans if applicable.
Opinions on projects to build sewage plants or on the discharges originating from them
The French Public Health Code (Article R.1331-1 of the French Public Health Code) stipulates that “The Prefect may formally request ANSES to assess any sewage project”. These projects include creations, works, and discharges from wastewater treatment plants. Most of these projects are investigated locally and the Prefect rarely requests the Agency’s expert assessment.
As this concerns the reuse of treated wastewater, and pending the amendment of the Decree of 2 August 2010 relating to the “use of water originating from the purification treatment of urban waste water for the irrigation of crops or green spaces”, further to the Agency’s recommendations in its 2012 report on the reuse of treated wastewater by sprinkling (see “sustainable water” section), applications for authorisation to reuse treated wastewater by sprinkling may also be submitted to the Agency.
Assessment of the effectiveness of non-mains sewage systems
In 2009 the Agency issued an expert appraisal report concerning the technical assessment protocol for non-mains sewage plants. Since then, the Agency has participated in a national discussion group concerned with methodologies for on-site monitoring of these plants.