Ecological engineering: a double win for Irstea

Recognized as one of the "strategic pillars of the green economy" by the Ministry of Ecology, sustainable development and energy, ecological engineering is proving increasingly more attractive, and action and awareness raising plans are on the rise. Proof of this is that following on from the 2nd National Ecological Engineering Days which took place in June, the National Grand Prize for "Ecological Engineering to Address Water Policy Challenges" has now been created to reward exemplary actors and projects in this field. The award ceremony, which took place during the convention of the Scientific and Technical Association for Water and the Environment (ASTEE), also took a look back over 50 years of water legislation : a chance to highlight the contribution of the ecological sector to the preservation of aquatic environments. During this inaugural award ceremony, Irstea was awarded 2 prizes in recognition of its strong involvement in this expanding field. Here is a close-up of the 2 award-winning projects.

Pond innovation

Rampillon Pool © M-L. Degaudez / IrsteaThe pilot project for an artificial wetland buffer zone in Rampillon [1] in Seine-et-Marne was recognized in the category of "Ecological Engineering in the Fight Against Diffuse Agricultural Pollution". In other words it constitutes a solution to naturally clean up agricultural waters, by using ingenious purification basins created by the researchers.

Nearly one million people from the Île-de-France region are supplied with drinking water from the Champigny groundwater system. The water that drains into the water table is sometimes heavily loaded with pesticides and nitrates. In order to intercept this pollution, Irstea and the AQUI'Brie Association established an artificial wetland buffer zone (Zone tampon humide artificielle, ZHTA) of over one hectare in 2012 in order to purify the water.

Perfectly integrated into the landscape, the artificial wetland buffer zone is nevertheless the result of a complex design that captures and slows water from fields and redirects it towards the basins. There, the combined actions of sun, bacteria (present in the environment) and plants naturally degrade the pesticides and nitrates. To create this system, 4 facilities have been put in place:

  • improvements to an existing pool in order to exploit its purification function
  • two artificial wetland buffer zones of 2,000m2 built on the land of two farmers located upstream of the catchment area
  • and a 1.4 ha buffer zone built to treat all the water in the basin

To complete the system, researchers have developed an original hydraulic management system that rationalizes the arrival of the pollutant flow, by opening and closing valves during pesticide application periods. This allows the concentrations of pollutants to disperse in the ZHTA installed downstream, thereby limiting their transfer from agricultural plots to the water table. And it works ! Out of 100 pesticides analyzed, the results showed a 50 % average reduction in concentration, and a 20 mg/L reduction in nitrates, with high seasonal variability. For researchers, however, this by no means constitutes a "license to pollute" ! These facilities must be coupled with measures to reduce the use of pesticides and nitrates upstream.

New natural purification stations for overseas departments (DOM)

Aerial view of the Mansarde-Rancée station in Martinique © SICSMThe use of plant filtration is a well-known and proven technique. It has been around for more than 50 years and takes its inspiration from the natural purifying capacity of wetland ecosystems. But how does this technique stand up in a tropical environment ? The treatment techniques used in mainland France cannot be directly transferred as they are to overseas departments (DOM). This is a challenge that researchers from the Irstea center in Lyon-Villeurbanne, alongside the Water Board of Martinique and the French National Agency for Water and Aquatic Environments (ONEMA), have addressed through the ATTENTIVE project [2], a winner in the category for "Ecological Engineering Towards Alternative Management of Rain and Wastewater."

Limited access to materials, strong population growth, a fragile financial situation and a unique climate context have all served to hamper the development of sewage treatment infrastructure. This is a crucial issue when 80 % of national biodiversity is found in the DOM, which account for 14 % of the national territory !

The ATTENTIVE project combines the wastewater, solid matter and mud generated by treatment in one system with vertical flow, and produces "compost" that can be used in agriculture, all thanks to the use of macrophyte plant filters [3].Use of local plants, such as false papyrus © P. Molle / Irstea

After initial tests carried out in Mayotte in 2006, Irstea researchers, alongside the company COTRAM, were able to adapt the design : 2 plant filtration stations designed for 1,000 and 1,500 people were established by using local non-invasive plants and local materials that are resistant to variations in rainfall. A true showcase of ecological engineering, these 2 experimental sites unique within Europe have been a success: related expansion projects for the whole of the region are already emerging ! A green light for ecological engineering !

Definition / Ecological engineering

Inspired by nature and living things, ecologists, Irstea biologists and hydrologists restore and create new ecosystems for biodiversity and improve the quality of our everyday lives by limiting our impact on the environment.

For more information

[1] Project carried out in collaboration with the association AQUI’Brie and with the support of the Seine-Normandy Water Agency and the Seine-et-Marne department.

[2] ATTENTIVE: Wastewater purification adapted to a tropical context through extensive plant-based treatment. Project created in response to a call for projects in 2011 by the Ministry of Ecology, Sustainable Development and Energy within the framework of the National Biodiversity Strategy (SNB). Project led by the Martinique Water Office and funded by ONEMA.

[3] Macrophyte is a generic term for all aquatic plants that are visible to the naked eye (reeds, water lilies, etc.).