Protecting biodiversity with the dragonfly zone a nature-based solution proposed by SUEZ

The Dragonfly Zone (Zone Libellule®) is an environmental innovation site inspired by natural wetlands. Its goal is to act as a buffer space downstream from wastewater treatment plants, where treated wastewater continues to be purified by a series of ecological processes that work naturally in wetlands, with the bonus of protecting local biodiversity.
Our innovation

Encouraging rich, dense biodiversity while treating micropollutants

Arising from unique engineering developed by SUEZ, the Dragonfly Zone complements the conventional treatment provided by wastewater plants with the purification capacity of nature. It is an artificial wetland that can be established downstream from a wastewater treatment plant, in which the development of biodiversity intensifies the fight against micropollutants and limits their spread in freshwater or seawater.

The Dragonfly Zone consists of a series of basins of varying shapes and sizes, planted with local species selected specifically for each project (reeds, irises, water mint, sage, rushes, water lilies etc.). The treated wastewater circulating through these basins is purified by a combination of biological actions (biodegradation by microfauna, removal by plants) and physical effects (degradation by the sun, settling). The succession of varying wetland environments, with different flow speeds and depths of water, mobilises these different mechanisms for pollutant degradation or absorption, adapting the treatment to each site's objectives.

Five years of research led by CIRSEE, our main centre of research and expertise, as part of the ZHART project (2012-2016), led to the Dragonfly Zone concept being finalised. Its scale can be adapted to the treatment goals for the macro- and micropollutants being targeted and to the local context.

Unlike other planted discharge zones, the Dragonfly Zone is able to meet quantified targets for water regulation, micropollutant treatment and ecological benefit.  

Our references

Full-scale applications

The Dragonfly Zone concept has been deployed at several sites in France and exported to China. In 2017, SUEZ NWS won a design contract for the ecological rehabilitation of wetlands at Shanghai Chemical Industry Park (SCIP). It is the Group’s largest wetland creation project, using the Dragonfly Zone concept and covering approximately 40 hectares.

The aim of the project is to rehabilitate the existing wetland to improve industrial wastewater treatment using a network of functional and natural wetlands. To meet the challenge of treating the SCIP industry park’s salinated wastewater, coastal plant species with a high salinity tolerance were chosen for the wetland. This ecological engineering innovation helps to improve the quality of treated wastewater and boost the site’s high level of biodiversity.