Lyon

Location: Lyon Metropole

Context:3rd biggest metropolis in France with ~1.4 million inhabitants

Climate:Lyon is classified to have a semi-continental climate zone, but climate change has shifted it closer to a Mediterranean climate change effect, therefore experiencing heat waves, more intense and frequent storms, especially in summer.

Typology:Stormwater /CSO French Vertical Flow Constructed Wetland with a forced aeration system

Description: In the region of Lyon metropolis, the more intense and frequent storms are leading to increasing problems with conventional treatment plants to handle rain water quantity overflows. Thanks to the pilot in Lyon, we are demonstrating the performance of this kind of typologies to help mitigate stormwater and CSO while treating a wide range of pollutants.

The pilot is based on the hidr'epur solution. This entails encorporating Forced Aeration abd also, to implement reactive materials. It is obviously functioning for both storm water run-off and CSO. Filtration happens through 3 main layers:

• Filtering layer (composed by unsaturated gravel)
• Transiton layer (saturated and composed by medium sized gravel)
• Drainage layer

enhancing the removal of pollutants and sediments.

The ongoing monitoring of a wide range of pollutants screened the removal performance, considering different aeration techniques and the use of saturated and unsaturated layers. For upscaling, design needs to be adapted for contextual needs (topography, inflow, land-use patterns, etc). Upscaling this system through a decentralised approach at Lyon metropolitan region is being discussed through stakeholder exchanges.

In addition to treating real storm water and Combined Sewage Overflow, it helps to improve the natural nearby area where the receiving water body is located, enhancing the quality of this recreational site for many citizens.

Synergies: System co-designed between INRAE research centre and the private design company EcoBird. More information about the French vertical flow Treatment Wetlands systems, to be consulted at our UrbanByNature NICE Capacity-Building webinar series. In these series, Introduction, theoretical concepts and research results, recommendations on design, construction and maintenance of the systems, based on practical case examples.

The research done in the Lyon 'Urban Real Lab' will be utilised to implement the solution in other site locations, as INRAE moves forward with stakeholder engagement for decentralising the current wastewater treatment systems in the Metropolitan area of Lyon.