An assessment of the river’s quality revealed that the Ostwaldergraben was of poor quality (low level of biodiversity, presence of hydrocarbons, metals, pesticides, etc.) In view of European regulatory requirements (the 2000 Framework Directive on Water), the CUS has undertaken a programme to restore and improve the physical and chemical qualities of its watercourses, and thereby recover the biodiversity of their flora and fauna.
The principal stages in the restoration of the Ostwaldergraben in the urban environment :
- Creation of an ecological corridor to restore biodiversity, in particular the green toad (a second phase is still to come),
- Design and completion of three processes for depolluting pure rainwater before discharge into the Ostwaldergraben (underway).
Each clean-up process comprises :
- an artificial sedimentation pond;
- a vertical or horizontal flow filter planted with reeds;
- a natural pond that receives the treated water.
Exemplary features of the plan that has been implemented
The techniques proposed for treatment of pure rainwater in the urban environment are the result of a partnership between several agencies and cross-disciplinary environmental research.
Exemplary features of the technical solutions implemented
The technical solutions applied are low-tech, of reasonable cost for installation and monitoring, are well integrated into the landscape and will be of long-term ecological benefit to the ecosystem.
List of skills that can be seen on the site
- Expertise in monitoring the design and production of clean-up technology,
- Metrological expertise enabling the clean-up technology to be fitted with instruments enabling both qualitative and quantitative monitoring of seasonal fluctuation in pollution flows.
- Analytical skills that make it possible to describe the behaviour of constructed wetlands.
Key funding figures
Overall finance provided by: the CUS, ENGEES, AERM, ZAEU
- Work (restoration and clean-up devices): €320,000
- Instrumentation and metrology: €110,000
- Analytical monitoring: €50,000
- Follow-up engineering (doctoral thesis, teacher-researcher time): €450,000
1 Quai Koch, 67000 Strasbourg
Players involved and their roles
COMMUNAUTE URBAINE DE STRASBOURG (CUS)
SINBIO: Bureau d’études
ECOLE NATIONALE DU GENIE DE L'EAU ET DE L'ENVIRONNEMENT DE STRASBOURG (ENGEES), LABORATOIRE EN SCIENCES DE L'INGENIEUR, DE L'INFORMATIQUE ET DE L'IMAGERIE (ICUBE), AGENCE DE L'EAU RHIN MEUSE (AERM) , ASSOCIATION POUR L'ETUDE ET LA PROTECTION DES AMPHIBIENS ET REPTILES D'ALSACE (BUFO), ZONE ATELIER ENVIRONNEMENTALE URBAINE (ZAEU)