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The second half of the last century witnessed the implementation of increasingly strict environmental policies. In terms of wastewater treatment, these policies have resulted in more stringent discharge standards, particularly for nitrogen and phosphorus. The objective still relevant today was to improve the quality of water bodies and rivers threatened by eutrophication.

This improvement is reflected in the restoration of biodiversity, as seen with the reappearance in rivers such as the Seine or the Thames of fish species that had been extinct from them. Therefore, the sewerage network and wastewater treatment plant are considered as a whole system that must minimise its impact on the environment.

The new step already well underway of this development is to transform wastewater treatment plants into biorefineries that can reuse 100% of the wastewater they treat and recover 100%

of treatment process by-products: biowaste-to-energy, sludge to compost, and even phosphorous extraction. This is already the case in Granada, Spain, and Santiago, Chile. A frame of reference on circularity must not only consider the specificities of these water uses but also their interaction with the other issues at stake, all of which are connected to biodiversity: diet, economic activity, energy and the health of the environment, etc.

This territorial approach to the circular economy must also be included in the companies value chains, enabling them to achieve ultimately a positive water footprint. It should be feasible for this positive footprint to be more widely applied, in as far as is possible, to all the ecosystems with which companies interact. It is in this way and only in this way that the great battles for the survival of our planet will be won.

1 - Act4nature is an initiative launched in France by EpE (Entreprises pour l environnement) and many partners to mobilize companies to protect, enhance and restore biodiversity.

CHALLENGE

In the Montélimar (France) wastewater treatment plant, the sludge are transformed into compost

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