Saur France will be tasked with maintaining the high level of performance and technical expertise of a remarkable network and plant infrastructure. This infrastructure includes:
- The Carré de Réunion wastewater treatment plant (350,000 population equivalents) in Saint-Cyr l’Ecole, which incorporates the largest membrane treatment unit in Europe, using ultrafiltration to purify water to a higher standard than conventional treatments;
- The Val de Gally wastewater treatment plant (40,000 population equivalents) in Villepreux;
- Nearly 20 km of large collectors with a diameter of over 2 m.
This ambitious new partnership responds to local expectations in terms of transparency, investment, and respect for the environment, placing improving residents’ quality of life at the heart of its priorities.
The contract, which will begin on January 1st, 2026, for a period of 12 years, represents annual revenue of €17 million. It is now Saur’s largest sanitation contract in France. It covers an area with a population of 500,000 and 31 municipalities belonging to three main public establishments for inter-municipal cooperation (EPCI): Versailles Grand Parc, Grand Paris Seine Ouest, and Saint-Quentin-en-Yvelines.
The contract was officially signed on Wednesday, September 24th, 2025, in the presence of:
- Marc Tourelle, President of the Hydreaulys syndicate and Mayor of Noisy-le-Roi, and some of the union’s elected officials;
- Philippe Leroy, Managing Director of Services, and Hydreaulys services;
- Patrick Blethon, Executive Chairman of the Saur Group, and Estelle Grelier, President of Saur France.
A public service that preserves water quality and protects natural environments
In line with GEMAPI (aquatic environment management and flood prevention) responsibilities, which are handled by Hydreaulys in its capacity as a river authority, the contract provides for concrete actions to manage the water cycle in an integrated manner and ensure the sustainable protection of natural environments:
- Preservation of the Gally stream thanks to an investment of several million euros to significantly reduce direct discharges and spills;
- Strengthening of the resources dedicated to managing the sanitation system for greater safety and anticipation in wastewater transport thanks to predictive models and hundreds of sensors distributed throughout the network;
- Greater comfort for local residents thanks to improved management of odor pollution at large treatment plants and transport networks.
Transforming sanitation into a driver of ecological transition
With this contract, Hydreaulys and Saur France are signing a binding partnership agreement to support the region’s ecological and energy transition. New actions and investments will be undertaken by both parties to reduce the impact of the facilities on the environment and stay ahead of certain regulatory changes relating to the environmental performance of wastewater treatment plants:
- Transformation of the Carré de Réunion wastewater treatment plant into a positive energy plant halfway through the contract (2032) thanks to the synergy between the two players:
- Hydreaulys’ investment projects for the installation of a solar farm that would produce green electricity covering 20% of the plant’s needs, and for the recovery of heat from effluents;
- Saur France’s commitment to reduce energy consumption by 16% and greenhouse gas emissions by 20% by 2031;
- Finally, a 15% increase in the amount of biomethane produced at the plant and injected into the city gas network.
- Development of the circular economy through the energy recovery of 100% of the sludge from wastewater treatment. Its local transformation will be used to supply the district heating network of the city of Plaisir.
- Increased reuse of treated wastewater with the production of 150,000 m3/year of water that can be used for agricultural irrigation or other purposes.
A new open local government, serving residents
With this new contract, Saur France will support Hydreaulys in the sustainable transformation of its sanitation service. The local teams, which will operate within a dedicated company called Hylio, will ensure the continuity of public service, while strengthening proximity to users and transparency vis-à-vis elected officials and the Syndicate’s services:
- Opening of a customer service center in Versailles to promote often overlooked professions and expertise. This center also aims to help residents understand the sanitation service, increase its visibility, and assist individuals with certain procedures;
- Development of a new educational space and opening of a visitor trail at the Carré de Réunion wastewater treatment plant to strengthen the ability to raise awareness among young people in the area;
- Contribution to the local economy with 35% of purchases made from local businesses.
Together, we are shaping a new service for users that will drive trust and transformation: protecting the environment to preserve citizens’ quality of life and ensure control of the water cycle.
"With Saur, we have chosen a bid that offers a comprehensive and consistent vision across the union's three main areas of expertise: wastewater collection, transport, and treatment. Choosing a new company is a bold move for Hydreaulys, but one that will enable us to raise the profile of our work and continue to pursue our ambition for excellence. This contract, with its strong commitments, is intended to be a real driver for the circular economy in the region and an example of ecological transition. With this new contract, we are building a win-win partnership that guarantees continuity of rates while increasing the level of service. "
"This partnership with Hydreaulys is a major and prestigious reference for the Saur group. It reflects a shared ambition: to protect the natural environment while modernizing public services. By focusing on transparency, innovation, and proximity, we want to respond concretely to the expectations of residents and improve their daily living environment. "
