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Inauguration of the Eaux Blanches wastewater treatment plant in Sète, Occitanie region, a key facility to protect the environment and accelerate the energy transition
Loïc Linares, President of Sète agglopôle méditerranée, Hervé Marques, Mayor of Sète, Karine Bonacina, Director of the Montpellier delegation of the Rhône Méditerranée Corse Water Agency, Arnaud Bazire, CEO of SUEZ Water France, and François-Xavier Lauch, Prefect of Hérault, inaugurated the new Eaux Blanches wastewater treatment plant in Sète, Hérault, on June 14th, 2025. Located on the Mediterranean coast, the plant plays a vital role in preserving resources in an environmentally sensitive area weakened by climate change.
“We have chosen a plant with high environmental and territorial added value. The Eaux Blanches wastewater treatment plant is an investment that perfectly meets our needs and will shape the future of the region.”, said Loïc Linares, President of Sète agglopôle méditerranée.
“The Eaux Blanches wastewater treatment plant demonstrates the ability of local authorities to address the challenges of water transition, aquatic environment preservation and climate change adaptation. It is a concrete response resulting in facilities that are simple, smart and integrated.”, said Karine Bonacina, Director of the Montpellier delegation of the Rhône Méditerranée Corse Water Agency.
As challenges become more complex and require a systemic and collaborative approach, we are proud to contribute to the industrial ecology initiative launched by Sète agglopôle méditerranée to provide a sanitation service that protects the environment and recovers resources.Arnaud Bazire , CEO of the Water France activities of SUEZ
A new wastewater treatment plant to address demographic pressure and climate change
The new Eaux Blanches wastewater treatment plant is a model of innovation by Sète agglopôle méditerranée to tackle the challenges of preserving resources and sensitive natural environments while promoting regional development. In 2018, the local authority launched a project to modernise the sanitation infrastructure and build a new plant. This major project led by Sète agglopôle méditerranée, the Rhône Méditerranée Corse Water Agency and Thau Maritima (a project company created by SUEZ and the investment company Vauban Infrastructure Partners), represents an investment of more than €64 million.
The new plant treats 89% of the wastewater from seven municipalities of Sète agglopôle méditerranée – representing 6.5 million m3 of wastewater treated per year, equivalent to 165,000 inhabitants, with a capacity that can be extended to 190,000 population equivalent. The expansion of treatment capacity adresses the needs of this Mediterranean coastal area, whose population doubles during summer, resulting in growing sanitation demands, and which is bearing the brunt of climate change (prolonged droughts and heavy, rapid rainfall).
With this new plant, SUEZ is confirming its expertise in wastewater treatment and recovery, which is an essential lever for preserving water resources and sensitive natural environments. The Group operates 270 wastewater treatment plants in France.
A plant equipped with cutting-edge technologies to improve the quality of treated water
The Eaux Blanches wastewater treatment plant uses ultrafiltration membrane technology to treat wastewater. It meets the strictest regulatory requirements and removes over 90% of organic pollution to achieve “Class A” or “bathing water” quality discharge, thereby preserving the Mediterranean Sea and the Thau Basin, a sensitive ecosystem located near the plant.
The plant is equipped with a storm basin to store excess wastewater during rainy periods and a differentiated operating system that adapts to high rainfall. These devices are designed to minimise overflow risk and optimise the quality of wastewater released into the natural environment. These innovative processes contribute to the preservation of aquatic environments and local economic activities, particularly shellfish farming, which is essential to the region.
A virtuous model of circular economy and industrial ecology using wastewater
The Eaux Blanches wastewater treatment plant is a prime example of the circular economy, producing reusable wastewater and renewable energy for local use. Located within the Val'Thau ecopole, the plant is connected to the neighbouring waste-to-energy plant and the industrial company SAIPOL to optimise water, energy and material flows. This collective governance, led by Sète agglopôle méditerranée, contributes to the region's water and energy resilience.
The plant recovers sludge from wastewater treatment to produce 500,000 Nm³ of biomethane per year, which is fed back into the GRDF network. It also recovers 2,800 MWh of steam from the waste-to-energy plant to dry the sludge. From 2025, this steam will be used to heat the digester, thereby improving the performance of the methanisation process. The residual sludge is then composted and used in local agriculture, thus closing the recovery chain.
Additionally, a Treated Wastewater Reuse unit helps preserve drinking water resources. Currently, more than 60,000 m³ of treated water per year is used by the waste-to-energy plant. Starting in 2026, an additional 540,000 m³ per year will be used for SAIPOL's industrial activities. These strictly regulated initiatives address climate and water issues while supporting the region's strategic activities.
Finally, from 2025, an educational tour will welcome 20 school classes per year to explore the synergies between water management, energy recovery, and circular economy. Developed in collaboration with the Ecopole's partners, this educational programme will provide younger generations with the knowledge and tools to understand and address environmental challenges.
A complex modernisation project for the benefit of the region
Sète agglopôle méditerranée and Thau Maritima have taken up the challenge of a complex large-scale project, launched in 2018, to rebuild the Eaux Blanches wastewater treatment plant while ensuring the continuity of public sanitation services. Notably, 55% of the project's turnover was awarded to small and medium-sized businesses in Occitanie, a third of which are based in the Sète agglopôle méditerranée area. This project ranks among the most significant construction projects for SUEZ's Water activities in France in the last 10 years.
In addition to its technical performance, the plant blends harmoniously into the urban landscape thanks to its contemporary architecture and features designed to minimise visual, noise and odour pollution. Since 2018, the project has generated more than 45,000 hours of professional integration and supported the training of future water professionals, thereby strengthening its role as a driving force in the local ecological and economic transition.