Villette (GE) and Ocybèle (F) STEPs: connection planned for 2023

The State of Geneva, Annemasse Agglo and the Geneva Industrial Services (SIG) provided an update on Thursday on the progress of the Villette STEP site. Started in 2018, large-scale works will be completed in 2023 with the connection of the Ocybèle WWTP, in Gaillard (F), for joint treatment of micropollutants.

This cross-border collaboration will eliminate 80% of the micropollutants from the water discharged into the Arve by these two large treatment plants, the partners indicated on Thursday in a press release.

This project is part of the amendment to the federal law on water protection, which occurred in 2016. The wastewater treatment plants (STEP) of Villette and Ocybèle today treat wastewater from around 142 ‘000 inhabitants. After treatment, the water from Ocybèle will be transported to Villette by a collector for the micropollutant elimination phase.

Preserving the Arve

This partnership will make it possible to improve the quality of the water discharged by these two large WWTPs to preserve the water of the Arve and the groundwater. Today, approximately 50% of the micropollutants measured in the Arve in Geneva come from these two WWTPs and cannot be eliminated at source.

The complex site began in 2018. Divided into two main phases, it consists of demolishing the old facilities and building the new ones while guaranteeing the operation of the site.

Already an improvement

Prior to the treatment of micropollutants, the WWTP was enlarged, renovated and modernized. Since the commissioning of the first phase, in April 2021, a marked improvement in the quality of the water discharged into the Arve has already been noted, underlines the press release.

The overall investment for this project amounts to 62 million francs, including 14 million for the micropollutant treatment facility. The Confederation contributes 75% of the investment for micropollutants.

‘Taking into account the inhabitants connected from France made it possible to obtain this Swiss subsidy’, noted Christian Brunier, director of GIS. The remaining 25% is divided equally between SIG and Annemasse Agglo.

Modernization in France too

For its part, the French WWTP of Ocybèle, located about 500 meters from Villette, has undertaken modernization works for more than 30 million euros. Work on the collector that will connect it to Villette will start at the end of 2022 with a view to commissioning the treatment of micropollutants at the end of 2023 (the section under the Villette STEP has already been laid).

Villette is one of the four major STEPs in the canton of Geneva along with Aïre, Bois-de-Bay and Chancy. The current work at Villette is part of an overall plan for the expansion and modernization of wastewater treatment, agreed with the canton. This work and that to come on the Aïre site is part of the ecological transition by contributing to the carbon neutrality of GIS activities by 2030.

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