Veolia Upgrades Europe’s Largest Wastewater Treatment Plant

Image source: Veolia

Published on March 20, 2025

The Seine Aval wastewater treatment plant, Europe’s largest and a key facility serving 6 million residents in the Paris region, has reached a major milestone in its modernization with the inauguration of a new primary settling unit. Designed and constructed by Veolia, the facility enhances treatment efficiency, energy savings, and environmental performance while addressing the challenges of high population density and frequent heavy rainfall in the area.

The new unit, capable of treating up to 34 m³/s of wastewater—equivalent to over 50 Olympic swimming pools per hour—features advanced digital tools and innovative technologies. These include lamellar settlers for removing fine particles, predictive control systems to optimize energy and reagent use, and a heat recovery system to reduce environmental impact. Additionally, the facility is fully covered to minimize odors, improving the quality of life for nearby residents.

This €511 million project, part of a broader modernization initiative launched in 2009, aligns with European water directives and aims to improve water quality in the Seine and Marne rivers. The upgrade also incorporates biodiversity protection measures, ensuring the preservation of local ecosystems.

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