CERN Accelerating science

Water protection

CERN strives to minimise its water consumption through continuous consolidation and improvement of its cooling and sanitation infrastructures. Since 2000, CERN has radically decreased its water consumption by some 80%, from 15 000 megalitres that year to 3234 megalitres in 2022, notably by changing the water circuits in its cooling towers from open to semi-open or closed ones during LS2.

The water used at CERN is mainly supplied by the Services Industriels de Genève (SIG). The raw water is pumped from Lake Geneva (CH), processed to drinking water quality at a treatment centre in Bellevue (Canton of Geneva), and then delivered to CERN.

Water at CERN is mainly used for cooling the accelerator facilities, for industrial activities and for sanitary purposes. Good practices are applied to guarantee sustainable consumption of water and most of the water is returned into watercourses neighbouring CERN’s premises, notably the Nant d’Avril in Switzerland and the Allondon and Lion in France. Effluents from CERN’s facilities are continuously monitored at the main water discharge points into these watercourses. For more information, please see CERN’s environment reports.

Some of the water used in cooling circuits evaporates into cooling towers and results in water vapour releases. Water in cooling towers is checked regularly and treated in accordance with the Host States' regulations so as to limit any bacterial issues.

The sanitary water is directed to Swiss wastewater treatment plants for treatment previous to their discharge into rivers.