The annual water consumption of CERN in 2020 was about 1.9 million m3. With the LHC being in its second long shutdown (LS2), about 47% less water was needed than in operational years. CERN decreased its water consumption radically from 15 million m3 in 2000 to 3.5 million m3 in 2018 (last run year before LS2), principally by changing its cooling tower water circuits from open circuits to semi-open or closed ones.
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.
CERN’S ANNUAL WATER CONSUMPTION 2000 - 2020. Based on data from Services Industriels de Genève and Régie des Eaux Gessiennes.