The Consorci Besòs Tordera (CBT) is a local water institution founded in 1988 and composed of 56 entities, counting among them 52 cities of four different Catalonia regions –i.e. Barcelonès, Osona, Vallès Occidental and Vallès Oriental–, with a population of about 2400000 inhabitants. The rest of its members are the Barcelona Council (Diputació de Barcelona), the Barcelona Metropolitan Area (Àrea Metropolitana de Barcelona), the Vallès Oriental Regional Council and the Consortium for Waste Management of the Vallès Oriental. The CBT area of activity is the sanitation –sewage systems, discharges, Wastewater Pump Stations (WWPSs) and Wastewater Treatment Plants (WWTP) monitoring and management–, improvement of the river environment –six rivers in its area: Mogent, Congost, Tenes, Ripoll, Besòs and riera de Caldes–, promotion and environmental education and support to the consortium entities. 39 of the 52 consortium cities have delegated their functions as an active administration in the field of sanitation to CBT, with an equivalent population of 430000 inhabitants and more than 4000 industrial establishments. The CBT activities involve the sanitation of a municipal sewage network of 1250 km –including conservation and cleaning services of the sewage system, as well as improvement of the installations–. On the other hand, to carry out the water sanitation, CBT has 18 WWTPs, almost 300 km of additional sewer pipelines and 45 WWPSs.