Supply of blends of desalinated seawater: effects on the flavour

The metropolitan area of Barcelona suffers from a well known lack of water resources. To mitigate this situation the El Prat Desalination Plant, a seawater reverse osmosis (RO) facility, is scheduled to come into operation during 2009. The network management project foresees supply in the southern area of the city of a blend of desalinated seawater and water from the River Llobregat. The latter could be treated in two ways: by conventional treatment consisting of the predioxychlorination, clarification, sand filtration, GAC filtration and postchlorination stages, or by means of this same process with an additional electrodialysis reversal (EDR) stage prior to postchlorination. In this study, an estimation of the organoleptic characteristics of the blends was carried out by trained and untrained sensory panels. The water samples for tasting were RO desalinated seawater (Tordera Plant), treated water from the Llobregat (Sant Joan Despí water treatment plant working under adequate conditions for the study), and the effluent from an EDR pilot plant. The results of the ranking, scoring and triangle difference tests indicated that the quality of the 50/50 blends improved in relation to the water from the Llobregat, although without reaching the level of quality of the water from the Ter basin, Barcelona's other important resource (North area).