Rejected brine recycling in hydroponic and thermo-solar evaporation systems for leisure and tourist facilities. Changing waste into raw material

For > 50 years the Canary Islands have been using seawater desalinization facilities in order to satisfy the freshwater demand of their main economic activity -tourism, which continues to contribute to the economic and social progress of the archipelago. However, this desalinization process involves the production of a "waste" product known as rejected brine, which is discharged from coastal regions and islands, whether it originates from public or private facilities. Rejected brines are potentially a serious threat to marine ecosystems. However, here we demonstrate that this "waste" can be processed and reused as a nutrient mineral solution for a hydroponic production system and also a source of freshwater. The efficiency of this management process in terms of fresh-water production and water recycling economy is also discussed. The aim of this paper is to change the attitude towards rejected brines, which should be treated as potential raw material to permit high savings in the running costs of leisure and tourist facilities around the archipelago. In addition, this will also have a positive effect on the environment, making desalinization more sustainable and environmentally friendly, which is nowadays an added value in customer and user satisfaction.