Transformation of waste into raw material: Reuse of rejected brines from desalination plants for hydroponic cultivation

Rejected brines discarded by seawater desalination facilities can be used in hydroponic cultivation as a source of minerals and water.

This trial study, a collaboration between researchers from the IPNA Agrobiotechnology group, also points out that this brine can be made the basis of a circular economy that maximizes reuse and evaporation to reduce water consumption in tourist and leisure facilities.

Desalination of seawater is not 100% effective, despite improvements achieved by implementing new desalination technologies. These processes generate liquid waste effluent called residual brine, a serious potential threat to the flora and fauna of marine ecosystems, since it is normally released into the sea. This study was carried out by the Institute of Natural Products and Agrobiology, the University of La Laguna (Tenerife), the Zaidín Experimental Station - CSIC (Granada) and the Fundación Centro Canario del Agua. It shows that ‘wastes’ such as these can be reused as potential raw materials, after suitable processing, adapting them as a nutritive mineral solution in hydroponic cultivation systems and also as a possible source of fresh water.

The results of this research indicate that the use of residual brines in a 1/40 solution for the cultivation of tomato plants in a greenhouse provides the fruits with excellent organoleptic quality. This was demonstrated by parameters measured in the tomatoes, such as soluble solids, dry matter percentage, titratable acidity and pH. Furthermore, the study shows that by applying improved evaporation technologies, such as membrane distillation with solar energy, the excess solution generated in the greenhouse can be used to produce water for fertilization and for irrigation of gardens.

In regions such as the Canary Islands, where seawater desalination plants have been used to meet the demand for fresh water by the tourist industry for more than 50 years, the implementation of measures such as these in a circular economy would lead to an obvious improvement in the environmental sustainability of these facilities. They could also provide quality value to the resulting agricultural products.

The results of this multidisciplinary research project, funded by the CajaCanarias Foundation, have been published in the journal “"Desalination"”(Elsevier group).

By Andrés Borges

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