Jones, E.R. and M. Qadir. 2021. The state of desalination and brine production. In: UNESCO-Encyclopedia of Life Support Systems (EOLSS), EOLSS Publishers, Paris, France. Available at: https://www.eolss.net
Access to clean water is vital for protecting life, livelihoods and for achieving sustainable development. Trends towards increasing water demands, decreasing clean water availability and urbanization are exacerbating water scarcity in most world regions. Conventional water resources such as lakes, rivers and aquifers fed by rainfall, snowmelt and river runoff are becoming increasingly overstressed, with trends in water conservation and improved water use efficiencies insufficient to close the supplydemand gap. Unconventional water resources, such as desalination and treated wastewater re-use, are increasingly recognized as viable options for water supply enhancement. Continually improving unconventional water resources technologies have permitted more efficient and economical tapping of water resources which were previously unusable due to access constraints or the added costs related to unsuitable water quality. Desalination can either extend clean water availability beyond what is available from the hydrological cycle (e.g. seawater) or improve the quality of existing water sources below sectoral thresholds (e.g. brackish water). Whilst desalination has enormous potential, specific barriers pose constraints to its widespread application. Barriers include economic costs, greenhouse gases emissions and effluent management. The disposal of a concentrated effluent stream (brine) produced in the desalination process simultaneously poses technical, economic and environmental challenges.