Those scientifically curious Greeks who guessed at the marine-based origin of life, wondered about the paradox that almost all water on Earth is brackish and that this life, at least terrestrial life, cannot filter it. It was not until 1872 that the Aristotelian dream materialized with the first facility capable of desalinating water, using solar heat, from wells in the Chilean Atacama Desert. After World War II, the first indus-trial plants that enabled evaporation, by means of large amounts of thermal energy, were built. In the mid-sixties, another tech-nological leap occurred: the invention of reverse osmosis membranes, the most efficient, sustainable and economic system known. Alberto Garrido, director of the Botín Foundation’s Water Observatory, summarizes how it works: “The salty water is passed at very high pressure through an osmotic membrane, that separates the H2O from the dissolved chemical components, including sodium chloride.” But the important thing is what is its purpose.Together with water reuse, reverse osmosis is held up one of the great hopes for tackling sev-eral simultaneous challenges: to combat the water stress that is advanc-ing with global warming, while ensuring supply to a growing popu-lation, and closing the circle by decarbonizing the economy to curb the climate change that exacerbates water scarcity, explains Fernando Cortabitarte, director of the Water Cycle at ACCIONA. The director speaks from the knowledge gained in a company that leads the field in R+D, quality improvement, reducing our environmental impact and making a productive leap in scale in reverse osmosis, as is demonstrated ToDAY, SoME 2.2 BILLION HUMAN BeINGs dO NOT HAVE accesS To a SAFE SUPPLY OF QualiTY WATER WATER FRESH WATER TO EAT FRESH WATER TO EAT There is an obvious relationship between reverse osmosis and the UN Sustainable Development Goal 6: to guarantee the avail-ability of quality water and its sustainable management. But its relationship with SDG 2, which aspires to zero hunger through food security, is also beginning to become clearer. How? The desalinated water is converted into water for eating through a specialized process suitable for crop irrigation and seamless-ly integrates into intensive agricultural practices, which opti-mizes production while minimizing the use of both space and irrigation. It thus emerges as a key ally of the primary sector that some voices are beginning to consider tertiary, namely an essential service for fostering a sustainable economy and envi-ronmental well-being. “Desalination for agricultural purposes is a favorable alternative offering a reliable supply, within a short period of time and within a timeframe of three to five years. Moreover, its stable prices allow long-term investment planning in this crucial sector,” points out Fernando Cortabitarte, director of the Water Cycle.