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España, Technology for Life is a campaign to showcase Spanish tech businesses and sectors.

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Desalination in Spain

Desalination in Spain

History of Desalination

The idea that pure water could be made from seawater has been tantalizing thirsty humans for hundreds, if not thousands, of years. The original premise was based on the idea that boiling or evaporating water separates the water from the salt. That theory—vaporization or distillation—was behind the technology for the first large-scale desalination plants that sprouted in desert areas in the 1950s and 1960s, primarily in the Middle East. These areas, lacking water but with plenty of fuel to burn, turned one resource, energy, into what the region craved: water. The technologies using heat, though, require vast amounts of energy.

Researchers throughout the early 1900s had been studying the idea of using a membrane to separate out salt from seawater. This is based on the osmotic nature of cell walls: certain semipermeable membranes, such as animal and plant cell walls, allow water to pass through, creating an equilibrium between a highly concentrated solution on one side of the membrane and a diluted concentration on the other.

Scientists hypothesized that with the right amount of pressure and with the correct membrane design, this natural phenomenon could be reversed through a man-made membrane. Instead of flowing from a diluted solution to a highly concentrated one, equalizing them both, the concentrate could be forced through a membrane, leaving an even higher concentrated solution of dissolved solids (in this case, salt) behind.

In the 1960s, researchers in the U. S. and Japan who developed membranes for industrial purposes soon realized that those same semipermeable man-made membranes could be used in desalination. By the 1970s, desalination-plant developers adopted reverse osmosis (RO) for use in new desalination plants.

Though more efficient than vaporization or distillation and requiring far less physical space for the same operation, these plants still demanded a high energy input. Over time, engineers developed recovery systems to take advantage of the high pressure of waste brine left after the reverse-osmosis process. This has led to precipitous drops in energy needs for the process, reducing the cost, while the cost of the membranes used in reverse-osmosis technology have also dropped about 50 percent.

At the same time, conventional sources of fresh water have proven more costly in recent years. In some areas, coastal aquifers are depleted of water before they can refill naturally, leading to the intrusion of seawater. All these factors contribute to the fact that, in some regions, desalination has become cost-competitive with traditional methods of supplying water needs.

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