Desalination is a process that removes salts or chemical compounds from impure water in order to purify it.  During this process salt water is heated in order to make the water evaporate and therefore leaving the salt behind.  The second step consists of condensing the desalinated vapor in order to form water into a separate container. In many areas of the world this process can be a lifesaver to serious water shortage situations such as droughts or contaminations.

A new approach to desalination is being developed by researchers at MIT (Massachusetts Institute of Technology) will hopefully lead to small and portable desalination units that could be powered by solar cells or batteries. This could be a useful and efficient solution to deliver water the entire villages and needy families.  This process would also have the extra advantage of removing contemporaneously many contaminants and bacteria present in that same water.

The new approach, called ion concentration polarization, is described in a paper by Postdoctoral Associate Sung Jae Kim and Associate Professor Jongyoon Han, both in MIT’s Department of Electrical Engineering and Computer Science, and colleagues in Korea.

“ The system works at a microscopic scale, using fabrication methods developed for micro fluidics devices — similar to the manufacture of microchips, but using materials such as silicone (synthetic rubber). Each individual device would only process minute amounts of water, but a large number of them — the researchers envision an array with 1,600 units fabricated on an 8-inch-diameter wafer — could produce about 15 liters of water per hour, enough to provide drinking water for several people. The whole unit could be self-contained and driven by gravity — salt water would be poured in at the top, and fresh water and concentrated brine collected from two outlets at the bottom” (source: http://www.sciencedaily.com/releases/2009/08/090819135931.htm).

Professor Kim explains that the small size could actually be an advantage for various situations. For example, in an emergency situation like Haiti’s earthquake aftermath, the delivery infrastructure to get fresh water to the people who need it was largely lacking, so small, portable units would have made a huge difference.

So far, the researchers have successfully tested a single unit, using seawater they collected from a beach in Massachusetts. The amount of electricity required by this method is a bit more superior than the one needed for current large-scale methods such as reverse osmosis.. If properly engineered, this system would only use as much power as a light bulb.

The principle that makes this possible is called ion concentration polarization, a phenomenon that occurs near ion-selective materials (such as Nafion, often used in fuel cells) or electrodes. and this team and other researchers have been applying the phenomenon for other applications such as biomolecule preconcentration. However, this application has not been test yet for water purification purposes.

Up to now, one of the leading desalination methods used is called reverse osmosis. This procedure uses membranes that filter out the salt; but these membranes need strong pumps to maintain the high pressure in order to push the water. For this reason the membranes are often subject to fouling or blockages. “The new system separates salts and microbes from the water by electrostatically repelling them away from the ion-selective membrane in the system — so the flowing water never needs to pass through a membrane. Researchers say that this should eliminate the need for high pressure and the problems of fouling” (source: http://www.sciencedaily.com/releases/2009/08/090819135931.htm).

Having proved the principle in a single-unit device, Kim and Han plan to produce a 100-unit device to demonstrate the scaling-up of the process, followed by a 10,000-unit system. They expect it will take about two years before the system will be ready to develop as a product. “After that,” says Kim, “we’ll know if it’s possible” for this to work as a robust, portable system, “and what problems might need to be worked on.”

Water is a precious resource and its scarcity in many of the regions of the world is alarming because it puts at risks the survival of people, wildlife and agricultural economies. The process of desalination is worth investing into for a long-term sustainable future especially in needing areas or upon the sites where tragedies and natural disaster like an earthquake have occurred. In Haiti this process could have saved the life of many children while assuring a basic resource needed to the survival on the people and their lands. In areas where agriculture is the only income, water becomes a matter of life or death.