MIT has developed a method using solar energy to turn brackish water (a mixture of salt and fresh) into water suitable for irrigation and drinking. Here's an excerpt:
A team from the Massachusetts Institute of Technology and Jain Irrigation Systems have come up with a method of turning brackish water into drinking water using renewable energy. With parts of the planet running dangerously low on fresh water, this technology can’t come soon enough.
This solar-powered machine is able to pull salt out of water and further disinfect the water with ultraviolet rays, making it suitable for irrigation and drinking. As the MIT News Officeexplained, “Electrodialysis works by passing a stream of water between two electrodes with opposite charges. Because the salt dissolved in water consists of positive and negative ions, the electrodes pull the ions out of the water, leaving fresher water at the center of the flow. A series of membranes separate the freshwater stream from increasingly salty ones.”
Called a “photovoltaic-powered electrodialysis reversal system,” the technology recently won the top $140,000 Desal Prize from the U.S. Department of Interior (USID) that recognizes innovators who create cost-effective, energy efficient and environmentally sustainabledesalination technologies that can provide potable water for humans and water for crops in developing countries, the USID announced.