According to the Securing Water for Food agency, between 2000 and 2050 water demand is expected to increase 55 percent globally, meaning the number of people affected by water scarcity will continue to grow. By 2025, two-thirds of the world's population could be living in severe water stress conditions.
Around the world, there is more salty groundwater than fresh, drinkable groundwater. For example, 60 percent of India is underlain by salty water — and much of that area is not served by an electric grid that could run conventional reverse-osmosis desalination plants.
To find solution for this drinking water issue in developing countries, USAID the U.S. Agency for International Development had run a global competion for Desal prize.
The idea for the competition was to create a system that could remove salt from water and meet three criteria: it had to be cost-effective, environmentally sustainable, and energy efficient.
The winners of the $140,000 first prize were a group from MIT and Jain Irrigation Systems. The group came up with a method that uses solar panels to charge a bank of batteries. The batteries then power a system that removes salt from the water through electrodialysis, that means that dissolved salt particles, which have a slight electric charge, are drawn out of the water when a small electrical current is applied.
Using the sun instead of fossil fuels to power a desalination plant isn't a totally new idea. Larger solar desalination plants are being seriously investigated in areas where water is becoming a scarce resource, including Chile and California.But the current technology is expensive.
The MIT team's this new desalination technology "electrodialysis" is comparatively less expensive.
Both electrodialysis and reverse osmosis require the use of membranes, but the membranes in an electrodialysis system are exposed to lower pressures and can be cleared of salt buildup simply by reversing the electrical polarity. That means the expensive membranes should last much longer and require less maintenance. In addition, electrodialysis systems recover a much higher percentage of the water — more than 90 percent, compared with about 40 to 60 percent from reverse-osmosis systems, a big advantage in areas where water is scarce.
Image credit: MIT
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