New System Turns Salty Groundwater Into Drinking Water Using Solar Power

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As the world population continues to bloat at an alarming rate, so does our demand for food and water. It’s estimated that by 2050, the global water demand will have increased by a staggering 55%. But how are we going to meet this need when so many areas do not have access to drinking water or water that can be used for crops?

While many countries have plenty of groundwater to tap into, much of this is salty and therefore requires desalination, but in developing countries the electricity or facilities required to do this are lacking. That’s why the U.S. Agency for International Development (USAID), among others, have developed a competition that challenges scientists to come up with cost-effective, energy-efficient and environmentally sustainable desalination technologies that can create both drinking water and water for agriculture in developing countries.

After scrupulously testing the submitted systems, first prize was awarded to MIT and Jain Irrigation System’s invention that uses the sun to power a system that has the potential to provide enough potable water to supply the needs of a typical village in India of 2,000 to 5,000 people.

Their innovative creation uses a set of solar panels to generate energy that can then either be stored in batteries or fed into the desalination system. To then remove salt from the groundwater, the researchers decided to choose a process known as electrodialysis since this is suitable for relatively low salinity levels. While traditional methods, such as reverse-osmosis, can cope with higher salt levels, such as those found in seawater, they also require a much higher energy input.  

The process of electrodialysis involves passing water between two electrodes with opposing charges. Since the salt dissolved in the water is slightly charged, consisting of both positively and negatively charged ions, the electrodes attract them and draw them out. A series of membranes are then used to separate the salty water flow from the fresh water created by the process.

While removing salt makes the water suitable for use on crops, this alone is not enough to make it safe for drinking by humans. That’s why the researchers also combined this system with UV light, which helps destroy pathogens, like bacteria and viruses, present in the water.

After a careful analysis of the system, the researchers found they were able to recover around 90% of the water input, which is around double the amount that traditional reverse-osmosis systems typically recover. Furthermore, tests in New Mexico that required 24 hour, round-the-clock operation proved that it is durable and able to cope with high demand.

Having put it through its paces, the researchers are keen to install working prototypes for field evaluations in India next year. Although the system was originally created with remote villages in mind, the researchers also think it would be useful in other scenarios, such as disaster relief or military operations.

[Via MIT, PopSci and USAID]

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