In India, 60 percent of the water body contains salty water, which is not served by an electric grid that could run reverse-osmosis desalination plants.
A new analysis shows through desalination technology called electrodialysis, powered by solar panels, clean, palatable drinking water can be recovered from salty water.
The study, by MIT student Natasha Wright and Amos Winter, the Robert N. Noyce Career Development Assistant Professor of Mechanical Engineering, appears in the journal Desalination.
Electrodialysis is common in developing nations and India can choose this method as Indian waters include low levels of salinity – ranging from 500 to 3,000 milligrams per liter, compared with seawater at about 35,000 mg/L.
In addition, the region’s lack of electrical power finds it feasible to use this technology as in case of on-grid locations reverse-osmosis plants can be economically viable.
In general, moderately salty water is not directly toxic, but it can have long-term effects on health.
By pairing village-scale electrodialysis systems, which is smaller than the industrial-scale units with a simple set of solar panels and a battery system to store the produced energy, an economically viable system can be made supplying enough water to meet the needs of a village of 2,000 to 5,000 people.
It is estimated that deployment of such systems will double the area of India in which groundwater can provide acceptable drinking water.
While many homes in India use home-based filtration systems to treat water, village-scale systems would be more effective as fewer people would be left out of access to clean water.
Most organizations working to improve clean-water access focus their attention on controlling known pathogens and toxins such as arsenic, which is not right.
With the salinity levels seen in India’s groundwater, an electrodialysis system can provide fresh water for about half the energy required by a reverse-osmosis system from solar panels and battery storage system which is half as big, offsetting the higher initial cost of the electrodialysis system itself.
In electrodialysis system are exposed to lower pressures and can be cleared of salt buildup by reversing the electrical polarity making the membranes last much longer with low maintenance.
In addition, electrodialysis systems recover 90 percentage of the water compared with about 40 – 60 percent from reverse-osmosis systems, a big advantage in areas where water is scarce.
Having carried out this analysis, Wright and Winter plan to put together a working prototype for field evaluations in India in January.
This approach, initially conceived for village-scale, self-contained systems can also be useful for applications such as disaster relief, and for military use in remote locations.
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