Washington, Sep 9 :
Researchers have found that a desalination technology called electrodialysis – powered by solar panels – could provide enough clean and palatable drinking water to meet the needs of water-deficient Indian villages.
There is more salty groundwater than fresh, potable groundwater in India as 60 percent of the country has vast reservoirs of salty water underground.
After weeks of field research in India and reviews of various established technologies, the researchers from the Massachusetts Institute of Technology in the US found that electrodialysis, which is not what is commonly used in developing nations, could offer an effective solution to the problem of salty water.
“An economically viable and culturally acceptable system could supply enough water to meet the needs of a village of 2,000 to 5,000 people,” said researchers Natasha Wright and Amos Winter.
They estimated that deployment of such systems would double the area of India in which groundwater – which is inherently safer, in terms of pathogen loads than surface water – could provide acceptable drinking water.
Viewing the salinity levels present in India’s groundwater, the researchers found that an electrodialysis system could provide fresh water using half the energy required by a reverse-osmosis system.
That means the solar panels and battery storage system can be half as big, more than offsetting the higher initial cost of the electrodialysis system itself.
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 centre of the flow.
A series of membranes separate the freshwater stream from increasingly salty ones.
Both electrodialysis and reverse osmosis require the use of membranes, but those in an electrodialysis system are exposed to lower pressures and can be cleared of salt buildup simply by reversing the electrical polarity.
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.
Having carried out this analysis, Wright and Winter plan to put together a working prototype for field evaluations in India in January.
The study appears in the journal Desalination.