Solar electrodialysis brings water to off-grid villages

A simple set of solar panels and a battery system connected to an electrodialysis desalination unit could provide fresh water for a typical Indian village according to researchers at the Massachusetts Institute of Technology (MIT) in the US.

The MIT scientists found that Indian communities with no connection to the power grid but with access salty groundwater could get potable water through their proposed solar technique.

Salty groundwater is present under some 60% of India and much of that area is not served by an electricity grid that could power (say) conventional reverse-osmosis desalination plants.

The study, by MIT graduate student Natasha Wright and Professor Amos Winter, showed that solar powered electrodialysis of saline groundwater could provide enough clean drinking water to supply the needs of a typical village.

Winter said the search for optimal solutions to exploit saline groundwater – with weeks of field research in India, and reviews of established technologies – “pointed very strongly to electrodialysis” – which is not commonly used in developing nations.

Electrodialysis emerged as the lead candidate technology because of the low-salinity of the groundwater at 500-3,000 mg/l compared with seawater at about 35,000 mg/l and the region’s lack of electrical power.

The health effects of drinking low salinity water are long-term but its unpleasant taste drive people to drink dirtier sources.

Pairing village-scale electrodialysis with solar panels and a battery to store the solar power, creates an affordable way to produce enough palatable water for 2000-5000 people, there researchers concluded.

Deployment of such systems would double the area of India in which groundwater could provide acceptable drinking water according to the MIT team. And groundwater carries a lower pathogen risk than surface water. Furthermore, electrodialysis recovers more than 90 per cent of the treated water making it ideal where water is scarce.

The researchers plan to put together a working prototype for field evaluations in India in January 2015. While this approach was initially conceived for village-scale, self- contained systems, Winter said it could apply in disaster relief and military use in remote locations.