News Feature | November 25, 2014

Photovoltaic-Powered Electrodialysis: A Water Solution For Rural Villages

Sara Jerome

By Sara Jerome
@sarmje

village.reg

Is sun-powered desalination the answer to water challenges in India?

The idea is appealing since around 60 percent of the country sits above saltwater, and large swaths of the country lack an electric grid to run reverse-osmosis desalination processes, according to the MIT New Office.

A new study by MIT researchers shows that electrodialysis desalination technology, powered by solar panels, can meet the water treatment needs of a typical village. The study, which appears in the journal Desalination, notes that conventional desalination processes are not viable for major sections of India.

"Most village-scale, on-grid desalination plants use reverse osmosis (RO), which is economically unviable in off-grid locations," the journal article said. Using photovoltaic-powered electrodialysis "has the potential to greatly expand the reach of desalination units for rural India."

The study was conducted by MIT graduate student Natasha Wright and Professor Amos Winter. Winter says it takes "detective work" to find viable water solutions and understand limitations posed by the market.

"The factors pointing to the choice of electrodialysis in India include relatively low levels of salinity – ranging from 500 to 3000 milligrams per liter (mg/L), compared with seawater at about 35,000 mg/L – and the region's lack of electrical power. For on-grid locations, the team found, reverse-osmosis plants can be economically viable," ECOS Magazine reported.

In January, Wright and Winter will put together plans for field evaluations in India.

"While this approach was initially conceived for village-scale, self-contained systems, Winter says the same technology could also be useful for applications such as disaster relief, and for military use in remote locations," the MIT News Office said.

What is electrodialysis? This process works by moving water between two electrodes.

"Because the salt dissolved in water consists of positive and negative ions, the electrodes pull the ions out of the water,” Winter says, “leaving fresher water at the center of the flow. A series of membranes separate the freshwater stream from increasingly salty ones," the MIT News Office reported.

India faces an uphill battle against an array of water challenges.

"Although India has made improvements over the past decades to both the availability and quality of municipal drinking water systems, its large population has stressed planned water resources and rural areas are left out. In addition, rapid growth in India's urban areas has stretched government solutions, which have been compromised by over-privatization," according to The Water Project, a non-profit sustainability project.

Image credit: "India – Rural Street," McKay Savage © 2009, used under an Attribution-ShareAlike 2.0 Generic license: https://creativecommons.org/licenses/by-sa/2.0/