MIT researchers unveil groundbreaking desalination system

A research team at Massachusetts Institute of Technology (MIT) has developed a desalination system that uses a powerful electric field acting on a stream of flowing water. The field pushes ions in the salty water to one side of the flow and fresh water to the other so the two streams can be readily separated.

This approach – called called shock electrodialysis – is “a fundamentally new and different separation system,” according to the leader of the research, professor of chemical engineering and mathematics, Martin Bazant. It carries out a “membraneless separation” of ions and particles from water.

In Bazant’s process, water flows through a porous column of glass particles sandwiched between electrodes that create “a very strong gradient” according to Bazant. When current flows through the electrodes, the salt solution in the glass column divides into a high salt concentration flow and a low concentration flow. When the electric current is increased it reaches a point where it creates a shock that splits the fresh and saline stream so they can be separated by a barrier placed at the dividing line between he two flows.

Bazant explained that the system does not drive water through a membrane to effect separation so it is not susceptible to fouling as in reveres osmosis or even conventional eletrodialysis.

The new system is a continuous process, based on water flowing through an inexpensive porous medium that the MIT team claim should be easy to scale up for desalination.

The system not only removes salt, but also other contaminants — and because of the electrical current passing through, it may also sterilize the stream said research team member, graduate student Sven Schlumpberger. “The electric fields are pretty high, so we may be able to kill the bacteria,” he says.

The research produced both a laboratory demonstration of the process. Bazant said the next step was to scale that up and carry out practical testing. Initially shock electrodialysis would not compete with reverse osmosis for large-scale seawater desalination, but it could applications in treating produced water such as water effluent from tracking, Schlumpberger said.

He went on to say the system needs little by the way of infrastructure, so it might form the basis of portable systems for use in remote locations.