Filterless portable device uses electricity to make seawater drinkable

MIT researchers have developed a portable desalination unit, which weighs less than 10 kg and can remove particles and salts to generate drinking water.

The suitcase-sized device requires less power to operate than a cell phone charger and can be powered by a small, portable solar panel.

Automatically generates drinking water that exceeds WHO quality standards. The technology is built into an easy-to-use device that operates at the touch of a button.

Unlike other portable desalination units that require the water to pass through filters, this unit uses electrical energy to remove particles from drinking water. Since no filters are required, long-term maintenance requirements are greatly reduced.

This could allow the unit to be deployed to remote areas with very limited resources, such as small island communities or aboard sea freighters. It could also be used to help refugees fleeing natural disasters.

It is truly the culmination of a 10 year journey that my group and I have been on. We have worked for years on the physics of each of the desalination processes, but putting all of these advances together in a box, building a system and demonstrating it in the ocean has been a really meaningful and rewarding experience for me.

Jongyoon Han, professor of electrical and computer engineering and biological engineering.

Filterless technology.

Commercially available portable desalination units often require high-pressure pumps to push water through filters, which are very difficult to miniaturize without compromising the energy efficiency of the device.

Instead, his unit relies on a technique called ion concentration polarization (ICP). Instead of filtering water, the ICP process applies an electric field to membranes placed above and below a water channel. The membranes repel positively or negatively charged particles – including salt molecules, bacteria and viruses – as they pass. The charged particles are conveyed in a second flow of water which is finally evacuated.

The process removes dissolved and suspended solids, allowing clean water to pass through the channel. Because it only requires a low pressure pump, the ICP consumes less energy than other techniques.

But ICP does not always remove all the salts floating in the center of the channel. So the researchers incorporated a second process, called electrodialysis, to remove the remaining salt ions.

Yoon and Kang used machine learning to find the ideal combination of ICP and electrodialysis modules. The optimal setup includes a two-stage ICP process, with water flowing through six modules in the first stage, then through three in the second, followed by a single electrodialysis process. In this way, the energy consumption is minimized and the self-cleaning of the process is guaranteed.

They shrunk and stacked the ICP and electrodialysis modules to improve their energy efficiency and allow them to fit in a portable device. The researchers designed the device for non-experts, with a single button to start the desalination and purification process automatically. Once the salinity level and the number of particles have reached specific thresholds, the device notifies the user that the water is safe to drink.

The researchers also created a smartphone app that can wirelessly control the unit and report real-time energy consumption and water salinity.

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His prototype generates drinking water at the rate of 0.3 liters per hour and requires only 20 watts of power per litre.

His idea now is to reduce its price and make it with low cost materials.

Going through mit.edu

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