With no fuss, a portable dealination unit distributes drinking water from seawater

With no fuss, a portable dealination unit distributes drinking water from seawater ...

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

The suitcase-sized device, which requires less energy to operate than a cell phone charger, can be fitted with a small portable solar panel, which can be purchased online for around $50. It automatically generates drinking water that exceeds World Health Organization quality standards. The technology is packaged into a user-friendly device that runs with the push of one button.

This device, which is similar to those used in portable desalination machines that require water to pass through filters, utilizes electrical power to remove particles from drinking water. Long-term maintenance restrictions are greatly reduced.

This may be used to assist refugees fleeing natural disasters or by soldiers performing long-term military operations.

This is truly the culmination of a 10-year journey that I and my group have been on. We worked for years on the physics behind individual desalination processes, but putting all of the advances into a box, building a system, and demonstrating it in the ocean, for me, according to senior author Jongyoon Han, who is a researcher in electrical engineering and computer science and biological engineering.

The first authors of Han''s paper are: Junghyo Yoon, a RLE research scientist, Hyukjin J. Kwon, a former postdoc at Northeastern University, and Eric Brack of the United States Army Combat Capabilities Development Command.

Filter-free technology

Portable desalination units, which are typically available in commercial use, require high-pressure pumps to push water through filters, which are extremely difficult to miniaturize, without compromising the energy-efficiency of the gadget, according to Yoon.

The ICP process is based on an electrical field to membranes located above and below a channel of water. The membranes repel positively or negatively charged particles, including salt molecules, bacteria, and viruses as they flow past. The charged particles are then funneled into a second stream of water that is eventually discharged.

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

ICP does not always remove all the salts floating in the middle of the channel. So, the researchers implemented a second process, known as electrodialysis, to remove remaining salt ions.

Yoon and Kang drew into machine learning to develop an 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 and three in the second phase, followed by a single electrodialysis process. This reduced energy usage while ensuring the process remains self-clean.

If some charged particles are trapped on the ion exchange membrane, then we just reverse the polarity of the electric field and the charged particles can be quickly removed, according to Yoon.

The researchers designed the device for nonexperts, and with just one touch to initiate the automatic desalination and purification process. Once the salinity level and the number of particles have decreased to specific thresholds, the device automatically notifys the user that the water is drinkable.

Researchers created a smartphone app that can control the device wirelessly and provide real-time insights on power consumption and water salinity.

Beach tests

At Bostons Carson Beach, they made lab experiments using water with different salinity and turbidity levels.

Yoon and Kwon set the box near the shore and tossed the feed tube into the water in about half an hour. The device had filled a plastic drinking cup with clear, drinkable water.

It was successful even in its first run, which was quite exciting and surprising. I think the main reason we were successful is the accumulation of all of these little advances we made along the way.

The water that produced it exceeded World Health Organization quality standards, and the facility reduced the amount of suspended solids by at least a factor of 10. Their prototype, which consists of drinking water at a rate of 0.3 liters per hour, requires only 20 watts of electricity per liter.

Right now, we are focusing on increasing the production rate, according to Yoon.

According to Han, one of the greatest challenges of designing a portable system was creating an intuitive device that might be used by anyone.

Yoon wants to make the device more user-friendly and improve its energy efficiency and production rate through a startup that he intends to initiate to commercialize the technology.

Han wants to apply the lessons he has learned over the past decade to water-quality issues that transcend desalination, such as rapid detection of contaminants in drinking water.

This is certainly a great task, and I am very impressed by the progress we have made so far, but there is still a lot of work to be done, according to the author.

While the development of portable devices with electro-membrane processes is an innovative and significant step in off-grid, small-scale desalination, toxic chemicals may significantly increase maintenance requirements and energy costs, according to Nidal Hilal, a professor of engineering and director of the New York University Water research center.

He adds that expensive materials are also being used. It would be interesting to see similar systems that include low-cost materials.

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