From Seawater to Drinking Water at the Push of a Button – With No Filters!

The user-friendly device, which weighs less than 10 kilograms and does not require the use of filters, can be powered by a small, portable solar panel. Photo credit: M. Scott Brauer

Researchers are building a portable desalination plant that produces clear, clean drinking water without filters or high-pressure pumps.

The device, which is about the size of a suitcase, needs less power to operate than a cell phone charger. It can also be driven by a small, portable solar panel, which can be purchased online for around $50. It automatically generates drinking water that exceeds World Health Organization (WHO) quality standards. The technology is packaged into a user-friendly device that runs with the push of a single button.

Unlike other portable desalination devices that require water to pass through filters, this unit utilizes electrical power to remove particles from drinking water. Eliminating the need for replacement filters significantly reduces the long-term maintenance requirements.

Two Stage Ion Concentration Polarization Process

The setup includes a two-stage ion concentration polarization (ICP) process, with water flowing through six modules in the first stage then through three in the second stage, followed by a single electrodialysis process Credit: M. Scott Brauer

This could enable the unit to be deployed in remote and severely resource-limited areas, such as communities on small islands or aboard seafaring cargo ships. It could also be used to aid refugees fleeing natural disasters or by soldiers carrying out long-term military operations.

“This is really 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 pushing all those advances into a box, building a system, and demonstrating it in the ocean, that was a really meaningful and rewarding experience for me,” says senior author Jongyoon Han, a professor of electrical engineering and computer science and of biological engineering, and a member of the Research Laboratory of Electronics (RLE).

Joining Han on the paper are first author Junghyo Yoon, a research scientist in RLE; Hyukjin J. Kwon, a former postdoc; SungKu Kang, a postdoc at Northeastern University; and Eric Brack of the U.S. Army Combat Capabilities Development Command (DEVCOM). The research has been published online in the journal Environmental Science and Technology.

Filter-free technology

Commercially available portable desalination units typically require high-pressure pumps to force water through filters, which are very difficult to miniaturize without sacrificing the unit’s energy efficiency, Yoon explains.

Instead, their unit relies on a technique called Polarization of the ion concentration (ICP), which was developed by Hans Gruppe more than 10 years ago. 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 flow past. The charged particles are directed into a second stream of water, which is eventually drained.

The process removes both dissolved and suspended solids, allowing clean water to flow through the channel. Because only one low-pressure pump is required, ICP uses less energy than other techniques.

Portable device from sea water to drinking water

The portable device does not require replacement filters, which significantly reduces long-term maintenance requirements. Photo credit: M. Scott Brauer

But ICP doesn’t always remove all the salts floating in the middle of the channel. Therefore, the researchers integrated a second process, called electrodialysis, to remove any remaining salt ions.

Yoon and Kang used machine learning to find the ideal combination of ICP and electrodialysis modules. The optimal setup involves a two-stage ICP process, with water flowing through six modules in the first stage and three modules in the second stage, followed by a single electrodialysis process. This minimizes energy consumption while ensuring that the process remains self-cleaning.

“While it’s true that some charged particles could be trapped on the ion exchange membrane, if they are trapped, we simply reverse the polarity of the electric field and the charged particles can be easily removed,” explains Yoon.

They shrunk and stacked the ICP and electrodialysis modules to improve their energy efficiency and allow them to fit into a portable device. The researchers designed the device for the layman, with just one button to start the automatic desalination and cleaning process. Once the salinity and particle counts drop to certain thresholds, the device notifies the user that the water is safe to drink.

Researchers also created a smartphone app that can wirelessly control the device and report real-time data on electricity usage and water salinity.

beach tests

After conducting lab experiments with water of varying salinity and turbidity (turbidity), they tested the device in the field at Boston’s Carson Beach.

Yoon and Kwon parked the box near the bank and threw the hose into the water. In about half an hour, the device had filled a plastic drinking cup with clear, drinkable water.

Jongyoon Han and Junghyo Yoon

MIT researchers have developed a portable desalination unit that can automatically remove particles and salts simultaneously to produce drinking water. “This is truly the culmination of a 10-year journey that my group and I have been on,” says lead author Jongyoon Han, right, pictured with Junghyo Yoon seated. Photo credit: M. Scott Brauer

“It was successful in the first run, which was quite exciting and surprising. But I think the main reason for our success is the accumulation of all these small steps that we’ve made along the way,” says Han.

The resulting water exceeded World Health Organization quality guidelines, and the unit reduced the amount of suspended solids by at least a factor of 10. Their prototype produces drinking water at a rate of 0.3 liters per hour and requires only 20 watts of power per liter.

“Right now, we’re pushing our research to increase that production rate,” says Yoon.

One of the biggest challenges in designing the wearable system was creating an intuitive device that anyone could use, says Han.

Yoon hopes to make the device more user-friendly and improve its energy efficiency and production rate through a startup he plans to create to commercialize the technology.

In the lab, Han wants to apply the lessons he’s learned over the past decade to water quality issues beyond desalination, such as: B. the rapid detection of impurities in drinking water.

“This is definitely an exciting project and I’m proud of the progress we’ve made so far, but there’s still work to be done,” he says.

For example, while the “development of portable electromembrane process systems is an original and exciting direction in small-scale off-grid desalination,” the effects of fouling, particularly when the water is high in turbidity, could significantly increase maintenance and energy costs, notes Nidal Hilal, Professor of Engineering and Director of[{” attribute=””>New York University Abu Dhabi Water research center, who was not involved with this research.

“Another limitation is the use of expensive materials,” he adds. “It would be interesting to see similar systems with low-cost materials in place.”

Reference: “Portable Seawater Desalination System for Generating Drinkable Water in Remote Locations” by Junghyo Yoon, Hyukjin J. Kwon, SungKu Kang, Eric Brack and Jongyoon Han, 14 April 2022, Environmental Science and Technology.
DOI: 10.1021/acs.est.1c08466

The research was funded, in part, by the DEVCOM Soldier Center, the Abdul Latif Jameel Water and Food Systems Lab (J-WAFS), the Experimental AI Postdoc Fellowship Program of Northeastern University, and the Roux AI Institute.

From Seawater to Drinking Water at the Push of a Button – With No Filters! Source link From Seawater to Drinking Water at the Push of a Button – With No Filters!

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