With no fuss, a portable desalination unit delivers drinking water from seawater

With no fuss, a portable desalination unit delivers drinking water from seawater ...

Researchers at MIT have developed a portable desalination unit, which measures less than 10 kilograms, capable of extracting particles and salts to produce drinking water.

A suitcase-sized device, which requires less power to operate than a cell phone charger, can be powered by 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 operates with the push of one button.

This device, compared to other portable desalination units that require water to pass through filters, utilizes electrical power to remove particles from drinking water. The long-term maintenance limitations are greatly reduced.

This may allow the unit to be deployed in remote and resource-limited areas, such as communities on small islands or aboard seafaring cargo ships. It may also be used to assist refugees in disaster situations or by military personnel undertaking long-term military operations.

I and my group have embarked on a 10-year journey that we explored for years, but putting all of them into a box, building a system, and manifesting it in the ocean, according to Jongyoon Han, a senior author.

First author of Han''s book is Junghyo Yoon, a research scientist in RLE; Hyukjin J. Kwon, a former postdoc at Northeastern University; and Eric Brack of the United States Army Combat Capabilities Development Command (DEVCOM). The research has been published online in Environmental Science and Technology.

Filter-free technology

Portable desalination units are usually staffed with high-pressure pumps to push water through filters, which are quite difficult to miniaturize without compromising the energy-efficiency of the equipment, according to Yoon.

Instead, their company is built on a technique called ion concentration polarization (ICP), which was established by the Hans group more than ten years ago. Rather than filter water, the ICP process involves an electrical field to membranes located above and below a channel of water. As they repel positively or negatively charged particles, including salt molecules, bacteria, and viruses. The charged particles are then funneled into a second stream of water that is eventually discharged.

The process removes both dissipate and suspended solids, allowing clean water to pass through the channel. Because it only requires a low-pressure pump, ICP reduces energy usage than other methods.

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

Yoon and Kang used machine learning to select 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 phase then through three in the second stage, followed by a single electrodialysis process. This minimized energy usage while ensuring the process remains self-clean.

Although some charged particles may be captured on the ion exchange membrane, if they become trapped, we only reverse the polarity of the electric field and the charged particles can be easily removed, according to Yoon.

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

The researchers have developed a smartphone app that can be used wirelessly to control the unit and disclose real-time information on power consumption and water salinity.

Beach tests

At Bostons Carson Beach, they performed 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 the small advancements we made along the way, according to Han.

The water that produced it exceeded World Health Organization quality recommendations, reducing the amount of suspended solids by at least a factor of 10. Their system, which combines drinking water with 0.3 liters per hour, requires only 20 watts of power per liter.

According to Yoon, we are working on an increase in research in order to avert that production rate.

According to Han, one of the biggest challenges of designing the portable system was designing an intuitive system that could 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 launch to commercialize the technology.

Han, who works in the lab, wants to use his experiences from the past decade to water-quality issues that transcend desalination, such as rapidly discovering contaminants in drinking water.

This is truly a fun project, and I am grateful for all 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 mobile equipment with electro-membrane elements is an original and exciting step in off-grid, small-scale desalination, the effects of fouling, especially if the water has high turbidity, might 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.

A further limitation is the use of expensive materials, according to the author. It would be helpful to see similar structures with low-cost materials in place.

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