MIT researchers have developed a portable desalination tool, which measures less than 10 kilograms, and which can remove particles and salts to produce drinking water.
The suitcase-sized device, which requires less power to operate than a cell phone charger, can be further powered by a small, portable solar panel, which can be purchased online for around $50. It automatically produces 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, similar to other portable desalination units that require water to pass through filters, uses electrical power to remove contaminants from drinking water. The elimination of the need for replacement filters greatly reduces the long-term maintenance concerns.
This may enable the unit to be deployed in remote and heavy resource-limited areas, such as communities on small islands or aboard seafaring cargo ships. It may also be used to assist refugees who have not experienced natural disasters or by military deployments.
This is the culmination of a 10-year journey that I and my group have ever completed. We worked for years on the physics behind individual desalination processes, but then putting all of them into a box, and building a system, and testing it in the ocean, which was a truly beneficial and rewarding experience for me, according to senior author Jongyoon Han, who is a professor of electrical engineering and computer science and biological engineering.
Junghyo Yoon, a research scientist at RLE, Hyukjin J. Kwon, a former postdoc at Northeastern University, and Eric Brack of the United States Army Combat Capabilities Development Command (DEVCOM), join Han on the paper.
Portable desalination units that are commercially available typically require high-pressure pumps to push water through filters, which are very difficult to miniaturize without compromising the energy-efficiency of the devices, according to Yoon.
The ICP process is mostly based on a technique called ion concentration polarization (ICP), which was developed by the Hans group more than ten years ago. Rather than filtering water, membranes are applied an electrical field to the fluids, which forms, which repel positively or negatively charged particles, including salt molecules, bacteria, and viruses as they travel past. The charged particles are then placed into a second stream of water that is eventually discharged.
The process is divided into two parts, which allows clean water to pass through the channel. Since it only requires a low-pressure pump, ICP uses less energy than other techniques.
However, ICP does not always remove all the salts floating in the middle of the channel. So, the researchers introduced a second method, called electrodialysis, to remove remaining salt ions.
Yoon and Kang drew on machine learning to design an ideal combination of ICP and electrodialysis modules. The ideal arrangement includes a two-stage ICP process, with water flowing through six modules in the first stage, three in the second stage, followed by a single electrodialysis process. This reduced energy usage while ensuring the process remains self-clean.
While certain charged particles might be removed on the ion exchange membrane, if they become trapped, we just reverse the polarity of the electric field and the charged particles may be easily removed, according to Yoon.
The researchers designed the ICP and electrodialysis modules for nonexperts, with just one touch to begin the automatic desalination and purification process. Once the salinity level and the number of particles have dropped to specific thresholds, the device informs the user that the water is drinking.
Researchers designed a smartphone app that can operate the unit wirelessly and provide real-time insights on power consumption and water salinity.
At Bostons Carson Beach, they fielded the device after performing laboratory experiments using water with different salinity and turbidity levels.
Yoon and Kwon sat near the shore and wrapped the feed tube in 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. However, I think the main reason we were successful is the accumulation of all of the little advances we made along the way.
The water resulting from the world health organization exceeded World Health Organization quality guidelines, and the company 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, is capable of generating only 20 watts of power per liter.
According to Yoon, we are working on a larger amount of research to increase that production rate right now.
One of the most difficult aspects of designing a portable system was designing an intuitive device that could be used by anyone, according to Han.
Yoon hopes to increase the device''s performance and output rate through a startup that he intends to launch to commercialize the technology.
Han has been working on a project to provide water quality improvements beyond desalination, such as rapidly detecting contaminants in drinking water.
This is really a fantastic project, and I am very pleased of the progress we have made so far, although there is still a lot to do, according to the author.
While the development of portable equipment using electro-membrane processes is an original and exciting approach in off-grid, small-scale de-salination, 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.
He adds that the use of expensive materials might be a problem. It might be interesting to see similar systems with low-cost materials in place.