Transcript
In many places there is plenty of seawater but a serious shortage of drinkable water. To address that problem, MIT researchers have developed a portable desalination unit that generates clear, clean drinking water without the need for filters or high-pressure pumps. The suitcase-sized device requires less power to operate than a cell phone charger and operates with the push of one button.
Unlike existing portable desalination units that require water to pass through filters, this device utilizes electrical power to remove particles from drinking water. Eliminating the need for replacement filters greatly reduces the long-term maintenance requirements. This enables 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 soldiers carrying out long-term military operations.
This new system is the culmination of a 10- year investigation into the physics behind desalination processes. That research was recently documented in the journal Environmental Science and Technology. Until now, commercially available portable desalination units required high-pressure pumps to push water through filters. And these proved very difficult to miniaturize without compromising the energy-efficiency of the device.
On the contrary, the MIT unit relies on a technique called ion concentration polarization (or ICP), which was pioneered by the MIT researchers more than 10 years ago. Rather than filtering water, the ICP process applies an electrical field to membranes placed 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 funneled into a second stream of water that is eventually discharged. Notably, ICP does not always remove all the salts floating in the middle of the channel.
So, the researchers incorporated a second process, known as electrodialysis, to remove remaining salt ions. The researchers shrunk and stacked the ICP and electrodialysis modules to improve their energy efficiency and enable them to fit inside a portable device. And they also created a smartphone app to control the unit wirelessly and report real-time data on power consumption and water salinity. Once the salinity level and the number of particles decrease to specific thresholds, the device notifies the user that the water is drinkable.
The prototype generates drinking water which exceeds World Health Organization quality guidelines at a rate of one liters every 3 hours and requires only 20 watt-hours of electricity per liter. Right now, the MIT teams is involved in scaling up the production rate, while working to design a similar system with lower-cost materials.
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