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Low-Energy Water Filtration
A new membrane-free water-purification system uses small amounts of energy.
Lee Bruno, May 12, 2008, Technology Review
Excerpts from the article:
Most water-filtration technologies require a lot of energy to push water through membranes that eventually become fouled and need to be replaced. Both factors make water filtration costly for most applications.
Now researchers at Palo Alto Research Center (PARC) have been able to overcome those challenges by incorporating scientific insights from the physics of toner particle movements into a low-energy water-filtration device that doesn't use membranes.
That's all good news for the looming specter of filtering brackish drinking water that threatens much of the developing world and even some water-stressed areas in developed countries. In the past, however, the economics have been the stumbling block for creating affordable water-treatment systems...
PARC researchers call their device the spiral concentrator... As water is pumped through one end of the device, particles in the water are pressed up against the walls of the tubing. Particles as small as one micron in size are separated out by centrifugal force and shunted away from the clean water via diverging forks in the spiral concentrator.
The advantage of this approach is that it doesn't require as much energy as it would to push contaminated water through a membrane...
The PARC innovation sprang from an earlier contract research project with the U.S. Army...
The PARC researchers have lots of experience with studying the physics of particles. Toner in copy machines is made up of miniature, electron-charged particles...
The purifier requires a constant flow rate of water so that the movements of the particles conform to predicted patterns...
However, because the spin concentrator can separate particles no smaller than one micron in size, it can't remove bacteria. Scott Elrod, manager of the hardware systems laboratory at PARC, says that smaller particles could be separated out by...
Elrod says that in the next two months, the researchers expect to...
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