March 5, 2012
New Device Can Turn Wastewater Into Electricity
Researchers from Penn State University claim that they have developed a prototype device that can use wastewater to create electricity, essentially transforming treatment stations into power plans.
Lead researcher and engineering professor Bruce E. Logan and his colleagues have combined microbial fuel cells (which can use wastewater and naturally occurring bacteria to generate electricity) and reverse electrodialysis (which creates power from the differences in salt concentration between freshwater and saltwater) in order to create what they call a microbial reverse-electrodialysis cell (MRC), the university said in a Thursday press release.
MSNBC.com (http://www.futureoftech.msnbc.msn.com/technology/futureoftech/electricity-wastewater-gets-salty-boost-280300) Tech Reporter John Roach wrote that the device, which according to Logan's team can produce 0.94 kilowatt hours of electricity per kilogram of wastewater-based organic material, "could lead to wastewater treatment plants that generate electricity, instead of consuming it."
Roach adds that the Penn State team believes that wastewater could potentially produce as much power as 15 to 20 nuclear power facilities. Their findings were published on March 1 in the journal Science Express.
Logan told Damian Carrington of the Guardian that their device treated the organic matter in the wastewater "much faster" than traditional treatment and pumping stations, which also require a "substantial" amount of energy to keep running. He added that the team is hoping to "optimize" their power-generation, and that he believed that his team's work could help solve the clean water crisis affecting some parts of the world.
"There are 2 billion people in the world who need sanitation, including 1 billion who need access to clean water," Logan told Carrington. "If you go into a country and give them a waste treatment system -- the World Bank and others have done this -- they do not keep it going, as it needs power and maintenance. It is a drain on the community. But if you can also provide electricity for lighting, or charging mobile phones, that's a game-changer."
According to a March 1 article by Nature's Duncan Graham-Rowe, the MRC system takes a reverse electrodialysis or RED stack comprised of alternating ion exchange membranes and sandwiches them between a pair of microbial fuel cell or MFC chambers where one would normally find the proton-exchange membrane. While the fluids from each system are separated and working independently, the stacks increase the MFC's current while the voltage from its electrodes makes it possible for the RED stack to remain functional with fewer membrane pairs.
"A crucial part of making this work is the use of an ammonium bicarbonate solution in the RED stack instead of sea water. This raises the power density, and the ammonium bicarbonate can be regenerated within the stack, making the RED stack a closed system. The team shows that this configuration can achieve maximum power densities of 3 watts per meter squared, much higher than either technology can achieve on its own," Graham-Rowe added.
Logan's team isn't the only one experimenting with such technology, according to BBC News Science and Health Reporter Neil Bowdler. Dutch scientists have reportedly been trying to find some way of creating renewable power sources along the coastline of the Netherlands, where fresh and salt water meet. Likewise, a company in Norway is also working on a similar device that also utilizes both salt and fresh water, he added.
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