Thursday, April 15, 2010

New Microbial Bioreactors Produce Power and Clean Water


Researchers at University of Wisconsin Madison aim to revolutionise water purification by turning the process into a method of "power generation" instead of a massive consumer of electrical power. Their research into the esoteric field of "microbial fuel cells" is yet another important step in the quest for bioenergy.
Research for many water scientists involves a frustrating paradox: Water purification requires prodigious amounts of electricity, while utilities guzzle huge volumes of water to generate electricity.

...The bioreactors that crowd [Zhen]He's labs are built around a phenomenon that was established 100 years ago in Britain, but that scientists all but ignored until recent years. As bacteria break down organic materials, such as wastewater contaminants, the process emits a stream of electrons that can be captured with a pair of simple electrodes to generate electricity.

He's systems ideally will perform three functions at once:

• Purify wastewater using bacteria.

• Produce electricity.

• Desalinate a separate supply of seawater in the same three-chamber bioreactors.

"This is not a perpetual motion machine. The science is proven. It's just taking energy that's untapped and using it," said David Drew, an engineer in the Madison office of Gannett Fleming.

...Classic microbial fuel cells have two chambers. And like a battery, one side has a positive electrode and the other a negative. One side is filled with bacteria and wastewater, which triggers the circuit.

The big innovation for He and Drew was the addition of a third chamber that holds salty seawater. Salt molecules, or sodium chloride, dissolve naturally in water. Permeable membranes separate the third chamber from the other two, allowing positively charged sodium atoms to migrate toward the electrode in one chamber while negatively charged chloride particles seep into the second. That removes the salt, molecule by molecule - at least in the lab.

So far, it appears unlikely that the system can remove every last trace of salt from water. But at the very least, He said his system could create a pre-desalination process that removes most of the salt and reduces the energy needed to strip out the rest. _JSOnline

In other microbial energy news, Purdue and Iowa State University researchers are busy tweaking the genes of algae to better produce fuels such as diesel and gasoline.

Stanford research aimed at harvesting electricity from algae

Programming viruses to split H2O into H2 and O2.

Microbial fuel cells, microbial fuels, microbial production of chemicals, cosmetics, nutraceuticals, animal feeds etc, and microbial water purification -- all of these relatively new uses of microbes promise to alter the balance of fuel production within the next 20 to 30 years.

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