Sustaining Future

Tuesday, November 20, 2007

Treat Water, Make Energy

I am advocating the use of "by-production management" instead of "waste management" because this will shift our focus of the way of utilising the "waste".

Here is a good example. A single-chamber fuel-cell which uses "waste-water" as its energy source.

The single-chambered microbial fuel cell is essentially a plexiglass cylinder about the size of a soda bottle. Inside are eight graphite anodes (or negative electrodes), upon which the bacteria attach, and a hollow central cathode (or positive electrode). Electrons flow along a circuit wired from the anode to the cathode.

A steady flow of wastewater pumped into the chamber feeds the bacteria. Bacterial digestion of the wastewater's organic matter unleashes electrons into the electrical circuit and positively charged hydrogen ions into the solution. Those ions reduce the solution's oxygen demand, a key goal of wastewater treatment. The hydrogen ions also pass through a proton-exchange membrane to reach the cathode. Meanwhile, a hollow tube within the cylinder contains the cathode, which is exposed to air. At the cathode, oxygen from the air, hydrogen ions coming through the membrane and the electrons coming down the circuit combine to create water.


The single-chamber design is important, he said, because it facilitates a "continuous flow-through system," a design consistent with existing treatment systems.

By introducing air passively through the tube within the cathode layer, this model also greatly reduces the need for more aggressive – and energy-demanding – aeration schemes to treat the wastewater. Thus, as it creates electricity, it also reduces the need for it.

This is turning a cost-center (treating waste water) into a profit-center. Even better is the size of the device. It can be installed at our home and let's us reduce our energy bill. WoW!



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