Fuel cells: a replacement for wastewater activated sludge treatment?

Microbial fuel cells could produce electricity directly from wastewater and replace activated sludge and anaerobic digestion methods, researchers have claimed...

Microbial fuel cells could produce electricity directly from wastewater and replace activated sludge and anaerobic digestion methods, researchers have claimed.

Engineers at Oregon State University (OSU) have found that microbial fuel cells can produce electricity directly from wastewater, which they said will mean that wastewater treatment plants could eventually generate enough power to sell excess electricity.

OSU claimed the technology can now produce 10 to 50 more times the electricity, per volume, than most other approaches using microbial fuel cells, and 100 times more electricity than some.

Researchers said this could eventually change the way that wastewater is treated all over the world, replacing the widely used activated sludge process that has been in use for almost a century.

The findings have just been published in Energy and Environmental Science, a professional journal, in work funded by the National Science Foundation.

The technology cleans wastewater using a different approach than the aerobic bacteria. Bacteria oxidize the organic matter and, in the process, produce electrons that run from the anode to the cathode within the fuel cell, creating an electrical current.

OSU researchers reported several years ago on the promise of this technology but at that time the systems in use produced far less electrical power. With new concepts – reduced anode-cathode spacing, evolved microbes and new separator materials – the technology can now produce more than two kilowatts per cubic meter of liquid reactor volume, OSU claimed.

The system has been tested on a laboratory scale and OSU said the next stage is a pilot study, for which funding is being sought. A food processing plant has been suggested as a possible testing ground.

OSU said: “The system also works better than an alternative approach to creating electricity from wastewater, based on anaerobic digestion that produces methane. It treats the wastewater more effectively, and doesn’t have any of the environmental drawbacks of that technology, such as production of unwanted hydrogen sulfide or possible release of methane, a potent greenhouse gas.”

Once advances are made to reduce high initial costs, researchers estimated that the capital construction costs of this new technology should be comparable to that of the activated sludge systems now in widespread use today – and even less expensive when future sales of excess electricity are factored in.

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