New Technology Could Treat Wastewater

A new technology designed to run cars of the future also could revolutionize wastewater treatment, researchers announced on Jan. 18.

With slight adaptations, the "microbial fuel cell" technology systems could take about any biodegradeable organic matter and produce a useful product -- such as the electricity to help operate a waste treatment plant or hydrogen for fuel cells.

When used with sewage, another fringe benefit of the technology is that it also cleans the water by a completely different method than the traditional use of aerobic bacteria, opening the door for new generations of waste treatment plants that could produce much of the energy needed for their own operation.

"These systems would use oxidation to remove up to 80 percent of the pollutants in wastewater, and at the same time provide a substantial portion of the energy used to operate the treatment plants," said Hong Liu (http://bee.oregonstate.edu/Faculty/Liu/index.htm), an assistant professor of biological and ecological engineering in Oregon State University's (OSU) College of Engineering. "In the United States, about $25 billion a year is spent for domestic wastewater treatment, so major cost savings may be possible."

According to Liu, those possibilities will take further refinement of existing technology. But the concept has clearly been proven in laboratory experiments, she said. It's renewable, and efforts are under way to bring down costs, identify less expensive materials and improve operational efficiency.

It's been known that microbial fuel cells can be run from high-energy materials such as glucose, but is now clear that many organic waste materials may also work, including grass straw, wood pulp, and of course wastewater. Bacteria oxidize the organic matters and, in the process, produce electrons that travel from the anode to the cathode within the fuel cell, creating an electrical current.

As a new concept in sewage treatment, this approach eliminates the need to pump oxygen into a mixture of sewage and aerobic bacteria -- in one stroke eliminating almost half of the cost associated with a conventional sewage treatment plant, according to the researchers.

For hydrogen production, some of the latest studies outline a related process in the absence of oxygen that uses an electrical assist to greatly increase the efficiency of direct hydrogen production at the cathode of the reactor. This "bio-electrochemically assisted microbial reactor" also treats the wastewater at the same time -- just like in the approach used to create electricity -- but instead yields hydrogen as a useful end product and the ultimate power source for hydrogen fuel cells. And the approach is more cost-effective than existing technology to produce hydrogen, which uses large amounts of electricity.

"Some of the newest experiments indicate that for hydrogen production, we can increase the amount of potential hydrogen recovered from sewage from about 15 percent to about 70 percent," Liu said. "This completely anaerobic technology is very promising, but we still have improvements to make."

Additional information on biological and ecological engineering at OSU can be found at http://bee.oregonstate.edu.

This article originally appeared in the 01/01/2006 issue of Environmental Protection.

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