March 2004

E-Mail This Article Printer-Friendly Version Dr. Bruce Logan and Dr. Hong Liu work with their microbial fuel cell. Photo by Greg Grieco, Penn State.

UNIVERSITY PARK, PA -A team of three environmental engineers at Penn State here have demonstrated a double-duty microbial fuel cell (MFC) that cleans wastewater flushing down the drain while at the same time generating electricity.

The power output so far is tiny - 10-50 milliwatt per square meter of electrode surface - but at the same time it removes up to 78% of the effluent's organic matter, as measured by biochemical oxygen demand, reports a Penn State release.

Bruce E. Logan, a professor of environmental engineering and the project's director, says microbial fuel cells "may represent a completely new approach to wastewater treatment. If power generation in these systems can be increased, MFC technology may provide a new method to offset wastewater treatment plant operating costs, making advanced wastewater treatment more affordable for both developing and industrial nations."

The Penn State device consists of a tube about six in. long and 2.5 in. in diameter. In it are eight graphite anodes, the negative electrode of a fuel cell, with about 36 square in. of surface area to which the bacteria can adhere and pass electrons to. The cathode is a carbon/platinum catalyst PEM membrane fused to a plastic support tube.

Unlike other microbial fuel cells where, according to Logan, various kinds of bacteria are typically added to the system, here only the naturally occurring wastewater bacteria drive the process.

First Demonstration Ever

Logan says this is the first demonstration ever that these organisms, skimmed from the settling pond of a treatment plant, can directly produce electricity. These organic fuel cells work through the action of bacteria which can pass electrons to the anodes. From there, the electrons flow to the positive cathode as electric current where they combine with hydrogen ions (protons) and oxygen to form water. Additionally, an oxidizing reaction occurs in the bacterial cell's interior that lowers the biochemical oxygen demand which in turn cleans the water.

The project is described in a on-line paper by Logan and Dr. Hong Liu, a postdoctoral researcher, and Ramanathan Ramnarayanan, a doctoral candidate, "Production of Electricity During Wastewater Treatment Using an Single Chamber Microbial Fuel Cell." It is scheduled for future publication in the "Environmental Science and Technology" journal. Contacts: Dr. Logan, 814/863-7908, blogan@psu.edu; Penn State media office, Barbara Hale or Vicki Fong, 814/865-9481, bah@psu.edu, vfong@psu.edu.