Production Of Electricity During Wastewater Treatment Using A Single Chamber Microbial Fuel Cell PDF

Environ. Sci. Technol. 2004, 38, 2281-2285 but these technologies are generally only suitable for high- Production of Electricity during strength wastewater streams typically produced by ind...

Environ. Sci. Technol. 2004, 38, 2281-2285 but these technologies are generally only suitable for high- Production of Electricity during strength wastewater streams typically produced by industry. Wastewater Treatment Using a In addition, conventional anaerobic treatment produces methane gas, which if released, can contribute to global Single Chamber Microbial Fuel Cell warming. One method has been advocated to reduce wastewater treatment costs, finding ways to produce useful products from wastewater treatment (2). However, effective HONG LIU,† methods for generating products other than methane from RAMANATHAN RAMNARAYANAN,‡ AND wastewater have not yet been shown to be feasible. B R U C E E. L O G A N * ,†,§ It has been known for several years that bacteria can be Department of Civil and Environmental Engineering, used to generate electricity that can be harvested in microbial Department of Chemistry, and The Penn State Hydrogen Energy (H2E) Center, The Pennsylvania State University, fuel cells (MFCs) (3). In a MFC, bacteria that oxidize a University Park, Pennsylvania substrate are kept physically separated from the electron acceptor by a proton exchange membrane. Electrons pass from the bacteria to the electrode (anode) in the same chamber and then via a circuit to the cathode where they Microbial fuel cells (MFCs) have been used to produce combine with protons and oxygen to form water. The electricity from different compounds, including acetate, difference in the potential coupled to electron flow produces electricity in this fuel cell. Electrons generated by bacteria lactate, and glucose. We demonstrate here that it is also through the anaerobic oxidation of organic matter (by possible to produce electricity in a MFC from domestic nonfermentative reactions) are passed to respiratory enzymes wastewater, while at the same time accomplishing biological normally bound to the inner cell membrane. Artificial electron wastewater treatment (removal of chemical oxygen carriers (mediators), such as neutral red or anthraquinone- demand; COD). Tests were conducted using a single 2,6-disulfonate (AQDS), or high concentrations of humic acids chamber microbial fuel cell (SCMFC) containing eight can be used to carry electrons from inside the cell to an graphite electrodes (anodes) and a single air cathode. The external electrode (3-6). However, the need for high system was operated under continuous flow conditions concentrations of electron carriers, many of which are toxic with primary clarifier effluent obtained from a local wastewater chemicals, is thought to make electricity generation on a treatment plant. The prototype SCMFC reactor generated large scale in a mediator-type fuel cell impractical. Some bacteria, such as Shewanella putrefaciens, however, can electrical power (maximum of 26 mW m-2) while removing produce their own mediators (soluble quinones) (7) that can up to 80% of the COD of the wastewater. Power output eliminate the need to add mediators. was proportional to the hydraulic retention time over a range It was only recently discovered that the respiratory of 3-33 h and to the influent wastewater strength over enzymes of certain iron-reducing bacteria span their outer a range of 50-220 mg/L of COD. Current generation was membrane allowing direct transfer of electrons to external controlled primarily by the efficiency of the cathode. Optimal metals such as Fe (III) or Mn (IV) (8-10). The attachment of cathode performance was obtained by allowing passive these iron-reducing bacteria to carbon electrodes results in air flow rather than forced air flow (4.5-5.5 L/min). The electron transfer to the anode, with oxygen reduction at the Coulombic efficiency of the system, based on COD removal cathode (11). The measured equilibrium potentials (-0.17 and current generation, was