The Pennsylvania State University The Graduate School College of Engineering SHEWANELLA ONEIDENSIS MR-1 COMPARED TO MIXED CULTURES FOR ELECTRICITY PRODUCTION IN FOUR DIFFERENT MICROBIAL FUEL CELL CONFIGURATIONS A Thesis in Environmental Engineering by Valerie J. Watson © 2009 Valerie Watson Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Science May 2009 The thesis of Valerie J. Watson was reviewed and approved* by the following: Bruce E. Logan Kappe Professor of Environmental Engineering Thesis Advisor John M. Regan Associate Professor of Environmental Engineering Rachel Brennan Assistant Professor of Environmental Engineering Peggy Johnson Professor of Civil Engineering Head of the Department of Civil and Environmental Engineering *Signatures are on file in the Graduate School ii ABSTRACT Bacteria can produce power in microbial fuel cells (MFCs) by converting organic matter into electricity. As an added benefit, the organic matter used in the system can come from waste streams that would need to be treated, often by energy consuming processes. There are several studies investigating power production from pure culture communities as well as studies using mixed cultures for power production, but very few studies actually comparing power production from both mixed culture and pure culture communities. The dissimilatory metal reducing bacterium (DMRB) Shewanella oneidensis MR-1 has been used as a model bacterium in MFC studies, but there may be a bacterium (or consortia of bacteria) that is better suited for power production in MFCs. In this study, power densities from undefined mixed cultures obtained from a wastewater treatment facility, as well as from a pure culture of the facultative anaerobe S. oneidensis MR-1, were compared in cube shaped, 1-bottle, 2-bottle, and 3-bottle batch-fed MFC reactor configurations. Results show that the mixed culture produced 68 to 480% more power than S. oneidensis MR-1 in MFCs. The mixed culture produced the maximum power density of 858±9 mW m-2, while the MR-1 culture produced a maximum of 332±21 mW m-2 in a 1-bottle MFC. The difference in power production was the result of the decreased internal resistance in the mixed culture MFC compared to the internal resistance obtained with the MR-1 anode community. Oxidation-reduction potentials (ORP) were measured to help analyze the environmental conditions within the MFCs during power production. The results show that the environment that the bacteria are subjected to in the anode chamber can fluctuate from a reductive to an iii oxidative environment during the batch cycle. Power production decreased as the redox environment became more positive at the end of each cycle. However, the mixed culture MFCs produced more power than the MR-1 MFCs even though the redox environment was less negative. Considering this significant difference in power production as well as the limitations of substrate oxidation encountered by MR-1, there may be microorganisms that are more important for power production than S. oneidensis MR-1. iv TABLE OF CONTENTS LIST OF FIGURES ..................................................................................................... vii LIST OF TABLES ....................................................................................................... viii ACKNOWLEDGEMENTS ......................................................................................... ix CHAPTER 1 INTRODUCTION ................................................................................. 1 CHAPTER 2 LITERATURE REVIEW ...................................................................... 5 2.1 MFC Operation and Architecture............................................................... 5 2.2 MFC Anodic Bacteria................................................................................. 9 2.3 Oxidation-Reduction Potential (ORP)........................................................ 13 CHAPTER 3 MATERIALS AND METHODS........................................................... 15 3.1 Medium and Inoculum .............................................................................. 15 3.2 Reactor Construction ................................................................................. 15 3.3 Startup and Operation ................................................................................ 18 3.4 Analyses...................................................................................................... 19 3.4.1 Polarization and Power Production....................................................... 19 3.4.2 Internal Resistance ............................................................................... 20 3.4.3 Coulombic Efficiency........................................................................... 20 3.4.4 Oxidation-Reduction Potential ............................................................. 20 CHAPTER 4 RESULTS............................................................................................... 22 4.1 Anode Enrichment ................................................................................... 22 v 4.2 Polarization, Power Density, and Internal Resistance ............................ 25 4.3 Coulombic Efficiency.............................................................................. 28 4.4 Oxidation-Reduction Potential ............................................................... 30 CHAPTER 5 DISCUSSION....................................................................................... 33 5.1 Polarization, Power Density, and Internal Resistance............................. 33 5.2 Oxidation-Reduction Potential ................................................................ 37 5.3 Voltage Production Cycle........................................................................ 38 5.4 Coulombic Efficiency.............................................................................. 40 CHAPTER 6 CONCLUSIONS AND RECOMMENDATIONS FOR FUTURE RESEARCH................................................................................................................. 42 APPENDIX A GROWTH MEDIUM AND ELECTROLYTE DETAILS.................. 43 APPENDIX B COMPARISON OF SHEWANELLA MFC PERFORMANCE REPORTED IN LITERATURE................................................................................... 45 APPENDIX C GAS CHROMATOGRAPY ANALYSIS OF MFC EFFLUENT........ 48 APPENDIX D ORP VARIATIONS OVER A COMPLETE FEED CYCLE.............. 49 REFERENCES.............................................................................................................. 50 vi LIST OF FIGURES Figure 1.1 Diagram of the operation of a single chamber MFC............................................... 3 Figure 3.1 MFC reactor configuration (A)1-bottle, (B) 2-bottle, (C) 3-bottle, and (D) cubic....................................................................................................................... 16 Figure 3.2 Diagrams of electrode spacing and anode orientation for A) 1-bottle and B) cubic MFCs...................................................................................................................... 18 Figure 4.1 Cell Voltage measurements in A) Cubic, B) 1-Bottle, C) 2-Bottle, and D) 3-Bottle MFCs..................................................................................................................... 24 Figure 4.2 Power density and Polarization curves for Shewanella oneidensis MR-1 ( ) versus a mixed culture ( ) in (A, C) Cubic MFCs and (B, D) 1-Bottle MFCs................... 26 Figure 4.3 Power density and Polarization curves for Shewanella oneidensis MR-1 ( ) versus a mixed culture ( ) in (A, C) 2-Bottle MFCs and (B, D) 3-Bottle MFCs............... 27 Figure 4.4 Internal resistance from polarization curves for Shewanella oneidensis MR-1 ( ) versus a mixed culture ( ) in (A) Cubic, (B) 1-Bottle, (C) 2-Bottle, and (D) 3-Bottle MFCs..................................................................................................................... 29 Figure 4.5 Coulombic Efficiencies for Shewanella oneidensis MR-1 (red) versus a mixed culture (blue) in cubic, 1-bottle, 2-bottle, and 3-bottle MFCs........................................... 30 Figure 4.6 Oxidation-Reduction potential versus measured cell potential in cubic, 1-bottle, 2- bottle, and 3-bottle MFCs inoculated with (A) Shewanella oneidensis MR-1 and (B) a mixed culture measured over multiple cycles............................................... 32 Figure 5.1(A) Power generation is inversely related with the measured internal resistance, (B) power related to the inverse of ohmic resistance, and (C) power as a function of the inverse of electrode spacing for MR-1 ( ) and mixed ( ) culture MFCs............. 34 Figure 5.2 Ohmic resistance versus electrode spacing in MFCs.............................................. 36 Figure 5.3 Relationships between internal and ohmic resistance for MR-1 ( ) and mixed ( ) culture MFCs.......................................................................................................... 37 Figure D-1 ORP values and cell potential over one cycle in (A) 2-bottle and (B) 3-bottle MR-1 MFCs....................................................................................................................... 49 vii LIST OF TABLES Table 4.1 Ohmic resistance (from EIS at OCV), internal resistance (from polarization), and power production for each MFC configuration........................................................ 28 Table 4.2 Average redox potentials in mixed and