Development and Evaluation of Microbial Fuel Cell by Using Light as Energy

• Main Authors: Yen-Chun Lai, 賴彥錞
• Other Authors: Chun-Hsiung Hung
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/23951632366712079686

博士 === 國立中興大學 === 環境工程學系所 === 105 === Microbial fuel cells (MFCs) is a novel energy technology, which could treat wastewater and recover energy from organic compounds simultaneously. Comparing with traditional wastewater treatment processes, MFCs has lower energy demand and could produce extra energy for other wastewater treatment units. Therefore, it had become more popular in academic research recently. After that, photomicrobial fuel cells (PMFCs) and microbial solar cells (MSCs) were developed by combining light illumination and MFCs. It has been proved that the light-related MFCs could capture light energy and convert it into electricity. The aim of this study is using purple non-sulfur bacteria (PNSB), which are capable of capturing light energy and storing energy as a polyphosphate, as the exoelectrogen in PMFCs and investigating its potential of power generation. On the other side, cyanobacteria were applied to produce electricity without extra organic compounds addition. The performance of MSCs system would be evaluated under sunlight illumination condition. To start with, several PNSB strains were selected for investigating their potential of power generation and the result was similar. The correlation between power generation and light illumination was showed in this research. Also, many factors that might affect system performance were optimized for increasing power generation. The system performance was successfully raised up about twice. In addition, using molecular biotechnology for pufM, ppk, and ppx gene expression of PNSB is feasible. This study attempts to use the monitoring tool and water quality analysis for finding the way of releasing the energy in form of polyphosphate and PHB that stored in cells. The result showed that bacteria could release the energy when they were under low-carbon or low-phosphate environment. In the following study, cyanobacteria samples collected from different sources were selected for power generation. Among them, an appropriate cyanobacteria sample was chosen for the following experiments. After that, system performance under different operation conditions was tested. Results showed that the degree of power generation correlates with cyanobacteria biomass. Excess cyanobacteria biomass might cover light illumination and lead to lower performance. The optimum pH for power generation of MSCs system is neutral. Too much acid or alkaline would reduce system performance. MSCs system produced electricity when light intensity below 2,000 lx (6,000 mW/m2), but had less power output under excess light illumination. Furthermore, dissolved oxygen is an important factor that strongly affected system performance. Adding 3% Na2SO3 enable the system to produce electricity for at least three weeks. Finally, PNSB and cyanobacteria were used as exoelectrogen and oxygen supplier in dual-chambered MFCs. The performance of this system was evaluated and compared with that of system inoculated with anaerobic sludge and single-chambered system. Results showed that dual-chambered system had lower power output, which was resulted from the high internal resistance of proton exchange membrane and the diffusion of oxygen from cathodic chamber to anodic chamber. On the other hand, the performance of system inoculated with anaerobic sludge was better than that of system inoculated with PNSB. According to electrochemical analysis, the electron transfer resistance of these two systems was different. This study successfully established two different mechanism MFCs systems and the evaluation method. The major internal resistance of both systems used in this study was electron transfer resistance. Therefore, system performance could be improved by increasing electron transfer efficiency.