Bioenergy production from wastewater using bioelectrochemical cells and performance improvement

Abstract

The increasing oil price and energy demand combined with the general acceptance that man-made global warming is occurring commands the emergence of new energy solutions. Microbial fuel cell (MFC) technology can extract electric energy directly from wastewater, and is therefore a sustainable means of supplying energy to our electricity-based society. Several challenges are, however, facing us in that various limitations currently exist, such as the low generation of MFCs. Therefore, this study was conducted to overcome the problems of low power generation by reducing internal resistance and optimizing the operation parameters of MFCs treating actual wastewater. First, experiments were conducted to reduce internal resistance in the form of ohmic resistance and charge transfer resistance. Ohmic resistance could be decreased using feasible buffer solutions of phosphate and PIPES buffers. A suitable buffer should be selected considering conductivity and the buffer capacity to enhance power output. It was also found that biofilm when attached to the anode was significantly related to charge transfer resistance. Dense biofilm on the anode can enhance the charge transfer rates due to the complex development of a biofilm matrix that anchors the electrochemically active microorganisms together on the anode surface. Second, ammonia inhibition of electricity production in single-chamber MFCs was investigated in batch and continuous operations. For the first time, it was demonstrated that electricity generation in MFCs was inhibited by the total ammonia-N (TAN) concentration. Although TAN concentrations of over 1000 mg $NH_4^+$-N/L inhibited electricity generation in batch MFCs, stable electricity could be maintained with TAN concentrations as high as 3500 mg $NH_4^+$ -N/L under continuous operation due to bacterial adaptation to the high ammonia concentration. Third, continuous electricity generation from fermented wastewater was achieved using upflow granular sing...