• Journal of Microbiology and Biotechnology
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• v.22 no.2
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• pp.270-273
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• 2012

These studies were conducted to determine the effects of various concentrations of ammonium and nitrate on current generation using dual-cathode microbial fuel cells (MFCs). Current generation was not affected by ammonium up to $51.8{\pm}0.0$ mg/l, whereas $103.5{\pm}0.0$ mg/l ammonium chloride reduced the current slightly. On the other hand, when $60.0{\pm}0.0$ and $123.3{\pm}0.1$ mg/l nitrate were supplied, the current was decreased from $10.23{\pm}0.07$ mA to $3.20{\pm}0.24$ and $0.20{\pm}0.01$ mA, respectively. Nitrate did not seem to serve as a fuel for current generation in these studies. At this time, COD and nitrate removal were increased except at $123{\pm}0.1$ mg ${NO_3}^-/l$. These results show that proper management of ammonium and nitrate is very important for increasing the current in a microbial fuel cell.

• Microbiology and Biotechnology Letters
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• v.40 no.4
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• pp.414-418
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• 2012

The quantity of research on microbial fuel cells has been rapidly increasing. Microbial fuel cells are unique in their ability to utilize microorganisms and to generate electricity from sewage, pig excrement, and other wastewaters which include organic matter. This system can directly produce electrical energy without an inefficient energy conversion step. However, with MFCs maximum power production is limited by several factors such as activation losses, ohmic losses, and mass transfer losses in cathodes. Therefore, electron acceptors such as nitrate and ferric ion in the cathodes were utilized to improve the cathode reaction rate because the cathode reaction is very important for electricity production. When 100 mM nitrate as an electron acceptor was fed into cathodes, the current in single-cathode and dual-cathode MFCs was noted as $3.24{\pm}0.06$ mA and $4.41{\pm}0.08$ mA, respectively. These values were similar to when air-saturated water was fed into the cathodes. One hundred mM nitrate as an electron acceptor in the cathode compartments did not affect an increase in current generation. However, when ferric ion was used as an electron acceptor the current increased by $6.90{\pm}0.36$ mA and $6.67{\pm}0.33$ mA, in the single-cathode and dual-cathode microbial fuel cells, respectively. These values, in single-cathode and dual-cathode microbial fuel cells, represent an increase of 67.1% and 17.6%, respectively. Furthermore, when supplied with ferric ion without air, the current was higher than that of only air-saturated water. In this study, we attempted to reveal an inexpensive and readily available electron acceptor which can replace platinum in cathodes to improve current generation by increasing the cathode reaction rate.

• Microbiology and Biotechnology Letters
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• v.39 no.4
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• pp.382-386
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• 2011

Microbial fuel cells (MFC), devices that use bacteria as a catalyst to generate electricity, can utilize a variety of organic wastes as electron donors. The current generated may differ depending on the organic matter concentrations used, when other conditions, such as oxidant supply, proton transfer, internal resistance and so on, are not limiting factors. In these studies, a single-cathode type MFC (SCMFC) and dual-cathode type MFC (DCMFC) were used to ascertain the current's improvement through an increase in the contact area between the anode and the cathode compartments, because the cathode reaction is one of the most serious limiting factors in an MFC. Also an MFC was conducted to explore whether an improvement in electricity generation resulted from oxidizing the carbon sources and nitrates. About 250 mg $L^{-1}$ sodium acetate was fed to an anode compartment with a flow rate of 0.326 mL $min^{-1}$ by continuous mode. The current generated from the DCMFC was higher than the value produced from MFC with a single cathode. COD removal of dual-cathode MFC was also higher than that of single-cathode MFC. The nitrate didn't affect current generation at 2 mM, but when 4 and 8 mM nitrate was supplied, the current in the single-cathode and dual-cathode MFC was decreased by 98% from $5.97{\pm}0.13$ to $0.23{\pm}0.03$ mA and $8.40{\pm}0.23$ to $0.20{\pm}0.01$ mA, respectively. These results demonstrate that increasing of contact area of the anode and cathode can raise current generation by an improvement in the cathode reaction.