Abstract
In this work, the effect of the external load on the current and power generation, as well as on the pollutant removal by microbial fuel cells (MFCs), has been studied by step-wise modifying the external load. The load changes included a direct scan, in which the external resistance was increased from 120 Ω to 3300 Ω, and a subsequent reverse scan, in which the external resistance was decreased back to 120 Ω. The reduction in the current, experienced when increasing the external resistance, was maintained even in the reverse scan when the external resistance was step-wise decreased. Regarding the power exerted, when the external resistance was increased below the value of the internal resistance, an enhancement in the power exerted was observed. However, when operating near the value of the internal resistance, a stable power exerted of about 1.6 µW was reached. These current and power responses can be explained by the change in population distribution, which shifts to a more fermentative than electrogenic culture, as was confirmed by the population analyses. Regarding the pollutant removal, the effluent chemical oxygen demand (COD) decreased when the external resistance increased up to the internal resistance value. However, the effluent COD increased when the external resistance was higher than the internal resistance. This behavior was maintained in the reverse scan, which confirmed the modification in the microbial population of the MFC.
Highlights
The increasing world population and the rising standard of living are the main reasons for the increase in energy demand
The external resistance of 3300 Ω was selected in order to ensure that the upper limit of the resistance range is significantly above the internal resistance of the microbial fuel cells (MFCs) used in this study, the latter being about 2200 Ω
With the aim of ensuring the reproducibility of the tests, each external resistance value was kept in the MFC for 7 days in order to ensure a steady state response
Summary
The increasing world population and the rising standard of living are the main reasons for the increase in energy demand. The rise in energy consumption is accompanied by the deterioration of the natural environment. With the aim to protect the environment, a number of steps have been taken to minimize the negative effects of energy production. During the last few years, more attention has been focused on alternative energy sources that are abundant and environment-friendly [1]. Energy production from some renewable energy sources strongly depends on atmospheric conditions, which makes the sources hardly appropriate for addressing peak demands. Continuous energy supply cannot be ensured only by these sources, and novel renewable energy technologies are required
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