Abstract
Constructed wetland-coupled microbial fuel cell systems (CW-MFCs) incorporate an aerobic zone and an anaerobic zone to generate electricity that achieves the oxidative degradation of contaminants. However, there are few reports on the performance of such coupled systems. In this study, we determined the optimal configuration of CW-MFCs to characterize their electricity generation performance. Based on the results using different levels of dissolved oxygen among the CW-MFCs, we concluded that a 20-cm distance between the anode and cathode produced an optimal removal of chemical oxygen demand (COD) of 94.90% with a 0.15 W/m3 power density, 339.80 Ω internal resistance, and 0.31% coulombic efficiency. In addition, a COD of 200 mg/L provided greater electricity generation (741 mV open circuit voltage, 0.20 W/m3 power density, 339.80 Ω internal resistance, and 0.49 mA current) and purification ability (90.45% COD removal) to meet system COD loading limitations than did higher COD values. By adding 50 mM phosphate buffer solution to synthetic wastewater, relatively high conductivity and buffer capacity were achieved, resulting in improvement in electricity generation. These findings highlight important aspects of bioelectricity generation in CW-MFCs.
Highlights
Microbial fuel cells (MFCs), which make use of domestic sewage, industrial effluent, leachate, sediment, and rhizodeposits as biodegradable substrates, offer a technology for electricity generation in addition to benefits for the environment [1,2,3]
Despite the variation in electrolyte resistance, our results suggest that the accumulation of microorganisms feeding on higher chemical oxygen demand (COD) concentrations can block electron conduction on the interface of the activated carbon acting as an electrode, which results in higher internal resistance
The maximum current density, coulombic efficiency, and COD removal rate were obtained with an electrode spacing of 20 cm
Summary
Microbial fuel cells (MFCs), which make use of domestic sewage, industrial effluent, leachate, sediment, and rhizodeposits as biodegradable substrates, offer a technology for electricity generation in addition to benefits for the environment [1,2,3]. Organic matter can be used as a renewable resource to generate electrons and protons via electrochemically active bacteria in MFCs [4,5,6]. Protons are released into solution and electrons are produced at the anode; subsequently, at the interface of the cathode, electrons pass through the outer circuit before they can reach the cathode and combine with electron acceptors [7,8]. Numerous studies have focused on exploiting constructions in MFCs [11], and there is a need to study the systems with electric potential between the anode and cathode. Plant-MFCs and MFC-coupled constructed wetlands (CW-MFCs) have been studied [12,13]. In one such system, microbes in the anaerobic
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