Abstract
Benthic microbial fuel cells (BMFC) are devices that remove organic matter (OM) and generate energy from sediments rich in organic nutrients. They are composed of electrodes with adequate different distances and floating air cathodes in an aqueous medium with saturated oxygen. In this study we proposed to design, build, analyze and evaluate a set of BMFCs with floating air cathodes to test the optimal distance between the electrodes, using sediment from the Bay of Campeche as a substrate. For the analysis of OM removal, COD tests, volatile solids (VS), E4/E6 study and FTIR analysis were performed. Power generation was evaluated through polarization curves, cyclic voltammetry and electrochemical impedance spectroscopy (EIS). We achieved a current density and power density at 10 cm depth of 929.7 ± 9.5 mA/m2 and 109.6 ± 7.5 mW/m2 respectively, with 54% removal of OM from the sediment, obtaining formation of aliphatic structures. BMFCs are proposed as adequate systems for bioremediation and power generation. The system at 10 cm depth and 100 cm distance between sediment and the floating air cathode had a good performance and therefore the potential for possible scaling.
Highlights
In Mexico there is a high level of pollution of marine resources, especially in the Bay of Campeche, where according to reports from the Autonomous University of Campeche, the National Autonomous University of Mexico, the Secretary of Marine and Natural Resources (SEMARNAT) and the Secretary of Urban Development and Environment (SEDUMA), there are high levels of Organic Matter (OM), mainly due to anthropogenic factors [1]
The Secretary of Environment and Natural Resources (Semarnat) and the Commission for Protection Against Health Risks (Copriscam) have pointed out that the lack of wastewater treatment plants causes the increase in pollution levels in the bay [24]
There is no significant difference in the percentage of removal with the anode electrode at 10 cm depth since at this depth a maximum removal of 52.89% was obtained, which is why it is concluded that at both depths a large amount of OM is removed, this quantity being greater than the percentage reported by other authors in sediments
Summary
In Mexico there is a high level of pollution of marine resources, especially in the Bay of Campeche, where according to reports from the Autonomous University of Campeche, the National Autonomous University of Mexico, the Secretary of Marine and Natural Resources (SEMARNAT) and the Secretary of Urban Development and Environment (SEDUMA), there are high levels of Organic Matter (OM), mainly due to anthropogenic factors [1]. There are different bioremediation technologies that help to reduce the OM content and improve the sediment conditions and benthic microbial fuel cells (BMFC) could be an option. These are devices where the anodic electrode is buried in the anaerobic sediment and the cathode electrode suspended in the aerobic water column [7]. The performance of the BMFCs can be affected by different factors such as the distance between the electrodes [8,9,10,11,12], the anode depth in the sediment [12,13,14,15] and the reduction reaction in the cathode [16,17,18,19,20], because the implementation of these systems has been proposed on a real scale [21,22,23]. Hong et al (2009) found that the current density depends on the space between the electrodes, varying the distance of the aqueous cathode between 12, 20, 80 and 100 cm; obtaining 11.5, 7.64, 2.51 and 2.11 mA/m2 respectively; and finding that the power density increases when the electrode gap decreases from 0.37 to 1.01 mW/m2 [9,11]
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