ANALYSIS OF THE EFFICIENCY OF MICROBIAL FUEL CELLS BASED ON SULFATE-REDUCTION PROCESS, INTEGRATED IN ANAEROBIC WETLANDS
ROSEN IVANOV*, SVETLANA BRATKOVA, ANATOLIY ANGELOV
Department of Engineering Geoecology, Faculty of Geoexploration, University of Mining and Geology “St. Ivan Rilski”, Sofia, Bulgaria
*Corresponding author: rosen_iv@abv.bg
Keywords: microbial fuel cells, microbial sulfate-reduction, biofilms
Abstract: Microbial fuel cells (MFCs) are systems in which microorganisms, using various energy sources (mainly organic compounds, but also inorganic substrates such as hydrogen sulfide, ferrous or ammonium ions) convert this energy directly into electricity. This process is accomplished as the electrons that are detached from the donor at its oxidation are transferred to an insoluble anode of the fuel cell instead to the relevant natural acceptor (oxygen, sulfates, ferric ions, nitrates). In MFCs based on microbial sulfate-reduction process, the electricity generation is related to the reduction of sulfates to hydrogen sulfide, which plays the role of a mediator and on the anodic surface it is oxidized to elemental sulfur. In most cases, at the continuous operational mode of the microbial fuel cell, the elemental sulfur is accumulated on the surface of the electrode or in the area around it and this leads to deterioration of the electrochemical characteristics of the cell. In this work three MFCs based on the process of microbial sulfate-reduction were tested for a period of over 18 months, as they were integrated in anaerobic wetlands for mining wastewater treatment. The influence of the formed microbial biofilm consisting of diverse microflora and products of the microbial metabolism and of chemical and electrochemical reactions (insoluble sulfides and elemental sulfur) on the efficiency of various components of MFCs was established.