High strength bioethanol wastewater inoculated with single-strain or binary consortium feeding air-cathode microbial fuel cells

Bioethanol industries generate a large volume of high strength wastewater called vinasse. This study compares the performance of microbial fuel cells (MFCs), inoculated with a single-strain or a binary consortium, to produce bioelectricity while simultaneously reducing the COD levels and removing the vinasse color. The MFCs achieved the power density of 124.0 +/- 0.2 mW/m(2) when inoculated with a strain of Shewanella oneidensis (MFC/So) and 178.0 +/- 0.8 mW/m(2) after inoculation with a strain of Clostridium butyricum (MFC/Cb). However, a better performance in power density was reached by the MFC inoculated with both cultures (MFC/So-Cb), which produced 205.0 +/- 0.5 mW/m(2). Additionally, the results showed a decrease in the initial COD (36,440 mg/L), as well as a decolorization. Thus, the MFC/So, MFC/Cb, and MFC/So-Cb caused a reduction in COD by 41.8 +/- 2.4%, 20.1 +/- 4.4%, and 53.8 +/- 5.9%, respectively, and in color by 62 +/- 4%, 70 +/- 4%, and 58 +/- 5%, respectively. These findings demonstrate that high power density can be produced using raw vinasse as a substrate in air-cathode MFCs. However, the coulombic efficiency was low indicating that the COD conversion into electricity must be improved. Novelty: This work combines fermentative and metal-reducing bacteria, instead of mixed cultures with unknown microorganisms, to break down complex organics in the vinasse, simultaneously to electricity generation. No studies have been found concerning Shewanella oneidensis and Clostridium butyricum strains for harvesting bioelectricity from bioethanol wastewater. Second, different from early studies, this work uses the real high strength wastewater, without dilution or any pre-treatment, before MFC process. Third, here we consider the total biomass at the end process to calculate the COD removal rate. Finally, we employed electronic load, never used previously, in MFC polarization measurements. (c) 2018 American Institute of Chemical Engineers Environ Prog, 38: 380-386, 2019