In this paper, the anaerobic treatment of a high organic-strength wastewater-type feedstock, referred as the liquid fraction of pressed municipal solid waste (LPW) was studied for energy recovery and organic matter removal. The processes investigated were (i) dark fermentation to produce biohydrogen, (ii) anaerobic digestion for biogas formation and (iii) microbial fuel cells for electrical energy generation. To find a feasible alternative for LPW treatment (meeting the two-fold aims given above), various one- as well as multi-stage processes were tested. The applications were evaluated based on their (i) COD removal efficiencies and (ii) specific energy gain. As a result, considering the former aspect, the single-stage processes could be ranked as: microbial fuel cell (92.4%)> anaerobic digestion (50.2%)> hydrogen fermentation (8.8%). From the latter standpoint, an order of hydrogen fermentation (2277 J g COD d)> anaerobic digestion (205 J g COD d)> microbial fuel cell (0.43 J g COD d) was attained. The assessment showed that combined, multi-step treatment was necessary to simultaneously achieve efficient organic matter removal and energy recovery from LPW. Therefore, a three-stage system (hydrogen fermentation-biomethanation-bioelectrochemical cell in sequence) was suggested. The different approaches were characterized via the estimation of COD balance, as well.
ResumenSe monitoreó la generación de electricidad de bacterias electrogénicas en celdas de combustibles microbianas de cámara simple (CCMs), usando electrodos de fibra de carbono, con dos inóculos. El primer inóculo se preparó con suelo no intervenido y residuos sólidos orgánicos de la región amazónica de Ecuador y el segundo con suelo no intervenido y residuos sólidos orgánicos de la región alto andina de Ecuador. Se monitoreó el proceso durante 171 días sin renovación del combustible microbiano. Se emplearon CCMs con volúmenes de 20 L, 12 L y 4 L, observándose la influencia en el voltaje de salida. El mejor experimento con suelo de la región alto andina fueron las CCMs de 12 L con una generación promedio de 317 mV, mientras que con suelo de la región amazónica fueron las CCMs de 4 L, generando 270 mV.
Palabras clave: celda de combustible microbiano, bioelectricidad, residuos sólidos orgánicos, bacterias electrogénicas, bioconversión
Bioconversion of Organic solid Wastes with Soils from the Amazonian and High Andean Regions of Ecuador in Single Chamber Microbial Fuel Cells AbstractBioelectricity generation from electrogenic bacteria in single chamber microbial fuel cells (MFCs) was monitored. Carbon fiber as electrodes and two different inoculums were used. The first inoculum was prepared with undisturbed soil and organic solid wastes from the Amazonian region in Ecuador. The second was prepared using undisturbed soil and organic solid wastes from the high Andean region in Ecuador. The process was monitored during 171 days without renovation of microbial fuel. In this work, MFCs with volumes of 20 L, 12 L and 4 L were employed, observing the influence on the output voltage. The best experiment with soil from the high Andean region were the MFCs of 12 L with 317 mV as average generation, while the experiment with soil from the Amazonian region were the MFCs of 4 L, producing 270 mV.
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