Rapid Two Stage Anaerobic Digestion of Nejayote through Microaeration and Direct Interspecies Electron Transfer

ABSTRACT: Corn is one of the main food products in Mexico. The elaboration of corn-derived products generates wastewater with a high organic load (nejayote). Anaerobic digestion is an indicated treatment for wastewater with high organic loads. The results of this study show that the application of microaeration in the hydrolysis-fermentative reactor increased the percentage of volatile fatty acids (VFA) available in the medium by 62%. The addition of a conductive material, such as granulated activated carbon (GAC), promotes DIET (Direct interspecies electrons transfer) in the methanogenic UASB reactor increasing the methane yield by 55%. Likewise, a great diversity of exoelectrogenic bacteria, with the ability to donate electrons DIET mechanisms, were developed in the GAC biofilm, though interestingly, Peptoclostridium and Clostridium (17.3% and 12.75%, respectively) were detected with a great abundance in the GAC biofilm. Peptoclostridium has not been previously reported as a participant in DIET process

Enhancing Biochemical Methane Potential and Enrichment of Specific Electroactive Communities from Nixtamalization Wastewater using Granular Activated Carbon as a Conductive Material

Nejayote (corn step liquor) production in Mexico is approximately 1.4 x 1010 m3 per year and anaerobic digestion is an effective process to transform this waste into green energy. The biochemical methane potential (BMP) test is one of the most important tests for evaluating the biodegradability and methane production capacity of any organic waste. Previous research confirms that the addition of conductive materials significantly enhances the methane production yield. This study concludes that the addition of granular activated carbon (GAC) increases methane yield by 34% in the first instance. Furthermore, results show that methane production is increased by 54% when a GAC biofilm is developed 10 days before undertaking the BMP test. In addition, the electroactive population was 30% higher when attached to the GAC than in control reactors. Moreover, results show that electroactive communities attached to the GAC increased by 38% when a GAC biofilm is developed 10 days before undertaking the BMP test, additionally only in these reactors Geobacter was identified. GAC has two main effects in anaerobic digestion; it promotes direct interspecies electron transfer (DIET) by developing an electro-active biofilm and simultaneously it reduces redox potential from -223 mV to -470 mV. These results suggest that the addition of GAC to biodigesters, improves the anaerobic digestion performance in industrial processed food waste

Pretreatment of vinasse from the sugar refinery industry under non-sterile conditions by Trametes versicolor in a fluidized bed bioreactor and its effect when coupled to an UASB reactor

During hydrous ethanol production from the sugar refinery industry in Mexico, vinasse is generated. Phenolic compounds and melanoidins contribute to its color and make degradation of the vinasse a difficult task. Although anaerobic digestion (AD) is feasible for vinasse treatment, the presence of recalcitrant compounds can be toxic or inhibitory for anaerobic microorganism. Therefore, this study presents new data on the coupled of the FBR (Fluidized Bed Bioreactor) to the UASB (Upflow Anaerobic Sludge Blanket) reactor under non-sterile conditions by T. versicolor. Nevertheless, for an industrial application, it is necessary to evaluate the performance in this kind of proposal system. Therefore, this study used a FBR for the removal of phenolic compounds (67%) and COD (38%) at non-sterile conditions. Continuous operation of the FBR was successfully for 26 days according to the literature. When the FBR was coupled to the UASB reactor, we obtained a better quality of effluent, furthermore methane content and yield were 74% and 0.18 m 3 CH/ kg COD respectively. This study demonstrated the possibility of using for an industrial application the coupled of the FBR to the UASB reactor under non-sterile conditions. Continuous operation of the FBR was carried out successfully for 26 days, which is the highest value found in the literature

Generación de electricidad a partir de una celda de combustible microbiana tipo pem

Se empleó una celda de combustible microbiana (CCM) a escala de laboratorio para la generación de electricidad. La celda consistió de dos cámaras separadas por una membrana de intercambio protónico (PEM). Se utilizaron electrodos de papel carbón y un catolito acuoso burbujeado con aire para proveer O2 disuelto al electrodo. La generación de potencia en la CCM, se debió a la presencia de bacterias como biocatalizadores en la cámara del ánodo. Las bacterias fueron obtenidas de un inóculo mixto anaerobio de tipo entérico, empleando agua residual sintética (ARS) como sustrato. Se determinó la influencia de la temperatura y el pH sobre el rendimiento de la CCM, encontrando que la mayor densidad de potencia fue generada a temperatura mesofílica de 35 ±5°C y pH entre 5 y 6. Empleando resistencias de 600 y 1000Ω se obtuvieron densidades de 640 y 336mW·m‑2, respectivamente. La eficiencia coulómbica obtenida fue de 59,8%. Este tipo de sistemas resultan atractivos para la generación de electricidad y a la vez para la degradación de la fracción orgánica

Generación de electricidad a partir de una celda de combustible microbiana tipo pem

Se empleó una celda de combustible microbiana (CCM) a escala de laboratorio para la generación de electricidad. La celda consistió de dos cámaras separadas por una membrana de intercambio protónico (PEM). Se utilizaron electrodos de papel carbón y un catolito acuoso burbujeado con aire para proveer O2 disuelto al electrodo. La generación de potencia en la CCM, se debió a la presencia de bacterias como biocatalizadores en la cámara del ánodo. Las bacterias fueron obtenidas de un inóculo mixto anaerobio de tipo entérico, empleando agua residual sintética (ARS) como sustrato. Se determinó la influencia de la temperatura y el pH sobre el rendimiento de la CCM, encontrando que la mayor densidad de potencia fue generada a temperatura mesofílica de 35 ±5°C y pH entre 5 y 6. Empleando resistencias de 600 y 1000Ω se obtuvieron densidades de 640 y 336mW·m‑2, respectivamente. La eficiencia coulómbica obtenida fue de 59,8%. Este tipo de sistemas resultan atractivos para la generación de electricidad y a la vez para la degradación de la fracción orgánica

Removal of Coliphage MS2 Using a Microbial Fuel Cell Stack

Bioelectrochemical technologies offer alternative ways of treating wastewater and using this process to generate electricity. However, research in this area is just beginning to consider environmental transmission of viruses present in wastewater. The viral fecal indicator coliphage MS2 (the most frequently used pathogen model) was used in this study, since it is a well-known indigenous wastewater virus. The scaled-up bioelectrochemical system had a working volume of 167 L and coliphage MS2 concentration decreased from 8000 to 285 PFU/mL. The kinetics were quantified up to 15 h, after which excessive yeast growth in the system prevented further bacteriophage determination. The logarithmic reduction value (LRV) calculated within the first three hours was 3.8. From 4 hours to 14, LRV values were from 4.1 to 4.8, and in hour 15 the LRV increased to 5.3, yielding a more than 90% reduction. Overall, results obtained indicate that the scaled-up bioelectrochemical treatment system was efficient in reducing coliphage MS2 densities and could be used as a model to explore its further applicability for the reduction of viruses or pathogens in treated effluents

Methane production by treating vinasses from hydrous ethanol using a modified UASB reactor

<p>Abstract</p> <p>Background</p> <p>A modified laboratory-scale upflow anaerobic sludge blanket (UASB) reactor was used to obtain methane by treating hydrous ethanol vinasse. Vinasses or stillage are waste materials with high organic loads, and a complex composition resulting from the process of alcohol distillation. They must initially be treated with anaerobic processes due to their high organic loads. Vinasses can be considered multipurpose waste for energy recovery and once treated they can be used in agriculture without the risk of polluting soil, underground water or crops. In this sense, treatment of vinasse combines the elimination of organic waste with the formation of methane. Biogas is considered as a promising renewable energy source. The aim of this study was to determine the optimum organic loading rate for operating a modified UASB reactor to treat vinasse generated in the production of hydrous ethanol from sugar cane molasses.</p> <p>Results</p> <p>The study showed that chemical oxygen demand (COD) removal efficiency was 69% at an optimum organic loading rate (OLR) of 17.05 kg COD/m³-day, achieving a methane yield of 0.263 m³/kg COD_added and a biogas methane content of 84%. During this stage, effluent characterization presented lower values than the vinasse, except for potassium, sulfide and ammonia nitrogen. On the other hand, primers used to amplify the 16S-rDNA genes for the domains Archaea and Bacteria showed the presence of microorganisms which favor methane production at the optimum organic loading rate.</p> <p>Conclusions</p> <p>The modified UASB reactor proposed in this study provided a successful treatment of the vinasse obtained from hydrous ethanol production.</p> <p>Methanogen groups (Methanobacteriales and Methanosarcinales) detected by PCR during operational optimum OLR of the modified UASB reactor, favored methane production.</p