Temporary feeding shocks increase the productivity in a continuous biohydrogen-producing reactor

Continuous hydrogen production stability and robustness by dark fermentation were comprehensively studied at laboratory scale. Continuous bioreactors were operated at two different hydraulic retention times (HRT) of 6 and 10 hours. The reactors were subjected to feeding shocks given by decreases in the HRT, and therefore the organic loading increase, during 6 and 24 hours. Results indicated that the H2 productivity was significantly improved by the temporary organic shock loads, increasing the hydrogen production rate up to 40%, compared to the rate obtained at the steady-state condition. Besides, it was observed that after the shock load, the stability of the reactor (measured as the hydrogen production rate) was recovered attaining the values observed before the feeding shocks. The bioreactor operated at shorter HRT (6 h) showed better H2 productivity (17.3 ± 1.1 L H2/L-d) in comparison to the other one operated at 10 h HRT (12.4 ± 1.6 L H2/L-d)

Evaluation of various cheese whey treatment scenarios in single-chamber microbial electrolysis cells for improved biohydrogen production

In this study single-chamber microbial electrolysis cells (MECs) were applied to treat cheese whey (CW), an industrial by-product, and recover H2 gas. Firstly, this substrate was fed directly to the MEC to get the initial feedback about its H2 generation potential. The results indicated that the direct application of CW requires an adequate pH control to realize bioelectrohydrogenesis and avoid operational failure due to the loss of bioanode activity. In the second part of the study, the effluents of anaerobic (methanogenic) digester and hydrogenogenic (dark fermentative H2-producing) reactor utilizing the CW were tested in the MEC process (representing the concept of a two-stage technology). It turned out that the residue of the methanogenic reactor – with its relatively lower carbohydrate- and higher volatile fatty acid contents – was more suitable to produce hydrogen bioelectrochemically. The MEC operated with the dark fermentation effluent, containing a high portion of carbohydrates and low amount of organic acids, produced significant amount of undesired methane simultaneously with H2. Overall, the best MEC behavior was attained using the effluent of the methanogenic reactor and therefore, considering a two-stage system, methanogenesis is an advisable pretreatment step for the acidic CW to enhance the H2 formation in complementary microbial electrohydrogenesis

Feasibility of quaternary ammonium and 1,4-diazabicyclo[2.2.2]octane-functionalized anion-exchange membranes for biohydrogen production in microbial electrolysis cells

In this work, two commercialized anion-exchange membranes (AEMs), AMI-7001 and AF49R27, were applied in microbial electrolysis cells (MECs) and compared with a novel AEM (PSEBS CM DBC, functionalized with 1,4-diazabicyclo[2.2.2]octane) to produce biohydrogen. The evaluation regarding the effect of using different AEMs was carried out using simple (acetate) and complex (mixture of acetate, butyrate and propionate to mimic dark fermentation effluent) substrates. The MECs equipped with various AEMs were assessed based on their electrochemical efficiencies, H2 generation capacities and the composition of anodic biofilm communities. pH imbalances, ionic losses and cathodic overpotentials were taken into consideration together with changes to substantial AEM properties (particularly ion-exchange capacity, ionic conductivity, area- and specific resistances) before and after AEMs were applied in the process to describe their potential impact on the behavior of MECs. It was concluded that the MECs which employed the PSEBS CM DBC membrane provided the highest H2 yield and lowest internal losses compared to the two other separators. Therefore, it has the potential to improve MECs

Supported ionic liquid membrane based on [bmim][PF6] can be a promising separator to replace Nafion in microbial fuel cells and improve energy recovery: A comparative process evaluation

In this study, mixed culture bioelectrochemical systems were operated with various membrane separators: one prepared with 1-Butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) ionic liquid and another one called Nafion, used as reference for comparative evaluation. In the course of experiments, the primary objective was to reveal the influence of membranes-type on microbial fuel cell (MFC) behavior by applying a range of characterization methods. These included cell polarization measurements, monitoring of dehydrogenase enzyme activity and cyclic voltammetry for the analysis of anode biofilm properties and related electron transfer mechanism. Additionally, MFC performances for both membranes were assessed based on Coulombic efficiency as well as substrate (acetate) concentration dependency of energy yields. As a result, it was demonstrated that the ionic liquid-containing membrane could be suitable to compete with Nafion and appears as a candidate to be further investigated for microbial electrochemical applications

Perfil inmunológico de los cerdos de dos meses de edad

El grado de madurez inmunológica se ha evaluado e-n humanos y animales por medio del perfil inmunológico, el cual se basa en la cuantificación de los diferentes leucocitos y subpoblaciones de linfocitos circulantes, en la capacidad fagocitaria y microbic

PRODUCCIÓN DE ELECTRICIDAD EN CELDAS DE COMBUSTIBLE MICROBIANAS UTILIZANDO AGUA RESIDUAL: EFECTO DE LA DISTANCIA ENTRE ELECTRODOS

Se evaluó la influencia de la separación de electrodos sobre la producción de electricidad y la eliminación de materia orgánica en celdas de combustible microbianas usando agua residual. Para ello se construyeron tres celdas de geometría semejante pero con diferente volumen. En promedio, se obtuvo una eficiencia de eliminación de materia orgánica del 71%. La duración del ciclo fue de 0.97 días para la celda de 40 mL, 1.03 días para la celda de 80 mL y 5.93 días para la celda de 120 mL. El aumento de distancia entre los electrodos (4, 8 y 12 cm) no causó un efecto negativo en la generación de electricidad, pues en la mayor separación (celda de 120 mL) se alcanzó un voltaje máximo de 660 mV, mientras que para las celdas de 40 y 80 mL fue de 540 mV y 532 mV, respectivamente. La densidad de potencia máxima se presentó en la celda con separación de 12 cm (408 mW/m2). Sin embargo, se observó que la potencia volumétrica disminuyó a medida que aumentó la separación entre los electrodos

Producción de electricidad en celdas de combustible microbianas utilizando agua residual: efecto de la distancia entre electrodos

The influence of the electrode separation on electricity production and organic matter removal was studied in microbial fuel cells using wastewater. Three cells were constructed with similar geometry, but different volume. On average, 71% of the initial organic matter was removed. Cycle duration was 0.97, 1.03 and 5.93 days for the 40, 80 and 120 mL cells, respectively. The increment of the distance between the electrodes (4, 8 and 12 cm) did not affect electricity generation adversely. The higher voltage was obtained in the 120 mL cell (660 mV), whereas 540 and 532 mV were obtained for the 40 and 80 mL cells, respectively. Maximum power density was 408 mW/m2 and was obtained in the 12 cm cell. However, it was observed that volumetric power decreased as the separation between electrodes increased.Se evaluó la influencia de la separación de electrodos sobre la producción de electricidad y la eliminación de materia orgánica en celdas de combustible microbianas usando agua residual. Para ello se construyeron tres celdas de geometría semejante pero con diferente volumen. En promedio, se obtuvo una eficiencia de eliminación de materia orgánica del 71%. La duración del ciclo fue de 0.97 días para la celda de 40 mL, 1.03 días para la celda de 80 mL y 5.93 días para la celda de 120 mL. El aumento de distancia entre los electrodos (4, 8 y 12 cm) no causó un efecto negativo en la generación de electricidad, pues en la mayor separación (celda de 120 mL) se alcanzó un voltaje máximo de 660 mV, mientras que para las celdas de 40 y 80 mL fue de 540 mV y 532 mV, respectivamente. La densidad de potencia máxima se presentó en la celda con separación de 12 cm (408 mW/m2). Sin embargo, se observó que la potencia volumétrica disminuyó a medida que aumentó la separación entre los electrodos

Hydrogen production in two-chamber MEC using a low-cost and biodegradable poly(vinyl) alcohol/chitosan membrane

Hydrogen production was evaluated in two-chamber microbial electrolysis cells (MEC), where the chambers of the cell were separated using a new economical and environmentally friendly membrane made of poly (vinyl) alcohol/chitosan (PVA/CS). The MEC performance was compared to that of Nafion. The obtained results indicated that the MEC performance for hydrogen production did not show significant differences between the PVA/CS and Nafion membranes. MEC with PVA/CS showed the hydrogen production rate and hydrogen yield of 1277 ± 46 mL H2Lcat−1d−1 and 974 ± 116 mL H2 gacetate−1, respectively. The PVA/CS membrane allowed acetate removal that was 7% higher than that of Nafion due to the lower pH gradient and a lower voltage drop that increased the ion transfer across the membrane.Fil: Gonzalez Pabon, Maria Jesus. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Cardeña, René. Universidad Nacional Autónoma de México; MéxicoFil: Corton, Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Buitrón, Germán. Universidad Nacional Autónoma de México; Méxic

Microalgal–bacterial aggregates with flue gas supply as a platform for the treatment of anaerobic digestion centrate

Producción CientíficaBACKGROUND: Centrate treatment using microalgal–bacterial processes might be limited by the hydraulic retention time (HRT) required to achieve satisfactory chemical oxygen demand (COD) and nutrients removal. Moreover, the poor settling of microalgal biomass still limits the technical and economic performance of microalgal–bacterial processes. In this work, the performance of microalgal–bacterial aggregates (MABAs) supplied with flue gas was investigated as an effective strategy to improve the treatment of centrate from anaerobic digestion of winery wastewater. RESULTS: MABAs supplied with flue gas achieved maximum soluble COD, N‐NO3−, P‐PO43− and N‐NH4+ removal efficiencies of 95%, 94%, 100%, and 100%, respectively, in five‐fold centrate dilution within 7 days of operation. Centrate turbidity or its components did not hinder the performance of the MABAs under the conditions tested and no aggregates were formed in controls without MABAs inoculation. The mean diameter of the MABAs after centrate treatment was the same or even larger than that of the aggregates of the inoculum. Scanning electron microscopy analyses showed that the liquid medium composition influenced the structure and the type of microalgae cells established in the MABAs. CONCLUSION: MABAs‐based centrate treatment supported by flue gas is a promising technology for improving COD and nutrients removal from centrate as well as further biomass harvesting.Fondo de Sustentabilidad Energética SENER‐CONACYT (Mexico), (project 247006)Ecos‐Nord‐CONACYT (project 296541

Decolourization of Direct Blue 2 by peroxidases obtained from an industrial soybean waste

In this work the decolourization of Direct Blue 2 dye (DB2) using an industrial soybean waste as a source of peroxidases was studied. Temperature, pH, amount of H2O2 and concentration of dye were evaluated to determine the maximum catalytic activity of the enzyme during the dye degradation process. It was observed that a temperature of 40°C, a pH of 5 and a concentration of 40 mg/L for the dye in aqueous phase, play a significant role in the overall enzyme-mediated reaction. The maximum decolourization efficiency achieved under optimal conditions was 70% ± 4%. HPLC studies were carried out to confirm dye degradation and analyse the intermediate metabolites. The oxidation products quantified during the reaction were benzidine and 4 aminobiphenyl. Also, an increase in toxicity, determined by Vibrio fisheri, was observed after the enzymatic oxidation of the dye. Results suggest that the oxidation of DB2 with peroxidases can be recommended as a pretreatment step before a conventional treatment process