Effect of temperature and hydraulic retention time on hydrogen producing granules : homoacetogenesis and morphological characteristics

The effect of temperature and hydraulic retention time (HRT) on the homoacetogenesis and on .the morphological characteristics of hydrogen producing granules was investigated. Hydrogen was produced using an expanded granular sludge blanket (EGSB) reactor, fed with glucose and Larabinose, under mesophilic (37ºC), thermophilic (55ºC), and hyperthermophilic (70ºC) conditions. Apparent homoacetogenesis was observed only at mesophilic conditions. Glucose was utilized preferentially over L-arabinose at thermophilic and hyper-thermophilic conditions. Higher yields of hydrogen production were linked to the decrease of lactic acid and the increase of nbutyrate, in all temperatures tested. Under mesophilic conditions with an organic loading rate (OLR) of 5KgCOD/m3/d the total filaments length per VSS (TL/VSS) increased and the apparent granules density (VSS/TA) dropped off. With the application of OLR 10 and 16KgCOD/m3/d, TL/VSS decreased and the VSS/TA augmented suggesting an increase of granules density. Under thermophilic conditions the enhance of TL/VSS and the diminish of VSS/TA only occurred with the application of OLR16KgCOD/m3/d, while under hyperthermophilic conditions it happened since the beginning of operation with the application of OLR10KgCOD/m3/d. Granules size was not affected by temperature but the application of higher OLR promote a decline on the percentage of projected area of aggregates with equivalent diameter (Deq) larger than 1 mm.Fundação para a Ciência e a Tecnologia (FCT) - SFRH/BD/29823/2006, SFRH/BPD/24221/2005, projecto POCTI/ENR/57786/200

Bio-hydrogen production in an EGSB reactor under mesophilic, thermophilic and hyperthermophilic conditions

Mesophilic, thermophilic and hyperthermophilic bio-hydrogen production with an expanded granular sludge blanket (EGSB) fed with glucose and arabinose, without methane production, was demonstrated. Homoacetogenesis was observed on reactor when operated under mesophilic (37ºC) conditions but not under thermophilic (55ºC) and hyper-thermophilic conditions (70ºC). It was also found that under thermophilic and hyper-thermophilic conditions glucose is preferentially consumed than arabinose.Fundação para a Ciência e a Tecnologia (FCT) - SFRH/BD/29823/2006, SFRH/BPD/24221/2005, POCI/ENR/57786/2004

Effect of arabinose concentration on dark fermentation hydrogen production using different mixed cultures

Dark fermentation hydrogen production from arabinose at concentrations ranging between 0 and 100 g/L was examined in batch assays for three different mixed anaerobic cultures, two suspended sludges (S1, S2) obtained from two different sludge digesters and one granular sludge (G) obtained from a brewery wastewater treatment plant. After elimination of the methanogenic activity by heat treatment, all mixed cultures produced hydrogen, and optimal hydrogen rates and yields were generally observed for concentrations between 10 and 40 g/L of substrate. Higher concentrations of arabinose up to 100 g/L inhibited hydrogen production, although the effect was different from inoculum to inoculum. It was evident that the granular biomass was less affected by increased initial arabinose concentrations when calculating the rate of decrease in hydrogen yields versus arabinose concentrations, compared against the two suspended sludges. The largest amount of soluble microbial product produced for all three inocula was for n-butyrate. Also, valeric acid production was observed in some samples.Fundação para a Ciência e a Tecnologia (FCT

Influence of the anaerobic biodegradation of different types of biodiesel on the natural attenuation of benzene

In the present research work, different types of biodiesel were produced by a homogeneous alkali transesterification reaction using soybean oil, pork lard, and castor bean oil as raw materials, to evaluate how their different compositions may affect the biodegradability, namely, in the presence of benzene. Biodiesel was characterized according to the European standard EN 14214. The anaerobic biodegradation of the different types of biodiesel was examined as well as its influence on the biodegradation of benzene. Analyses were performed to determine the volume of methane ( directly related to the anaerobic biodegradation of biodiesel), the concentration of benzene over time, and the production of organic acids. The results showed methane production resulting from the anaerobic degradation of all biodiesel types. The differences between the degradation behavior of each fuel were negligible, contrary to what was expected; however, the amount of methane produced was low due to nutrient limitations. This fact was confirmed by the organic acid analysis as well as by the addition of new media. Anaerobic benzene biodegradation was found to be negatively impacted by the presence of all biodiesel types on average; therefore, the results of this study may impact management of sites that contain biodiesel and fuel hydrocarbon contamination

Effect of methanogenic inhibitors, inocula type, and temperature on biohydrogen production from food components

Dark fermentation hydrogen production from a mixture of food components using two different methods of methanogenic inhibition (autoclaving and BES) and three different temperatures (37, 60, and 70 ºC) was examined in batch assays for two different mixed anaerobic cultures - one suspended sludge (S) obtained from an anaerobic digester and one granular sludge (G) obtained from a brewery wastewater treatment plant. In general, BES-inhibition of sludge was more robust when compared against heat-treated inoculum. Also, hydrogen, VFA, and sCOD production were affected by increases in temperature although the effects were less severe for G than for S. In addition, differences in individual VFAs were observed between the two inocula. S produced more acetate as a percentage of VFATOTAL compared to G. Conversely, G produced more butyrate compared to S. Differences in the microbial communities were likely responsible for the diverse behaviour of the two inocula.Fundação para a Ciência e a Tecnologia (FCT

Fermentative bio-hydrogen production from organic wastes and sugars

Utilization of renewable energy has been identified as a priority within the “European Energy Policy” which stresses the need to develop new sources of green energy. A follow-up of the programme “Intelligent Energy – Europe” (Decision No. 1230/2003/EC of the European Parliament and of the Council of 26 June 2003) is projected for the 7th Framework Programme (2007-2013). The main focus of the programme is the production of electricity from renewable sources of energy, as described in Directive 2001/77/EC of the European Parliament and of the Council of 27 September 2001. According to this document, Portugal has committed to raise the national electricity production exclusively from renewable sources to 39% by 2010. In addition, it constitutes an essential part of the package of measures necessary to comply with the commitments made by the EU under the 1997 Kyoto Protocol on the reduction of greenhouse gas emissions. Hydrogen is a CO2-neutral energy source with a very promising future as an alternative to fossil fuels for energy production. The treatment and disposal of wastes by conventional methods poses many problems throughout the world and may result in the consumption of energy. In addition, costs to dispose and treat wastes are escalating. Hydrogen can be produced, from undesirable waste products by bacterial fermentation, to generate electricity. The Centre for Biological Engineering at the University of Minho is studying bio-hydrogen production from organic wastes and sugars. The specific tasks of the project (FCT/POCI/ENR/57786/2004) include the utilization of different waste compositions from a real kitchen waste and sugars to produce and optimize H2 yields, methanogenesis inhibition strategies, design, construction and operation of batch and continuous lab scale reactors for mesophilic (37 °C), thermophilic (55 °C), and hyperthermophilic (70 °C) conditions. In addition, molecular ecology techniques are being used to study bacterial community dynamics in the different bioreactors, comparing the microbial communities developed at different temperatures and different OLR. One objective is to determine the optimal conditions to select the most important microorganisms involved in H2 production

Effect of pesticide bendiocarbamate on distribution of acetylcholine- and butyrylcholine-positive nerves in rabbit's thymus

Many pesticides used in agriculture have a negative effect on organisms. The group of hazardous pesticides includes the cholinesterase inhibitor bendiocarbamate. According to literature, bendiocarbamate has relatively low toxicity in mammals and vertebrates in general, since it does accumulate in their tissues and the cholinesterase activity returns to norm within 24 h after acute exposure. The present study focused on the influence of bendiocarbamate on rabbit thymus after its administration at a dose of 5 mg/kg body weight (BW) for the period of 3 months. The thymus was observed for acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE)-positive nerve fibers visualized by histochemical methods. Microscopic findings of BuChE - positive nerve fibers show the same density and the topography by the experimental and the control animals. On the other hand, AChE - positive nerve fibers in experimental animals after administration of bendiocarbamate is only poorly identified, suggesting that bendiocarbamate inhibits AChE but not BuChE

Effect of pH on fermentative hydrogen production from L-arabinose using mixed cultures

Hydrogen is now considered one of the alternatives to fossil fuels. It is preferred to biogas or methane because hydrogen is not chemically bound to carbon and therefore, combustion does not contribute to green house gases or acid rain [1]. One alternative to sustainable H2 energy production from renewable energy sources is through microbiological fermentation. There have been many studies examining the effect of pH in fermentative hydrogen production from glucose and sucrose using mixed microflora [2,3,4,5,6]. However, fermentative hydrogen production from arabinose, one of the most common pentoses and a component of various biopolymers such as hemicellulose and plant polysaccharides using mixed microflora has not been previously examined. Understanding the influence of pH on biohydrogen production is necessary to develop arabinose-based hydrogen fermentation applications, such as the use of agricultural wastes. Biohydrogen production from arabinose was examined using three different anaerobic sludges with different pHs ranging from 4.5 to 8.0. Arabinose (30 g/L) was used as the substrate for all experiments. Individual cumulative hydrogen production data were used to estimate the three parameters of the modified Gompertz equation. This model has been used for describing the progress of cumulative gas production obtained from the batch experiments. Higher hydrogen production potentials (more than 35 mL) were observed with pH values greater than 6.0 for Unicer (granular sludge) and Choupal (disperse anaerobic digester sludge supplemented with fat) and greater than 6.5 for Freixo (disperse anaerobic digester sludge). Choupal biomass had the largest hydrogen production rate (4.8±1.4 mL/h) at pH 7.5, compared with the other two sludges. Unicer biomass had the shortest lag time (10.6±2.4 h) at pH 8.0. The highest hydrogen yield was observed with Choupal biomass (2.5 mol H2/mol arabinose consumed), with pH 6.0. The granular biomass showed different behaviour than the suspended biomasses. The differences may be explained by smaller lag phases, the percentage of acetate produced, the higher percentage of ethanol produced, and the amount of arabinose consumed. The percentage of n-butyrate was highly correlated with the percentage of acetate (R2 = 0.980) in Freixo biomass. A high correlation (R2 = 0.973) was observed between the percentage of n-butyrate and the percentage of ethanol in Unicer biomass, suggesting that the fermentation is following the butyrate/ethanol pathways which correspond to the lower yields of hydrogen obtained