scholarly journals Impact of operational conditions on methane yield and microbial community composition during biological methanation in in situ and hybrid reactor systems

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Radziah Wahid ◽  
Svein Jarle Horn
Keyword(s):  
Volatile Fatty Acids ◽  
Microbial Community Composition ◽  
Archaeal Community ◽  
Methane Yield ◽  
Ex Situ ◽  
Hybrid Reactor ◽  
Reactor Performance ◽  
High Accumulation ◽  
Operational Conditions

Abstract Background Biogas can be upgraded to methane biologically by adding H2 to biogas reactors. The process is called biological methanation (BM) and can be done in situ in a regular biogas reactor or the biogas can be transferred to a separate ex situ upgrading reactor. The hybrid BM concept, a combination of in situ and ex situ BM, has received little attention, and only a few studies have been reported. The hybrid BM has the advantage of resolving the issue of pH increment during in situ BM, while the size of the ex situ BM reactor could be reduced. Results In this study, the efficiency of in situ and hybrid biological methanation (BM) for upgrading raw biogas was investigated. The hybrid BM system achieved a CH4 yield of 257 mL gVS−1 when degrading a feedstock blend of manure and cheese waste. This represented an increase in methane yield of 76% when compared to the control reactor with no H2 addition. A 2:1 H2:CO2 ratio resulted in stable reactor performance, while a 4:1 ratio resulted in a high accumulation of volatile fatty acids. H2 consumption rate was improved when a low manure–cheese waste ratio (90%:10%) was applied. Furthermore, feeding less frequently (every 48 h) resulted in a higher CH4 production from CO2 and H2. Methanothermobacter was found to dominate the archaeal community in the in situ BM reactor, and its relative abundance increased over the experimental time. Methanosarcina abundance was negatively affected by H2 addition and was nearly non-existent at the end of the experiment. Conclusions Our results show that hybrid BM outperforms in situ BM in terms of total CH4 production and content of CH4 in the biogas. In comparison to in situ BM, the use of hybrid BM increased CH4 yield by up to 42%. Furthermore, addition of H2 at 2:1 H2:CO2 ratio in in situ BM resulted in stable reactor operation.

scholarly journals Impact of Operational Conditions on Methane Yield and Microbial Community Composition during Biological Methanation in a Hybrid Reactor System

2021 ◽  
Author(s):  
Radziah Wahid ◽  
Svein Jarle Horn
Keyword(s):  
Volatile Fatty Acids ◽  
Microbial Community Composition ◽  
Archaeal Community ◽  
Methane Yield ◽  
Ex Situ ◽  
Hybrid Reactor ◽  
Reactor Performance ◽  
High Accumulation ◽  
Operational Conditions

Abstract Background: Biogas can be upgraded to methane biologically by adding hydrogen to biogas reactors. The process is called biological methanation (BM) and can be done in-situ in a regular biogas reactor or the biogas can be transferred to a separate ex-situ upgrading reactor. The hybrid BM concept, a combination of in-situ and ex-situ BM, has received little attention, and only a few studies have been reported. The hybrid BM has the advantage of resolving the issue of pH increment during in-situ BM, while the size of the ex-situ BM reactor could be reduced.Results: In this study, the efficiency of in-situ and hybrid biological methanation (BM) for upgrading raw biogas was investigated. The hybrid BM system achieved a CH4 yield of 257 mL gVS-1 when degrading a feedstock blend of manure and cheese waste. This represented an increase in methane yield of 76% when compared to the control reactor with no H2 addition. A 2:1 H2:CO2 ratio resulted in stable reactor performance, while a 4:1 ratio resulted in a high accumulation of volatile fatty acids. H2 consumption rate was improved when a low manure-cheese waste ratio (90%:10%) was applied. Furthermore, feeding less frequently (every 48 hours) resulted in a higher CH4 production from CO2 and H2. Methanothermobacter was found to dominate the archaeal community in the in-situ BM reactor, and its relative abundance increased over the experimental time. Methanosarcina abundance was negatively affected by H2 addition and was nearly non-existent at the end of the experiment. Conclusions: Our results show that hybrid BM outperforms in-situ BM in terms of total CH4 production and content of CH4 in the biogas. The application of hybrid BM increased CH4 yield up to 42%. Furthermore, addition of H2 at 2:1 H2:CO2 ratio in in-situ BM resulted in stable reactor operation.

Hybrid reactor performance in pentachlorophenol (pcp) removal by anaerobic granules

2001 ◽  
Vol 44 (4) ◽  
pp. 137-144 ◽  
Author(s):  
M. De Almeida Prado Montenegro ◽  
E. De Mattos Moraes ◽  
H. Moreira Soares ◽  
R. Filomena Vazoller
Keyword(s):  
Fatty Acids ◽  
Volatile Fatty Acids ◽  
Culture Media ◽  
Biogas Production ◽  
Removal Rate ◽  
Oxygen Demand ◽  
Granular Sludge ◽  
Concentration Addition ◽  
Hybrid Reactor ◽  
Reactor Performance

The present research aimed at evaluating pentachlorophenol (PCP) degradation in a hybrid reactor supplied with a mixture of fatty acids (propionic, butyric, acetic and lactic) and methanol. The performance of the reactor is remarkably stable and efficient during PCP additions at range of 2.0 to 21.0 mg/L. The reduction of chemical oxygen demand (COD) was around 97% and methane was found to be 86% in the biogas production. The efficiency of volatile fatty acids breakdown was 93%, 64% and 74% respectively for butyric, propionic and acetic. PCP total removal of more than 99% was reached by granular sludge activities formed during 21 months of reactor operation. Methanogenic microorganisms predominance was noticed with 105 to 106 cells/mL during enumeration on methanol or lactate added to sulfate culture media. The removal rate was 1.07 mg PCP · g−1 VS · d−1 during the highest PCP concentration addition.

Application of an anaerobic hybrid reactor for petrochemical effluent treatment

2012 ◽  
Vol 65 (12) ◽  
pp. 2098-2105 ◽  
Author(s):  
Mohammad Taghi Jafarzadeh ◽  
Naser Mehrdadi ◽  
Seyed Jamaladdin Hashemian
Keyword(s):  
Biogas Production ◽  
Dairy Wastewater ◽  
Effluent Treatment ◽  
Hybrid Reactor ◽  
Reactor Performance ◽  
Operational Conditions ◽  
Start Up ◽  
Anaerobic Hybrid Reactor ◽  
Petrochemical Wastes

An anaerobic hybrid reactor (UASB/Filter) was used for petrochemical wastewater treatment in mesophilic conditions. The seeded flocculent sludge from a UASB plant treating dairy wastewater, acclimatized to the petrochemical wastes in a two-stage operation. After start up, under steady-state conditions, experiments were conducted at OLRs of between 0.5 and 24 kg TCOD m−3 d−1, hydraulic retention times (HRT) of 4–48 h and up-flow velocities 0.021–0.25 mh−1. Removal efficiencies in the range of 42–86% were achieved at feed TCOD concentrations of 1,000–4,000 mg L−1. The results of reactor performance at different operational conditions and its relations are presented and discussed in this paper. Then, the obtained data are used for determination of kinetic models. The results showed that a second-order model and a modified Stover–Kincannon model were the most appropriate models for this reactor. Finally, the biogas production data were used for the determination of biogas production kinetics.

scholarly journals Disentangling Microbial Syntrophic Mechanisms for Hexavalent Chromium Reduction in Autotrophic Biosystems

2020 ◽  
Author(s):  
Baogang Zhang ◽  
Jun Liu ◽  
Yizhi Sheng ◽  
Jiaxin Shi ◽  
Hailiang Dong
Keyword(s):  
Hexavalent Chromium ◽  
Volatile Fatty Acids ◽  
Elemental Sulfur ◽  
Ex Situ ◽  
Metabolic Reconstruction ◽  
Symbiotic Relationships ◽  
Groundwater Systems ◽  
Remediation Process ◽  
Key Parameter

Abstract Background: Hexavalent chromium [Cr(VI)] is one of ubiquitous heavy-metal contaminants in groundwater, and electron donors are considered to be a key parameter for Cr(VI) biotransformation. During autotrophic remediation process, however, much remains to be unveiled that how complex syntrophic microbial communities couple Cr(VI) reduction with other elemental cycles. Results: Two series of Cr(VI)-reducing groundwater bioreactors were independently amended by elemental sulfur (S0) and iron (Fe0), and inoculated with the same inoculum. After 160 days incubation, both bioreactors showed the similar archaea-dominating microbiota compositions, whereas a higher Cr(VI) reducing rate and more methane production were detected in the Fe0-driven one. Metabolic reconstruction of 23 retrieved genomes revealed complex symbiotic relationships driving distinct elemental cycles coupled with Cr(VI) reduction in bioreactors. In both bioreactors, these inferred Cr(VI) reducers were assumed to live in syntrophy with oxidizers of sulfur, iron, and volatile fatty acids (VFAs) and methane produced by carbon fixers and multi-trophic methanogens, while hydrogen slowly released via an Fe0 corrosion process might readily facilitate methanogenesis and more methane oxidation might be linked to Cr(VI) reduction in the Fe-bioreactor.Conclusion: These findings provide insights into mutualistic symbioses of carbon, sulfur, iron and chromium metabolisms in groundwater systems, providing implications for both in-situ and ex-situ bioremediation of contaminated groundwater.

An in situ and ex situ TEM study of the formation of thin cobalt silicide films by molecular beam epitaxy on the silicon (100) surface

1988 ◽  
Vol 46 ◽  
pp. 884-885
Author(s):  
D. Loretto ◽  
J. M. Gibson ◽  
S. M. Yalisove ◽  
R. T. Tung
Keyword(s):  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Defect Density ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Ex Situ ◽  
Metal Base ◽  
In Situ Experiments ◽  
Potential Applications

The cobalt disilicide/silicon system has potential applications as a metal-base and as a permeable-base transistor. Although thin, low defect density, films of CoSi2 on Si(111) have been successfully grown, there are reasons to believe that Si(100)/CoSi2 may be better suited to the transmission of electrons at the silicon/silicide interface than Si(111)/CoSi2. A TEM study of the formation of CoSi2 on Si(100) is therefore being conducted. We have previously reported TEM observations on Si(111)/CoSi2 grown both in situ, in an ultra high vacuum (UHV) TEM and ex situ, in a conventional Molecular Beam Epitaxy system.The procedures used for the MBE growth have been described elsewhere. In situ experiments were performed in a JEOL 200CX electron microscope, extensively modified to give a vacuum of better than 10-9 T in the specimen region and the capacity to do in situ sample heating and deposition. Cobalt was deposited onto clean Si(100) samples by thermal evaporation from cobalt-coated Ta filaments.

The use of transmission and analytical electron microscopy in studying reactions and phase transformations in thin film

1993 ◽  
Vol 51 ◽  
pp. 842-843
Author(s):  
K. Barmak
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Phase Transformations ◽  
Analytical Electron Microscopy ◽  
Ex Situ ◽  
Multilayer Thin Films ◽  
Absolute Concentration ◽  
Analytical Electron ◽  
Deposition Step

Generally, processing of thin films involves several annealing steps in addition to the deposition step. During the annealing steps, diffusion, transformations and reactions take place. In this paper, examples of the use of TEM and AEM for ex situ and in situ studies of reactions and phase transformations in thin films will be presented.The ex situ studies were carried out on Nb/Al multilayer thin films annealed to different stages of reaction. Figure 1 shows a multilayer with dNb = 383 and dAl = 117 nm annealed at 750°C for 4 hours. As can be seen in the micrograph, there are four phases, Nb/Nb3-xAl/Nb2-xAl/NbAl3, present in the film at this stage of the reaction. The composition of each of the four regions marked 1-4 was obtained by EDX analysis. The absolute concentration in each region could not be determined due to the lack of thickness and geometry parameters that were required to make the necessary absorption and fluorescence corrections.

Transmission Electron Microscopy of Epitaxial silicides grown by ultra high vacuum deposition

1989 ◽  
Vol 47 ◽  
pp. 462-463
Author(s):  
D. Loretto ◽  
J. M. Gibson ◽  
S. M. Yalisove
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Diffraction ◽  
High Vacuum ◽  
High Energy ◽  
Energy Electron ◽  
Ultra High Vacuum ◽  
Ex Situ ◽  
Transmission Electron

The silicides CoSi2 and NiSi2 are both metallic with the fee flourite structure and lattice constants which are close to silicon (1.2% and 0.6% smaller at room temperature respectively) Consequently epitaxial cobalt and nickel disilicide can be grown on silicon. If these layers are formed by ultra high vacuum (UHV) deposition (also known as molecular beam epitaxy or MBE) their thickness can be controlled to within a few monolayers. Such ultrathin metal/silicon systems have many potential applications: for example electronic devices based on ballistic transport. They also provide a model system to study the properties of heterointerfaces. In this work we will discuss results obtained using in situ and ex situ transmission electron microscopy (TEM).In situ TEM is suited to the study of MBE growth for several reasons. It offers high spatial resolution and the ability to penetrate many monolayers of material. This is in contrast to the techniques which are usually employed for in situ measurements in MBE, for example low energy electron diffraction (LEED) and reflection high energy electron diffraction (RHEED), which are both sensitive to only a few monolayers at the surface.

Atomic Layer Deposition of LiF and Lithium Ion Conducting (AlF3)(LiF)x Alloys Using Trimethylaluminum, Lithium Hexamethyldisilazide and Hydrogen Fluoride

2017 ◽  
Author(s):  
Younghee Lee ◽  
Daniela M. Piper ◽  
Andrew S. Cavanagh ◽  
Matthias J. Young ◽  
Se-Hee Lee ◽  
...  
Keyword(s):  
Lithium Ion ◽  
Atomic Layer ◽  
Mass Gain ◽  
Alloy Film ◽  
Ex Situ ◽  
X Ray ◽  
Layer Deposition ◽  
Ion Conducting ◽  
Good Agreement

<div>Atomic layer deposition (ALD) of LiF and lithium ion conducting (AlF<sub>3</sub>)(LiF)<sub>x</sub> alloys was developed using trimethylaluminum, lithium hexamethyldisilazide (LiHMDS) and hydrogen fluoride derived from HF-pyridine solution. ALD of LiF was studied using in situ quartz crystal microbalance (QCM) and in situ quadrupole mass spectrometer (QMS) at reaction temperatures between 125°C and 250°C. A mass gain per cycle of 12 ng/(cm<sup>2</sup> cycle) was obtained from QCM measurements at 150°C and decreased at higher temperatures. QMS detected FSi(CH<sub>3</sub>)<sub>3</sub> as a reaction byproduct instead of HMDS at 150°C. LiF ALD showed self-limiting behavior. Ex situ measurements using X-ray reflectivity (XRR) and spectroscopic ellipsometry (SE) showed a growth rate of 0.5-0.6 Å/cycle, in good agreement with the in situ QCM measurements.</div><div>ALD of lithium ion conducting (AlF3)(LiF)x alloys was also demonstrated using in situ QCM and in situ QMS at reaction temperatures at 150°C A mass gain per sequence of 22 ng/(cm<sup>2</sup> cycle) was obtained from QCM measurements at 150°C. Ex situ measurements using XRR and SE showed a linear growth rate of 0.9 Å/sequence, in good agreement with the in situ QCM measurements. Stoichiometry between AlF<sub>3</sub> and LiF by QCM experiment was calculated to 1:2.8. XPS showed LiF film consist of lithium and fluorine. XPS also showed (AlF<sub>3</sub>)(LiF)x alloy consists of aluminum, lithium and fluorine. Carbon, oxygen, and nitrogen impurities were both below the detection limit of XPS. Grazing incidence X-ray diffraction (GIXRD) observed that LiF and (AlF<sub>3</sub>)(LiF)<sub>x</sub> alloy film have crystalline structures. Inductively coupled plasma mass spectrometry (ICP-MS) and ionic chromatography revealed atomic ratio of Li:F=1:1.1 and Al:Li:F=1:2.7: 5.4 for (AlF<sub>3</sub>)(LiF)<sub>x</sub> alloy film. These atomic ratios were consistent with the calculation from QCM experiments. Finally, lithium ion conductivity (AlF<sub>3</sub>)(LiF)<sub>x</sub> alloy film was measured as σ = 7.5 × 10<sup>-6</sup> S/cm.</div>

A New Method of Wafer Level Plan View TEM Sample Preparation by DualBeam

2008 ◽  
Author(s):  
Hyoung H. Kang ◽  
Michael A. Gribelyuk ◽  
Oliver D. Patterson ◽  
Steven B. Herschbein ◽  
Corey Senowitz
Keyword(s):  
Sample Preparation ◽  
Ex Situ ◽  
Wafer Level ◽  
Cross Sectional ◽  
Plan View ◽  
Manufacturing Line ◽  
Transmission Electron ◽  
Thin Lamella ◽  
Preparation Techniques

Abstract Cross-sectional style transmission electron microscopy (TEM) sample preparation techniques by DualBeam (SEM/FIB) systems are widely used in both laboratory and manufacturing lines with either in-situ or ex-situ lift out methods. By contrast, however, the plan view TEM sample has only been prepared in the laboratory environment, and only after breaking the wafer. This paper introduces a novel methodology for in-line, plan view TEM sample preparation at the 300mm wafer level that does not require breaking the wafer. It also presents the benefit of the technique on electrically short defects. The methodology of thin lamella TEM sample preparation for plan view work in two different tool configurations is also presented. The detailed procedure of thin lamella sample preparation is also described. In-line, full wafer plan view (S)TEM provides a quick turn around solution for defect analysis in the manufacturing line.

PROPUESTA DE CONSERVACIÓN DE TRES ESPECIES MEXICANAS DE PICEA EN PELIGRO DE EXTINCIÓN

2015 ◽  
Vol 38 (3) ◽  
pp. 235 ◽  
Author(s):  
Eduardo Mendoza-Maya ◽  
Judith Espino-Espino ◽  
Carmen Z. Quiñones-Pérez ◽  
Celestino Flores-López ◽  
Christian Wehenkel ◽  
...  
Keyword(s):  
Ex Situ

Picea mexicana Martínez, P. chihuahuana Martínez y P. martinezii Patterson son especies endémicas de México en peligro de extinción. Se presenta una síntesis de su situación actual y una propuesta de manejo para su conservación in situ y ex situ, con base en la diversidad y estructura genética de las poblaciones y la ubicación de las áreas en donde se predice existirá el hábitat climático que les es propicio en el futuro (años 2030, 2060 y 2090; al promediar los modelos Canadiense, Hadley y Geofísica de Fluidos con escenarios de emisiones A y B). Para la conservación in situ se plantea la protección, el incremento de la diversidad genética y la expansión de las tres únicas poblaciones de P. mexicana, las cuatro únicas de P. martinezii y ocho poblaciones designadas prioritarias de las 40 poblaciones de P. chihuahuana, mediante la plantación de individuos originados de otras poblaciones hasta alcanzar un tamaño mínimo de población genéticamente viable (entre 1035 a 3836 individuos). Para la conservación ex situ se propone el establecimiento de poblaciones en sitios fuera del rango de distribución natural de las especies, en donde se ha proyectado que ocurrirá el clima que les es propicio, con al menos 3606 individuos de P. mexicana en el volcán Cofre de Perote, Veracruz; 2431 individuos de P. chihuahuana en el municipio de Guanaceví, Durango; y 3092 individuos de P. martinezii en la región de Tlatlauquitepec, Puebla, con plantas originadas de una mezcla de semillas colectadas de árboles al azar de poblaciones específicas.

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