Liter Of Reactor Research Articles

Inhibition during Anaerobic Co-Digestion of Aqueous Pyrolysis Liquid from Wastewater Solids and Synthetic Primary Sludge

Pyrolysis can convert wastewater solids into useful byproducts such as pyrolysis gas (py-gas), bio-oil and biochar. However, pyrolysis also yields organic-rich aqueous pyrolysis liquid (APL), which presently has no beneficial use. Autocatalytic pyrolysis can beneficially increase py-gas production and eliminate bio-oil; however, APL is still generated. This study aimed to utilize APLs derived from conventional and autocatalytic wastewater solids pyrolysis as co-digestates to produce biomethane. Results showed that digester performance was not reduced when conventional APL was co-digested. Despite having a lower phenolics concentration, catalyzed APL inhibited methane production more than conventional APL and microbial community analysis revealed a concomitant reduction in acetoclastic Methanosaeta. Long-term (over 500-day) co-digestion of conventional APL with synthetic primary sludge was performed at different APL organic loading rates (OLRs). Acclimation resulted in a doubling of biomass tolerance to APL toxicity. However, at OLRs higher than 0.10 gCOD/Lr-d (COD = chemical oxygen demand, Lr = liter of reactor), methane production was inhibited. In conclusion, conventional APL COD was stoichiometrically converted to methane in quasi steady state, semi-continuous fed co-digesters at OLR ≤ 0.10 gCOD/Lr-d. Undetected organic compounds in the catalyzed APL ostensibly inhibited anaerobic digestion. Strategies such as use of specific acclimated inoculum, addition of biochar to the digester and pretreatment to remove toxicants may improve future APL digestion efforts.

Co-Digestion of Swine Manure and Crude Glycerine: Increasing Glycerine Ratio Results in Preferential Degradation of Labile Compounds

Co-digestion of swine manure and crude glycerine from biodiesel production has been successfully attempted by many authors reporting substantial increments in biogas production. However, the effectiveness of this approach has been questioned recently. The addition of glycerol may cause an improvement in biogas production but at the expense of disturbing the degradation of manure. In the present paper, the organic transformations undergone in the anaerobic digestion of pig manure at increasing amounts of glycerine (2–8 % (v/v)) were analysed using spectroscopy techniques (Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (1H NMR)). An increase in biogas production was observed with the addition of glycerine up to 8 %, resulting in a volumetric production of methane per litre of reactor (Lr) of 1.4 L CH4/Lr d. However, the subsequent failure of the system was observed at this glycerine content due to the inhibitory effect caused by high H2S concentration and foam formation. FTIR and 1H NMR analysis performed on digestate samples showed that the addition of the co-substrate also caused the preferential degradation of glycerine and accumulation of proteins and aliphatic compounds. A post-stabilisation stage was necessary to complete the degradation process. Modifications in organic matter continued under this last stage although in the previous digestion period, a competition for substrate between sulphate reducing bacteria and methanogens was observed.

Increased performance of hydrogen production in microbial electrolysis cells under alkaline conditions

This work reports the first successful enrichment and operation of alkaline bioelectrochemical systems (microbial fuel cells, MFC, and microbial electrolysis cells, MEC). Alkaline (pH=9.3) bioelectrochemical hydrogen production presented better performance (+117%) compared to conventional neutral conditions (2.6 vs 1.2litres of hydrogen gas per litre of reactor per day, LH2·L−1REACTOR·d−1). Pyrosequencing results of the anodic biofilm showed that while Geobacter was mainly detected under conventional neutral conditions, Geoalkalibacter sp. was highly detected in the alkaline MFC (21%) and MEC (48%). This is the first report of a high enrichment of Geoalkalibacter from an anaerobic mixed culture using alkaline conditions in an MEC. Moreover, Alkalibacter sp. was highly present in the anodic biofilm of the alkaline MFC (37%), which would indicate its potentiality as a new exoelectrogen.

Low-temperature anaerobic digestion of swine manure in a plug-flow reactor

A low-temperature (25°C) anaerobic eight-compartment (PF01 to PF08) cascade reactor simulating a plug-flow reactor (PFR) treating pig manure was monitored for a year. The bioreactor was fed at an average loading rate of 2.4±0.2 g of total chemical oxygen demand (TCOD) per litre of reactor per day for a theoretical hydraulic retention time (HRT) of 67±7 d. An average of 79% of TCOD was removed from pig manure (converted into biogas and in sediments), whereas specific methane yields ranging from 397 to 482 NL CH4 kg−1 VS (148.6 to 171.4 NL CH4 kg−1 TCOD) were obtained. After 150 d, fluctuating performances of the process were observed, associated with solids accumulation in the upstream compartments, preventing the complete anaerobic digestion of swine manure in the compartments PF01 to PF04. Low-temperature anaerobic PFR represents an interesting alternative for the treatment of pig manure and recovery of green energy. Further investigations regarding a modified design, with better accumulating solids management, are needed to optimize the performance of this low-temperature PFR treating pig manure.

Biogas production from pear residues using sludge from a wastewater treatment plant digester. Influence of the feed delivery procedure

Clear economic advantages may be obtained from the management of seasonal fruit wastes by codigestion at existing facilities which are working throughout the year with other residues.We have explored the biomethanization of pear residues in a 5L stirred reactor loaded with sludge from the anaerobic digester of a municipal wastewater treatment plant. Different organic loading rates (OLRs) of fruit waste were tested with two delivery procedures: a discontinuous one (fed once a day) and a pseudocontinuous one. For both procedures, as the OLR increases the pH of the digester drops to acidic values and large OLRs may cause the reactor failure. Nevertheless, the pseudocontinuous delivery allows the treatment of more residue, (10.5 versus 6.0g of volatile solids per litre of reactor and day), maintaining the specific biogas production (0.44L of biogas per gram of volatile solids), with some improvement in methane concentration (44% vs 39%).

Produção específica de biogás a partir de manipueira em reator de fase única

O presente artigo mostra um estudo sobre a produção de biogás a partir de manipueira, considerando o volume de um reator de fluxo tubular horizontal de fase única. O objetivo do trabalho foi avaliar a produção de biogás aumentando-se as cargas orgânicas e os volumes de alimentação, o que resultou em redução do tempo de retenção hidráulica (TRH). O reator foi alimentado continuamente, com cargas orgânicas de 1,18; 1,28; 1,57 e 2,68 g DQO L-1rd-1 (gramas de demanda química de oxigênio por litro de reator por dia) em TRHs de 15; 13,0; 8,3; 6,6 dias, respectivamente. As produções de biogás foram de 0,52; 0,41; 0,65 e 0,63 L L-1rd-1, destacando-se que o primeiro TRH avaliado foi o de 13 dias, seguido de 8,3; 6,6 e 15 dias. Do estudo, concluiu-se que, com a diminuição do TRH, ocorre maior produção de biogás por volume de reator. Consequentemente, através da utilização do TRH adequado, pode-se aproveitar melhor o volume do reator, fato que resultará em economia na implantação da tecnologia em indústrias processadoras de mandioca.

New method for selection of hydrogen peroxide adapted bifidobacteria cells using continuous culture and immobilized cell technology

BackgroundOxidative stress can severely compromise viability of bifidobacteria. Exposure of Bifidobacterium cells to oxygen causes accumulation of reactive oxygen species, mainly hydrogen peroxide, leading to cell death. In this study, we tested the suitability of continuous culture under increasing selective pressure combined with immobilized cell technology for the selection of hydrogen peroxide adapted Bifidobacterium cells. Cells of B. longum NCC2705 were immobilized in gellan-xanthan gum gel beads and used to continuously ferment MRS medium containing increasing concentration of H2O2 from 0 to 130 ppm.ResultsAt the beginning of the culture, high cell density of 1013 CFU per litre of reactor was tested. The continuous culture gradually adapted to increasing H2O2 concentrations. However, after increasing the H2O2 concentration to 130 ppm the OD of the culture decreased to 0. Full wash out was prevented by the immobilization of the cells in gel matrix. Hence after stopping the stress, it was possible to re-grow the cells that survived the highest lethal dose of H2O2 and to select two adapted colonies (HPR1 and HPR2) after plating of the culture effluent. In contrast to HPR1, HPR2 showed stable characteristics over at least 70 generations and exhibited also higher tolerance to O2 than non adapted wild type cells. Preliminary characterization of HPR2 was carried out by global genome expression profile analysis. Two genes coding for a protein with unknown function and possessing trans-membrane domains and an ABC-type transporter protein were overexpressed in HPR2 cells compared to wild type cells.ConclusionsOur study showed that continuous culture with cell immobilization is a valid approach for selecting cells adapted to hydrogen peroxide. Elucidation of H2O2 adaptation mechanisms in HPR2 could be helpful to develop oxygen resistant bifidobacteria.

Biological hydrogen production by Clostridium acetobutylicum in an unsaturated flow reactor

A mesophilic unsaturated flow (trickle bed) reactor was designed and tested for H 2 production via fermentation of glucose. The reactor consisted of a column packed with glass beads and inoculated with a pure culture ( Clostridium acetobutylicum ATCC 824). A defined medium containing glucose was fed at a flow rate of 1.6 mL/min (0.096 L/h) into the capped reactor, producing a hydraulic retention time of 2.1 min. Gas-phase H 2 concentrations were constant, averaging 74±3% for all conditions tested. H 2 production rates increased from 89 to 220 mL/h L of reactor when influent glucose concentrations were varied from 1.0 to 10.5 g/L. Specific H 2 production rate ranged from 680 to 1270 mL/g glucose per liter of reactor (total volume). The H 2 yield was 15–27%, based on a theoretical limit by fermentation of 4 moles of H 2 from 1 mole of glucose. The major fermentation by-products in the liquid effluent were acetate and butyrate. The reactor rapidly (within 60–72 h) became clogged with biomass, requiring manual cleaning of the system. In order to make long-term operation of the reactor feasible, biofilm accumulation in the reactor will need to be controlled through some process such as backwashing. These tests using an unsaturated flow reactor demonstrate the feasibility of the process to produce high H 2 gas concentrations in a trickle-bed type of reactor. A likely application of this reactor technology could be H 2 gas recovery from pre-treatment of high carbohydrate-containing wastewaters.

Compact Radial Reactor with a Structured Porous Metal Catalyst for the Conversion of Natural Gas to Synthesis Gas: Experiment and Modeling

To perform the catalytic conversion of natural gas to synthesis gas, a compact radial reactor supplied with a structured porous metal catalyst has been designed. The reactor was tested at normal pressure using natural gas and air. The reactor can operate without preheating of the inlet gas mixture. A novel structured porous metal catalyst was developed on the basis of the 7% Ni/α-Al2O3 commercial catalyst and Ni−Cr powders. The catalyst is characterized by a low hydraulic pressure drop and a high tortuosity coefficient of the regular structure. The coefficient of heat conductivity of the structured catalyst and the coefficient of mass transfer between a gas flow and the catalyst were determined in special experiments. The catalyst temperature and outlet gas concentrations were experimentally investigated with respect to the gas−air flow rate and methane concentration in the mixture. The catalyst temperature drop along the reactor radius was no higher than 230 °C. The maximum catalyst temperature does not exceed 1090 °C for all runs. At volumetric flow rates of the gas mixture of 4000−40 000 h-1 and O2/CH4 ratios of 0.6−0.9, methane is completely converted, and the maximum space time yield (STY) of the reactor is about 1 L of CH4 per second per liter of reactor. A mathematical model for this process was developed. The results of modeling agree well with the experimental data. One possible application of the developed syngas generator in internal combustion engines is discussed.

04/00306 Potential synergies and challenges in refining cellulosic biomass to fuel, chemicals, and power: Wyman, C. E. Biotechnology Progress, 2003, 19, (2), 254–262

The enzymatic hydrolysis of wheat straw was carried out in bi-phasic media prepared with acetate esters and Na-acetate buffer. The volume percentage of the organic chemicals was 75%. The biomass was pretreated in a steam explosion plant at 217°C and for 3 min. A cellulase complex from commercial source was utilised and the experiments were run at 45°C and at constant enzyme to biomass weight ratio (0.06). Biomass loadings ranged from 6.25 to 100 g per litre of reactor. The amount of glucose formed per litre of reactor and hour and the glucose yield (grams of product per gram of biomass) were close to the values attained in pure buffer. The glucose concentration in the aqueous phase was in bi-phasic media much higher than in pure buffer and reached the value of 146 g lH2O−1 during 72 h of saccharification. The results were poorly dependent on the physical–chemical properties of the solvents. Nevertheless, butyl acetate could be slightly preferred to propyl and i-amyl acetate. The use of bi-phasic media did not require stirring rate higher than in pure buffer. The presence of acetate ester traces did not alter markedly the production of ethanol in the fermentation stage, but determined the extension of the lag phase.

Biosaccharification of cellulosic biomass in immiscible solvent–water mixtures

The enzymatic hydrolysis of wheat straw was carried out in bi-phasic media prepared with acetate esters and Na-acetate buffer. The volume percentage of the organic chemicals was 75%. The biomass was pretreated in a steam explosion plant at 217°C and for 3 min. A cellulase complex from commercial source was utilised and the experiments were run at 45°C and at constant enzyme to biomass weight ratio (0.06). Biomass loadings ranged from 6.25 to 100 g per litre of reactor. The amount of glucose formed per litre of reactor and hour and the glucose yield (grams of product per gram of biomass) were close to the values attained in pure buffer. The glucose concentration in the aqueous phase was in bi-phasic media much higher than in pure buffer and reached the value of 146 g lH2O−1 during 72 h of saccharification. The results were poorly dependent on the physical–chemical properties of the solvents. Nevertheless, butyl acetate could be slightly preferred to propyl and i-amyl acetate. The use of bi-phasic media did not require stirring rate higher than in pure buffer. The presence of acetate ester traces did not alter markedly the production of ethanol in the fermentation stage, but determined the extension of the lag phase.

Plasma catalytic reforming of methane

Thermal plasma technology can be efficiently used in the production of hydrogen and hydrogen-rich gases from methane and a variety of fuels. This article describes progress in plasma reforming experiments and calculations of high temperature conversion of methane using heterogeneous processes. The thermal plasma is a highly energetic state of matter that is characterized by extremely high temperatures (several thousand degrees Celsius), and a high degree of dissociation and a substantial degree of ionization. The high temperatures accelerate the reactions involved in the reforming process. Hydrogen-rich gas (40% H 2, 17% CO 2 and 33% N 2, for partial oxidation/water shifting) can be efficiently made in compact plasma reformers. Experiments have been carried out in a small device (2–3 kW) and without the use of efficient heat regeneration. For partial oxidation/water shifting, it was determined that the specific energy consumption in the plasma reforming processes is 16 MJ/kg H 2 with high conversion efficiencies. Larger plasmatrons, better reactor thermal insulation, efficient heat regeneration and improved plasma catalysis could also play a major role in specific energy consumption reduction and increasing the methane conversion. A system has been demonstrated for hydrogen production with low CO content (∼1.5%) with power densities of ∼30 kW (H 2 HHV)/l of reactor, or ∼10 m 3/h H 2 per liter of reactor. Power density should further increase with increased power and improved design.

Anaerobic Biodegradability of the Organic Components of Municipal Solid Wastes (OFMSW)

The aim of this research was to study the anaerobic conversion efficiency of the organic fraction of municipal solid waste (OFMSW). In order to compare and appraise our techniques and respective conversion efficiencies, primary sewage sludge (PSS) assays were also performed. OFMSW has a high cellulose content (32.9% TS) followed by lignin (12.5% TS), protein (9.61% TS), lipids (5.94% TS) and hemicellulose (5.2% TS). PSS is equally rich in lipids (19.8% TS), protein (18.2% TS) and lignin (19.6% TS), followed by cellulose (13.4% TS) and hemicellulose (5.5% TS). Assays were run in CSTRbiodigesters operated at 35°C and 20 days hydraulic retention time (HRT). Three organic loading rates - 1.0, 2.7 and 3.8 OFMSW g VS/Lr.d (gram of volatile solids per liter of reactor per day) - were studied. PSS was assayed only at 1.0 g VS/Lr.d. Concerning the conversion efficiencies, the most important component for the OFMSW anaerobic digestion is cellulose (74.0 - 77.8% conversion), while lipids (70.0 - 80.6% conversion) are the most important for PSS. The biodegradability of the other organic components are also presented and discussed. Some literature data about OFMSW anaerobic digestion processes are discussed in view of the results presented here. The similarities between our results and those of the so-called dry fermentation processes are also discussed in order to evaluate efficiencies of biogas and CH4 production versus volatile solids removal.

Sulfate Reduction Relative to Methane Production in High-Rate Anaerobic Digestion: Microbiological Aspects

In the high-rate anaerobic reactors studied (ca. 10 g of chemical oxygen demand [COD] removed per liter of reactor per day), the sulfate-reducing bacteria (SRB) were poor competitors of methane-producing bacteria (MPB), scavenging only on the order of 10 to 20% of the total electron flow. The relatively noncompetitive nature of the SRB in this type of reactor is in sharp contrast to the tendency of the SRB to dominate in natural environments and in other types of anaerobic digesters. Various factors such as the feedback inhibition of H(2)S on the SRB, iron limitation, the origin of the SRB inocula, biokinetics, and thermodynamics were investigated. The outcome of the SRB-MPB competition under the reactor conditions studied appeared to be particularly determined by two factors. The SRB, as predicted by the V(max)-K(m) kinetics, competed most effectively at low substrate levels (<0.5 g of COD per liter). The MPB, however, appeared to colonize and adhere much more effectively to the polyurethane carrier matrix present in the reactor, thus compensating for the apparent lower growth rates. Even if the reactor was initially allowed to be predominantly colonized by SRB, the MPB could regain dominance.

Cinétique de l'isomérisation du glucose en continu par une enzyme immobilisée dans un réacteur agité

The kinetics of isomerization of D-glucose to D-fructose catalyzed by immobilized glucose isomerase from Bacillus coagulans were studied at 50, 60 and 70°C in a continuous stirred tank reactor. Initial substrate concentrations of 5 to 25% (W/V) were used with 0,043kg of immobilized enzyme per liter of reactor. From preliminary studies on the reactor, it was found that at a stirring speed of 2,25 r/s and a glucose residence time under 3 330s, diffusional interferences were negligible. Different rate models were tested, but only the Michaelis-Menten expression without inhibition adequately described the kinetic data. Non-linear estimations of Km and Vmax were determined at 50, 60 and 70°C respectively. The apparent activation energy obtained had a value of 46 kJ/mol.