bluuebunny/crossref_metadata_2025_split huggingface dataset:
Enhanced biological phosphorus removal in a sequencing batch reactor using propionate as the sole carbon source
Authors: Pijuan M. , Saunders A.M. , Guisasola A. , Baeza J.A. , Casas C. , Blackall L.L. 
Published: June 2004

AbstractAn enhanced biological phosphorus removal (EBPR) system was developed in a sequencing batch reactor (SBR) using propionate as the sole carbon source. The microbial community was followed using fluorescence in situ hybridization (FISH) techniques and Candidatus ‘Accumulibacter phosphatis’ were quantified from the start up of the reactor until steady state. A series of SBR cycle studies was performed when 55% of the SBR biomass was Accumulibacter, a confirmed polyphosphate accumulating organism (PAO) and when Candidatus ‘Competibacter phosphatis’, a confirmed glycogen‐accumulating organism (GAO), was essentially undetectable. These experiments evaluated two different carbon sources (propionate and acetate), and in every case, two different P‐release rates were detected. The highest rate took place while there was volatile fatty acid (VFA) in the mixed liquor, and after the VFA was depleted a second P‐release rate was observed. This second rate was very similar to the one detected in experiments performed without added VFA.A kinetic and stoichiometric model developed as a modification of Activated Sludge Model 2 (ASM2) including glycogen economy, was fitted to the experimental profiles. The validation and calibration of this model was carried out with the cycle study experiments performed using both VFAs. The effect of pH from 6.5 to 8.0 on anaerobic P‐release and VFA‐uptake and aerobic P‐uptake was also studied using propionate. The optimal overall working pH was around 7.5. This is the first study of the microbial community involved in EBPR developed with propionate as a sole carbon source along with detailed process performance investigations of the propionate‐utilizing PAOs. © 2003 Wiley Periodicals, Inc.
Reconsidering the use of photosynthetic bacteria for removal of sulfide from wastewater
Authors: Hurse T.J. , Keller J. 
Published: June 2004

AbstractThe feasibility of using photosynthetic sulfide‐oxidizing bacteria to remove sulfide from wastewater in circumstances where axenic cultures are unrealistic has been completely reconsidered on the basis of known ecophysiological data, and the principles of photobioreactor and chemical reactor engineering. This has given rise to the development of two similar treatment concepts relying on biofilms dominated by green sulfur bacteria (GSB) that develop on the exterior of transparent surfaces suspended in the wastewater. The GSB are sustained and selected for by radiant energy in the band 720–780 nm, supplied from within the transparent surface. A model of one of these concepts was constructed and with it the reactor concept was proven. The dependence of sulfide‐removal rate on bulk sulfide concentration has been ascertained. The maximum net areal sulfide removal rate was 2.23 g m−2 day−1 at a bulk sulfide concentration of 16.5 mg L−1 and an incident irradiance of 1.51 W m−2. The system has a demonstrated capacity to mitigate surges in sulfide load, and appears to use much less radiant power than comparable systems. The efficacy with which this energy was used for sulfide removal was 1.47 g day−1 W−1. The biofilm was dominated by GSB, and evidence gathered indicated that other types of phototrophs were not present. © 2003 Wiley Periodicals, Inc.
Toluene removal from waste air using a flat composite membrane bioreactor
Authors: Jacobs Pieter , De Bo Inge , Demeestere Kristof , Verstraete Willy , Van Langenhove Herman 
Published: June 2004

AbstractIn this report, gaseous toluene biodegradation results in a flat composite membrane reactor inoculated with Pseudomonas putida TVA8 are presented. Preliminary abiotic experiments showed that transport of toluene through the membrane was linearly and negatively correlated with the gas residence time (τ). During a 339‐day biofiltration experiment, the influence of gas residence time (2–24 sec) and mass loading rate (Bv; 10–483 g m−3 h−1) on the toluene elimination capacity was investigated. A maximum elimination capacity (ECmax) of 397 g m−3 h−1 was achieved at τ = 24 sec and Bv = 473 g m−3 h−1. Expressed per unit membrane area, the ECm,max was 0.793 g m−2 h−1, which is five times higher than results obtained with other membrane bioreactor experiments in the same range of loading rates. At low gas residence times, reactor performance was limited by mass transfer. Toluene concentration profiles along the membrane were measured for several biotic and abiotic conditions. For inlet concentrations (Cin) up to 1 g m−3, more than 90% was eliminated at 15 cm from the reactor inlet. For Cin > 1.65 g m−3, longer membranes are necessary to obtain these high removal efficiencies. © 2003 Wiley Periodicals, Inc.
Overcoming shear stress of microalgae cultures in sparged photobioreactors
Authors: Barbosa Maria J. , Hadiyanto  , Wijffels René H. 
Published: June 2004

AbstractIn the present work we identified and quantified the effect of hydrodynamic stress on two different microalgae strains,Dunaliella tertiolectaandD. salina, cultivated in bench‐scale bubble columns. The cell death rate constant increased with increasing gas‐entrance velocity at the sparger.Dunaliella salinawas slightly more sensitive thanD. tertiolecta. The critical gas‐entrance velocities were ∼50 and 30 m s−1forD. tertiolectaandD. salina, respectively. The effects of gas‐flow rate, culture height, and nozzle diameter on the death rate constant were also studied. From these results it was concluded that bubble rising and bubble bursting are not responsible for cell death. Regarding nozzle diameter, small nozzles were more detrimental to cells. The bubble formation at the sparger was found to be the main event leading to cell death. © 2003 Wiley Periodicals, Inc.
Analysis of size distribution and areal cell density of ammonia‐oxidizing bacterial microcolonies in relation to substrate microprofiles in biofilms
Authors: Okabe Satoshi , Kindaichi Tomonori , Ito Tsukasa , Satoh Hisashi 
Published: June 2004

AbstractA fine‐scale in situ spatial organization of ammonia‐oxidizing bacteria (AOB) in biofilms was investigated by combining molecular techniques (i.e., fluorescence in situ hybridization (FISH) and 16S rDNA‐cloning analysis) and microelectrode measurements. Important parameters of AOB microcolonies such as size distribution and areal cell density of the microcolonies were determined and correlated with substrate microprofiles in the biofilms. In situ hybridization with a nested 16S rRNA‐targeted oligonucleotide probe set revealed two different populations of AOB, Nitrosomonas europaea‐lineage and Nitrosospira multiformis‐lineage, coexisting in an autotrophic nitrifying biofilm. Nitrosospira formed looser microcolonies, with an areal cell density of 0.51 cells μm−2, which was half of the cell density of Nitrosomonas (1.12 cells μm−2). It is speculated that the formation of looser microcolonies facilitates substrate diffusion into the microcolonies, which might be a survival strategy to low O2 and NH conditions in the biofilm. A long‐term experiment (4‐week cultivation at different substrate C/N ratios) revealed that the size distribution of AOB microcolonies was strongly affected by better substrate supply due to shorter distance from the surface and the presence of organic carbon. The microcolony size was relatively constant throughout the autotrophic nitrifying biofilm, while the size increased by ∼80% toward the depth of the biofilm cultured at the substrate C/N = 1. A short‐term (∼3 h) organic carbon addition experiment showed that the addition of organic carbon created interspecies competition for O2 between AOB and heterotrophic bacteria, which dramatically decreased the in situ NH‐uptake activity of AOB in the surface of the biofilms. This result might explain the spatial distribution of AOB microcolony size in the biofilms cultured at the substrate C/N = 1. These experimental results suggest O2 and organic carbon were the main factors controlling the spatial organization and activity of AOB in biofilms. These findings are significantly important to further improve mathematical models used to describe how the slow‐growing AOB develop their niches in biofilms and how that configuration affects nitrification performance in the biofilm. © 2003 Wiley Periodicals, Inc.
Cephalosporin C production by immobilized Cephalosporium acremonium cells in a repeated batch tower bioreactor
Authors: Cruz Antonio J. G. , Pan Tai , Giordano Roberto C. , Araujo Maria Lucia G. C. , Hokka Carlos O. 
Published: June 2004

AbstractThe industrial production of antibiotics with filamentous fungi is usually carried out in conventional aerated and agitated tank fermentors. Highly viscous non‐Newtonian broths are produced and a compromise must be found between convenient shear stress and adequate oxygen transfer. In this work, cephalosporin C production by bioparticles of immobilized cells of Cephalosporium acremonium ATCC 48272 was studied in a repeated batch tower bioreactor as an alternative to the conventional process. Also, gas‐liquid oxygen transfer volumetric coefficients, kLa, were determined at various air flow‐rates and alumina contents in the bioparticle. The bioparticles were composed of calcium alginate (2.0% w/w), alumina ( < 44 micra), cells, and water. A model describing the cell growth, cephalosporin C production, oxygen, glucose, and sucrose consumption was proposed. To describe the radial variation of oxygen concentration within the pellet, the reaction‐diffusion model forecasting a dead core bioparticle was adopted. The kLa measurements with gel beads prepared with 0.0, 1.0, 1.5, and 2.0% alumina showed that a higher kLa value is attained with 1.5 and 2.0%. An expression relating this coefficient to particle density, liquid density, and air velocity was obtained and further utilized in the simulation of the proposed model. Batch, followed by repeated batch experiments, were accomplished by draining the spent medium, washing with saline solution, and pouring fresh medium into the bioreactor. Results showed that glucose is consumed very quickly, within 24 h, followed by sucrose consumption and cephalosporin C production. Higher productivities were attained during the second batch, as cell concentration was already high, resulting in rapid glucose consumption and an early derepression of cephalosporin C synthesizing enzymes. The model incorporated this improvement predicting higher cephalosporin C productivity. © 2003 Wiley Periodicals, Inc.
Combined in‐fermenter extraction and cross‐flow microfiltration for improved inclusion body processing
Authors: Tin Lee Chew , Morreale Giacomo , Middelberg Anton P. J. 
Published: June 2004

AbstractIn this study we demonstrate a new in‐fermenter chemical extraction procedure that degrades the cell wall of Escherichia coli and releases inclusion bodies (IBs) into the fermentation medium. We then prove that cross‐flow microfiltration can be used to remove 91% of soluble contaminants from the released IBs. The extraction protocol, based on a combination of Triton X‐100, EDTA, and intracellular T7 lysozyme, effectively released most of the intracellular soluble content without solubilising the IBs. Cross‐flow microfiltration using a 0.2 μm ceramic membrane successfully recovered the granulocyte macrophage‐colony stimulating factor (GM‐CSF) IBs with removal of 91% of the soluble contaminants and virtually no loss of IBs to the permeate. The filtration efficiency, in terms of both flux and transmission, was significantly enhanced by in‐fermenter Benzonase® digestion of nucleic acids following chemical extraction. Both the extraction and filtration methods exerted their efficacy directly on a crude fermentation broth, eliminating the need for cell recovery and resuspension in buffer. The processes demonstrated here can all be performed using just a fermenter and a single cross‐flow filtration unit, demonstrating a high level of process intensification. Furthermore, there is considerable scope to also use the microfiltration system to subsequently solubilise the IBs, to separate the denatured protein from cell debris, and to refold the protein using diafiltration. In this way refolded protein can potentially be obtained, in a relatively pure state, using only two unit operations. © 2003 Wiley Periodicals, Inc.
Total Oxidation of Methane and Chlorinated Hydrocarbons on Zirconia Supported A1–xSrxMnO3 Catalysts
Authors: Stephan K. , Hackenberger M. , Kießling D. , Wendt G. 
Published: June 2004

AbstractThe catalytic behavior of ZrO2 and ZrO2 containing 8 mol‐% Y2O3 supported A1–xSrxMnO3 (A = La, didymium) perovskites was studied in the total oxidation of methane, chloromethane and dichloromethane considering catalyst deactivation and byproduct formation. The perovskites are dispersed on the support surface; clusters with a perovskite‐like structure were formed. The supported catalysts are characterized by higher specific surface areas compared with the unsupported ones. Partial substitution of A‐site cations by Sr leads to an enhancement of the catalytic activity in the total oxidation of methane, but not in the total oxidation of chlorinated hydrocarbons (CHC). The catalytic activity of supported and unsupported catalysts is comparable in the total oxidation of methane in spite of the significantly lower perovskite content of the supported catalysts. In the CHC conversion the catalytic activity of the supported catalysts is higher than that of the unsupported ones.
Optimal Production Planning for Chemical Processes under Uncertain Market Conditions
Authors: Li P. , Wendt M. , Wozny G. 
Published: June 2004

AbstractDue to lack of a systematic reliability analysis, intuitive decisions can often be made in production planning under uncertainty. These decisions will lead to either conservative or aggressive production. In this work, we propose a novel analysis and optimization framework to address this problem, with which the relationship between the profitability and reliability of a planned operation can be quantified. By using probabilistic programming, the solution of the problem provides comprehensive information on the economical achievement as a function of the desired confidence level of satisfying process constraints. The feasible region will shrink and the profit will decrease when increasing the confidence level. For complex plant operations under multiple uncertainties, the sources of risk that have the most significant impacts on the profitability can be identified. Through this approach, an optimal as well as reliable decision for operations can be made, from which a suitable compensation between the profit and the probability of constraints violation can be received. The approach is applied to three problems of production planning under uncertainty and various issues in planning these operations are discussed.
Mass Transfer Modeling of SO2 into Large Water Drops
Authors: Alexandrova S. , Marion M. , Lepinasse E. , Saboni A. 
Published: June 2004

AbstractThis article concerns the modeling of the SO2 absorption and desorption by falling drops through air with low to high concentration of sulfur dioxide. In the liquid phase, a model based on local scales, interfacial liquid friction velocity and drop size diameter is used. In the continuous gas phase a more classical model is applied. Data obtained by the modeling of the SO2 absorption and desorption by a single water drop are compared to published experimental results and a fairly good correspondence was found. On the other hand, the model shows that at high gas concentration (> 1 %) the internal resistance to diffusion dominates, while at low gas concentration (< 1000 ppb) the external resistance to diffusion dominates.
Video Microscopy for Fast Screening of Polymerization Catalysts
Authors: Abboud M. , Kallio K. , Reichert K.‐H. 
Published: June 2004

AbstractVideo microscopy has been used as an effective tool for fast screening of six different metallocene/MAO supported catalyst samples. The different techniques employed for supporting the metallocene on silica gels can have an influence on the overall catalyst activity and on the activity of single catalyst particles. The kinetics of gas‐phase polymerization of ethylene with supported metallocene/MAO catalysts can be modeled by using a simple reaction scheme and neglecting mass and heat transport effects.
Examination of External Mass Transport in a Microchannel Reactor by Pressure Variation
Authors: Kölbl A. , Pfeifer P. , Fichtner M. , Kraut M. , Schubert K. , Liauw M.A. , Emig G. 
Published: June 2004

AbstractA variation of total pressure may be used to check for external mass transfer limitation in heterogeneous catalytic experiments. This is particularly interesting for microchannel reactor studies where a variation of flow rate is not suitable. The pressure variation approach is demonstrated for the steam reforming of methanol in a microstructured reactor. The result is verified by another method, viz. the variation of the carrier gas. The two methods are in good agreement. Other implications of a pressure variation in microchannels are discussed.
A Comparison of the Mixing Characteristics in Single‐ and Two‐Phase Grid‐Generated Turbulent Flow Systems
Authors: Moghaddas J.S. , Trägårdh C. , Östergren K. , Revstedt J. 
Published: June 2004

AbstractThe mixing process is studied in grid‐generated turbulent flow for single‐ and bubbly two‐phase flow systems. Concentration and mixing characteristics in the liquid phase are measured with the aid of a PLIF/PLIF arrangement. A nearly isotropic turbulent flow field is generated at the center of the vertical pipe by using a honeycomb, three grids and a contraction. In two‐phase flow experiments, air bubbles were injected into the flow from a rectangular grid, with mesh size M = 6 mm, which is placed midway between two circular grids each with a mesh size of M = 2 mm. For single‐phase flow, the normalized mean concentration cross‐stream profiles have rather similar Gaussian shapes, and the cross‐stream profiles of the normalized root‐mean‐square (RMS) values of concentration were found to be quite similar. Cross‐stream profiles of the mean concentration, for bubbly two‐phase flow, were also found to be quite similar, but they did not have the Gaussian shape of the profiles for single‐phase flow. Almost self‐similar behavior was also found for the RMS values of the concentration in two‐phase systems. The turbulent diffusion coefficient in the liquid phase was also calculated. At the center of the plume, the flow was found to have a periodic coherent structure, probably of vortex shedding character. Observations showed that the period of oscillation is higher in the case of two‐phase flow than in single‐phase flow.
Determination of Kinetics and Equilibria for Adsorption of Water Vapor on Single Zeolite Particles by a Magnetic Suspension Balance
Authors: Kwapinski W. , Tsotsas E. 
Published: June 2004

AbstractIn order to obtain kinetic and equilibrium data for the adsorption of water vapor on zeolite for use in packed bed adsorber simulations, experimental investigations have been conducted on single zeolite particles with the help of a magnetic suspension balance. The objective was, first, to present such data in a form that is accurate enough and as simple as possible for easier application of the packed bed model and, second, to investigate and discuss the potential of the magnetic suspension balance technique, comparing with more conventional methods.
Pulse Jet Cleaning of Textile and Rigid Filter Media – Characteristic Parameters
Authors: Leubner H. , Riebel U. 
Published: June 2004

AbstractTo characterize the pulse cleaning of textile and rigid filter media in technical filter houses and test rigs, by now mainly tank pressure and valve opening time have been used as characteristic parameters. The pressure pulse formed, however, depends on the whole geometry of the plant so that these operation parameters do not allow a comparison between different technical systems. Thus, the question is raised – also for the development of new pulse jet systems – which parameters of a cleaning pulse are decisive for its performance. By knowing these parameters, an experimental setup could be adjusted in a way that it shows the same cleaning behavior like a filter house so that the laboratory filter tests are comparable to technical filter cycles. On a filter test rig which can be used for both textile and rigid filter media as well as on a pilot plant designed for Herding alpha filter candles, experiments concerning the influence of these different parameters on the cleaning behavior were performed. By inserting different orifices into the blow tube and varying the tank pressure and valve opening time, cleaning pulses of great variability were generated and the history of pressure drop over the filter medium or with candles even on the filter surface was recorded. The performance parameters maximum pressure pressure integral and pressure rise velocity of each pressure pulse were determined and compared with the cleaning efficiency achieved. As result of comprehensive regression analyses we found that especially the maximum pressure and the pressure rise velocity during the zero passage of a cleaning pulse are decisive for the cleaning result. The practical conclusion is that pulse jet systems should be optimized with regard to these parameters. The pressure integral however is not a significant performance parameter.
Product Design of Cohesive Powders – Mechanical Properties, Compression and Flow Behavior
Authors: Tomas J. 
Published: June 2004

AbstractThe fundamentals of cohesive powder consolidation and flow behavior are explained using a reasonable combination of particle and continuum mechanics. By the model “stiff particles with soft contacts”, universal models are presented which include the elastic‐plastic and viscoplastic particle contact behavior with adhesion, load‐unload hysteresis and thus energy dissipation, a history‐dependent and a nonlinear adhesion force function. With this as the physical basis, incipient powder consolidation, yield and cohesive steady‐state flow, consolidation and compression functions, compression and preshear works are explained. As an example, the flow properties of an ultrafine limestone powder are shown. These constitutive models are used to evaluate shear cell test results for apparatus design to ensure reliable powder flow. Finally, conclusions are drawn concerning particle stressing, powder handling behavior and product quality assessment in processing industries.
Regio‐ and diastereocontrolled preparative oxidation of methyloctalones by a biomimetic porphyrin catalyst
Authors: Akagah Bernardin , Estour François , Vérité Philippe , Lameiras Pédro , Nour Mohammed , Cavé Christian , Ménager Sabine , Lafont Olivier 
Published: June 2004

AbstractBoth enantiomers of methyloctalone were oxidized by a biomimetic manganese/porphyrin/imidazole catalytic system in order to obtain sufficient amounts of various model metabolites. The double bond proved to be less sensitive than the ring methylenes. Hydroxylation occurred mainly in the allylic position (position 8) and also at positions 7 and 6. In position 8, two diastereomers were obtained while in positions 7 and 6 the reaction was diastereospecific. In the case of position 8 only the oxidation yielded a keto compound. The efficiency of this method for the preparation of functionalized chiral synthons was better than it was for biological pathways. Chirality 16:398–403, 2004. © 2004 Wiley‐Liss, Inc.