Packed Column Reactor Research Articles

High-diversity biofilm for the oxidation of sulfide-containing effluents.

In the present work, we describe for the first time the utilization of a complex microbial biofilm for the treatment of sulfide-containing effluents. A non-aerated packed-column reactor was inoculated with anoxic lake sediment and exposed to light. A biofilm developed in the column and showed a stable oxidation performance for several weeks. Microbial species composition was analyzed by microscopy, pigment analysis and a bacterial 16S rRNA gene clone library. Colorless sulfur bacteria, green algae and purple sulfur bacteria were observed microscopically. Pigment composition confirmed the presence of algae and purple sulfur bacteria. The clone library was dominated by alpha-Proteobacteria (mostly Rhodobacter group), followed by gamma-Proteobacteria (Chromatiaceae-like and Thiothrix-like aerobic sulfur oxidizers) and the Cytophaga- Flavobacterium- Bacteroides group. Plastid signatures from algae were also present and a few clones belonged to both the beta- ( Rhodoferax sp., Thiobacillus sp.) and delta-Proteobacteria ( Desulfocapsa sp.) and to the low G+C Gram-positive bacteria (Firmicutes group). The coexistence of aerobic, anaerobic, phototrophic and chemotrophic microorganisms in the biofilm, the species richness found within these metabolic groups (42 operational taxonomic units) and the microdiversity observed within some species could be very important for the long-term functioning and versatility of the reactor.

Statistical sensitivity analysis of packed column reactors for contaminated wastewater

AbstractIn this article we consider the statistical sensitivity analysis of heavy metal biosorption in contaminated wastewater packed column reactors. In particular, the model describes the biosorption phenomenon using the Advection Dispersion Reaction equation under rapid local equilibrium. This allows computer simulation with random input parameters chosen from appropriate probability distributions. In order to have a statistical framework for analyzing the simulated data and assessing input importance, we introduce heteroskedastic and multivariate sensitivity analysis, which extends standard sensitivity analysis. Copyright © 2003 John Wiley & Sons, Ltd.

Continuous atom transfer radical block copolymerization of methacrylates

AbstractA column reactor packed with silica‐gel‐supported copper bromide (CuBr)–hexamethyltriethylenetetramine (HMTETA) was developed for the continuous‐transition–metal‐mediated living/controlled radical polymerization [atom transfer radical polymerization (ATRP)] for homo‐ and block copolymerization of methyl methacrylate (MMA). The reactor showed good stability (>100 h) in both catalyst activity and molecular weight of the poly(methyl methacrylate) (PMMA) produced. The MMA conversion decreased as the flow rate increased. The polymerization in the reactor was in first order with respect to monomer concentration. The molecular weight of the resulting PMMA increased linearly with MMA conversion, exhibiting the characteristic feature of living polymerization. Thus, simply changing the flow rate of MMA, which in turn determined the MMA conversion, readily controlled the molecular weight of PMMA. The block copolymerization of MMA with n‐butyl methacrylate (nBMA) was carried out using two reactors connected in series. The block copolymers were slightly contaminated by PMMA prepolymer from the first column. The molecular weight of the nBMA block could be changed by the flow rate of the nBMA in the second reactor. This packed column reactor technology is feasible for continuously synthesizing polymers or block copolymers with controlled molecular weights that are readily adjustable by changing the monomer flow rates.

Flow injection on-line preconcentration of low levels of Cr(VI) with detection by ETAAS: Comparison of using an open tubular PTFE knotted reactor and a column reactor packed with PTFE beads

A flow injection (FI) on-line sorption preconcentration procedure utilizing a packed column reactor and combined with electrothermal atomic absorption spectrometry (ETAAS) is proposed for the determination of low levels of Cr(VI) in water samples. Polytetrafluoroethylene (PTFE) beads packed in a mini-column is used as sorbent material. The complex formed between Cr(VI) and ammonium pyrrolidine dithiocarbamate (APDC) is sorbed on the PTFE beads, and is subsequently eluted by an air-monosegmented discrete zone of absolute ethanol (35 μl), the analyte being quantified by ETAAS. The preconcentration procedure using the proposed column significantly enhances the preconcentration efficiency as compared with the preconcentration approach incorporating an open tubular PTFE knotted reactor (KR). Comparing the two procedure for equal surface sorption area, the advantages of using a packed column are observed in terms of limit of detection, enrichment factor and retention efficiency. With a preconcentration time of 60 s, and a sample flow rate of 5.0 ml l −1, the enrichment factor (30.1) and the retention efficiency (24.1%) were doubled, yielding a detection limit (3 σ) as low as 8.8 ng l −1. The sample frequency was 16.7 h −1. The concentration efficiency was 8.38 and the precision was 1.05% at 0.5 μg l −1 of Cr(VI). The proposed column has been applied successfully to the analysis of natural water and synthetic seawater. Its performance was verified by the analysis of two certified Cr(VI)-reference materials and by recovery measurements on spiked samples.

Bioenhancement of NAPL pool dissolution: experimental evaluation

Experiments were conducted to quantify nonaqueous phase liquid (NAPL) pool dissolution and its enhancement by in situ biodegradation. The experiments were performed using square cross-section, glass-bead packed column reactors with a small pool of a toluene-in-dodecane mixture (toluene mole fraction, X tol≈0.02 or 0.09). Experimental quasi-steady-state toluene dissolution fluxes were determined using a 14C-carbon mass-balance approach during water flushing with and without biodegradation. The experiments demonstrated a statistically significant bioenhancement of the toluene dissolution flux of up to roughly twofold at average pore water velocities of approximately 0.1 and 1 m/day when the toluene mole fraction was low (≈0.02); however, little or no bioenhancement was observed with the higher mole fraction (≈0.09). Although it cannot be determined conclusively, the weight of evidence based on biomass measurements and model analyses suggests that the reduced bioenhancement for the high mole fraction was due to higher dissolved toluene concentrations, which may have caused toxicity effects. Importantly, even though NAPL dissolution was not bioenhanced in every case, the biodegradation reduced toluene concentrations to low levels in the reactor effluents.

Preparation of crayfish chitin by in situ lactic acid production

Lactic acid production by batch-fed fermentation of deproteinized whey, using immobilized cells of Lactobacillus pentosus-4023 in a spirally wound fibrous-sheet packed-column reactor, has been investigated. This fermentation process has been studied to produce low-cost lactic acid ‘in situ’ and to investigate its direct use for the demineralization of crayfish chitinous fraction (exoskeleton). Chitin obtained by this procedure was chemically and spectrometrically (FT-IR and 13C-NMR) characterized.

Application of equilibrium and mass transfer models to dynamic removal of Cr(VI) ions by Chitin in packed column reactor

The dynamic removal of hexavalent chromium by chitin flakes was studied in a packed column reactor. The values of column parameters were predicted as a function of flow rate, bed depth, particle size and inlet metal ion concentration. On evaluating the breakthrough curves, sorption isotherms were obtained and modelled according to the Langmuir, the Redlich–Peterson and the Freundlich models. Kinetic and mass transfer aspects of the dynamic removal of Cr(VI) ions by chitin were investigated using several mathematical models. Column studies showed a good correlation between the experimental data and the calculated breakthrough curves obtained by the Adams–Bohart or the Wolborska models and the Clark model. The simulation of the whole breakthrough curve was effective with the Clark model, but the breakthrough was best predicted by Adams–Bohart, or related derived models.

Packed column reactor for continuous atom transfer radical polymerization: Methyl methacrylate polymerization using silica gel supported catalyst

A continuous column reactor packed with silica gel supported CuBr-HMTETA catalyst has been successfully developed for ATRP of MMA. The reactor had a good catalytic stability up to 100 h. The MMA conversion decreased with an increasing feeding flow rate. The polymerization kinetics was first order with respect to the monomer. The molecular weight increased linearly with conversion, demonstrating the living character. Possible flow back-mixing and polymer trapping in the pores of silica gel caused some broadening in the molecular weight distribution. This type of packed column reactor is believed to be a significant development for possible commercial exploitation of the ATRP process.

Process development of continuous hydrogen production by Enterobacter aerogenes in a packed column reactor

Process development of continuous hydrogen production by Enterobacter aerogenes in a packed column reactor

Process development of continuous hydrogen production by Enterobacter aerogenes in a packed column reactor

Hydrogen bioproduction from agro-industrial residues by Enterobacter aerogenes in a continuous packed column has been investigated and a complete reactor characterization is presented. Experimental runs carried out at different residence time, liable of interest for industrial application, showed hydrogen yields ranging from 1.36 to 3.02 mmolH2mmol−1glucose or, in other words, from 37.5% to 75% of the theoretical hydrogen yield. A simple kinetic model of cell growth, validated by experimental results and allowing the prediction of biomass concentration profile along the reactor and the optimization of superficial velocity, is suggested. By applying the developed approach to the selected operative conditions, the identification of the optimum superficial velocity v0,opt of about 2.2 cm h−1 corresponding to the maximum hydrogen evolution rate H˙2g,max, was performed.

Integrated Chemical-Biological Treatment of Benzo[a]pyrene

Benzo[a]pyrene of natural and anthropogenic sources is one of the toxic, mutagenic, polycyclic aromatic hydrocarbons (PAHs) listed as priority pollutants. This study focuses on an integrated treatment of benzo[a]pyrene involving sequential chemical oxidation and biological degradation. The objectives are to (1) provide mechanistic details in the ozone-mediated degradation of benzo[a]pyrene in the aqueous phase, (2) test the biodegradability of resultant intermediates, and (3) test the feasibility for the coupled chemical-biological treatment of the five-ring PAH. Batch and packed column reactors were used to examine the degradation pathways of benzo[a]pyrene subject to ozonation in the aqueous phase. After different ozonation times, samples containing reaction intermediates and byproducts from both reactors were collected, identified for organic contents, and further biologically inoculated to determine their biodegradability. The O3-pretreated samples were incubated for 5, 10, 15, and 20 days; afterward biochemical oxygen demand (BOD), chemical oxygen demand (COD), and E. coli toxicity tests were conducted along with qualitative and quantitative determinations of benzo[a]pyrene, intermediates, and reaction products by GC/FID and GC/MS methods. Prevalent intermediates identified at different stages included ring-opened aldehydes, phthalic derivatives, and aliphatics. The degradation of benzo[a]pyrene is primarily initiated via O3-mediated ring-opening, followed by O3 and hydroxyl radical fragmentation, and ultimately brought to complete mineralization primarily via hydroxyl radicals. Intermediates formed during chemical oxidation were biodegradable with a measured first-order rate constant (k0) of 0.18 day-1. The integrated chemical-biological system seems feasible for treating recalcitrant compounds, while pretreatment by chemical oxidation appears useful in promoting soluble intermediates from otherwise highly insoluble, biologically inaccessible benzo[a]pyrene.

Biological Decolorization of Textile Dyestuff by Coriolus Versicolor in a Packed Column Reactor

Biological decolorization of textile dyestuff Everzol Turquoise Blue G, a phthalocyanin type reactive dyestuff, by white-rot fungi Coriolus versicolor MUCL was studied in a packed column reactor. Decolorization performance of fungi immobilized on different support particles such as metal mesh, sponge, stone, wood ash, polyurethane and wood particles were investigated in shake flasks. Metal mesh particles was found to be superior to the other immobilization matrices resulting in 97% decolorization efficiency. The packed column reactor containing fungi immobilized on metal mesh particles was operated in repeated-batch mode. The reactor was loaded 7 times with fresh colored media in every 24 hours. The reactor was gently aerated by a diffuser from the bottom of the column. Environmental conditions were adjusted to T= 28 °C and pH= 4.5–5.0. TOC, glucose and dyestuff concentrations were determined throughout the experiments. During the course of repeated batch operation, decolorization efficiency decreased from 99% to 50% in seven days. Operation of the reactor with 50-100-200 mg l−1 feed dyestuff concentrations resulted in 50% decolorization and 80% TOC removal efficiency in seven days.

Chemical–biological treatment of pyrene

Pyrene of natural and anthropogenic sources is one of the toxic, mutagenic polycyclic-aromatic hydrocarbons (PAHs) listed as priority pollutants. This study focuses on an integrated approach for the degradation of pyrene involving chemical oxidation followed by biological treatment. The objectives were to: (1) provide mechanistic details in the degradation of pyrene subject to ozone treatment; (2) test the combined technique of ozone pretreatment followed by biological degradation; and (3) test a pretreatment column to promote efficient use of chemical oxidants and biodegradability. Batch and packed column reactors were used to examine the degradation pathways of pyrene subject to ozonation in the aqueous phase. After different ozonation times, samples containing reaction intermediates and byproducts from both reactors were collected, identified for organic contents, and further biologically inoculated to determine biodegradability. The O 3-pretreated samples were incubated for 5, 10, 15, and 20 days, after which BOD, COD, and toxicity tests along with qualitative and quantitative GC/FID and GC/MS analyses of pyrene, intermediates, and products were performed. Intermediates identified at different stages included 4,5-phenanthrenedialdehyde, 2,2′,6,6′-biphenyltetraaldehyde, and long-chain aliphatic hydrocarbons, which suggested that the degradation of pyrene was initiated by O 3 via ring cleavage at the 4,5- and 9,10-bonds and that further oxidation ensued via reactions with both O 3 and OH until complete mineralization. Intermediates formed during chemical oxidation were biodegradable with a measured first-order rate constant ( k 0) of 0.24 day −1. The integrated chemical–biological system appears to be feasible for treating recalcitrant compounds, and a chemical pretreatment column is particularly useful in promoting soluble intermediates from otherwise highly insoluble, inaccessible pyrene.

Immobilized lipoxygenase in a packed-bed column bioreactor: continuous oxygenation of linoleic acid.

The continuous oxygenation of linoleic acid (LA) by immobilized lipoxygenase (LOX) was studied. Enzymatic oxidation was carried out in a recirculating packed column reactor using immobilized LOX as the stationary phase and LA as the substrate. The column, when packed with LOX immobilized in either a calcium alginate sol-gel matrix or a phyllosilicate sol-gel matrix, is equivalent to five continuous stirred tank reactors (CSTRs). The reactor cascade was calculated from the residence-time distribution for the reactor. Based on mass-balance calculations, a set of mathematical equations for predicting the concentration of oxygenated product generated in each CSTR was calculated. Product formation in the packed column reactor was simulated and results calculated with the model were compared with the experimental results. The data indicated that product yield (hydroperoxyoctadecadienoic acid, HPOD) increased asymptotically with reaction time. Experimentally, when the bioreactor was packed with calcium alginate sol-gel-immobilized LOX, an initial linear increase in HPOD production with time was observed, but reached a steady state. For the bioreactor packed with phyllosilicate sol-gel-immobilized LOX, initial HPOD production increased more rapidly but reached a lower steady-state concentration. From these data, a simple computer simulation model was developed to determine the process kinetics of this reactor design.

Selective Rhenium Recovery from Spent Reforming Catalysts

Reforming catalysts (0.3% Pt, 0.3% Re) are used extensively in industry for the improvement of the octane number of fuels. After deactivation the catalysts are treated for the recovery of Pt and Re. The aim of this study was to simplify the conventional recovery process by the application of a slight alkali solution (NaHCO3) for the selective dissolution of Re. The process was tested in batch and packed column reactors with crushed and uncrushed catalyst extrudes. The influence on the reaction yield of NaHCO3 concentration, pH, temperature and space velocity was examined and the optimum conditions were determined. The Re dissolution process seemed to follow first-order kinetics, and the recovery yield was up to 97% for crushed and up to 87% for uncrushed catalyst samples.

A novel entrapping matrix for yeast-catalyzed ethanol fermentation

Saccharomyces cerevisiae cells were immobilized by cell suspension homogenization with a soluble prepolymeric matrix, forming insoluble polymer entrapped homogeneously distributed cells. The fermentation capacity of this system was found to be maximal at 30°C and relatively pH insensitive. A packed column reactor was used to test this biocatalyst's operational sensitivity to key fermentation variables. The results obtained as well as the characteristics of the polymer, prepared by an epoxy resin and diaminopolyethylene oxide polymerization, present this method as a good choice for ethanol production.

Comparison of Different Types of Immunoaffinity Reactors in an Electrochemical Flow Injection Immunoanalysis System Developed for Residue Analysis

A comparison of different types of immunoreactors for a flow injection immunoanalysis (FIIA) system is presented. The use of the FIIA system was demonstrated here with the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). The hardware system centers around the immunoreactor. In the preferred reactor set-up, a column is filled with protein G-coated porous beads serving as the affinity matrix for the antibody. In the 2,4-D assay a 2,4-D-alkaline phosphatase conjugate competes with the analyte in the sample for binding to the anti-2,4-D antibody. Subsequently p-aminophenol, generated from the enzymatic reaction with p-aminophenyl phosphate, is detected at ±150mV at a carbon working electrode versus Ag/AgCl. The immunoreactor allows for more than 150 measurements. The fully automated assay procedure needs 15min only for one measurement. For 2,4-D the working range for the determination in water samples was between 1 and 1000 μg/L. Results obtained with the packed column reactor are compared to glassy capillary reactors and miniaturized silicon chip reactors used in previous studies.

Simultaneous Biosorption of Chromium(VI) and Copper(II) on Rhizopus Arrhizus in Packed Column Reactor: Application of the Competitive Freundlich Mode

The simultaneous biosorption of Cr(VI) and Cu(II) on free Rhizopus arrhizus in a packed column operated in the continuous mode was investigated and compared to the single metal ion situation. The breakthrough curves were measured as a function of feed flow rate, feed pH, and different combinations of metal ion concentrations in the feed solutions. Column competitive biosorption data were evaluated in terms the maximum (equilibrium) capacity of the column, the amount of metal loading on the R. arrhizus surface, the adsorption yield, and the total adsorption yield. In the single-ion situation the adsorption isotherms were developed for optimum conditions, and it was seen that the adsorption equilibrium data fit the noncompetitive Freundlich model. For the multicomponent adsorption equilibrium the competitive adsorption isotherms were also developed. The competitive Freundlich model for binary metal mixtures represented most the column adsorption equilibrium data of Cr(VI) and Cu(II) on R. arrhizus satisfactorily.

The effect of bacterial injury on toluene degradation and respiration rates in vapor phase bioreactors

The effects of prolonged toluene exposure and degradation on bacterial cultures of Pseudomonas putida 54G were investigated in three reactor systems: a batch suspended culture system, a bench-scale flat plate biofilm reactor, and a bench-scale packed column reactor. Humidified air containing 150 ppmv (toluene limiting) to 750 ppmv (oxygen limiting) toluene vapor was the sole source of carbon and energy supplied to these systems. Results from the suspended batch culture experiments were used to develop rate expressions and kinetic parameters for loss of culturability and of toluene degradative capacity. Experiments in the flat plate reactor were carried out to examine the effects of injury on biofilm structure and function. The packed column studies were performed under conditions relevant to field application, and confirmed results from the other two studies - that decreased culturability on toluene media correlated with decreased specific toluene degradation rate, particularly at higher toluene concentration.

The effect of bacterial injury on toluene degradation and respiration rates in vapor phase bioreactors

The effects of prolonged toluene exposure and degradation on bacterial cultures of Pseudomonas putida 54G were investigated in three reactor systems: a batch suspended culture system, a bench-scale flat plate biofilm reactor, and a bench-scale packed column reactor. Humidified air containing 150 ppmv (toluene limiting) to 750 ppmv (oxygen limiting) toluene vapor was the sole source of carbon and energy supplied to these systems. Results from the suspended batch culture experiments were used to develop rate expressions and kinetic parameters for loss of culturability and of toluene degradative capacity. Experiments in the flat plate reactor were carried out to examine the effects of injury on biofilm structure and function. The packed column studies were performed under conditions relevant to field application, and confirmed results from the other two studies - that decreased culturability on toluene media correlated with decreased specific toluene degradation rate, particularly at higher toluene concentration.