Méthodologie d'étude et de modélisation de la déphosphatation d'effluents aqueux

Due to phosphorus impact on water pollution, a P‐recovery process by calcium phosphate precipitation was developed. The reactor process is a fluidized bed in which phosphate precipitates continuously and coats sand grains. The pilot unit can treat synthetic wastewater flow rates ([P] = 50 mg/l) of about 0.1 m3/h. A two‐stage methodology is proposed to understand the physicochemical phenomena. Fluidized bed precipitation modeling involves thermodynamical concepts taking into account the various calcium phosphates that can precipitate vs. operating conditions (PH, [P], [Ca], T). Coating modeling is performed by a first‐order kinetics reaction between fines and sand grains, combined with a network of ideal reactors representing system hydrodynamics.     

Simultaneous heterotrophic nitrification and aerobic denitrification at high initial phenol concentration by isolated bacterium Diaphorobacter sp. PD-7

A strain capable of phenol degradation, heterotrophic nitrification and aerobic denitrification was isolated from activated sludge of coking-plant wastewater ponds under aerobic condition. Based on its morphology, physiology, biochemical analysis and phylogenetic characteristics, the isolate was identified as Diaphorobacter sp. PD-7. Biodegradation tests of phenol showed that the maximum phenol degradation occurred at the late phase of exponential growth stages, with 1400 mg·L-1 phenol completely degraded within 85 h. Diaphorobacter sp. PD-7 accumulated a vast quantity of phenol hydroxylase in this physiological phase, ensuring that the cel s quickly utilize phenol as a sole carbon and energy source. The kinetic behavior of Diaphorobacter sp. PD-7 in batch cultures was investigated over a wide range of initial phenol concentrations (0–1400 mg·L-1) by using the Haldane model, which adequately describes the dynamic behavior of phenol biodegradation by strain Diaphorobacter sp. PD-7. At initial phenol concentration of 1400 mg·L-1, batch experiments (0.25 L flask) of nitrogen removal under aerobic condition gave almost entirely removal of 120.69 mg·L-1 ammonium nitrogen within 75 h, while nitrate nitrogen removal reached 91%within 65 h. Moreover, hydroxylamine oxidase, periplasmic nitrate reductase and nitrite reductase were successful y expressed in the isolate.     

月桂酸酯季铵盐阳离子表面活性剂的生物降解研究

在pH=6.5~7.0、降解温度25~30℃、振荡速率60~75 r.min-1的条件下,研究了月桂酸酯季铵盐阳离子表面活性剂(2-羟基-3-月桂酰氧基丙基)十二烷基二甲基氯化铵(HDAC)在专性好氧菌作用下,不同初始质量浓度、接种量对HDAC降解速率及降解率的影响,提出了HDAC不同质量浓度范围内的降解动力学方程:当HDAC的初始质量浓度600 mg/L时,HDAC对生物降解反应符合零级动力学特征;当HDAC的初始质量浓度为800~1 000 mg/L时,HDAC对生物降解反应符合一级动力学特征。     

Biodegradation of High Strength Phenolic Wastewater in a Modified External Loop Inversed Fluidized Bed Airlift Bioreactor (EIFBAB)

An EIFBAB was modified with a mixed‐tank reactor placed in series to extend the phenol treatability range. Phenol degradation at high concentrations was investigated at recycle rates from the mixed‐tank reactor from 0 to 15 L/h under batch operation. With a total working volume of 10 L, the new setup could handle 3000 mg/L phenol at a comparable volumetric biodegradation rate of 9 mg/L·h at optimized operation of 5 L/h recycle rate, as the 11 mg/L‐h in the original EIFBAB. While the original EIFBAB could not handle phenol concentrations exceeding 3000 mg/L, continuous operation was ascertained in the modified EIFBAB for phenol degradation of up to 5000 mg/L phenol and feed flow rates up to 160 mL/h. The recoverability of the system under shock loading of phenol up to 5000 mg/L was also assessed.     

Combination of Advanced Oxidation and/or Reductive Dehalogenation and Biodegradation for the Decontamination of Waters Contaminated with Chlorinated Organic Compounds

Abstract

The method of decomposition of chlorinated organic substances in contaminated water based upon successive steps of chemical pretreatment of organic compound with a) active radicals (Fenton reaction) and/or with b) reductive dehalogenation on metallic Pd in the presence of zero‐valent iron, followed by aerobic biodegradation using bacteria strain Pandoraea sp. was studied. 4‐chlorophenol was chosen as a model compound. Generally, chlorophenols show limited biodegradability. The average efficiency of biodegradability of 4‐chlorophenol with both free and immobilized cells does not exceed 70% after 42 days of biodegradation, but their intermediates obtained by partial oxidation (products of hydrolytic‐hydroxylation) and/or a product of their partial reductive dechlorination (phenol) show increased biodegradability. To test the efficiency of the method, water exposed to this contaminant was treated in the laboratory in batch conditions. Because the products of partial oxidation and partial reductive dehalogenation of 4‐chlorophenol essentially differ, the main factor studied was the efficiency of biodegradation of 4‐chlorophenol after oxidative or reductive pre‐treatment steps. In comparison with the rate of biodegradation using free cells without application of the pre‐treatment step, the rate of degradation of 4‐chlorophenol by the application of consecutive combination of Fenton reagent and biotreatment was two‐fold. As for the combination of reductive dechlorination pre‐treatment step with consecutive biodegradation, the rate of decontamination of the 4‐chlorophenol was a little bit higher here in comparison with the rate of biotreatment after the pre‐oxidizing step: the remaining concentration of 4‐chlorophenol corresponding to the sampling in 7, 28, and 56 days after the inoculation were 70 mg/L, 12 mg/L, and 1.1 mg/L, respectively, in samples containing the average initial concentration of 126 mg/L of 4‐chlorophenol. Positive results may probably be due to the co‐substrate effect of phenol presented in the samples after the pre‐traetment reductive step. We have shown that both procedures followed with aerobic biodegradation can be considered suitable for removing hazardous chlorinated compounds from contaminated waters. The rate of biodegradation after the application of pre‐treatment procedures was slightly enhanced in comparison with the rate of biodegradation without the application of the pre‐treatment steps. It is evident that the choice of the decontamination pre‐treatment procedure cannot be generalized and will essentially depend upon the type and concentration of target contaminants and on process costs.     

Integrated anaerobic/aerobic biodegradation in an internal airlift loop reactor for phenol wastewater treatment

Anaerobic and aerobic biodegradation were integrated in an internal airlift loop reactor (IALR) by adding porous microbial carriers. In this bioreactor, aerobic activated sludge was suspended in the liquid bulk, while the anaerobic microbes were attached within the core of carriers. The integrated IALR was applied to the treatment of synthetic phenol wastewater. After 50 days’ acclimation according to co-substance strategy, the influent COD decreased from 3,700 mg/L to 400 mg/L (phenol removal rate was over 99%) with the residence time of 24 h. High performance could be achieved under the operation condition of superficial gas flow rate higher than 0.07 cm/s, temperature beyond 15°C and the microbial carrier volume fraction larger than 5%. Integration of anaerobic/aerobic biodegradation in IALR enhanced the synergetic effects between aerobic and anaerobic degradation; therefore, it has great potential in the treatment of phenol wastewater and other wastewater containing hard biodegradable organics.     

Cometabolic Transformation of 2‐Chlorophenol and 4‐Chlorophenol in the Presence of Phenol by Pseudomonas putida

Biotransformation of 2‐chlorophenol (2‐cp) and 4‐chlorophenol (4‐cp) in the presence of phenol by Pseudomonas putida (ATCC 49451) was investigated. Strain ATCC 49451 was unable to utilize 2‐cp and 4‐cp as the sole carbon and energy source. In the presence of phenol as a growth substrate, 2‐cp and 4‐cp could be transformed through cometabolism. It was found, however, that cell growth and phenol degradation were strongly inhibited by the presence of 2‐cp and 4‐cp. A much longer lag phase (19 h versus 3 h) occurred with the mere addition of 40 mg/L 2‐cp and 100 mg/L 4‐cp. Further increase in 2‐cp and 4‐cp concentrations resulted in incomplete transformation: only 80% of the initial 100 mg/L 4cp and 50% of the initial 40 mg/L 2‐cp could be degraded in the presence of 200 mg/L phenol. Interactions between substrates affected cell growth and substrates degradation significantly and both 2‐cp and 4‐cp were toxic to the cells. Kinetic models for cell growth as well as substrate transformation were established to simulate the experimental data. The form of the kinetic models and magnitude of the model parameters (K₂ = 5.62 mg/L > K₃ = 3.57 mg/L; k_d2 = 17.8 mg/L < k_d3 = 51.5 mg/L) indicate that 2‐cp and 4‐cp exhibited different inhibition and toxicity effects on the cells and their degradation capacities. Kinetics also revealed that the toxicity effect of the chlorophenols dominated over the competitive inhibition effect.     

Modélisation de nanofiltration/osmose inverse en tenant compte du facteur de séparations minimale et maximale

Based on theorical analysis of existing models and on experimental observations, a model that allows us to connect the permeate flux tothe intrinsic separation factor takingaccount of the termsof the minimal and maximalseparation factors, was established. The experiments covering a large range of permeate flux (from several 10^?9 μL/m 2.s) to several 10.³ mL/(m 2.s)) permit us todetermine the values of maximal seaparation and minimal separation, as well as the solute transport parameterr for the solutions of sodiumchloride and sodium sulfate.     

Modeling for local dynamic behaviors of phenol biodegradation in bubble columns

A coupled three-dimensional (3-D) model, combining hydrodynamics with biochemical reactions, was developed to simulate the local transient flow patterns and the dynamic behaviors of cell growth and phenol biodegradation by yeast Candida tropicalis in the bubble-column bioreactor, using the computational fluid dynamic (CFD) method. In order to validate this proposed model effectively, the validation of the local hydrodynamic characteristics of the gas-mineral salt solution (gas-liquid) two-phase system, with the phenol concentration of 1200 mg/L, and with the absence of cells, was performed in a square-sectioned bubble column bioreactor using the LDA system and conductivity probe. Furthermore, the validation of phenol biodegradation behaviors by yeast Candida tropicalis at different initial concentrations of phenol and cell was also carried out in the above bubble-column bioreactor. The results indicated that the model simulations had a satisfying agreement with the experimental data. Finally, the local instantaneous flow and phenol biodegradation features including gas holdup, gas velocity, liquid velocity, cell concentration and phenol concentration inside the bioreactor were successfully predicted in different-scale bubble columns by the proposed model. © 2006 American Institute of Chemical Engineers AIChE J, 2006     

Modélisation Mathématique de la Décantation de la Boue Rouge

A good performance of the solid‐liquid unit operation is required for the economical exploitation of the Bayer process. A computational fluid dynamics (CFD) model simulating the operation of the last washing stage mud thickener of a large Canadian alumina plant is presented. The parametric study of the impact of changes in four parameters shows that the diameter of flocculated red mud particles, the feed flow rate and the radius of the feed well are critical parameters for the operation of the thickener.     

Simulation de la distillation catalytique par un nouveau modèle de transfert &#0150; Application à la production d'acétate de méthyle

A catalytic distillation model, based on Maxwel‐Stefan Equations, is presented. In this model, the effective diffusion in porous catalyst is taken into account. Since this model is developed in a commercial environment (ProSim Plus process simulator), particular attention is paid to the solution strategy: robustness and adaptability are of particular importance for the user. The influence of catalyst characteristic, column design, mixture non &#0150; ideality and liquid/vapour interface are discussed. We conclude that an optimum design exists. Reflux ratio and catalyst location are key‐parameters.     

利用生物反应器处理含酚废水

以从农药厂土壤中分离得到的苯酚降解菌为菌种,采用有效容积为6L的自制生物反应器对模拟含酚废水进行生物降解实验,考察在不同曝气量、pH值和苯酚浓度下苯酚降解菌降解苯酚性能的变化。结果表明,在温度为17 ℃、接种量为7%、曝气量为30 L/h、pH值为6～8的条件下,24 h内可使浓度为700 mg/L的苯酚降解率达到99%以上。在苯酚浓度为200～700 mg/L范围内其平均降酚速率随苯酚浓度的增加而增大,最大达29.2 mg/(L·h)。该菌对pH值、初始苯酚浓度的变化不敏感,能适应一定的冲击负荷。     

Enhancement in mineralization of some natural refractory organic compounds by ozonation–aerobic biodegradation

Two schemes, the first involving ozonation followed by final aerobic biodegradation (phase I experiments), and the second involving initial aerobic biodegradation, followed by ozonation and subsequent final aerobic biodegradation (phase II experiments), were examined for enhanced mineralization of refractory model compounds, viz. gallic acid, tannin and lignin. In all cases, and irrespective of the applied scheme, chemical oxygen demand (COD), total organic carbon (TOC), COD/TOC ratio, and specific UV absorbance at 280 nm attributed to the model compounds decreased with application of increasing ozone dose. The residual organic matter remaining after ozonation exhibited enhanced aerobic biodegradability in all cases. Further, in all cases and irrespective of the applied scheme, the overall amount of COD and TOC removed through the combination of ozonation and biodegradation processes increased with increase in ozone dose for all three model compounds, and more than 90% COD removal could be achieved with an ozone dose of 3 mg ozone absorbed per mg initial TOC, as compared with approximately 40% COD removal when no ozone was applied. Treatment by the first scheme resulted in the fraction of starting COD removed through biodegradation decreasing with increase in ozone dose in all cases, while this fraction increased or remained constant during treatment using the second scheme. In the case of tannin and lignin, similar overall COD removal could be achieved at lower ozone doses using scheme II. Due to incorporation of the initial aerobic biodegradation step in scheme II, the ozone requirement for additional mineralization, ie mineralization over and above that achieved by aerobic biodegradation, was also lower than that in scheme I. Copyright © 2005 Society of Chemical Industry     

Biodegradation of phenol at high concentration by a novel bacterium: Gulosibacter sp. YZ4

BACKGROUND: A novel bacterial strain, Gulosibacter sp. YZ4, has been isolated from activated sludge. Its application potential for phenol biodegradation has not yet been reported, therefore, in this study, biodegradation tests using strain YZ4 were executed under different conditions. RESULTS: The strain was identified as a new member of the genus Gulosibacter and nominated as Gulosibacter sp. YZ4. Phenol biodegradation tests showed that strain YZ4 could thoroughly biodegrade 1000 mg L^?1 phenol across a wide temperature range from 10 to 42 °C and pH range 5 to 11. Degradation of 1000 mg L^?1 phenol was not inhibited by the coexistence of p‐cresol or quinoline. During phenol degradation, strain YZ4 excreted both phenol hydroxylase and catechol 1,2‐dioxygenase to efficiently metabolize phenol. At 36 °C, pH 7.5, strain YZ4 could effectively degrade phenol at concentrations as high as 2000 mg L^?1 within 76 h. Haldane's model with the parameters obtained from the experiments could successfully describe the behavior of the phenol biodegradation by the strain YZ4. CONCLUSIONS: The strain YZ4 has a high potential for applications in phenol wastewater treatment in view of its adaptability to temperature and pH fluctuations and great tolerance to other coexistent toxics. Copyright © 2011 Society of Chemical Industry     

Distribution des temps de séjour en écoulement tourbillonnaire annulaire induit par une entrée tangentielle du liquide

In this work, a thorough model for the flow in annular cell provided with various feed systems, based on an experimental determination of the residence time distribution, was presented for values of the Reynolds number in the range 100 to 5000. Using the plug flow model with axial dispersion, followed by a series of perfectly stirred plug-reactors, it was shown that the non-maintained swirling flow induced by a tangential inlet exhibits a very pronounced piston behavior in conjunction with a stirred zone due to the flow inlet/outlet system in the cell. When an axial inlet or an inlet perpendicular to the cell was used, the percentage of the overall reactor volume having a plug flow with respect to the one with a tangential inlet was decreased.     

Anaerobic biodegradation of phenol in sulfide‐rich media

In the refinery industry, the washing processes of middle‐distillates using caustic solutions generate phenol‐ and sulfide‐containing waste streams. The spent caustic liquors generated contain phenols at concentrations higher than 60 g dm^?3(638.3 mmol dm^?3). For sulfur compounds, the average sulfide concentration was 48 g dm^?3(1500 mmol dm^?3) in these streams. The goal of this study was to evaluate the specific impact of phenol and sulfide concentrations towards the phenol‐biodegradation activity of a phenol‐acclimated anaerobic granular sludge. An inhibition model was used to calculate the phenol and sulfide inhibitory concentrations that completely stopped the phenol‐biodegradation activity (IC100). A maximum phenol‐biodegradation activity of 83 µmol g^?1 VSS h^?1 was assessed and the IC100 values were 21.8 mmol dm^?3 and 13.4 mmol dm^?3 for phenol and sulfide respectively. The limitation of the phenol biodegradation flow by phenol inhibition seemed to be related to the more important sensitivity of phenol‐degrading bacteria. The up‐flow anaerobic sludge bed reactor operating in a non‐phenol‐dependent inhibition condition did not present any sensitivity to sulfide concentrations below 9.6 mmol dm^?3. At this residual concentration, the pH and bisulfide ions' concentration might be responsible for the general collapsing of the reactor activity. Copyright © 2004 Society of Chemical Industry     

Caractérisation viscoélastique du comportement d'une membrane thermoplastique et modélisation numérique de thermoformage

In this work, we are interested, on the one hand in the characterization of circular polymeric ABS membrane under biaxial deformation using the bubble inflation technique, on the other hand in modelling and numerical simulation of the thermoforming of ABS materials using the dynamic finite element method. The viscoelastic behaviour of the Lodge model is considered. First, the governing equations for the inflation of a flat circular membrane are solved using a variable‐step‐size‐finite difference method and a modified Levenberg‐Marquardt algorithm to minimize the difference between the calculated and measured inflation pressure. This will determine the material constants embedded within the model used. For dynamic finite elements method, we consider a nonlinear load in air flow which obeys the Redlich‐Kwong equation of state of the real gases. For numerical simulation, the lagrangian formulation together with the assumption of the membrane theory is used. Moreover, the influence of the viscoelastic model on the thickness and on the stress distribution in the thermoforming sheet are analysed for ABS material.     

Analyse Expérimentale et Numérique du Comportement de Membranes Thermoplastiques en ABS et en HIPS dans le Procédé de Thermoformage

In this work, we are interested, on the one hand in the characterization of circular polymeric ABS and HIPS membrane under biaxial deformation using the bubble inflation technique, on the other hand in modelling and numerical simulation of the thermoforming of ABS and HIPS materials using the dynamic finite element method. Hyperelastic models (Mooney‐Rivlin, Ogden) are considered. First, the governing equations for the inflation of a flat circular membrane are solved using a variable‐step‐size‐finite difference method and a modified Levenberg‐Marquardt algorithm to minimize the difference between the calculated and measured inflation pressure. This will determine the material constants embedded within the models used. For numerical simulation, the lagrangian formulation together with the assumption of the membrane theory is used. Moreover, the influence of the hyperalastic model on the thickness and on the stress distribution in the thermoforming sheet are analysed for ABS and HIPS materials.     

Étude d'un procédé de pyrolyse rapide du charbon dans un réacteur cyclone

Experimental results on fast pyrolysis of coal in a steady state pilot reactor at a flowrate of 0.1 kg/h are examined in this article. The pyrolysis reactor is a cyclone. Using such a system it was possible to achieve simultaneously the reaction and the separation of semi-cokes from volatiles produced by pyrolysis. A pump enabled gas recycling on the experimental setup and allowed a good hydrodynamic regime in the reactor. Only gases were recycled, liquids and tars being condensed and recovered. Experiments were carried out on a Lorraine coal (Houve well). From 100 grams of coal, 60 grams of semi-coke, 35 grams of liquids, and 5 grams of gas containing 66% hydrogen and 30% methane were obtained. For the interpretation of results, an experimental kinetics study on coal grain pyrolysis is presented for grains in the range of 2.5 to 20 mm and temperatures between 700 C and 1050 C.     

Dispositif de déposition de couches de suspensions de céramiques appliqué à la stéréolithographie

A system to coat uniform layers of ceramic suspensions has been developed for rapid prototyping applications. The metering system is made of a gas injection nozzle which height, angle of attack and pressure can be adjusted. The coated layer homogeneity and the process reproducibility have been studied. The effect of each parameter on the coated layer thickness has been characterized using a design of experiments approach and a reliable mathematical model is proposed to optimze the coating system.