Dynamic behavior of an internal-loop airlift bioreactor for degradation of waste gas containing toluene

Experiments were performed to study the transient behavior of an internal-loop airlift bioreactor for degradation of toluene in a waste gas stream. The gas pollutant flowed into the reactor from the bottom, and it was then degraded by the microorganisms suspended in the liquid phase. Whenever the operating condition was changed, the gas phase toluene concentration initially increased sharply and the time required to reach a new steady-state concentration was short except when the dissolved oxygen decreased to below about 2K_O, where K_O was Monod constant for oxygen in the microbial kinetics. However, even though the gas phase toluene concentration had already reached a new steady state, the whole system still did not yet reach a new steady state. It took 960-1850 s for the whole system to reach a new steady-state except when the dissolved oxygen decreased to below about 2K_O in this airlift bioreactor. For latter cases, it took 4990-7065 s. Moreover, the time required to reach a new steady state for the whole system increased with increasing input gas phase toluene concentration.A mathematical model was developed to describe the dynamic behavior of toluene degradation in the internal-loop airlift bioreactor. The mathematical model took into account the gas and liquid flow patterns in various sections (e.g. riser, gas-liquid separator, downcomer and bottom), the gas-liquid mass transfer of the reactants and the microbial kinetics. The dynamic behavior of the internal-loop airlift bioreactor simulated by the proposed model showed good agreement with the experimental results.     

Dynamic properties of a continuous stirred tank biofilm bioreactor for aerobic processes

A dynamic analysis of a continuous stirred tank bioreactor with biofilm was performed. The existence of gas, liquid, and biofilm were taken into account. The proposed heterogeneous model of such bioreactor takes into account dynamic biofilm growth and interphase transfer of substrates and biomass for a double‐substrate aerobic process. Simulations were performed to investigate the influence of important process parameters, i.e., toxic substrate concentration in the feed stream, detachment rate coefficient, mean residence time of the liquid and aeration intensity, on dynamic properties of the bioreactor. Dynamic behavior at conditions of anoxia of microorganisms were shown. A method was proposed to reduce bioreactor start‐up time significantly. The paper presents a mathematical model of the bioreactor that uses a discrete model of biofilm growth based on the theory of cellular automata. Dynamics of the bioreactor based on the continuous and discrete biofilm model was compared. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1818–1829, 2017     

CFD simulation and optimization of effective parameters for biomass production in a horizontal tubular loop bioreactor

The focus of the current study was to perform an experimental investigation and computational fluid dynamic (CFD) simulation of flow hydrodynamics in a forced-liquid horizontal tubular loop bioreactor for the production of biomass. The simulations were performed using the FLUENT commercial CFD package, a segregated unsteady solver and a two-phase Eulerian multiphase model. To validate the simulation results, several experiments were performed in a pilot bioreactor. In addition, the design of experiments methodology using a Taguchi orthogonal array (OA) was applied to evaluate the influence of four factors on the hydrodynamic behavior of the bioreactor. The effective parameters considered for optimization were air inlet velocity, liquid inlet velocity, bubble diameter, and viscosity. An L₉ OA was used to conduct the Taguchi experiments to study the significance of these parameters and the possible effects of any two-factor interactions. The optimum conditions and most significant process parameters affecting the hydrodynamic behavior were determined using an analysis of variance model. The results showed that the liquid inlet velocity had the most influence on the air volume fraction in the bioreactor. A subsequent confirmatory test demonstrated that the results were within the confidence interval.     

Continuous solid-state fermentation as affected by substrate flow pattern

The performance of continuous solid state bioreactors having two different solid substrate flow patterns, namely plug flow and completely mixed flow, is quantified for both steady-state and transient operation using a simple mathematical model. The core assumption is that each substrate particle acts as an infinitesimal bioreactor. The residence time distribution of the particles is considered in the formulation of the equations for the mixed-flow bioreactor and the error that results from neglecting it is investigated by comparing the simulation results with those of a completely mixed, continuous bioreactor for submerged liquid fermentation (a chemostat). The model is extended to include autolysis, inter-particle inoculation and contamination. Plug flow is shown to have superior performance when high product concentration is needed, if autolysis or other undesirable late emerging phenomena occur, and when non-sterile fermentation using slow-growing microorganisms is undertaken.     

Modeling,Simulation, and Optimization of Hybrid Fe(II)/Fe(III) Redox Flow Fuel Cell System

The kinetic parameters of ferrous iron oxidation, covering both lag and growth phases at low pH, were determined using a free suspended culture of the bacterium Leptospirillum ferriphilum. A mathematical model was developed to simulate the dynamics of a continuous bioreactor used for operation of a novel hybrid Fe(II)/Fe(III) redox flow fuel cell system. By changing the current load within a predefined range, three runs were performed to predict time‐varying ferrous iron concentration, bacterial cell concentration, and pH as the major output variables of simulation program. The model was experimentally validated through three runs. It was found out that the key variable in dynamic analysis of the bioreactor was the current load applied. To optimize the bioreactor and the fuel cell conditions for a normal‐steady‐state operation, the optimal current profile for a transient phase was determined. A selected optimal policy was also implemented and validated during the mini‐pilot‐scale system experiments. © 2013 American Institute of Chemical Engineers AIChE J, 59: 1844–1854, 2013     

A packed-column bioreactor for phenol degradation: Model and experimental verification

Pseudomonas putida (ATCC 17484) has been grown in a pure culture, slime layer inside a continuous packed-column bioreactor. The bioreactor has been characterized in terms of liquid holdup, dispersion, air stripping, fixed biomass concentration, and degradation rate capabilities. The experimental data has been used to develop a predictive model using mechanistic equations for the operation of packed columns and the biokinetics of pure culture phenol degradation. The liquid holdup, dispersion and liquid-to-air mass transfer coefficients were found to be correlated by power law equations commonly used for packed column absorption and stripping equipment. The microorganisms developed a uniform slime layer over the 3-mm diameter glass spheres, measured to be 200 μm thick. Phenol inlet concentrations of 500 ppm were degraded 100% and at rates up to 1.2 × 10^?3 kg m^?3 s^?1. These results compare favorably with the best biodegradation results reported elsewhere in the literature for other bioreactor designs. The packed-column bioreactor has the advantages of no moving parts and the need for minimum aeration (air fluxes less than 0.001 ms^?1), thereby reducing volatile stripping losses. A computer model of the bioreactor was found to predict accurately the experimental trend in biodegradation capacities and rates with liquid flux. It is shown to be a useful model for studying design parameter changes or for determining scale-up characteristics due to its simplicity and mechanistic basis.     

Process intensification with a hybrid system: A tubular packed bed bioreactor with immobilized activated sludge culture coupled with membrane filtration

Performance of a hybrid system consisting of a tubular bioreactor and a membrane filter was studied for removing carbohydrate and protein. Microporous polyurethane (sponge) was used as the packing medium for immobilization activated sludge culture. The bioreactor was operated in series with a cross flow ultrafiltration system to study the effect of influent flow rate and chemical oxygen demand (COD) concentration on the overall system performance. The removal efficiency in the bioreactor decreased linearly with increase in loading. The decline of removal efficiency at higher loadings was more significant for protein than carbohydrate. Coupling the bioreactor with a membrane separation process increased the overall removal rates and provided a consistent effluent quality. The flux through ultrafiltration membrane did not change significantly even when the bioreactor effluent had high levels of protein. Morphological examination of the packing medium both visually and by SEM showed significant accumulation of organisms on the surface which indicates that biofilm thickness was controlled by diffusion limitations. Advantages of the hybrid system include small footprint, economical packing medium, and space savings by coupling the bioreactor with a membrane filtration process.     

气泡循环流动型膜生物反应器流体力学特性研究

以气升式环流反应器和膜生物反应器为基础,提出气泡循环流动型膜生物反应器的概念.利用气液循环流动减缓膜污染,通过充压渗透的操作方式,降低水处理能耗与设备投资.实验研究了下降管内中空纤维膜填充率对反应器的平均气含率、循环液速等流体力学性能的影响,使用模拟体系考察膜分离性能. 研究结果表明:循环流动的气液两相能够明显缓解膜污染,提高膜渗透通量;利用充压渗透的操作方式可以实现膜分离过程,同时加压操作会导致平均气含率减小,循环液速降低.在理论分析基础上,导出平均气含率、循环液速随操作气速和压强的变化关系.     

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     

PHENOL RECOVERY WITH SLM USING “CYANEX 923”

The study of the phenol separation-concentration process with the hollow fiber supported liquid membrane technology has been performed. Mixtures of kerosene and CYANEX 923 were used as liquid membrane. The extractant CYANEX 923 is characterized by a high phenol selectivity and an extremely low solubility in the aqueous phase. The introduction of CYANEX 923 in the membrane composition decreases the extractant losses from the pores of the support.

The phenol separation and simultaneous concentration process has been checked. The influences of the initial concentration of phenol in the feed solution and sodium hydroxide in the stripping phase and the membrane composition on the separation rate have been investigated in a single-pass mode. The analysis of the membrane composition influence has been performed according to the steady-state mass transfer conservation equation and the associated boundary conditions, leading to the mass transfer parameters of the process     

An NMR Imaging Study of Steady-State and Periodic Operation Modes of a Trickle Bed Reactor

NMR imaging has been applied to study the steady-state and the periodic operations of a functioning trickle bed reactor. It has been revealed that under conditions of the continuous supply of a liquid reagent to the catalyst bed, the bed was mostly filled with the liquid phase and was characterized by the uniform and stationary distribution of a liquid phase, whereas under conditions of the periodic supply of a liquid reagent to the catalyst bed with the same liquid flow velocity the bed was mostly dry and was characterized by a non-stationary distribution of the liquid phase. The oscillations of the liquid phase content within the bed, corresponding to the modulated liquid flow, have been observed. It has been shown that performing the hydrogenation reaction in a trickle bed reactor under conditions of the periodic supply of a liquid reagent to the catalyst bed leads to the intensification of the hydrogenation process. It becomes apparent in the significant increase of the temperature of the catalyst bed as well as in the increase of the conversion degree in the regimes under forced time-varying liquid flow rates in comparison to the steady-state regime of the reactor operation.     

生物反应器制备Vero细胞乙型脑炎纯化疫苗

目的建立利用生物反应器制备Vero细胞乙型脑炎纯化疫苗的新工艺。方法以Vero细胞作为乙型脑炎病毒增殖的细胞基质,使用微载体Cytodex-Ⅰ在15L生物反应器中进行高密度培养,采用2.5～4.5g/L的载体浓度培养乙型脑炎病毒,制备3批纯化乙型脑炎疫苗并进行检定。结果随着微载体浓度的增加,细胞密度升高。采用2.5～4.5g/L微载体培养的病毒收获液的平均滴度为7.38～7.56lgPFU/ml,收获量最高可达到12～15个有效罐体积。制备的3批疫苗各项质量指标均符合《中国药典》三部(2005版)相关要求。结论已建立了15L生物反应器制备Vero细胞乙型脑炎纯化疫苗的新工艺,为进一步放大生产规模奠定了基础。     

喷射环流膜生物反应器水力特性的研究

通过清水试验,确定了喷射环流膜生物反应器的最大吸气量,探讨吸气量、循环水量等因素对气含率、液相循环速度的影响,测定膜组件加入前后的气含率、液相循环速度大小,并与已有的生化反应器进行了比较.结果表明,装置的最大吸气量可达到0.67 m~3·h~(-1)吸气量是影响气含率的主要因素,并且随着吸气量的增加,气含率也随着增加;循环水量是影响液相循环速度的主要因素,随着循环水量的升高循环液速升高;膜组件的加入对气舍率、液相循环速度的影响非常小,与已有的生化反应器比较,JLMBR在水力特性方面具有明显的优势.所得结果可以为该类反应器的放大设计提供借鉴.     

Oxygen transfer in a rotating disk reactor with continuous flow

The oxygen transfer characterized by the liquid phase mass-transfer coefficient (k_L) was investigated in a three-phase rotating disk reactor. Experiments were carried out in steady-state liquid flow conditions because this type of operation is more commonly practised, for example, in wastewater treatment system. The oxygen transfer rate was measured by the sodium sulphite method, but the oxidation was carefully controlled so that the mass transfer was not enhanced by the accompanying chemical reaction. A large portion of oxygen transfer occurred by the convective motion on the free surface of the bulk liquid in the trough, which was more significant when the flow rate was high in the axial direction.     

Hybrid versus global thermostatting in molecular-dynamics simulation of methane-hydrate crystallisation

Molecular-dynamics (MD) simulations have been performed for the growth of a spherical methane-hydrate nano-crystallite, surrounded by a supersaturated water-methane liquid phase, using both a hybrid and globalsystem thermostatting approach. It was found that hybrid thermostatting led to more sluggish growth and the establishment of a radial temperature profile about the spherical hydrate crystallite, in which the growing crystal phase is at a higher temperature than the surrounding liquid phase in the interfacial region, owing to latent-heat dissipation. In addition, Onsager's-hypothesis fluctuation-dissipation analysis of fluctuations in the number of crystal-state water molecules at the interface shows slower growth.     

Startup simulation for a rotating biological contactor

A model for a rotating biological contactor is developed that takes into account the Michaelis-Menten kinetics, the submergence level of the disk, and its rotational speed. The aerobic nature of substrate processing and mass transfer between an aqueous medium and a biofilm are described. The model includes consideration of the erosion of the biofilm by flowing water. The variability of the biofilm thickness along the radius of the disk is taken into account. It is demonstrated how the steady-state characteristics of the bioreactor are reached under different bioreactor conditions.     

STEADY-STATE PERFORMANCE OF A MULTI-STAGE BUBBLE COLUMN BIOREACTOR WITH SUBSTRATE LIMITED MICROBIAL GROWTH

The steady-state performance of a multi-stage bubble column bioreactor in which substrate limited microbial growth proceeds is investigated numerically. The back-flow model for representing longitudinal mixing of the liquid phase and the Monod kinetic equation for cell growth are employed here. The influence of the endogenous metabolism of cells is also taken into account. The concentration profiles of substrate and cells, the substrate conversion, the washout condition and the cell productivity are discussed. The effects of various model parameters, especially the back-flow ratio, on such reactor characteristics are presented as equations or figures. Optimal reactor conditions are determined.     

Microbial Kinetics and Enzymatic Activities in Hybrid Moving‐Bed Biofilm Reactor‐Membrane Bioreactor Systems

A membrane bioreactor (MBR), a hybrid moving‐bed biofilm reactor‐membrane bioreactor (hybrid MBBR‐MBR_a) containing carriers in the anoxic and aerobic compartments, and a hybrid MBBR‐MBR_b containing carriers only in the aerobic zone were used in parallel and compared for treating municipal wastewater. The microbial kinetics and the evolution of the enzymatic activities of α‐glucosidase and acid and alkaline phosphatase as well as the bacterial diversity and bacterial community structure were studied to explain the removal of organic matter and nutrients. The MBR and the hybrid MBBR‐MBR_b showed the highest reduction percentages of chemical oxygen demand. Moreover, the hybrid MBBR‐MBR_b exhibited the highest removal performance of total nitrogen.     

Einsatz von Pervaporation-Bioreaktor-Hybridprozessen in der Biotechnologie

Use of Pervaporation/Bioreactor Hybrid Processes in Biotechnology Pervaporation is a membrane separation process with considerable innovative possibilities in the area of biotechnology. Above all, the combination of bioreactor and pervaporation has potential in the longer term as an alternative to conventional batch processes. This article considers the state of the art of pervaporation/bioreactor hybrid processes. The possible applications of such hybrid processes are discussed and compared with conventional processes. It becomes apparent that the use of pervaporation/bioreactor hybrid processes can avoid product inhibition and greatly enhance the productivity of biotechnological processes.     

搅拌生物反应器的循环时间分布和混合结构模型

利用磁粒子流动跟踪法对搅拌生物反应器的循环时间分布进行测定,并将Rushton径向流桨和两种新型轴向流桨在不同介质粘度和转速下的循环时间分布进行比较和性能评价。建立了单桨搅拌生物反应器的混合结构模型,对循环时间分布数据进行拟合,求得模型参数,进而讨论了不同实验条件下模型参数的变化。结果表明,对于非牛顿、高粘度发酵过程,轴向流桨比Rushton桨具有更好的混合特性。