Hollow Fiber Membrane Bioreactor Research Articles

Zymomonas mobilis immobilization in polymeric membranes for improved resistance to lignocellulose-derived inhibitors in bioethanol fermentation

Immobilized cell hollow fiber membrane bioreactor (ICHFMB) was designed and operated to mitigate the effect of lignocellulose derived inhibitors during fermentation of synthetic lignocellulosic hydrolysate by Zymomonas mobilis. The individual inhibitors – vanillin, syringaldehyde, 5-hydroxymethylfurfural and 4-hydroxy-3-methoxycinnamaldehyde, exhibited toxicity on suspended cells, whereas simultaneous exposure to multiple inhibitors was detrimental for the cells. In contrast, the immobilized cells showed excellent growth and glucose uptake in the presence of these inhibitors, and the microorganisms achieved 95% of the theoretical ethanol yield under highly inhibitory conditions. ICHFMB performance could be improved significantly by increasing the flow rate of the hydrolysate over the membranes, and by increasing the number of membranes, indicating that diffusion through the membranes was an important factor during the fermentation. Z. mobilis showed gradual acclimatization to the presence of inhibitors as they were slowly released from the membrane pores into suspension, and enhanced glucose uptake rate and ethanol productivity. Cell immobilization within the membranes was also found to be very stable as the ICHFMB performance did not deteriorate during 20 consecutive runs under identical conditions. These results indicate that ICHFMB can be promising in lignocellulosic bioethanol production under inhibitory conditions.

Bubble coalescence suppression driven carbon monoxide (CO)-water mass transfer increase by electrolyte addition in a hollow fiber membrane bioreactor (HFMBR) for microbial CO conversion to ethanol

This study investigated the effects of electrolytes (CaCl2, K2HPO4, MgSO4, NaCl, and NH4Cl) on CO mass transfer and ethanol production in a HFMBR. The hollow fiber membranes (HFM) were found to generate tiny gas bubbles; the bubble coalescence was significantly suppressed in electrolyte solution. The volumetric gas-liquid mass transfer coefficients (kLa) increased up to 414% compared to the control. Saturated CO (C∗) decreased as electrolyte concentrations increased. Overall, the maximum mass transfer rate (Rmax) in electrolyte solution ranged from 106% to 339% of the value obtained in water. The electrolyte toxicity on cell growth was tested using Clostridium autoethanogenum. Most electrolytes, except for MgSO4, inhibited cell growth. The HFMBR operation using a medium containing 1% MgSO4 achieved 119% ethanol production compared to that without electrolytes. Finally, a kinetic simulation using the parameters got from the 1% MgSO4 medium predicted a higher ethanol production compared to the control.

Denitrification of Nitric Oxide Using Hollow Fiber Membrane Bioreactor; Effect of Nitrate and Nitric Oxide Loadings on the Reactor Performance and Microbiology

Nitric oxide (NO) removal from a gas stream containing ~500 ppm NO was studied in a hollow fiber membrane (HFM) bioreactor. Compared to other biological NO removal methods the HFM bioreactor achieved NO removal rates that were as good if not better, of up to 92% NO removal, under comparable loadings and reactor size. Results showed that a wastewater stream containing organic carbon can be used as the electron donor to reduce the NO. Hence, combining biological NO treatment with treatment of a wastewater containing organic carbon has may be an effective overall cost-reducing strategy. The effect of different nitrate (NO 3 − ) concentrations on the NO reduction rate was also evaluated, and results showed that NO 3 − does enhance the NO removal rate. The reactor’s performance was studied under six different NO:NO 3 − loading regimes and the NO removal rate as well as the microbial denitrifier community in the reactor was tracked. Specifically, the relevant genes responsible for each denitrification step were tracked during each different NO:NO 3 − loading regime to the reactor. Results showed that the denitrifying microbial community adjust rapidly to changes in the different N loadings, but overall the performance of the reactor is robust and can withstand such variability in terms of NO, NO 3 − and organic carbon removal.

Impact of SRT on the performance of MBRs for the treatment of high strength landfill leachate

This study examines the performance and fouling potential of flat sheet (FS) and hollow fiber (HF) membrane bioreactors (MBRs) during the treatment of high strength landfill leachate under varying solid retention times (SRT = 5–20 days). Mixed-liquor bacterial communities were examined over time using 16S rRNA gene sequence analysis in an attempt to define linkages between the system performance and the microbial community composition. Similarly, biofilm samples were collected at the end of each SRT to characterize the microbial communities that evolved on the surface of the FS and HF membranes. In general, both systems exhibited comparable removal efficiencies that dropped significantly as SRT was decreased down to 5 days. Noticeably, ammonia and nitrite oxidizing bacteria were not detected at the tested SRTs. This suggests that the nitrifiers were not enriched, possibly due to the high organic and ammonium content of the leachate that led to low TN and NH3 removal efficiency. The steady-state fouling rate of both membranes increased linearly with the decrease in SRT at an estimated factor of 1.1 and 1.2 for the FS- and HF-MBR, respectively, when the SRT was reduced from 15 to 10 days and from 10 to 5 days. Similar dominant genera were detected in both MBRs, including Pseudomonas, Aequorivita, Ulvibacter, Taibaiella, and Thermus. Aequorivita, Taibaiella; Thermus were the dominant genera in the biofilms. Hierarchical clustering and non-metric multidimensional scaling revealed that while the mixed liquor communities in the FS-MBR and HF-MBRs were dynamic, they clustered separately. Similarly, biofilm communities on the FS and HF membranes differed in the dynamic bacterial community structure, especially for the FS-MBR; however this was less dynamic than the mixed liquor community.

Application of membrane bioreactor for sulfamethazine-contained wastewater treatment

The presence of antibiotics in wastewater has been widely confirmed. Membrane bioreactor (MBR), as an efficient wastewater treatment technology, has attracted increasing interest in its ability to remove antibiotics in recent years. However, its long-term operation stability and the underlying mechanisms for antibiotics removal are still poorly understood. In this study, a hollow fiber MBR was used to treat low concentration sulfamethazine (SMZ) contained wastewater. The long-term effects of various SMZ concentrations on nutrients removal, SMZ degradation, and sludge characteristics were investigated. During the 244 days operation, the overall SMZ removal efficiency could reach 95.4 ± 4.5% under various SMZ concentrations and hydraulic retention times. The reactor exhibited high chemical oxygen demand and NH4+-N removal efficiencies, which reached 93.0% and 96.2%, respectively. A sludge concentration of 4.1 ± 0.3 g/L was maintained in the system without excess sludge discharge. The dosage of SMZ had obvious effect on sludge characteristics. The contents of extracellular polymeric substances (EPS) in MBR decreased after a long-term operation of the reactor under SMZ pressure. The low sludge concentration and the reduced EPS content were also beneficial for mitigating membrane fouling. Thus, this study provides a low-cost, efficient and simple approach to treat SMZ-contained wastewater.

Automation and control system for fluid dynamic stability in hollow‐fiber membrane bioreactor for cell culture

AbstractBACKGROUNDIn recent years, biochemical and biotechnological engineering has been applied to the culture of human and animal tissue cells, which requires the design, operation and control of complex bioreactors. Hollow fibre membrane bioreactors provide favourable conditions for cellular function and metabolism. To develop bioartificial systems ensuring stable and long‐term operation, fluid dynamics and transport phenomena require careful automation strategies.RESULTSStarting from a crossed hollow‐fiber membrane bioreactor for the culture of complex cell systems configured to operate manually, a 2×2 liquid level/flow‐rate control system is experimentally developed and thoroughly tested for its robustness against liquid level or flow‐rate set‐point changes and disturbances arising from loop interaction. The automation system is shown to be fast for flow‐rate and sufficiently reliable for liquid level (response times of minutes). Limitations are mostly owing to flow‐rate difference constraints and level sensor noise, both originating from cell culture requirements. Prolonged operation (27 days) of the bioreactor in maintaining human hepatocytes in a three‐cell co‐culture system is presented and discussed.CONCLUSIONThe results shown in the present work allow improving the understanding of the dynamic behaviour of a membrane bioreactor for biomedical application and examining the possibility to run the bioreactor under fully automated pre‐set conditions smoothly and for extended periods of time. © 2017 Society of Chemical Industry

Human liver microtissue spheroids in hollow fiber membrane bioreactor

The aim of this work was to create human liver microtissue spheroids metabolically active by using a hollow fiber membrane bioreactor whose design and structural features ensure a uniform microenvironment and adequate oxygenation. Human hepatocyte spheroids with uniform size and shape were formed through self-assembling and cultured into the bioreactor. Adjacent spheroids fused, giving rise to larger microstructures around the fibers forming liver-like tissue, which retained functional features in terms of urea synthesis, albumin production, and diazepam biotransformation up to 25days. The overall data strongly corroborates that within the bioreactor a proper oxygenation and supply of nutrients were provided to the cells ensuring a physiological amount even in the spheroids core. The oxygen uptake rate and the mathematical modelling of the mass transfer directly elucidated that liver microtissue spheroids are not exposed to any oxygen mass transfer limitation. The minimum oxygen concentration reached at the center of multiple spheroids with diameter of 200μm is significantly higher than the one of the perivenous zone in vivo, while for larger microtissues (400μm diameter) the oxygen concentration drops to values that are equal to the maximum concentration found in the liver periportal zone. Both experimental and modelling investigations led to the achievement of significant results in terms of liver cell performance. Indeed, the creation of a permissive microenvironment inside the bioreactor supported the formation and long-term maintenance of functional human liver microtissues.

Oxygen transport in hollow fibre membrane bioreactors for hepatic 3D cell culture: A parametric study

Hepatic cell cultures are exploited for different applications in liver disease studies, drug toxicity testing and bioartificial liver (BAL) devices. Despite the development of various 3D cell culture systems, mass transfer properties and limitations, especially oxygen supply, still remain a controversial topic. In this paper, oxygen transport in a convection-enhanced, crossed-configuration hollow fibre membrane bioreactor hosting hepatocyte spheroids has been investigated through coupled free/porous media flow hydrodynamics and mass transfer modelling using finite-element simulations. Starting from experimental measurements of the oxygen concentration in the bioreactor, a systematic parametric study was performed to evaluate the effect of different parameters – oxygen partial pressure, perfusion rate, hollow fibre spacing, spheroid size, Michaelis-Menten kinetics for oxygen uptake and porosities of the spheroid and the membrane – on dissolved oxygen concentration profile. These parameters were studied in relation to dimensionless groups and variables. Among the operational conditions, oxygen concentration was much more influential than perfusion rate. As for the Michaelis-Menten parameters, oxygen concentration profile inside the spheroids was strongly affected by the maximum consumption rate (Vmax) and weakly dependent on the constant KM. Culturing smaller spheroids minimized the exposure of cells to hypoxic conditions, owing to the short diffusive penetration depth of oxygen especially at low porosities (0.2). An in vivo-like microenvironment in terms of physiological oxygen concentration range was achieved in large spheroids (400µm diameter) at spheroid porosity of 0.47. Membrane porosity also affected the intra-spheroid oxygen concentration and an improvement in oxygen supply to the spheroids could be achieved by reducing the corresponding transfer resistances. The mechanical stress on the spheroid surfaces was found to be within the tolerated ranges. Overall, the most important parameters for optimization of the bioreactor were identified.

Hollow fiber membrane bioreactor affects microbial community and morphology of the DAMO and Anammox co-culture system

Denitrifying anaerobic methane oxidation (DAMO) and Anammox co-culture system was investigated in hollow fiber membrane bioreactor (HfMBR) for the change of microbial community morphology and proportion. NO3−-N and NH4+-N removal rates reached 85.33 and 37.95mg/L/d on 193d. The inoculum microorganisms were flocs and the proportion of DAMO archaea, DAMO bacteria and Anammox bacteria was 11.0, 24.2 and 0.4%, respectively, but it changed to 74.3, 11.8, 5.6% in HfMBR, respectively. Interestingly, microorganisms formed biofilms on fibers surface and the biofilms included two layers: inner layer was thin and dominated by DAMO bacteria and Anammox bacteria; while the outer layer was thick made up of granules with 100–200μm diameter and dominated by DAMO archaea. The spatial distribution of microorganisms in HfMBR was different from simulation results in the literature. Likely, HfMBR changed the interaction between DAMO and Anammox microorganisms, and the reactor configuration was beneficial for DAMO archaea growth.

Investigation of CO2 removal by immobilized carbonic anhydrase enzyme in a hollow‐fiber membrane bioreactor

Gas–liquid membrane contactors are compelling candidate bioreactors for implementing CO2 capture because of large mass transfer rates and liquid–solid interfaces, low pressure drop, low axial dispersion and mixing, modularity, simple scale‐up or scale‐down, and operational suppleness. Binding the carbonic anhydrase (CA) enzyme on the membrane surface adds extra advantages due to the impressive large hydration turnover number and offers an attractive way for CO2 capture. This novel approach to CO2 removal by immobilized CA in a hollow‐fiber membrane bioreactor (HFMB) was investigated via a multiscale steady‐state model, under gas‐filled and partially liquid‐filled membrane pores conditions. The impact of CA loading, buffer acid‐base constant and concentration, membrane wetting, uncatalyzed/catalyzed CO2 hydration in the wetted membrane zone, operating conditions, and cocurrent/countercurrent flow orientation on the HFMB performance was analyzed. The results showed that this low‐cost, green, and environmentally friendly technology could be an appealing alternative to CO2 capture from stationary emissions sources. © 2017 American Institute of Chemical Engineers AIChE J, 63: 2996–3007, 2017

Various Reactor Types for Biodegradation Process

In last few decades, biological treatment of toxic pollutants and industrial wastewater has gained tremendous attention in the scientific community as well as in the industrial arena. Consequently, various kinds of reactor configuration for biodegradation process, starting from the more conventional activated sludge system to highly advanced microbial fuel cell (MFC) or hollow fiber membrane bioreactor, have been reported in the literature. Batch or semi-batch reactors are mainly used for laboratory studies, anaerobic digestion and manufacture of pharmaceuticals; while continuous reactors are often employed for aerobic treatment of municipal and industrial wastes [1]. Two extreme mixing regimes are represented by well stirred tank reactor and plug flow reactors. Intermediate degrees of mixing can be achieved by employing well-stirred reactors in series or by designing plug flow reactors with axial dispersion. The overall model of the reactor can be developed by combining the equations for the hydraulic regime and the kinetics of the reactions [1]. As compared to the suspended culture of free microbial cells, the immobilization process affects the bioreactor performance by providing the retention of active biomass on support particles, flexibility of reactor design and the improved thermal and operational stability [2]. A brief account of major types of bioreactors with their successful application in the biodegradation of wastewaters, especially the phenolic pollutants and effluents of petroleum/oil based industries, is presented in the following sections. A more detail and excellent review is reported by Al-Khalid & El-Naas [3].

Three-dimensional reconstruction of bioactive membranes and pore-scale simulation of enzymatic reactions: The case of lactose hydrolysis

Two-layered hollow-fiber membrane bioreactors containing immobilized enzymes are investigated in this work at mesoscopic and macroscopic scales. Layer-by-layer reconstruction of the membrane in three dimensions is achieved using two different stochastic techniques that draw data only from electron microscopy images of the structure. The reconstructed layers are subsequently used for the prediction of effective transport properties through the numerical solution of the relevant transport equations. The methodology is used for the investigation of hydrolysis of lactose, employing a convective diffusion and reaction macroscopic model. Direct comparison of model predictions with experimental data from the literature reveals a good agreement, provided that one uses the effective transport coefficients that are calculated from the reconstruction process. A parametric investigation of the hydrolysis process and its efficiency was conducted. The three-dimensional reconstructions are also used for the modeling of the hydrolysis of lactose at the pore scale, taking into account mass transport limitations and applying the same hydrolysis kinetics as in the macroscopic model. The agreement was quite satisfactory. Among the advantages of the pore scale approach that is formulated here is its ability to correlate pore structure details with the performance of the lactose hydrolysis process at the inevitable expense of computational resources.

Enhancing productivity for cascade biotransformation of styrene to (S)-vicinal diol with biphasic system in hollow fiber membrane bioreactor.

Biotransformation is a green and useful tool for sustainable and selective chemical synthesis. However, it often suffers from the toxicity and inhibition from organic substrates or products. Here, we established a hollow fiber membrane bioreactor (HFMB)-based aqueous/organic biphasic system, for the first time, to enhance the productivity of a cascade biotransformation with strong substrate toxicity and inhibition. The enantioselective trans-dihydroxylation of styrene to (S)-1-phenyl-1,2-ethanediol, catalyzed by Escherichia coli (SSP1) coexpressing styrene monooxygenase and an epoxide hydrolase, was performed in HFMB with organic solvent in the shell side and aqueous cell suspension in the lumen side. Various organic solvents were investigated, and n-hexadecane was found as the best for the HFMB-based biphasic system. Comparing to other reported biphasic systems assisted by HFMB, our system not only shield much of the substrate toxicity but also deflate the product recovery burden in downstream processing as the majority of styrene stayed in organic phase while the diol product mostly remained in the aqueous phase. The established HFMB-based biphasic system enhanced the production titer to 143mM, being 16-fold higher than the aqueous system and 1.6-fold higher than the traditional dispersive partitioning biphase system. Furthermore, the combination of biphasic system with HFMB prevents the foaming and emulsification, thus reducing the burden in downstream purification. HFMB-based biphasic system could serve as a suitable platform for enhancing the productivity of single-step or cascade biotransformation with toxic substrates to produce useful and valuable chemicals.

Case studies on the physical-chemical parameters' variation during three different purification approaches destined to treat wastewaters from food industry

The paper presents a set of three interconnected case studies on the depuration of food processing wastewaters by using aeration & ozonation and two types of hollow-fiber membrane bioreactor (MBR) approaches. A secondary and more extensive objective derived from the first one is to draw a clearer, broader frame on the variation of physical-chemical parameters during the purification of wastewaters from food industry through different operating modes with the aim of improving the management of water purification process. Chemical oxygen demand (COD), pH, mixed liquor suspended solids (MLSS), total nitrogen, specific nitrogen (NH4+, NO2−, NO3−) total phosphorous, and total surfactants were the measured parameters, and their influence was discussed in order to establish the best operating mode to achieve the purification performances. The integrated air-ozone aeration process applied in the second operating mode lead to a COD decrease by up to 90%, compared to only 75% obtained in a conventional biological activated sludge process. The combined purification process of MBR and ozonation produced an additional COD decrease of 10–15%, and made the Total Surfactants values to comply to the specific legislation.

English

The performance of a hollow-fiber membrane bioreactor (HFBR) (molecular weight cut-off 30 kD, fiber surface area 2050 cm2) containing a culture of hybridoma cells has been investigated. Experimental data were used as basis to develop a model of general application. Concentrations of fundamental nutrients (glucose and glutamine), inhibitory products (ammonium and lactate), and monoclonal antibodies (MAb) against bovine lactoferrin (IgG1) were monitored over time. Exchange of nutrients and products occurred across the capillary surface, whereas cells and MAb remained in the extra-capillary space (ECS). A protein-free culture medium (Hybrimax) with and without antibiotics was used. In both cases, the final MAb concentration was the same; however, antibiotic presence slowed down the time to achieve this concentration. Diffusion assays have been carried out in order to support the development of a mathematical model that describes the performance of the HFBR, including mass transfer and reaction terms. Inhibition by ammonium and lactate has been considered in the kinetics, providing model results consistent with experimental data. Further research with other cell lines and/or culture media will allow to broaden the field of application of this model for general use in HFBR systems.

Control of membrane fouling with the addition of a nanoporous zeolite membrane fouling reducer to the submerged hollow fiber membrane bioreactor

ABSTRACTThe membrane fouling control via the addition of nanoporous zeolite membrane fouling reducer (Z-MFR) to the submerged membrane bioreactor (MBR) was investigated. Using scanning electron microscopy/energy-dispersive X-ray (SEM/EDX) analysis techniques, the characteristics of fouling on a hollow fiber membrane surface were also analyzed. The addition of Z-MFR to the MBR led to the adsorption of foulants and the flocculation of mixed liquor suspended solids (MLSSs), which resulted in substantially enhancing the membrane filterability. The critical flux values obtained from the sewage mixed liquors of 3400 mg L−1 at the effective dosage rate of 0.03 mg Z-MFR mg−1 MLSS was 85 L m−2 h−1 (LMH), which was enhanced by 42%. The transmembrane pressure (TMP) variation under the operating conditions of 30 LMH with 3500 mg MLSS L−1 showed that the addition of Z-MFR extended the time required to reach the critical flux of 0.32 bar by 2.6-fold longer than the control. Thus, due to the hybrid functions of adsorbing foulants and precipitating colloidal substances with the addition of Z-MFR, a decrease in the foulant amount and an improvement of sludge flocculation have been attained simultaneously. As a result, the membrane fouling control was achieved effectively with the addition of the Z-MFR.

Hepatic Differentiation of Human Induced Pluripotent Stem Cells in a Perfused Three-Dimensional Multicompartment Bioreactor.

The hepatic differentiation of human induced pluripotent stem cells (hiPSC) holds great potential for application in regenerative medicine, pharmacological drug screening, and toxicity testing. However, full maturation of hiPSC into functional hepatocytes has not yet been achieved. In this study, we investigated the potential of a dynamic three-dimensional (3D) hollow fiber membrane bioreactor technology to improve the hepatic differentiation of hiPSC in comparison to static two-dimensional (2D) cultures. A total of 100 × 106 hiPSC were seeded into each 3D bioreactor (n = 3). Differentiation into definitive endoderm (DE) was induced by adding activin A, Wnt3a, and sodium butyrate to the culture medium. For further maturation, hepatocyte growth factor and oncostatin M were added. The same differentiation protocol was applied to hiPSC maintained in 2D cultures. Secretion of alpha-fetoprotein (AFP), a marker for DE, was significantly (p < 0.05) higher in 2D cultures, while secretion of albumin, a typical characteristic for mature hepatocytes, was higher after hepatic differentiation of hiPSC in 3D bioreactors. Functional analysis of multiple cytochrome P450 (CYP) isoenzymes showed activity of CYP1A2, CYP2B6, and CYP3A4 in both groups, although at a lower level compared to primary human hepatocytes (PHH). CYP2B6 activities were significantly (p < 0.05) higher in 3D bioreactors compared with 2D cultures, which is in line with results from gene expression. Immunofluorescence staining showed that the majority of cells was positive for albumin, cytokeratin 18 (CK18), and hepatocyte nuclear factor 4-alpha (HNF4A) at the end of the differentiation process. In addition, cytokeratin 19 (CK19) staining revealed the formation of bile duct-like structures in 3D bioreactors similar to native liver tissue. The results indicate a better maturation of hiPSC in the 3D bioreactor system compared to 2D cultures and emphasize the potential of dynamic 3D culture systems in stem cell differentiation approaches for improved formation of differentiated tissue structures.

Human endothelial cells hollow fiber membrane bioreactor as a model of the blood vessel for in vitro studies.

Human endothelial cells are used in experimental models for studying in vitro pathophysiological mechanisms of different diseases. We developed an original bioreactor, which can simulate human blood vessel, with capillary polysulfone membranes covered with the human umbilical vein endothelial cells (HUVECs) and we characterized its properties. The elaborated cell seeding and culturing procedures ensured formation of a confluent cell monolayer on the inside surface of capillaries within 24h of culturing under the shear stress of 6.6 dyn/cm(2). The optimal density of cells to be seeded was 60,000 cells/cm(2). Labeling HUVECs with carboxyfluorescein succinimidyl ester (CFSE) did not influence cells' metabolism. Flow cytometry-based analysis of HUVECs stained with CFSE demonstrated that in a presence of the shear stress cells' proliferation was much inhibited (after 72h proliferation index was equal to 1.9 and 6.2 for cultures with and without shear stress, respectively) and the monolayer was formed mainly due to migration and spreading of cells that were physiologically elongated in a direction of the flow. Monitoring of cells' metabolism showed that HUVECs cultured in a presence of the shear stress preferred anaerobic metabolism and they consumed 1.5 times more glucose and produced 2.3 times more lactate than the cells cultured under static conditions. Daily von Willebrand factor production by HUVECs was near 2 times higher in a presence of the shear stress. The developed model can be used for at least 3days in target studies under conditions mimicking the in vivo state more closely than the static HUVEC cultures.

Fouling control of submerged hollow fibre membrane bioreactor with transverse vibration

The present study further examines the effectiveness of transverse vibration for the fouling control of hollow fibre membranes in a submerged membrane bioreactor (SMBR) with real mixed liquor. The scope of the investigation included both short and long duration tests. The short duration tests incorporated both continuous and intermittent vibration in different concentrations of mixed liquor, and compared among longitudinal vibration, transverse vibration and combined transverse vibration and low aeration. The results indicated that continuous transverse vibration with low frequencies was very effective towards the fouling control, and was more so than longitudinal vibration. Intermittent vibration was somewhat less favourable, but it provided significant energy savings. With intermittent vibration, a short non-vibration time interval of less than 120s was also found to be necessary to prevent irreversible fouling during this time interval when the permeated extraction continued. For the first time we found that transverse vibration can be more effective for fouling control when combined with low aeration due to the turbulence enhancement by the moving bubbles. The long duration tests confirmed that transverse vibration could be effectively used in the SMBR to control the membrane fouling and prolong the membrane filtration period without chemical cleaning, with high removal efficiencies of both organics and nutrients in the reactor. Higher frequencies of transverse vibration produced larger shear stresses on the membrane surface and enhanced the membrane filtration performance, at the same time the risk of fibre breakage also heightened with the increase in periodic stress cycles on the hollow fibres. The characteristics of the biosolids in the reactor were monitored during the long duration tests. The results showed that both soluble microbial products (SMP) and extracellular polymeric substances (EPS) affected the membrane filtration performance under transverse vibration, but SMP was found to be key membrane fouling contributor. Overall, the study demonstrated that transverse membrane vibration is practical and beneficial for fouling control in the SMBR.

Modeling of hydrodynamics in hollow fiber membrane bioreactor for mammalian cells cultivation

The mathematical modelling in CFD-packages are powerfull instrument for design and calculation of any engineering tasks. CFD-package contains the set of programs that allow to model the different objects behavior based on the mathematical lows. ANSYS Fluent are widely used for modelling of biotechnological and chemical-technological processes. This package is convenient to describe their hydrodynamics. As cell cultivation is one of the actual scientific direction in modern biotechnology ANSYS Fluent was used to create the model of hollow fiber membrane bioreactor. The fibers are hollow cylindrical membrane to be used for cell cultivation. The criterion of process effectiveness for cell growth is full filling of the membrane surface by cells in the bioreactor. While the cell growth the fiber permeability is decreased which effects to feed flow through membrane pores. The specific feature of this process is to ensure such feed flow to deliver the optimal nutrition for the cells on the external membrane surface. The velocity distribution inside the fiber and in all bioreactor as a whole has been calculated based on mass an impulse conservation equations taking into account the mathematical model assumptions. The hydrodynamics analysis in hollow fiber membrane bioreactor is described by the three-dimensional model created in ANSYS Fluent. The specific features of one membrane model are considered and for whole bioreactor too.