Hollow Fiber Membrane Bioreactor Research Articles

Biological treatment and thickening with a hollow fibre membrane bioreactor

Aerobic operation of an immersed hollow fibre membrane bioreactor, treating municipal wastewater supplemented with molasses solution, has been studied across mixed liquor suspended solids (MLSS) concentrations between 8 and 32 g L−1, the higher concentrations being normally associated with thickening operations. Only a marginal loss in membrane permeability was noted between 8 and 18 g L−1 when operation was conducted without clogging. The sustainable operational flux attainable above 18 g L−1 was highly dependent upon both the MLSS concentration and the state of the membrane. A temperature-corrected flux of 28 L m−2 h−1 (LMH) was sustained for 18 h at an MLSS of 8 g L−1 using membranes close to initial their virgin-state permeability. This value decreased to around 14 LMH at 20 g L−1 and 5 LMH at 32 g L−1 MLSS for an aged membrane whose permeability had been recovered following clogging. Below the threshold flux operation without significant clogging was possible, such that the membrane permeability could be recovered with a chemically enhanced backflush (CEB). Above this flux clogging took place at a rate of around 7–14 g solids per m2 membrane per m3 permeate volume passed irrespective of the MLSS concentration. The permeability of the unclogged membrane was depressed and could not be recovered using a standard CEB, indicative of irrecoverable pore clogging. The outcomes corroborated previously reported observations concerning the deleterious long-term impacts of clogging, and confirmed the critical importance of operation at a sustainable flux value.

An immersed hollow fiber membrane bioreactor for enhanced biotransformation of indene to cis-indandiol using Pseudomonas putida

An immersed hollow fiber membrane bioreactor (IHFMB) was fabricated for production of pharmaceutical intermediates cis-indandiol from indene by Pseudomonas putida ATCC 55687. At 2–6g/L indene, significant increase of 160–400%, corresponding to 240–400mg/L of cis-indandiol was achieved as compared to that obtained from suspension culture bioreactors (SCB). The IHFMB volumetric productivity of 10.1–12.9mg/(Lh) and molar yield of 0.050–0.093mol/mol indene was also higher than the 4.3–8.3mg/(Lh) and 0.01–0.030mol/mol indene, respectively, in the SCB. The hollow fiber membranes in the IHFMB facilitated a more effective biotransformation through reactant sequestration and cell immobilization, with equal contribution at low indene concentrations, albeit a lower contribution by the latter at 6g/L indene. The performance of the IHFMB was further improved by process optimization and the highest product titer of 487mg/L, overall volumetric productivity of 24.6mg/(Lh) and molar yield of 0.126mol/mol indene were achieved with a module comprising 28 membranes (168cm2/150mL working volume) at a medium circulation rate of 5mL/min and aeration rate of 0.5vvm. Reusability of the membranes has also been successfully demonstrated through 5 successive operations of batch biotransformation.

Biomass properties and permeability in an immersed hollow fibre membrane bioreactor at high sludge concentrations.

This study aimed to investigate the influence of biomass properties and high mixed liquor suspended solids (MLSS) concentrations on membrane permeability in a pilot-scale hollow fibre membrane bioreactor treating domestic wastewater. Auxiliary molasses solution was added to maintain system operation at constant food-to-microorganisms ratio (F/M = 0.13). Various physicochemical and biological biomass parameters were measured throughout the trial, comprising pre-thickening, thickening and post-thickening periods with reference to the sludge concentration and with aerobic biotreatment continuing throughout. Correlations between dynamic changes in biomass characteristics and membrane permeability decline as well as permeability recovery were further assessed by statistical analyses. Results showed the MLSS concentration to exert the greatest influence on sustainable membrane permeability, with a weaker correlation with particle size distribution. The strong dependence of absolute recovered permeability on wet accumulated solids (WACS) concentration, or clogging propensity, revealed clogging to deleteriously affect membrane permeability decline and recovery (from mechanical declogging and chemical cleaning), with WACS levels increasing with increasing MLSS. Evidence from the study indicated clogging may permanently reduce membrane permeability post declogging and chemical cleaning, corroborating previously reported findings.

Study the Effect of Temperature on the Performance of Hollow Fiber Membrane Bioreactor in Wastewater Treatment

A membrane bioreactor (MBR) is one of the modifications to the conventional activated sludge process, since it is the combination of a membrane module and a bioreactor. In the present study, 100 liters lab-scale aerobic MBR was seeded with 1.5 Liter activated sludge and municipal wastewater from AL-Rustumiya municipal wastewater treatment station, two hollow fibers sample (MI,MII) manufactured in the University of Technology/ Chemical Engineering Department, were used as biomembranes. Trans membrane pressure TMP was studied and it was found that the optimum value of TMP was 10 cm Hg vacuum which gave optimum effluent flux 400 ml/hr for MI and 350 ml/hr for MII. The experimental work involves the effect of temperature 25, 35, 45°C on the performance of the MBR fibers sample (MI, MII) and its effect on biomass growth and removal efficiency of the COD, BOD. Both samples show good performance in 25°C.

Kinetics modeling of two phase biodegradation in a hollow fiber membrane bioreactor

A hollow fiber membrane bioreactor (HFMB) was used for two-phase biodegradation of phenol directly from wastewater. In a non-dispersive approach, phenol was extracted from the wastewater to 2-undecanone, and concomitantly back-extracted into the cell culture medium for biodegradation by suspended cells of Pseudomonas putida ATCC 11172. Cell growth in the HFMB was characterized by the absence of lag phase, high cell growth and biodegradation rates. For example, 1000mg/L phenol was metabolized within 28h, with specific growth rates and average biodegradation rates of 0.51h−1 and 59mg/L-h, respectively. A kinetics model based on steady state mass transfer and Haldane growth kinetics was formulated to examine the mass transfer and biodegradation of phenol in the HFMB. The model described the experimental data with reasonable accuracy and the overall mass transfer coefficient on the shell and the tube sides were estimated using empirical correlations as 3.83×10−8 and 1.26×10−6m/s, respectively. Phenol diffusion through the shell side boundary layer was the rate-limiting step. The model indicated that about 18% of the biomass in the HFMB was present on the surfaces as biofilms and the biodegradation kinetics of the biofilms was same as that of the suspended cells. Model simulations were carried out to examine the effects of various operating conditions on bioreactor performance, and HFMB performance improved significantly by increasing shell side flow rate.

Recent advances in the analysis of nanotube-reinforced polymeric biomaterials

AbstractConventional experimental or computational techniques are often inadequate for the analysis and development of nanocomposite-based materials as they are tedious (e.g., experimental methods) or are unsuitable to capture the properties of these novel materials (e.g., conventional computational techniques), thereby requiring multiscale computational strategies. During the last 5 years, major developments were made by the authors on the formulation and implementation of multiscale computational models, using atomistic simulation and micro-mechanics-based techniques, to study the mechanical and thermal behavior of nanocomposite-based materials. In this article, the advances made in the computational analysis of nanocomposites for tissue engineering applications (e.g., scaffolds and bioreactors) would be discussed. The material properties of the nanocomposites in the lower scales were determined using molecular dynamics, and were then transferred to the macroscale using various homogenization techniques. Also in this article, the authors discuss the development of a theory of mixture-based finite element model for nutrient flow in a hollow fiber membrane bioreactor and the use of computational tools to improve the efficiency of the bioreactor.

Removal of nitric oxide from simulated flue gas via denitrification in a hollow-fiber membrane bioreactor

A hollow-fiber membrane bioreactor (HMBR) was studied for its ability to treat nitric oxide (NO) from simulated flue gas. The HMBR was operated for 9 months and showed a maximum elimination capacity of 702 mg NO/(m2day) with a removal efficiency of 86% (gas residence time of 30 sec, inlet NO concentration of 2680 mg/m3, pH 8). Varying operation parameters were tested to determine the stability and response of the HMBR. Both the inlet NO concentration and gas residence time influenced the removal of NO in the HMBR. NO elimination capacity increased with an increase in inlet NO concentration or a shortening of gas residence time. Higher removal efficiency of NO was obtained at a longer gas residence time or a lower inlet NO concentration. Microbial communities of the HMBR were sensitive to the variation in pH value and alkalescence corresponding to an optimum pH value of 8. In addition, NO elimination capacity and removal efficiency were inversely proportional to the inlet oxygen concentration. Sulfur dioxide had no great influence on elimination capacity and removal efficiency of NO. Product analysis was performed to study N2O and N2 production and confirmed that the majority of the microorganisms were denitrifying bacteria in the HMBR. Compared to other bioreactors treating NO, this study showed that the denitrifying HMBR was a good option for the removal of NO.

Comparative assessment of a biofilter, a biotrickling filter and a hollow fiber membrane bioreactor for odor treatment in wastewater treatment plants

A low abatement efficiency for the hydrophobic fraction of odorous emissions and a high footprint are often pointed out as the major drawbacks of conventional biotechnologies for odor treatment. In this work, two conventional biotechnologies (a compost-based biofilter, BF, and a biotrickling filter, BTF), and a hollow-fiber membrane bioreactor (HF-MBR) were comparatively evaluated in terms of odor abatement potential and pressure drop (ΔP) at empty bed residence times (EBRTs) ranging from 4 to 84 s, during the treatment of methyl-mercaptan, toluene, alpha-pinene and hexane at trace level concentrations (0.75–4.9 mg m−3). High removal efficiencies (RE > 90% regardless of the air pollutant) were recorded in the BF at EBRTs ≥ 8 s, although the high ΔP across the packed bed limited its cost-effective operation to EBRTs > 19 s. A complete methyl-mercaptan, toluene and alpha-pinene removal was recorded in the BTF at EBRTs ≥ 4 s and ΔP lower than 33 mmH2O (∼611 Pa mbed−1), whereas slightly lower REs were observed for hexane (∼88%). The HF-MBR completely removed methyl-mercaptan and toluene at all EBRTs tested, but exhibited an unstable alpha-pinene removal performance as a result of biomass accumulation and a low hexane abatement efficiency. Thus, a periodical membrane-cleaning procedure was required to ensure a steady abatement performance. Finally, a high bacterial diversity was observed in the three bioreactors in spite of the low carbon source spectrum present in the air emission.

Multiphase modelling of the influence of fluid flow and chemical concentration on tissue growth in a hollow fibre membrane bioreactor

A 2D model is developed for fluid flow, mass transport and cell distribution in a hollow fibre membrane bioreactor. The geometry of the modelling region is simplified by excluding the exit ports at either end and focusing on the upper half of the central section of the bioreactor. Cells are seeded on a porous scaffold throughout the extracapillary space (ECS), and fluid pumped through the bioreactor via the lumen inlet and/or exit ports. In the fibre lumen and porous fibre wall, flow is described using Stokes and Darcy governing equations, respectively, while in the ECS porous mixture theory is used to model the cells, culture medium and scaffold. Reaction-advection-diffusion equations govern the concentration of a solute of interest in each region. The governing equations are reduced by exploiting the small aspect ratio of the bioreactor. This yields a coupled system for the cell volume fraction, solute concentration and ECS water pressure which is solved numerically for a variety of experimentally relevant case studies. The model is used to identify different regimes of cell behaviour, and results indicate how the flow rate can be controlled experimentally to generate a uniform cell distribution under regimes relevant to nutrient- and/or chemotactic-driven behaviours.

Two-phase biodegradation of phenol in trioctylphosphine oxide impregnated hollow fiber membrane bioreactor

A hollow fiber membrane bioreactor using trioctylphosphine oxide (TOPO) impregnated in polypropylene hollow fiber membranes was developed for two-phase biodegradation of phenol using Pseudomonas putida ATCC 11172. Scanning electron microscopy revealed white deposits of TOPO impregnated non-uniformly within the cross sections and surfaces of the membranes. The extractant impregnated membranes exhibited high adsorption capacity and rates, whereas biodegradation of 800–2500mg/L phenol at 200mL volume in the extractant impregnated hollow fiber membrane bioreactor (EIHFMB) was characterized by high cell growth and biodegradation rates. For example, 1000mg/L phenol was completely degraded within 12h at a specific growth rate of 0.73h−1 while the biomass yield and average biodegradation rate were 0.31g/g and 86mg/Lh, respectively. The biodegradation capacity and rate in the EIHFMB were improved by increasing the effective length of the fibers by 50%, as demonstrated during the biodegradation of 3000mg/L phenol. The adsorption/desorption rates were also enhanced with increasing aqueous phase flow rate. EIHFMB performance remained unchanged over 400h of operation under various operating conditions suggesting the stability of TOPO impregnation within the membrane. These results indicate the use of EIHFMB as a promising technology in solvent-free two-phase biodegradation of phenolic compounds.

Hollow-fiber membrane bioreactor for the treatment of high-strength landfill leachate

Performance assessment of membrane bioreactor (MBR) technology for the treatability of high-strength landfill leachate is relatively limited or lacking. This study examines the feasibility of treating high-strength landfill leachate using a hollow-fiber MBR. For this purpose, a laboratory-scale MBR was constructed and operated to treat leachate with a chemical oxygen demand (COD) of 9000-11,000 mg/l, a 5-day biochemical oxygen demand (BOD5) of 4000-6,000 mg/l, volatile suspended solids (VSS) of 300-500 mg/l, total nitrogen (TN) of 2000-6000 mg/l, and an ammonia-nitrogen (NH3-N) of 1800-4000 mg/l. VSS was used with the BOD and COD data to simulate the biological activity in the activated sludge. Removal efficiencies > 95-99% for BOD5, VSS, TN and NH3-N were attained. The coupled experimental and simulation results contribute in filling a gap in managing high-strength landfill leachate and providing guidelines for corresponding MBR application.

Membrane Bioreactor for Expansion and Differentiation of Embryonic Liver Cells

There is a growing demand for the expansion and differentiation of stem cells for cell therapies, tissue engineering, and model systems for drug screening. Current methods for stem cell production are based on the use of batch tissue culture flasks, which have several drawbacks. In this paper we report on the use of a crossed hollow fiber membrane bioreactor for the expansion and differentiation of embryonic liver cells, which have been used as an alternative model of human liver progenitor cells. The bioreactor is based on two bundles of fiber (PEEK-WC HF and PES-HF) which are cross-assembled in an alternating manner. This bioreactor geometry ensures high mass exchange of nutrients and metabolites, which is important for cell proliferation and differentiation. The membrane bioreactor, thanks to its optimized fluid dynamics and mass transport and the adequate surface properties of hollow fibers, was able to guide the expansion and differentiation of liver progenitor cells in mature hepatocytes as demonstrated by their expression of liver specific functions in terms of urea synthesis, albumin production, and diazepam drug biotransformation.

Control and optimization of solute transport in a thin porous tube

Predicting the distribution of solutes or particles in flows within porous-walled tubes is essential to inform the design of devices that rely on cross-flow filtration, such as those used in water purification, irrigation devices, field-flow fractionation, and hollow-fibre bioreactors for tissue-engineering applications. Motivated by these applications, a radially averaged model for fluid and solute transport in a tube with thin porous walls is derived by developing the classical ideas of Taylor dispersion. The model includes solute diffusion and advection via both radial and axial flow components, and the advection, diffusion, and uptake coefficients in the averaged equation are explicitly derived. The effect of wall permeability, slip, and pressure differentials upon the dispersive solute behaviour are investigated. The model is used to explore the control of solute transport across the membrane walls via the membrane permeability, and a parametric expression for the permeability required to generate a given solute distribution is derived. The theory is applied to the specific example of a hollow-fibre membrane bioreactor, where a uniform delivery of nutrient across the membrane walls to the extra-capillary space is required to promote spatially uniform cell growth.

Reproducibility and applicability of the flux step test for a hollow fibre membrane bioreactor

Results from flux step tests conducted on a pilot-scale hollow fibre immersed membrane bioreactor plant (HF iMBR) are reported. Trials combined a classic flux-step test, each step incorporating six backflush cycles, with an extended (15-h) test to evaluate trends in fouling. Both fouling rate, i.e. the rate of increase in transmembrane pressure (dTMP/dt) at a constant flux, and mean permeability were calculated and reproducibility assessed through the standard deviation. Applied nominal fluxes between 5 and 35Lm−2h−1 (LMH) were employed for the flux-step trials, and all experiments were (i) triplicated through simultaneous application across three central membrane elements in the seven-element membrane module, and (ii) repeated four times. Reproducibility was quantified as standard deviation (SD), and assessed with reference to both the mean permeability across the backflush cycle and the irreversible fouling rate across the three modules – the latter both for the short-term and long-term trials.Results indicated greatly reduced fouling (by 80–88% with respect to fouling rate) for the longer-term study compared with the flux-step data. Fouling rate SD values were slightly lower for the flux step data at 20–27% for the four highest flux steps compared with 30% for the longer trial conducted at 20LMH, based on quadruplicated data. Mean permeability data, on the other hand were much more reproducible, with SD values below 8%. It was concluded that significant variations in hydrodynamics can arise across a module comprising a number of elements, accounting for a 20–40% change in fouling rate. However, this cannot account for the differences recorded between the short-term and long-term fouling measurements, which are a facet of the flux step test conditions.

Treatment of dyeing wastewater using submerged membrane bioreactor

This study was carried out to evaluate the efficiency of aerobic submerged hollow fiber membrane bioreactor (HFMBR) in the removal of direct fast red dye-CI 81 from textile wastewater. The effect of hydraulic retention time (HRT), initial dye concentration, and transmembrane pressure (TMP) on the performance of submerged HFMBR was studied. The removal rate of chemical oxygen demand was found to increase with the increasing of HRT and decrease with increasing initial dye concentration and TMP. The rate of dye removal was found to increase with increasing HRT and decrease with the increasing TMP. The optimum color removal was obtained at initial dye concentration of 150–200 ppm. A mass transfer model for the dye removal using submerged membrane bioreactor system was developed and verified. The results revealed that there is a remarkable agreement between the theoretical results and experimental results with a deviation of 14.83%. The membrane fouling was investigated using electron dispersive X-ray (EDX) and scanning electron microscope (SEM) and compared with the EDX and SEM of the original one. SEM images revealed that there are some geometrical changes that occur in the membrane pores with fouling, while EDX mapping showed that most of the foulants deposited on the inner surface of the fiber.

Performance of a Carboxydothermus hydrogenoformans-immobilizing membrane reactor for syngas upgrading into hydrogen

Hydrogen conversion of CO by a pure culture of Carboxydothermus hydrogenoformans was investigated and optimized in a lab-scale hollow fiber membrane bioreactor (HFMBR). The reactor was operated under strict anaerobic, extremely thermophilic (70 °C) conditions with a continuous supply of gas, for four months. Reactor performance was evaluated under various operational conditions, such as liquid velocity (vliq) (13, 65 and 130 m h−1), temperature (70, 65, and 60 °C), CO pressure (from 1 to 2.5 atm) and CO loading rate (from 1.3 to 16.5molLrxr−1d−1). Overall, results indicated a relatively constant H2 yield of 92 ± 4% (mol mol−1) regardless of the operational condition tested. Permeation across the colonized membrane was improved by three orders of magnitude as compared to the abiotic membrane, because of dissolved CO concentration was constantly maintained low in the liquid on the shell side of the membrane as continually depleted by the microorganisms. Once the biofilm was sufficiently developed, a maximum CO conversion activity of 0.44 mol CO g−1 volatile suspended solid (VSS) d−1 was achieved at a pCO of 2 atm or above and a vliq of 65 m h−1. However, this highest activity represented only 15% of the maximal activity potential of the strain under non-limiting conditions, attributed to the low concentration of dissolved CO (0.01–0.07 mM) present in the HFMBR liquid. Higher vliq (130 m h−1) produced shearing stress, which detached a significant portion of the biofilm from the membrane, and/or prevented less sessile growth (57% total biomass as biofilm, as opposed to 84–86% at lower vliq). One may deduce from this work that the volumetric CO conversion performance of such a membrane bioreactor would be at the most in the range of 5molCOLrxr−1d−1. Overall, the CO conversion performance in the HFMBR was biokinetically limited, when not limited by gas–liquid mass transfer. Additionally, over time, membrane fouling and aging decreased membrane permeability such that the CO transfer rate would be the most limiting factor in the long run.

Coupling ozone and hollow fibers membrane bioreactor for enhanced treatment of gaseous xylene mixture

Two hollow fiber membrane bioreactors (HFMBRs) inoculated with activated sludge were used in series to biodegrade continuously mixed xylene. The influence of gas residence time (τ) and mass loading rate (LR) on elimination capacity (EC) of the mixed xylene was investigated. A maximum elimination capacity (ECmax,v) of 466gm−3h−1 was achieved at τ=10s and LRv=728gm−3h−1. Thereafter, ozone was introduced into inlet gas and the influence of ozone was investigated. Results showed that the maximum xylene elimination capacity increased from 524gm−3h−1 to 568gm−3h−1 and 616gm−3h−1 at τ=10s, respectively when the inlet ozone concentration rose from 200mgm−3 to 400mgm−3 and 600mgm−3, respectively. HFMBR coupled with O3 has higher performance and stability for the long-term operation at the same condition.

Serum-free culture of primary human hepatocytes in a miniaturized hollow-fibre membrane bioreactor for pharmacologicalin vitrostudies

Primary human hepatocytes represent an important cell source for in vitro investigation of hepatic drug metabolism and disposition. In this study, a multi-compartment capillary membrane-based bioreactor technology for three-dimensional (3D) perfusion culture was further developed and miniaturized to a volume of less than 0.5 ml to reduce demand for cells. The miniaturized bioreactor was composed of two capillary layers, each made of alternately arranged oxygen and medium capillaries serving as a 3D culture for the cells. Metabolic activity and stability of primary human hepatocytes was studied in this bioreactor in the presence of 2.5% fetal calf serum (FCS) under serum-free conditions over a culture period of 10 days. The miniaturized bioreactor showed functions comparable to previously reported data for larger variants. Glucose and lactate metabolism, urea production, albumin synthesis and release of intracellular enzymes (AST, ALT, GLDH) showed no significant differences between serum-free and serum-supplemented bioreactors. Activities of human-relevant cytochrome P450 (CYP) isoenzymes (CYP1A2, CYP3A4/5, CYP2C9, CYP2D6, CYP2B6) analyzed by determination of product formation rates from selective probe substrates were also comparable in both groups. Gene expression analysis showed moderately higher expression in the majority of CYP enzymes, transport proteins and enzymes of Phase II metabolism in the serum-free bioreactors compared to those maintained with FCS. In conclusion, the miniaturized bioreactor maintained stable function over the investigated period and thus provides a suitable system for pharmacological studies on primary human hepatocytes under defined serum-free conditions.

Two-Phase Biodegradation of Phenol in a Hollow Fiber Membrane Bioreactor

AbstractA hollow fiber membrane bioreactor (HFMB) was employed for aqueous-organic two-phase biodegradation of phenol using Pseudomonas putida ATCC 11172, and the results were compared with that in a two-phase partitioning bioreactor (TPPB). Phenol containing 2-undecanone was nondispersively contacted with mineral medium that was inoculated with the bacteria. P. putida in suspension was able to biodegrade inhibitory phenol concentrations at 600–2,000 mg/L without experiencing severe substrate inhibition. For example, 1,000 mg/L phenol was completely biodegraded in 46 h at a maximum specific growth rate of 0.49 h−1, whereas the biomass yield and average biodegradation rate were 0.36 g/g and 62 mg/L·h, respectively. Biomass yield and maximum specific growth rate decreased concomitantly with increasing phenol concentration. Phenol removal started at an exponential rate, and subsequently attained a linear profile in nutrient-limited conditions. Unlike conventional two-phase biodegradation systems, HFMB o...

Testing the Applicability of Submerged Hollow Fiber Membrane Bioreactor (MBR) Technology for Municipal Wastewater Treatment in Iraq

Testing the Applicability of Submerged Hollow Fiber Membrane Bioreactor (MBR) Technology for Municipal Wastewater Treatment in Iraq