Flat Membrane Bioreactor Research Articles

Membrane fouling and influencing factors of a submerged commercial ceramic flat membrane bioreactor in treatment of coal chemical wastewater

An anoxic/oxic (A/O) treatment unit was upgraded using a submerged commercial ceramic flat-membrane bioreactor. The upgraded bioreactor effectively treated coal chemical wastewater. However, the factors influencing membrane fouling remain unclear. Thus, this study explored the mechanisms of membrane fouling of a commercial ceramic flat membrane bioreactor. With increasing duration of backwash, the rate of growth of transmembrane pressure (TMP) gradually increased. The proportions of concentration polarization resistance Rp and cake layer resistance Rf were 48.87% and 50.08%, respectively. Under the action of static electricity, negatively charged particles in the mixed liquid do not easily adhere to the membrane. Under conditions of high mixed liquid suspended solids (＞12 000 mg/L), an increase in the suspended solid content in the mixture caused membrane fouling and pore blockage. When the flux exceeded 58 L·m−2·h−1, the TMP increased sharply. When the aeration rate exceeded 200 mL/min, the impact of membrane erosion on fouling was no longer significant. The optimal suction/cessation ratio was 7:3. After cleaning with NaOH and NaClO, surface fouling of the membrane was significantly reduced.

Pilot study on ceramic flat membrane bioreactor in treatment of coal chemical wastewater

Some toxic and refractory pollutants in coal chemical wastewater can penetrate the biochemical treatment systems and cause high concentrations of suspended solids in the effluent, which may obstruct the subsequent advanced treatment. In this project, a submerged ceramic plate membrane system was integrated to the last oxic corridor of an existing multistage anoxic/oxic tank. In the ceramic flat membrane bioreactor, the influent chemical oxygen demand (COD) was 102.24–178.88 mg/L, with a removal ratio of approximately 30%. The NH3–N concentration in the effluent was relatively stable with an average value of 1.76 mg/L. The turbidity of the effluent was in the range of 0.235–0.852 NTU and was stable below 1 NTU. A flux of 30 L m−2·h−1 could meet the requirements of the pilot test. A gas-water ratio of 50:1 was found optimal. When the concentration of mixed liquor suspended solids (MLSS) was >3769 mg/L, the extracellular polymeric substance in the mixed solution was utilized by microorganisms as a substrate. High MLSS decreased membrane fouling rate. NaClO backwashing can effectively remove pollutants without adversely affecting the treatment efficiency of membrane bioreactors.

Efficiency of submerged ceramic flat membrane bioreactor in the treatment of coal chemical wastewater

Coal chemical wastewater inhibits the development of the modern coal chemical industry. This study used a submerged ceramic flat membrane bioreactor to treat coal chemical wastewater. By combining the characteristics of high flux and high strength of ceramic flat membrane with the characteristics of high sludge concentration of Membrane Bio-Reactor (MBR). The treatment effect of ceramic flat membrane bioreactor on coal chemical wastewater and related influencing factors were studied. The Chemical Oxygen Demand (COD) concentration, ammonia nitrogen concentration, total phenol concentration, and turbidity of coal chemical wastewater could be reduced to below 31.4 mg/L, 3.03 mg/L, 3.76 mg/L, and 0.4 NTU. The ceramic flat membrane bioreactor achieved the optimal removal effect on pollutants when Hydraulic Retention Time (HRT) was 21 h, Dissolved Oxygen (DO) concentration was 3.2–4.0 mg/L and pH was 7.1–7.5. Among them, the total phenol removal ratio reached the maximum value of 95.31 %, and the COD removal ratio remained at 93 % ∼ 94 %, ammonia nitrogen removal ratio was stable at 95 % ∼ 97 %. The microorganisms in the mixture and membrane mainly were aerobic bacteria, and the content of organic-degrading bacteria, nitrifying and denitrifying bacteria was high. The addition of a membrane module not only prevented the loss of activated sludge in the reactor but also kept a high sludge concentration. Meanwhile, the addition of a membrane module also improves the biodiversity and stability of sludge treatment system.

Pilot Scale Application of a Ceramic Membrane Bioreactor for Treating High-Salinity Oil Production Wastewater.

The offshore oil extraction process generates copious amounts of high-salinity oil-bearing wastewater; at present, treating such wastewater in an efficient and low-consumption manner is a major challenge. In this study, a flat ceramic membrane bioreactor (C−MBR) process combining aerobic microbial treatment technology and ceramic membrane filtration technology was used to treat oil-bearing wastewater. The pilot test results demonstrated the remarkable performance of the combined sequential batch reactor (SBR) and C-MBR process, wherein the chemical oxygen demand (COD) and ammonia nitrogen (NH4+−N) removal rates reached 93% and 98.9%, respectively. Microbial analysis indicated that the symbiosis between Marinobacterium, Marinobacter, and Nitrosomonas might have contributed to simultaneously removing NH4+−N and reducing COD, and the increased enrichment of Nitrosomonas significantly improved the nitrogen removal efficiency. Cleaning ceramic membranes with NaClO solution reduces membrane contamination and membrane cleaning frequency. The combined SBR and C−MBR process is an economical and feasible solution for treating high-salinity oil-bearing wastewater. Based on the pilot application study, the capital expenditure for operating the full-scale combined SBR and C−MBR process was estimated to be 251,717 USD/year, and the unit wastewater treatment cost was 0.21 USD/m3, which saved 62.5% of the energy cost compared to the conventional MBR process.

Efficiency of Submerged Ceramic Flat Membrane Bioreactor in the Treatment of Coal Chemical Wastewater

Efficiency of Submerged Ceramic Flat Membrane Bioreactor in the Treatment of Coal Chemical Wastewater

Efficiency of Submerged Ceramic Flat Membrane Bioreactor in the Treatment of Coal Chemical Wastewater

Efficiency of Submerged Ceramic Flat Membrane Bioreactor in the Treatment of Coal Chemical Wastewater

Numerical simulation and optimization of a cold model of a flat membrane bioreactor air scouring for membrane fouling control

Aeration scouring is currently the most common membrane fouling control technology. The optimization of aeration parameters, such as the aeration aperture, aeration pore spacing, and aerator layout height, can improve the efficiency of aeration and reduce the energy consumption of aeration. However, the simulation results cannot guide engineering practices well due to the limitations in the model precision of computational fluid dynamics. On this basis, the study compared and selected the computational fluid dynamics turbulence model. The DES model was used to study the influence of aeration parameters on membrane fouling control. The study showed that the DES turbulence model had a higher precision and accuracy in predicting the average shear force and the instantaneous shear force distribution on the membrane surface than the k-ε turbulence model. The average error of the DES turbulence model simulation of a bubble height was only 1.33%, which was 14.33% lower than the 15.66% of k-ε. An aeration pore spacing of 20 mm, a height of 100 mm, and an aeration aperture of 2.0 mm were the best layout parameters. The degree of influence of the aeration aperture, the aeration pore spacing, and the height of the aerator layout on the shear force of the membrane surface decreased sequentially. The influence of each interaction on the average shear force of the membrane surface was negligible. Among these parameters, the main reason for the membrane surface shear force was the change in the flow velocity caused by aeration. By calculating the fitting equation and the critical value of the shear force, the critical value of the liquid velocity on the membrane surface that could remove membrane fouling was 0.232 m/s. Although the numerical simulation and optimization of a flat membrane bioreactor air scouring for membrane fouling control were carried out with pure water, it still plays a significant impact on the actual membrane fouling control. These results could guide the optimization design of aeration parameters for flat membrane bioreactors and provide a reference for the analysis of aeration scour control membrane pollution control research.

Biodegradation of gaseous xylene in a flat composite membrane bioreactor

ABSTRACT The xylene is an important hydrophobic volatile organic compound (VOC) widely used as a solvent in different industries. Compared to the conventional bioreactors, the membrane bioreactor is more efficient for the degradation of hydrophobic VOCs. In this work, the degradation of gaseous xylene in a flat composite membrane bioreactor inoculated with activated sludge under different operating conditions was investigated. The maximum elimination capacities, ECv of 289 g/(m3 h) and ECm of 0.145 g/(m2 h) were obtained at the gas residence time of 20 s and the loading rate of 475 g/(m3 h). Moreover, the membrane bioreactor is stable enough to suffer weak shock loading and short intermittent process shutdown. These results indicate that the membrane biotechnology shows great potentials in practical applications for xylene removal.

Numerical simulation of aeration flow phenomena in bench-scale submerged flat membrane bioreactor

The aeration rates in the membrane bioreactor is an important management-point that can reduce the maintenance costs and the membrane fouling by changing the reactor flow patterns and the shear stresses in the vicinity of the membrane surface. In the present study, COMSOL, a finite element analysis (FEA) program was used to analyze the velocity distribution, the shear stresses between the membranes and the baffle, and the shear stresses between the membranes in a system in which two flat membrane modules are installed within a bench-scale submerged flat membrane reactor for aeration at the bottom. The diameters and velocities of the bubbles that develop the velocities within the reactor were measured through image analysis and the results were applied to numerical analysis. The shear stresses between the membrane and the baffle showed relatively high values ranging from 0Pa to 0.1Pa at the 1/3 point from the bottom of the membrane module and showed high shear stresses in some of the top part of the membrane module too. However, the shear stresses between the membranes were formed to be lower than the shear stresses between the membranes and the baffle. This is disadvantageous to the reduction of fouling on the surfaces of the membranes where permeation fluxes exist.

Study on Pollutant Removal Efficiency of Industrial Wastewater Using Submerged Anaerobic Membrane Bio-Reactor

The industrial effluents contain more organic pollutants, the most favorable option to treat this by anaerobic treatment process. In this study, a lab scale submerged anaerobic flat membrane bioreactor was operated with pumping operation for the treatment of tannery effluent. This Reactor was used to investigate the Residence Time Distribution and Rheology of the wastewater in the reactor under different Organic Loading Rate. Initially, treatment efficiency of the Submerged Membrane Bio – reactor was studied by monitoring various parameters (COD, TSS, TS, Alkalinity, VFA and pH). The COD removal efficiency was increasing from 66.67% to 88.89% invariably of the sludge retention inside the reactor. The results also showed that the membrane fouling was also occurring simultaneously, which is always predominant in any type of membrane treatment process. In order to decrease the membrane fouling rate, gas recirculation and effluent recirculation were employed and it proved efficient throughout the rheology study. The combined use of gas bubbles and periodic backwashing enables operation in high filtrate fluxes without seriously increasing the fouling resistance. RTD was maintained between 6 to 12 days with 18kg/m3/day was found to be optimum in efficient removal efficiency.

Performance of a composite membrane bioreactor for the removal of ethyl acetate from waste air

Ethyl acetate removal from an air stream was carried out by using a flat composite membrane bioreactor. The composite membrane consisted of a dense polydimethylsiloxane top layer with an average thickness of 0.3μm supported in a porous polyacrylonitrile layer (50μm). The membrane bioreactor (MBR) was operated during 3months, and a maximum elimination capacity of 225gm−3h−1 at an empty bed residence time of 60s was observed. Removal efficiencies higher than 95% were obtained for inlet loads lower than 200gm−3h−1 and empty bed residence times as short as 15s. The estimated yield coefficient, determined from the carbon dioxide production, resulted in 0.82g dry biomass synthesized per gram of ethyl acetate degraded. No data of ethyl acetate treatment in MBR have been found in the literature, but the results illustrate that membrane bioreactors can potentially be a good option for its treatment.

Biotransformation of diazepam in a clinically relevant flat membrane bioreactor model using primary porcine hepatocytes

In vitro biotransformation of drug using commercial culture medium with serum may not be the ideal culture medium for clinical application in extracorporeal bioartificial liver support (BAL) systems. In these systems, patient's blood or plasma is plumbed to primary hepatocytes within a seeded bioreactor, creating interaction between plasma and seeded hepatocytes. To address this situation, we investigated the biotransformation potential of diazepam in primary porcine hepatocytes with a flat membrane bioreactor (FMB); we used human plasma exposure and serum-free media in organotypical double gel culture model for long-term culture. We investigated diazepam clearance and all major metabolites of diazepam, such as oxazepam, temazepam, and desmethyldiazepam, in conventional single gel and organotypical sandwich models and compared them to the FMB model. Diazepam elimination was higher in double gel cultures with exposure to both SF 3 medium conditions and plasma, when compared to the single gel model in a Petri dish. It was observed that in the FMB, diazepam elimination was stable at about 3 pg/h/cell in plasma and SF 3 exposure. Oxazepam synthesis in the bioreactor was approximately one quarter less than in the Petri dish, but there were no differences between N-desmethyldiazepam and temazepam synthesis in double gel culture. In the flat membrane bioreactor, there was no decrease in the biotransformation of diazepam in plasma exposure compared with the control group. Our results suggest that this plasma exposure bioreactor may offer a useful approach in clinical use of extracorporeal BAL, as well as for drug metabolite investigation into toxicological research.

Cryopreservation of primary porcine liver cells in an organotypical sandwich model in a clinically relevant flat membrane bioreactor

To overcome the logistical difficulties of continuously supplying freshly-isolated, primary porcine liver cells to bioartificial liver support bioreactors, we developed a cryopreservation method using an organotypical sandwich model in a flat membrane bioreactor (FMB). We measured albumin secretion rate, urea synthesis rate and 7-ethoxy coumarin (ECOD) in long-term cultures of cryopreserved cells (up to 14 days). The albumin secretion rate was 62% that of non-cryopreserved cells at days 11 and 14. The ECOD activity was 54% that of fresh, control cells initially and increased up to 79% by the 14th day. The urea synthesis rate was stable at 60% that of the control. This study showed that cryopreserved cells can recover liver-specific functions. This result has the potential to dramatically expand the clinical application of bioartificial liver supports.

Preclinical characterization of primary porcine hepatocytes in a clinically relevant flat membrane bioreactor

Using primary porcine hepatocytes, artificial extracorporeal liver support (AEL) is a therapy that carries out the liver functions of liver failure patients until their own organs have been regenerated or until whole organ transplantation. Significant variation exists with regard to current bioreactor designs for AEL, and they may not reflect the in vivo architecture of the liver since each individual hepatocyte has its own direct contact with blood plasma for oxygen and nutrient supply and detoxification. The present study, based on our flat membrane bioreactor (FMB), aimed at in vivo liver architecture and to meet authentic clinical levels of human plasma exposure. Since many existing preclinical AELs are based on commercial culture medium with or without nonhuman serum, they may not authentically reflect the clinical situation in human patients, and little research has been done on human plasma exposure in in vitro culture-based bioreactors. To address this situation, herein we examined liver-specific functions such as albumin secretion, urea synthesis, glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), cell membrane stability by lactate dehydrogenase (LDH) test and ammonia clearance by using human plasma and serum-free medium in long-term culture of primary porcine hepatocytes to show the potential of our clinically relevant FMB. We observed that the organotypical double-gel (DG) culture is superior to conventional collagen-coated single-gel (SG) cultures. The performance of liver-specific functions by the FMB has long-term stability with intact cell morphology for up to 20 days under both plasma exposure and serum-free media. Our three focus points (long-term culture that correlates with the generation time of spontaneous regeneration, high-density culture, organotypical culture model using human plasma) may provide valuable clinical clues for AEL.

Comparative study of polyvinylidene fluoride and PES flat membranes in submerged MBRs to treat domestic wastewater

Two kinds of membranes, polyvinylidene fluoride (PVDF) and polyethersulfone (PES), were used in submerged flat membrane bioreactors (MBRs) to treat domestic wastewater in this study. The MBRs ran under the same reactor structure, the same membrane pore size of 0.45 mICROm and the same anoxic/ oxic (A/O) process. The experimental results showed that: (1) With the influent of BOD(5) 200-500 mg/L and COD(Cr) 400-1,000 mg/L, PVDF MBR achieved the removal efficiencies of BOD(5) 96-98% and COD(Cr) 89-98%, and those were 97-99% and 93-97% in PES MBR. The interceptive efficiency of PES membrane to BOD(5) and COD(Cr) was superior to PVDF membrane. (2) The removal efficiencies of TN and NH(3)-N in two MBRs exhibited good results which were greater than 85%. The removal efficiencies of TP were greater than 80% in both MBRs. (3) MLSS concentration changed from 2,000 mg/L to 7,000 mg/L during the experiment. PES membrane was not washed and the membrane flux was steady. However, the flux of PVDF one decreased quickly and was washed for twice. It meant that PES membrane had fine capability than PVDF one.

Optimization of membrane bioreactor performances during enzymatic oxidation of waste bio-polyphenols

Polyphenols represent a wide class of organic compounds characterised by oxidrylic group bound to an aromatic ring. Their presence makes agro-food wastewaters phytotoxic and not suitable to conventional biological oxidation because of the inhibition of the bacterial activity. In this work the oxidation of polyphenols has been achieved by means of an enzymatic reaction carried out in a membrane bioreactor where the enzyme has been confined upstream the membrane. Tyrosinase from mushroom has been used as biocatalyst confined in a flat membrane bioreactor: an experimental study has been carried out in order to select the optimal operating conditions and a theoretical analysis has been also carried out in order to design the optimal bioreactor configuration for the process scale-up. The kinetic of the enzymatic oxidation has been preliminarily studied to establish the reaction pattern. A transport model has been also formulated to characterize the behaviour of the enzyme membrane reactor. The bioreactor configuration and its performance have been analysed in order to optimize the process conversion. The results of the experimental analysis in terms of products distribution confirmed the validity of the enzyme membrane bioreactor for the oxidation of polyphenols.

Vacuum membrane applications in domestic wastewater reuse

A flat type membrane bioreactor (MBR) with a pore size of 0.038 μm and having a total surface area of 540 m 2 was operated intermittently for over a year in METU campus at Ankara to treat domestic effluents from dormitories and academic village. At the first stage the MBR plant was operated continuously for 140 days with hydraulic retention times ranging between 18 and 22 h. During this period, sludge concentration increased from an initial 2.4 g/L to 21 g/L. The plant consistently produced fully nitrified effluents when DO was kept over 2.0 mg/L. Over 99.99% BOD 5 removal and 95% COD removals were achieved in the system. When DO concentration was 2 mg/L and mixed liquor suspended solids, MLSS, concentration was 16 g/L, simultaneous nitrification and denitrification was observed in the system. The effluent turbidity, was always below 1 NTU, equal to or below that of tap water, and around 6–7 log coliform removals with close to zero/100 mL effluent counts were achieved.

A bioartificial liver support system using primary hepatocytes: a preclinical study in a new porcine hepatectomy model

BackgroundBioartificial liver support systems providing a bridge to transplantation or even a definitive treatment of acute hepatic failure are a current focus of research. Different devices are used, although an impact on patient survival is doubtful for the time being. After developing a new flat membrane bioreactor, further preclinical studies have become necessary. Existing animal models of fulminant hepatic failure show common difficulties in defining a reproducible loss of functional liver tissue while considering systemic side effects. We now present a reproducible model with total hepatectomy in pigs, suitable to test the safety and efficacy of liver support systems. MethodsTwelve pigs underwent total hepatectomy by using silicone tubes and a Y-adapter as vascular prosthesis; intracranial pressure was measured via a subdural probe. Anhepatic pigs were monitored under general anesthesia until death occurred. All were treated with a new flat membrane bioreactor (FMB) that contained porcine hepatocytes in 6 of the 12 cases. ResultsOur hepatectomy technique proved to be successful without requiring venovenous bypass circulation. Mean vascular clamping time was 9 minutes. The mean survival time was longer in animals treated with hepatocyte-equipped bioreactors than in untreated animals (24.8 ± 4.3 vs 16.4 ± 4.7 hours), which already showed increased intracranial pressure after 10 to 12 hours. Serum albumin levels indicated stable cell-specific functions of the FMB. ConclusionsThe described technique of total hepatectomy is a well-reproducible animal model. The presented FMB maintained stable cell-specific functions and is a safe and efficient device.

Evaluation of a Flat Membrane Hepatocyte Bioreactor for Pharmacotoxicological Applications: Evidence that Inhibition of Spontaneously Produced Nitric Oxide Improves Cell Functionality

A laboratory-scale bioreactor was re-evaluated, with the aim of improving its use for the perfused culture of rat hepatocytes. In contrast to conventional culture systems, the flat membrane bioreactor (FMB) showed good functionality and biochemical competence during 2-3 days. Hepatocytes cultured in the FMB, specifically in a "sandwich" configuration, were functionally stable, as shown by a high rate of urea biosynthesis after challenge with NH4Cl, a low alanine-aminotransferase leakage and suppressed spontaneous nitric oxide (NO) production. Moreover, the time-course of the disappearance of cyclosporin A (CsA) from the perfusate demonstrated the high biotransformation capacity of cells in the FMB. The effect of CsA on the modulation of urea and spontaneous NO production demonstrated flexibility, in that minor changes could be observed at diverse time intervals and in a non-destructive way. The monitoring of nitrite levels during various steps of isolation and culture suggested that spontaneously produced NO has a negative impact on hepatocyte metabolic and functional integrity. In spite of the sophisticated techniques that are being used for the preparation of bioreactors, with hepatocytes surviving for longer periods, our data have shed light on some factors that could be important for the successful use of similar models for pharmacotoxicological and other biomedical applications.

Flat membrane bioreactor for the replacement of liver functions.

Each year in the U.S., approximately 150,000 people are hospitalised with liver disease and over 43,000 people die from it (Langer and Vacanti 1993). These numbers are expected to increase as the 4 million people currently infected with Hepatitis C advance to liver failure. Transplantation, the only effective means of treating liver failure, is not an option for many patients. Some are simply not sick enough to justify the massive cost, invasiveness and risk of a transplant, leaving them unaided today. Other patients are too sick to qualify, while others die awaiting a transplant.