Effect of Aeration Conditions on the Flow Field in the Submerged Membrane Bioreactor

2014 ◽  
Vol 535 ◽  
pp. 539-546 ◽  
Author(s):  
Shi Lu Xing ◽  
Zhong Lan Tao ◽  
Jian Ming Niu ◽  
Rui Tian ◽  
Chun Li Li
Keyword(s):  
Membrane Bioreactor ◽  
Flow Model ◽  
Liquid Velocity ◽  
Membrane Surface ◽  
Gas Holdup ◽  
Aeration Rate ◽  
Two Phase ◽  
Submerged Membrane Bioreactor ◽  
Aeration Conditions ◽  
Simulation Results

A full size 3D numerical simulation of gas liquid two-phase flow in a submerged membrane bioreactor was carried out. The standard k-ε turbulence model and Euler multiphase flow model of fluent were used. The effect of changed aeration conditions in the reactor on the gas holdup and gas-liquid velocity distribution in the reactor was studied. The simulation results were shown that, at the same aeration rate, the liquid and gas velocities of 1mm hole aerated at the membrane surface increased faster than 2 mm and 3mm aeration holes; At the same aeration hole , with the increase of aeration rate，the liquid and gas velocities at the membrane surface increased; At the 1mm aeration hole and 5.5m3/h aeration rate, the vortex area was larger and gas holdup was higher, so that gas and liquid were contacting well and the membrane surface scouring effect was better; The Simulation also shown that local gas holdup was lower at close to the wall at the bottom of the reactor, this was not conducive to the growth of microorganisms in the activated sludge, the need to further optimize the structure of aeration and reactor.

A venturi device reduces membrane fouling in a submerged membrane bioreactor

2016 ◽  
Vol 74 (1) ◽  
pp. 147-156 ◽  
Author(s):  
Necati Kayaalp ◽  
Gokmen Ozturkmen
Keyword(s):  
Membrane Fouling ◽  
Membrane Bioreactor ◽  
Membrane Surface ◽  
Oxygen Transfer Rate ◽  
Surface Cleaning ◽  
Aeration Rate ◽  
Transmembrane Pressure ◽  
Submerged Membrane Bioreactor ◽  
System A ◽  
Do Concentration

In this study, for the first time, a venturi device was integrated into a submerged membrane bioreactor (MBR) to improve membrane surface cleaning and bioreactor oxygenation. The performances of a blower and the venturi device were compared in terms of membrane fouling and bioreactor oxygenation. Upon comparing membrane fouling, the performances were similar for a low operation flux (18 L/m2.h); however, at a medium flux (32 L/m2.h), the venturi system operated 3.4 times longer than the blower system, and the final transmembrane pressure was one-third that of the blower system. At the highest flux studied (50 L/m2.h), the venturi system operated 5.4 times longer than the blower system. The most notable advantage of using a venturi device was that the dissolved oxygen (DO) concentration of the MBR was in the range of 7 to 8 mg/L at a 3 L/min aeration rate, while the DO concentration of the MBR was inadequate (a maximum of 0.29 mg/L) in the blower system. A clean water oxygenation test at a 3 L/min aeration rate indicated that the standard oxygen transfer rate for the venturi system was 9.5 times higher than that of the blower system.

Impact of chemical cleaning and air-sparging on the critical and sustainable flux in a flat sheet membrane bioreactor for municipal wastewater treatment

2008 ◽  
Vol 57 (12) ◽  
pp. 1873-1879 ◽  
Author(s):  
G. Guglielmi ◽  
D. Chiarani ◽  
D. P. Saroj ◽  
G. Andreottola
Keyword(s):  
Membrane Bioreactor ◽  
Municipal Wastewater ◽  
Membrane Surface ◽  
Municipal Wastewater Treatment ◽  
Chemical Cleaning ◽  
Critical Flux ◽  
Submerged Membrane Bioreactor ◽  
Flat Sheet ◽  
Exponential Trend ◽  
Flat Sheet Membrane

The paper discusses the experimental optimisation of both chemical and mechanical cleaning procedures for a flat-sheet submerged membrane bioreactor fed with municipal wastewater. Fouling was evaluated by means of the critical flux concept, which was experimentally measured by short-term flux-stepping tests. By keeping constant most important parameters of the biological process (MLSS, sludge age), two different chemical cleaning protocols (2,000 mg L−1 NaOCl and 200 mg L−1 NaOCl) were applied with different frequency and, after approximately 9 months of operation, the criticality threshold was determined under different values of SADm (specific aeration demand per unit of membrane surface area). The weaker and more frequent chemical cleaning regime (200 mg L−1, monthly) proved much more effective than the stronger and less frequent strategy (2,000 mg L−1, once every three months). The improvement of performances was quantified by two TMP-based parameters, the fouling rate and the ΔTMP (difference between TMP values during the increasing and decreasing phase of hysteresis). The best performing configuration was then checked over a longer period by running four long-term trials showing an exponential trend of the sub-critical fouling rate with the imposed flux.

3D Cavitations Turbulent Transient Calculation in the Francis Turbine Model

2012 ◽  
Vol 479-481 ◽  
pp. 2466-2470
Author(s):  
Dun Zhang ◽  
Yuan Zheng
Keyword(s):  
Model Experiment ◽  
Flow Model ◽  
Three Dimensional ◽  
Francis Turbine ◽  
Two Phase ◽  
Mixture Flow ◽  
Phase Mixture ◽  
Simulation Results ◽  
Accurate Numerical Solution ◽  
Turbine Model

Analysis had been carried out, based on the three-dimensional transient viscous turbulent calculation of a Francis turbine full flow field, the complete cavitations model and the two-phase mixture flow model were combined during the calculation, more accurate numerical solution had been obtained. According to the simulation results, the site and extent of cavitations in the turbine flow were reflected within the specific conditions, and were more consistent with the cavitations phenomenon observed in the model experiment, also provided a reference for the more in-depth research.

scholarly journals Hydrodynamic Study and Influence of Physicochemical Parameters on Gas Retention in a Submerged Membrane Bioreactor

2018 ◽  
Author(s):  
Nsoe Mengue Jean Jacques Nestor ◽  
Kofa Guillaume ◽  
Marc Heran ◽  
Kayem Joseph ◽  
Ndi Koungou Sylvere
Keyword(s):  
Flow Rate ◽  
Membrane Bioreactor ◽  
Mixing Time ◽  
Average Pore Size ◽  
Air Flow ◽  
Aeration Rate ◽  
Ammonium Formate ◽  
Air Flow Rate ◽  
Average Pore ◽  
Submerged Membrane Bioreactor

Gas-liquid reactors pose transfer difficulties due to diffusion effects. It is necessary to master the aeration and hydrodynamics of the medium to conduct the reaction well and get a good performance. For this purpose, a study in a submerged membrane bioreactor with a useful volume of 30L, consisting of a microfiltration membrane with an average pore size of 0.14 mm having an effective surface area of 0.2 m2 and a PVC cylindrical air diffuser of radius 4 cm has been studied. The saline tracing method associated with a conductimetric follow-up made it possible to determine the residence times and the mixing time in the reactor at 4 different points both in recirculation and in the absence of recirculation. Gas retention was measured by the manometric method. The experiments were carried out at different temperatures of 25 ° C, at 45 ° C, with a variable air flow rate of 0.5 to 16 mL / s and different solutions (osmosis water, ammonium formate solution, solution ammonium formate + salt, synthetic rubber effluent). The results show that the mixing time varies from one point to another and the recirculation of the mixture reduces the mixing time. One of the positions is limiting, the transfer is done most by diffusion with a mixing time of 115 min without circulation and 65 min with circulation. Gas retention increases with aeration rate and temperature. On the other hand, the more the medium becomes rich in organic substances, the more the gaseous retention decreases. The homogeneous fine-bubble regime is obtained for an air flow rate of between 3 and 10 mL / s of aeration. Beyond this flow rate, the regime becomes heterogeneous without a transition phase for ammonium formate and formate ammonium + salt solutions.

scholarly journals Influence of nanoparticles on filterability of fruit-juice industry wastewater using submerged membrane bioreactor

2017 ◽  
Vol 76 (3) ◽  
pp. 705-711 ◽  
Author(s):  
Guler Turkoglu Demirkol ◽  
Nadir Dizge ◽  
Turkan Ormanci Acar ◽  
Oyku Mutlu Salmanli ◽  
Nese Tufekci
Keyword(s):  
Membrane Bioreactor ◽  
Fruit Juice ◽  
Membrane Surface ◽  
Glass Container ◽  
Submerged Membrane Bioreactor ◽  
Flux Decline ◽  
Coated Membranes ◽  
Pes Membrane ◽  
Coated Membrane ◽  
Industry Wastewater

In this study, polyethersulfone (PES) ultrafiltration membrane surface was modified with nano-sized zinc oxide (nZnO) and silver (nAg) to improve the membrane filterability of the mixed liquor and used to treat fruit-juice industry wastewater in a submerged membrane bioreactor (MBR). The nAg was synthesized using three different methods. In the first method, named as nAg-M1, PES membrane was placed on the membrane module and nAg solution was passed through the membrane for 24 h at 25 ± 1 °C. In the second method, named as nAg-M2, PES membrane was placed in a glass container and it was shaken for 24 h at 150 rpm at 25 ± 1 °C. In the third method, named as nAg-M3, Ag nanoparticles were loaded onto PES membrane in L-ascorbic acid solution (0.1 mol/L) at pH 2 for 24 h at 150 rpm at 25 ± 1 °C. For the preparation of nZnO coated membrane, nZnO nanoparticles solution was passed through the membrane for 24 h at 25 ± 1 °C. Anti-fouling performance of pristine and coated membranes was examined using the submerged MBR. The results showed that nZnO and nAg-M3 membranes showed lower flux decline compared with pristine membrane. Moreover, pristine and coated PES membranes were characterized using a permeation test, contact angle goniometer, and scanning electron microscopy.

Jet Flotation Column System Structure Design and Numerical Simulation of Two-Phase Flow

2012 ◽  
Vol 616-618 ◽  
pp. 655-661 ◽  
Author(s):  
Run Quan Yang ◽  
Huai Fa Wang ◽  
Jian Chao Liu
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Flow Model ◽  
Structure Design ◽  
System Structure ◽  
Two Phase ◽  
Air Bubble ◽  
Flotation Column ◽  
Column System ◽  
Simulation Results

A laboratory scale jet flotation column system was designed and air inflation for flotation column was provided by jet aerator with a chamber. In order to understand interior flow field distribution of jet aerator and flotation column, two-phase turbulent flow model was established by use of commercial computational fluid dynamics (CFD) software FLUENT 6.3.26. Modeling of the flow field was firstly established with GAMBIT 2.3.16; standard k-ε turbulence model and multiphase flow model MIXTURE were adopted for gas-liquid two-phase numerical simulation about jet aerator and flotation column. The simulation results show that gas-liquid two-phase mixing have been established by the cavity entrainment vortex flow in jet aerator with a chamber, and the distortion was really occurred although the reversed cone feed inlet have been designed, at the same time non-uniform distribution of air-bubble was also simulated. Simulation results can help to optimize the structure of the jet flotation column.

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