Mass Transfer of Oxygen in Diffused Aeration Systems

Starting from the fundamental concepts of mass transfer of gases into liquid, a comprehensive mathematical equation, relating the mass oxygen-transfer rate to the various parameters in diffused aeration systems, is developed.The important variables involved are the liquid film coefficient, temperature, waste water characteristics, bubble size, diffuser submergence, airflow rate, and the contact time. The contact time between the air bubbles and the oxygen absorbing liquid can be varied by changing the operating conditions of the aeration system in terms of the direction of air and liquid movement. Investigations on four such combinations are presented.The influence of the above-mentioned variables, individually or in combination, on the mass oxygen-transfer rate and overall oxygen transfer coefficient are discussed. The presentation is supported with laboratory data collected from aeration studies over a period of 3 years. With proper understanding of the influence of operating parameters on mass transfer coefficients, it should be possible to modify the design and operation of aeration basins in order to obtain increased oxygen transfer.

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Two-Phase Flow Mass Transfer Analysis of Airlift Pump for Aquaculture Applications

Fluids ◽

10.3390/fluids6060226 ◽

2021 ◽

Vol 6 (6) ◽

pp. 226

Author(s):

Rashal Abed ◽

Mohamed M. Hussein ◽

Wael H. Ahmed ◽

Sherif Abdou

Keyword(s):

Mass Transfer ◽

Oxygen Transfer ◽

Transfer Rate ◽

Two Phase Flow ◽

Oxygen Transfer Rate ◽

Flow Patterns ◽

Oxygen Mass Transfer ◽

Phase Flow ◽

Two Phase ◽

Airlift Pump

Airlift pumps can be used in the aquaculture industry to provide aeration while concurrently moving water utilizing the dynamics of two-phase flow in the pump riser. The oxygen mass transfer that occurs from the injected compressed air to the water in the aquaculture systems can be experimentally investigated to determine the pump aeration capabilities. The objective of this study is to evaluate the effects of various airflow rates as well as the injection methods on the oxygen transfer rate within a dual injector airlift pump system. Experiments were conducted using an airlift pump connected to a vertical pump riser within a recirculating system. Both two-phase flow patterns and the void fraction measurements were used to evaluate the dissolved oxygen mass transfer mechanism through the airlift pump. A dissolved oxygen (DO) sensor was used to determine the DO levels within the airlift pumping system at different operating conditions required by the pump. Flow visualization imaging and particle image velocimetry (PIV) measurements were performed in order to better understand the effects of the two-phase flow patterns on the aeration performance. It was found that the radial injection method reached the saturation point faster at lower airflow rates, whereas the axial method performed better as the airflow rates were increased. The standard oxygen transfer rate (SOTR) and standard aeration efficiency (SAE) were calculated and were found to strongly depend on the injection method as well as the two-phase flow patterns in the pump riser.

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DISTRIBUTION OF OXYGEN TRANSFER RATE IN STIRRED BIOREACTORS WITH SIMULATED BROTHS

Environmental Engineering and Management Journal ◽

10.30638/eemj.2008.034 ◽

2008 ◽

Vol 7 (3) ◽

pp. 199-211 ◽

Cited By ~ 1

Author(s):

Dan Cascaval ◽

Anca-Irina Galaction ◽

Stefanica Camarut ◽

Radu Z. Tudose

Keyword(s):

Oxygen Transfer ◽

Transfer Rate ◽

Oxygen Transfer Rate ◽

Stirred Bioreactors

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Estimation of oxygen transfer rate in sequencing batch reactor

Water Science & Technology ◽

10.2166/wst.1996.0458 ◽

1996 ◽

Vol 34 (3-4) ◽

pp. 413-420

Author(s):

Y. C. Liao ◽

D. J. Lee

Keyword(s):

Dissolved Oxygen ◽

Oxygen Transfer ◽

Transfer Rate ◽

Sequencing Batch Reactor ◽

Batch Reactor ◽

Oxygen Transfer Rate ◽

Intermittent Aeration ◽

Transient Effects ◽

Operational Parameters ◽

Transient Model

Transient model of oxygen transfer rate in a sequencing batch reactor is derived and solved numerically. The dissolved oxygen response under several conditions is analyzed. Effects of operational parameters and liquid bath height are studied. When with short, intermittent aeration periods, the transient effects on oxygen transfer rate may be substantial and should be taken into considerations. An example considering bioreaction is also given.

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Oxygen Supply Method Using Gas-Permeable Film for Wastewater Treatment

Water Science & Technology ◽

10.2166/wst.1993.0169 ◽

1993 ◽

Vol 28 (7) ◽

pp. 243-250 ◽

Cited By ~ 17

Author(s):

Y. Suzuki ◽

S. Miyahara ◽

K. Takeishi

Keyword(s):

Wastewater Treatment ◽

Energy Consumption ◽

Oxygen Transfer ◽

Transfer Rate ◽

Oxygen Supply ◽

Oxygen Transfer Rate ◽

High Energy ◽

High Rate ◽

N Removal ◽

High Energy Consumption

Gas-permeable film can separate air and water, and at the same time, let oxygen diffuse from the air to the water through the film. An oxygen supply method using this film was investigated for the purpose of reducing energy consumption for wastewater treatment. The oxygen transfer rate was measured for the cases with or without biofilm, which proved the high rate of oxygen transfer in the case with nitrifying biofilm which performed nitrification. When the Gas-permeable film with nitrifying biofilm was applied to the treatment of wastewater, denitrifying biofilm formed on the nitrifying biofilm, and simultaneous nitrification and denitrification occurred, resulting in the high rate of organic matter and T-N removal (7 gTOC/m2/d and 4 gT-N/m2/d, respectively). However, periodic sloughing of the denitrifying biofilm was needed to keep the oxygen transfer rate high. Energy consumption of the process using the film in the form of tubes was estimated to be less than 40% of that of the activated sludge process.

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Flow Mixing Enhancement from Balloon Pulsations in an Intravenous Oxygenator

Journal of Biomechanical Engineering ◽

10.1115/1.1894260 ◽

2004 ◽

Vol 127 (3) ◽

pp. 400-415 ◽

Cited By ~ 3

Author(s):

Amador M. Guzmán ◽

Rodrigo A. Escobar ◽

Cristina H. Amon

Keyword(s):

Numerical Simulations ◽

Oxygen Transfer ◽

Fiber Bundle ◽

Transfer Rate ◽

Oxygen Transfer Rate ◽

Three Dimensional ◽

Time Dependent ◽

Fiber Placement ◽

Flow Mixing ◽

Dependent Flow

Computational investigations of flow mixing and oxygen transfer characteristics in an intravenous membrane oxygenator (IMO) are performed by direct numerical simulations of the conservation of mass, momentum, and species equations. Three-dimensional computational models are developed to investigate flow-mixing and oxygen-transfer characteristics for stationary and pulsating balloons, using the spectral element method. For a stationary balloon, the effect of the fiber placement within the fiber bundle and the number of fiber rings is investigated. In a pulsating balloon, the flow mixing characteristics are determined and the oxygen transfer rate is evaluated. For a stationary balloon, numerical simulations show two well-defined flow patterns that depend on the region of the IMO device. Successive increases of the Reynolds number raise the longitudinal velocity without creating secondary flow. This characteristic is not affected by staggered or non-staggered fiber placement within the fiber bundle. For a pulsating balloon, the flow mixing is enhanced by generating a three-dimensional time-dependent flow characterized by oscillatory radial, pulsatile longitudinal, and both oscillatory and random tangential velocities. This three-dimensional flow increases the flow mixing due to an active time-dependent secondary flow, particularly around the fibers. Analytical models show the fiber bundle placement effect on the pressure gradient and flow pattern. The oxygen transport from the fiber surface to the mean flow is due to a dominant radial diffusion mechanism, for the stationary balloon. The oxygen transfer rate reaches an asymptotic behavior at relatively low Reynolds numbers. For a pulsating balloon, the time-dependent oxygen-concentration field resembles the oscillatory and wavy nature of the time-dependent flow. Sherwood number evaluations demonstrate that balloon pulsations enhance the oxygen transfer rate, even for smaller flow rates.

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Enhancement and repression of the volumetric oxygen transfer coefficient through hydrocarbon addition and its influence on oxygen transfer rate in stirred tank bioreactors

Biochemical Engineering Journal ◽

10.1016/j.bej.2005.11.007 ◽

2006 ◽

Vol 28 (3) ◽

pp. 237-242 ◽

Cited By ~ 48

Author(s):

K.G. Clarke ◽

P.C. Williams ◽

M.S. Smit ◽

S.T.L. Harrison

Keyword(s):

Transfer Coefficient ◽

Oxygen Transfer ◽

Transfer Rate ◽

Oxygen Transfer Rate ◽

Stirred Tank ◽

Oxygen Transfer Coefficient ◽

Volumetric Oxygen Transfer Coefficient

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The Influence of Optic and Polarographic Dissolved Oxygen Sensors Estimating the Volumetric Oxygen Mass Transfer Coefficient (KLa)

Modern Applied Science ◽

10.5539/mas.v10n8p142 ◽

2016 ◽

Vol 10 (8) ◽

pp. 142 ◽

Cited By ~ 1

Author(s):

Gustavo Andrés Baquero-Rodríguez ◽

Jaime A. Lara-Borrero

Keyword(s):

Mass Transfer ◽

Wastewater Treatment ◽

Dissolved Oxygen ◽

Transfer Coefficient ◽

Mass Transfer Coefficient ◽

Oxygen Transfer ◽

Airflow Rate ◽

Oxygen Probe ◽

Aeration System ◽

Oxygen Measurement

Aeration is usually the most energy intensive part of the wastewater treatment process. Optimizing the aeration system is essential for reducing energy costs. Field tests oriented to estimate parameters related to oxygen transfer are a common approach to compare aeration systems. The aim of this research is to assess the effect of dissolved oxygen probe lag on oxygen transfer parameter estimation. Experimental procedures regarding to process automation and control were applied to quantify dissolved oxygen probe lag. We have measured oxygen transfer in clean water, under a wide range of conditions (airflow rate, diffuser characteristics and diffuser density), with optic and polarographic sensors for dissolved oxygen measurement. The oxygen transfer was measured as per ASCE Standard procedures. Nonparametric statistical tests were used to compare the estimated volumetric mass transfer coefficient KLa with different sensors. According to the results, there is not significant influence of the probe lag (also known as time constant) or probe characteristics on the parameters used to assess oxygen transfer efficiency. This fact has great relevance in common practice of aerobic process for wastewater treatment because dissolved oxygen monitoring is used as an input for decision making related to the energy optimization in the aeration system. Findings from these tests contradict previous studies which claim that lag time in polarographic sensors for the dissolved oxygen measurement can bias estimate KLa.

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