Fluid hydrodynamics in submerged and sidestream membrane bioreactors

2003 ◽  
Vol 48 (3) ◽  
pp. 113-119 ◽  
Author(s):  
P. Le-Clech ◽  
H. Alvarez-Vazquez ◽  
B. Jefferson ◽  
S. Judd
Keyword(s):  
Mass Transfer ◽  
Membrane Permeability ◽  
Bubble Formation ◽  
Cross Flow ◽  
Membrane Bioreactors ◽  
Air Velocity ◽  
Membrane Processes ◽  
Critical Flux ◽  
Taylor Bubble ◽  
Fluid Hydrodynamics

As with all membrane processes, turbulence, as promoted by aeration in submerged membrane bioreactors (MBRs) or pumping in sidestream (SS) systems to produce somewhat higher effective cross-flow velocities, increases mass transfer and reduces fouling. This is manifested in an elevated critical flux, the flux at which the membrane permeability is sustained. However, the non-Newtonian nature of the sludge makes precise rheological characterisation difficult. In this study, a calculation of the appropriate hydrodynamics parameters for a SS MBR configuration is presented. Optimisation of the aeration in a submerged MBR system has been attained by defining the minimum air velocity required for Taylor bubble formation.

Methods for understanding organic fouling in MBRs

2004 ◽  
Vol 49 (2) ◽  
pp. 237-244 ◽  
Author(s):  
B. Jefferson ◽  
A. Brookes ◽  
P. Le Clech ◽  
S.J. Judd
Keyword(s):  
Organic Carbon ◽  
Membrane Permeability ◽  
Membrane Bioreactors ◽  
Specific Reference ◽  
Critical Flux ◽  
Valuable Data ◽  
Organic Fouling ◽  
Soluble Organic Carbon ◽  
Carbon Concentrations

The identification and quantification of foulants in membrane bioreactors present a major challenge due to their complexity resulting from biomass heterogeneity. Fouling is normally characterised with respect to the critical flux, this being conventionally viewed as being the flux below which a reduction in membrane permeability does not take place. However, recent studies have revealed that such fouling arises even at very low fluxes. Moreover, fouling rates can differ substantially between different experiments, trials and installations even when operated under apparently similar conditions of biomass and soluble organic carbon concentrations. The methods available for quantifying and analysing fouling are reviewed with specific reference to recent data on sub-critical flux behaviour. It is concluded that HPSEC analysis of extracted biomass fractions may provide the most valuable data towards the determination of differences in fouling propensity between different biomasses, as inferred in conventional flux step analysis.

Membrane Processes in Water and Wastewater Treatment

2020 ◽  
pp. 109-136
Keyword(s):  
Lower Energy ◽  
Energy Requirement ◽  
Membrane Bioreactors ◽  
Water And Wastewater Treatment ◽  
Membrane Processes ◽  
Critical Flux ◽  
Liquid Phases ◽  
Water And Wastewater ◽  
Contaminants Removal ◽  
Membrane Technologies

Membrane technologies play a very important role in water and wastewater treatments. These membrane processes provide key advantages over the conventional processes, such as lower energy requirement, lower footprint, easier to operate, and more effective contaminants removal. This chapter introduces different membrane processes: (1) pressure-driven membrane processes which are the most widely used in water and wastewater treatments, and (2) several advanced membrane processes. These processes perform physical or physicochemical separations. Most of the separations occur between liquid-liquid phases, but liquid-gas and gas-gas separation phases are also performed in the latest membrane development. The contemporary membrane bioreactor is the heart of membrane technologies that are used in various applications. However, fouling is a common phenomenon that reduces the efficiency of the membrane operation. Thus, the concept of critical flux and introduction of some control and preventive mechanism could prevent or reduce the fouling in membrane bioreactors.

Multilevel cross flow rotating packed bed to enhance gas film control mass transfer process

2021 ◽  
Vol 161 ◽  
pp. 108321
Author(s):  
Qing-Qing Duan ◽  
Zhi-Guo Yuan ◽  
You-Zhi Liu ◽  
Shan-Shan Duan ◽  
Xi-Fan Duan
Keyword(s):  
Mass Transfer ◽  
Transfer Process ◽  
Cross Flow ◽  
Mass Transfer Process ◽  
Packed Bed ◽  
Rotating Packed Bed

Bubble Formation From Porous Plates in Liquid Cross-Flow

2018 ◽  
Author(s):  
Thomas Shepard ◽  
Eric Ruud ◽  
Henry Kinane ◽  
Deify Law ◽  
Kohl Ordahl
Keyword(s):  
Size Distribution ◽  
Bubble Size ◽  
Bubble Diameter ◽  
Bubble Formation ◽  
Cross Flow ◽  
Rectangular Channels ◽  
Gas Liquid Flow ◽  
Liquid Flows ◽  
Processing Techniques ◽  
The Impact

Controlling bubble diameter and bubble size distribution is important for a variety of applications and active fields of research. In this study the formation of bubbles from porous plates in a liquid cross-flow is examined experimentally. By injecting air through porous plates of various media grades (0.2 to 100) into liquid flows in rectangular channels of varying aspect ratio (1–10) and gas/liquid flow rates the impact of the various factors is presented. Image processing techniques were used to measure bubble diameters and capture their formation from the porous plates. Mean bubble diameters ranged from 0.06–1.21 mm. The present work expands upon the work of [1] and further identifies the relative importance of wall shear stress, air injector pore size and gas to liquid mass flow ratio on bubble size and size distribution.

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