Experimental studies of the fluid dynamics in the separation zone in dissolved air flotation

2000 ◽  
Vol 34 (1) ◽  
pp. 21-30 ◽  
Author(s):  
Måns Lundh ◽  
Lennart Jönsson ◽  
Jan Dahlquist
Keyword(s):  
Fluid Dynamics ◽  
Separation Zone ◽  
Experimental Studies ◽  
Dissolved Air Flotation ◽  
Air Flotation ◽  
Dissolved Air

scholarly journals Modeling the Separation of Microorganisms in Bioprocesses by Flotation

Processes ◽  
2018 ◽  
Vol 6 (10) ◽  
pp. 184 ◽  
Author(s):  
Stefan Schmideder ◽  
Christoph Kirse ◽  
Julia Hofinger ◽  
Sascha Rollié ◽  
Heiko Briesen
Keyword(s):  
Fluid Dynamics ◽  
Separation Efficiency ◽  
Algebraic Model ◽  
Balance Model ◽  
Separation Processes ◽  
Dissolved Air Flotation ◽  
Computational Fluid Dynamics Cfd ◽  
Air Flotation ◽  
Cell Size Distributions ◽  
Dissolved Air

Bioprocesses for the production of renewable energies and materials lack efficient separation processes for the utilized microorganisms such as algae and yeasts. Dissolved air flotation (DAF) and microflotation are promising approaches to overcome this problem. The efficiency of these processes depends on the ability of microorganisms to aggregate with microbubbles in the flotation tank. In this study, different new or adapted aggregation models for microbubbles and microorganisms are compared and investigated for their range of suitability to predict the separation efficiency of microorganisms from fermentation broths. The complexity of the heteroaggregation models range from an algebraic model to a 2D population balance model (PBM) including the formation of clusters containing several bubbles and microorganisms. The effect of bubble and cell size distributions on the flotation efficiency is considered by applying PBMs, as well. To determine the sensitivity of the results on the model assumptions, the modeling approaches are compared, and suggestions for their range of applicability are given. Evaluating the computational fluid dynamics (CFD) of a dissolved air flotation (DAF) system shows the heterogeneity of the fluid dynamics in the flotation tank. Since analysis of the streamlines of the tank show negligible back mixing, the proposed aggregation models are coupled to the CFD data by applying a Lagrangian approach.

scholarly journals Three dimensional Eulerian-Eulerian simulation on hydrodynamics in dissolved air flotation tank with different turbulence models

2017 ◽  
Vol 76 (2) ◽  
pp. 425-433
Author(s):  
Baoqing Deng ◽  
Qiong Ding ◽  
Daqiang Ge
Keyword(s):  
Volume Fraction ◽  
Separation Zone ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Air Bubbles ◽  
Dimensional Model ◽  
Dissolved Air Flotation ◽  
Stratification Structure ◽  
Air Flotation ◽  
Dissolved Air

The Eulerian-Eulerian approach is used to simulate the two phase flow of air and water in a dissolved air flotation (DAF) tank. Unsteady simulation is adopted to obtain the quasi-steady result. The two dimensional model cannot capture the three dimensional feature of flow pattern in the tank. The three dimensional model reproduces the stratification structure observed in the experiment and obtains the satisfactory volume fraction of air bubbles in the separation zone. To account for the turbulence effect, four two-equation turbulence models are evaluated. Although all turbulence models capture the stratification structure in the separation zone, the re-normalization group theory (RNG) k-ɛ model obtains the best agreement with the experimental data. The effect of bubble diameter on the performance of DAF tank is simulated. Small air bubbles can form a big range of high volume fraction of air bubbles, which helps to remove the suspended matters.

Interactions between flocs and bubbles in the separation zone of dissolved air flotation system

2020 ◽  
pp. 143222
Author(s):  
Yong Wang ◽  
Xin Jin ◽  
Shengjiong Yang ◽  
Gen Wang ◽  
Lu Xu ◽  
...  
Keyword(s):  
Separation Zone ◽  
Dissolved Air Flotation ◽  
Air Flotation ◽  
Dissolved Air

Behaviour of air injection nozzles in dissolved air flotation

1995 ◽  
Vol 31 (3-4) ◽  
pp. 25-35 ◽  
Author(s):  
E. M. Rykaart ◽  
J. Haarhoff
Keyword(s):  
Bubble Coalescence ◽  
Second Phase ◽  
Initial Growth ◽  
Two Phase ◽  
Dissolved Air Flotation ◽  
Nozzle Orifice ◽  
Pressure Release ◽  
Air Volume ◽  
Air Flotation ◽  
Dissolved Air

A simple two-phase conceptual model is postulated to explain the initial growth of microbubbles after pressure release in dissolved air flotation. During the first phase bubbles merely expand from existing nucleation centres as air precipitates from solution, without bubble coalescence. This phase ends when all excess air is transferred to the gas phase. During the second phase, the total air volume remains the same, but bubbles continue to grow due to bubble coalescence. This model is used to explain the results from experiments where three different nozzle variations were tested, namely a nozzle with an impinging surface immediately outside the nozzle orifice, a nozzle with a bend in the nozzle channel, and a nozzle with a tapering outlet immediately outside the nozzle orifice. From these experiments, it is inferred that the first phase of bubble growth is completed at approximately 1.7 ms after the start of pressure release.

Enhanced rapid gravity filtration and dissolved air flotation for pre-treatment of river thames reservoir water

1998 ◽  
Vol 37 (2) ◽  
pp. 35-42 ◽  
Author(s):  
M. J. Bauer ◽  
R. Bayley ◽  
M. J. Chipps ◽  
A. Eades ◽  
R. J. Scriven ◽  
...  
Keyword(s):  
Water Treatment ◽  
Water Supply ◽  
21St Century ◽  
Reservoir Water ◽  
Dissolved Air Flotation ◽  
Lowland Rivers ◽  
Air Flotation ◽  
Pre Treatment ◽  
Counter Current ◽  
Dissolved Air

Thames Water treats approximately 2800Ml/d of water originating mainly from the lowland rivers Thames and Lee for supply to over 7.3million customers, principally in the cities of London and Oxford. This paper reviews aspects of Thames Water's research, design and operating experiences of treating algal rich reservoir stored lowland water. Areas covered include experiences of optimising reservoir management, uprating and upgrading of rapid gravity filtration (RGF), standard co-current dissolved air flotation (DAF) and counter-current dissolved air flotation/filtration (COCO-DAFF®) to counter operational problems caused by seasonal blooms of filter blocking algae such as Melosira spp., Aphanizomenon spp. and Anabaena spp. A major programme of uprating and modernisation (inclusion of Advanced Water Treatment: GAC and ozone) of the major works is in progress which, together with the Thames Tunnel Ring Main, will meet London's water supply needs into the 21st Century.

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