Effect of Physicochemical Variables on Algal Autoflotation

1992 ◽  
Vol 26 (7-8) ◽  
pp. 1769-1778 ◽  
Author(s):  
S.-I. Lee ◽  
B. Koopman ◽  
E. P. Lincoln
Keyword(s):  
Dissolved Oxygen ◽  
Oxygen Concentration ◽  
Retention Time ◽  
Contact Time ◽  
Pilot Scale ◽  
Dissolved Oxygen Concentration ◽  
Physicochemical Variables ◽  
Rise Rate ◽  
Mixing Intensity ◽  
Maximum Rise

Combined chemical flocculation and autoflotation were examined using pilot scale process with chitosan and alum as flocculants. Positive correlation was observed between dissolved oxygen concentration and rise rate. Rise rate depended entirely on the autoflotation parameters: mixing intensity, retention time, and flocculant contact time. Also, rise rate was influenced by the type of flocculant used. The maximum rise rate with alum was observed to be 70 m/h, whereas that with chitosan was approximately 420 m/h. The efficiency of the flocculation-autoflotation process was superior to that of the flocculation-sedimentation process.

scholarly journals La Alcalinidad Y La Nitrificación En Una Laguna Aireada A Escala Piloto

2016 ◽  
Vol 12 (36) ◽  
pp. 89
Author(s):  
Agustín Leiva Pérez ◽  
Edison Macías Andrade ◽  
Joffre A. Andrade Candell ◽  
Ana M. Aveiga Ortiz ◽  
Sergio S. Alcívar Pinargote
Keyword(s):  
Calcium Carbonate ◽  
Dissolved Oxygen ◽  
Oxygen Concentration ◽  
Ammonium Phosphate ◽  
Pilot Scale ◽  
Process Efficiency ◽  
Dissolved Oxygen Concentration ◽  
Initial Concentration ◽  
Nitrification Process ◽  
The Relationship

It was studied the relationship among means alkalinity concentration as calcium carbonate, and the nitrification process in an aerated oxidation lagoon in batch and pilot scale (1,72 m3 as total volume and 1,46 m3 as effective one) working on a residual synthetic liquid, elaborated with base in sucrose, sulfate and ammonium phosphate. The results demonstrated that when being increased the initial alkalinity in the range from 120 to 360 mg CaCO3/dm3, the nitrification process efficiency increased significantly until the surroundings of the 86%, decreasing when being this with smaller and bigger values that said range. The dissolved oxygen concentration stayed around 4,3 mg/dm3, belonging together with the aerobic character of the microorganisms for nitrification (Nitrosomona and Nitrobacter). The initial concentration of total nitrogen in each one of the 14 processes batch was 38 mg/dm3 and the same one went down to minimum values around 4,56 mg/dm3.

Nonlinear and set-point control of the dissolved oxygen concentration in an activated sludge process

1996 ◽  
Vol 34 (3-4) ◽  
pp. 135-142 ◽  
Author(s):  
Carl-Fredrik Lindberg ◽  
Bengt Carlsson
Keyword(s):  
Dissolved Oxygen ◽  
Activated Sludge ◽  
Oxygen Concentration ◽  
Controller Design ◽  
Ammonia Concentration ◽  
Pilot Scale ◽  
Process Efficiency ◽  
Activated Sludge Process ◽  
Dissolved Oxygen Concentration ◽  
Set Point

Control of the dissolved oxygen concentration (DO) in an activated sludge process is of considerable importance because of economy and process efficiency. A strategy for designing a nonlinear DO controller was developed. The basic idea was to take the nonlinear oxygen transfer function into account in the controller design. Simulations illustrated that a nonlinear DO controller outperforms a standard PI controller. This was also confirmed in a pilot-scale plant experiment. A supervision (set-point) controller for the DO is also outlined. Initial simulations showed promising results where the aeration system is used more efficiently and the effluent ammonia concentration could be maintained low.

scholarly journals Gas–liquid mass transfer characteristics of aviation fuel scrubbing in an aircraft fuel tank

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Li Chaoyue ◽  
Feng Shiyu ◽  
Xu Lei ◽  
Peng Xiaotian ◽  
Yan Yan
Keyword(s):  
Mass Transfer ◽  
Dissolved Oxygen ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Oxygen Concentration ◽  
Gas Holdup ◽  
Aviation Fuel ◽  
Volumetric Mass Transfer Coefficient ◽  
Dissolved Oxygen Concentration ◽  
Liquid Mass Transfer

AbstractDissolved oxygen evolving from aviation fuel leads to an increase in the oxygen concentration in an inert aircraft fuel tank ullage that may increase the flammability of the tank. Aviation fuel scrubbing with nitrogen-enriched air (NEA) can largely reduce the amount of dissolved oxygen and counteract the adverse effect of oxygen evolution. The gas–liquid mass transfer characteristics of aviation fuel scrubbing are investigated using the computational fluid dynamics method, which is verified experimentally. The effects of the NEA bubble diameter, NEA superficial velocity and fuel load on oxygen transfer between NEA and aviation fuel are discussed. Findings from this work indicate that the descent rate of the average dissolved oxygen concentration, gas holdup distribution and volumetric mass transfer coefficient increase with increasing NEA superficial velocity but decrease with increasing bubble diameter and fuel load. When the bubble diameter varies from 1 to 4 mm, the maximum change of descent rate of dissolved oxygen concentration is 18.46%, the gas holdup is 8.73%, the oxygen volumetric mass transfer coefficient is 81.45%. When the NEA superficial velocities varies from 0.04 to 0.10 m/s, the maximum change of descent rate of dissolved oxygen concentration is 146.77%, the gas holdup is 77.14%, the oxygen volumetric mass transfer coefficient is 175.38%. When the fuel load varies from 35 to 80%, the maximum change of descent rate of dissolved oxygen concentration is 21.15%, the gas holdup is 49.54%, the oxygen volumetric mass transfer coefficient is 44.57%. These results provide a better understanding of the gas and liquid mass transfer characteristics of aviation fuel scrubbing in aircraft fuel tanks and can promote the optimal design of fuel scrubbing inerting systems.

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