Bubble dynamics and oxygen transfer in a hypolimnetic aerator

1998 ◽  
Vol 37 (2) ◽  
pp. 293-300 ◽  
Author(s):  
Vickie L. Burris ◽  
John C. Little
Keyword(s):  
Gas Phase ◽  
Bubble Size ◽  
Oxygen Transfer ◽  
Bubble Dynamics ◽  
Water Flow Rate ◽  
Flow Rates ◽  
Wide Range ◽  
The City ◽  
Close Fit ◽  
Water Supply Reservoirs

A hypolimnetic aerator operating in one of the City of Norfolk's water supply reservoirs was tested. Dissolved oxygen (DO) profiles, water flow rate, and gas-phase holdup were measured over a wide range of applied air flow rates. A model that was developed to predict oxygen transfer in a Speece Cone was modified to conform to the conditions of the hypolimnetic aerator. By varying a single parameter (the initial bubble size) the model was found to provide a close fit to the experimental DO profiles as well as the observed gas-phase holdup. The model was used to show that a doubling in oxygen transfer may be achieved if initial bubble size is reduced from 5 mm to 2.5 mm. Knowing the initial bubble size, it should be possible to predict water velocity by incorporating the effect of momentum. Further work is now underway to test this approach and to examine the possibility of extending this generalized model to cover the range of hypolimnetic aeration and oxygenation devices.

Bubble dynamics and oxygen transfer in a speece cone

1998 ◽  
Vol 37 (2) ◽  
pp. 285-292 ◽  
Author(s):  
Daniel F. McGinnis ◽  
John C. Little
Keyword(s):  
Gas Phase ◽  
Oxygen Transfer ◽  
Process Model ◽  
Bubble Dynamics ◽  
Cost Model ◽  
Bubble Diameter ◽  
Water Flow Rate ◽  
Preliminary Design ◽  
Economic Optimization ◽  
Using Data

A model is developed that predicts bubble dynamics and oxygen transfer in a Speece Cone. The model is based on differential mass balances for both gas and water and requires a knowledge of cone dimensions, water flow rate, depth to the cone, and initial bubble diameter produced by the oxygen diffuser. The model calculates the oxygen transfer, nitrogen stripping, and gas-phase holdup within the cone. Experimental data for a Speece Cone have not been published; however, a modified version of the model is tested using data obtained from a hydrodynamically similar full-lift hypolimnetic aerator with good results. This process model, when coupled with a suitable cost model, should prove useful in the preliminary design and economic optimization of Speece Cone oxygenators.

Bubble Formation and Behaviour Under Hypergravity Conditions

2010 ◽  
Author(s):  
Anna Eiden ◽  
Christina Giannopapa ◽  
Balazs Toth ◽  
Alan Dowson
Keyword(s):  
Water Column ◽  
Bubble Size ◽  
Bubble Dynamics ◽  
Bubble Diameter ◽  
Bubble Formation ◽  
Industrial Applications ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Rates ◽  
Aerospace Applications

Bubble formation and behaviour have been studied over decades, but the complex two-phase flow phenomena involved are still not fully understood. In view of the importance of two-phase flow processes in a broad range of industrial applications, such as the chemical process industry, food industry and aerospace applications, it is crucial to obtain a detailed understanding of single and multiple bubble dynamics. Gravity plays an important role in bubble formation and behaviour. Several studies have been conducted on single bubble formation under microgravity conditions, but the effects of gravitational accelerations much larger than on Earth have not been previously documented. In order to gain a full understanding of the effect of gravity on the bubble dynamics and in view of industrial applications, particularly aerospace applications, it is essential to examine bubble formation and behaviour under hypergravity conditions. Bubble formation and behaviour at the surface of a porous material and at a nozzle were investigated at hypergravity levels of 1–20g using the Large Diameter Centrifuge (LDC) at ESA/ESTEC. The formation of air bubbles through a porous filter into a water column was recorded under hypergravity conditions and the obtained data were analysed qualitatively. A decrease in bubble size and an increase in bubble formation frequency with increasing hypergravity levels could be clearly observed. Data for the experiments on air and oil bubble formation at a nozzle into a water column were recorded under hypergravity conditions using a high speed camera (for different nozzle sizes and air/oil flow rates). For the recorded data from the experiments on air and oil bubble formation at a nozzle, a decrease in bubble size and an increase in bubble formation frequency with increasing gravitational acceleration could be observed qualitatively. Quantitative analysis of the data obtained for the experiments on air bubble formation at a nozzle clearly showed a decrease in average bubble diameter with increasing hypergravity levels. The effect of the nozzle diameter on the bubble size was shown to be small and the bubble diameter was larger for higher flow rates.

Evaluation of Opercular Catheterization as a Method for Sampling Water Expired by Fish

1970 ◽  
Vol 27 (9) ◽  
pp. 1627-1635 ◽  
Author(s):  
John C. Davis ◽  
Kenneth Watters
Keyword(s):  
Oxygen Tension ◽  
Posterior Margin ◽  
Water Flow Rate ◽  
Addition Formula ◽  
Oxygen Utilization ◽  
Flow Rates ◽  
Wide Range ◽  
The Mean ◽  
Normal Ventilation ◽  
Cannula Placement

Experiments were carried out on rainbow trout to see if cannulae implanted at different positions on the operculum yield accurate estimates of mean expired oxygen tension. This value is frequently used to calculate utilization or ventilation volume in fish and should therefore be accurately determined.Opercular oxygen tension [Formula: see text] recorded from seven quiescent fish (383–426 g, 10–12 C) in aquaria was highly variable with respect to time and cannula placement. Expired [Formula: see text] recorded from cannulae placed in the middle, upper, or lower part of the posterior margin of the operculum ranged from 54 to 157 mm Hg and was sometimes identical with inspired [Formula: see text]. When the fish were chased, expired oxygen tension usually rose but the magnitude of the rise and its duration were not uniform from cannula placement to placement. Other studies, on 21 trout (217–388 g, 10–12.5 C) whose gills were perfused with water at different flow rates with a mouth tube, indicated that the [Formula: see text] variability existed over a wide range of perfusion rates. In addition, [Formula: see text] levels from all three placements at perfusion rates approximating those of normal ventilation were frequently below the mean expired oxygen tension calculated from oxygen uptake and gill water-flow rate data.It is concluded that opercular cannulae provide poor estimates of mean expired oxygen tension in trout. The use of this technique to determine mean [Formula: see text] could lead to serious errors. It appears that large changes in oxygen utilization can be detected with opercular cannulae but any utilization values determined in this way would likely be erroneous.

Automation of Process Control in Chemical Plant

2015 ◽  
Vol 2 (1) ◽  
pp. 6-12
Author(s):  
Agus Sugiarta ◽  
Houtman P. Siregar ◽  
Dedy Loebis
Keyword(s):  
Process Control ◽  
Pid Control ◽  
Control Algorithm ◽  
Chemical Engineering ◽  
Chemical Plant ◽  
Raw Material ◽  
Flow Rates ◽  
Material Supply ◽  
Wide Range ◽  
Inherent Problem

Automation of process control in chemical plant is an inspiring application field of mechatronicengineering. In order to understand the complexity of the automation and its application requireknowledges of chemical engineering, mechatronic and other numerous interconnected studies.The background of this paper is an inherent problem of overheating due to lack of level controlsystem. The objective of this research is to control the dynamic process of desired level more tightlywhich is able to stabilize raw material supply into the chemical plant system.The chemical plant is operated within a wide range of feed compositions and flow rates whichmake the process control become difficult. This research uses modelling for efficiency reason andanalyzes the model by PID control algorithm along with its simulations by using Matlab.

Death in the City

2017 ◽  
Author(s):  
Kathryn A. Sloan
Keyword(s):  
Scientific Inquiry ◽  
The United States ◽  
Violent Death ◽  
Special Relationship ◽  
Intimate Friend ◽  
Counter Narrative ◽  
Wide Range ◽  
European Heritage ◽  
The City ◽  
The Temple

Popular culture has long conflated Mexico with the macabre. Some persuasive intellectuals argue that Mexicans have a special relationship with death, formed in the crucible of their hybrid Aztec-European heritage. Death is their intimate friend; death is mocked and accepted with irony and fatalistic abandon. The commonplace nature of death desensitizes Mexicans to suffering. Death, simply put, defines Mexico. There must have been historical actors who looked away from human misery, but to essentialize a diverse group of people as possessing a unique death cult delights those who want to see the exotic in Mexico or distinguish that society from its peers. Examining tragic and untimely death—namely self-annihilation—reveals a counter narrative. What could be more chilling than suicide, especially the violent death of the young? What desperation or madness pushed the victim to raise the gun to the temple or slip the noose around the neck? A close examination of a wide range of twentieth-century historical documents proves that Mexicans did not accept death with a cavalier chuckle nor develop a unique death cult, for that matter. Quite the reverse, Mexicans behaved just as their contemporaries did in Austria, France, England, and the United States. They devoted scientific inquiry to the malady and mourned the loss of each life to suicide.

Museum Preserves in the Sphere of “Cultural Tourism”: Through the Example of the Cultural Preserves of Tatarstan

2019 ◽  
Vol 9 (4) ◽  
pp. 193-198
Author(s):  
Lyudmila S. Timofeeva ◽  
Albina R. Akhmetova ◽  
Liliya R. Galimzyanova ◽  
Roman R. Nizaev ◽  
Svetlana E. Nikitina
Keyword(s):  
19Th Century ◽  
Art Museum ◽  
Medium Size ◽  
Business Elite ◽  
Wide Range ◽  
The Subject ◽  
Tourist Center ◽  
Regional Authorities ◽  
The 19Th Century ◽  
The City

Abstract The article studies the existence experience of historical cities as centers of tourism development as in the case of Elabuga. The city of Elabuga is among the historical cities of Russia. The major role in the development of the city as a tourist center is played by the Elabuga State Historical-Architectural and Art Museum-Reserve. The object of the research in the article is Elabuga as a medium-size historical city. The subject of the research is the activity of the museum-reserve which contributes to the preservation and development of the historical look of Elabuga and increases its attractiveness to tourists. The tourism attractiveness of Elabuga is obtained primarily through the presence of the perfectly preserved historical center of the city with the blocks of integral buildings of the 19th century. The Elabuga State Historical-Architectural and Art Museum-Reserve, which emerged in 1989, is currently an object of historical and cultural heritage of federal importance. Museum-reserves with their significant territories and rich historical, cultural and natural heritage have unique resources for the implementation of large partnership projects. Such projects are not only aimed at attracting a wide range of tourists, but also stimulate interest in the reserve from the business elite, municipal and regional authorities. The most famous example is the Spasskaya Fair which revived in 2008 in Elabuga. It was held in the city since the second half of the 19th century, and was widely known throughout Russia. The process of the revival and successful development of the fair can be viewed as the creation of a special tourist event contributing to the formation of new and currently important tourism products.

Intrinsic Stacking Interactions of Natural and Artificial Nucleobases

2019 ◽  
Author(s):  
Drew P. Harding ◽  
Laura J. Kingsley ◽  
Glen Spraggon ◽  
Steven Wheeler
Keyword(s):  
Gas Phase ◽  
Electrostatic Interactions ◽  
Density Functional ◽  
Molecular Descriptors ◽  
Stacking Interactions ◽  
Interaction Energies ◽  
Functional Theory ◽  
Binding Partner ◽  
Heavy Atoms ◽  
Wide Range

The intrinsic (gas-phase) stacking energies of natural and artificial nucleobases were explored using density functional theory (DFT) and correlated ab initio methods. Ranking the stacking strength of natural nucleobase dimers revealed a preference in binding partner similar to that seen from experiments, namely G > C > A > T > U. Decomposition of these interaction energies using symmetry-adapted perturbation theory (SAPT) showed that these dispersion dominated interactions are modulated by electrostatics. Artificial nucleobases showed a similar stacking preference for natural nucleobases and were also modulated by electrostatic interactions. A robust predictive multivariate model was developed that quantitively predicts the maximum stacking interaction between natural and a wide range of artificial nucleobases using molecular descriptors based on computed electrostatic potentials (ESPs) and the number of heavy atoms. This model should find utility in designing artificial nucleobase analogs that exhibit stacking interactions comparable to those of natural nucleobases. Further analysis of the descriptors in this model unveil the origin of superior stacking abilities of certain nucleobases, including cytosine and guanine.

Nitrogen Removal from Anaerobically-Treated Leachate

1984 ◽  
Vol 19 (1) ◽  
pp. 87-100
Author(s):  
D. Prasad ◽  
J.G. Henry ◽  
P. Elefsiniotis
Keyword(s):  
Nitrogen Removal ◽  
Air Flow ◽  
Operating Conditions ◽  
Air Flow Rate ◽  
Flow Rates ◽  
Anaerobic Filter ◽  
Ph Values ◽  
Wide Range ◽  
Ammonia Desorption ◽  
Effects Of Ph

Abstract Laboratory studies were conducted to demonstrate the effectiveness of diffused aeration for the removal of ammonia from the effluent of an anaerobic filter treating leachate. The effects of pH, temperature and air flow on the process were studied. The coefficient of desorption of ammonia, KD for the anaerobic filter effluent (TKN 75 mg/L with NH3-N 88%) was determined at pH values of 9, 10 and 11, temperatures of 10, 15, 20, 30 and 35°C, and air flow rates of 50, 120, and 190 cm3/sec/L. Results indicated that nitrogen removal from the effluent of anaerobic filters by ammonia desorption was feasible. Removals exceeding 90% were obtained with 8 hours aeration at pH of 10, a temperature of 20°C, and an air flow rate of 190 cm3/sec/L. Ammonia desorption coefficients, KD, determined at other temperatures and air flow rates can be used to predict ammonia removals under a wide range of operating conditions.

Bulking and Foaming Organism Control at Phoenix, AZ WWTP

1992 ◽  
Vol 26 (3-4) ◽  
pp. 461-472 ◽  
Author(s):  
O. E. Albertson ◽  
P. Hendricks
Keyword(s):  
Wastewater Treatment ◽  
Nitrogen Removal ◽  
Retention Time ◽  
Oxygen Transfer ◽  
Average Rate ◽  
Oxygen Transfer Efficiency ◽  
Solids Retention ◽  
Total Nitrogen Removal ◽  
The Cost ◽  
The City

A 1630 L/s activated sludge plant at Phoenix was limited to an average rate of 1050 L/s and operated, at 400-600 mg/L MLSS and 0.8-1.3 day solids retention time (SRT) due to bulking sludge and limited clarification capacity. Higher SRTs also produced uncontrolled Nocardia foaming and low dissolved oxygen due to partial nitrification. The City retained the services of a team of consultants to resolve these problems as well as to upgrade the plant to provide nitrification and total nitrogen removal. An anoxic selector design was implemented within the existing basin and the clarifiers were modified to improve inlet design and sludge transport. The modified advanced wastewater treatment (AWT) plant operating at 1450 L/s has averaged an effluent of 7.6 mg/L BOD5, 8.2 mg/L TSS, 1.3 mg/L NH4N, 4.1 mg/L NO3N and 2.9 mg/L TP. Oxygen transfer efficiency has increased about 80% in the nitrification-denitrification (NdeN) mode. The cost of modification/upgrading to AWT was approximately $730,000 and a 400 L/s increase in hydraulic capacity was realized. Upgrading costs were $5.63/m3 ($0.02/gal.)

Forest path condition monitoring based on crowd-based trajectory data analysis

2020 ◽  
pp. 1-18
Author(s):  
Francisco Arcas-Tunez ◽  
Fernando Terroso-Saenz
Keyword(s):  
Information Acquisition ◽  
Road Network ◽  
Road Networks ◽  
Trajectory Data ◽  
Country Road ◽  
Wide Range ◽  
Sport Activities ◽  
Path Condition ◽  
Spatio Temporal ◽  
The City

The development of Road Information Acquisition Systems (RIASs) based on the Mobile Crowdsensing (MCS) paradigm has been widely studied for the last years. In that sense, most of the existing MCS-based RIASs focus on urban road networks and assume a car-based scenario. However, there exist a scarcity of approaches that pay attention to rural and country road networks. In that sense, forest paths are used for a wide range of recreational and sport activities by many different people and they can be also affected by different problems or obstacles blocking them. As a result, this work introduces SAMARITAN, a framework for rural-road network monitoring based on MCS. SAMARITAN analyzes the spatio-temporal trajectories from cyclists extracted from the fitness application Strava so as to uncover potential obstacles in a target road network. The framework has been evaluated in a real-world network of forest paths in the city of Cieza (Spain) showing quite promising results.

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