Bubbles aeration

Distinguishing Cohesive aeratable bubble readily spoutable... 

In surface aeration, bubbles are generated at the surface because of the turbulence in the liquid phase. These bubbles are entrained into the bulk liquid by the liquid flow generated by the impeller. For a six-bladed turbine, Van Dierendonck et al. (1968) proposed the following correlation for the minimum impeller speed needed for surface aeration in the absence of gas... 

If trihalomethanes are easily removed from water by aeration (bubbling with air), what does this imply about the vapor pressure of THMs compared to water ... 

Mg. 3.6-10 Information on cohesive, aeratable, bubbling and difScult fluidized beds (Geldart 1973 Molerus 1982)... 

Zahradnik, J., and Kastanek, F. (1979), Gias holdup in uniformly aerated bubble column reactors, Chemical Engineering Communications, 3(4-5) 413-429. 

The function of aeration in a wastewater treatment system is to maintain an aerobic condition. Water, upon exposure to air, tends to estabUsh an equihbrium concentration of dissolved oxygen (DO). Oxygen absorption is controlled by gas solubiUty and diffusion at the gas—hquid interface. Mechanical or artificial aeration may be utilised to speed up this process. Agitating the water, creating drops or a thin layer, or bubbling air through water speeds up absorption because each increases the surface area at the interface. 

The effective saturation depth,, represents the depth of water under which the total pressure (hydrostatic plus atmospheric) would produce a saturation concentration equal to for water ia contact with air at 100% relative humidity. This can be calculated usiag the above equation, based on a spatial average value of T, measured by a clean water test. For design purposes,, can be estimated from clean water test results on similar systems, and it can range from 5 to 50% of tank Hquid depth. Effective depth values for coarse bubble diffused air, fine bubble diffused air, and low speed surface aerators are 26 to 34%, 21 to 44%, and 5 to 7%, of the Hquid depth, respectively. 

Submerged-Culture Generators. Adaptation of the surface-film growth procedure for producing antibiotics to an aerated submerged-culture process has been successful in making vinegar. A mechanical system keeps the bacteria in suspension in the Hquid in the tank, in intimate contact with fine bubbles of air. The excess heat must be removed and the foam, which accumulates at the top of the tank, must be destroyed. 

The aeration factor P has been determined for bubble-cap and sieve plates, and a representative correlation of its values is shown in Fig. 14-32. Values of P in the figure may be calculated from... 

In contrast to vacuum flotation, dissolved-air flotation units can be operated on a continuous basis by the application of pressure. This consists of pressurizing and aerating the process stream and introducing it into the flotation vessel that is maintained at the atmospheric pressure. The reduction of pressure results in the formation of fine air bubbles and the collection of fine particulates to be floated and removed as sludge. 

A tracing of the electrode signal during a cycle of turning aeration off and on is shown in Fig. 24-15. The rate of supply is zero (after bubbles have escaped) in the first portion of the response curve thus, the slope equals the uptake rate by the organisms. When aeration is resumed, both the supply rate and uptake rate terms apply. The values for C — C can be calculated from the data, the slope of the response curve at a given point is measured to get dC/dt, and the equation can be solved for K a because all the other values are known. 

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