Bubble aeration system

The air flow of the coarse bubble aeration system was then adjusted for the lower BOD of 30 mg/L that is assumed to occur at a depth of 73 m, with each of the 1,160 diffusers maintaining 2 mg/L in a 341 m area. An air flow rate of 29 scmh per diffuser (33,640 scmh total) was determined to be sufficient, assuming that the characteristic equations may be extrapolated to 73 m of depth. For this case, KlA, = 0.018 hr and KlAs = 0.003 hr During the high BOD period at 10 m depth, approximately 3.5 times as much air flow is needed to maintain aerobic conditions. 

A fine bubble aeration system for McCook Reservoir was designed using the same procedure. The system was first designed for the high BOD of 80 mg/L and a depth of 10 m. It was determined that a fine bubble diffuser with an air flow rate of 20 scmh would maintain aerobic conditions for an area of 115 m. From this, 3,438 fine bubble diffusers supplying a total air flow of 68,760 scmh would be needed for the reservoir. For this case, KlAs = 0.003 hr and KlAs = 0.044hr. ... 

A coarse bubble aeration system for McCook Reservoir requires only 1,160 diffusers, approximately one-third of the 3,438 diffusers needed for a fine bubble aeration system. However, significantly less air flow is needed for the fine bubble diffusers in comparison with the coarse bubble diffusers. At the more common depth of 10 m, the air flow required by the fine bubble diffusers was 39% of that required by the coarse bubble diffusers. These considerations and the mixing requirements of the reservoir are a part of the aeration system design. 

Stirred-tank bioreactor with a bubble aeration system (A) schematic representation (B) photograph of a 300 L bioreactor (CIM, Cuba). 

Of course, both of the two coefficients, C and Klo are some combination of the processes considered when equation (8.87) through (8.102) were developed, and are a function of liquid film coefficient across both the bubbles and the free surface, bubble and water surface interfacial area, hydrostatic pressure, the mole ratio of gas in the bubbles, and equilibrium with the atmosphere. These two coefficients, however, can be valuable in the design of an aeration system, as long as (1) the arrangement of diffusers in the water body or tank is similar to the application and (2) the depth of the test is the same as the application. Significant deviations from these two criteria will cause errors in the application of the tests to the field. 

In both the gassed (aerated) stirred tank and in the bubble column, the gas bubbles rise through a liquid, despite the mechanisms of bubble formation in the two types of apparatus being different. In this section, we shall consider some common aspects of the gas bubble - liquid systems in these two types of reactors. 

The sediment from the conical bottoms of the settling boxes is continuously withdrawn into reservoir 17. It is partially removed as dirt and partially sent with pumps 18 and 26 to installation 27 to dehydrate. At the stage of biochemical purification the clarified waste waters from settling boxes 16 self-flow into the top channel of the clarified water of aerotank 10. The aerotank is a six-section open concrete precast reservoir with bubble and aeration systems. All sections of the aerotank function parallel to each other. Each consists of two corridors the oxidation corridor, where the process of biochemical purification takes place, and the regeneration corridor, which serves to prepare silt for purification in the oxidation corridor. 

Matsuoka H, Fukada S Toda K (1992) High oxygen transfer rate in bubble aeration using hollow fiber membrane a proposal of a new aeration system. Biotechnology and Bioengineering 40 346-352. 

Wagner R Lehmann J (1988) The growth and productivity of recombinant animal cells in a bubble-free aeration system. Trends in Biotechnology 6 101-104. 

Consider the situation described in Problem 4.18. According to Eckenfelder (2000), for most types of bubble-diffusion aeration systems the volumetric mass-transfer coefficient will vary with liquid depth Z according to the relationship... 

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