Gas Transfer from Bubbles

Schierholz et al. (2006) applied equations (8.98) to (8.102) to various tank experiments of depths that varied from 2.25 to 32 m in depth. The results were that a value of the bubble transfer coefficient, T LA/l and the surface transfer coefficient, 

EXAMPLE 9.4 Sizing bubble diffusers for a reservoir with combined sewer overflow 

Aercor CB (2001 WES) Aercor CB (1995 WES) Sanitaire CB (LACSD) Envirex CB (LACSD) FMC CB (LACSD) Bauer CB (LACSD) Kenics CB (LACSD) Norton FB (LACSD) FMC FB (LACSD) Pentech FB (LACSD) Aercor CB (Lock Tests) Sanitaire CB (Sanitaire) - Perfect Fit 

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.  

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