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5.4 CHAPTER t'IVE
FIGURE 5.2 View of a packed column installation. (Source: U.S. Environmental Pro-
tection Agency.)
Diffusion-Type Aeration
Diffusion- or bubble-type aerators accomplish gas transfer by discharging bubbles of air
into water by means of air injection devices. Compared with packed columns, diffused
aeration provides less interfacial area for mass transfer but greater liquid contact time. On
the other hand, packed columns provide a greater effective area but lower liquid contact
time.
