Influence of Mass Transfer Rates at Gas Bubble and Biofilm Surfaces

A total specific mass transfer rate can be defined by Eq. (7.23):

K is the overall mass transfer coefficient.

Notice that c* is the concentration of oxygen at the bubble surface and c'0 is the concentration of oxygen at the biofilm surface.

We write:

respectively:

After dividing Eq. (7.23) by Eq. (7.24) and using Eq. (7.25), we obtain: 1 1 1

total resistance resistance resistance to mass transfer at gas film at biofilm

Equation (7.27) is comparable to the addition of two electrical resistors which are coupled in series. For a high (kLa)G, only mass transfer liquid/solid at the biofilm is relevant (Section 7.4.2) and vice versa (Section 7.4.3). A possible concentration profile is presented as curve VI in Fig. 7.6.

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