There are two ways that we could account for the growth of microorganisms. One is to account for the number of living cells, and the other is to account for the mass of the living cells. We shall use the latter. A mass balance on the microorganisms in a CSTR (chemostat) (e.g., margin figure and Figure 9-24) of constant volume is
Cell Mass Balance
The corresponding substrate balance is
In most systems, the entering ...