Experimental Study of Biodegradation of Ethanol and Toluene Vapors

The continuous models can capture all significant physical phenomena since
they were derived based on fundamental biochemical principles and mass balances.
Equations (5-65), (5-69), (5-71), and (5-73) illustrate that biomass concentrations are a
function of the operating conditions such as inlet and outlet concentrations in liquid and
gas phases, dilution rates, yield coefficients on each substrate, and the maintenance
terms under different conditions. If the operating conditions change, the model reflects
the physical reality of this change. For instance, for continuous removal of ethanol at
steady state conditions, biomass concentration increases as the amount of ethanol
introduced from gas phase increases when other conditions remain the same (see
Figures 5-14a and 5-14b). For example, results in Figure 5-7 show that the steady state
continuous model predicts the changes in biomass concentrations due to the increase of
ethanol gas inlet concentration. However, there was not sufficient time to generate more
data to determine the predictive ability of the model.
The limitation of the simulation is the parameters obtained from the limited (but
time consuming) number of experiments such as m, Y m . As discussed in Section 5.4.2,
this maintenance term of growth depends on the growth environment such as the type of
substrate and its concentration, operating mode (batch or continuous), and conditions of
other nutrients such as pH, oxygen and ammonia. Moreover, in reality the P/O ratio (δ )
may also vary with the operating conditions. Therefore, it is recommended that more
detailed on-line measurements, including ATP, oxygen and carbon dioxide, be carried
out in order to verify and improve the model in the future.
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