Experimental Study of Biodegradation of Ethanol and Toluene Vapors

ATP
1
=
Y max
ATP
r
x
+ m
ATP
⋅ C
x
(5-58)
where r ATP is the ATP consumption rate (mol/L-h); the parameter Y ATP is the
reciprocal of parameter K in Equation (5-4), which has been determined in Section
5.3.1.
(4) The following equations (Equations (5-59a) and 5-59b) are applied in the prediction
of oxygen uptake rates and mass transfer rates. Oxygen consumption rate is
calculated as:
Q = μC Y *32 (g/L-h) (5-59a)
O
/
2 x O2
Oxygen mass transfer rate is described by:
Q
o
2 _
mass
*
= k a ⋅ ( C − C )
(5-59b)
L
o
2
o
2
Figures (5-11b) and (5-11c) indicate that oxygen consumption reaches higher
rates when the log phase starts. A peak in the product of μ C
x
, and thus the total oxygen
demand, occurs near the end of the exponential phase and the approach to the stationary
phase. The results also indicate that a higher initial concentration of ethanol results in a
higher biomass level, and thus a higher oxygen demand for cell growth. For instance,
the maximum oxygen demand of 1.6 g/L-h for 6 g/L initial concentration is higher than
that of 0.9 g/L-h for initial concentration of 4 g/L. In the cases of an ethanol initial
concentrations below 6 g/L, the maximum oxygen supply ( k a ⋅
than the maximum oxygen demand ( μ
max
C x
/ Y
O
2
*
L
C o2
) is always higher
). Thus the main resistance to
increased oxygen consumption is microbial metabolism and the reaction appears to be
always growth rate limited, not oxygen mass transfer limited. This agrees with the
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