Experimental Study of Biodegradation of Ethanol and Toluene Vapors

5.6.3 Theoretical Predictions of Steady State Simultaneous Removal of Ethanol and
Toluene Mixtures
For the growth on the mixture of ethanol/toluene or benzyl alcohol/toluene,
toluene acts as a growth inhibitor only (Bailey and Ollis, 1986; Chang et al, 1993;
Bielefeldt and Stensel, 1999). There is no growth on toluene, but toluene gets consumed
proportional to the growth rate on the actual growth substrate. The following
assumptions are made in the prediction of the steady state removal of ethanol and
toluene mixtures. The growth on the mixture of ethanol and toluene follows the two
compound inhibition equation (Bailey and Ollis, 1986), which agrees with the
metabolic model that applied with the data for ethanol/toluene bioremediation.
μ
maxCe
μ =
(5-70)
C + K (1 + I / K )
e
e
i
where μ max = μ e,max , I = liquid concentration of a competing compound (mg/L) and K i
is an inhibition constant (mg/L). In this case, I = C t, and
K i
= 1.71mg
/ L for toluene
was used (Chang et al., 1993). For ethanol (see Table 5.1): μ = 0. 56 h -1 ,and
K e
= 0.59g
/ L .
The biomass concentration can be predicted by:
m
C
x
1 max
tx
et
= max
⋅ ( φe
⋅Yex
+
T
⋅Y
( μ + m )
φ
)
(5-49)
where φ
e
and φ T
are the net amounts of ethanol and toluene flowing into the system
(In-Out), respectively. Considering the fact that ethanol in the outlet gas steam is
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