Experimental Study of Biodegradation of Ethanol and Toluene Vapors

where µ is the total specific growth rate (h -1 ), and the summation is taken over the n
substrates. The specific growth rate on each substrate, µ i , is related to the concentration
of all the substrates through a multi-substrate Monod growth relationship by assuming
that all components in the mixture share a common rate-limiting enzyme reaction
pathway. The resulting equation is:
μ max,
iSi
μ
i
= (2-10)
n
K
si
K
si
+ ∑ Si
K
j
sj
Bailey and Ollis (1986) proposed the following two compound inhibition equation:
μ
maxS
μ =
(2-11)
S + K (1 + I / )
s
K i
where I = liquid concentration of a competing compound (mg/L) and K i is an inhibition
constant (mg/L). This equation was applied to model biodegradation of mixtures with
presence of toluene by a group of researchers (Machado and Grady Jr., 1989; Chang et
al., 1993; Criddle, 1993; Bielefeld and Stensel, 1999).
2.3.4 Metabolic Modeling
The metabolic reactions for the aerobic metabolism of substrate can be separated
into two groups: the energy consuming reactions and the energy generating reactions.
The energy consuming reactions are due to the production of biomass while the energy
producing reactions include substrate catabolism and oxidative phosphorylation. The
system being considered is assumed to be of constant volume and it contains a certain
number of moles of biomass. The stoichiometry of the energy-generating and energy-
27