Experimental Study of Biodegradation of Ethanol and Toluene Vapors

2.4.1 Batch Reactor
In a batch reactor, the reactants are initially added into the reactor and left to
react for a certain period of time. The reactant can be either a pure chemical reaction or
a biochemical one. The content of the reactor is kept mixed in order to have a uniform
composition throughout the reactor. The process is unsteady state (changes with time)
and the reactor content is discharged at the end of the process. The performance
equation of a batch reactor can be derived from the material balance of substrate as
(Levenspiel, 1972):
dX = r (2-13)
x
dt
dS
dt
r s
= −
(2-14)
in which t is the time, X is the biomass mass concentrations and r x is the rate of biomass
formation, S is the substrate mass concentrations and r s is the rate of substrate
consumption. Solving Equations (2-13) and (2-14) will give the concentrations of
biomass (X) and substrate (S) at any desired time. If the temperature of the reactor
changes, an energy balance will also be necessary for solving the performance equation
of the batch reactor.
2.4.2 Fedbatch Reactors
In a fedbatch (semi-batch) reactor, an initial amount of reactant and/or medium
is charged into the reactor (initial charge) which is also kept well mixed. More reactants
or medium are added to the reactor as the reaction proceeds. The process is unsteady
state and the contents of the reactor need to be discharged after a certain period of time.
Fedbatch processes are often used in fermentation to minimize substrate inhibition, or to
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