Biomedical Engineering Reference
In-Depth Information
7.6. Awastewater stream is treated biologically with a reactor containing immobilized cells
in porous particles.
Table P7.6
shows the rate data obtained for a particular particle size
when the external mass transfer effects are negligible. Internal mass transfer effects are
known to be present. Determine if Michaelis
e
Menten equation, i.e.
r
max
S
K
m
þ S
r ¼
even mass transfer effects are not negligible. Determine the apparent kinetic
parameters.
S
0
, g/L
0.00
0.10
0.25
0.50
1.00
2.00
r
, g/(L
$
h)
0.000
0.085
0.200
0.360
0.630
1.000
7.7. An understanding of bacteria transport in porous media is vital to the efficient operation
of the water flooding of petroleum reservoirs. Bacteria can have both beneficial and
harmful effects on the performance of the reservoir. In enhanced microbial oil recovery,
EMOR, bacteria are injected to secrete surfactants to reduce the interfacial tension at the
oil
e
water interface so that the oil will flow out more easily. However, under some
circumstances the bacteria can be harmful, by plugging the pore space (due to excessive
growth and wall attachment) and thereby block the flow of water and oil. One bacteria
that has been studied,
Leuconostoc mesenteroides
, has the unusual behavior that when it is
injected into a porous medium and fed sucrose, it greatly reduces the flow (i.e. damages
the formation and reduces permeability). When the bacteria are fed fructose or glucose,
there is no damage to the porous medium (Lappan R. and Fogler H.S.
SPE Prod. Eng
., 7:
167
e
171, 1992). The cell concentration,
X
, is given in Table P8.13 as a function of time for
different initial sucrose concentrations.
(a)
From
Table P7.7
, determine the time to reach the stationary phase, the saturation
m
G
¼
m
max
S
constant,
K
S
, and the maximum specific growth rate,
m
max
.
r
¼ m
G
X
and
S
.
K
S
þ
S
is the substrate concentration, while
X
is the cell concentration.
(b)
Will an inhibition model of the form
n
X
X
0
X
N
m
G
¼ m
max
1
where
n
and
X
N
are parameters, fit the data?
7.8. Yogurt is produced by a mixed culture of
Lactobacillus bulgaricus
and
Streptococcus
thermophilus
to pasteurize milk. At a temperature of 110
F, the bacteria grow and
produce lactic acid. The acid contributes flavor and causes the proteins to coagulate,
giving the characteristic properties of yogurt. When sufficient acid has been produced
(about 0.90%), the yogurt is cooled and stored until eaten by consumers. A lactic acid
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