Page 449 - Elements of Chemical Reaction Engineering Ebook

Nonelementary Reaction Kinetics Chap. 7

Run 1:
rime (h) 0 10 15 20 30 40 50 60 70
I
Cell Density / 2.7 2.8 15 70 400 600 775 600 525
(cells/mL) X

Run 2:
Time (h) 0 5 10 15 20 30 40 50 60
Cell density 2.7 7 11 80 250 350 350 250 -
(~elIs11nL) X lob4

% H2S 0.1 0.7 0.7 0.8 1.2 4.3 7.5 11.0 12.3

(a) What is the lag time with and without the yeast extract?
(b) What is the difference in the specific growth rates, kmax, of the bacteria
with and without the yeast extract?
(c) How long is the stationary phase?
(d) During which phase does the majority production of H2S occur?
(e) The liquid reactor volume in which these batch experiments were carried
out was 0.2 dm3. If this reactor were converted to a continuous-flow reac-
tor, what would be the corresponding wash-out rate?
W-2& Cell growth with uncompetitive substrate inhibition is taking place in a
CSTR. The cell growth rate law for this system is

with kmax = 1.5 h-l, Ks = 1 g/dm3, KI = 50 g/dm3, Cd = 30 g/dm3,
Y,,, = 0.08, Cd = 0.5 g/dm3, and D = 0.75 h-l.
(a) Make a plot of the steady-state cell concentration C, as a function of D.
(b) Make a plot of the substrate concentration Cs as a function of D on the
same graph as that used for part (a).
(c) Initially, 0.5 g/dm3 of bacteria was placed in the tank containing the sub-
strate and the flow to the tank started. Plot the concentrations of bacteria
and substrate as functions of time.
W-27B A solution containing bacteria at a concentration of 0.001 g/dm3 was fed to a
semibatch reactor. The nutrient was in excess and the growth rate law is first
order in the cell concentration. The reactor was empty at the start of the
experiment. If the concentration of bacteria in the reactor at the end of 2 h is
0.025 g/dm3, what is the specific growth rate k in min-I?
W-28* 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 reservoir. In enhanced microbial oil
recovery, EMOR, bacteria are injected to secrete surfactants to reduce the inter-
facial tension at the oil-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 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