Biomedical Engineering Reference
In-Depth Information
4.3. Effect of Cr(VI) on Growth Kinetics
Figure 5 shows the experimental results of biomass growth for each algal species. Growth
in the presence of different Cr(VI) concentrations is compared with that obtained using
Cr(VI)-free culture medium. Cr(VI) concentrations of 1 mg l
-1
do not affect or slightly
improve algal growth. However, higher concentrations cause an inhibitory influence on
growth kinetics. The more marked effect is visible in
C. vulgaris
culture, since growth is
almost interrupted for Cr(VI) concentration as low as 5 mg l
-1
. In the absence of Cr(VI) or for
low Cr(VI) concentrations (1 mg l
-1
), pH increases over time from the initial value around 6.5
to about 7.4-7.8 (Figure 6). As it could be expected, pH rises more slowly or even remains
constant when inhibition occurs.
200
400
180
350
160
Chlorella Fusca
300
140
250
120
Chlorella Vulgaris
0 mg Cr/l
1 mg Cr/l
5 mg Cr/l
25 mg Cr/l
200
100
150
80
0 mg Cr/l
1 mg Cr/l
5 mg Cr/l
50 mg Cr/l
60
100
40
50
20
0
0
0
100
200
300
400
500
600
700
0
100
200
300
400
500
600
7
Ti m e ( h )
Ti m e ( h )
400
600
350
500
0 mg Cr/l
1 mg Cr/l
5 mg Cr/l
25 mg Cr/l
300
400
0 mg Cr/l
1 mg Cr/l
5 mg Cr/l
25 mg Cr/l
250
Scenedesmus Acutus
300
200
150
200
Scenedesmus Obliquus
100
100
50
0
0
0
100
200
300
400
500
600
7
0
100
200
300
400
500
600
700
Ti m e ( h )
Ti m e ( h )
Figure 5. Effect of Cr(VI) on algal growth as a function of time (T = 21-22 ºC; initial pH = 6.6-6.7;
arrow indicates the moment of Cr addition). (—) Logistic model fittings.
