Environmental Engineering Reference
In-Depth Information
0.035
a
0.030
P
H
C
PH
PC
HC
0.025
PHC
Control
0.020
0.015
0.010
0.005
0.000
6
12
18
24
48
Time (h)
100
b
P
H
C
PH
PC
HC
PHC
Control
80
60
40
20
0
6
12
18
24
48
Time (h)
Fig. 2
Relative performance of various pretreatment methods application on anae [(
a
)H
2
produc-
tion and (
b
) substrate (COD) removal efficiency [H, heat-shock; P, acid; C, chemical (BESA)]]
[30]
5.5-6.0 is reported to be ideal to avoid both methanogenesis and solventogenesis
[21, 79], which is important for good H
2
production. Effective H
2
production was
observed by maintaining operating pH in and around 6 compared to near neutral
pH [21, 75]. Increase in initial/feeding pH (from acidic to neutral) has resulted in
suppressed H
2
production [21, 26, 31, 32]. However, highly acidic pH (<4.5) is
detrimental to H
2
production as it inactivates H
2
producing bacteria [72, 80].
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