Environmental Engineering Reference
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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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