Environmental Engineering Reference
In-Depth Information
2.5
Bioaugmentation
2.0
1.5
1.0
0.5
0.0
72
96
120
140
164
187
210
232
256
278
Time (h)
Fig. 6 H 2 production with the function of reactor operation (before and after augmentation with
selective enriched H 2 producing culture) [25]
Suspended growth (SG-control) of cultures showed inhibition in terms of both
H 2 production and substrate degradation, especially at higher loading rates. On
the other hand, attached growth showed marked improvement in both H 2 yields
and substrate degradation efficiency, particularly at higher loading rates. Self-
immobilization on SBA-15 showed nine times higher H 2 production than the
non-attached (SG) operation. Attached growth on GAC and PAC also showed
marked improvement in the process performance at higher OLRs compared to SG
operation. Immobilization of microflora on the support medium as biofilm results
in high biomass hold up, which enabled the operation of the process at signifi-
cantly higher liquid throughputs and OLRs. Immobilization protects the cells from
environmental/chemical toxicity and from predation by other organisms and may
enhance survival under extreme environments with relatively high survival rates
even after prolonged storage [26, 92, 126]. Immobilized cells survive even at high
temperatures.
7.6 Activators to Enhance H 2 Production
Some trace metals, organic compounds, nutrients and H + concentration generally
have a stimulating effect on the enzymatic activity pertaining to biochemical pro-
cesses and might enhance process efficiency if added at optmial concentrations
(Table 5). Hydrogenases that are able to catalyze the oxidation of H 2 or the reduc-
tion of H + are classified into two major families: the [Ni-Fe] hydrogenases and
the [Fe-Fe] hydrogenases, according to the metal content at their active site [130].
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