Environmental Engineering Reference
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a
d
1.7
µm
e
b
333 nm
c
Fig. 4
SEM images of (
a
) acidophilic biofilm (X 2,500) (
b
) isolated strain (X 1,800) (
c
) iso-
lated strain (X 2,200); (
d
) TEM images of isolate captured at different magnification (1.7
μ
mand
333 nm) [26]
in H
2
production rate was observed with an increase in OLR when chemical
wastewater was used as the substrate [22]. H
2
production was also found to decrease
with an increase in OLR when dairy wastewater was used as substrate [31]. Similar
observations with substrate loading have been reported in the literature [101, 102].
Decreased H
2
production may also be due to end product inhibition by over-
accumulated (supersaturated) soluble metabolites in the liquid phase at high OLRs
[102]. However, each wastewater has its own threshold value, which relates to the
system microenvironment and desired output [4, 22, 26, 31]. Feed consisting of only
glucose as substrate showed a low H
2
yield, while feed with chemical wastewater
admixed either with glucose or domestic sewage as co-substrates showed a positive
influence on the H
2
generation rate [21, 71]. Domestic sewage addition showed a
positive affect on the acidogenic fermentation process due to supplementation of
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