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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