Environmental Engineering Reference
In-Depth Information
Table 8.2
Microalgae grown on various industrial wastewater and their biomass and lipid yields
Microalgae
Wastewater
N removal
(%)
P removal
(%)
Biomass
(gL
−1
D
−1
)
Lipid yield
(%)
Reference
Chlorella
zofingiensis
Dairy wastewater
51.7
97.5
-
17.9
(Huo et al.
2012
)
Microalgae
consortium
Carpet mill effluent
> 96
> 96
0.039
12
(Chinnasamy
et al.
2010
)
Chlamydomonas sp.
TAI-2
Industrial wastewater
100
33
-
18.4
(Wu et al.
2012
)
Chlorella
saccharophila
Carpet mill effluent
-
-
0.023
18.1
(Chinnasamy
et al.
2010
)
Botryococcus
braunii
Carpet mill effluent
-
-
0.034
13.2
(Chinnasamy
et al.
2010
)
croalgae cultivation in open pond is as high as
11-13 million L ha
−1
year
−1
(Chinnasamy et al.
2010
). Wastewater utilization for microalgae cul-
tivation can reduce fresh WF as well as can pro-
vide treated water for other use. Wastewater has
very high concentrations of nutrients specifically
N and P along with some toxic metals. Costly
chemical treatment methods are required to re-
move these nutrients. The potential shown by mi-
croalgae to grow with minimal fresh water and
accumulate nutrients and metals can be exploited
to treat such domestic and industrial wastewa-
ter. Cultivation of microalgae needs water and
supply of inorganic nutrients like nitrogen and
phosphorous. Nitrogen and phosphorous plays
a very important role in microalgal physiology,
and thus needs to be supplied through growth
medium. The nutrient supplementation contrib-
utes a major portion in the overall cost of micro-
algae cultivation. Utilization of tertiary industrial
or domestic wastewater as growth medium can
supply required nutrients for microalgae. Nutri-
ents cost can be reduced if wastewater effluent
is used as the nutrient medium. Various microal-
gal strains have been studied for their growth in
wastewater nutrient medium. Most studied strain
for wastewater utilization is
Chlorella
sp, due to
its robustness and application in biodiesel pro-
duction (Huo et al.
2012
; Ramanna et al.
2014
).
Table
8.2
shows different microalgal strains
grown on various industrial wastewater and their
biomass and lipid yields. Wastewater medium
has lower N and P content as compared to com-
mercial media used for microalgae cultivation.
Limitation of nutrients for stress induced lipid
accumulation is a well accepted method in mi-
croalgal biofuel process. Ramanna et al. (
2014
)
when grew Chlorella sorokiniana on wastewater
medium and standard BG11 medium, lipid yield
was found to be higher in wastewater grown bio-
mass (10.7 % DCW) compared to BG11 grown
biomass (8.08 % DCW). Utilization of wastewa-
ter growth medium for microalgal biomass gen-
eration thus provides several benefits like cheap
nutrient source, enhanced lipid productivity, re-
ducing risk of eutrophication, reduce fresh WF,
and polished tertiary treated wastewater for other
uses. Overall, this approach provides sustainabil-
ity, commercial compatibility, and environmental
benefits for microalgal biofuel production pro-
cess.
b.
Utilization of
flue gases
CO
2
is a major contributor of green house gases
(GHG) which causes global warming. Global
warming poses serious threat causing climate
changes, glacial melting, rise in ocean level, re-
duced food production, extinction of species, and
many other environmental problems. Globally, it
has seen as a serious issue, and thus Kyoto Proto-
col has been promoted by United Nations with the
objective of reducing GHG emission by 5.2 % on
the basis of emission in 1990 (Pires et al.
2012
).
Several strategies are practiced for capture and
sequestration of CO
2
. Most widely used method
is carbon capture and storage. CO
2
is captured
from emission sources like power plants and ce-
ment industries. CO
2
can be captured by several
methods viz., adsorption, absorption, separation
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