Environmental Engineering Reference
In-Depth Information
the biodiesel production process, lipid extracted
algae (LEA) has great potential to be used as
animal and fish feed as it is still rich in carbohy-
drates and proteins (Table
8.1
).
mass production can be improved by use of in-
dustrial refusals like wastewater and flue gases.
This strategy not only lowers the cost involved in
biomass generation, but also has several environ-
mental significances. Integrated biorefinary ap-
proach of utilizing industrial wastewater and flue
gases for microalgal biomass generation provides
effective resource management, environmental
benefits, and makes it economically competitive.
Microalgae can assimilate nutrients in wastewa-
ter and CO
2
from flue gases into cellular com-
ponents like carbohydrates and lipids. Microalgal
biomass generated using such industrial refusals
can be directed to synthesis of various end prod-
ucts like biodiesel, biomethane, and animal feed.
c.
Bioactive
compounds
Bioactive compounds are the group of active
chemical products synthesized as secondary me-
tabolite in microalgae. Most of them are having
antimicrobial, antiviral, and antioxidant proper-
ties which are important for microalgae as they
act as protective mechanism during stress condi-
tions. Number of bioactive compounds such as
indoles, terpenes, acetogenins phenols, polysac-
charides, toxins can be obtained from microal-
gae. Marine red algae
Laurencia sp.
is reported as
the most prominent producer of these bioactive
compounds, especially halogenated compounds
(Faulkner
2001
). These bioactive compounds
can be used as pharmaceuticals due to its anti-
microbial, antitubercular, and anticancer activity.
A high-weight polysaccharide from
Chlorella
pyrenoidosa
has very high immunostimulatory
and antitumor effect with potential use in can-
cer therapy (Shi et al.
2007
).
Chlorella vulgaris
produces glycoprotein which shows anticancer
activity through antimetastatic immunopotentia-
tion. Integrated biorefinary with the aim of biofu-
el production from microalgae along with value
added compounds as coproducts is a sustainable
and economically feasible approach. Table
8.1
depicts the different value added products from
microalgae and their application.
a.
Wastewater nutrient medium
Wastewater effluent after primary and second-
ary treatment has various organic and inorganic
constituents. Release of such effluent into envi-
ronment can cause severe problems like eutro-
phication and pollution. Inorganic constituents
of wastewater effluent primarily consists of ni-
trogen and phosphorous. European Commission
Directive 98/15/EEC have specified limits of
10 mgL
−1
total nitrogen and 1 mgL
−1
total phos-
phorous for discharge. Normal values of total
nitrogen and phosphorous in wastewater effluent
are 20-70 and 4-12 mgL
−1
(Arbib et al.
2014
;
Cabanelas et al.
2013
). Discharge of industrial
and domestic wastewater are adding organic and
inorganic nutrients, pathogens, heavy metals,
suspended solids, and oxygen demanding mate-
rial to the existing water resources. Biological
treatment of such tertiary effluent is the possible
solution for this problem. Availability of fresh
water is facing severe risks due to rapid indus-
trialization and socioeconomic development. In
biorefinary concept cultivation of microalgae
using wastewater serves dual purpose of biomass
generation as well as polishing of the effluent
by removing inorganic nutrients (Rawat et al.
2011
; Singh et al.
2014
). Microalgae cultivation
using wastewater for valuable biomass genera-
tion, which can be utilized for several purposes
fulfilling energy and feed requirements, is a
sustainable approach. Water requirement for mi-
8.4.2
Use of Industrial Refusals for
Biomass Production: Wastewater
Nutrient Medium and Flue Gases
Microalgae are simple unicellular photosynthetic
organisms which utilize nutrients from growth
medium and capture atmospheric CO
2
for its en-
ergy requirements and growth. More than half
of energy requirement for microalgal biomass
generation is utilized by carbon dioxide (CO
2
)
and fertilizers supplementation (Orfield et al.
2014
). Economical feasibility of microalgal bio-
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