Environmental Engineering Reference
In-Depth Information
10.4.1
Highly Biodegradable
Wastewater
and TDS from wastewater, apart from carbon
content (Mohanakrishna et al.
2010a
; Pant et al.
2012
; Venkata Mohan et al.
2014
). Application
of BES was also extended to treat solid waste, as
well as toxic aromatic hydrocarbons under in situ
biopotential (Venkata Mohan and Chandrasekhar
2011
). Studies related to the mechanism of pol-
lutant reduction and their role in electron transfer
will give a spectrum of practical feasibility of this
technology for the sustainable removal of toxic
pollutants.
The characteristics of wastewater vary based on
the raw materials used as the source for its gen-
eration. Domestic wastewater is considered to be
simple and highly biodegradable in nature with
low substrate load and hence its treatment in BES
is highly efficient and faster but the power gen-
eration lasts only for few hours (Venkata Mohan
et al.
2009a
). Dairy wastewater rich in milk-based
waste components such as lactate, proteins, etc.
is also simple in nature and depicted higher treat-
ment efficiency (Venkata Mohan et al.
2010a
).
Similarly, kitchen waste, food waste, vegetable
waste, cheese waste, potato wastewater, etc.
comes under highly biodegradable wastewater
(Pant et al.
2010
; ElMekawy et al.
2013
). Waste-
water from these sources mainly contains a lot of
organic carbon in the form of carbohydrates and
proteins, which can be easily degraded by almost
all the bacteria. The energy gain from this type of
wastes is also very high along with higher treat-
ment efficiency. Moreover, microbes can also
function effectively under higher organic loading
rates this type of wastewaters, that avoids the ne-
cessity of feed dilution. Various types of biode-
gradable wastewater used in BES including their
treatment efficiency are depicted in Table
10.1
.
10.4
Wastewater Treatment
The nature of the substrate is regarded as one of
the most important biological factors that can
influence the treatment efficiency of BES, thus
affecting the electron recovery. BES can utilize
a wide range of substrates as electron donors/
acceptors, including inorganic and organic mol-
ecules. However, the efficiency of electron re-
covery depends on the oxidation state of the elec-
tron donor and it's ratio to the microbe that can
oxidize it. Among the simple substrates, glucose
and acetate are most widely used anodic fuels but
other simple substrates, viz. sucrose, starch, bu-
tyrate, dextran, peptone, ethanol, etc. were also
evaluated in BES, with a prime motto of power
generation. Apart from these simple substrates,
BES also depicted versatility in utilizing a wide
range of simple to complex organic wastes. Waste
generated from different origins, viz. industries,
commercial areas, residential areas, etc. were
considered as potential electron donors in BES.
The waste having higher biodegradability such
as domestic wastewater, dairy based wastewater,
food wastewater, vegetable waste, etc. will have
good power generation capacity, while the indus-
trial wastewater having low biodegradability will
depict lower power output. Still wastewater is a
potential substrate for MFC because of its dual
advantages of converting negative valued waste
into bioenergy.
10.4.2
Complex/Low Biodegradable
Wastewater
On the other end, BES can also handle highly
complex and low biodegradable wastewater such
as distillery-based wastewater, pharmaceutical
wastewater, lignin-based wastewater etc. A de-
tailed list of complex wastewater used as sub-
strates in BES was provided in Table
10.1
. The
complex nature and low biodegradability of these
wastewaters creates difficulty in conversion to
the reducing equivalents, and moreover, the elec-
trons and protons generated will be accepted by
the pollutants/components of wastewater them-
selves (intermediary acceptors) for further oxida-
tion, generating lower current densities. Colour
removal from industrial wastewater such as dis-
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