Treatment of wastewater and electricity generation

IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
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TREATMENT OF WASTEWATER AND ELECTRICITY GENERATION
USING MICROBIAL FUEL CELL TECHNOLOGY
B.G. Mahendra1
, Shridhar Mahavarkar2
1
Associate Professor, 2
M.Tech Scholar, Department of Civil Engineering, Poojya Doddappa Appa College of
Engineering, Gulbarga-585102, Karnataka
bgm_pda@yahoo.co.in, shridhar_m21@yahoo.co.in
Abstract
The need for alternate eco-friendly fuel is increasing rapidly with the depletion of non-renewable energy resources. Microbial fuel
cells (MFCs) represent a new form of renewable energy, which converts organic matter into electricity with the help of bacteria
present in wastewater, while simultaneously treating the wastewater. In the present study single chamber (MFC-1) and double
chambered (MFC-2) MFCs were compared for domestic and dairy wastewater treatment and electricity generation. MFC-1 was
proved to be more efficient and found to be producing maximum current of 0.84 mA and 1.02mA whereas MFC-2 produced maximum
current of 0.56mA and 0.58mA from full strength (100%) domestic and dairy wastewater concentrations respectively. COD removal
efficiency achieved in MFC-2 was 88.4% and 86.42% for 100% domestic and dairy wastewater concentrations respectively when
compared with MFC-1 which attained 86.6% and 84.8% respectively for 100% domestic and dairy wastewater concentrations
respectively. The performance of MFC-1 and MFC-2 decreased, when the wastewater concentration was decreased from 100% to
75% and 50% concentrations.
Keywords: Microbial Fuel cell, bioelectricity, wastewater, salt bridge, air cathode.
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1. INTRODUCTION
Increasing human activities are consuming the natural energy
sources leading to the depletion of fossil fuels. The present-
day energy scenario in India and around the globe is
precarious. The need for alternate fuel has made us to initiate
extensive research in identifying a potential, cheap and
renewable source for energy production. The building of the
sustainable society will require reduction of dependency on
fossil fuels and lowering the amount of pollution that is
generated [1]. Current methods to produce energy are not
sustainable, and concerns about climate and global warming
require developing new methods of energy production using
renewable and carbon-neutral sources [2].
Microbial Fuel cell (MFC) is a device designed for the
purpose of electricity generation in the process of wastewater
treatment. Hence it is an ideal solution for sustainable non
renewable source of energy. MFC can be defined as
electrochemical devices that convert the chemical energy
contained in organic matter into electricity by means of
catalytic (metabolic) activity of the living microorganisms [3-
5]. MFCs have gained significance in the last few decades due
to their capability to produce energy, either as electricity or
through hydrogen production, from renewable sources such as
sewage waste and other similar waste sources. The MFC
consists of anode and cathode separated by a proton exchange
membrane or a salt bridge. In the anode chamber, the substrate
is oxidized by microorganisms generating protons and
electrons. The electrons are transferred through an external
circuit, while the protons diffuse through the solution to the
cathode, where electrons combine with protons and oxygen to
form water. There are two kinds of microbial fuel cells:
mediator and mediator-less. In mediator microbial fuel cell,
the bacteria are electrochemically inactive. The bacteria digest
the organic matter and create electrons. The electron transfer
from microbial cells to the electrode is facilitated by
mediators such as thionine, methyl blue, methyl viologen,
humic acid, neutral red and so on[6-7]. Most of the
mediators available are expensive and toxic to bacteria.
Mediator-less microbial fuel cells do not require a mediator
but uses electrochemically active bacteria to transfer electrons
to the electrode (electrons are carried directly from the
bacterial respiratory enzyme to the electrode)[8-9]. Some of
the bacteria which have pili on their external membrane are
able to transfer their electron production via these pili.
Bacteria in mediator-less MFCs typically have
electrochemically-active redox enzymes such as cytochromes
on their outer membrane that can transfer electrons to external
materials [1]
In the present study, mediator-less microbial fuel cells were
used for electric current generation and simultaneous
treatment of the wastewater.

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2. MATERIAL AND METHODS
2.1 Wastewater Samples
The domestic wastewater was collected from Naganahalli
cross nala which is about 2 km away from the
Engg. Gulbarga and the dairy wastewater was collected
Gulbarga Milk Producer’s Society Union Ltd, (Karnataka
Milk Federation) Gulbarga which is about 5 km away
college. Table 1 shows the characteristics of domestic and
dairy wastewater. Both wastewater samples
refrigerator at 40
C before use. The wastewaters were used as
inoculum for all MFC tests without any modifications such as
Table 1:
Sl.No Characteristics
1 pH
2 Colour
3 Total Solids
4 Total Dissolved Solids
5 Suspended Solids
6 BOD3 @ 27
7 COD
8 Chlorides
2.2 MFC Fabrication
Two MFC reactors were fabricated, one was single chamber
MFC and the other was double chambered MFC. The reactors
were fabricated using non-reactive plastic containers with total
volume of 10 liters and the working volume
Graphite rods from pencils were used as both anode and
cathode materials. The arrangement of graphite rods (90mm in
length & 2mm in diameter) was made in such a way as to
provide the maximum surface area for the development of
biofilm on anode. The electrodes were connected using copper
wire. The anode and the cathode chambers were separated by
proton exchange membrane (agar salt bridge
diameter of the agar salt bridge is 5 inches and 1.5 inches
respectively. The electrodes were placed in the chamb
Fig 1: Single Chamber MFC
IJRET: International Journal of Research in Engineering and Technology eISSN: 2319
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2013, Available @ http://www.ijret.org
wastewater was collected from Naganahalli
about 2 km away from the PDA college of
and the dairy wastewater was collected from
Gulbarga Milk Producer’s Society Union Ltd, (Karnataka
5 km away from the
Table 1 shows the characteristics of domestic and
dairy wastewater. Both wastewater samples were kept in
C before use. The wastewaters were used as
inoculum for all MFC tests without any modifications such as
pH adjustments or additions of nutrients etc. Experiments
were conducted using full strength (100%) wastewater, 75%
wastewater and 50% wastewater.
Full strength wastewater: Plain wastewater sample
without any dilution.
75% wastewater: 100% wastewater dilu
distilled water.
50% wastewater: 100% wastewater diluted with 50%
distilled water.
Table 1: Characteristics of domestic and dairy wastewater
Characteristics Unit Domestic wastewater Dairy Wastewater
- 7.4
Colour - Greyish
Total Solids (mg/L) 1140
Total Dissolved Solids (mg/L) 980
Suspended Solids (mg/L) 160
@ 270
C (mg/L) 290
(mg/L) 945
Chlorides (mg/L) 262
ted, one was single chamber
MFC and the other was double chambered MFC. The reactors
reactive plastic containers with total
and the working volume was 8 liters.
rods from pencils were used as both anode and
cathode materials. The arrangement of graphite rods (90mm in
was made in such a way as to
provide the maximum surface area for the development of
connected using copper
wire. The anode and the cathode chambers were separated by
salt bridge). The length and
diameter of the agar salt bridge is 5 inches and 1.5 inches
respectively. The electrodes were placed in the chambers, then
were sealed, made airtight and were checked for water
leakages.
Single chamber MFC: consists of single plastic container
which is used as anode chamber. The agar salt bridge is joined
to the anode chamber. The graphite rods are placed on the
open end of the agar salt bridge which acts as cathode.
Double chamber MFC: consists of two plastic containers. One
plastic container was used as anode chamber and the other as
cathode chamber. The wastewater was fed to the anode
chamber and KCL (catholyte)
The anode and cathode chambers are connected using a agar
salt bridge
Single Chamber MFC Fig 2: Double Chamber MFC
eISSN: 2319-1163 | pISSN: 2321-7308
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278
pH adjustments or additions of nutrients etc. Experiments
were conducted using full strength (100%) wastewater, 75%
wastewater and 50% wastewater.
Full strength wastewater: Plain wastewater sample
75% wastewater: 100% wastewater diluted with 25%
100% wastewater diluted with 50%
haracteristics of domestic and dairy wastewater
Dairy Wastewater
6.8
Whitish
2856
2074
782
654
1868
232
were sealed, made airtight and were checked for water
MFC: consists of single plastic container
which is used as anode chamber. The agar salt bridge is joined
to the anode chamber. The graphite rods are placed on the
agar salt bridge which acts as cathode.
MFC: consists of two plastic containers. One
plastic container was used as anode chamber and the other as
cathode chamber. The wastewater was fed to the anode
chamber and KCL (catholyte) was fed to the cathode chamber.
The anode and cathode chambers are connected using a agar
Double Chamber MFC

IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
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2.3 MFC Operation
The study was conducted by feeding domestic wastewater and
dairy wastewater separately to MFC-1 and MFC-2 with
different strengths separately (i.e., 100% strength without any
dilution, 75% & 50% strengths by diluting with distilled water
25% & 50% respectively) for both the wastewaters. The anode
chamber (anaerobic chamber) was filled with wastewater and
the cathode chamber (aerobic chamber where oxygen was
used as electron acceptor) was filled with KCL solution
(catholyte). The internal wiring of anode and cathode was
connected to a multimeter to complete the circuit. The entire
setup was left for 1 hr for stabilization and the reading in the
multimeter was noted down every 24hrs for 12 days of
operation.
2.4 Monitoring of MFCs
The current (I) in the MFC circuit was monitored at 24hr
intervals using multimeter (Model No. DT830D). The samples
were drawn from the chambers and analysed for the variation
of wastewater characteristics. Analytical procedures followed
were those outlined in Standard Methods for the examination
of water and wastewater characteristics (1995).
3. RESULTS AND DISCUSSIONS
The single and double chambered MFC were run parallel. The
MFCs were operated by feeding domestic and dairy
wastewater with different wastewater concentrations
separately. The effect of wastewater concentration on COD
and TDS removal efficiency and current generation was
observed.
3.1 COD Removal Efficiency
During operation, all MFCs were continuously monitored for
waste (as COD) removal to enumerate the potential of fuel cell
to act as wastewater treatment unit. Both domestic wastewater
and dairy wastewater showed its potential for COD removal
indicating the function of microbes, present in wastewaters in
metabolizing the carbon source as electron donors. It is
evident from experimental data that current generation and
COD removal showed relative compatibility. Continuous
COD removal was observed in both MFC-1 and MFC-2
during 12 days of operation. Initially full strength wastewater
was used in the anodic chamber, and then it was replaced by
75% and 50% wastewater concentrations.
The effect of wastewater concentration on COD removal of
domestic and dairy wastewater in MFC-1 and MFC-2 are
shown in figure 3 to figure 6. Experimental data indicated that
COD removal efficiency was decreased with the decrease of
wastewater concentration from 100% to 75% and 50% in both
MFC-1 and MFC-2. The COD removal efficiency using
domestic wastewater at 100%, 75% and 50% wastewater
concentrations were 86.68%, 76.3% and 64.5% respectively in
MFC-1 and 88.4%, 78.6% and 67.2% respectively in MFC-2.
The COD removal efficiency using dairy wastewater at 100%,
75% and 50% wastewater concentrations were 84.8%, 77.8%
and 72.1% respectively in MFC-1 and 86.42%, 81.7% and
75.2% respectively in MFC-2. This relative slow COD
removal was possibly due to less availability of biodegradable
substrate in 75% and 50% wastewater samples than that of full
strength wastewater leading to competitive inhibition in
microorganisms.
The COD removal efficiency was almost same using full
Strength dairy and domestic wastewater samples, but
relatively slower COD removal was observed in 50%
wastewater concentrations.
3.2 Dissolved Solids Removal Efficiency
Both MFC-1 and MFC-2 showed its potential for dissolved
Solids removal. Initially full strength wastewater was used in
the anodic chamber, and then it was replaced by 75% and 50%
wastewater concentrations. The effect of wastewater
concentration on dissolved solids removal of domestic and
dairy wastewater in MFC-1 and MFC-2 are shown in figure 7
to figure 10. Experimental data indicated that dissolved
removal efficiency was decreased with the decrease of
wastewater concentration from 100% to 75% and 50% in both
MFC-1 and MFC-2. The dissolved solids removal efficiency
using domestic wastewater at 100%, 75% and 50% wastewater
concentrations were 56.2%, 47.2% and 38.2% respectively in
MFC-1 and 53.6%, 45.8% and 34.5% respectively in MFC-2.
The dissolved solids removal efficiency using dairy
wastewater at 100%, 75% and 50% wastewater concentration
were 57.68%, 52.7% and 46.5% respectively in MFC-1 and
55.44%, 49.72% and 45.5% respectively in MFC-2. This
relative slow dissolved solids removal was possibly due to less
availability of biodegradable substrate in 75% and 50%
wastewater samples than that of full strength wastewater
leading to competitive inhibition in microorganisms. The
dissolved solids removal efficiency was almost same using
full strength domestic and dairy wastewater samples, but
relatively slower dissolved solids removal was observed in
75% and 50% wastewater concentrations
.

__________________________________________________________________________________________
Fig.3. COD reduction in domestic
at various concentrations in MFC
Fig.5. COD reduction in dairy wastewater at
at various concentrations in MFC
Fig.7. Dissolved Solids reduction in domestic
wastewater at various concentrations in MFC
__________________________________________________________________________________________
omestic wastewater Fig. 4. COD reduction in domestic wastewater
in MFC-1 at various concentrations in MFC
COD reduction in dairy wastewater at Fig. 6. COD reduction in dairy wastewater
at various concentrations in MFC-1 at various concentrations in MFC
reduction in domestic Fig. 8 Dissolved Solids reduction in domestic
wastewater at various concentrations in MFC-1 wastewater at various concentrations in
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280
. COD reduction in domestic wastewater
at various concentrations in MFC-2
COD reduction in dairy wastewater
1 at various concentrations in MFC-2
reduction in domestic
various concentrations inMFC-2

__________________________________________________________________________________________
Fig.9. Dissolved Solids reduction in dairy
Wastewater at various concentrations in MFC
Current Generation for
Both MFC-1 and MFC-2 were operated with
wastewater samples at different conditions, as feed to support
the formation of biomass and subsequent
electricity. The MFCs were continuously monitored during
experiment and readings were taken after each 24 hr,
inoculation time was considered as time 0. The readings were
noted down for 12 days of MFC operation.
experiments conducted using MFCs showed that electricity
could be generated using different wastewaters.
was measured for each concentration of both
dairy wastewater separately. Initially full strength
was used in the anodic chamber, and then it is replaced by
75% and 50% wastewater concentration. The current showed a
gradual increase for few days, and then it was
The effect of wastewater concentrations on current generation
with the use of domestic and dairy wastewater in MFC
MFC-2 are shown in figure 11 to figure 14. Experimental data
indicated that current generation was decreased with the
decrease of wastewater concentration from 100% to 75% and
50% in both MFC-1 and MFC-2. The maximum current
obtained from domestic wastewater at 100%, 75% and 50%
Fig.11 Current generation
__________________________________________________________________________________________
Dissolved Solids reduction in dairy Fig. 10. Dissolved Solids reduction in dairy
at various concentrations in MFC-1 wastewater at various concentrations inMFC
eneration for Various Wastewater Concentrations in MFC-1 and MFC
were operated with different
wastewater samples at different conditions, as feed to support
and subsequent generation of
electricity. The MFCs were continuously monitored during
experiment and readings were taken after each 24 hr,
The readings were
noted down for 12 days of MFC operation. Preliminary
cted using MFCs showed that electricity
could be generated using different wastewaters. The current
was measured for each concentration of both domestic and
dairy wastewater separately. Initially full strength wastewater
then it is replaced by
75% and 50% wastewater concentration. The current showed a
was declined.
The effect of wastewater concentrations on current generation
airy wastewater in MFC-1 and
. Experimental data
indicated that current generation was decreased with the
decrease of wastewater concentration from 100% to 75% and
maximum current
tewater at 100%, 75% and 50%
wastewater concentration are 0.84 mA, 0.69 mA and 0.5 mA
respectively in MFC-1 and 0.56 mA,
respectively in MFC-2. The
dairy wastewater at 100%, 75% and 50% wastewater
concentration are 1.02 mA, 0.88 mA and 0.78 mA respectively
in MFC-1 and 0.58 mA, 0.52 mA, 0.41 mA respectively in
MFC-2. This variation in current generation
availability of less oxidizable substrates in 75%
wastewater samples.
The current generation from
higher than the domestic wastewater sample. The current
generation was much higher in MFC
MFC-2. Logan et al., (200
air- cathode MFC (compared with the cathode suspe
water) as oxygen transfer to the cathode occurs directly from
air, and thus oxygen does not have to be dissolved in water.
The abundant electron acceptor i.e., oxygen availability in air
is the reason for the higher current generation.
Current generation in domestic Fig. 12 Current generation
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281
Dissolved Solids reduction in dairy
1 wastewater at various concentrations inMFC-2
1 and MFC-2
wastewater concentration are 0.84 mA, 0.69 mA and 0.5 mA
1 and 0.56 mA, 0.4 mA, 0.28 mA
2. The maximum current obtained from
airy wastewater at 100%, 75% and 50% wastewater
on are 1.02 mA, 0.88 mA and 0.78 mA respectively
1 and 0.58 mA, 0.52 mA, 0.41 mA respectively in
This variation in current generation is due to
availability of less oxidizable substrates in 75% and 50%
ion from dairy wastewater sample was
omestic wastewater sample. The current
generation was much higher in MFC-1 when compared with
2. Logan et al., (2007) have reported the advantage of
cathode MFC (compared with the cathode suspended in
water) as oxygen transfer to the cathode occurs directly from
air, and thus oxygen does not have to be dissolved in water.
The abundant electron acceptor i.e., oxygen availability in air
is the reason for the higher current generation.
Current generation in domestic

__________________________________________________________________________________________
Fig.11 Current generation in dairy
CONCLUSIONS
The study demonstrated that microbial fuel cell technology
was able to treat domestic and dairy wastewater successfully,
and microorganisms present in the wastewater are
for electricity generation and COD & TDS
single chamber air cathode MFC proves to be more reliable
because of the reduced cost of construction, low maintenance
and higher electricity generation when compared with double
chambered MFC. The performance of MFCs decreased, with
the decrease in the wastewater concentrat
generation in these systems can be increased, MFC technology
may provide a new method to offset wastewater treatment
plant operating cost, making wastewater treatment more
affordable for developing and developed nations. Thus, the
combination of wastewater treatment along with electricity
production may help in saving money as a cost of wastewater
REFERENCES
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Electricity Production in Microbial Hydrogen Based
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[2] Abhilasha S. M and Sharma V. N., "
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[4] Liu H., Ramnarayanan R. Logan B. E. "
electricity during wastewater treatment using a single
__________________________________________________________________________________________
Current generation in dairy Fig. 12 Current generation in dairy
The study demonstrated that microbial fuel cell technology
was able to treat domestic and dairy wastewater successfully,
microorganisms present in the wastewater are responsible
& TDS removal. The
cathode MFC proves to be more reliable
because of the reduced cost of construction, low maintenance
pared with double
. The performance of MFCs decreased, with
the decrease in the wastewater concentration. If electricity
generation in these systems can be increased, MFC technology
may provide a new method to offset wastewater treatment
plant operating cost, making wastewater treatment more
affordable for developing and developed nations. Thus, the
nation of wastewater treatment along with electricity
production may help in saving money as a cost of wastewater.
Impact of Salt Concentration on
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Edition. Prepared and Published by
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Works Association, Water Pollution Control Federation

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