Bursic 2:00
L07
THE INTEGRATION OF MICROBIAL FUEL CELLS IN CONSTRUCTED
WETLANDS
Adalee Jacobs (axj1@pitt.edu)
INTRODUCTION
As the population increases, pollution has increased.
Pollution comes in many forms with one example being
wastewater. As a result, the government of the United States
has implemented wastewater treatment plants in order to
regulate the amount of contaminants permitted back into our
homes and into surrounding bodies of water. However,
engineers and environmentalists are looking to treat
wastewater – water that H. Perlman in “Wastewater
Treatment Water Use What is wastewater, and why treat it?”
says “includes substances such as human waste, food scraps,
oils, soaps, and chemicals” – in more effective ways [1].
During the summer of 2014, I had the chance to construct and
operate a microbial fuel cell at Saint Francis University.
While there, I was intrigued by how environmental engineers
were looking at renewable power sources that run on solely
organic matter. One such method currently being studied in
treating wastewater is the use of microbial fuel cells in
constructed wetlands [2]. Although fairly new in terms of
wastewater treatment methods, I agree with the statement –
made by Ong et al. in “Hybrid system up-flow constructed
wetland integrated with microbial fuel cell for simultaneous
wastewater treatment and electricity generation” – that
microbial fuel cells have “great potential to treat waste water”
and can generate clean electricity [3]. Keeping the
environment free of pollutants as well as making use of
renewable energy from wastewater should be reason enough
for scientists and engineers to continue studying the applied
benefits of microbial fuel cells to treat wastewater.
microbial fuel cells which will better clean the water and
harness more energy from organic matter.
WHAT ARE CONSTRUCTED WETLANDMICROBIAL FUEL CELLS?
A constructed wetland is a cheap, effective technology
that wastewater treatment plants use in order to remove
pollutants from water while a microbial fuel cell (MFC)
produces electricity from organic matter [3]. Each technology
has strengths which complement the other by overcoming
weaknesses of the other technology [2]. Specifically, the main
problems are that constructed wetlands require a large amount
of land in comparison to MFCs whereas MFCs have yet to be
used in real-world plants [2]. Therefore with the creation of
constructed wetland-microbial fuel cells (CW-MFCs),
engineers and scientists can eliminate problems each
individual technology has as well as filter water better and
generate clean power with one innovation [2].
How does a constructed wetland-microbial fuel cell
work?
In a CW-MFC, the components of the MFC replace the
majority of the gravel of the constructed wetland while
preserving the plant species located at the top of the wetland
[2]. Figure 1 illustrates a simple schematic of a CW-MFC.
The constructed wetland portion focuses mainly on the
filtering of contaminants from water whereas the MFC works
to produce energy from the organic matter [3]. However, both
portions do improve the efficiency of the other [2].
WHY TREAT WASTEWATER?
Wastewater treatment plants keep the environment and
people healthy by cleaning water that is released back into a
river or ocean and reused as tap water. If water was not
treated, many chemicals, heavy metals, and microbes would
leak back into our water sources and cause harm to organisms
[2]. For example, overexposure to nitrates – a compound
filtered out of water in a treatment plant – can result in
complications involving the heart and lungs, cancer, or death
[4]. While wastewater treatment plants are able to remove the
majority of harmful pollutants, they have yet to eliminate all
of the potent substances from water [2]. In addition to this, the
majority of the energy in the organic matter from wastewater
is not utilized [5]. Currently, a portion of organic waste is used
as fertilizer for crops and as energy; however, about seventyfive percent of waste is not utilized [5]. Thus, wastewater
treatment plants need to implement constructed wetland-
University of Pittsburgh, Swanson School of Engineering 1
2015-10-06
FIGURE 1 [6]
A CW-MFC of length 690 mm
Adalee Jacobs
In regards to the MFC portion, the oxygen from plants
assists the microbes in releasing electrons in the wastewater
[3]. To illustrate, the organic matter releases negativelycharged electrons which are attracted to a positively-charged
anode [3]. After traveling to the anode, the electrons then flow
towards a cathode by means of a circuit which creates an
electrical current – energy – along with water [3]. The
creation of pure water by the MFC supplements the filtering
of water by the constructed wetland [3]. As a result, clean
water and electricity are available for use.
CW-MFCs have the potential to save wastewater
treatment plants millions of dollars annually by providing
renewable energy to the plants while also cleaning the water
more effectively [3]. For instance, the need to spend over
$40,000,000 to treat water would no longer exist for
ALCOSAN with the integration of CW-MFCs [9]. However
at the present time, the main problems of integrating CWMFCs into wastewater treatment plants are that the size of a
CW-MFC is small and, Ong et al. says, the idea of CW-MFCs
is “still in its infancy” [3]. Thus, the question arises whether
to implement many small CW-MFCs or scale-up a current
model of a CW-MFC [2]. Each option has its own difficulties;
yet, the potential of CW-MFCs outweighs these
complications [2]. We may not realize how CW-MFCs can
affect us yet every time we flush a toilet or use the sink, we
are part of a cycle. A cycle that consists of us using water that
plants have cleaned and contributing to the wastewater that
ends up back in the plants. As a result of our water usage in
the United States of America, a portion of our taxes fund
wastewater treatment plants and if the cost of better quality
water is reduced due to new technology, the taxes can be
allocated to other programs such as education or health care.
I believe if more people were aware of the benefits CW-MFCs
had on them, CW-MFCs could be working in wastewater
treatment plants by 2025 if not sooner.
WHY ARE CONSTRUCTED WETLANDMICROBIAL FUEL CELLS IMPORTANT?
Although only in the beginning stages of research, the
application of CW-MFCs in the real world is highly likely due
to the promising results of current research. In fact, the
addition of MFCs has improved the majority of the aspects
involved with treating wastewater [2]. According to Yadav et
al. in “The effects of microbial fuel cell integration into
constructed wetland on the performance on constructed
wetland”, CW-MFCs performed “27-49% better than
Normal-CW for chemical oxygen demand (COD) removal”,
meaning CW-MFCs were better at removing organic waste
from the water [2]. Furthermore in “Operating a two-stage
microbial fuel cell-constructed wetland for fuller wastewater
treatment and more efficient electricity generation”, Doherty
and Zhao found the removal of nitrates and nitrites had
“efficiencies of 81 ± 5.7% and 98 ± 4.2%, respectively” [6].
In addition to releasing cleaner water back into the
environment, wastewater treatment plants are able to use the
organic matter as a “clean” energy source that can decrease
costs of operating the plants [2]. Yadav writes that the
maximum power density was found to be 320.8 mW/m3 and
the maximum current density was found to be 422.2 mA/m3
[2]. Although the numbers may seem small, an individual
CW-MFC at this time is on average less than a meter cubed,
smaller than a queen-size bed [6]. As a matter of fact in
“Microbial Fuel Technologies | Bruce Logan”, B. Logan
estimates that we could extract a minimum of 40 GW of
energy per year from organic matter in wastewater and that is
after factoring in the energy that would be used to power the
treatment plant [7]. For example if CW-MFCs were added to
the Allegheny County Sanitary Authority (ALCOSAN) – a
230,000 square meter wastewater treatment plant located in
Pittsburgh, Pennsylvania – the plant would have enough
power to run its operations as well as have a surplus of energy
[8]. In conclusion, it is important for engineers to continue to
work on implementing CW-MFCs in wastewater treatment
plants.
CONCLUSION
Wastewater treatment plants provide the individual with
clean water every day. If people were able to have access to
cleaner and cheaper water, why would we not take the
opportunity? I know the potential CW-MFCs could have on
the future of wastewater treatment plants and can predict how
the integration of such technology would impact the society
as a whole as well as the individual person. CW-MFCs would
provide cleaner water as well as create a cheap, renewable
energy source, two benefits from one technology.
REFERENCES
[1] H. Perlman. (2015, July 30) “Wastewater Treatment
Water Use What is wastewater, and why treat it?” USGS.
(Online blog). http://water.usgs.gov/edu/wuww.html
[2] P. Srivastava, A.K. Yadav, B.K. Mishra. (2015). “The
effects of microbial fuel cell integration into constructed
wetland on the performance of constructed wetland.”
Bioresource Technology. (Online article). DOI:
10.1016/j.fiortech.2015.05.072. pp. 223-230
[3] L. Ho, H.K. Lehl, S. Ong, et al. (2015). “Hybrid system
up-flow constructed wetland integrated with microbial fuel
cell for simultaneous wastewater treatment and electricity
generation.” Bioresource Technology. (Online article) DOI:
10.1016/j.biortech.2015.03.014. pp. 270-275
[4] X. Zhao, L. Chen, H. Zhang. (2013, March 1). “Nitrate
and Ammonia Contaminations in Drinking Water and the
Why continue research on constructed wetlandmicrobial fuel cells?
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Adalee Jacobs
Affecting Factors in Hailun, Northeast China.” Journal of
Environmental Health. (Online article)
http://web.b.ebscohost.com/ehost/pdfviewer/pdfviewer?sid=
f38a3cac-c88b-4652-97945eb77d3192da%40sessionmgr111&vid=4&hid=101 pp. 2834
[5] A. Aupperlee. (2015, June 28). “Human-waste fertilizer
aids farmers, worries some Ohio residents.” Trib Total
Media. (Online article).
http://triblive.com/news/editorspicks/8593330-74/sludgealcosan-synagro#axzz3mzkb5MfK
[6] L. Doherty, Y. Zhao. (2015). “Operating a two-stage
microbial fuel cell-constructed wetland for fuller wastewater
treatment and more efficient electricity generation.” Water
Science & Technology. (Online Article). DOI:
10.2166/wst.2015.212. pp. 421-428
[7] “Microbial Fuel Technologies | Bruce Logan.” Michigan
Engineering. (2015). (Video).
https://www.youtube.com/watch?v=su6PfYeMrsI
[8] J. Clark. (2015, September 2). “ALCOSAN Launches
“Flush Cleveland” Campaign in Open House Competition.”
Alcosan. (Online article).
http://www.alcosan.org/LinkClick.aspx?link=NewsReleases
%2fNewsRelease_Flush+Cleveland_9_2_15.pdf&tabid=79
&mid=460
[9] “Allegheny Country Sanitary Authority Financial
Statements and Required Supplementary and Supplementary
Information.” (2015, March 24). Auditor’s Report. Maher
Duessel.
ACKNOWLEDGEMENTS
A sincere thank you to Ms. Emelyn Fuhrman, Ms. Anne
Schwan, Mr. Ethan McElhinny, Mr. Kim Jacobs, and Miss
Tyra Pitts for their support and guidance on writing this
paper.
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