MICROBIAL FUEL CELL (MFC) TECHNOLOGY FOR HOUSEHOLD WASTE REDUCTION AND BIOENE...
Erin Fuller WW Poster
1. Quantification of dilute heavy metal removal
mechanisms by microbial electrolysis cells
Erin Fuller, Younggy Kim
Department of Civil Engineering
McMaster University
Contact: fullee1@mcmaster.ca
Introduction
Heavy metals are an increasing concern in
wastewater as global industry expands. They can
be toxic even at low concentration, are not
biodegradable and are prone to bioaccumulation
in soil [1]. Sludge from wastewater treatment
facilities have agricultural applications, thus it is
pertinent to develop efficient, cost-effective
methods to remove heavy metals [2].
Current technologies (ie. ion exchange and
membrane filtration) have high capital and
operational cost [1]. Microbial electrolysis cells
(MECs) show promise for high efficiency, low-
cost treatment. Reactors are low-cost, operated at
neutral pH and room temperature, the biofilm is
developed from wastewater effluent and require
little energy [3]. MECs generate electricity from
exoelectrogenic bacteria on the anode by
oxidizing organics in wastewater and reducing
metals to solid deposits at the cathode. External
power is required to overcome the
thermodynamic barrier.
Eight metals were selected for simultaneous
removal. It is expected that Cu, Au and Ag will
aggressively reduce out of solution, Pb, Cd, Cr
and Zn will reduce, albeit slower, and Mn will
not come out of solution based on required
electrochemical potential (E) calculated from the
Nernst equation [4].
𝐸 = 𝐸°
−
𝑅𝑇
𝑧𝐹
𝑙𝑛
𝑎 𝑜𝑥
𝑎 𝑟𝑒𝑑
𝑉 𝑣𝑠 𝑆𝐻𝐸
Figure 2. Typical MEC setup. Orange
ovals represent exoelectrogenic
bacteria and white circles represent
generated hydrogen gas. Acetic acid is
used by the biofilm as an electron donor
to generate current. At the cathode,
electrons are consumed to reduce metal
cations and water. The power supply
lowers the cathode potential, enabling
electron flow.
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
E(VvsSHE)
1 ug/L 10 ug/L 100 ug/L
E (anode) E (cathode)
Figure 1. Half-cell reduction potentials at 21°C and
various cation concentrations.
Objectives
• explore the effects of low concentration and applied voltage on removal efficiency
• quantify the distribution of removal mechanism contribution
• explore reduction competition between metals simultaneously treated
Materials and Methods
• Feed 2 g/L sodium acetate, 5 mM PBS buffer,
trace vitamins and minerals and electrolyte
solution every 4 days, 135 cycles (1.5 years)
• Operated at neutral pH. Mixing is provided
• Two electrolyte concentrations: 0.05, 0.5 μM
• Two voltage conditions: 0.6, 1.2 V vs SHE
• Anode: graphite brush, cut to 1”x1”x½” to
prevent excess bioadsorption. Steel rod as current
collector
• Cathode: nickel foil with titanium wire
• Reactor: polypropylene block, 50 mL
• Concentration analysis done with ICP-OES
Figure 4. Four reactors are connected to a power supply.
The current is read across a resistor in series. Reactor four
shown in detail.
Results
Outlook
References
Acknowledgements
Thank you to Hui Guo and Pengyi Yuan for their help in reactor set-up and
Monica Han and Peter Koudys for their help on laboratory equipment
operation and reactor construction. Funding from Discovery Grants (435547-
2013, Natural Science and Engineering Research Council of Canada), Canada
Research Chairs Program (950-2320518), Leaders Opportunity Fund (31604,
Canada Foundation for Innovation) and the Small Infrastructure Funds (31604,
Ontario Research Fund).
[1] F. Fu and Q. Wang, “Removal of heavy metal ions from wastewaters: A
review,” J. Environ. Manage., vol. 92, no. 3, pp. 407–418, 2011.
[2] I. Metcalf & Eddy, Wastewater Engineering: Treatment and Reuse, 4th ed.
McGraw-Hill, 2002.
[3] B. Logan, D. Call, S. Cheng, and H. V. M. Hamelers, “Critical Review
Microbial Electrolysis Cells for High Yield Hydrogen Gas Production from
Organic Matter,” Environ. Sci. Technol., vol. 42, no. 23, pp. 8630–8640, 2008.
[4] O. Modin, X. Wang, X. Wu, S. Rauch, and K. K. Fedje,
“Bioelectrochemical recovery of Cu, Pb, Cd, and Zn from dilute solutions,” J.
Hazard. Mater., vol. 235–236, pp. 291–297, 2012.
[5] D. R. Lindsay, K. J. Farley, and R. F. Carbonaro, “Oxidation of Cr(III) to
Cr(VI) during chlorination of drinking water.,” J. Environ. Monit., vol. 14, no.
7, pp. 1789–97, 2012.
[6] Federal-Provincial-Territorial Committee on Drinking Water of,
“Guidelines for Canadian Drinking Water Quality Summary Table,” Heal.
Canada, 2014.
[7] N. Colantonio, H. Guo, and Y. Kim, “Effect of Cd(II) concentration on the
removal mechanism and efficiency in microbial electrolysis cells.” 2016.
Using bioelectrochemical systems in wastewater
treatment can remove organic content, nutrients,
heavy metals otherwise difficult and expensive to
remove and is nearly an energy-sustainable process.
Precious metals can be recovered to generate a
revenue stream from the treatment process. Sludge
will also be safer in agricultural applications.
Developing MEC technology could make a
beneficial impact on the wastewater treatment’s
environmental impact and economic potential.
MECs are currently establishing the
biofilm and are producing current. This
means reduction reactions at the cathode
are expected as exoelectrogenic
organisms in the biofilm are producing
current in response to substrate
consumption.
Dips in current represent decreasing or
absence of available substrate. Sharp
increases represent the start of a cycle
where fresh feed is added to the reactor.
Figure 3. Current production in each reactor
during the inoculation stage.
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0 2 4 6 8 10
Current(mA)
Time (days)
MEC 1 MEC 2 MEC 3 MEC 4
Metals were chosen based on their suitability to removal by MECs,
their importance as a pollutant, toxicity and if they are a precious
metal capable of being recovered in the case of Ag and Au.
Chlorination in water treatment oxidizes Cr(III) to Cr(VI) [5]. At the
point of MEC treatment, Cr(III) is the prevalent form of aqueous
chromium. Concentrations were chosen based on instrumentation
detection limits in ICP-OES analysis and Canadian Drinking Water
Quality guidelines [6].
Mechanisms of cation removal include bioadsorption, chemical
precipitation and electrodeposition (reduction at the cathode).
Contribution of each mechanism is quantified by dissolving the
cathode and deposits in acid (quantifying electrodeposition
contribution). A similar treatment is done on a portion of the anode
(quantifying bioadsorption), and visual inspection for chemical
precipitation followed by ICP-OES analysis if apparent, but
precipitation not expected at concentrations 100 μg/L and below [7].