A Population Dynamics Investigation of a Self-Sustained Microbial Copper Recovery System
Yimeng Li
Sir Winston Churchill Secondary
Floor Location : M 056 V

Many metal-refining industries produce large amounts of copper-contaminated wastewater
that do not always meet regulatory standards. Over accumulation of this metal (exceeding 4 - 70 mg/L) can lead to serious health disorders, including arthritis, organ/nervous system damage, and in extreme cases, death.

After reviewing conventional copper-removal methods from wastewater, I found that a
number of removal methods including chemical precipitation, ion exchange, and adsorption
have significant disadvantages ranging from heavy chemical demand, high energy consumption, and the production of toxic sludges. Electrochemical deposition methods, in
contrast, require no chemical demand and produce no toxic wastes. Previous research has
reported recovery efficiencies of over 99% of total metal concentrations using this method.
However, these systems operate on large volumes of electricity, making it a much less
sustainable option.

The goal of this research was to develop an inexpensive and sustainable electrochemical
metal recovery system without dependence on external energy inputs; through the
interdisciplinary combination of two fields: (1) microbiology and (2) electrochemistry, a circuit
harnessing electrons produced during the microbial decomposition of sugars was used to power the reduction reaction of copper ions at the cathode of a specially modified electrolytic cell. Research into population dynamics is currently being carried out, investigating the impacts of a pure or mixed microogranism species culture on copper recovery and voltage stability in response to shock and feeding intervals.

Using a highly sensitive catalysis test, copper ions were observed to precipite from the catholyte as previously predicted theoretically. Since this reaction is thermodynamically favourable, a higher peak of electrochemical potential was also observed. Higher currents indicated that the ionic resistance of the cell may have been reduced, leading to higher power densities. It was also found that cells operating on multiple species of microorganisms produce smoother power outputs and respond with greater stability in response to stress intervals.

The findings of this research may be applied to the development of a shock-resistant bioelectrochemical heavy metal recovery system. Future studies should investigate the ability of the system to precipitate multiple metals in solution. However, the results of this project represents one step closer to applying bioelectrochemical systems to heavy metal remediation.