Hazardous waste from industrial production is a seemingly irreversible by-product of human presence, and energy is relentlessly demanded by consumers from all across the globe. Currently, energy generated from the sun, wind, and water are the most widely used, but these much-needed environmental solutions are often inefficient, expensive, and resource intensive to either set-up or execute. However, devices known as Microbial fuel cells (MFCs), which use conductive electrodes to convert chemical energy into electrical energy as microbes break down substances, offer a novel, possibly more-efficient option. Additionally, cadmium is a carcinogenic heavy metal that is detrimental to the environment.

The goal of this experiment is to determine if an MFC utilizing P. putida can also be used to remediate cadmium from soil without reducing the electrical output of the device, which traditionally uses non-contaminated soil. The MFCs are made with plastic containers that have holes in the bottom for effluent drainage, soil sterilized in an oven and initially soaked to its water holding capacity, electrodes made with graphite rods surrounded by carbon cloth on both the top and within the soil, and wires connecting them with a 110K ohm resistor as a load in between.

To run the experiment, a control was set up containing only sterilized soil, and 3 levels were created by adding 200 mg of cadmium chloride in liquid form to one fuel cell, 200 mg of cadmium chloride in liquid form and P. putida to the

second, and just P. putida to the third. Maintenance of the fuel cells included daily watering and adding more P. putida. The MFCs each had holes in the bottom and beakers below to collect the effluent. Every other day, this effluent was moved into another beaker along with 60 fronds of duckweed (L. minor), whose hyperaccumulation properties were used to bioindicate the levels of cadmium toxicity. The duckweed mortality rates were tracked over a week long period. Additionally, two beakers, one with distilled water, and one with 200 mg cadmium chloride, were set up alongside the effluent beakers to compare against the beakers of effluent. In tandem, the electricity generation of the MFCs was tracked by connecting the anode and cathode to a multimeter with wires and 1.3K, 10K, and 110K ohm resistor levels between them to measure the power every other day.

The power output of both the P. putida and the P. putida and cadmium chloride fuel cells peaked on the eighth day after the MFCs were created, and there was no significant difference between them. There was, however, a significant difference between the MFCs with P. putida, and those without it, which produced minimal power.

In terms of duckweed mortality rates, for all days, there was no significant difference between the P.putida and P. putida and cadmium chloride MFC's remedial effect on the duckweed mortality rate. These MFC effluent samples had lower mortality rates than both the cadmium chloride effluent and the cadmium chloride control beaker, and this difference was significant on days 4 and 6.

In conclusion, The presence of P. putida in soil positively affects duckweed growth rates by bioremediating cadmium and hence preventing its bioaccumulation by the duckweed in soil effluent. Additionally, use of cadmium contaminated soil instead of sterilized soil does not significantly reduce the power output of MFCs. In terms of further studies, techniques such as spectroscopy and precipitate reactions would have more reliable results, and the incorporation of MFCs into bioswales, or landscape elements that filter polluted water, could be a way to assist in remediation and generate electricity from the chemical process.