| Description |
The proper treatment of wastewater generated by human activity is of paramount importance for the preservation of the quality of water sources. For effluents containing high salt concentrations, treatment requires expensive methods that require high energy usage and additional chemicals. Halotolerant bacteria offer a potential alternative to conventional technologies, as they naturally break down organic contaminants to fuel their metabolic processes. Recently, a halotolerant bacterial strain was isolated from the Great Salt Lake that is capable of this type of degradation, even when exposed to high salt concentrations. It has also been found to be electroactive, meaning the bacteria can actually generate electrical power from the chemical energy stored in organic compounds when placed in a microbial fuel cell. If the power output of a microbial fuel cell using these bacteria can be maximized and correlated to the concentrations of organic contaminants in solution, it would be possible for a device using the technology to be employed in the field as a self-powered, on-line biosensor for continuous process control, which is not possible with current analytical techniques. Herein, the electrocatalytic and degradation capabilities of the bacteria are characterized at salt concentrations of 100 g/L. It is shown that degradation efficiencies can be reached that compare to freshwater biological treatment processes. Entrapment of bacteria in calcium alginate hydrogel capsules results in a power density of 12 ± 4 mW/m2 and stable (albeit impaired) degradation over long-term operation. While these results are promising, they are achieved under ideal conditions. In order to begin developing a device that is suitable for field applications, the effects of a continuous non-zero flow rate are explored. Continuous flow results in significant loss of power output, but improved stability of organic degradation. Multiple routes for optimization via chamber geometry, improved anode-bacteria interfacing, and flow control are revealed that will assist in the further development of the technology. |
