Functional Requirements

Our system needed to allow diffusion of heavy metal ions across a filter boundary without letting the genetically engineered cells out into the environment. To satisfy this requirement, we bought a hollow fiber reactor with a MWCO of 5kd @ 50%, effectively isolating the E.coli cells(0.7-1.4 micrometers)^[1] from the outlet, while allowing diffusion of smaller molecules such as ions across the membrane of the fibers. Additionally, water needed to have an initial flow rate that would allow it to pass through the filter with the cells completely while still allowing time for the diffusion of any heavy metals across the filter membrane to be taken up by the cells. This was accomplished by placing a pump between the reservoir and the hollow fiber reactor. Additional components were added to improve the system, including a carbon water filter before the hollow fiber reactor in order to filter out large particles, which would clog the hollow fiber reactor, and to purify the water of certain compounds which would harm the cells. An additional requirement for the pump in the system was that it had to move water through the large filter first. Also, a battery was required to power the pump. Since this system was modeled to work outside for extended periods of time attached to a factory outlet pipe, a solar panel was used to power a long lasting battery. Finally, a bucket functioned as the reservoir to collect the water from the pipe. The system was scaled down slightly for our purposes, since volume of water was not a concern, so only one hollow fiber reactor to house the cells was necessary.