Team:ASU/Proof Of Concept

Proof Of Concept

design of the filter

While meeting with algae cultivation experts this summer, we were able to gain inspiration for the large-scale growth of our recombinant Chlamydomonas. Our model incorporates this information by utilizing the general shape and function of a photobioreactor. In an effort to prioritize sustainability, we also felt that an important device specification is the minimization of externally powered facets of our system. Thus, to keep our algae mobile and oxygenated, we required a system to allow movement without a power source. A Tesla valve leverages a cyclone shape to encourage single-direction flow without the use of an energy input.

In general, hydrocyclone technology can be described as the application of centrifugal forces derived from the natural flow of water in a conical vessel to separate particles in mixtures based on individual densities. Through this method, it is possible to filter a pure column of the original liquid in a vertical outflow column. Initial modeling of our device was performed with On Shape CAD design tools to generate 2D sketches and 3D printed plastic vinyl models which can be used for advanced testing.

In order to separate small (10um) cells from our experimental filtrate, we adapted the use of these hydrocyclones. Drawing from the concept of separating small particles with centrifugal force, the utilization of hydrocyclones enables a simplified method of purifying treated water reservoirs in small batches for the express purpose of modeling large-scale filtration processes. In particular, removing Chlamydomonas reinhardtii from treated water posed an issue, as the design of our experiments incorporates direct application and growth of recombineered microbes in drinking water. Calculations based around the partition curve allowed for accurate measurements of flow rate ratios and approximate height and circumferential dimensions, which provided an estimate for the partition number at particle sizes from 5um to 24um. While additional testing and supplemental simulations are required to confirm separation of post-treatment Chlamy, we are confident that this design will effectively remove the remaining live cell contaminants, and deliver filtered drinking water free from arsenic contamination.

The final product filter will be based on the use of non-degradable non-reactive plastic polymers, PVC, and clear tubing. Initial constructs require filters to be designed for general public health safety as well as the proper drainage of engineered microbes to minimize leakage or contamination into the environment. A closed filter system with both pre and post filtration testing will confirm removal of potential contaminants and cellular debris. Theoretically, this model will situate directly into water well extraction plumbing, and provide direct treatment of contaminated groundwater reservoirs. After multiple rounds of filtration, a final test or inspection will confirm safety of drinkable water.

This concept was particularly difficult to model; determining simple and replicable methods of completely removing Chlamy is difficult due to the nature of its size. Instead, natural processes were analyzed and inspiration for the concept of the hydrocyclone was derived from the centrifugal separation of materials and the guided size separation of particles found in ribbed shark stomachs. These two ideas were found in our final design, yet it required significant research and calculations to determine the lower limit of the size of particles which can be effectively filtered. While the range does permit groundwater and chlamy to be filtered, it does not completely remove all contaminants in a single round, and there will likely be a requirement for multiple filtration steps or repeated cycles to be run in order to reach a complete filtration of Chlamy. We aim to improve upon this complication by improving the filtration capacity so as to minimize the time, water, and energy consumed in the process. Another potential point of improvement revolves around the accurate and rapid detection of Chlamy post-treatment. Hematocytometry is currently the most accurate and repeatable method of testing for Chlamy contaminants, and it is another future focus to increase the screening methods to quickly check for contaminants.