BS in Materials Engineering
Materials Engineering Department
A system was designed to mitigate the accelerated process of anthropogenic eutrophication. This system aimed to contain Chlorella Vulgaris microalgae cells within an enclosed polymer membrane pouch while allowing for water and nutrients to diffuse through the pouch. As a test model, a 10 gallon aquarium was partitioned into three sections using polycarbonate membranes with 1 micron pore diameters. Each section was then gradually filled with a deionized water and Bristol solution recommended for microalgae growth. Phosphate and nitrate were added to Section A of the aquarium and allowed to diffuse throughout the tank. A water pump was used to agitate the solution and increase the diffusion rates of the nutrients. Samples were drawn periodically from section A and section C. A spectrophotometer was then used to analyze the phosphate and nitrate concentration of the samples. The resulting diffusion rates were graphed for trials with and without Chlorella Vulgaris cells present in section B of the tank to quantify the rate and overall amount of nutrient absorption by this microalgae.
The membrane was shown to successfully contain the microalgae cells within section B, so long as it was properly adhered to the aquarium. Both nitrate and phosphate were readily able to permeate the polycarbonate membrane and diffuse throughout the tank. Quantitative analysis of chlorella cell population failed to yield representative data. However, qualitative observations found that microalgae growth had occurred within Section B. Nutrient diffusion trends were highly linear. With the exception of two data sets that had substantially lower values, all data sets demonstrated R2 values of at least 0.9059 and 0.985 at the highest. This behavior was contrary to that predicted prior to conducting the experiment.
As anticipated, rates of nutrient concentration change into Section C were lower when chlorella was present in Section B than when it was not added to the system. For phosphate, the rate at which this concentration increased in Section C was 1.4 µg/L/min lower when chlorella was added to Section B. For nitrate, the rate of concentration increase in Section C was 11 µg/L/min lower when chlorella was added to Section B. These results suggest that microalgae within the tank was successful in absorbing both nitrate and phosphate as they diffused throughout the tank.
Overall, results suggest that the proposed system would be able to absorb excess nutrients present within a eutrophic water system, thereby mitigating the ill effects of this biological state. However, collected results were based on a limited number of trials and thus were not robust. Further investigation should be undertaken to confirm the quantitative results obtained in this project.