Date of Award

8-2018

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Environmental Engineering and Earth Sciences

Committee Member

Dr. Yi Zheng, Committee Chair

Committee Member

Dr. Qiushi Chen, Committee Co-Chair

Committee Member

Dr. David Ladner

Committee Member

Dr. Terry Walker

Abstract

Here on Earth biocementation has been extensively studied and holds promise in producing a more energy efficient and environmentally benign alternative construction materials compared to the standard method of production. This research is focused on developing bioprocesses to produce bioconcrete columns using potentially Mars-compatible microalgae and simulated Martian regolith. A marine microalga, Thraustochytrium striatum was tested to make Martian regolith-based columns in the presence of CaCl2/urea.

Three different biogrouting methods were investigated including simultaneous, sequential and batch circulation of microalga cell biomass and CaCl2/urea in the columns. The need of post-biogrouting column soaking was studied to develop an understanding of its relationship with unconfined compressional strength (UCS) of the columns. X-ray diffraction (XRD) was used to identify the formation of CaCO3 along with using a scanning electron microscope (SEM) to identify the microstructure of the deposited CaCO3. Carbonite titration analysis and hydraulic conductivity tests were conducted to further characterize the biocemented columns.

T. striatum is capable of biocementation and can produce urease to induce CaCO3

precipitation for regolith columns, with an average CaCO3concentration of 12.21%±0.79%. Post-biogrouting column soaking has shown to have an inverse relationship with UCS, and therefore is not needed in the process of manufacturing biocemented columns. Removing the biomass from the growth media and resuspending in it DDI water produced a better biogrout solution because the salts within the growth media reduced the strength of the columns. The average hydraulic conductivity of the biocemented columns was 2.06±0.69×10-3 cm/s, about 50% less than that of the untreated Martian regolith column. Batch feed biogrout recirculation was found to be the best method of production with producing columns with average UCS values of 732.40±117.84 kPa.

Calcium acetate was used to simulate the anaerobic digestion of food waste in the production of acetic acid, which would further be utilized to dissolve limestone to produce a stable source of calcium for the manufacturing of biocement. The utilization of calcium acetate instead of CaCl2 resulted in a significant decrease in the permeability of the biocemented columns compared to the untreated MMS regolith by 90%. T. stratum was able to utilize acetate as a carbon source to precipitate carbonate, instead of using urea through urea hydrolysis. Lastly, the average CaCO3 concentration within the columns produced with calcium acetate was 11.50%±0.34%. Therefore, future research in optimizing the regolith particle size, biomass loading rate, and nutrient loading rate will need to be conducted to improve the UCS of biocemented columns.

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