Bataller, Butch Galicia (2018-10). Design, Fabrication and Assessment of a Short Tank Internally-Illuminated Concentric-Tube Airlift Photobioreactor for the Cultivation of Spirulina platensis. Doctoral Dissertation.
Thesis
A comprehensive study on the bench-scale cultivation of Spirulina in a short-tank concentric-tube internally-illuminated airlift photobioreactor was presented. This study includes: (a) the development of a rapid and non-destructive analytical method for biochemical analysis of the Spirulina biomass via FTIR spectroscopy and PLS regression; (b) design, construction and hydrodynamic and mass transfer characterization of a 3-L photobioreactor; and (c) performance assessment of the reactor in cultivating Spirulina. A preliminary techno-economic analysis was also performed. The use of FTIR-ATR spectroscopy and PLS-regression for biochemical analysis was successfully demonstrated. PLS-regression was found to have better predictive power than multipoint regression. While, comparison of the new method with conventional biochemical methods revealed statistically similar results. This new method reduced the time for sample preparation and eliminated the extraction of target biomolecule for analysis. It has also been valuable in monitoring the growth and biochemical changes in Spirulina biomass during growth. For the second part, a 3-L internally-illuminated concentric-tube airlift photobioreactor with a H/D of approximately 2.0 and Avr/Avd of less than 1.0 was designed. From the hydrodynamic and mass transfer characteristics, it was hypothesized that at 0.3 vvm air flow rate would result to better growth performance due to better liquid circulation (shorter light/dark cycle) and lesser accumulation of dissolved oxygen. This hypothesis was proven to be correct. The third part was to assess the reactor's performance in cultivating Spirulina. The effects of light intensity, air flow rate, and initial biomass concentration on growth parameters such as specific growth rate, overall and daily biomass and product productivity, and photosynthetic efficiency were tested. From the results, it was recommended that the right combination of light intensity, air flow rate, and initial biomass concentration must be selected to produce the highest biomass throughput. A smart control of these factors with respect to the instantaneous population density must also be developed to attain better growth performance. On the other hand, preliminary techno-economic analysis revealed that producing Spirulina powder from 80-mv3 short tank internally-illuminated airlift photobioreactor is feasible. A few ways to further reduce the production cost were also presented.
