Thesis (M.Eng.)--Chulalongkorn University, 2013

This research is divided into three sections. The first part shows the growth of two algae (Ankistrodesmus sp. and Scenedesmus sp.) which were cultivated in the 25 L non-baffled flat panel airlift photobioreactor (NB-FPAP). The result shows that the growths of Ankistrodesmus sp. and Scenedesmus sp. were 9.76±0.36x106 and 2.95±0.48x106, respectively. The second part describes the use of reduced nutrient of BG11 in the cultivation of the two algae. The cultured microalgae with 25%N&P medium provided the best growth condition with the cell density of 1.23±1.68x107 and 2.89±0.83x106 cell mL-1 and the dry weight of 0.70±0.01 and 0.47±0.01 g L-1 for Ankistrodesmus sp. and Scenedesmus sp., respectively. The various nutrient reduction conditions exerted some effect on the biochemical composition of the algae, e.g. lipid contents in Ankistrodesmus sp. from control batch, 25%N&P, 25%P and 25%N were 33±2%wt, 31±0.2%wt, 30±1.0%wt and 29±4.5%wt, respectively. In the last part, the remaining nutrient was reused in the algal culture to examine the growth of such culture. Ankistrodesmus sp. was found to be successfully cultivated in reuse mediums where the cell density from fresh, 1st reuse and 2nd reuse mediums were 9.06±1.40x106, 1.47±0.28x107 and 8.76±2.79x106 cell mL-1, respectively. Biochemical composition of the two algae was also affected from the differences in the medium concentration. Last, this study shows basic concepts for economics assessment, and describes methodologies for the cost estimation of microalgal culture using simple costing equations which is then used to compare the different cost reduction options, e.g. reduced and reused nutrients.