Optimization of photobioreactor for production of biodiesel part ii : effect of light on microalgae

• Main Author: Goh, Yvonne Qian Ru.
• Other Authors: Lau Wai Man
• Format: Final Year Project
• Language: English
• Published: 2010
• Subjects: DRNTU::Engineering::Chemical engineering::Biotechnology
• Online Access: http://hdl.handle.net/10356/39650
• Institution: Nanyang Technological University

This study focuses on the investigation of effects of light on growth of microalgae Chlorella sp. ATCC 14854. Pre-experimental phase involved medium selection, medium modification and the determination of optimal temperature and pH range suitable for growth. It was found that R-medium was best suited for growth of Chlorella sp. ATCC 14854; and the optimal temperatures were 28±1°C and pH 6 respectively. R-medium was further modified to yield higher concentrations of iron, magnesium, nitrogen and phosphorus so as to eliminate nutrient limitation or imbalance. Effects of short duration mixing-induced light/dark cycling were studied at four average surface light intensities -- 82μmol/m2.s, 260μmol/m2.s, 370μmol/m2.s and 590μmol/m2.s. Using 82μmol/m2.s, growth performances using both draft tube sizes almost paralleled. However, it was found that the 74mm draft tube runs with a longer cycle time of 1.2s and smaller light fraction of 0.48 outperformed the 54mm draft tube runs with a shorter cycle time of 1.0s and a larger light fraction of 0.72. Results suggested that a light/dark cycling becomes important for higher light fluxes, and longer dark time in relation to light time promoted better growth performance. Lumostatic operations were also investigated based on two light-control parameters—optimal surface light intensity and critical average surface light intensity, where the latter was herein proposed based on investigation of trend of chlorophyll a content. Further work will need to be done to ascertain the superiority of either method.