LAUSR

ABSTRACT A lab scale externally illuminated photobioreactor was used to evaluate the lipid productivity (LP) of microalga Chlorella protothecoides (SAG-211-10C) cultivated in municipal secondary waste water supplemented with CO2. Experiments were conducted in two stages: growth phase (GP) and nitrogen starvation phase (NSP). The influence of five environmental factors (light intensity [LI], photoperiod, temperature, concentration of CO2, pH) on LP of Chlorella protothecoides under both phases was studied and the parameters were individually optimized. Under optimum operating conditions in GP (LI 6 klux, photoperiod 12 h:12 h, temperature 25°C, 6% concentration of CO2), the total nitrogen was completely consumed after 8 days of operation and highest LP of 64.7 mg/(L.day) was obtained. This value was further enhanced to 106.65 mg/(L.day) by operating the photobioreactor in NSP under its optimum conditions (LI of 4 klux, photoperiod of 16 h:8 h, temperature 25°C, pH 8, 4% concentration of CO2). Under optimum operating conditions, removal efficiency of total phosphorous and Chemical Oxygen Demand were 100 and 70.19%, respectively, and highest carbon fixation rate of 549.16 mg CO2/(L.day) was observed.