Optimization of cultivation conditions for combined nutrient removal and CO 2 fixation in a batch photobioreactor

BACKGROUND The application of Chlorella vulgaris for simultaneous CO 2 biofixation and nutrient removal has been optimised using response surface methodology ( RSM ) based on Box Behnken design ( BBD ). Experimental conditions employed comprised CO 2 concentrations ( C c,g ) of 0.03–22% CO 2 , irradiation intensities ( I ) of 100–400 μE , temperatures of 20–30 °C and nutrient concentrations of 0–56 and 0–19 mg L −1 nitrogen and phosphorus, respectively, the response parameters being specific growth rate μ , CO 2 uptake rate R c and %nutrient removal. RESULTS Over 10 days the biomass concentration reached almost 3 g L −1 for C c,g of 5% CO 2 , with corresponding values of 0.74 g L −1 day −1 and 1.17 day −1 for R c and μ , respectively, and 100% nutrient (N and P) removals. At 22% CO 2 the R c and μ decreased by around an order of magnitude, and nutrient removal also decreased to 79% and 50% for N and P, respectively. CONCLUSION Optimum values 5% CO 2 , 100 μE and 22 °C were identified for C c,g , I and T , respectively, with μ and R c reaching 1.53 day −1 and 1 g L −1 day −1 , respectively, along with associated nutrient removal of 100%. Regression analysis indicated a good fit between experimental and model data. © 2016 Society of Chemical Industry