Optimization of cultivation conditions for combined nutrient removal and CO2 fixation in a batch photobioreactor
2017
Al Ketife, Ahmed MD | Judd, Simon | Znad, Hussein
BACKGROUND: The application of Chlorella vulgaris for simultaneous CO₂ biofixation and nutrient removal has been optimised using response surface methodology (RSM) based on Box Behnken design (BBD). Experimental conditions employed comprised CO₂ concentrations (Cc,g) of 0.03–22% CO₂, 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, CO₂ uptake rate Rc and %nutrient removal. RESULTS: Over 10 days the biomass concentration reached almost 3 g L⁻¹ for Cc,g of 5% CO₂, with corresponding values of 0.74 g L⁻¹ day⁻¹ and 1.17 day⁻¹ for Rc and μ, respectively, and 100% nutrient (N and P) removals. At 22% CO₂ the Rc 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% CO₂, 100 μE and 22 °C were identified for Cc,g, I and T, respectively, with μ and Rc 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
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