Kinetics on the CO₂ fixation by batch culture for blue green algae

Abstract

Batch cultivation of blue green algae Spirulina platensis in the photobioreactor was carried out to evaluate the culture as CO₂ fixation system. The authors kinetically analyzed the effect of CO₂ and NH₃ concentration in the culture on CO₂ fixation and biomass productivity ofthe algae. The obtained results are summarized as follows;
1) The productivity of the algae was slightly increased, when the NaHCO₃ concentration was raised to between 32-64 (g/l) in comparison with ordinary cultivation (16g/l).
2) The growth of the algae was smooth on the culture when both NH₃ and NO₃ were used as the nitrogen source. In this case, the absorption rate of NH₃-N was about 20 (mg/(l·d)). When NH₃ was the only nitrogen source, the obtained maximum growth rate was 0.147 (g/(l·d)) at 20 (mg/l) of initial NH₃-N concentration, and productivity of the algae was reduced by about 1/2-1/3 of the ordinary cultivation. A 200 (mg/l) of the initial NH₃-N concentration damaged the growth of the biomass.
3) The C/N ratio, which obtained the maximum CO₂ fixation rate, ranged from 10 to 20 and the average volumetric mass transfer coefficient value, K^CO2La, was 0.005 (1/h).
For wastewater treatment using algae, the concentration and composition control of the influent nitrogen source will be one of the most important problems.