Modeling of carbon dioxide mass transfer behavior in attached cultivation photobioreactor using the analysis of the pH profiles.

The CO2 mass transfer model associated with growth kinetics of microalgal biofilm in attached cultivation photobioreactor was developed and verified by using the analysis of pH profiles which were in equilibrium with inorganic carbon components concentrations (CO2, H2CO3, HCO3- and CO32-) in medium. Model simulation results showed that the model well presented the biofilm growth process. The overall volumetric mass transfer coefficient of CO2 was more influenced by CO2 concentration in aerated gas but less by gas aeration rate and medium circulation rate. Other bio-kinetic parameters related with the microalgal biofilm such as CO2 diffusion coefficient in biofilm, Monod maximum utilization rate of CO2, lag phase duration of biofilm and half-saturation CO2 concentration in the biofilm were independent on operational conditions. The pH profiles provided a way to monitor the variations of inorganic carbon concentrations of medium and to regulate the cultivation of attached microalgal biofilm by CO2 supplement.