Characterization of bubble column photobioreactors for shear-sensitive microalgae culture

Area of Science:

• Marine biology
• Biochemical engineering
• Fluid dynamics

Background:

• Karlodinium veneficum is a shear-sensitive marine dinoflagellate.
• Bubble column photobioreactors are used for microalgal cultivation.
• Understanding hydrodynamics is crucial for optimizing photobioreactor performance.

Purpose of the Study:

• To investigate the effect of hydrodynamics on Karlodinium veneficum growth in a bubble column photobioreactor.
• To characterize energy dissipation rates and their impact on CO2 transfer.
• To determine optimal operating conditions for K. veneficum cultivation.

Main Methods:

• Cultivation of K. veneficum in a cylindrical bubble column photobioreactor.
• Varying liquid height, superficial gas velocity, and nozzle diameter.
• Utilizing computational fluid dynamics (CFD) to analyze flow hydrodynamics and energy dissipation.
• Measuring gas holdup and volumetric mass transfer coefficient.

Main Results:

• Gas holdup and volumetric mass transfer coefficient were dependent on liquid height and correlated with the Froude number.
• Energy dissipation rates varied significantly within the reactor: ED_spar > ED_top > ED_whole.
• CO2 transfer limited K. veneficum growth at low energy dissipation rates (ED_whole).
• High energy dissipation rates (above a critical ED_whole) caused severe stress to the cultures.

Conclusions:

• Hydrodynamic conditions significantly influence CO2 transfer and K. veneficum growth.
• Optimal photobioreactor design and operation require careful management of energy dissipation.
• Further research is needed to define the critical energy dissipation threshold for K. veneficum stress.