Photosynthetic Microorganisms Have Been Attracting World Attention for their Great Potential as Renewable Energy Sources in Recent Years. Cost Effective Production in Large Scale, However, remains a Major Challenge to overcome. It is Known to the Field that Turbulence Could Help Improving the Performance of Photobioreactors Due to the So-Called Flashing Light Effects. Better Understanding of the Multiphase Fluid Dynamics and the Irradiance Distribution Inside the Reactor that Cause the Flashing Light Effects, as Well as Quantifying their Impacts on the Reactor Performance, Thus, Are Crucial for Successful Design and Scale-Up of Photobioreactors. in This Study, a Species of Red Marine Microalgae, Porphyridium Sp., Was Grown in Three Airlift Column Photobioreactors (I.e., Draft Tube Column, Bubble Column, and Split Column). the Physical Properties of the Culture Medium, the Local Fluid Dynamics and the Photobioreactor Performances Were Investigated and Are Reported in This Part of the Manuscript. Results Indicate that the Presence of Microalgae Considerably Affected the Local Multiphase Flow Dynamics in the Studied Draft Tube Column. Results Also Show that the Split Column Reactor Works Slightly Better Than the Draft Tube and the Bubble Columns Due to the Spiral Flow Pattern Inside the Reactor. © 2011 Wiley Periodicals, Inc.