Butterfly Baffle-Enhanced Solution Mixing and Mass Transfer for Improved Microalgal Growth in Double-Column Photobioreactor

High microalgal growth rates depend on appropriate solution mixing, and therefore, mass transfer can be achieved by installing baffle structures into photobioreactor (PBR) systems. In this study, butterfly-shaped baffles were installed in a double-column photobioreactor (DC-PBR) to decrease the mixing time, increase the mass transfer coefficient, and promote the growth rate of Arthrospira platensis. The mixing time was reduced by 20%, increasing the baffle size and the angle between wings, resulting in the mass transfer coefficient being simultaneously enhanced by 32%. The vertical flow vortices generated by the butterfly baffles strengthened the light/dark cycle between the inner and outer columns in DC-PBRs, which improved the chlorophyll-a content by 19%, photochemical efficiency and electron transfer rate by 20% during photosynthesis. The biomass growth rate of A. platensis was increased by 33% with the addition of a butterfly baffle to the PBR, while the helix pitch and trichome length were enlarged by 15–16%.