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

Abstract

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%.