Developing Microporous Fibrous-Diaphragm Aerator to Decrease Bubble Generation Diameter for Improving Microalgal Growth with CO2 Fixation in a Raceway Pond.

A novel microporous fibrous-diaphragm aerator (FDA) was proposed to generate pressurized gas with check valve to penetrate through millions of micropores (6-126 mu m) of expanded fibrous diaphragm on internal support, thus decreasing bubble generation diameter and increasing bubble residence time for improving microalgal growth with CO2 fixation in a raceway pond. When installation angle of FDA internal support increased from 0 degrees to 45 degrees, bubble generation time and diameter first decreased (to valley bottoms of 4 ms and 0.45mm at 22 degrees) and then increased. Compared to traditional strip aerator, bubble generation time and diameter decreased by 50% and 60% through FDA with support installation angle of 22 degrees and average pore diameter of 28 mu m, while gas-solution mixing time decreased by 22% and mass transfer coefficient increased by 40%, leading to increased actual photochemical efficiency (by 80%) and increased biomass yield (by 38.5%) of Arthrospira cells with pure CO2 aeration through FDA.