Developing microporous fibrous-diaphragm aerator to decrease bubble generation diameter for improving microalgal growth with CO2 fixation in a raceway pond

Abstract

A novel microporous fibrous-diaphragm aerator (FDA) was proposed to generate pressurized gas with check valve to penetrate through millions of micropores (6-126 μm) 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° to 45°, bubble generation time and diameter first decreased (to valley bottoms of 4 ms and 0.45 mm at 22°) 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° and average pore diameter of 28 µm, 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.

Keywords: Bubble generation; Fibrous-diaphragm aerator; Mass transfer; Microalgae biomass; Micropores.