Developing microporous fibrous-diaphragm aerator to decrease bubble generation diameter for improving microalgal growth with CO 2 fixation in a raceway pond.

•A fibrous-diaphragm aerator generates bubbles through pores of expanded diaphragm.•An installation angle of 22° resulted in the minimum bubble generation diameter.•Bubble generation diameter and time decreased by 60% and 50%.•Mixing time decreased by 22% and mass-transfer coefficient increased by 40%.•Microalgal biomass yield and photochemical efficiency increased by 38.5% and 80%.