Evaluation of Oscillatory Flow Conditions for Microalgal CO₂ Capture and Biomass Sedimentation Kinetics: Experimental...

This study evaluates the oscillatory frequency and amplitude in an oscillatory flow reactor with smooth periodic constrictions (OFR-SPC) for the cultivation and harvesting of Chlorella vulgaris fed with an air stream with 5% (v/v) CO₂. Their effect on biomass productivity, CO₂ capture, nutrient removal, and sedimentation kinetics was assessed. Cultures were tested at frequencies of 0.5-2.5 Hz and amplitudes of 6-18 mm. At 2.5 Hz|6 mm, the system achieved the maximum biomass concentration (592 mg_DW L^-1), productivity (5.36 mg_DW L^-1 h^-1), and CO₂ fixation (8.34 mg L^-1 h^-1) as well as complete nitrogen removal and near-complete phosphorus removal (100% and 91%, respectively). Complete sedimentation occurred at 0.5 Hz|6 mm, with kinetics described by the Gompertz model (k = 4.60 h^-1), confirming the feasibility of low-cost biomass recovery. Additionally, zeta potential positively influenced sedimentation but negatively affected productivity. Statistical analyses confirmed oscillation frequency and amplitude as key factors, establishing the OFR-SPC as a promising technology for microalgae-based efficient CO₂ capture, nutrient removal, and low-cost biomass harvesting.