Microporous Diaphragm Aerator Improves Flue Gas CO2 Dissolution and Photosynthetic Characteristics of Arthrospira Cells in 660 m2 Raceway Ponds

Abstract

The flue gas CO₂ from coal chemical plants can be purified and then absorbed by microalgae to produce high valued products and achieve CO₂ emission reduction. The dissolution of CO₂ from coal chemical flue gas was strengthened using microporous diaphragm aerators (MDA) to promote the HCO₃– concentration for improving photosynthetic characteristics of Arthrospira cells in 660 m² raceway ponds with 2.5–10 vol % CO₂ gas. An increase in the quantum yield of the photosynthetic electron transfer of Arthrospira cells promoted biomass growth by 15.5% in the MDA-equipped raceway pond. The specific energy fluxes of light absorption (ABS/RC) and electron transport (ET₀/RC) in Arthrospira cells at 23 h first increased to peaks of 3113 and 757, respectively, when the CO₂ concentration increased from 0.04% (air) to 7.5 vol %, and then both values decreased when the CO₂ concentration further increased to 10 vol %. Accordingly, the photosystem II (PSII) reaction center quantity and the driving force per excited cross-section reached peaks of 628 and 2.72, respectively, at 7.5 vol % CO₂. Therefore, the Arthrospira carotenoid yield increased by 25% and peaked when the CO₂ concentration increased from 0.04% (air) to 7.5 vol %. This could provide guidance for engineering demonstration of large-scale microalgae cultivation.