Promotion of Microalgal Growth, CO2 Fixation, and Pollutant Removal in Piggery Effluent by a Column Photobioreactor with Funnel-Shaped Spoilers

To enhance contact time between microalgae and nutrients in reactors, thereby improving the growth rate of microalgae and increasing pollutant removal efficiency, two funnel-shaped spoilers were added inside a traditional column photobioreactor. Compared to conventional column photobioreactors, the addition of these spoilers resulted in increased updraft, which improved horizontal flow. This change led to a greater shear force near the spoilers and a reduction in bubble diameter. As a result, the mass transfer coefficient and gas content increased by 12.17% and 7.71%, respectively, while the mixing time decreased by 30.57%. These improvements resulted in an 18.18% increase in microalgal biomass, a 13.95% increase in the CO2 fixation rate, and increases of 4.48%, 7.5%, and 4.7% in the removal of COD, TP, and NH4+-N, respectively, in the column photobioreactor with funnel-shaped spoilers. This was achieved when CO2 was introduced at a concentration of 10%, compared to a conventional column photobioreactor. This innovative design enhances the growth efficiency of microalgae, offering a new solution for reducing carbon emissions, promoting recycling of water resources, and advancing sustainable development.