Mixed Wastewater Coupled With CO₂ For Microalgae Culturing And Nutrient Removal

Biomass, nutrient removal capacity, lipid productivityand morphological changesof Chlorella sorokiniana and Desmodesmus communis were investigated in mixed wastewaters with different CO₂ concentrations. Under optimal condition, which was 1:3 ratio of swine wastewater to second treated municipal wastewater with 5% CO₂, the maximum biomass concentrations were 1.22 g L-1 and 0.84 g L-1 for C. sorokiniana and D. communis, respectively. Almost all of the ammonia and phosphorus were removed, the removal rates of total nitrogen were 88.05% for C. sorokiniana and 83.18% for D. communis. Lipid productivity reached 0.021 g L-1d-1 for C. sorokiniana and 0.017 g L-1d-1 for D. communis after 10 days culture. CO₂ aeration increased intracellular particle numbers of both microalgae and made D.communis tend to be solitary. The research suggested the aeration of CO₂ improve the tolerance of microalgae to high concentration of NH4+-N, and nutrient excess stress could induce lipid accumulation of microalgae. In addition,under different culture conditions, two microalgae strains also undergo corresponding changes.