Abstract
This study aimed to reveal the potential of microalgae for purifying wastewater, reducing carbon dioxide (CO2) emissions, and simultaneously providing potential biofuel feedstock for energy security. Tetradesmus obliquus (T. obliquus) was cultured in municipal wastewater supplemented with different NH4Cl (0, 50, 100 mg L−1 NH4Cl) and CO2 concentrations (5%, 10% and 15% v/v). The results showed that municipal wastewater is appropriate for T. obliquus cultivation, achieving significant biomass (818.8–1577.6 mgdw·L−1). The diameter of T. obliquus cells at 5–15% v/v CO2 concentrations was approximately 2.9, 2.3, and 2.0 μm in the groups with 0, 50 and 100 mg L−1 NH4Cl respectively, which may be caused by the accumulation of biochemical components in T. obliquus cells. The computed maximum CO2 fixation rates of T. obliquus were 106.6–121.1, 171.1–224.3 and 229.8–275.1 mg CO2·L−1·d−1 in groups with 0, 50 and 100 NH4Cl mg·L−1 added, respectively. It suggested that adding N concentration could promote CO2 fixation by T. obliquus. T. obliquus demonstrated favourable removal efficiencies of nitrogen (76.99–100%), phosphorus (97.64–100%) and heavy metals (32.57–100%) from municipal wastewater, and the concentrations of all these pollutants decreased with time. Total fatty acids produced by T. obliquus cells (102, 812.8–134, 232.4 μg g−1) generally increased with increasing feeding CO2 dosage (5%–15% v/v). These results indicate that the content of total fatty acids increased with increasing CO2 dosage. The growth kinetic model of T. obliquus, depending on the phosphorus and nitrogen quota, described changes in the specific growth rate (μ) well with R2 = 0.944–0.995, and μmax (0.335–0.625 d−1) positively related to added NH4+-N concentrations.
Published Version
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