Nutrients recycle and the growth of Scenedesmus obliquus in synthetic wastewater under different sodium carbonate concentrations

This study illustrated the growth of Scenedesmus obliquus and recycle of nutrients in wastewater combined with inorganic carbon under autotrophic conditions. Scenedesmus obliquus was cultivated under different conditions by adding sodium carbonate (Na(2)CO(3)) at 15–40 mg l(−1) separately in wastewater containing high nitrogen and phosphorus content. The growth characteristics of S. obliquus, pH and dissolved inorganic carbon (DIC) changes of microalgae liquid, the recycle rate of ammonia and phosphorus and lipid content were determined. The changes of pH and DIC showed that S. obliquus could use Na(2)CO(3) to grow, with lipid contents of 18–25%. Among all Na(2)CO(3) concentrations, 20 mg l(−1) was the optimum, of which S. obliquus had the highest NH(3)-N recycle of 52% and [Formula: see text] recycle of 67%. By the 14th day, its biomass production also reaches the maximum of 0.21 g l(−1). However, inorganic carbon fixation rate was inversely proportional to its concentration. Moreover, the biomass was in positive correlation with the Na(2)CO(3) concentration except 20 mg l(−1), which provided a possibility that S. obliquus could be acclimatized to adjust to high concentrations of inorganic carbon to promote biomass accumulation and recycle of nutrients.