Abstract：To explore the impacts of carbon source supplementation on the purification efficiency of Pyropia-processing wastewater (PPW) by microalga, Scenedesmus obliquus was selected as the research object and sodium acetate as the supplementary carbon source. The growth performance of S. obliquus and the removal efficiency of pollutants in PPW were investigated under different sodium acetate concentrations (0, 0.25, 0.50, 0.75, 1.00, and 1.50 g/L). The results showed that the addition of exogenous sodium acetate led to an obvious increase in the initial concentration of chemical oxygen demand (COD) in PPW. However, S. obliquus was still effective in removing pollutants from PPW (P<0.05). After 5—7 d of culture, the maximal removal rate was shown to be 81.97% in COD, 88.41% in total nitrogen (TN), 94.10% in total phosphorus (TP), and 91.23% in phycobiliprotein (PP) from PPW by S. obliquus under different concentrations of sodium acetate. The addition of 80 mg/L chitosan to flocculate algal cells after culturing S. obliquus resulted in significant increase in the maximum COD elimination rate to 91.43% (P<0.05). The maximal biomass (0.81 g/L) and soluble sugar (168.61 mg/g) contents were observed in S. obliquus in the 1.50 g/L sodium acetate group for 7 days culture, 63.54% and 1.06 times higher than those in the control group (P<0.05). The findings suggest that under exogenous supplementation of 0.25—1.50 g/L sodium acetate conditions, S. obliquus cultivated in PPW can accumulate higher biomass and soluble sugar content, with effectively reducing the levels of pollutants in PPW simultaneously. In addition, the COD removal rate is found to be further improved by adding moderate chitosan for flocculation at the end of microalgae culture.
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