Heterotrophic and mixotrophic cultivation of microalgae to simultaneously achieve furfural wastewater treatment and lipid production

[Display omitted] •It’s vital for algae growth and pollutants removal to add low nitrogen in wastewater.•Pollutants remove in wastewater varies in effect from heterotrophy to mixotrophy.•Nitrogen in wastewater for heterotrophy or mixotrophy affects lipid accumulation. Furfural wastewater (FWW) treatment is important in modern chemical production. However, traditional wastewater treatment methods are inappropriate for the treatment of FWW. In this work, Chlorella pyrenoidosa was employed to study the growth and pollutants removal with both heterotrophic and mixotrophic cultures. The results show that the biomass and removal efficiency for COD and TN were the highest under 10-fold dilution. However, TP removal were inconsistent when the algae were cultivated in both mixotrophic and heterotrophic modes. Compared to high nitrogen (0.75 g/L NaNO3), the algal cells grew faster when adding 0.25 g/L NaNO3 to the FWW, whether in mixotrophic or heterotrophic conditions. The total lipid content in heterotrophic conditions was 18.53%, which was higher than the values in mixotrophy when the concentration of NaNO3 was 0.75 g/L. Different carbon assimilation mechanisms of the algal cells result in a discrepancy in cell growth and pollutant removal, under different culture modes.