Trophic mode conversion and nitrogen deprivation of microalgae for high ammonium removal from synthetic wastewater.

In this study, a well-controlled three-stage process was proposed for high ammonium removal from synthetic wastewater using selected promising microalgal strain UMN266. Three trophic modes (photoautotrophy, heterotrophy, and mixotrophy), two N sufficiency conditions (N sufficient and N deprived), two inoculum modes (photoautotrophic and heterotrophic), and different NH 4 + -N concentrations were compared to investigate the effect of trophic mode conversion and N deprivation on high NH 4 + -N removal by UMN266. Results showed that photoautotrophic inoculum with trophic mode conversion from heterotrophy to photoautotrophy and N deprivation in Stage 2 turned was the optimum plan for NH 4 + -N removal, and average removal rates were 12.4 and 19.1 mg/L/d with initial NH 4 + -N of 80 and 160 mg/L in Stage 3. Mechanism investigations based on algal biomass carbon (C) and N content, cellular composition, and starch content confirmed the above optimum plan and potential of UMN266 as bioethanol feedstock. [ABSTRACT FROM AUTHOR]