Carbon-negative and high-rate nutrient removal using mixotrophic microalgae. (November 2021) - Mubashar, Muhammad
Graphical abstract: Highlights: Mixotrophy removed 53.18% and 37.98% more N than autotrophy and heterotrophy. N removal at balanced autotrophic/heterotrophic share of 6:4 was 2.03 mg L −1 h −1 . Glucose utilization increased from 63% to 98% due to internal recycling of CO2 . Abstract: Mixotrophic microalgae have demonstrated great potential for wastewater nutrient removal. How autotrophy/heterotrophy shares affect nutrient removal as well as carbon budget has not been understood. In this study, the autotrophy/heterotrophy shares in mixotrophy were quantified, and N removal rate and carbon budget under different mixotrophic autotrophy/heterotrophy shares were modeled. The results showed that mixotrophic N removal rate reached 2.09 mg L −1 h −1, which was 53.18% and 37.98% higher than removal rates in autotrophic (0.97 mg L −1 h −1 ) and heterotrophic (1.25 mg L −1 h −1 ) controls. Mixotrophic-autotrophy and mixotrophic-heterotrophy contributed 1.15 mg L −1 h −1 and 0.94 mg L −1 h −1 in N removal, respectively. Model disclosed that at balanced share of 6:4, more than 2 mg L −1 h −1 N removal could be achieved, similar to bacterial nitrogen removal rate but with a negative carbon budget of 6.21 mg L −1 h −1 . Nutrient removal using mixotrophic microalgae would lead to carbon negative sustainable wastewater treatment and resource recycling.