An assessment of the autotrophic/heterotrophic synergism in microalgae under mixotrophic mode and its contribution in high-rate phosphate recovery from wastewater

Dual carbon metabolisms and the synergism contribute to improving nutrient recovery under mixotrophy. However, how synergism influences nutrient recovery has yet to be understood, which is revealed in the current study. Due to dual carbon metabolisms and synergism, the PO₄⁻-P recovery rate under mixotrophy reached 0.34 mg L⁻¹ h⁻¹. Due to the internal cycling of respiratory CO₂, the mutualistic index (MI) in terms of synergism helped Scenedesmus accumulate 27.49 % more biomass under mixotrophy than sum of the two controls. In contrast, MI contributed 0.26 g L⁻¹ d⁻¹ to the total modeled mixotrophic productivity of 1.15 g L⁻¹ d⁻¹. To total modeled PO₄⁻-P recovery, mixotrophic-auto, and mixotrophic-hetero shares were 42 % and 58 %. The synergism under mixotrophy contributed 20 % in total PO₄⁻-P recovery. The PO₄⁻-P recovery rate under mixotrophy was comparable to other biological P removal methods. These findings emphasize the potential of synergism in improving productivity and promoting resource recovery for sustainable wastewater treatment.