Cultivation of Mixed Microalgae Using Municipal Wastewater: Biomass Productivity, Nutrient Removal, and Biochemical Content

Background: Microalgal biotechnology has gained much attention previously. Monoculture algae cultivation has been carried out extensively in the last decades. However, although the mixed microalgae cultivation has some advantageous over pure cultures, there is still a lack of knowledge about the performance of mixed cultures. Objective: In this study, it has been tried to investigate all growth aspects of marine and freshwater microalgal species in a mixed culture and their biological effects on biomass growth and composition based on wastewater nutrient consumption. Material and Methods: Three algal species of Chlorella vulgaris, Scenedesmus obliquus, and Nannochloropsis sp. were cultivated in saline wastewater individually, then the effects of mixing the three strains on biomass productivity, nutrient removal efficiency, chlorophyll, carotenoid, and lipid content were investigated. Results: The obtained results revealed that the mixed culture of three strains showed the highest biomass productivity of 191 mg. L-1.d-1. Also, while there were no significant differences between the performance of mono and mixed culture of algal species in the removal efficiency of wastewater nutrients, the three-strain microalgal mixed culture showed the highest values of 3.5 mg.L-1.d-1 and 5.75 mg.L-1.d-1 in the removal rate of phosphate and nitrate, respectively. In terms of total chlorophyll and carotenoid per produced biomass, however, the mixed culture of three species showed the lowest values of 4.08 and 0.6 mg. g biomass-1, respectively. Conclusions: The finding proves the potential of attractive and economically feasible mixed microalgae cultivation for high percentage nutrient removal and microalgal biomass production.