Co-cultivation of fungal-microalgal strains in biogas slurry and biogas purification under different initial CO 2 concentrations.

The effects of five different microalgae-fungi on nutrient removal and CO ₂ removal were investigated under three different CO ₂ contents (35%, 45% and 55%). The results showed that the highest nutrient and CO ₂ removal efficiency were found at 55% CO ₂ by cocultivation of different microalgae and fungi. The effect of different initial CO ₂ concentration on the removal of CO ₂ from microalgae was significant, and the order of CO ₂ removal efficiency was 55% (v/v) >45% (v/v) >35% (v/v). The best nutrient removal and biogas purification could be achieved by co-cultivation of C. vulgaris and G. lucidum with 55% initial CO ₂ content. The maximum mean COD, TN, TP and CO ₂ removal efficiency can reach 68.29%, 61.75%, 64.21% and 64.68%, respectively under this condition. All highest COD, TN, TP and CO ₂ removal efficiency were more than 85%. The analysis of energy consumption economic efficiency revealed that this strategy resulted in the highest economic efficiency. The results of this work can promote simultaneously biological purification of wastewater and biogas using microalgal-fungal symbiosis.