Efficient treatment of actual biogas slurry by Chlorella sorokiniana: Nutrient recovery and biomass production

Abstract

Microalgae have received widespread attention for their effectiveness in treating highly concentrated organic wastewater, not only for the effective removal of pollutants, but also for the preparation of biofuels and high-value products. This study investigated that the efficient purification process and mechanism of Chlorella sorokiniana on actual biogas slurry, including nutrient removal and biomass production. The results showed the C. sorokiniana grew well with a biomass of 742.35 ± 1.72 mg/L at pH 9, an inoculum concentration of 60 mg/L and 24 h of continuous light for 12 days. The recirculating experiments showed that after three incubations of the biogas slurry, the removal efficiency of COD, TN, NH4+-N, TP and PO43−-P were 89.11 %, 89.30 %, 97.26 %, 95.39 % and 96.43 %, respectively, and the total biomass of microalgae was 1015.87 mg/L. The contents of lipids, proteins, carbohydrates and photosynthetic pigments in C. sorokiniana cultured in biogas slurry were 26.36 %, 31.34 %, 30.26 % and 16.31 mg/L, respectively. It was increased by 6.21 %, 7.24 %, 2.74 % and 12.82 mg/L compared to the control, respectively. SEM results showed that the surface of C. sorokiniana mosaic with a large number of bacteria, and the cultivation of C. sorokiniana promoted the relative abundance for Proteobacteria, Cyanobacteria and Bacteroidota. Cultivation of C. sorokiniana in the actual biogas slurry constituted a good algae-bacterial symbiosis system, which effectively promoted the process of wastewater purification. This study provided an applied reference for the efficient treatment of actual wastewater by microalgae and its potential for resources utilization.