Interaction of Chlorella vulgaris and bacteria when co-cultivated in anaerobically digested swine manure

Mono-culture and co-culture of algae (Chlorella vulgaris) and bacteria (activated sludge) on anaerobically digested swine manure (ADSM) were investigated in this research. The results showed that during the co-cultivation biomass growth was promoted (2.43 ± 0.11 g/L) compared with the algae-only culture (1.09 ± 0.03 g/L), and the aerobic bacteria growth was initially promoted, then inhibited. The SEM (Scanning Electron Microscope) observation indicated that the amount of the C. vulgaris increased while bacteria ‘disappeared’ over time. After 30 min settlement, 95.5% of the biomass in co-cultivation group precipitated, while only 40.4% of the biomass settled for the algae-only group was. It is believed that the presence of bacteria enhanced the settling rate through the formation of algal consortium flocs. Bacterial community diversity and composition were measured and the results indicated that the bacterial diversity dropped and the bacterial active classes changed in the co-cultivation group.