The interactions of algae-bacteria symbiotic system and its effects on nutrients removal from synthetic wastewater

- sCOD, TDN and TDP removals by the algae-bacteria symbiotic system were obtained.
- The appropriate ratio for Chlorella vulgaris and Bacillus licheniformis was 1:3.
- The concentrations of AIP and c-di-GMP as quorum sensing substances were tested.

The ability of Chlorella vulgaris-Bacillus licheniformis and Microcystis aeruginosa-Bacillus licheniformis consortiums to eliminate total dissolved nitrogen (TDN), total dissolved phosphorus (TDP), and soluble chemical oxygen demand (sCOD) from synthetic wastewater was studied. The highest values of dry cell weight, chlorophyll-a, and chlorophyll metabolism related genes/bacterial rRNA gene copies were obtained in the Chlorella vulgaris-Bacillus licheniformis system at Chlorella vulgaris and Bacillus licheniformis ratio of 1:3. On the 10th day, the Chlorella vulgaris-Bacillus licheniformis system at this ratio removed 86.55%, 80.28% and 88.95% of sCOD, TDP and TDN, respectively. But, the Microcystis aeruginosa-Bacillus licheniformis system at this ratio only removed 65.62%, 70.82%, and 21.56% of sCOD, TDP and TDN, respectively. Chlorella vulgaris and Bacillus licheniformis could coexist as an algae-bacteria consortia and quorum sensing substances (autoinducing peptides and bis (3′-5′) diguanylic acid) concentrations were measured. Finally, the interactions and communication patterns between Chlorella vulgaris and Bacillus licheniformis were depicted.