Effect of salinity on a Chlorella salina-Mercenaria mercenaria consortium in the treatment of aquacultural wastewater

Sammendrag

Mariculture wastewater contains elevated levels of nitrogen and phosphorus nutrients. Microalgal technology shows potential for treating these wastewaters. However, its widespread application is limited by challenges associated with microalgae collection. In this study, the effects of salinity on a Chlorella salina-Mercenaria mercenaria consortium and the purification capacity of the consortium for aquacultural wastewater were evaluated. The microalgae–shellfish consortium has demonstrated excellent removal capabilities for both Chlorella salina and nutrient salts. At 26 ppt, the microalgae–shellfish consortium showed better removal rates than at 16 ppt, with total nitrogen (76.33 % and 62.22 %), total phosphorus (96.82 % and 96.67 %), and Chlorella salina (74.22 % and 37.01 %) removal rates, respectively. Filter-feeding by Mercenaria mercenaria significantly reduced microbial community diversity in the water. The highest abundance of NS3a_marine_group was seen in the Chlorella phase, and the highest abundance of Alternaria alternata was seen in the clam-feeding phase. The better removal rate of dissolved organic nitrogen at 26 ppt may have been due to the higher abundance of Alteromonas. The microalgae–shellfish consortium showed a low removal rate of Chlorella salina (37.01 %) at low salinity. Increasing the number of shellfish in the microalgae–shellfish consortium may help enhance the algal removal rate at lower salinities. For optimal treatment of aquaculture wastewater, Chlorella salina should first be added and allowed to act alone for 48 to 72 h, followed by the addition of Mercenaria mercenaria for 36 to 42 h. The findings of this study provided references for the treatment of mariculture wastewater and the sustainable development of aquaculture.