Towards advanced mariculture wastewater treatment by bacterial-algal symbiosis system with different bacteria and algae inoculation ratios

In this study, we investigated the effect of different inoculation ratios of the suspended state bacterial-algal symbiosis system (BASS) on the treatment of pollutants in mariculture wastewater. The inoculation ratio of 3 (sludge/algae = 360 mg/L:120 mg/L) performed best, resulting in removal efficiencies of 96.22 %, 92.43 %, 94.56 %, and 95.06 % for COD, nitrogen, phosphorus, and sulfamethoxazole (SMX), respectively. An appropriate inoculation ratio (sludge/algae = 3) would increase not only the activity of algae and bacteria (12.86 μMol O2/mg·Chl-a·h for SOGR and 28.17 mgO2/g·MLVSS·h for SOUR) but also facilitate the secretion of extracellular polymers and the formation of bacterial-algal colloids, achieving simultaneous nitrification-denitrification. High-throughput sequencing results showed that the functional bacteria could constitute a complete aerobic-anoxic-anaerobic environmental gradient to achieve maximum oxygen utilization, and a higher abundance of sulfamethoxazole-degrading bacteria norak_f_Microscillaceae could be cultivated by changing the inoculum ratio. Therefore, this study provides new ideas for the treatment of mariculture wastewater containing antibiotics and the green development of the mariculture industry.