Efficient treatment of mariculture wastewater in a bacteria-algal symbiotic moving bed biofilm reactor: Impact of aerobic/anoxic duration

The bacteria-algal symbiotic moving bed biofilm reactor (BAS-MBBR) could remove nitrogen and phosphorus efficiently, but its performance was limited by the aerobic/anoxic duration. Therefore, the impact of aerobic/anoxic duration on removal performance, enzyme activity and microbial structure was studied. The results showed high removal efficiencies of COD (86.15 %), NH₄⁺-N (86.11 %) and TP (87.95 %) under varying aerobic/anoxic durations. The optimal aerobic/anoxic duration of 150 min/170 min achieved the highest oxygen consumption, nitrogen transformation, phosphorus uptake, and enzymatic activity. However, a longer anoxic duration (90 min/230 min) increased extracellular polymer secretion, reactive oxygen species production, and lactate dehydrogenase release, indicating elevated biological toxicity. The increase in anoxic duration promoted the proliferation of Denitromonas and Muricauda in the bacterial community and affected the removal of nitrogen. Chloroplastida thrived under short anoxic durations in the algal community. SAR increased significantly, resulting in changes in algal community structure and pollutant removal efficiency.