The characteristic evolution and formation mechanism of hybrid microalgae biofilm and its application in mariculture wastewater treatment

Microalgae biofilm had important applications in both energy and environmental fields. However, the current research on the formation mechanism of microalgae biofilm was vague. And the treatment of mariculture wastewater by microalgae biofilm was rare. Herein, a kind of natural hybrid microalgae was applied in this study to investigate the mechanism of microalgae biofilm formation and the treatment of mariculture wastewater under different ammonia nitrogen loads (13 mg/L, 25 mg/L, 37 mg/L). The results indicated that filamentous algae were first to attach to the carrier and then formed a web-like structure. Later, more non-filamentous algae and bacteria involved in the formation of biofilm. Protein in extracellular polymeric substances (EPS) was the key substance for the initial colonization. The N[tbnd]N functional group, tryptophan, high molecular weight of EPS promoted microalgae biofilm formation. When the ammonia nitrogen concentration was 25 mg/L, the microalgae biofilm reached the maximum biomass (1.79 mg/cm²) and the highest nitrogen and phosphorus removal efficiency (98% of NH₄⁺-N, 84% of TN, 68% of PO₄^--P). The study provides a theoretical basis for understanding the mechanism of natural hybrid microalgae biofilm formation and its application for mariculture wastewater treatment.