The compound Bacillus and sea purslane (Sesuvium portulacastrum) enhanced aquaculture wastewater treatment efficiency: Insights from a study on microbial community distributions

As the aquaculture industry continues to grow rapidly, the environmental consequences of wastewater discharge from aquaculture have become a major concern. The biological treatment method has proven to be an effective and beneficial approach for wastewater treatment. In this experiment, aquaculture wastewater was treated using two different ratios of Bacillus subtilis and Bacillus licheniformis composites in combination with sea purslane (Sesuvium portulacastrum) to investigate the wastewater treatment efficiency and microbial community. Sea purslane effectively removed nutrients from aquaculture wastewater. The addition of compound Bacillus significantly increased the removal rates of COD_Mn, TP, and PO₄³⁻-P, which were 54.9–56.4 %, 78.2–79.9 %, and 85.0–89.6 %, respectively. Moreover, the compound Bacillus notably influenced the microbial community composition in the water and root systems, reducing species abundance while increasing community diversity, with Treatment 2 exhibiting the highest community stability. The addition of the compound Bacillus significantly increased the relative abundance of Alphaproteobacteria. Most of the important operational taxonomic units (OTUs) that significantly impacted the groups belonged to Alphaproteobacteria. Different biomarkers in the water and root system were primarily from Alphaproteobacteria, Gammaproteobacteria, and Bacteroidia, including Idiomarina and Alteromonas, Ruegeria, Vibrio, Algoriphagus, and Maribacter, among others. These microorganisms play a significant role in promoting the removal rate of nitrogen and phosphorus. Furthermore, the compound Bacillus notably affected the abundance of nitrogen cycle-related sequences and increased the relative abundance of microorganisms associated with the nitrogen cycle. These findings provide valuable insights for optimizing aquaculture wastewater treatment processes.