Nitrogen transformation and bacterial community response in O₃-SBR process for treating nitrogen-containing...

Nitrogen heterocyclic antibiotics (NHAs) pollution poses a significant threat to aquatic ecosystems. Ozonation (O₃) pretreatment is beneficial for the removal of total nitrogen (TN) in antibiotics by facilitating subsequent biological treatment. However, nitrogen transformation and bacterial community responses when treating NHAs by O₃-coupled biological processes remain unclear. This study utilized an O₃-coupled sequencing batch reactor (O₃-SBR) to evaluate its treatment efficacy on three typical NHAs, namely fluconazole, sulfamethizole, and acyclovir, and explored nitrogen transformation and the effects of oxidation products (NHAs-OPs) on bacterial communities. The results showed that the O₃-SBR process was more effective for treating NHAs than using O₃ or SBR alone. O₃ pretreatment converted nitrogen in difficult-to-degrade NHAs into inorganic nitrogen and other organic nitrogen compounds, improving the biodegradability of NHAs. Subsequently, NHAs-OPs were used as the nitrogen/carbon source for SBR. Unlike the low TN removal rate of 14.4-23.4% observed when treating pure NHAs wastewater, the TN and total organic carbon removal rates of the SBR treating NHAs-OPs wastewater reached 62.4-85.2% and 65.2-86.4%, respectively. High-throughput sequencing analysis revealed that the enhanced efficacy of the SBR process may be attributed to the dominance of bacterial genera adapted to NHAs-OPs within the system. Additionally, the abundance of denitrification functions under NHAs-OPs stress was found to be higher than that of nitrification functions. These results provide new theoretical support for the treatment of antibiotic production wastewater.