Long-term effect of aluminum oxide nanoparticles on activated sludge performance in sequencing batch reactors

Nanoparticles (NPs) have raised global concerns due to their extensive use and detrimental impacts on ecosystems. While wastewater treatment plants (WWTPs) are viewed as potential sources of nanocompounds in the environment, the influence of aluminum oxide nanoparticles (Al₂O₃NPs) on wastewater treatment remains uncertain. This study aimed to explore the long-term effects of wastewater-borne Al₂O₃NPs and their bulk counterparts on the effectiveness of pollutant removal within sequencing batch reactors (SBRs), activated sludge performance, internal biological activity/viability, and microbial community diversity and structure. The presence of Al₂O₃NPs was observed to induce alterations in the removal efficiency of COD, ${NH}_4^{+}-$ N, and SOP from wastewater, as well as impacting the nitrification process during prolonged exposure. Al₂O₃NPs in wastewater accumulated in the sludge, affecting its morphology and diminishing microbial viability and biological activity. Additionally, high throughput sequencing of 16S rRNA indicated that Al₂O₃NPs could impact on the microbial richness and diversity of activated sludge in the SBR. In contrast, wastewater containing bulk counterparts did not negatively influence the capacity of wastewater treatment plants. This research provides novel and crucial insights into the effects of Al₂O₃NPs on the biological wastewater treatment process, holding significance for risk assessment procedures.