Elucidation of the stress mechanisms on activated sludge stability induced by yttrium oxide nanoparticles with...

As technoscience advances, widespread use of nanoparticles (NPs) has resulted in environmental risks. This study focuses on the potential stress of 0-200 mg/L yttrium oxide (Y₂O₃) NPs on the activated sludge stability. Y₂O₃ NPs progressively suppressed nitrification, caused significant NO₂^- accumulation (200 mg/L) and diminished activities of key functional enzymes. Deteriorated flocculation corroborates the Y₂O₃ NPs' destruction. Extracellular polymeric substances were lessened, yet amplified microbial metabolites prove the microbial counteraction coping with Y₂O₃ NPs' cytotoxicity. Plausible blockage of different protein channels contributed to the wane in biological nitrogen-removal capacity. Plus, 50 mg/L Y₂O₃ NPs stimulated the β-glucan production. When exceeding 100 mg/L, plentiful Y₂O₃ NPs aggregate on sludge-surface, which inhibits nutrients transfer and metabolism. Furthermore, ammonia-oxidizing bacteria shifted from Nitrosomonas to Nitrosospira with Y₂O₃ NPs increase. Reduction in Nitrospira, Saccharimonada-genera, and Microlunatus further corroborates the impairment of pollutants removal. PICRUSt2 prediction demonstrates Y₂O₃ NPs impedes nitrogen and glycolytic metabolic pathway.