Elucidation of the stress mechanisms on activated sludge stability induced by yttrium oxide nanoparticles with cytotoxicity: Performance deterioration, biointerface variation and microbial response

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 (Y 2 O 3 ) NPs on the activated sludge stability. Y 2 O 3 NPs progressively suppressed nitrification, caused significant NO 2 − accumulation (200 mg/L) and diminished activities of key functional enzymes. Deteriorated flocculation corroborates the Y 2 O 3 NPs’ destruction. Extracellular polymeric substances were lessened, yet amplified microbial metabolites prove the microbial counteraction coping with Y 2 O 3 NPs’ cytotoxicity. Plausible blockage of different protein channels contributed to the wane in biological nitrogen-removal capacity. Plus, 50 mg/L Y 2 O 3 NPs stimulated the β -glucan production. When exceeding 100 mg/L, plentiful Y 2 O 3 NPs aggregate on sludge-surface, which inhibits nutrients transfer and metabolism. Furthermore, ammonia-oxidizing bacteria shifted from Nitrosomonas to Nitrosospira with Y 2 O 3 NPs increase. Reduction in Nitrospira , Saccharimonada- genera, and Microlunatus further corroborates the impairment of pollutants removal. PICRUSt2 prediction demonstrates Y 2 O 3 NPs impedes nitrogen and glycolytic metabolic pathway.