Effects of aluminum oxide nanoparticles on the performance, extracellular polymeric substances, microbial community and enzymatic activity of sequencing batch reactor.

The performance, pollutant removal rate, microbial community and enzymatic activity of a sequencing batch reactor (SBR) were investigated under oxide nanoparticles (AlO NPs) stress. AlO NPs at 0-50 mg/L showed no evident impact on the COD and NH removals of SBR. The oxygen-uptake rate, nitrifying rate and nitrite-reducing rate slightly diminished with the increase of AlO NPs concentration. Compared with 0 mg/L AlO NPs, the dehydrogenase activity declined by 23.52% at 50 mg/L AlO NPs. The activities of ammonia monooxygenase, nitrite oxidoreductase and nitrite reductase decreased with the increase of AlO NPs concentration from 0 to 50 mg/L AlO NPs. However, the nitrate reductase (NR) activity slightly increased at 5 and 15 mg/L AlO NPs and declined at 30 and 50 mg/L AlO NPs. The microbial reactive oxygen species (ROS) production and lactate dehydrogenase (LDH) release merely raised 14.80% and 20.72% at 50 mg/L AlO NPs by contrast with 0 mg/L AlO NPs, respectively. AlO NPs enhanced the production, protein content and polysaccharide content of extracellular polymeric substances owing to preventing the microbes from AlO NPs biotoxicity. The existence of AlO NPs led to the variations of microbial richness and diversity in the SBR due to their biotoxicity.