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 (Al2O3 NPs) stress. Al2O3 NPs at 0-50 mg/L showed no evident impact on the COD and NH4 + removals of SBR. The oxygen-uptake rate, nitrifying rate and nitrite-reducing rate slightly diminished with the increase of Al2O3 NPs concentration. Compared with 0 mg/L Al2O3 NPs, the dehydrogenase activity declined by 23.52% at 50 mg/L Al2O3 NPs. The activities of ammonia monooxygenase, nitrite oxidoreductase and nitrite reductase decreased with the increase of Al2O3 NPs concentration from 0 to 50 mg/L Al2O3 NPs. However, the nitrate reductase (NR) activity slightly increased at 5 and 15 mg/L Al2O3 NPs and declined at 30 and 50 mg/L Al2O3 NPs. The microbial reactive oxygen species (ROS) production and lactate dehydrogenase (LDH) release merely raised 14.80% and 20.72% at 50 mg/L Al2O3 NPs by contrast with 0 mg/L Al2O3 NPs, respectively. Al2O3 NPs enhanced the production, protein content and polysaccharide content of extracellular polymeric substances owing to preventing the microbes from Al2O3 NPs biotoxicity. The existence of Al2O3 NPs led to the variations of microbial richness and diversity in the SBR due to their biotoxicity.

Impacts of silver nanoparticles on performance and microbial community and enzymatic activity of a sequencing batch reactor.

The performance, microbial community and enzymatic activity of a sequencing batch reactor (SBR) were evaluated under silver nanoparticles (Ag NPs) stress. Over 5 mg/L Ag NPs inhibited the COD and phosphorus removals, whereas the NH4+ removal kept stable during the whole operational period. The organic matter, nitrogen and phosphorus removal rates were obviously inhibited under Ag NPs stress, which showed similar varying trends with the corresponding microbial enzymatic activities. The change of Ag content in the activated sludge indicated that some Ag NPs were absorbed by the sludge. The presence of Ag NPs promoted the increase of reactive oxygen species (ROS) and lactate dehydrogenase (LDH) of microorganism due to the microbial response to the Ag NPs toxicity, which could impact on the microbial morphology and physiological functions. The presence of Ag NPs could produce some evident changes in the microbial community.