[Effects of Magnetic FeO Nanoparticles on the Characteristics of Anaerobic Granular Sludge and Its Interior Microbial Community].

In this study, the effects of magnetic FeO nanoparticles (FeO NPs) on soluble microbial products (SMP), loosely bound extracellular polymeric substances (LB-EPS), and tightly bound extracellular polymeric substances (TB-EPS) in anaerobic granular sludge were examined. In addition, the anaerobic granular sludge interior microbial community dynamics were investigated using high-throughput sequencing. The results demonstrated that the removal rate of COD was 83.6% after long-term exposure in the experimental reactor, namely, the anaerobic reactor containing FeO NPs. It was reduced by 5.7% in comparison with the removal rate in the control reactor. The total amount of TB-EPS in anaerobic granular sludge in the experimental and control reactors was 178.20 mg·g and 138.24 mg·g, respectively, while the total amount of SMP in anaerobic granular sludge was 34.88 mg·L and 27.44 mg·L, respectively. With regard to the LB-EPS in anaerobic granular sludge in the experimental reactor, the peak of humic acid disappeared and the peak intensity of coenzyme F decreased slightly using excitation-emission matrix (EEM) fluorescence spectra. In terms of the microbial community dynamics in the experimental reactor, the abundance of was greatly augmented from 76.15% to 86.76%; whereas, the abundance of decreased from 17.1% to 7.51%. This indicated that was more sensitive to FeO NPs. Moreover, the changes in bacterial communities were evident:①the abundance of Proteobacteria dropped from 66.44% to 47.16%; ② the abundance of Actinobacteria grew from 8.97% to 17.33%; and ③ the abundance of Bacteroidetes increased from 8.07% to 17.74%. The increasing abundance of Actinobacteria and Bacteroidetes plays a positive role in the anaerobic hydrolysis of organic matter.