Effect of Fe3O4 nanoparticles exposure on the treatment efficiency of phenol wastewater and community shifts in SBR system

Abstract

Increasing magnetic Fe3O4 nanoparticles (Fe3O4 NPs) application has aroused concern about its potential environmental toxicity. During acute and chronic exposure, key enzymes involved in phenol biodegradation were promoted at 0–600 mg/L Fe3O4 NPs, while were inhibited at 800 mg/L Fe3O4 NPs, correspondingly affected phenol degradation efficiency. Lactic dehydrogenase (LDH) increased when Fe3O4 NPs exceeded 600 mg/L, indicated the more severe cell rupture at high Fe3O4 NPs concentration. At the same Fe3O4 NPs concentration, the removal of EPS further inhibited key enzymes, decreased phenol degradation, and increased LDH, indicating that the existence of EPS relieved the adverse effects on microorganisms. Spectroscopic analysis showed that protein and polysaccharide associated bonds in EPS decreased at 0–600 mg/L Fe3O4 NPs, while increased when Fe3O4 NPs exceeded 600 mg/L, which was in accordance with EPS content. Biopolymer-degrading and phenol-degrading genera increased at 0–600 mg/L Fe3O4 NPs, while decreased at Fe3O4 NPs exceeded 600 mg/L, which conformed to EPS content and phenol degradation efficiency.