Effect of Fe 3 O 4 nanoparticles exposure on the treatment efficiency of phenol wastewater and community shifts in SBR system

Increasing magnetic Fe O nanoparticles (Fe O 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 Fe O NPs, while were inhibited at 800 mg/L Fe O NPs, correspondingly affected phenol degradation efficiency. Lactic dehydrogenase (LDH) increased when Fe O NPs exceeded 600 mg/L, indicated the more severe cell rupture at high Fe O NPs concentration. At the same Fe O 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 Fe O NPs, while increased when Fe O NPs exceeded 600 mg/L, which was in accordance with EPS content. Biopolymer-degrading and phenol-degrading genera increased at 0-600 mg/L Fe O NPs, while decreased at Fe O NPs exceeded 600 mg/L, which conformed to EPS content and phenol degradation efficiency.