Effects of CeO2 nanoparticles on biological nitrogen removal in a sequencing batch biofilm reactor and mechanism of toxicity

Bioresour Technol. 2015 Sep:191:73-8. doi: 10.1016/j.biortech.2015.04.123. Epub 2015 May 7.

Abstract

The effects of CeO2 nanoparticles (CeO2 NPs) exposure on biological nitrogen removal in a sequencing batch biofilm reactor (SBBR) were investigated. At low concentration (1 mg/L), no significant effect was observed on total nitrogen (TN) removal. However, at high concentrations (10 and 50 mg/L), the TN removal efficiency reduced from 74.09% to 64.26% and 55.17%, respectively. Scanning electron microscope imaging showed large amounts of CeO2 NPs adsorbed on the biofilm, which increased the production of reactive oxygen species. The exposure at only 50 mg/L CeO2 NPs measurably affected the lactate dehydrogenase release. Confocal laser scanning microscopy showed that high concentrations of CeO2 NPs reduced bacterial viability. Moreover, after a short-term exposure, extracellular polymeric substances (EPS) were observed to increase, forming a compact matrix to protect the bacteria. The activities of nitrate reductase and ammonia monooxygenase were inhibited, but there was no significant impact on the activity of nitrite oxidoreductase.

Keywords: Biofilms; CeO(2) NPs; Nitrogen removal; Sequencing batch biofilm reactor (SBBR); Toxicity mechanism.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adsorption / drug effects
  • Bacteria / metabolism
  • Biofilms / drug effects*
  • Bioreactors
  • Cerium / administration & dosage*
  • L-Lactate Dehydrogenase / metabolism
  • Nanoparticles / administration & dosage*
  • Nitrate Reductase / metabolism
  • Nitrogen / metabolism*
  • Oxidoreductases / metabolism
  • Reactive Oxygen Species / metabolism
  • Waste Disposal, Fluid / methods

Substances

  • Reactive Oxygen Species
  • Cerium
  • ceric oxide
  • Oxidoreductases
  • L-Lactate Dehydrogenase
  • ammonia monooxygenase
  • Nitrate Reductase
  • Nitrogen