Impacts of multiwalled carbon nanotubes on nutrient removal from wastewater and bacterial community structure in activated sludge

PLoS One. 2014 Sep 19;9(9):e107345. doi: 10.1371/journal.pone.0107345. eCollection 2014.

Abstract

Background: The increasing use of multiwalled carbon nanotubes (MWCNTs) will inevitably lead to the exposure of wastewater treatment facilities. However, knowledge of the impacts of MWCNTs on wastewater nutrient removal and bacterial community structure in the activated sludge process is sparse.

Aims: To investigate the effects of MWCNTs on wastewater nutrient removal, and bacterial community structure in activated sludge.

Methods: Three triplicate sequencing batch reactors (SBR) were exposed to wastewater which contained 0, 1, and 20 mg/L MWCNTs. MiSeq sequencing was used to investigate the bacterial community structures in activated sludge samples which were exposed to different concentrations of MWCNTs.

Results: Exposure to 1 and 20 mg/L MWCNTs had no acute (1 day) impact on nutrient removal from wastewater. After long-term (180 days) exposure to 1 mg/L MWCNTs, the average total nitrogen (TN) removal efficiency was not significantly affected. TN removal efficiency decreased from 84.0% to 71.9% after long-term effects of 20 mg/L MWCNTs. After long-term exposure to 1 and 20 mg/L MWCNTs, the total phosphorus removal efficiencies decreased from 96.8% to 52.3% and from 98.2% to 34.0% respectively. Further study revealed that long-term exposure to 20 mg/L MWCNTs inhibited activities of ammonia monooxygenase and nitrite oxidoreductase. Long-term exposure to 1 and 20 mg/L MWCNTs both inhibited activities of exopolyphosphatase and polyphosphate kinase. MiSeq sequencing data indicated that 20 mg/L MWCNTs significantly decreased the diversity of bacterial community in activated sludge. Long-term exposure to 1 and 20 mg/L MWCNTs differentially decreased the abundance of nitrifying bacteria, especially ammonia-oxidizing bacteria. The abundance of PAOs was decreased after long-term exposure to 20 mg/L MWCNTs. The abundance of glycogen accumulating organisms (GAOs) was increased after long-term exposure to 1 mg/L MWCNTs.

Conclusion: MWCNTs have adverse effects on biological wastewater nutrient removal, and altered the diversity and structure of bacterial community in activated sludge.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bioreactors
  • Nanotubes, Carbon / chemistry*
  • Nitrogen / analysis
  • Nitrogen / chemistry
  • Phosphorus / analysis
  • Phosphorus / chemistry
  • Phylogeny
  • Proteobacteria / classification
  • Proteobacteria / physiology
  • Sewage / microbiology*
  • Wastewater / chemistry*
  • Wastewater / microbiology
  • Water Purification / methods*

Substances

  • Nanotubes, Carbon
  • Sewage
  • Waste Water
  • Phosphorus
  • Nitrogen

Grants and funding

This study was supported by the International Science-Technology Cooperation Program of China (2013DFR60250), the Fundamental Research Funds for the Central Universities (ZY1306) and special fund of State Key Joint Laboratory of Environment Simulation and Pollution Control (3K06ESPCT). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.