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J Hazard Mater. 2014 Jul 15;276:164-70. doi: 10.1016/j.jhazmat.2014.04.048. Epub 2014 Apr 28.

Inhibitory effects of ZnO nanoparticles on aerobic wastewater biofilms from oxygen concentration profiles determined by microelectrodes.

Author information

1
Key Laboratory of Integrated Regulation and Resources Development on Shallow Lakes, Ministry of Education, Hohai University, Nanjing 210098, People's Republic of China; College of Environment, Hohai University, Nanjing 210098, People's Republic of China.
2
Key Laboratory of Integrated Regulation and Resources Development on Shallow Lakes, Ministry of Education, Hohai University, Nanjing 210098, People's Republic of China; College of Environment, Hohai University, Nanjing 210098, People's Republic of China. Electronic address: mlz1988@126.com.
3
Key Laboratory of Integrated Regulation and Resources Development on Shallow Lakes, Ministry of Education, Hohai University, Nanjing 210098, People's Republic of China; College of Environment, Hohai University, Nanjing 210098, People's Republic of China. Electronic address: hhuhjy973@126.com.

Abstract

The presence of ZnO NPs in waste streams can negatively affect the efficiency of biological nutrient removal from wastewater. However, details of the toxic effects of ZnO NPs on microbial activities of wastewater biofilms have not yet been reported. In this study, the temporal and spatial inhibitory effects of ZnO NPs on the O2 respiration activities of aerobic wastewater biofilms were investigated using an O2 microelectrode. The resulting time-course microelectrode measurements demonstrated that ZnO NPs inhibited O2 respiration within 2h. The spatial distributions of net specific O2 respiration were determined in biofilms with and without treatment of 5 or 50mg/L ZnO NPs. The results showed that 50mg/L of nano-ZnO inhibited the microbial activities only in the outer layer (∼200μm) of the biofilms, and bacteria present in the deeper parts of the biofilms became even more active. Scanning electron microscopy (SEM) analysis showed that the ZnO NPs were adsorbed onto the biofilm, but these NPs had no adverse effects on the cell membrane integrity of the biofilms. It was found that the inhibition of O2 respiration induced by higher concentrations of ZnO NPs (50mg/L) was mainly due to the release of zinc ions by dissolution of the ZnO NPs.

KEYWORDS:

Biofilm; Inhibitory effect; Microelectrode; Oxygen respiration activities; ZnO NPs

PMID:
24880618
DOI:
10.1016/j.jhazmat.2014.04.048
[Indexed for MEDLINE]
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