title: Response to shock load of engineered nanoparticles in an activated sludge treatment system: Insight into microbial community succession.
abstract: The environmental impacts of the use of engineered nanoparticles (NPs) remain unclear and have attracted increasing concern worldwide. Considering that NPs eventually end up in wastewater treatment systems, the potential impact of ZnO and TiO2 NPs on the activated sludge was investigated using laboratory-scale sequencing batch reactors (SBRs). Short-term (24 h) exposure to 1, 10 and 100 mg/L shock loads of NPs reduced the oxygen uptake rate of the activated sludge by 3.55%-12.51% compared with the controls. In our experiment, the toxicities of TiO2 NPs were higher than those of ZnO NPs as reflected in the inhibition of oxygen utilization in the activated sludge. However, both the short-term (24 h) and long-term (21 days) exposure to ZnO and TiO2 NPs did not adversely affect the pollutant removal of the SBRs. Furthermore, the polymerase chain reaction-denaturing gel gradient electrophoresis revealed that the microbial community did not significantly vary after the short-term exposure (24 h) to 1, 10 and 100 mg/L shock loads of NPs; however, the cluster analysis in our experiment revealed that the slight difference caused by the NPs largely depended on exposure time rather than on NP type and NP concentration. The long-term exposure (13 days) to 10 mg/L shock load of ZnO or TiO2 NPs caused no substantial microbial community shifts in the activated sludge. The microbial diversity also showed no significant change when exposed to NPs as revealed by the Shannon-Wiener index.
authors.affiliation: State Key Laboratory of Simulation and Regulation of River Basin Water Cycle, China Institute of Water Resources and Hydropower Research, A-1 Fuxing Road Haidian District, Beijing 100038, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.affiliation: State Key Joint Laboratory of ESPC, School of Environment, Tsinghua University, Beijing 10084, China.
authors.forename: Qian
authors.initials: Q
authors.lastname: Dong
authors.affiliation: State Key Joint Laboratory of ESPC, School of Environment, Tsinghua University, Beijing 10084, China.
authors.forename: Yanchen
authors.initials: Y
authors.lastname: Liu
authors.affiliation: State Key Joint Laboratory of ESPC, School of Environment, Tsinghua University, Beijing 10084, China. Electronic address: xhzhou@mail.tsinghua.edu.cn.
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Zhou
authors.affiliation: State Key Joint Laboratory of ESPC, School of Environment, Tsinghua University, Beijing 10084, China.
authors.forename: Hanchang
authors.initials: H
authors.lastname: Shi
mesh_terms: D001419:Bacteria / Q000145:classification / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D019149:Bioreactors / Q000382:microbiology*; D058645:Denaturing Gradient Gel Electrophoresis; D053758:Nanoparticles / Q000633:toxicity*; D010100:Oxygen / Q000378:metabolism; D016133:Polymerase Chain Reaction; D012722:Sewage / Q000382:microbiology*; D014025:Titanium / Q000633:toxicity*; D014865:Waste Disposal, Fluid; D014874:Water Pollutants, Chemical / Q000633:toxicity*; D015034:Zinc Oxide / Q000633:toxicity*
chemical_list: D012722:Sewage; D014874:Water Pollutants, Chemical; C009495:titanium dioxide; D014025:Titanium; D010100:Oxygen; D015034:Zinc Oxide
keywords: Activated sludge; Denaturing gel gradient electrophoresis (DGGE); Engineered nanoparticles; Microbial community structure; Oxygen uptake rate