title: Assessment of the fate of silver nanoparticles in the A(2)O-MBR system.
abstract: In this study, we employed a bench scale A(2)O-MBR (anaerobic-anoxic-oxic membrane bioreactor) system to systematically investigate the behavior and distribution of silver nanoparticles (AgNPs) in the activated sludge. The results showed that AgNPs would aggregate and form Ag-sulfur complexes in the activated sludge, and the dissolved silver only reached 13.6 μg/L when AgNPs of 5mg/L was spiked into the A(2)O-MBR. The long-term mass balance analysis showed that most of the silver contents were accumulated in the bioreactor and wasted excess sludge. Only a small fraction (less than 0.5%) of silver could get across the hollow fiber membranes with 0.1 μm nominal pore size in the effluent. In addition, the comparison between total AgNP concentration in aerobic sludge supernatant and effluent suggested that the membrane modules played a role in controlling the discharge of AgNPs into the effluent, especially under a higher influent concentration of AgNPs. Our results also showed that the adsorbed AgNPs or silver complexes in activated sludge still could release dissolved silver at the ambient pH. Thus, since activated sludge could be a sink for AgNPs, the risks of AgNPs in wasted excess sludge during utilization and disposal should be further studied.
authors.affiliation: Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China.
authors.forename: Zhi-Hua
authors.initials: ZH
authors.lastname: Yuan
authors.affiliation: Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China.
authors.forename: Xiaoyong
authors.initials: X
authors.lastname: Yang
authors.affiliation: Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China.
authors.forename: Anyi
authors.initials: A
authors.lastname: Hu
authors.affiliation: Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China. Electronic address: ymzheng@iue.ac.cn.
authors.forename: Yu-Ming
authors.initials: YM
authors.lastname: Zheng
authors.affiliation: Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China; Graduate Institute of Environmental Engineering, National Taiwan University, Taipei 106, Taiwan. Electronic address: cpyu@ntu.edu.tw.
authors.forename: Chang-Ping
authors.initials: CP
authors.lastname: Yu
keywords: Aggregation; Biological wastewater treatment; MBR; Release; Removal; Silver nanoparticles