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Article

Removal of Oxide Nanoparticles in a Model Wastewater Treatment Plant: Influence of Agglomeration and Surfactants on Clearing Efficiency

Supporting Info

Ludwig K. Limbach^†, Robert Bereiter^‡^§, Elisabeth M

ller, Rolf Krebs^§, Ren

lli^‡ and Wendelin J. Stark*^†

Institute for Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, ETH Zurich, CH-8093 Zurich, Switzerland, BMG Engineering AG, Ifangstrasse 11, CH-8952 Schlieren, Switzerland, Zurich University of Applied Sciences, Schloss, CH-8820 W

denswil, Switzerland, and Electron Microscopy ETH Zurich (EMEZ), CH-8093 Zurich, Switzerland

Environ. Sci. Technol., 2008, 42 (15), pp 5828–5833

DOI: 10.1021/es800091f

Publication Date (Web): June 25, 2008

†

Institute for Chemical and Bioengineering.

‡

BMG Engineering AG.

Zurich University of Applied Sciences.

Electron Microscopy ETH Zurich.

* Corresponding author phone: +41 44 632 09 80; fax: +41 44 633 10 83; e-mail: wendelin.stark@chem.ethz.ch.

Abstract

The rapidly increasing production of engineered nanoparticles has created a demand for particle removal from industrial and communal wastewater streams. Efficient removal is particularly important in view of increasing long-term persistence and evidence for considerable ecotoxicity of specific nanoparticles. The present work investigates the use of a model wastewater treatment plant for removal of oxide nanoparticles. While a majority of the nanoparticles could be captured through adhesion to clearing sludge, a significant fraction of the engineered nanoparticles escaped the wastewater plant’s clearing system, and up to 6 wt % of the model compound cerium oxide was found in the exit stream of the model plant. Our study demonstrates a significant influence of surface charge and the addition of dispersion stabilizing surfactants as routinely used in the preparation of nanoparticle derived products. A detailed investigation on the agglomeration of oxide nanoparticles in wastewater streams revealed a high stabilization of the particles against clearance (adsorption on the bacteria from the sludge). This unexpected finding suggests a need to investigate nanoparticle clearance in more detail and demonstrates the complex interactions between dissolved species and the nanoparticles within the continuously changing environment of the clearing sludge.

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