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155628 
Journal Article 
Removal of oxide nanoparticles in a model wastewater treatment plant: Influence of agglomeration and surfactants on clearing efficiency 
Limbach, LK; Bereiter, R; Muller, E; Krebs, R; Galli, R; Stark, WJ 
2008 
1 
Environmental Science & Technology
ISSN: 0013-936X
EISSN: 1520-5851 
42 
15 
5828-5833 
WOS:000258075100071 
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 throughadhesionto clearing sludge,asignificant fraction
of the engineered nanoparticles escaped the wastewater
plant?s clearing system, and up to 6wt%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.