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

• Published in: Environmental science & technology Vol. 42; no. 15; pp. 5828 - 5833
• Main Authors: Limbach, Ludwig K, Bereiter, Robert, Müller, Elisabeth, Krebs, Rolf, Gälli, René, Stark, Wendelin J
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.08.2008
• Subjects: Adsorption; Applied sciences; Cerium - chemistry; Cerium - isolation & purification; Ecotoxicology and Human Environmental Health; Exact sciences and technology; Hydrogen-Ion Concentration; Investigations; Microscopy, Electron, Scanning; Models, Chemical; Nanoparticles; Nanoparticles - chemistry; Nanotechnology - methods; Oxides - chemistry; Oxides - isolation & purification; Oxygen; Pollution; Sewage - chemistry; Sludge; Solubility; Surface-Active Agents - chemistry; Surfactants; Time Factors; Toxicity; Waste Disposal, Fluid - methods; Water Pollutants, Chemical - chemistry; Water Pollutants, Chemical - isolation & purification; Water treatment; Water treatment plants; Surface charge; Pollutant behavior; Nanoparticle; Stabilization; Waste treatment; Ultrafine particle; Surfactant; Long term; Modeling; Sewage treatment plant; Waste water; Persistence; Adsorption; Industrial waste water; Model compound; Preparation; Aerosols; Bacteria; Air pollution
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es800091f

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.