Fate of cerium dioxide (CeO _2) nanoparticles in municipal wastewater during activated sludge treatment

摘要

This study investigated the fate of nano-CeO _2 during municipal wastewater treatment using a laboratory-scale activated sludge (A/S) system fed with primarily-treated municipal wastewater and nano-CeO _2 (55.0mg Ce/L). Nano-CeO _2 was highly removed during A/S treatment (96.6% total Ce). Extensive removal of CeO _2 <200nm was also attained and the concentration escaping treatment was only 0.11mg Ce/L. Elimination occurred mainly by aggregation and settling of CeO _2 particles, promoted by circumneutral pH values and by nanoparticle interactions with organic and/or inorganic wastewater constituents. Biosorption also contributed to CeO _2 removal as shown by sludge analysis and batch adsorption studies. Batch bioassays demonstrated that nano-CeO _2 only exerted inhibition of O _2 uptake by A/S at concentrations exceeding those in the bioreactor feed (50% inhibition at 950mg CeO _2/L). These findings indicate that A/S treatment is expected to provide extensive removal of nano-CeO _2 in municipal wastewaters.