Toxicity of Aqueous Fullerene nC60 to Activated Sludge: Nitrification Inhibition and Microtox Test

The increasing production and use of fullerene nanomaterials raised their exposure potential to the activated sludge during biological wastewater treatment process. In this study, the toxicity of aqueous nanoscaled C-60 (nC(60)) to activated sludge was investigated using nitrification inhibition and Microtox test. The test solutions of nC(60) were prepared using two methods: long stirring (Stir/nC(60)) and toluene exchange (Tol/nC(60)). The nC(60) aggregation in test medium was also evaluated for toxicity assessment. The results showed that the nC(60) aggregation behaved differently in two test mediums during the incubation periods. The nC(60) toxicity was greatly influenced by the preparation method. Stir/nC(60) presented no significant toxicity to both the nitrification sludge and bioluminescent bacteria at the maximum concentration studied. In contrast, the EC20 of Tol/nC(60) was obtained to be 4.89 mg/L (3 h) for the nitrification inhibition and 3.44 mg/L (30 min) for Microtox test, respectively.