LAUSR

Abstract This paper investigates the impact of nano-TiO 2 and fullerene (C 60 ) on the activity of micro-organisms present in wastewater treatment works (WWTWs). Results showed that low concentration levels of nano-TiO 2 (10 μg L −1 ) and fullerene (1 μg L −1 ) has little effect on both gas production and the microorganisms’ morphology. However higher concentrations of nano-TiO 2 (100 and 1000 μg L −1 ) and fullerene (10 and 100 μg L −1 ) reduced or stopped completely gas production. SEM micrographs showed that addition of nanoparticles reduced the microorganisms count up to 30 min of exposure, followed by an increase of selected micro-organisms after a 360 min exposure to TiO 2 and Fullerene. Overall, this study demonstrates that engineered nanoparticle concentration levels and exposure time play an important role in the toxicity of microbial communities present in WWTWs. It also shows that under stressed conditions, the micro-organisms appear to protect themselves via a spore forming mechanism that allows them to survive the environment.