Toxicity of Long Single-Walled Carbon Nanotubes to the Activated Sludge Process: Examination of the Effects of Extracellular Polymeric Substances

In this paper, we examined the effect of extracellular polymeric substances (EPS) in protecting the microbial communities when the activated sludge was dosed with long single-walled carbon nanotubes (LSWCNTs). Mix-cultured activated sludge from a local wastewater treatment plant was used in the study and a respiratory inhibition test was performed on the activated sludge without shearing and after shearing to determine the respiratory activity of the activated sludge when the LSWCNTs were introduced. The results showed that the LSWCNTs exhibited toxicity towards the activated sludge microbial communities and more respiratory inhibition was observed when the EPS of the activated sludge was sheared off, illustrating the protective ability of EPS.