Toxicity of carbon nanotubes to the activated sludge process - examination of extracellular polymeric substances

This thesis examines the effects of two types of single walled carbon nanotubes, namely, long single walled carbon nanotubes (LSWCNTs) and functionalized long single walled carbon nanotubes (FLSWCNTs) on the respiratory activity of the activated sludge microbial communities by a respiration inhibition test. The effectiveness of the extracellular polymeric substances (EPS) in protecting the microbial communities within the activated sludge against the CNTs was determined by using both sheared and unsheared activated sludge. The results showed that CNTs were more toxic under the sheared condition compared to the unsheared condition. LSWCNTS were more toxic towards sheared activated sludge compared to unsheared activated sludge. In case of FLSWCNTs similar inhibition was observed for sheared and unsheared activated sludge and FLSWCNTs were more toxic than LSWCNTs in unsheared activated sludge.