Looking for engineered nanoparticles (ENPs) in wastewater treatment systems: Qualification and quantification aspects.

The current study developed a rationalized method for the quantification and identification of engineered nanoparticles (ENPs) in wastewaters. A review of current literature revealed that overall, presently available methods focused on single ENP mostly and were applicable mainly to samples of low organic loadings or under well-controlled laboratory conditions. In the present research, procedures including dialysis for desalting and low-temperature oxidation for organic removal were used to pretreat samples of high organic loadings, specifically, municipal wastewater and sludge. SEM mapping technique identified the presence of nanoparticles, which was followed by ICP-OES quantification of different engineering nanoparticles in wastewater and sludge samples collected from two major regional municipal wastewater treatment plants. Results showed successful identification and quantification of nano-size titanium and zinc oxides from wastewater treatment plants studied. Concentration profile was mapped out for the wastewater treatment plants (WWTPs) using the method developed in this research. Results also showed an overall 80% and 68% removal of titanium and zinc by primary and secondary sludge particulates, respectively. Mass flux of engineered nanoparticles (ENPs) was also calculated to estimate the daily flow of engineered nanoparticles in the system.