Changcheng Pu is a second year PhD student of Civil & Environmental Engineering department at Syracuse University, working in the Environmental Organic Chemistry Laboratory with Dr. Teng Zeng. He received his Bachelor’s degree from Tsinghua University and Master’s degree from Stanford University. His research focuses on understanding the transport and fate of organic contaminants in natural and engineered aquatic systems, by combining analytical instrumentation with field-based research. He is currently working on a project to identify N-Nitrosamines and their precursors in urban water systems. The long-term goal of his research is to promote the control of contaminants in the aquatic environment.
Occurrence, Fate and Composition of Total N-Nitrosamines and Their Precursors in Wastewater
N-Nitrosamines are a group of emerging contaminants of public health concern. The current focus on N-nitrosamines in drinking water systems has forced the impression that N-nitrosamines are disinfection byproducts. However, other upstream processes, especially wastewater treatment plants (WWTPs), may serve as direct sources of N-nitrosamines. Numerous studies have documented the fate of known N-nitrosamines (e.g., N-nitrosodimethylamine) at conventional and advanced WWTPs, but these species only represent a small fraction of the total N-nitrosamine (TONO) pool. To advance our understanding of the unknown fraction of TONO, we combine chemiluminescence detection and high-resolution mass spectrometry (HRMS) to characterize the occurrence, fate and composition of wastewater-derived TONO and their precursors. We applied a previously developed chemiluminescence method to study the variation of TONO concentrations across the treatment train at six municipal WWTPs in New York. N-nitrosamine precursors are quantified through chloramination formation potential test. Preliminary results showed that aerobic biological treatment (e.g., activated sludge or aerated filters) resulted in elevated TONO levels to varying degrees, which likely serves as a net source of TONO and their precursors. To further determine the composition of TONO, we established an N-nitroso compound database containing 2839 unique molecular formulas compiled from PubChem. Comparing HRMS experimental data of samples from three WWTPs and the database revealed a total of 460 aligned chemical features potentially containing the N-nitroso substructure. These features are further prioritized based on occurrence frequency and peak area change after chloramination. According to predicted compound structures, some of the features are possibly derived from N-nitrosation of pharmaceuticals in wastewater.