N-nitrosamines in electroplating and printing/dyeing industrial wastewater treatment plants: Removal efficiency, environmental emission, and the influence on drinking water

The discharge of industrial wastewater containing high concentrations of N -nitrosamines to the aquatic environment can impair downstream source waters and pose potential risks to human health. However, the transport and fate of N -nitrosamines in typical industrial wastewater treatment plants (IWWTPs) and the influence of these effluents on source water and drinking water are still unclear. This study investigated nine N -nitrosamines in four full-scale electroplating (E-) and printing/dyeing (PD-) IWWTPs, two drinking water treatment plants (DWTPs) in the lower reaches of these IWWTPs, and the corresponding tap water in South China. The total concentrations of N -nitrosamines ( & sum;NAs) were 382 - 10,600, 480 - 1920, 494 - 789, and 27.9 - 427 ng/L in influents, effluents, source water, and tap water, respectively. The compositions of N -nitrosamine species in different influents varied a lot, while N -nitrosodi-n-butylamine (NDBA) and N -nitrosodimethylamine (NDMA) dominated in most of the effluents, source water, and tap water. More than 70 % N -nitrosamines were removed by wastewater treatment processes used in E-IWWTPs such as ferric -carbon micro -electrolysis (Fe/C-ME), while only about 50 % of N - nitrosamines were removed in PD-IWWTPs due to the use of chlorine reagent or other inefficient conventional processes such as flocculation by cationic amine -based polymers or bio-contact oxidation. Therefore, the mass fluxes of N -nitrosamines discharged from these industrial wastewaters to the environment in the selected two industrial towns were up to 14,700 mg/day. The results based on correlation and principal component analysis significantly demonstrated correlations between E -and PD -effluents and source water and tap water, suggesting that these effluents can serve as sources of N -nitrosamines to local drinking water systems. This study suggests that N -nitrosamines are prevalent in typical IWWTPs, which may infect drinking water systems. The findings of this study provide a basis data for the scientific evaluation of environmental processes of N -nitrosamines.