N-Nitrosamines and their precursors in wastewater effluents from selected industries in Spain

COVID-19 impacts on characterization of N-nitrosamines and their precursors during transport in sewer systems

During the COVID-19 outbreak, N-nitrosodimethylamine (NDMA) and N-nitrosomorpholine (NMOR) and their specific precursors (N,N-dimethylformamide [DMF] for NDMA and morpholine [MOR] for NMOR) were widely detected in sewerage systems of an urban area, in which chlorine-containing disinfectants were discharged with effluent of hospitals, etc. However, little is known about the effect of chlorine influx on formation and distribution of NDMA and NMOR in sewer systems in a sudden major public health event. We investigated the spatiotemporal patterns of NDMA, NMOR, DMF and MOR in influents of sewage treatment plants (STPs), as well as its upstream sewer sites during the COVID-19 pandemic. During the pandemic, there was a significant decrease of industry-related NMOR and DMF, however, with an increase of concentration (up to 243 ng/L) and detection frequency for NDMA in influents of the biggest STP in Kyoto Prefecture. Moreover, it was found that NDMA reached a maximum of 187 ng/L with 57 % detection frequency, while NMOR reached a maximum of 101 ng/L with 51 % detection frequency in the sewer systems connecting to all the STPs for service area during the pandemic. Especially, during the pandemic, concentration (median value) of NDMA increased from 40.9 ng/L with 42 % detection frequency in 2020 to 72.5 ng/L with 77 % detection frequency in 2021, which was coincident with the change of infected population. In addition, this research clearly exhibited the possibility that unintentional chlorination and nitrosation of precursors formed NDMA and NMOR in sewer systems influenced by COVID-19 pandemic. The NDMA formation was ranked according to increased concentration (median value) as follows: addition of ClO- (669 ng/L) > addition of NO2- (138 ng/L) > without addition (34.3 ng/L), while additional ClO- and NO2- did not significantly increase NMOR formation probably caused by low existence of NMOR precursors (e.g., MOR) in raw sewage. Therefore, it is necessary to make an urgent attention on environmental issues caused by high-dose chlorine-containing disinfectants residue, because increased byproducts induced by disinfectants in raw sewage caused higher risk during the future pandemic by unexpected pollution from insufficiently treated sewage (e.g. combined sewer overflow and primary effluent bypass discharge) to receiving water bodies.

Microcontaminants and microplastics in water from the textile sector: a review and a database of physicochemical properties, use in the textile process, and ecotoxicity data for detected chemicals

Microcontaminants (MCs) and microplastics (MPs) originating from the textile sector are today receiving a great deal of attention due to potential environmental concerns. Environmental pressures and impacts related to the textile system include not only the use of resources (e.g., water) but also the release of a wide variety of pollutants. This review's main objective is to highlight the presence of textile MCs and MPs in water, in their full path from textile factories (from raw materials to the final product) to wastewater treatment plants (WWTPs), and finally to the receiving surface waters. Their environmental fate and ecotoxicity were also addressed. Overall, more than 500 compounds were found, many of which are so called "contaminants of environmental concern" such as per- and polyfluoroalkyl substances (PFAS) and alkylphenol compounds. A database of physicochemical properties, ecotoxicity, and place of detection (specific textile process, WWTP, surface water or sediment) (classification by several international agencies) was compiled for the chemical detected. Preliminary risk assessment was conducted for those MCs for which the reported environmental concentrations exceeded the Predicted No Effect Concentration (PNEC). These chemicals were some nonylphenols, nonylphenol ethoxylates and organophosphate esters. Among MPs, polyester and nylon fibres were the most abundant. The highest concentration of MPs was reported in sludge (about 1.4 × 106 MPs per kg) compared to wastewater and surface water which showed MP concentrations at least two orders of magnitude lower. The role of transboundary contamination due to the release of chemicals from imported textile products was also assessed.

Maximizing N-Nitrosamine Rejection via RO Membrane Plugging with Hexylamine and Hexamethylenediamine

The rapid expansion of urban areas and the increasing demand for water resources necessitate substantial investments in technologies that enable the reuse of municipal wastewater for various purposes. Nonetheless, numerous challenges remain, particularly regarding disinfection by-products (DBPs), especially carcinogenic compounds such as N-nitrosamines (NTRs). To tackle the ongoing issues associated with reverse osmosis (RO) membranes, this study investigated the rejection of NTRs across a range of commercially available RO membranes. In addition, the research aimed to improve rejection rates by integrating molecular plugs into the nanopores of the polyamide (PA) layer. Hexylamine (HEX) and hexamethylenediamine (HDMA), both linear chain amines, have proven to be effective as molecular plugs for enhancing the removal of NTRs. Given the environmental and human health concerns associated with linear amines, the study also aimed to assess the feasibility of diamine molecules as potential alternatives. The application of molecular plugs led to changes in pore size distribution (PSD) and effective pore number, resulting in a decrease in membrane permeability (from 5 to 33%), while maintaining levels suitable for RO processes. HEX and HDMA exhibited a positive effect on NTR rejection with ACM1, ACM5 and BW30LE membranes. In particular, NDMA rejection, the smallest molecule of the tested NTRs, with ACM1 was improved by 65.5% and 70.6% after treatment with HEX and HDMA, respectively.

Research progress on the generation of NDMA by typical PPCPs in disinfection treatment of water environment in China: A review

The drugs and personal care products in water sources are potential threats to the ecological environment and drinking water quality. In recent years, the presence of PPCPs has been detected in multiple drinking water sources in China. PPCPs are usually stable and resistant to degradation in aquatic environments. During chlorination, chloramination, and ozonation disinfection processes, PPCPs can act as precursor substances to generate N-nitrosodimethylamine (NDMA) which is the most widely detected nitrosamine byproduct in drinking water. This review provides a comprehensive overview of the impact of PPCPs in China's water environment on the generation of NDMA during disinfection processes to better understand the correlation between PPCPs and NDMA generation. Chloramine is the most likely to form NDMA with different disinfection methods, so chloramine disinfection may be the main pathway for NDMA generation. Activated carbon adsorption and UV photolysis are widely used in the removal of NDMA and its precursor PPCPs, and biological treatment is found to be a low-cost and high removal rate method for controlling the generation of NDMA. However, there are still certain regional limitations in the investigation and research on PPCPs, and other nitrosamine by-products such as NMEA, NDEA and NDBA should also be studied to investigate the formation mechanism and removal methods.

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 (∑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.

Feasibility of NDEA formation control from DEDTC in chlorination/chloramination by pre-ozonation: Mechanisms and influencing factors

N-nitrosodiethylamine (NDEA), which is the most toxic nitrosamine among the 9 detected species, has been widely detected in drinking water. Amines containing diethylamine (DEA) groups in the structure would generate NDEA during the disinfection processes. The aim of this study was to evaluate the feasibility of reducing NDEA formation from a commonly used dithiocarbamate pesticide sodium diethyldithiocarbamate (DEDTC) in subsequent chlorination and chloramination by pre-ozonation. The results demonstrated that NDEA could be generated directly during ozonation, its amounts increased from 0 to 14.34 μg/L with increasing ozone dosages (0-4 mg/L), which was higher than that chlorination (2.68 μg/L) and chloramination (4.91 μg/L) when the initial concentration of DEDTC was 20 μM. Pre-ozonation significantly raised NDEA formation from 2.68 to15.32 μg/L in subsequent chlorination; and that from 4.91 to 9.54 μg/L during subsequent chloramination processes. The addition of •OH scavenger tert-butanol (tBA) increased the production of NDEA from 8.14 to 20.80 μg/L during ozonation, and that from 6.76 to17.98 μg/L in O3/HClO process, 8.74 to 17.33 μg/L in O3/NH2Cl process. Except for NO3- and CO32-, most of the co-existing substances promoted NDEA generation from DEDTC under disinfection conditions. Based on the results of Gaussian theory calculations, GC/MS and UPLC-Q-TOFMS analysis, the influencing mechanisms of pre-ozonation on NDEA generation in the subsequent disinfection process were proposed. In addition, not only acute/chronic toxicity calculation but also luminescent bacteria test was performed to assess the possibility of pre-ozonation on the risk control of DEDTC. The research results fill a gap in the control of NDEA pollution and help to develop a safer ozone oxidation technology.

Spatiotemporal Variability in N-Nitrosodimethylamine Precursor Levels in a Watershed Impacted by Agricultural Activities and Municipal Wastewater Discharges and Effects of Lime Softening

The Crow River, a tributary of the Mississippi River in Minnesota, U.S.A., that is impacted by agricultural activities and municipal wastewater discharges, was sampled approximately monthly at 12 locations over 18 months to investigate temporal and spatial variations in N-nitrosodimethylamine (NDMA) precursor levels. NDMA precursors were quantified primarily by measuring NDMA formed under the low chloramine dose uniform formation conditions protocol (NDMAUFC) and occasionally using the high dose formation potential protocol (NDMAFP). Raw water NDMAUFC concentrations (2.2 to 128 ng/L) exhibited substantial temporal variation but relatively little spatial variation. An increase in NDMAUFC was observed for 126 of 169 water samples after lime-softening treatment. A kinetic model indicates that under chloramine-limited UFC test conditions, the increase in NDMAUFC can be attributed to a decrease in competition between precursors and natural organic matter (NOM) for chloramines and reduced interactions of precursors with NOM. NDMAUFC concentrations correlated positively with dissolved nitrogen concentration (ρ = 0.44, p < 0.01) when excluding the spring snowmelt period and negatively correlated with dissolved organic carbon concentration (ρ = -0.47, p < 0.01). Overall, NDMA precursor levels were highly dynamic and strongly affected by lime-softening treatment.

Impact of Polymer Chain Rearrangements in the PA Structure of RO Membranes on Water Permeability and N-Nitrosamine Rejection

The use of solvents is overall recognized as an efficient method to improve the water permeability of polyamide thin film composite membranes (PA-TFC). The objective of this work was to test the performance of the membranes after exposing them to n-propanol (n-PrOH) to improve the permeability of the membranes while maintaining the rejection factor for small uncharged organic molecules, namely N-nitrosamines (NTRs). After the membranes were exposed to n-PrOH, the water permeability of the UTC73AC membrane increased by 98%, with minimal change in rejection. N-nitrosodiethylamine (NDEA) rejection decreased (3.4%), while N-nitrosodi-n-propylamine (NDPA) and N-nitrosodi-n-butylamine (NDBA) rejection increased by 0.9% and 2.8%, respectively. In contrast, for the BW30LE membrane, water permeability decreased (by 38.7%), while rejection factors increased by 14.5% for NDEA, 6.2% for NDPA, and 15.0% for NDBA. In addition, the morphology of the membrane surface before and after exposure to n-PrOH was analyzed. This result and the pore size distribution (PSD) curves obtained indicate that the rearrangement of polymer chains affects the network or aggregate pores in the PA layer, implying that a change in pore size or a change in pore size distribution could improve the permeability of water molecules, while the rejection factor for NTRs is not significantly affected.