N-nitrosodimethylamine Formation Potentials Research Articles

Role of ranitidine in N-nitrosodimethylamine formation during chloramination of competing micropollutants

Ranitidine (RNT) is a widely known precursor of N-nitrosodimethylamine (NDMA) as evinced by the self-catalytic formation of NDMA during chloramination. In the present study, the NDMA formation potentials (NDMA-FP) of 26 micropollutants were assessed, particularly when mixed with RNT. 11 compounds were identified as individual precursors, including trimebutine and cimetidine, which exhibited substantial NDMA-FP, with up to 10% molar yield. In addition, nitrosamines, other than NDMA, namely N-nitrosodiethylamine and N-nitrosomethylamine, were observed from diethylamine-containing precursors, such as metoclopramide. In a 1:1 mixture of RNT and a competitor, the change in NDMA-FP was mostly comparable (within 20% deviation), while antagonistic interactions were observed for competitors, such as diethylhydroxylamine. The scattered overall NDMA-FP should be considered as a product of competition among the precursors for core substrates and intermediates for NDMA formation. The co-existence of either trimebutine or metoclopramide with RNT led to an exceptionally synergetic NDMA generation. Degradation kinetics and chlorination/nitrosation experiments combined with mass spectroscopy analyses indicated that RNT would accelerate both the initial chlorination and nitrosation of trimebutine and metoclopramide, leading to N-nitroso complexes, which have well-understood NDMA formation pathways, i.e., amination with subsequent aminyl radical generation. This work demonstrates a wide array of precursors with NDMA-FP, suggesting that nitrosamine formation is potentially underestimated in field environments.

Impact of biological wastewater treatment on the reactivity of N-Nitrosodimethylamine precursors

N-Nitrosodimethylamine (NDMA) is a probable human carcinogen which forms during chloramination of wastewater-impacted drinking waters. Municipal wastewater effluents are considered as major sources of NDMA precursors affecting downstream water quality. To evaluate the deactivation mechanisms and efficiencies of NDMA precursors during secondary treatment with the activated sludge (AS) process, NDMA formation potentials (FPs) of selected model precursor compounds and sewage components (i.e., blackwaters and greywaters) were monitored in batch AS treatment tests. After 24-h incubation with four different types of AS (i.e., domestic rural, domestic urban, textile and lab-grown AS), NDMA FP of trimethylamine (TMA) and minocycline (MNCL) decreased by 77-100%, while there was only 29-46% reduction in NDMA FP of sumatriptan (SMTR). The reduction in NDMA FP associated with ranitidine (RNTD) varied between 34% and 87%. The decrease in NDMA FP of RNTD depended on the AS type, hydraulic retention time (HRT) and solids retention time (SRT). The domestic AS (rural and urban) achieved higher decreases in NDMA FPs of the tested model precursors than the textile AS or lab-grown AS. Increasing the HRT or SRT enhanced NDMA FP decrease for RNTD. Among different processes tested (i.e., biodegradation, biosorption and volatilization), biosorption was the major mechanism responsible for the NDMA FP decrease of RNTD, MNCL and SMTR, while biodegradation was the major NDMA FP reduction mechanism for TMA. The reduction in NDMA FP of RNTD via biodegradation depended on the AS activity which may vary with sampling seasons and SRT. NDMA FPs in all tested sewage components (i.e., blackwaters and greywaters) decreased after 24-h AS treatment. Urine in blackwater was the predominant (i.e., >90%) contributor to NDMA FP in domestic sewage and AS-treated effluents.

Formation of N-nitrosodimethylamine by chloramination of anthropogenic nitrogenous compounds with dimethylamine monitored by Japanese water authorities.

Pollutant release and transfer registers (PRTRs) compounds accidentally released to source waters can be important precursors of the carcinogenic N-nitrosodimethylamine (NDMA) during drinking water treatment. The NDMA formation potentials (NDMAFPs) of 31 anthropogenic nitrogenous compounds with dimethylamine (DMA) moiety on the Japanese PRTR and the registered precursors listed by the Ministry of Health, Labour and Welfare of Japan are investigated as well as influencing factors (i.e., NH2Cl dose and water matrices) on the NDMAFPs of precursors. Tertiary amines with aryl groups β-positioned to the nitrogen atom of the DMA moiety formed high concentrations of NDMA (35-51%) during chloramination. Moreover, dimethylcarbamoyl chloride (DMCCl) was considered a new NDMA precursor with NDMAFP of 1.1%, higher than DMA, a traditional NDMA precursor. Excessive NH2Cl dose enhanced the NDMA formation, and the NDMAFP of DMCCl significantly decreased in river water; the effect of the matrix in river water varied and was compound-specific. Among the selected nitrogenous compounds, NDMAFPs of 15 excessed the current guideline concentration for NDMA in Japan (100 ng/L) assuming an accidental release of 0.144 mg C/L (the concentration in previous Japanese water quality accident in May 2012), and 2-(dimethylaminomethyl) thiophene (DMAMT) showed the highest NDMAFP at 58 μg/L.

Removal of N-nitrosodimethylamine precursors by cation exchange resin: The effects of pH and calcium

Cation exchange resins have proved to be efficient in removing precursors of N-nitrosodimethylamine (NDMA). NDMA is a probable human carcinogen with a calculated lifetime cancer risk of 10−6 at 0.7 ng/L in drinking water. This paper investigated the effect of pH and calcium levels on the removal of NDMA precursors using a cation exchange resin. At pH 5 and 7, 30–50% of NDMA precursors, measured by formation potentials (FPs) changes before and after the treatment, were removed by Plus resin. However, increases in NDMA FPs were observed after the treatment at pH 10 indicating that NDMA precursors were released from the resin. NDMA FPs removals in samples containing 15 and 115 mg/L Ca2+ were 40% and −10% after the ion exchange treatments at pH 7, respectively. It was found that in the presence of high concentration of calcium only one out of four cation exchange resins released NDMA precursors (probably due to manufacturing impurities). Also, the release of NDMA precursors depended on the calcium concentration and the contact time of the resin with the solution containing calcium. Nonetheless, NDMA precursors release from the resin subsided significantly with increasing the number of regeneration cycles of the resin.

Characterization of seven psychoactive pharmaceuticals as N‐nitrosodimethylamine precursors during free chlorine and chlorine dioxide chlorination processes

AbstractBACKGROUNDPsychoactive pharmaceuticals used to treat neurological disorders are of great concern because of their frequent detection in the aquatic environment and drinking water. The possibility for concurrent formation of N‐nitrosodimethylamine (NDMA) from psychoactive pharmaceuticals during disinfection is still not well‐studied. In the present study, seven widely used psychoactive drugs were selected due to their possession of a DMA functional group. The NDMA formation potentials of the selected drugs were assessed during free chlorine (NaOCl) and chlorine dioxide (ClO2) disinfection processes. The influence of several parameters (i.e. disinfectant dose, pH and water matrix) was investigated to better understand the reaction between the drugs and disinfectants that cause the formation of NDMA.RESULTSThe NDMA molar yields of seven pharmaceuticals were higher than 2%. NDMA formation was independent of the pH value, and more NDMA formation was observed during free chlorine chlorination. NDMA generation was enhanced when the selected pharmaceuticals were present in real water matrices, especially in secondary effluent.CONCLUSIONThis study demonstrated that the seven selected psychoactive pharmaceuticals containing dimethylamine groups can serve as NDMA precursors during free chlorine and chlorine dioxide chlorination processes. ClO2 was a proper disinfectant for controlling NDMA formation during chlorination. © 2018 Society of Chemical Industry

Deactivation of wastewater-derived N-nitrosodimethylamine precursors with chlorine dioxide oxidation and the effect of pH

In this study, the effect of chlorine dioxide (ClO2) oxidation on the deactivation of wastewater (WW)-derived N-nitrosodimethylamine (NDMA) precursors was investigated under various conditions (i.e., ClO2 application pH, dose and contact time). At pH 6.0, decreases in NDMA formation potentials (FPs) or occurrences (under uniform formation conditions [UFC]) were relatively low (<25%) with ClO2 oxidation regardless of WW-impact. A negative removal was also observed after ClO2 oxidation in some of the non-impacted waters. However, NDMA FP removals were significant (up to ~85%) under the same oxidation conditions in WW-impacted waters at pH 7.8. This indicates that the majority of WW-derived NDMA precursors can be deactivated with ClO2 oxidation above neutral pH. This was attributed to the better oxidative reaction of ClO2 with amines that have lone pair electrons to be shared at higher oxidation pH conditions. In addition, relatively short oxidation periods with ClO2 (i.e., ≤10 min) or low Ct (concentration × time, ~10 mg ∗ min/L) values were sufficient for the deactivation of WW-derived NDMA precursors. ClO2 oxidation was effective in freshly WW-impacted waters. Natural attenuation processes (e.g., sorption, biodegradation, etc.) can change the reactivity of WW-derived NDMA precursors for oxidation with ClO2. The effect of ClO2 on the removal of THM precursors was low (<25%) and independent of oxidation conditions. Given the low formation of regulated THMs and HAAs, ClO2 oxidation presents a viable option for the simultaneous control of NDMA and regulated DBP formation during water treatment, especially for utilities treating WW-impacted water sources.

Reduction by enhanced coagulation of dissolved organic nitrogen as a precursor of N-nitrosodimethylamine

ABSTRACTRaw water from the Banglen (BL) water treatment plant (WTP) and Bangkhen (BK) WTP in central Thailand and Hatyai (HY) WTP in southern Thailand was investigated for dissolved organic nitrogen (DON) reduction. The DON(mg N/L) and the dissolved organic carbon (DOC)/DON ratio were 0.34 and 21, 0.24 and 18, and 1.12 and 3 for the raw waters from BL, BK, and HY WTPs, respectively. Polyaluminum chloride (PACl) dosages of 150, 80, and 40 mg/L at pH 7 were the optimal coagulation conditions for the raw waters from BL, BK, and HY WTPs, respectively, and could reduce DON by 50%, 42%, and 42%, respectively. PACl and powder activated carbon (PAC, both in mg/L) at 150 and 20, 80 and 20, and 40 and 60 could reduce DON in the raw waters from BL, BK, and HY WTPs by 71%, 67%, and 29%, respectively. DOC/DON values of water treated with PACl were similar to those of raw water. DOC/DON values of water treated with PACl and PAC were lower than those of raw water. N-nitrosodimethylamine (NDMA) formation potentials of raw water, water treated with PACl, or both PACl and PAC, and organic fractions of BL, BK, and HY WTPs were below the detection limits of 542 and 237 ng/L, respectively. Reductions in fluorescence intensities of tryptophan-like substances at peaks 240/350 and 280/350 (nmEx/nmEm) were moderately (correlation coefficient, R = 0.85 and 0.86) and fairly (R = 0.59, 0.67, and 0.75) correlated with DON reduction.

Effect of oxidation on amine-based pharmaceutical degradation and N-Nitrosodimethylamine formation

Four pharmaceuticals (ranitidine, nizatidine, doxylamine, and carbinoxamine) were selected as model compounds to assess the efficiency of four oxidants (ozone (O3), chlorine (Cl2), chlorine dioxide (ClO2) and potassium permanganate (KMnO4)) on the removal of amine-based pharmaceutical and personal care products (PPCPs), as well as the reduction of their N-Nitrosodimethylamine formation potentials (NDMAFPs). The changes in PPCPs and their NDMAFPs during oxidation were quantified using various oxidants and dosages. The relationship between oxidation product structures and NDMAFP changes was also analyzed. The results showed that oxidation with O3, Cl2 and ClO2 were effective in removing the selected PPCPs. However, only ozonation was effective in reducing their NDMAFPs. Ozonation at 6 mg/L removed approximately 90% PPCPs and 90% NDMAFPs for all PPCPs. In addition, the results indicated that ozonation products made little contribution to NDMAFPs. In contrast, some PPCP products had higher NDMAFPs than PPCPs after oxidation with Cl2, ClO2 and KMnO4. There were two possible reaction pathways that led to decrease in NDMAFPs after oxidation. One was oxygen transfer to nitrogen at the tertiary amine site and the other was N-dealkylation from the tertiary amine site.

Assessing trihalomethanes (THMs) and N-nitrosodimethylamine (NDMA) formation potentials in drinking water treatment plants using fluorescence spectroscopy and parallel factor analysis

The formation of disinfection byproducts (DBPs) is a major challenge in drinking water treatments. This study explored the applicability of fluorescence excitation–emission matrices and parallel factor analysis (EEM–PARAFAC) for assessing the formation potentials (FPs) of trihalomethanes (THMs) and N-nitrosodimethylamine (NDMA), and the treatability of THM and NDMA precursors in nine drinking water treatment plants. Two humic-like and one tryptophan-like components were identified for the samples using PARAFAC. The total THM FP (TTHM FP) correlated strongly with humic-like component C2 (r=0.874), while NDMA FP showed a moderate and significant correlation with the tryptophan-like component C3 (r=0.628). The reduction by conventional treatment was more effective for C2 than C3, and for TTHM FP than NDMA FP. The treatability of DOM and TTHM FP correlated negatively with the absorption spectral slope (S275–295) and biological index (BIX) of the raw water, but it correlated positively with humification index (HIX). Our results demonstrated that PARAFAC components were valuable for assessing DBPs FP in drinking water treatments, and also that the raw water quality could affect the treatment efficiency.

Seasonal and temporal patterns of NDMA formation potentials in surface waters

The seasonal and temporal patterns of N-nitrosodimethylamine (NDMA) formation potentials (FPs) were examined with water samples collected monthly for 21 month period in 12 surface waters. This long term study allowed monitoring the patterns of NDMA FPs under dynamic weather conditions (e.g., rainy and dry periods) covering several seasons. Anthropogenically impacted waters which were determined by high sucralose levels (>100 ng/L) had higher NDMA FPs than limited impacted sources (<100 ng/L). In most sources, NDMA FP showed more variability in spring months, while seasonal mean values remained relatively consistent. The study also showed that watershed characteristics played an important role in the seasonal and temporal patterns. In the two dam-controlled river systems (SW A and G), the NDMA FP levels at the downstream sampling locations were controlled by the NDMA levels in the dams independent of either the increases in discharge rates due to water releases from the dams prior to or during the heavy rain events or intermittent high NDMA FP levels observed at the upstream of dams. The large reservoirs and impoundments on rivers examined in this study appeared serving as an equalization basin for NDMA precursors. On the other hand, in a river without an upstream reservoir (SW E), the NDMA levels were influenced by the ratio of an upstream wastewater treatment plant (WWTP) effluent discharge to the river discharge rate. The impact of WWTP effluent decreased during the high river flow periods due to rain events. Linear regression with independent variables DOC, DON, and sucralose yielded poor correlations with NDMA FP (R2 < 0.27). Multiple linear regression analysis using DOC and log [sucralose] yielded a better correlation with NDMA FP (R2 = 0.53).

N-nitrosodimethylamine and trihalomethane formation and minimisation in Southeast Queensland drinking water

This study assesses the prevalence of disinfection by-product (DBP) precursors in some Southeast Queensland drinking water sources by conducting formation potential experiments for the four regulated trihalomethanes (THMs), and the potent carcinogen, N-nitrosodimethylamine (NDMA). NDMA formation potentials were consistently low (<5-21 ng/L), and total THM (tTHM) formation potentials were consistently below the Australian Drinking Water Guideline (250 μg/L). NDMA concentration of finished drinking waters was also monitored and found to be <5 ng/L in all cases. The effect of coagulation and advanced oxidation on the formation of NDMA and THMs is also reported. UV/H(2)O(2) pre-treatment was effective in producing water with very low THMs concentrations, and UV irradiation was an effective method for NDMA degradation. H(2)O(2) was not required for the observed NDMA degradation to occur. Coagulation using alum, ferric chloride or poly(diallyldimethylammonium chloride) (polyDADMAC) was ineffective in removing DBPs precursors from the source water studied, irrespective of the low dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) attained. Rather, coagulation with polyDADMAC caused an increase in NDMA formation potential upon chloramination, and all coagulants led to an increased tTHM formation potential upon chlorination due to the high bromide concentration of the source water studied.

Oxidation of suspected N-nitrosodimethylamine (NDMA) precursors by ferrate (VI): Kinetics and effect on the NDMA formation potential of natural waters

The potential of ferrate (Fe(VI)) oxidation to remove N-nitrosodimethylamine (NDMA) precursors during water treatment was assessed. Apparent second-order rate constants ( k app) for the reactions of NDMA and its suspected precursors (dimethylamine (DMA) and 7 tertiary amines with DMA functional group) with Fe(VI) were determined in the range of pH 6–12. Four model NDMA precursors (dimethyldithiocarbamate, dimethylaminobenzene, 3-(dimethylaminomethyl)indole and 4-dimethylaminoantipyrine) showed high reactivity toward Fe(VI) with k app values at pH 7 between 2.6×10 2 and 3.2×10 5 M −1 s −1. The other NDMA precursors (DMA, trimethylamine, dimethylethanolamine, dimethylformamide) and NDMA had k app values ranging from 0.55 to 9.1 M −1 s −1 at pH 7. In the second part of the study, the NDMA formation potentials (NDMA-FP) of the model NDMA precursors and natural waters were measured with and without pre-oxidation by Fe(VI). For most of the NDMA precursors with the exception of DMA, a significant reduction of the NDMA-FP (>95%) was observed after complete transformation of the NDMA precursor. This result was supported by low yields of DMA from the Fe(VI) oxidation of tertiary amine NDMA precursors. Pre-oxidation of several natural waters (rivers Rhine, Neckar and Pfinz) with a high dose of Fe(VI) (0.38 mM=21 mg L −1 as Fe) led to removals of the NDMA-FP of 46–84%. This indicates that the NDMA precursors in these waters have a low reactivity toward Fe(VI) because it has been shown that for fast-reacting NDMA precursors Fe(VI) doses of 20 μM (1.1 mg L −1 as Fe) are sufficient to completely oxidize the precursors.

Oxidation of N-Nitrosodimethylamine (NDMA) Precursors with Ozone and Chlorine Dioxide: Kinetics and Effect on NDMA Formation Potential

The oxidation of N-nitrosodimethylamine (NDMA) precursors chlorine dioxide (ClO2). Second-order rate constants for the reactions of model NDMA precursors (dimethylamine (DMA) and 7 tertiary amines) with ozone (kapp at pH 7 = 2.4 x 10(-1) to 2.3 x 10(9) M(-1) s(-1)), ClO2 (kapp at pH 7 = 6.7 x 10(-3) to 3.0 x 10(7) M(-1) s(-1)), and hydroxyl radical (*OH) (kapp at pH 7 = 6.2 x 10(7) to 1.4 x 10(10) M(-1) s(-1)) were determined, which showed that the selected NDMA precursors, with the exception of dimethylformamide (DMFA) can be completely transformed via their direct reaction with ozone. During ozonation, DMFA may be partially transformed through oxidation by the secondary oxidant *OH. ClO2 was also shown to effectively transform most of the precursors, with the exceptions of DMA and DMFA. In the second part of the study, the NDMA formation potentials (NDMA-FP) in synthetic and natural waters were measured with and without pre-oxidation with ozone and ClO2. A significant reduction in the NDMA-FPs was observed after complete transformation of the model NDMA precursors. Ozonation generally led to more effective reduction of the NDMA-FP than ClO2. For most of the precursors, the formation of DMA could account for the NDMA-FPs remaining after complete transformation of the model NDMA precursors. In contrast, dimethylethanolamine and dimethyldithiocarbamate yielded other NDMA precursors (not DMA) as their oxidation products. Pre-oxidation by ozone and ClO2 of several natural waters showed behavior similar to that of the oxidation of model NDMA precursors with a reduction of the NDMA-FP by 32-94% for various natural water sources.

Fluorescence fingerprints to monitor total trihalomethanes and N-nitrosodimethylamine formation potentials in water

Water samples from 56 lakes of Missouri, USA, were analysed for their fluorescence excitation/emission matrix (EEM) spectroscopy and the formation potentials of total trihalomethanes (TTHM) and N-nitrosodimethylamine (NDMA). Comparing the excitation/emission matrix fingerprints with trihalomethanes formation revealed that water with higher fluorescence intensity generally exhibited higher trihalomethanes formation potential. Moreover, waters with fluorescence centre at excitation: 290–310 nm/emission: 330–350 nm were related to high N-nitrosodimethylamine and trihalomethanes formation potentials. The results suggest that excitation/emission matrix fingerprints could be used as surrogate parameters for monitoring trihalomethanes and N-nitrosodimethylamine formation potentials.