Class Of Nitrogenous Disinfection Byproducts Research Articles

Functional UiO-66 for highly selective adsorption of N-nitrosodipropylamine: adsorption performance and mechanisms.

N-Nitrosodipropylamine (NDPA) is a class of nitrogenous disinfection by-products (N-DBPs) with high toxicity. Although NDPA present in water bodies is at relatively low concentrations, the potential risk is high due to its high toxicity and bioaccumulation. Metal-organic frameworks (MOFs), a new type of porous material with remarkable functionality, have shown great performance in a wide variety of applications in adsorption. This is the first study investigating the adsorption of MOFs on NDPA. Herein, UiO-66 with -NH2 and imidazolium functional groups were synthesized by modifying UiO-66 after amination. Adsorption kinetics and isotherm models were used to compare the adsorption properties of the two materials for low-concentration NDPA in water. The results showed that the behavior of all the adsorbents was consistent with the Langmuir model and the pseudo-second-order model and that the adsorption was homogeneous chemisorption. The structures of the nanoparticles were characterized by FTIR, zeta potential, XRD, SEM and BET measurements. Based on the characteristics, four adsorption mechanisms, namely electron conjugation, coordination reaction, anion-π interaction, and van der Waals forces, were simultaneously involved in the adsorption. The influencing factor experiment revealed that the adsorption of UiO-66-NH2 and (I-)Meim-UiO-66 involved hydrogen bonding and electrostatic interactions, respectively.

Haloacetonitrile stability in cell culture media used in vitro toxicological studies

Haloacetonitriles (HANs) are an emerging class of nitrogenous disinfection by-products (DBPs) formed in disinfected drinking water and have been reported to be more cyto- and genotoxic than the regulated DBPs. HANs are also known to hydrolyze under neutral pH and normal room temperature. However, the stability of HANs has not been well characterized in DBP toxicological assessments. Most toxicological assessments expose DBPs up to several days which may result in a mixture of HANs and degradation products that might have underestimated HAN toxicity. In this study, HANs stability was characterized in 1) a buffer solution in sealed vials, 2) cell culture media (CCM) in sealed vials, and 3) CCM in 96 sealed well plates with 5% CO2. Solutions were incubated at 37 °C for 3 days. MonoHANs were found to be stable in buffer and CCM except when HANs were incubated in CCM in plates where they could possibly be affected by volatilization and photodegradation during sample handling. However, di- and tri- HANs degraded between 70 and 100% in both buffer solution and CCM. They were also found to be less stable in CCM than in buffer solution possibly from HANs reacting with nucleophiles present in CCM (i.e., amino acids). Identified degradation products include corresponding haloacetamides and haloacetic acids for buffer solutions and only haloacetic acids and an unknown brominated compound for CCM. Results of this study suggests that reported toxicity values might have been underestimated and should consider changing CCM and DBP on a daily basis for a more accurate toxicity measurement.

Structural and functional alterations of intestinal flora in mice induced by halonitromethanes exposure.

Halonitromethanes (HNMs) as one typical class of nitrogenous disinfection byproducts (DBPs) have been widely found in drinking water and are receiving more and more attentions because of their high cytotoxicity, genotoxicity, and developmental toxicity. However, the effects of HNMs exposure on the intestinal tract and intestinal flora remain unknown. This study comprehensively determined the effects of trichloronitromethane, bromonitromethane, and bromochloronitromethane exposure on the intestinal tract and intestinal flora. Results showed that the three HNMs induced intestinal oxidative stress and inflammatory response. Further, HNMs exposure could change the diversities and community structure of intestinal flora, thereby triggering intestinal flora dysbiosis, which might be associated with the intestinal damage such as oxidative stress and inflammation. The intestinal flora dysbiosis was accompanied with mark alterations in function of intestinal flora, such as carbohydrate, lipid, and amino acid metabolisms. This research provides a new insight into studying the toxicity of HNMs exposure based on intestinal flora, which will further improve the health risk assessment of DBPs in drinking water.

Formation and transformation of halonitromethanes from dimethylamine in the presence of bromide during the UV/chlorine disinfection

Halonitromethanes (HNMs) is a typical class of nitrogenous disinfection byproducts with high toxicity. The effect of Br− on the formation and transformation of HNMs from dimethylamine (DMA) during the ultraviolet (UV)/chlorine disinfection has been investigated in current study. Results reveal that only chloronitromethane, dichloronitromethane and trichloronitromethane (TCNM) could be found during the UV/chlorine disinfection. Whereas in the presence of Br−, nine species of HNMs could be observed simultaneously. When Br− concentration increased from 0 to 15.0 mg L−1, the predominant species of HNMs were gradually changed from TCNM to dibromonitromethane and tribromonitromethane, which contributed to 23.37% and 31.07% of total HNMs concentration at 15 mg L−1 Br−, respectively. The presence of Br− not only shifted the chlorinated-HNMs (Cl-HNMs) towards brominated-HNMs (Br-HNMs) but also affected the dominant species and total concentration of HNMs. When Br− concentration was 4.0 mg L−1, the formation of HNMs decreased with the increase of pH from 6.0 to 8.0 and increased with the increase of free chlorine and DMA. When free chlorine concentration rose from 0.25 to 1.1 mmol L−1, Br-HNMs were shifted to Br(Cl)-HNMs and then to Cl-HNMs. According to the findings, possible formation and transformation pathways of HNMs from DMA were proposed in the presence of Br− during the UV/chlorine disinfection. Finally, it was proved that the effect of Br− on the trend of HNMs in real water was similar to that in deionized water, but higher HNMs concentrations and delayed peak time were observed in real water. This study can provide the scientific evidence and fundamental data for the applications of UV/chlorine disinfection in the treatment of water containing Br−.

Nanoscale zero-valent iron particles supported on MIL-96: a novel material for adsorption-degradation of trichloronitromethane.

As an emerging class of nitrogenous disinfection by-products, halonitromethanes have caused public health concerns owing to their high toxicity. More and more attention has been paid to the new materials and technologies for the removal of halonitromethanes. In this study, a novel material, nanoscale zero-valent iron (nZVI) supported on MIL-96 (nZVI@MIL-96) with favorable stability and reusability, was synthesized and applied to the adsorption-degradation of trichloronitromethane (TCNM) in the water. The results revealed that almost all the TCNM could be removed under 20 mg/L nZVI@MIL-96 dosage with a wide temperature range. The optimum mass ratio of nZVI to MIL-96 was 1:2, and the TCNM adsorption-degradation followed a pseudo-first-order model. The coexisting ions, such as SO42-, PO43-, and NO3-, with high concentration brought adverse effects on the removal of TCNM; however, the effects of Cl- and CO32- were insignificant. The concentrations of aluminum and iron ions in water were all within the standard value after adsorption with the nZVI@MIL-96. The degradation mechanism of TCNM by nZVI@MIL-96 included two steps, namely, adsorption and degradation, and methylamine was the terminal dechlorination and denitration products. In a word, the as-prepared nZVI@MIL-96 nanoparticles demonstrated the capabilities as a material of adsorption-degradation of TCNM in the water.

Developmental toxicity of disinfection by-product monohaloacetamides in embryo-larval stage of zebrafish.

As an emerging class of nitrogenous disinfection by-products (N-DBPs), haloacetamides (HAcAms) have been widely detected in drinking water. Limited toxicity studies have shown an inconsistent toxicity of monoHAcAms, including CAcAm, BAcAm and IAcAm. In this study, the developmental toxicity of monoHAcAms was evaluated in embryo-larval stage of zebrafish. Embryos were exposed to one concentration of 2.50, 5.00, 10.0, 20.0, 40.0 and 80.0mg/L monoHAcAms from 4h post-fertilization (hpf) to 120 hpf. Multiple endpoints, including hatching rate, morphological abnormalities, mortality as well as locomotor behavior were assessed at specified stages (24, 48, 72, 96 and 120 hpf). Results showed that 80mg/L CAcAm and 40mg/L BAcAm significantly decreased the hatching rate, IAcAm decreased the hatching rate and delayed the hatching process in a concentration-dependent manner with an EC50 of 16.37mg/L at 72 hpf. The frequency and severity order of morphological abnormalities increased with the raised exposure concentrations and prolonged exposure time, and the corresponding EC50 at 96 hpf were 21.10, 9.77 and 16.60mg/L for CAcAm, BAcAm and IAcAm, respectively. MonoHAcAms exposure resulted in a time- and dose-dependent response in mortality and the calculated LC50 at 72 hpf were 38.44, 17.74 and 28.82mg/L for CAcAm, BAcAm and IAcAm, respectively. Based on EC50 for morphological abnormalities and LC50, a toxicity rank order of BAcAm>IAcAm>CAcAm was observed. Different degrees of hyperactivity and hypoactivity were observed from locomotor behavior analysis in larvae from ≤10.0mg/L monoHAcAms exposure groups. The light-dark periodic change was disappeared in larvae of 10.0mg/L BAcAm exposure group. In summary, our study showed that monoHAcAms were developmentally toxic to zebrafish even at very low concentrations and BAcAm exerted higher toxicity than IAcAm and CAcAm. These results will further our understanding of the toxicity of HAcAms and its potential toxicological impact on human and ecological environment.

Removal Efficiency of Trichloroacetamide by UV/Sodium Sulfite

Haloacetamides (HAcAms) are an emerging class of nitrogenous disinfection by-products (N-DBPs) with high cytotoxicity and genotoxicity, which are widely detected in drinking water. The toxicity of trichloroacetamide (TCAcAm) is significantly higher than traditional DBPs. In this study, ultraviolet (UV) treatment was combined with sodium sulphite (Na2SO3) to remove TCAcAm from water. The effects of different light intensities, different agent dosages (Na2SO3), and pH conditions on the removal of TCAcAm by UV/Na2SO3 advanced reduction process were investigated. The results showed that TCAcAm could be rapidly degraded by the UV/Na2SO3 system. The degradation effect was directly proportional to light intensity, dosage of Na2SO3, and pH. Moreover, the pH had a significant effect on the reaction rate and degradation rate. As the pH increased from 6 to 9, the degradation rate of TCAcAm increased from 12.8% to 99.6%, in 120 min. The removal rate of TCAcAm reached 99.4% when the UV light intensity, pH, Na2SO3 dosage, and reaction time were 450 μW·cm-2, 9, 1.00 mmol·L-1, and 30 min, respectively. The experimental results indicated that the UV/Na2SO3 system is an efficient advanced reduction process for the removal of TCAcAm, and it has the potential to reduce other halogenated DBPs. Therefore, it could be used for the degradation of halogenated DBPs in the treatment of drinking water.

Rapid and complete dehalogenation of halonitromethanes in simulated gastrointestinal tract and its influence on toxicity

Halonitromethanes (HNMs) as one typical class of nitrogenous disinfection byproducts in drinking water and wastewater are receiving attentions due to their high toxicity. This study applied a simulator of the human gastrointestinal tract to determine the dehalogenation processes of trichloronitromethane, bromonitromethane and bromochloronitromethane for the first time. Influence of digestion process of HNMs on gut microbiota and hepatotoxicity was further analyzed. Results showed that the three HNMs were rapidly and completely dehalogenated in the gastrointestinal tract, especially in the stomach (2 h retention Time) and small intestine (4 h retention Time). Mucin, cysteine, pancreatin and bile salts in the digestive juice played major roles in the dehalogenation process. HNMs and their dehalogenation products in the resulting fluids of stomach induced the highest toxicity followed by those in intestine and colon, exhibiting dose-dependent effects. Although most HNMs were degraded in the stomach and small intestine, residual HNMs entered into colon changed the microbial community. Abundance of several genera, such as Bacteroides, Lachnospiraceae_unassigned and Lactobacillus had high correlation with exposure concentration of HNMs. This study sheds new light on dehalogenation and toxic processes of HNMs by oral exposure, which provides basic data for their human health risk assessment.

Comparative toxicity of chloro- and bromo-nitromethanes in mice based on a metabolomic method

Halonitromethanes (HNMs) as one typical class of nitrogenous disinfection byproducts have been widely found in drinking water. In vitro test found HNMs could induce higher cytotoxicity and genotoxicity than trihalomethanes and haloacetic acids. However, data on toxic effect from in vivo experiment is limited. In this study, bromonitromethane (BNM), bromochloronitromethane (BCNM) and trichloronitromethane (TCNM) were chosen as target HNMs, and exposed to mice for 30 d. Hepatic toxicity and serum metabolic profiles were determined to reveal toxic effects and mechanisms of the three HNMs. Results showed the three HNMs significantly decreased relative liver weight, indicating liver is one of the target organs. Further, the three HNMs exposure damaged hepatic antioxidant defense system, and increased oxidative DNA damage. Nuclear magnetic resonance based metabolomics analysis found amino acid metabolism and carbohydrate metabolism were disturbed by HNMs exposure. Some metabolites in these metabolisms are related to oxidative stress and damage. Combined with above results, BNM had the highest toxicity, followed by BCNM and TCNM, indicating bromo-HNMs had higher toxicity than chloro-HNMs. Induction of oxidative stress is one of the toxicity mechanisms of HNMs. This study firstly provides the insight into in vivo toxicity of HNMs and their underlying mechanisms based on metabolomics methods, which is very useful for their health risk assessment in drinking water.

Metabolomics evaluation of the in vivo toxicity of bromoacetonitriles: One class of high-risk nitrogenous disinfection byproducts.

Bromoacetonitriles (BANs), one class of nitrogenous disinfection byproducts (N-DBPs), have frequently been detected in drinking water. The cytotoxicity and genotoxicity of BANs have been demonstrated in mammalian cells. However, a systematic study of the in vivo toxicity of BANs is rare. In this study, metabolomics combined with histopathology and oxidative stress analysis were used to evaluate the toxicity of BANs in mice. The results indicated that BAN exposure induced liver and kidney injury in mice. Furthermore, the superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities decreased, and the level of malonaldehyde (MDA) increased in mice livers due to BANs exposure, which indicated that hepatic oxidative stress was induced. These toxicities increased with an increasing number of bromine at the α carbon. In addition, BAN exposure disrupted the metabolic pathways of amino acid, energy and lipid metabolism in mice. Our results provide evidence for the comprehensive omics endpoints of the in vivo toxicity of BANs.

Peptide bonds affect the formation of haloacetamides, an emerging class of N-DBPs in drinking water: free amino acids versus oligopeptides.

Haloacetamides (HAcAms), an emerging class of nitrogenous disinfection by-products (N-DBPs) of health concern, have been frequently identified in drinking waters. It has long been appreciated that free amino acids (AAs), accounting for a small fraction of the dissolved organic nitrogen (DON) pool, can form dichloroacetamide (DCAcAm) during chlorination. However, the information regarding the impacts of combined AAs, which contribute to the greatest identifiable DON portion in natural waters, is limited. In this study, we compared the formation of HAcAms from free AAs (tyrosine [Tyr] and alanine [Ala]) and combined AAs (Tyr-Ala, Ala-Tyr, Tyr-Tyr-Tyr, Ala-Ala-Ala), and found that HAcAm formation from the chlorination of AAs in combined forms (oligopeptides) significantly exhibited a different pattern with HAcAm formation from free AAs. Due to the presence of peptide bonds in tripeptides, Tyr-Tyr-Tyr and Ala-Ala-Ala produced trichloroacetamide (TCAcAm) in which free AAs was unable to form TCAcAm during chlorination. Moreover, peptide bond in tripeptides formed more tri-HAcAms than di-HAcAms in the presence of bromide. Therefore, the peptide bond may be an important indicator to predict the formation of specific N-DBPs in chlorination. The increased use of algal- and wastewater-impacted water as drinking water sources will increase health concerns over exposure to HAcAms in drinking water.

Mice in vivo toxicity studies for monohaloacetamides emerging disinfection byproducts based on metabolomic methods.

Haloacetamides (HAcAms) as a new class of nitrogenous disinfection byproducts (N-DBPs) have been widely detected in drinking water and reclaimed water. Cytotoxicity and genotoxicity of monoHAcAms are determined by the leaving tendency of the halogens and decrease following a rank order of iodoacetamide (IAcAm)>bromoacetamide (BAcAm)≫chloroacetamide (CAcAm). However, the in vivo toxicity date for monoHAcAms is limited. In this study, hepatic oxidative stress and metabolomics responses in mice corresponding to monoHAcAms exposure were investigated. Exposure to the monoHAcAms decreased the activities of catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) and the levels of malonaldehyde (MDA) and increased the level of 8-hydroxy-2-deoxyguanosine (8-OHdG), indicating that each exposure generated oxidative stress in mice liver. Metabolomic alterations were also induced by each monoHAcAms exposure. In addition, disruptions of metabolic pathways, related to amino acid, energy and lipid metabolism, were identified based on the significantly changed metabolites. These data, for the first time, provide a comprehensive view for the toxic effects of monoHAcAms.

Formation and speciation of nine haloacetamides, an emerging class of nitrogenous DBPs, during chlorination or chloramination

Haloacetamides (HAcAms) are an emerging class of nitrogenous disinfection by-products (N-DBPs) of health concern. However, there are very limited data on the formation and speciation of the nine bromine- and chlorine-containing haloacetamides (HAcAm9). In the study, their formation and speciation during chlor(am)ination were investigated for a group of waters with a range of specific ultraviolet absorbance at 254nm (SUVA254), dissolved organic nitrogen (DON), and bromide levels. The waters that were the least impacted by anthropogenic pollution had the lowest DON levels, the highest ratios of dissolved organic carbon (DOC) to DON, and exhibited the least HAcAm9 formation. DON/DOC may act as an indicator of HAcAm yields during chlorination. HAcAm9 exhibited more formation during chloramination in the low-SUVA waters with no bromide, relative to high-SUVA waters with bromide. The selected waters all formed primarily dihalogenated (di-) HAcAms, followed by trihalogenated (tri-) species and, to a much lesser extent, monohalogenated (mono-) HAcAms. Di-HAcAm formation had similar trends as that of HAcAm9; whereas chloramination formed more mono- and less tri-HAcAms than chlorination. Bromine utilization factors and bromine incorporation factor increased with decreasing and increasing bromide during either chlorination or chloramination, and bromine was easier to incorporate into tri-HAcAms during chloramination than chlorination.

Solvent-minimized extraction for determining halonitromethanes and trihalomethanes in water

Halonitromethanes (HNMs) are a class of nitrogenous disinfection by-products (N-DBPs) that have so far received little attention and focused largely on trichloronitromethane. By contrast, trihalomethanes (THMs) are the most commonly regulated DBPs and have been the subject of much study. This paper reports the first miniaturized system for the simultaneous determination of the nine known HNMs and four THMs in tap and swimming pool water. Micro liquid–liquid extraction (MLLE) is an adaptation of EPA Method 551.1 using ethyl acetate instead of methyl tert-butyl ether as extractant and large injected sample volumes (30μL) in combination with programmed temperature vaporizer–gas chromatography–mass spectrometry for improved sensitivity and selectivity. Because extraction is done with a few microlitres of organic solvent (200μL) and practically all extract is injected into the instrument, MLLE can be regarded as a virtually solvent-free sample preparation technique. The proposed method provided an extraction efficiency of ∼85%, average limits of detection (tribromonitromethane excluded) of 30ng/L and relative standard deviations of ∼6.0%. The influence of various dechlorinating agents on the stability of the thirteen target analytes in treated water was evaluated; the only salt allowing both types of compounds to be efficiently preserved was (NH4)2SO4, but only for 1 day at 4°C. Therefore, acidifying the sample at pH ∼3.4—the optimum value for MLLE—at the time of collection is recommended in order to ensure that both HNMs and THMs retain their integrity for 2 days during storage at 4°C.

Precursors of Dichloroacetamide, an Emerging Nitrogenous DBP Formed during Chlorination or Chloramination

Haloacetamides (HAcAms) are an emerging class of nitrogenous disinfection byproducts (N-DBPs). However, there is a limited understanding about the precursors of HAcAms. In this study, we screened the precursors of dichloroacetamide (DCAcAm), the most commonly identified HAcAm in chlorinated or chloraminated drinking water. DCAcAm formation potential (FP) of raw water samples collected in different months from a reservoir in China was determined during chlorination, and the highest DCAcAm FP typically occurred in the summer samples. Dissolved organic matter (DOM) in a representative summer raw water sample was separated into six fractions by a series of resin elutions. Among them, hydrophilic acid (HiA) DOM showed the maximum DCAcAm FP, followed by hydrophilic bases (HiB) and, to a much lower extent, hydrophobic acids (HoA). Fluorescence excitation-emission matrix (EEM) spectra revealed that a mass of protein-like substances in the HiA fraction, made up of amino acids (AAs), were the likely DCAcAm precursors. Finally, we investigated the DCAcAm yields of 20 AAs during chlorination. Among them, seven AAs (aspartic acid, histidine, tyrosine, tryptophan, glutamine, asparagine, phenylalanine) could form DCAcAm during chlorination, with the corresponding DCAcAm yields of 0.231, 0.189, 0.153, 0.104, 0.078, 0.058, and 0.050 mmol/mol AA.