Animal Feedlots and Domestic Wastewater Discharges are Likely Sources of N-Nitrosodimethylamine (NDMA) Precursors in Midwestern Watersheds.

N-nitrosodimethylamine (NDMA) precursor concentrations along four major rivers in Minnesota, USA were quantified and correlated with watershed land cover types, anthropogenic activity, and organic matter characteristics. River water samples (36 in total) were chloraminated under uniform formation conditions (UFC) before and after lime-softening treatment, and the resulting NDMA concentrations were quantified (NDMAUFC). Regarding land cover, NDMAUFC in raw river water exhibited weak positive correlations with urban land (ρ = 0.33, p = 0.05) and cropland coverage (ρ = 0.35, p = 0.04). For anthropogenic activity, NDMAUFC in raw river water positively correlated with the number of feedlots (ρ = 0.57), total weight of animals (ρ = 0.68), and total number of domestic wastewater treatment plants (WWTPs; ρ = 0.63) with p < 0.01. NDMAUFC positively correlated with region IV fluorescence intensity from fluorescence excitation-emission spectra (ρ = 0.70, p < 0.01). Lime softening of river water typically increased NDMAUFC and preferentially removed organic matter that fluoresces in region V, suggesting that the organic matter in this region decreases NDMAUFC by competing for available chloramines. Overall, animal feedlots, along with domestic WWTPs, are predominant sources of NDMA precursors in the studied watersheds, while croplands and urban runoff are of lesser importance.

Formation and toxicity alteration of halonitromethanes from Chlorella vulgaris during UV/chloramination process involving bromide ion.

Frequent algal blooms cause algal cells and their algal organic matter (AOM) to become critical precursors of disinfection by-products (DBPs) during water treatment. The presence of bromide ion (Br-) in water has been demonstrated to affect the formation laws and species distribution of DBPs. However, few researchers have addressed the formation and toxicity alteration of halonitromethanes (HNMs) from algae during disinfection in the presence of Br-. Therefore, in this work, Chlorella vulgaris was selected as a representative algal precursor to investigate the formation and toxicity alteration of HNMs during UV/chloramination involving Br-. The results showed that the formation concentration of HNMs increased and then decreased during UV/chloramination. The intracellular organic matter of Chlorella vulgaris was more susceptible to form HNMs than the extracellular organic matter. When the Br-: Cl2 mass ratio was raised from 0.004 to 0.08, the peak of HNMs total concentration increased 33.99%, and the cytotoxicity index and genotoxicity index of HNMs increased 67.94% and 22.80%. Besides, the formation concentration and toxicity of HNMs increased with increasing Chlorella vulgaris concentration but decreased with increasing solution pH. Possible formation pathways of HNMs from Chlorella vulgaris during UV/chloramination involving Br- were proposed based on the alteration of nitrogen species and fluorescence spectrum analysis. Furthermore, the formation laws of HNMs from Chlorella vulgaris in real water samples were similar to those in deionized water samples. This study contributes to a better comprehension of HNMs formation from Chlorella vulgaris and provides valuable information for water managers to reduce hazards associated with the formation of HNMs.

Chloramination of Nitromethane: Incomplete Chlorination and Unexpected Substitution Reaction.

Ozone is commonly used as a predisinfectant in potable water reuse treatment trains. Nitromethane was recently found as a ubiquitous ozone byproduct in wastewater, and the key intermediate toward chloropicrin during subsequent secondary disinfection of ozonated wastewater effluent with chlorine. However, many utilities have switched from free chlorine to chloramines as a secondary disinfectant. The reaction mechanism and kinetics of nitromethane transformation by chloramines, unlike those for free chlorine, are unknown. In this work, the kinetics, mechanism, and products of nitromethane chloramination were studied. The expected principal product was chloropicrin, because chloramines are commonly assumed to react similarly to, although more slowly than, free chlorine. Different molar yields of chloropicrin were observed under acidic, neutral, and basic conditions, and surprisingly, transformation products other than chloropicrin were found. Monochloronitromethane and dichloronitromethane were detected at basic pH, and the mass balance was initially poor at neutral pH. Much of the missing mass was later attributed to nitrate formation, from a newly identified pathway involving monochloramine reacting as a nucleophile rather than a halogenating agent, through a presumed SN2 mechanism. The study indicates that nitromethane chloramination, unlike chlorination, is likely to produce a range of products, whose speciation is a function of pH and reaction time.

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.

Generation Mechanism of Perfluorohexanesulfonic Acid from Polyfluoroalkyl Sulfonamide Derivatives During Chloramination in Drinking Water.

Per- and polyfluoroalkyl substances (PFASs), including perfluorohexanesulfonic acid (PFHxS), as emerging persistent organic pollutants widely detected in drinking water, have drawn increasing concern. The PFHxS contamination of drinking water always results from direct and indirect sources, especially the secondary generations through environmental transformations of precursors. However, the mechanism of the transformation of precursors to PFHXS during the drinking water treatment processes remains unclear. Herein, the potential precursors and formation mechanisms of PFHxS were explored during drinking water disinfection. Simultaneously, the factors affecting PFHxS generation were also examined. This study found PFHxS could be generated from polyfluoroalkyl sulfonamide derivatives during chlorination and chloramination. The fate and yield of PFHxS varied from different precursors and disinfection processes. In particular, monochloramine more favorably formed PFHxS. Several perfluoroalkyl oxidation products and decarboxylation intermediates were detected and identified in the chloraminated samples using Fourier-transform ion cyclotron resonance mass spectrometry. Combined with density functional theory calculations, the results indicated that the indirect oxidation via the attack of the nitrogen atom in sulfonamide groups might be the dominant pathway for generating PFHxS during chloramination, and the process could be highly affected by the monochloramine dose, pH, and temperature. This study provides important evidence of the secondary formation of PFHxS during drinking water disinfection and scientific support for chemical management of PFHxS and PFHxS-related compounds.

Aspartame-Sweetened Tap Water: Transformation Products and 2,6-Dichloro-1,4-Benzoquinone Formation.

Aspartame (APM), a dipeptide of aspartic acid (ASP) and phenylalanine (PHE), is a widely used artificial sweetener in beverages. It is unclear whether residual chlorine in tap water can react with APM to form disinfection byproducts (DBPs). Therefore, we investigated the formation of DBPs from the reaction of APM with residual chlorine in authentic tap water. APM and a commercial sweetener (CS) packet containing APM were studied under authentic and simulated tap water conditions. Eight chlorinated products of APM were detected using solid-phase extraction (SPE) and high performance liquid chromatography quadrupole time-of-flight mass spectrometry (HPLC-QTOF-MS). These new chloro-products were tentatively identified based on accurate masses, isotopic patterns of 35,37Cl, and MS/MS spectra. Furthermore, we identified APM as a precursor to 2,6-dichloro-1,4-benzoquinone (DCBQ). DCBQ significantly increased to 2.3-12 ng/L with the addition of APM or CS in tap waters collected from different locations compared to 1.4-1.8 ng/L in the same tap water samples without sweetener. DCBQ and two of the chlorinated transformation products were identified in cold prepared tea containing APM. DCBQ formation was eliminated when the residual chlorine in tap water was reduced by ascorbic acid or boiling prior to the addition of APM or CS. This study found that eight new DBPs and DCBQ were produced by the reactions of residual chlorine with APM and CS. These findings show an unintended exposure source of emerging DBPs via APM sweetened beverages.

Production of Dichloroacetonitrile from Derivatives of Isoxaflutole Herbicide during Water Treatment.

The herbicide isoxaflutole has the potential to contaminate drinking water directly, as well as upon hydrolyzing to its active form diketonitrile. Diketonitrile also may impact water quality by acting as a precursor for dichloroacetonitrile (DCAN), which is an unregulated but highly toxic disinfection byproduct (DBP). In this study, we investigated the reaction of diketonitrile with free chlorine and chloramine to form DCAN. We found that diketonitrile reacts with free chlorine within seconds but reacts with chloramine on the time scale of hours to days. In the presence of both oxidants, DCAN was generated at yields up to 100%. Diketonitrile reacted fastest with chlorine at circumneutral pH, which was consistent with base-catalyzed halogenation involving the enolate form of diketonitrile present at alkaline pH and electrophilic hypochlorous acid, which decreases in abundance above its pKa (7.5). In contrast, we found that diketonitrile reacts faster with chloramine as pH values decreased, consistent with an attack on the enolate by electrophilic protonated monochloramine that increases in abundance at acidic pH approaching its pKa (1.6). Our results indicate that increasing isoxaflutole use, particularly in light of the recent release of genetically modified isoxaflutole-tolerant crops, could result in greater occurrences of a high-yield DCAN precursor during disinfection.

Formation of regulated and unregulated disinfection byproducts during chlorination and chloramination: Roles of dissolved organic matter type, bromide, and iodide.

Algal blooms and wastewater effluents can introduce algal organic matter (AOM) and effluent organic matter (EfOM) into surface waters, respectively. In this study, the impact of bromide and iodide on the formation of halogenated disinfection byproducts (DBPs) during chlorination and chloramination from various types of dissolved organic matter (DOM, e.g., natural organic matter (NOM), AOM, and EfOM) were investigated based on the data collected from literature. In general, higher formation of trihalomethanes (THMs) and haloacetic acids (HAAs) was observed in NOM than AOM and EfOM, indicating high reactivities of phenolic moieties with both chlorine and monochloramine. The formation of haloacetaldehydes (HALs), haloacetonitriles (HANs) and haloacetamides (HAMs) was much lower than THMs and HAAs. Increasing initial bromide concentrations increased the formation of THMs, HAAs, HANs, and HAMs, but not HALs. Bromine substitution factor (BSF) values of DBPs formed in chlorination decreased as specific ultraviolet absorbance (SUVA) increased. AOM favored the formation of iodinated THMs (I-THMs) during chloramination using preformed chloramines and chlorination-chloramination processes. Increasing prechlorination time can reduce the I-THM concentrations because of the conversion of iodide to iodate, but this increased the formation of chlorinated and brominated DBPs. In an analogous way, iodine substitution factor (ISF) values of I-THMs formed in chloramination decreased as SUVA values of DOM increased. Compared to chlorination, the formation of noniodinated DBPs is low in chloramination.

Formation, speciation and toxicity of CX3R-type disinfection by-products (DBPs) from chlor(am)ination of 2,4-diaminobutyric acid (DAB).

2,4-diaminobutyric acid (DAB), a newly identified algal toxins in water, pose a great threat to human health. DAB may react with chlorine or chloramine to produce CX3R-type disinfection by-products (DBPs) during water treatment processes. This study mainly investigated the formation and speciation of DBPs from chlor(am)ination of DAB. The results revealed that haloacetic acids (HAAs), trihalomethanes (THMs) and haloacetonitriles (HANs) were the main kinds of CX3R-type DBPs generated from DAB during chlor(am)ination, of which dichloroacetic acid yielded the highest. The formation and total toxicity of four CX3R-type DBPs from DAB during chloramination was significantly lower than that during chlorination at each Cl2:N molar ratio. However, more formation of Br-THMs and I-THMs were observed during chloramination in the presence of Br-/I-. Futhermore, the effects of chlor(am)ine dosage, solution pH, reaction time, and the concentration of Br- and I- on the formation and speciation of CX3R-type DBPs were also evaluated during chlor(am)ination. The plausible formation pathways of CX3R-type DBPs from DAB were proposed and verified by theoretical calculation. The quantum chemistry calculations indicate that 1N in DAB and 8N in 2,4-diaminochlorobutyric acid (C4H9O2N2Cl) were more likely to be attacked by electrophiles, supporting the proposed pathway schemes.

Chlorination and chloramination of benzophenone-3 and benzophenone-4 UV filters.

The objective of this research was to explore the fundamental reactions between chlorine/chloramine and 2-hydroxyl-4-methoxyl benzophenone (BP3)/2-hydroxyl-4-methoxyl benzophenone-sulfonic acid (BP4), which were the most common reactions in benzophenone-type UV filters during drinking water treatment processes. Both BP3 and BP4 could react with free chlorine and chloramine, with reactions following pseudo-first-order kinetics in excess of chlorine (HClO) and chloramine (NH2Cl). Generally, chlorination was more rapid than chloramination. BP4 was less reactive than BP3 toward both chlorine and chloramine, due to the presence of an electron-accepting sulfonate group. Therefore, BP3 had a significantly higher disinfection by-products (DBP) formation potential than BP4. Chlorination of BP3 and BP4 generated remarkably higher levels of DBPs than chloramination, with high pH conditions facilitating the formation of chloroform but inhibiting the formation of haloacetic acid (HAAs). Comparison of the reaction behavior of two different BP-type UV filters, i.e., BP3 and BP4, revealed that certain functional groups significantly affected the reactivity of BP-type UV filters in chlorination and chloramination processes. This contribution may provide new insights into the reaction behavior of UV filters during drinking water disinfection process using chlorine and/or chloramine as disinfectant, and provide guidelines for drinking water safety management.

Regression models evaluating THMs, HAAs and HANs formation upon chloramination of source water collected from Yangtze River Delta Region, China.

Present study aimed to generate multiple regression models to estimate the formation of trihalomethanes (THMs), haloacetonitriles (HANs) and haloacetic acids (HAAs) during chloramination of source water obtained from Yangtze River Delta Region, China. The results showed that the regression models for trichloromethane (TCM), dichloroacetonitrile (DCAN), dichloroacetic acid (DCAA), dihaloacetic acids (DHAAs), 5 HAAs species regulated by U.S. EPA (HAA5) and total haloacetic acids (HAA9) have good evaluation ability (prediction accuracy reached 81-94%), while the models for total haloacetonitriles (HAN4), trichloroacetic acid (TCAA), trihaloacetic acids (THAAs) and total trihalomethanes (THM4), they appeared relative low prediction accuracy (58-72%). For THMs, dissolved organic nitrogen (DON) was their key organic precursor, yet for HAN, DHAAs and THAAs, UVA254 played the dominant role. The other key factors influencing DBP formation included the bromide (THM4, DHAAs and HAA9), reaction time (DCAN, HAN4), chloramine dose (TCM, DCAA, TCAA, HAA5 and THAAs). These results provided important information for water works to optimize the water treatment process to control DBPs, and give an evaluating method for DBPs levels when estimating the health risks related with DBP exposure during chloramination.

Formation and control of nitrogenous DBPs from Western Australian source waters: Investigating the impacts of high nitrogen and bromide concentrations.

We studied the formation of four nitrogenous DBPs (N-DBPs) classes (haloacetonitriles, halonitromethanes, haloacetamides, and N-nitrosamines), as well as trihalomethanes and total organic halogen (TOX), after chlorination or chloramination of source waters. We also evaluated the relative and additive toxicity of N-DBPs and water treatment options for minimisation of N-DBPs. The formation of halonitromethanes, haloacetamides, and N-nitrosamines was higher after chloramination and positively correlated with dissolved organic nitrogen or total nitrogen. N-DBPs were major contributors to the toxicity of both chlorinated and chloraminated waters. The strong correlation between bromide concentration and the overall calculated DBP additive toxicity for both chlorinated and chloraminated source waters demonstrated that formation of brominated haloacetonitriles was the main contributor to toxicity. Ozone-biological activated carbon treatment was not effective in removing N-DBP precursors. The occurrence and formation of N-DBPs should be investigated on a case-by-case basis, especially where advanced water treatment processes are being considered to minimise their formation in drinking waters, and where chloramination is used for final disinfection.

Chloramination of wastewater effluent: Toxicity and formation of disinfection byproducts.

The reclamation and disinfection of waters impacted by human activities (e.g., wastewater effluent discharges) are of growing interest for various applications but has been associated with the formation of toxic nitrogenous disinfection byproducts (N-DBPs). Monochloramine used as an alternative disinfectant to chlorine can be an additional source of nitrogen in the formation of N-DBPs. Individual toxicity assays have been performed on many DBPs, but few studies have been conducted with complex mixtures such as wastewater effluents. In this work, we compared the cytotoxicity and genotoxicity of wastewater effluent organic matter (EfOM) before and after chloramination. The toxicity of chloraminated EfOM was significantly higher than the toxicity of raw EfOM, and the more hydrophobic fraction (HPO) isolated on XAD-8 resin was more toxic than the fraction isolated on XAD-4 resin. More DBPs were also isolated on the XAD-8 resin. N-DBPs (i.e., haloacetonitriles or haloacetamides) were responsible for the majority of the cytotoxicity estimated from DBP concentrations measured in the XAD-8 and XAD-4 fractions (99.4% and 78.5%, respectively). Measured DBPs accounted for minor proportions of total brominated and chlorinated products, which means that many unknown halogenated compounds were formed and can be responsible for a significant part of the toxicity. Other non-halogenated byproducts (e.g., nitrosamines) may contribute to the toxicity of chloraminated effluents as well.

Comparative mammalian cell cytotoxicity of wastewater with elevated bromide and iodide after chlorination, chloramination, or ozonation.

Recycling wastewater is becoming more common as communities around the world try to better control their water resources against an increased frequency of either prolonged droughts or intense flooding. For communities in coastal areas, wastewaters may contain elevated levels of bromide (Br-) and iodide (I-) from seawater intrusion or high mineral content of source waters. Disinfection of such wastewater is mandatory to prevent the spread of pathogens, however little is known about the toxicity of wastewater after disinfection in the presence of Br- and I-. In this study we compared the induction of chronic cytotoxicity in mammalian cells in samples of municipal secondary wastewater effluent amended with elevated levels of Br-/I- after disinfection by chlorine, chloramines or ozone to identify which disinfection process generated wastewater with the lowest level of adverse biological response. Chlorination increased mammalian cell cytotoxicity by 5 times as compared to non-disinfected controls. Chloramination produced disinfected wastewater that expressed 6.3 times more cytotoxicity than the non-disinfected controls and was 1.3 times more cytotoxic than the chlorinated samples. Ozonation produced wastewater with cytotoxicity comparable to the non-disinfected controls and was at least 4 times less cytotoxic than the chlorine disinfected wastewaters. These results indicate that compared to chlorination and chloramination, ozonation of wastewater with high Br-/I- levels yielded the lowest mammalian cell cytotoxicity, suggesting its potential as a more favorable method to disinfect wastewater with minimizing the biological toxicity in mind.

Formation of iodo-trihalomethanes, iodo-haloacetic acids, and haloacetaldehydes during chlorination and chloramination of iodine containing waters in laboratory controlled reactions.

Iodine containing disinfection by-products (I-DBPs) and haloacetaldehydes (HALs) are emerging disinfection by-product (DBP) classes of concern. The former due to its increased potential toxicity and the latter because it was found to be the third most relevant DBP class in mass in a U.S. nationwide drinking water study. These DBP classes have been scarcely investigated, and this work was performed to further explore their formation in drinking water under chlorination and chloramination scenarios. In order to do this, iodo-trihalomethanes (I-THMs), iodo-haloacetic acids (I-HAAs) and selected HALs (mono-HALs and di-HALs species, including iodoacetaldehyde) were investigated in DBP mixtures generated after chlorination and chloramination of different water matrices containing different levels of bromide and iodide in laboratory controlled reactions. Results confirmed the enhancement of I-DBP formation in the presence of monochloramine. While I-THMs and I-HAAs contributed almost equally to total I-DBP concentrations in chlorinated water, I-THMs contributed the most to total I-DBP levels in the case of chloraminated water. The most abundant and common I-THM species generated were bromochloroiodomethane, dichloroiodomethane, and chlorodiiodomethane. Iodoacetic acid and chloroiodoacetic acid contributed the most to the total I-HAA concentrations measured in the investigated disinfected water. As for the studied HALs, dihalogenated species were the compounds that predominantly formed under both investigated treatments.

Characterization of iodinated disinfection by-products in chlorinated and chloraminated waters using Orbitrap based gas chromatography-mass spectrometry.

Recent developments in gas chromatography (GC)-mass spectrometry (MS) have opened up the possibility to use the high resolution-accurate mass (HRAM) Orbitrap mass analyzer to further characterize the volatile and semivolatile fractions of environmental samples. This work describes the utilization of GC Orbitrap MS technology to characterize iodine-containing disinfection by-products (iodo-DBPs) in chlorinated and chloraminated DBP mixture concentrates. These DBP mixtures were generated in lab-scale disinfection reactions using Llobregat river water and solutions containing Nordic Lake natural organic matter (NOM). The DBPs generated were concentrated using XAD resins, and extracts obtained were analyzed in full scan mode with the GC Orbitrap MS. Integration of high resolution accurate mass information and fragment rationalization allowed the characterization of up to 11 different iodo-DBPs in the water extracts analyzed, including one new iodo-DBP reported for the first time. Overall, formation of iodo-DBPs was enhanced during chloramination reactions. As expected, NOM characteristics and iodide and bromide content of the tested waters affected the amount and type of iodo-DBPs generated.

Formation of nitrogenous disinfection by-products in 10 chlorinated and chloraminated drinking water supply systems.

The presence of nitrogenous disinfection by-products (N-DBPs) in drinking water supplies is a public health concern, particularly since some N-DBPs have been reported to be more toxic than the regulated trihalomethanes and haloacetic acids. In this paper, a comprehensive evaluation of the presence of N-DBPs in 10 drinking water supply systems in Western Australia is presented. A suite of 28 N-DBPs, including N-nitrosamines, haloacetonitriles (HANs), haloacetamides (HAAms) and halonitromethanes (HNMs), were measured and evaluated for relationships with bulk parameters in the waters before disinfection. A number of N-DBPs were frequently detected in disinfected waters, although at generally low concentrations (<10 ng/L for N-nitrosamines and <10 µg/L for other N-DBPs) and below health guideline values where they exist. While there were no clear relationships between N-DBP formation and organic nitrogen in the pre-disinfection water, N-DBP concentrations were significantly correlated with dissolved organic carbon (DOC) and ammonia, and these, in addition to high bromide in one of the waters, led to elevated concentrations of brominated HANs (26.6 µg/L of dibromoacetonitrile). There were significant differences in the occurrence of all classes of N-DBPs between chlorinated and chloraminated waters, except for HNMs, which were detected at relatively low concentrations in both water types. Trends observed in one large distribution system suggest that N-DBPs can continue to form or degrade within distribution systems, and redosing of disinfectant may cause further by-product formation.

Impact of pre-ozonation on disinfection by-product formation and speciation from chlor(am)ination of algal organic matter of Microcystis aeruginosa.

The increasing use of algal-impacted source waters is increasing concerns over exposure to disinfection byproducts (DBPs) in drinking water disinfection, due to the higher concentrations of DBP precursors in these waters. The impact of pre-ozonation on the formation and speciation of DBPs during subsequent chlorination and chloramination of algal organic matter (AOM), including extracellular organic matter (EOM) and intracellular organic matter (IOM), was investigated. During subsequent chlorination, ozonation pretreatment reduced the formation of haloacetonitriles from EOM, but increased the yields of trihalomethanes, dihaloacetic acid and trichloronitromethane from both EOM and IOM. While in chloramination, pre-ozonation remarkably enhanced the yields of several carbonaceous DBPs from IOM, and significantly minimized the nitrogenous DBP precursors. Also, the yield of 1,1-dichloro-2-propanone from IOM was decreased by 24.0% after pre-ozonation during chloramination. Both increases and decreases in the bromine substitution factors (BSF) of AOM were observed with ozone pretreatment at the low bromide level (50µg/L). However, pre-ozonation played little impact on the bromide substitution in DBPs at the high bromide level (500µg/L). This information was used to guide the design and practical operation of pre-ozonation in drinking water treatment plants using algae-rich waters.

Formation and speciation of disinfection byproducts during chlor(am)ination of aquarium seawater.

The chemistry associated with the disinfection of aquarium seawater is more complicated than that of freshwater, therefore limited information is available on the formation and speciation of disinfection byproducts (DBPs) in marine aquaria. In this study, the effects of organic precursors, bromide (Br-) and pre-ozonation on the formation and speciation of several typical classes of DBPs, including trihalomethanes (THM4), haloacetic acids (HAAs), iodinated trihalomethanes (I-THMs), and haloacetamides (HAcAms), were investigated during the chlorination/chloramination of aquarium seawater. Results indicate that with an increase in dissolved organic carbon concentration from 4.5 to 9.4 mg/L, the concentrations of THM4 and HAAs increased by 3.2-7.8 times under chlorination and by 1.1-2.3 times under chloramination. An increase in Br- concentration from 3 to 68 mg/L generally enhanced the formation of THM4, I-THMs and HAcAms and increased the bromine substitution factors of all studied DBPs as well, whereas it impacted insignificantly on the yield of HAAs. Pre-ozonation with 1 mg/L O3 dose substantially reduced the formation of all studied DBPs in the subsequent chlorination and I-THMs in the subsequent chloramination. Because chloramination produces much lower amounts of DBPs than chlorination, it tends to be more suitable for disinfection of aquarium seawater.

Influencing factors of disinfection byproducts formation during chloramination of Cyclops metabolite solutions.

Effects of reaction time, chlorine dosage, pH and temperature on the formation of disinfection byproducts (DBPs), were investigated during the chloramination of Cyclops metabolite solutions. The results showed that some species of DBPs like trichloromethane (TCM), dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) could accumulate to their respective stable values with a progressive elevation in reaction time and monochloramine concentration. And 1,1,1-2-trichloropropanone (1,1,1-TCP) content decreased correspondingly with a continuous increase of reaction time. The amounts of chloral hydrate (CH), chloropicrin (TCNM), 1,1,1-TCP and DCAA firstly increased and then decreased with increasing monochloramine doses. Higher temperature resulted in a decrease of CH, dichloroacetonitrile (DCAN), 1,1-dichloropropanone (1,1-DCP), 1,1,1-TCP, DCAA and TCAA concentration. pH affected the formation of the different DBPs distinctly. TCM accumulateded with the increase of pH under 9, and DCAA, TCAA, CH and 1,1-DCP decreased continuously with increasing pH from 5 to 10, and other DBPs had the maximum concentrations at pH 6-7.