Studies of the halogenation of dissolved organic material during the chlorination of saline cooling waters, using the model compound resorcinol

When resorcinol is chlorinated in seawater, the variety of reaction products formed is controlled by competing equilibria involving chlorination of the resorcinol and conversion of oxidising species to hypobromous acid by exchange with naturally occurring bromide. When bromide is present in a molar excess over added chlorine, chlorination of resorcinol is only favoured under high pH conditions; under more acid conditions however, bromination occurs at the expense of chlorination. Increasing chlorine levels leads to ring cleavage and the production of trihalomethanes (haloforms).     

Effect of some parameters on the formation of chloroform during chloramination of aqueous solutions of resorcinol

The effects of various factors (N/Cl ratio used to prepare monochloramine, monochloramine doses, pH and contact time) on the monochloramine demand and on the chloroform yield during chloramination of resorcinol have been investigated. Chloramination experiments were carried out at 24 ± 1 °C, at pH values ranging from 6.5 to 12 using a bicarbonate/carbonate buffer and preformed monochloramine solutions prepared at pH 8.5 with N/Cl ratios ([NH₄Cl]₀/[Total free Cl₂]₀ ranging from 1.0 to 150 mol/mol). Kinetic experiments ([Resorcinol]₀ = 5 or 100 μM, [NH₂Cl]₀/[Resorcinol]₀ = 20 mol/mol, pH = 8.5 ± 0.1) showed a slow increase of the monochloramine consumption with reaction time. The monochloramine demands after reaction times of 7 days ([Resorcinol]₀ = 100 μM) and 14 days ([Resorcinol]₀ = 5 μM) were equal to 8.5 mol of NH₂Cl/mole of resorcinol and were higher than the chlorine demands (≈7.3 mol/mol). Chloroform yields from monochloramination of resorcinol were lower than 8% (<80 mmol of CHCl₃/mole of resorcinol) and were less than the yields obtained by chlorination (0.9-0.95 mol/mol). Chloroform productions increased with increasing monochloramine dose and reaction time and decreased with increasing pH values within the pH range 6.5-10. Chloroform formation markedly decreased when the N/Cl ratio increased from 1 to 1.5 mol/mol and was suppressed at N/Cl > 100 mol/mol. The data obtained in the present work suggest that free chlorine released from monochloramine hydrolysis plays a significant role on the formation of chloroform during chloramination of resorcinol at N/Cl ratios close to unity (1.0 < N/Cl < 1.5).     

The formation of stable organic chloramines during the aqueous chlorination of cytosine and 5-methylcytosine

The interaction of aqueous hypochlorous acid with the aminopyrimidines, cytosine and 5-methylcytosine has been investigated. Analysis of the reaction mixtures indicated substantial formation of chlorine substitution and addition products with little reduction of chlorine to chloride. Very high levels of combined chlorine were observed. Ultraviolet spectra showed complex patterns of behaviour with peak shifts and intensity changes occurring in some cases and full loss of aromaticity in others. The latter process was suggestive of addition of HOCl to double bonds with formation of chlorohydrins. The behaviour was found to depend on reaction pH and chlorine to base ratios. Thin layer chromatography revealed complex patterns of stable chloramine formation with the reaction mixture complexity tending to increase with increasing pH and FAC/base ratios. Chemical ionization mass spectra disclosed the existence of a number of organic chloramines containing up to three chlorine atoms and, in the case of 5-methylcytosine a major ring cleavage and rearrangement product of as yet undefined structure. The half-life for the decay of the combined chlorine was found to be approx. 3.9 days and to be independent of precursor compound and pH.     

Etude physicochimique de la chloration de l'eau de mer artificielle contenant de l'azote ammoniacal

Chlorine added to ammonia-free sea-water gives rise to a fast and quantitative oxidation of bromide to hypobromite and hypobromous acid. However as ammonia nitrogen levels commonly found in coastal and estuarine sea-water are sufficiently high and thus not negligible compared to the chlorine dose introduced formation of monochloramine to compete with oxidation of bromine leading to bromamines. The relative importance of these two reactional pathways is estimated considering both bromine determination and study of the electron absorption spectra of chlorinated seawater. In order to avoid substitution reactions taking place in the presence of organic compounds, preliminary experiments have been carried out in artificial and u.v. photo-oxidized sea-water.The nature of the species formed depends on the molar ratio added chlorine vs ammonia-nitrogen concentration of seawater. With Cl/N larger than 1.5, only bromide derivatives are obtained: dibromamine, tribromamine and bromine(I) (HBrO + BrO⁻). Cl/N smaller than 1.5 leads to a mixture of monochloramine, dibromamine and some monobromamine: monochloramine clearly predominates when ammonium concentrations reach higher values. Stoichiometry of ammonia to nitrogen oxidation by chlorine explains this ratio of 1.5 and a strong decrease of the total oxidant concentration is observed under these conditions. Bromamines decompose within the following 30–60 min; only stable compounds remain: either bromine(I) or monochloramine according to Cl/N values. A similar behaviour is observed in natural seawater previously doped with ammonia as to the nature of the products formed for a given Cl/N ratio; however, bromamines decompose more rapidly due to bromination of organic components.     

Transformation of dissolved organic matter during ozonation: effects on trihalomethane formation potential

Transformation of dissolved organic matter (DOM) during ozonation results in a higher reduction in trihalomethane formation potential (THMFP) relative to dissolved organic carbon (DOC). This study was conducted to determine the effect of DOM transformation after ozonation on THM formation and to elucidate the difference in THMFP and DOC removal. Changes in DOC, THMFP, reactivities of the hydrophilic and hydrophobic DOC, and phenolic-OH were determined to explain the difference in THMFP and DOC removal after ozonation. Higher reduction in THMFP (24-46%) relative to DOC (10-16%) was obtained and was attributed to the following: transformation of DOM from a more reactive hydrophobic DOC (microg THM produced per mg organic carbon) to a less reactive hydrophilic DOC and to the decrease in the reactivities of both the hydrophobic and hydrophilic DOC after ozonation. The results also showed decrease in phenolic-OH indicating the oxidation of some reactive sites like resorcinol or meta-dihydroxy benzene ring structures, which are prone to chlorine substitution, consequently decreasing the reactivity of the organic carbon to form THM. These changes in DOM led to a significant decrease in THMFP with no remarkable removal in DOC.     

Chloration de composés organiques: demande en chlore et réactivite vis-a-vis de la formation des trihalométhanes. Incidence de l'azote ammoniacalChlorination of organic compounds: Chlorine demand and reactivity in relationship to the trihalomethane formation. Incidence of ammoniacal nitrogen

The purpose of this work is to contribute to knowledge of the condition of formation of volatile and non-volatile organochlorinated compounds during surface water chlorination. With this aim in view, the chlorination of a number of organic substances in diluted aqueous solutions (10⁻⁶-10⁻⁵ moll ⁻¹) and in a neutral medium was studied. Special attention was given to their reactivity in relation to the formation of trihalomethanes.The results obtained show great differences in the reactivity of chlorine towards chemical substances liable to be present in the waters. The high chlorine demands, 5–12 mol of chlorine per mol of compound after a 15 h reaction at pH 7, where obtained with those aromatic compounds having activating groups such as — OH and — NR₂ (phenol and aniline derivatives). On the other hand, a number of compounds (alipahitcs in general; acids, aldehydes, alcohols…) are relatively inert towards chlorination.As far as chloroform production is concerned, the study shows that many organic compounds are liable to lead to the production of low quantities of chloroform in a neutral medium (molar yields < 5%). However, only a few specific structures such as metapolyhydroxybenzenes and metachlorophenols constitute good precursors of the haloform reaction.The study of the formation kinetics of chloroform, carried out with some precursors of different reactivity: acetone, acetylacetone, resorcinol, phloroglucinol and 3,5-dichlorophenol allowed us to determine the kinetic constants of chloroform formation at pH 7.5 and 20° C:

The results obtained during this work also show that the chlorine found in the chloroform produced from a precursor, represents only a small proportion of the chlorine demand. Even with a highly reactive precursor such as resorcinol. It was shown that the liberation of chloroform is accompanied by the formation of trichloroacetic acid (molar yield < 10%) and of monochloromaleic acid (molar yield 60%). Moreover, tetrahalogenated and pentahalogenated hydrocarbons (C₃Cl₄ and C₃ HCl₅) resulting from 3,5 -dichlorophenol chlorination were made manifest. As for the chlorin- ation of acetylacetone, a mechanism passing through the formation of 1,1-tri- chloroacetone was proposed.Lastly, in the general framework of the interactions between chlorine, ammonia nitrogen and the organic compounds which are frequently found in surface water chlorination, the study allowed us to show that the chlorination of highly reactive precursors (such as metapolyhydroxybenzenes and metachlorophenols) can lead to the production of important amounts of chloroform before reaching breakpoint. These results compared to the values of the velocities of the various reactions between chlorine and the ammoniacal compounds.     

Chloroform production from model compounds of aquatic humic material the role of pentachlororesorcinol as an intermediate

The chlorination of pentachlororesorcinol was studied in view of its postulated role as an intermediate in the chlorination of resorcinol. Chlorination of resorcinol and pentachlororesorcinol produced several identical products, but the large differences in reaction rate, chloroform production, and products formed, point to a minor role of pentachlororesorcinol.     

Catalysis of copper corrosion products on chlorine decay and HAA formation in simulated distribution systems

This study investigated the effect of copper corrosion products, including Cu(II), Cu₂O, CuO and Cu₂(OH)₂CO₃, on chlorine degradation, HAA formation, and HAA speciation under controlled experimental conditions. Chlorine decay and HAA formation were significantly enhanced in the presence of copper with the extent of copper catalysis being affected by the solution pH and the concentration of copper corrosion products. Accelerated chlorine decay and increased HAA formation were observed at pH 8.6 in the presence of 1.0 mg/L Cu(II) compared with that observed at pH 6.6 and pH 7.6. Further investigation of chlorine decay in the presence of both Suwannee River NOM and Cu(II) indicated that an increased reactivity of NOM with dissolved and/or solid surface-associated Cu(II), rather than chlorine auto-decomposition, was a primary reason for the observed rapid chlorine decay. Copper corrosion solids [Cu₂O, CuO, Cu₂(OH)₂CO₃] exhibited catalytic effects on both chlorine decay and HAA formation. Contrary to the results observed when in the absence of copper corrosion products, DCAA formation was consistently predominant over other HAA species in the presence of copper corrosion products, especially at neutral and high pH. This study improves the understanding for water utilities and households regarding chlorine residuals and HAA concentrations in distribution systems, in particular once the water reaches domestic plumbing where copper is widely used.     

聚羧酸减水剂在海工混凝土工程中的应用

通过聚羧酸减水剂在海工混凝土工程中的试验及应用,说明掺用聚羧酸类减水剂的混凝土,具有较高的致密结构和优良的耐久性能,大大提高混凝土的抗海水侵蚀性能与氯离子渗透性能.     

Model studies in aqueous chlorination: The chlorination of phenols in dilute aqueous solutions

A study of the chlorination of four phenols in dilute aqueous solution at initial pH's of 6.0 and 3.5 is described. Extensive chlorination is observed under these mild reaction conditions. Identification of the products indicates that the reactions occurring involve chlorination to more highly chlorinated phenols, oxidation to chlorinated p-benzoquinones, chlorine addition to the aromatic ring to form chlorinated 2,5-cyclohexadienones, and addition of 2 moles of chlorine or one each of chlorine and hypochlorous acid to give chlorinated cyclohexenones and chlorinated hydroxycyclohexenones.     

The effects of active chlorine on photooxidation of 2-methyl-2-butene

Active chlorine comprising hypochlorite (OCl⁻), hypochlorous acid (HOCl) and chlorine (Cl₂) is the active constituent in bleach formulations for a variety of industrial and consumer applications. However, the strong oxidative reactivity of active chlorine can cause adverse effects on both human health and the environment. In this study, aerosolized Oxone® [2KHSO₅, KHSO₄, K₂SO₄] with saline solution has been utilized to produce active chlorine (HOCl and Cl₂). To investigate the impact of active chlorine on volatile organic compound (VOC) oxidation, 2-methyl-2-butene (MB) was photoirradiated in the presence of active chlorine using a 2-m³ Teflon film indoor chamber. The resulting carbonyl products produced from photooxidation of MB were derivatized with O-(2,3,4,5,6-pentafluorobenzyl) hydroxyamine hydrochloride (PFBHA) and analyzed using gas chromatograph-ion trap mass spectrometer (GC/ITMS). The photooxidation of MB in the presence of active chlorine was simulated with an explicit kinetic model using a chemical solver (Morpho) which included both Master Chemical Mechanism (MCM) and Cl radical reactions. The reaction rate constants of a Cl radical with MB and its oxidized products were estimated using a Structure-Reactivity Relationship method. Under dark conditions no effect of active chlorine on MB oxidation was apparent, whereas under simulated daylight conditions (UV irradiation) rapid MB oxidation was observed due to photo-dissociation of active chlorine. The model simulation agrees with chamber data showing rapid production of oxygenated products that are characterized using GC/ITMS. Ozone formation was enhanced when MB was oxidized in the presence of irradiated active chlorine and NO_x.     

Solar driven production of toxic halogenated and nitroaromatic compounds in natural seawater

Natural seawater (NSW) sampled in March and June 2007 in the Gulf of Trieste, Italy, has been spiked with phenol and irradiated in a device simulating solar light spectrum and intensity. Opposite to the case of artificial seawater, for which phenol is slightly degraded by direct photolysis, in NSW the phenol degradation mediated by natural photosensitizers occurs, forming several secondary pollutants, including hydroxyderivatives (1,4-benzoquinone, resorcinol), three chlorophenol isomers, 2,3-dichlorophenol, 2- and 4-bromophenol, 2- and 4-nitrophenol, and several condensed products (2 and 4-phenoxyphenol, 2,2'-, 4,4'- and 2,4-bisphenol). These compounds are toxic to bacteria and other living organisms. Ecotoxicologic effect has been evaluated by using the Vibrio Fischeri luminescent bacteria assay. This technique uses marine organisms, and it is therefore well suited for the study on marine samples. A correlation exists between the intermediates evolution and the toxicity profile, as the largest toxicity is observed when compounds with the lower EC50 (halophenols, phenoxyphenols) are formed at higher concentration.     

Chlorination studies of free and combined amino acids

Nitrogenous organic compounds in raw and treated water are of concern because they may exert high chlorine demand. They are also known as precursors of halogenated compounds. In this study, chlorine demand, TOX and THM formation potentials of 22 free amino acids, and some polypeptides and proteins were determined. Results have shown that the reactivity of free amino acids with chlorine is related to their structure. Experiments conducted with combined amino acids have shown that the amide linkage does not participate significantly in the chlorine demand of polypeptides, and does not seem to be TOX precursor. Specific amino acids that possess reactive side groups such as amino nitrogen, sulfur or activated aromatic ring were defined as the main chlorine consumer and TOX precursor sites of polypeptides. Complementary experiments indicated that sodium sulfite dechlorination can affect, more or less, the determination of amino acids TOXFP.     

Dissolved organic matter and the dissipation of chlorine in estuarine water and seawater

Dissolved organic matter in estuarine water and seawater collected in the summers of 1980 and 1981 in the James River, Virginia and the mouth of Chesapeake Bay were separated into fractions according to their nominal molecular weights (NMW) by ultrafiltration. Estuarine waters contained higher concentrations of dissolved organic carbon (DOC). Among the fractions, between 66–89% of the DOC was found in the fraction with NMW below 10,000. Estuarine waters also had higher chlorine demands. At a dose of 5 mg l⁻¹, in 23 h, about 90% of the added chlorine disappeared in estuarine waters, whereas, in seawater, only 60–75% of the chlorine had dissipated. At least two-thirds of the chlorine demand occurred in the first 5 h. About 10–30% of the chlorine demand may be attributed to the fraction with NMW above 10,000. The remaining chlorine demand was distributed almost equally between the fractions with ranges of NMW of 1000–10,000 and below 1000. If reactivity is measured in terms of organic chlorine demand (ΔClo) per unit weight of DOC, the fractions with lower NMW (< 1000 and 1000–10,000) always had a higher reactivity towards chlorine. Between these two fractions, the one with NMW between 1000 and 10,000 exhibited higher reactivity more frequently. The highest reactivity found was 1.4 mg ΔClo mg⁻¹ DOC.     

Naproxen removal from water by chlorination and biofilm processes

Naproxen is an anti-inflammatory pharmaceutical that has been detected in natural and engineered aquatic environments. The primary aim of this research was to study chemical transformations of naproxen following chlorine oxidation, which is common in water and wastewater treatment systems. Synthetic waters containing elevated concentrations of naproxen were oxidized by free chlorine at naproxen:chlorine molar ratios of 0.02-3:1 and pH values of 5-9. The formation of naproxen products was dependent on pH, chlorine dosage and contact time. This study demonstrates that naproxen readily reacts with free chlorine and forms disinfection products. The formation of specific reaction products can vary depending on the characteristics of the water or wastewater and treatment operating conditions. More research is needed to identify intermediate and chemical reaction end products and to understand the reaction kinetics of naproxen chlorination for a range of water and wastewater treatment conditions. A secondary aim of this research was to study effects of naproxen and its chlorination products on biofilm processes, which are common in water and wastewater treatment systems and natural aquatic environments. A bioreactor was fed a naproxen solution and then fed a solution at the same naproxen concentration following contact with free chlorine. Results indicate that naproxen was not degraded biologically for the conditions of this study. In contrast, the naproxen solution containing products of chlorination caused an adverse response by discharging biomass from the bioreactor. Results therefore demonstrate that naproxen products of chlorination can adversely affect a biofilm process, which potentially can impact the performance of biofilm processes in natural and engineered aquatic environments. More research is needed to study naproxen chlorination reactions at low concentrations and in complex matrices, and to understand the toxicological relevance of naproxen and its products of chlorination in natural and engineered aquatic environments.     

Exposure levels to brominated compounds in seawater swimming pools treated with chlorine

Despite evidence of formation of brominated compounds in seawater swimming pools treated with chlorine, no data about exposure levels to these compounds have been reported. To address this issue, a survey has been carried out in four establishments (representing 8 pools) fed with seawater and devoted to relaxing and cure treatments (thalassotherapy centres located in Southeast of France). Carcinogenic and mutagenic brominated disinfection byproducts (trihalomethanes -THM- and halogenated acetic acids -HAA-) were quantified at varying levels, statistically related to organic loadings brought by bathers, and not from marine organic matter, and also linked to activities carried out in the pools (watergym vs swimming). Bromoform and dibromoacetic acid, the most abundant THM and HAA detected, were measured at levels up to 18-fold greater than the maximum contaminant levels of 60 and 80 μg/L fixed by US.EPA in drinking waters. The correlations between these disinfection byproducts and other environmental factors such as nitrogen, pH, temperature, free residual chlorine, UV₂₅₄, chloride and bromide concentrations, and daily frequentation were examined. Because thalassotherapy and seawater swimming pools (hotels, cruise ships,…) are increasing in use around the world and because carcinogenic and mutagenic brominated byproducts may be produced in chlorinated seawater swimming pools, specific care should be taken to assure cleanliness of users (swimmers and patients taking the waters) and to increase water circulation through media filters to reduce levels of brominated byproducts.     

Combined toxicity of free chlorine, chloramine and temperature to stage I larvae of the American lobster Homarus americanus

The differential effects of free chlorine and chloramine on stage I larvae of the American lobster Homarus americanus have been investigated in continuous flow bioassay units. Applied chloramine was more toxic than corresponding concentrations of applied free chlorine to lobster larvae with estimated lc₅₀ values at 25° of 16.30 mg/l applied free chlorine and 2.02 mg/l applied chloramine. The synergistic effect of temperature on the toxicity of both free chlorine and chloramine has also been demonstrated. Exposure to applied free chlorine at 20° resulted in no significant mortality of test organisms, whereas exposure at 30° resulted in an estimated lc₅₀ value of 2.50 mg/l. Applied chloramine was considerably more toxic with an estimated lc₅₀ value at 20° of 4.08 mg/l and at 30° of 0.56 mg/l.The action of each toxicant appeared to be an alteration of standard metabolic activity as revealed by changes in respiration rates during and after exposure to applied free chlorine and chloramine. Initial respiratory stress was detected during exposure to 0.05 mg/l applied chloramine and 5.00 mg/l applied free chlorine. Reductions in respiration rates 48 h after exposure were observed with exposure to all concentrations tested, similar results being obtained following exposure to 0.05 mg/l applied chloramine and 0.10 mg/l applied free chlorine. These results are indicative of the need for information in addition to that obtained in standard bioassays for an adequate assessment of chlorine toxicity.The apparent chlorine demand of the seawater used in this study was determined after removal of particulate and dissolved organics and ammonia. Approximately 18% of the applied level of free chlorine and chloramine was recovered as residuals, measured by amperometric titration; however, no reason for this low recovery has been determined. Until it has been established that undetected chlorine and chloramine in seawater do not result in the production of toxic compounds, both applied and residual levels should be reported in toxicity studies.     

顺序氯化消毒控制卫生学指标的效果

开发了一种短时游离氯消毒后加氨转化为氯胺的顺序氯化消毒工艺,该工艺可充分利用游离氯灭活微生物迅速彻底、氯胺生成消毒副产物少的优势,安全经济地实现对微生物指标的双重控制。在天津市某水厂的中试表明,该消毒工艺对细菌总数、总大肠菌群的控制效果略好于单纯游离氯消毒,说明游离氯和氯胺可能因为攻击位点不同而存在一定程度的协同效应。     

Using Bayesian statistics to estimate the coefficients of a two- component second-order chlorine bulk decay model for a water distribution system

Most chlorine decay models for the bulk phase in a water distribution system consider only chlorine concentration and time. Clark [1998. Chlorine demand and trihalomethane formation kinetics: a second-order model. J. Environ. Eng. 124(1), 16-24] first proposed a two-component second-order chlorine decay model based on the concept of competing reacting substances. A corrected mathematical formulation is developed and, because the recent findings suggested that not all natural organic matter (NOM) is involved in the chlorine decay process, an additional parameter is introduced. A parameter assignment method employing Bayesian statistical analysis incorporating Monte Carlo Markov chain (MCMC) with Gibbs sampling to make inferences, is employed in the estimation of model parameters. Three parameters are estimated for the model, namely the ratio of chlorine to TOC, the chlorine reaction rate, and a fraction factor of TOC which represents the true amount of TOC involved in chlorine decay process. Water samples taken from Goderich in the summer of 2005, are used for estimating the parameters.     

Effects of activated carbon on the reactions of combined chlorine with phenols

In the presence of ammonia, prechlorination in drinking water treatment results in contact of combined chlorine (monochloramine) with activated carbon, which is used to remove organic compounds from water. Monochloramine reacts very slowly with phenolic compounds in aqueous solution, giving low yields of chlorinated phenols. When monochloramine reacts with phenols adsorbed on granular activated carbon (GAC), however, several oxidized products, principally hydroxylated biphenyls, are formed. Some of the hydroxylated biphenyls are chlorinated (hydroxylated PCBs). Their formation is particularly important because of their potential toxicity. Such compounds are major reaction products from chlorophenol, but they are also formed in small amounts from nonchlorinated phenols. Most of the monochloramine-GAC-phenolic compound reaction products are also produced in similar reactions with free chlorine, indicating that similar reaction mechanisms (free radical mechanisms) take place on carbon's surface. No organic compounds are produced from the reaction of monochloramine with GAC alone.