Kinetics of aqueous chlorination of some pharmaceuticals and their elimination from water matrices

Apparent rate constants for the reactions of four selected pharmaceutical compounds (metoprolol, naproxen, amoxicillin, and phenacetin) with chlorine in ultra-pure (UP) water were determined as a function of the pH. It was found that amoxicillin (in the whole pH range 3-12), and naproxen (in the low pH range 2-4) presented high reaction rates, while naproxen (in the pH range 5-9), and phenacetin and metoprolol (in the pH range 2.5-12 for phenacetin, and 3-10 for metoprolol) followed intermediate and slow reaction rates. A mechanism is proposed for the chlorination reaction, which allowed the evaluation of the intrinsic rate constants for the elementary reactions of the ionized and un-ionized species of each selected pharmaceutical with chlorine. An excellent agreement is obtained between experimental and calculated rate constants by this mechanism.The elimination of these substances in several waters (a groundwater, a surface water from a public reservoir, and two effluents from municipal wastewater treatment plants) was also investigated at neutral pH. The efficiency of the chlorination process with respect to the pharmaceuticals elimination and the formation THMs was also established. It is generally observed that the increasing presence of organic and inorganic matter in the water matrices demand more oxidant agent (chlorine), and therefore, less chlorine is available for the oxidation of these compounds. Finally, half-life times and oxidant exposures (CT) required for the removal of 99% of the four pharmaceuticals are also evaluated. These parameters are useful for the establishment of safety chlorine doses in oxidation or disinfection stages of pharmaceuticals in treatment plants.     

Transformation mechanism of benzophenone-4 in free chlorine promoted chlorination disinfection

The UV-filter BP-4 (2-hydroxy-4-methoxybenzophenone-5-sulfonic acid) has been frequently observed in the environment, showing high potentials to invade drinking water, swimming water, or wastewater reclamation treatment systems. With the help of high performance liquid chromatography-high resolution mass spectrometry and nuclear magnetic resonance spectroscopy, 10 new products from free chlorine-promoted BP-4 disinfection have been disclosed and their possible transformation routes have been investigated. The first route is chlorine substitution of BP-4 and its transformation products, forming mono-, di-, and tri-chlorinated BP-4 analogs. The second is Baeyer–Villiger-Type oxidation, converting diphenyl ketone to phenyl ester derivatives. The third is ester hydrolysis, generating corresponding phenolic and benzoic products. The fourth is decarboxylation, replacing the carboxyl group by chloride in the benzoic-type intermediate. The fifth is desulfonation, degrading the sulfonic group through an alternative chlorine substitution on the benzene ring. Orthogonal experiments have been established to investigate the species transformed from BP-4 at different pH values and free available chlorine (FAC) dosages. The reaction pathways are strongly dependent on pH conditions, while an excessive amount of FAC eliminates BP-4 to the smaller molecules. The initial transformation of BP-4 in chlorination system follows pseudo-first-order kinetics, and its half-lives ranged from 7.48 s to 1.26 × 10² s. More importantly, we have observed that the FAC-treated BP-4 aqueous solution might increase the genotoxic potentials due to the generation of chlorinated disinfection by-products.     

Aqueous chlorination of carbamazepine: Kinetic study and transformation product identification

Carbamazepine reactivity and fate during chlorination was investigated in this study. From a kinetic standpoint, a third-order reaction (first-order relative to the CBZ concentration and second-order relative to the free chlorine concentration) was observed at neutral and slightly acidic pH, whereas a second-order reaction (first order relative to the CBZ concentration and first order relative to the free chlorine concentration) was noted under alkaline conditions. In order to gain insight into the observed pH-dependence of the reaction order, elementary reactions (i.e. reactions of Cl₂, Cl₂O, HOCl with CBZ and of ClO⁻ with CBZ or of HOCl with the ionized form of CBZ) were highlighted and second order rate constants of each of them were calculated. Close correlations between the experimental and modeled values were obtained under these conditions. Cl₂ and Cl₂O were the main chlorination agents at neutral and acidic pH. These results indicate that, for a 1 mg/L free chlorine concentration and 1–10 mg/L chloride concentration at pH 7, halflives about 52–69 days can be expected. A low reactivity of chlorine with CBZ could thus occur under the chlorination steps used during water treatment. From a mechanistic viewpoint, several transformation products were observed during carbamazepine chlorination. As previously described for the chlorination of polynuclear aromatic or unsaturated compounds, we proposed monohydroxylated, epoxide, diols or chlorinated alcohol derivatives of CBZ for the chemical structures of these degradation products. Most of these compounds seem to accumulate in solution in the presence of excess chlorine.     

污水氯消毒过程中有机氯胺的生成及其影响

消毒是保证污水再生利用水质安全的必要措施，氯消毒是最常用的消毒方法。在氯消毒过程中，污水中的含氮有机物与氯反应会生成有毒有害的有机氯胺。国外很早就开始了对有机氯胺的研究，而国内对有机氯胺的关注较少。有机氯胺在一定条件下可以在自然水体中长时间稳定存在，部分有机氯胺在脱氯时不易被亚硫酸钠脱除。有机氯胺一般具有一定的生物毒性，而且一些有机氯胺也是致癌消毒副产物的前体物质，对水中的生物以及人体健康会产生毒害作用。消毒过程中有机氯胺的生成不仅会降低消毒效果，而且也会影响水体中余氯的测定。     

Identification of reaction products from reactions of free chlorine with the lipid-regulator gemfibrozil

High global consumption rates have led to the occurrence of pharmaceutically active compounds (PhACs) in wastewater. The use of chlorine to disinfect wastewater prior to release into the environment may convert PhACs into uncharacterized chlorinated by-products. In this investigation, chlorination of a common pharmaceutical, the antihyperlipidemic agent gemfibrozil, was documented. Gemfibrozil (2,2-dimethyl-5-(2,5-dimethylphenoxy)pentanoic acid) was reacted with sodium hypochlorite and product formation was monitored by gas chromatography-mass spectrometry (GC-MS). The incorporation of one, two or three chlorine atoms into the aromatic region of gemfibrozil was demonstrated using negative-ion electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry (ESI-MS/MS). Further analysis using ¹H nuclear magnetic resonance (NMR) spectroscopy identified the reaction products as 4′-ClGem (5-(4-chloro-2,5-dimethylphenoxy)-2,2-dimethylpentanoic acid) 4′,6′-diClGem (5-(4,6-dichloro-2,5-dimethylphenoxy)-2,2-dimethylpentanoic acid), and 3′,4′,6′-triClGem (5-(3,4,6-trichloro-2,5-dimethylphenoxy)-2,2-dimethylpentanoic acid), products consistent with electrophilic aromatic substitution reactions. The rapid reaction of gemfibrozil with free chlorine at pH conditions relevant to water treatment indicates that a mixture of chlorinated gemfibrozils is likely to be found in wastewater disinfected with chlorine.     

Investigating the chlorination of acidic pharmaceuticals and by-product formation aided by an experimental design methodology

The degradation of seven acidic drugs and two metabolites during chlorination was investigated by liquid chromatography-mass spectrometry (LC-MS). A triple-quadrupole (QqQ) system was used to follow the time course of the pharmaceuticals and by-products, while a quadrupole time-of-flight (Q-TOF) system was also used for the identification of the by-products. Under strong chlorination conditions (10 mg/L Cl₂, 24 h), only four of the target compounds were significantly degraded: salicylic acid, naproxen, diclofenac and indomethacine. The degradation kinetics of these four compounds were investigated at different concentrations of chlorine, bromide and pH by means of a Box-Behnken experimental design. Depending on these factors, measured pseudo-first order half-lives were in the ranges: 23-573 h for salicylic acid, 13-446 min for naproxen, 5-328 min for diclofenac and 0.4-13.4 min for indomethacine. Also, it was observed that chlorine concentration was the overall most significant factor, followed by the bromide concentration (except for indomethacine), resulting in increased degradation kinetics as they are increased. The degradation path of salicylic acid, naproxen and diclofenac consisted of aromatic substitution of one or two hydrogens by chlorine and/or bromide. Moreover, for diclofenac, two other by-products corresponding to a decarboxylation/hydroxylation pathway from the monohalogenated products were also identified. On the other hand, indomethacine degradation did not lead to halogenation products but to oxidation ones. The investigation of these by-products in real samples by LC-MS/MS (QqQ) showed that the halogenated derivates of salicylic acid occurred in all the drinking water and wastewater samples analysed.     

Determination of N-chloramines in As-samra chlorinated wastewater and their effect on the disinfection process

Chlorine is the most widely used disinfectant of wastewater due to its capacity to inactivate most pathogenic microorganisms quickly. However, chlorine reacts with natural organic compounds present in wastewater to produce some undesirable organic byproducts. One such class of compounds is the nitrogenous compounds. The reaction between chlorine and compounds containing a nitrogen atom with one or more hydrogen atoms attached to it will form chloramines which have lower disinfection efficiency. Eighty percent of the wastewater generated in Jordan is treated at the Khirbet As-Samra wastewater treatment plant for eventual use in agriculture. In this study efficiency of chlorination was studied by collecting samples from the effluent of the treatment plant. The yield concentration of N-chloramines upon chlorination was determined. Efficiency of disinfection process as a function of contact time, concentration of chlorine dosage, concentration of nitrogenous compound and pH were studied. In this study, it has been found that at a chlorine dosage of 15 mg/L and contact time of 15 min, the percentage total coliform kill in As-samra wastewater sample was 100%. After addition of histidine, glycine and phenylalanine (15 mg/L in each case) to the wastewater sample, the percentage of total coliform kill dropped to 58, 78 and 79% respectively. When chlorine dosage was increased to 24 mg/L the percentage total coliform kill reached 96, 99 and 100% in wastewater samples treated with 5 mg/L histidine, glycine and phenylalanine, respectively. The percentage total coliform kill dropped to zero in wastewater samples treated with histidine, glycine and phenylalanine at a concentration of 30 mg/L each. This work supports the theory that amino acids and ammonia preferentially react with chlorine to form N-chloramine which significantly reduces the disinfection efficiency of the chlorination process.     

Chlorination of model drinking water biofilm: implications for growth and organic carbon removal

The influence of chlorine on biofilm in low organic carbon environments typical of drinking water or industrial process water was examined by comparing biomass and kinetic parameters for biofilm growth in a chlorinated reactor to those in a non-chlorinated control. Mixed-population heterotrophic biofilms were developed in rotating annular reactors under low concentration, carbon-limited conditions (< 2 mg/L as carbon) using three substrate groups (amino acids, carbohydrates and humic substances). Reactors were operated in parallel under identical conditions with the exception that chlorine was added to one reactor at a dose sufficient to maintain a free chlorine residual of 0.09-0.15 mg/L in the effluent. The presence of free chlorine resulted in development of less biofilm biomass compared to the control for all substrates investigated. However, specific growth and organic carbon removal rates were on the average five times greater for chlorinated biofilm compared to the control. Observed yield values were less for chlorinated biofilm. Although chlorinated biofilm's specific organic carbon removal rate was high, the low observed yield indicated organic carbon was being utilized for purposes other than creating new cell biomass. The impacts of free chlorine on mixed-population biofilms in low-nutrient environments were different depending upon the available substrate. Biofilms grown using amino acids exhibited the least difference between control and chlorinated kinetic parameters; biofilm grown using carbohydrates had the greatest differences. These findings are particularly relevant to the fundamental kinetic parameters used in models of biofilm growth in piping systems that distribute chlorinated, low-carbon-concentration water.     

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.     

Chlorination kinetics of glyphosate and its by-products: modeling approach

Chlorination reactions of glyphosate, glycine, and sodium cyanate were conducted in well-agitated reactors to generate experimental kinetic measurements for the simulation of chlorination kinetics under the conditions of industrial water purification plants. The contribution of different by-products to the overall degradation of glyphosate during chlorination has been identified. The kinetic rate constants for the chlorination of glyphosate and its main degradation products were either obtained by calculation according to experimental data or taken from published literature. The fit of the kinetic constants with experimental data allowed us to predict consistently the concentration of the majority of the transitory and terminal chlorination products identified in the course of the glyphosate chlorination process. The simulation results conducted at varying aqueous chlorine/glyphosate molar ratios have shown that glyphosate is expected to degrade in fraction of a second under industrial aqueous chlorination conditions. Glyphosate chlorination products are not stable under the conditions of drinking water chlorination and are degraded to small molecules common to the degradation of amino acids and other naturally occurring substances in raw water. The kinetic studies of the chlorination reaction of glyphosate, together with calculations based on kinetic modeling in conditions close to those at real water treatment plants, confirm the reaction mechanism that we have previously suggested for glyphosate chlorination.     

Minimizing biofilm in the presence of iron oxides and humic substances

Based upon circumstantial evidence linking elevated coliform bacteria counts in drinking water distribution systems with unlined cast iron pipe, it was hypothesized that adsorption of humic substances by iron oxide containing corrosion products (CPs) can stimulate and/or support biofilm development. Using porous media consisting of iron-oxide-coated glass beads (IOCBs) or actual iron CPs, experiments were performed to evaluate the effectiveness of different corrosion control and disinfection treatments in reducing biofilm when humic substances were the carbon source. Free chlorine was the most effective treatment in minimizing biofilm. Addition of phosphate alone did not significantly reduce biofilm using the CPs, but there was weak evidence it did using the IOCBs. The combination of free chlorine and phosphate was more effective at minimizing biofilm than free chlorine alone when CPs were the media. The presence of humic substances was a major factor when considering biofilm minimization based on results of experiments using both types of iron oxide media. The combination of humic substances and CPs led to an increase in biofilm biomass when free chlorine was not present, similar to conditions that could occur at distribution system dead-ends. Treatment to raise the pH to 9 did not reduce biofilm in experiments using both media, and actually increased biofilm in the experiment using CPs under the conditions tested.     

Synergistic effect of the sequential use of UV irradiation and chlorine to disinfect reclaimed water

The effectiveness of UV and chlorination, used individually and sequentially, was investigated in killing pathogenic microorganisms and inhibiting the formation of disinfection by-products in two different municipal wastewaters for the source water of reclaimed water, which were from a microfilter (W1) and membrane bioreactor (W2) respectively. Heterotrophic plate count (HPC), total bacteria count (TBC), and total coliform (TC) were selected to evaluate the efficiency of different disinfection processes. UV inactivation of the three bacteria followed first-order kinetics in W1 wastewater, but in W2 wastewater, the UV dose-response curve trailed beyond approximately 10 mJ/cm² UV. The higher number of particles in the W2 might have protected the bacteria against UV damage, as UV light alone was not effective in killing HPC in W2 wastewater with higher turbidity. However, chlorine was more effective in W2 than in W1 for the three bacteria inactivation owing to the greater formation of inorganic and organic chloramines in W1 wastewater. Complete inactivation of HPC in W1 wastewater required a chlorine dose higher than 5.5 mg/L, whereas 4.5 mg/L chlorine gave the equivalent result in W2 wastewater. In contrast, sequential UV and chlorine treatment produced a synergistic effect in both wastewater systems and was the most effective option for complete removal of all three bacteria. UV disinfection lowered the required chlorine dose in W1, but not in W2, because of the higher chlorine consumption in W2 wastewater. However, UV irradiation decreased total trihalomethane formation during chlorination in both wastewaters.     

氯化消毒条件及污水水质对生成THMs、HAAs的影响

系统地研究了消毒务件和水质在城市污水氯化消毒过程中对生成三卤甲烷和卤乙酸的影响。结果表明，投氯量对三卤甲烷和卤乙酸生成量的影响最大，投氯量为40mg／L时的生成量分别约是投氯量为5mg／L时的30倍和70倍。三卤甲烷浓度随反应时间和温度无明显变化，而卤乙酸浓度在反应2h后达到峰值并在之后逐渐降低，且随温度的升高呈下降趋势。pH对两类副产物生成的影响几乎相反，近中性条件下的三卤甲烷生成量最多而卤乙酸生成量最少。水中氨氮浓度的增加会导致三卤甲烷生成量略有下降，而卤乙酸浓度却大幅上升。溴离子浓度升高将导致三卤甲烷和卤乙酸生成量显著增加，其中三氯甲烷浓度下降，三溴甲烷浓度显著上升，混合取代的三卤甲烷浓度先增加后减少。与此类似，二氯乙酸和三氯乙酸浓度随溴离子浓度的增加而减少，含溴卤乙酸浓度则有不同程度的增加。反应温度、反应时间、pH和氨氮对污水消毒副产物生成的影响与已报道的饮用水消毒中的作用规律存在显著差异，甚至截然相反，这为有针对性地选取消毒工艺参数提供了依据。     

Aqueous chlorination of diclofenac: kinetic study and transformation products identification

Diclofenac reactivity and fate during water chlorination was investigated in this work. In the first step, chlorination kinetic of diclofenac (DCF) was studied in the pH range of 4-10 at 20 ± 2 °C and in the presence of an excess of total chlorine. A second-order reaction (first-order relative to DCF concentration and first-order relative to free chlorine concentration) was shown with rate constant about 3.89 ± 1.17 M⁻¹ s⁻¹ at pH 7. The elementary reactions (i.e. reactions of hypochlorous acid (HOCl) with neutral and ionized forms of DCF, and acid-catalysed reaction of HOCl with neutral and ionized forms of DCF) were proposed to explain the pH-dependence of the rate constants and intrinsic constant of each of them were calculated. In the second step, several degradation products formed during chlorination of DCF were identified. These compounds could come from an initial chlorine electrophilic attack on aromatic ring or amine function of DCF. Some of these chlorinated derivatives seem to accumulate in solution in the presence of an excess of chlorine.     

Aqueous chlorination of the antibacterial agent trimethoprim: reaction kinetics and pathways

Trimethoprim (TMP), one of the antibacterials most frequently detected in municipal wastewaters and surface waters, reacts readily with free available chlorine (i.e., HOCl) at pH values between 3 and 9 (e.g., the pH-dependent apparent second-order rate constant, k'(app)=5.6 x 10(1)M(-1)s(-1), at pH 7). Solution pH significantly affects the rate of TMP reaction with HOCl. The reaction kinetics in reagent water systems can be well described by a second-order kinetic model incorporating speciation of both reactants and accounting for acid-mediated halogenation of TMP's 3,4,5-trimethoxybenzyl moiety. Studies with the substructure model compounds 2,4-diamino-5-methylpyrimidine and 3,4,5-trimethoxytoluene show that TMP reacts with HOCl primarily via its 3,4,5-trimethoxybenzyl moiety at acidic pH, and with its 2,4-diaminopyrimidinyl moiety at circumneutral and alkaline pH. LC/MS product analyses indicate that the TMP structure is not substantially degraded upon reactions with HOCl. Instead, a wide variety of (multi)chlorinated and hydroxylated products are formed. Experiments with real drinking water and wastewater matrixes confirmed that substantial TMP transformation can be expected for conditions typical of wastewater and drinking water chlorination.     

Pathways and metabolites of microbial degradation of selected acidic pharmaceutical and their occurrence in municipal wastewater treated by a membrane bioreactor

Laboratory degradation tests with five acidic pharmaceuticals using activated sludge as inocculum under aerobic conditions were performed and microbial metabolites were analysed by liquid chromatography-mass spectrometry (LC-MS). Ketoprofen was partly mineralized as a sole source of carbon and energy and the metabolites determined by LC-MS suggest microbial ketoprofen degradation to proceed along the pathway known for biphenyls and related compounds. Bezafibrate, naproxen and ibuprofen were degraded only cometabolically whereas no transformation was obtained for diclofenac. Some biodegradation intermediates in these batch tests could be tentatively identified by means of LC-MS. The first step in microbial bezafibrate degradation appears to be the hydrolytic cleavage of the amide bond, generating well degradable 4-chlorobenzoic acid as one of the hydrolysis products. As previously found for mammals, ether cleavage and formation of desmethylnaproxen was the initial step in microbial degradation of naproxen. Two isomers of hydroxy-ibuprofen were detected as intermediates in the mineralization of ibuprofen. Laboratory studies suggest that naproxen and ibuprofen can be fully mineralized whereas more stable metabolites occur in microbial ketoprofen and bezafibrate transformation, that may deserve further attention. A LC-MS method for the trace analysis of these metabolites in water was developed and applied to municipal wastewater. Municipal wastewater treatment by a membrane bioreactor may gradually improve the removal of these pharmaceuticals.     

Reaction of chlorine dioxide with emergent water pollutants: product study of the reaction of three beta-lactam antibiotics with ClO(2)

This work deals with the chlorine dioxide (ClO(2)) reactivity with three representative beta-lactam antibiotics (penicillin, amoxicillin and cefadroxil) that can be present in natural aquatic resources. Due to the wide use of ClO(2) as disinfection agent our work is of interest to determine the fate of these antibiotics during the water treatment process. Our study shows that antibiotics react stoichiometrically with ClO(2) because increasing amounts of ClO(2) lead to increasing antibiotic disappearance. Concerning the influence of antibiotic structure, penicillin reacts sluggishly with ClO(2), whereas amoxicillin and cefadroxil are highly reactive at either neutral or basic pH. For both reactive antibiotics, hydroquinone together with a wide range of 4-substituted phenols were detected as products. Pretreatment with ClO(2) before chlorination of aqueous solutions of antibiotics reduces the trihalomethane formation as compared with analogous chlorination without ClO(2) pretreatment.     

Cinetiques et mecanismes de la degradation de la creatinine sous l'action de l'hypochloriteKinetics and mechanisms of hypochlorite oxidation of creatinine

An area of substantial interest in current research on chlorination is the formation, stability and nature of chloramines formed by the interaction of chlorine with nitrogen organic compounds of biological origin in natural water or swimming pool water. It is desirable to be able to predict the lifetime of these harmful compounds under various conditions. The research described here constitutes an effort to gather important baseline data regarding the rate of formation of creatinine chloramines, the stabilities of these products and their identities.

Some researchers have studied the effect of the presence of chlorinated creatinine compounds in swimming pool water. Lomas (1967), showed that the presence of urine in water allowed the formation of compounds which reacted with DPD like dichloramine. He reported that the presence of this apparent dichloramine could be due to a chlorine derivative of creatine and creatinine derived from urine. Hamence (1980) confirmed this work and found that urine and particularly creatinine were responsible for the apparent nitrogen trichloride. As a result of this work it was concluded that the DPD-fast titrimetric method of analysis did not determine nitrogen trichloride but other chlorine compounds, particularly those of chlorinated creatinine and creatine. We found it interesting to examine in this study, for a range of hypochlorite creatinine ratios and pHs, the kinetics and mechanisms of formation and decomposition of N-chlorocreatinines.

The hypochlorite oxidation of creatinine in aqueous solution has been investigated in the dark. The following of creatinine and chloramines concentrations by the DPD-fast titrimetric method and by their u.v. spectra confirmed Lomas' and Hamence's works. However we observed dichloramine formation (Fig. 4) when the molar ratio of hypochlorite and creatinine was sufficient to decompose all chlorinated creatinine forms. The creatinine determination (HPLC method) suggested that N-chlorocreatinines were formed rapidly at an initial stage. Then they were decomposed by an apparent first order reaction at pH 8. With equimolar (1:1 mmol) amounts of hypochlorite and creatinine at pH 8, it appeared that N-chlorocreatinines were decomposed by hydrolysis to regenerate creatinine. We observed then the formation of creatine, 1-methylhydantoin, chlorocreatinines and NH₂Cl (Fig. 3). When the molar ratio was greater, the N-chlorocreatinines decomposed completely to form carbon dioxide, chlorite ion and mineral chloramines (see Table 1).

The reaction in the initial stage should be considered as an electrophile substitution followed slowly by hydrolysis when pH remained around 8 (Scheme 2). If the addition of hypochlorite affects the amine group of the molecule, 1-methylhydantoin is produced (Scheme 3) with NH₂Cl. Reaction yield was about 10% of initial creatinine.

In acid aqueous solution, with a molar ratio of 3, we also obtained trichlorocreatinine. This reaction is due to the various form of creatinine after addition of proton on amino of N-H groups of the molecule. In these conditions N-chlororcreatinines remained stable in aqueous solution for many days. However in the presence of free chlorine, we observed the production of carbon dioxide and mineral chloramines. After 4 days the residual concentration of N-chlorocreatinines was half the initial value.

It appears that N-chlorocreatinines formed during the chlorination of natural or swimming pool water were relatively stable, leading to the increase of the combined chlorine level. This stability was a function of the molar ratio of hypochlorite and creatinine, and pH. However, since most of the difference types of water had a pH in the range of 6–9, there would be little effect of pH at ambient temperature.     

Occurrence and production of chloramines in the chlorination of creatinine in aqueous solution

Occurrence and production of stable chloramines in the chlorination of creatinine, a constituent of perspiration and urine, in aqueous media were studied. Creatinine (5 x 10(-5)M) was treated with free chlorine in aqueous solutions at molar ratios of 0.5-8 (chlorine/creatinine) at pH 7.0 at room temperature for several days. At lower ratios of chlorine, two stable N-chlorocreatinine derivatives, which were determined as dichloramine fractions by the DPD method, were isolated by HPLC and identified by EI-MS and (1)H-NMR. One was 2-chloroamino-1-methylimidazolin-4-one (creatinine chloramine) and the other was 2-chloroamino-5-hydroxy-1-methylimidazolin-4-one (hydroxycreatinine chloramine). In addition, the formation of methylamine was identified by GC-MS analyses of its imine derivative formed with pentafluorobenzaldehyde. Methylamine forms stable chloramines, which might be determined as mono- and/or di-chloramine fractions together with free chlorine by the DPD method in the reaction mixtures at higher molar ratios of chlorine. In practice, small amounts of methylamine (ca. 19 microg/L) were detected in water samples collected from several swimming pools. Hence, methylamine may be an origin of elusive organic chloramine formed in the chlorination of swimming pools. A probable mechanism of the occurrence and processing of chlorination products of creatinine is suggested.