Trihalomethane exposures in indoor swimming pools: a level III fugacity model

The potential for generation of disinfection byproducts (DBPs) in swimming pools is high due to the concentrations of chlorine required to maintain adequate disinfection, and the presence of organics introduced by the swimmers. Health Canada set guidelines for trihalomethanes (THMs) in drinking water; however, no such guideline exists for swimming pool waters. Exposure occurs through ingestion, inhalation and dermal contact in swimming pools. In this research, a multimedia model is developed to evaluate exposure concentrations of THMs in the air and water of an indoor swimming pool. THM water concentration data were obtained from 15 indoor swimming pool facilities in Quebec (Canada). A level III fugacity model is used to estimate inhalation, dermal contact and ingestion exposure doses. The results of the proposed model will be useful to perform a human health risk assessment and develop risk management strategies including developing health-based guidelines for disinfection practices and the design of ventilation system for indoor swimming pools.     

Evaluation and improvement of total organic bromine analysis with respect to reductive property of activated carbon

A collective parameter and a toxicity indicator for all the halogenated organic disinfection byproducts in a water sample is total organic halogen (TOX), which can be differentiated as total organic chlorine (TOCl), total organic bromine (TOBr) and total organic iodine. The TOX method involves concentration of organic halogens from water by adsorption onto activated carbon (AC). A previous study showed that a portion of TOCl can be reduced to chloride during the adsorption procedure, which can be minimized by ozonation of the AC. In this study, a portion of TOBr was sometimes found to be reduced by AC to bromide, and the reduction was generally less than that of corresponding TOCl. The results suggested that around 10% of brominated Suwannee River fulvic acid was reduced to bromide. However, some brominated amino compounds (especially glycylglycine, phenylalanine, and cytosine) were found to be more reactive with the AC. For the iodinated compounds studied, the reduction to iodide was not significant. The method for the TOBr measurement was improved by using ozonated AC when reduction occurred on the original AC. The improved method was also evaluated on treated wastewater and swimming pool water samples.     

Formation of halogenated organic byproducts during medium-pressure UV and chlorine coexposure of model compounds, NOM and bromide

When chlorine is applied before or during UV disinfection of bromide-containing water, interactions between chlorine, bromide and UV light are inevitable. Formation of halogenated organic byproducts was studied during medium-pressure UV (MPUV) and chlorine coexposure of phenol, nitrobenzene and benzoic acid and maleic acid, chosen to represent electron-donating aromatics, electron-withdrawing aromatics, and aliphatic structures in natural organic matter (NOM), respectively. All were evaluated in the presence and absence of bromide. MPUV and chlorine coexposure of phenol produced less total organic halogen (TOX, a collective parameter for halogenated organic byproducts) than chlorination in the dark, and more haloacetic acids instead of halophenols. Increases in TOX were found in the coexposure of nitrobenzene and benzoic acid, but maleic acid was rather inert during coexposure. The presence of bromide increased the formation of brominated TOX but did not significantly affect total TOX formation, in spite of the fact that it reduced hydroxyl radical levels. MPUV and chlorine coexposure of NOM gave a higher differential UV absorbance of NOM and a larger shift to lower molecular weight compounds than chlorination in the dark. However, TOX formation with NOM remained similar to that observed from dark chlorination.     

Volatile disinfection by-product analysis from chlorinated indoor swimming pools

Chlorination of indoor swimming pools is practiced for disinfection and oxidation of reduced compounds that are introduced to water by swimmers. However, there is growing concern associated with formation for chlorinated disinfection by-products (DBPs) in these settings. Volatile DBPs are of particular concern because they may promote respiratory ailments and other adverse health effects among swimmers and patrons of indoor pool facilities. To examine the scope of this issue, water samples were collected from 11 pools over a 6 month period and analyzed for free chlorine and their volatile DBP content. Eleven volatile DBPs were identified: monochloramine (NH₂Cl), dichloramine (NHCl₂), trichloramine (NCl₃), chloroform (CHCl₃), bromoform (CHBr₃), dichlorobromomethane (CHBrCl₂), dibromochloromethane (CHBr₂Cl), cyanogen chloride (CNCl), cyanogen bromide (CNBr), dichloroacetonitrile (CNCHCl₂), and dichloromethylamine (CH₃NCl₂). Of these 11 DBPs, 10 were identified as regularly occurring, with CHBrCl₂ only appearing sporadically. Pool water samples were analyzed for residual chlorine compounds using the DPD colorimetric method and by membrane introduction mass spectrometry (MIMS). These two methods were chosen as complementary measures of residual chlorine, and to allow for comparisons between the methods. The DPD method was demonstrated to consistently overestimate inorganic chloramine content in swimming pools. Pairwise correlations among the measured volatile DBPs allowed identification of dichloromethylamine and dichloroacetonitrile as potential swimming pool water quality indicator compounds.     

The analysis of halogenated acetic acids in dutch drinking water

Halo-acetic acids are produced during chlorine disinfection of drinking water. Besides the well-known dichloro-, and trichloroacetic acid, brominated and mixed chloro/bromo acetic acids are also produced. A method was developed to determine all halo-acetic acids. This method was applied for the analysis of 20 drinking waters prepared from different source waters. Halo-acetic acids were found in all drinking waters prepared from surface water while they could not be detected in drinking waters prepared from ground water. The acid concentrations were in the range of 0–14.7 μg/l and dibromoacetic acid was found to be the most prominent halo-acetic acid in chlorinated waters. Brominated acetic acids accounted for 65% of the total acid concentration showing that brominated compounds form a large part of the chlorination products. The total halo-acetic acid concentration correlated positively with the chlorine-to-carbon ratio and with the adsorbable organic halogen, to which it accounted for 15%.     

Distribution and balance of volatile halogenated hydrocarbons in the water and air of covered swimming pools using chlorine for water disinfection

A survey of the “chlorination practice” of swimming-pool waters is presented taking the case of covered pools in Bremen. Chlorination of water may result in specific health hazards by various halogenated chemicals. Trihalomethanes (THMs), among others, are determined in water and air samples. We succeeded in identifying one organic “precursor” of the synthesis of THMs in swimming pools. An estimate of the average and maximum burden of the user/swimmer is given. Short and long range alternative measures are proposed to diminish the health hazards. We conclude from this work that the application of chlorine for disinfection should be minimized.     

Characteristics of trihalomethane (THM) production and associated health risk assessment in swimming pool waters treated with different disinfection methods

Swimming pool water must be treated to prevent infections caused by microbial pathogens. In Korea, the most commonly used disinfection methods include the application of chlorine, ozone/chlorine, and a technique that uses electrochemically generated mixed oxidants (EGMOs). The purpose of this study was to estimate the concentrations of total trihalomethanes (TTHMs) in indoor swimming pools adopting these disinfection methods, and to examine the correlations between the concentrations of THMs and TTHMs and other factors affecting the production of THMs. We also estimated the lifetime cancer risks associated with various exposure pathways by THMs in swimming pools. Water samples were collected from 183 indoor swimming pools in Seoul, Korea, and were analyzed for concentrations of each THM, TOC, and the amount of KMnO₄ consumption. The free chlorine residual and the pH of the pool water samples were also measured. The geometric mean concentrations of TTHMs in the swimming pool waters were 32.9 ± 2.4 µg/L for chlorine, 23.3 ± 2.2 µg/L for ozone/chlorine, and 58.2 ± 1.7 µg/L for EGMO. The concentrations of THMs differed significantly among the three treatment methods, and the correlation between THMs and TTHMs and the other factors influencing THMs varied. The lifetime cancer risk estimation showed that, while risks from oral ingestion and dermal exposure to THMs are mostly less than 10^− 6, which is the negligible risk level defined by the US EPA, however swimmers can be at the greater risk from inhalation exposure (7.77 × 10^− 4-1.36 × 10^− 3).     

城市污水再生水氯消毒副产物比较研究

比较分析了对城市污水再生水采用液氯和二氧化氯消毒前后消毒副产物的变化。结果表明:城市污水再生水本身含有少量的氯代有机物,经液氯消毒后二氯甲烷、三氯甲烷含量大幅增加,为进水的3～4倍,同时产生了新的消毒副产物二氯一溴甲烷;经二氧化氯消毒后未出现新的消毒副产物,且原有副产物浓度基本不变。因此,再生水使用二氧化氯消毒具有明显优势。     

Comparison of disinfection byproduct formation from chlorine and alternative disinfectants

Seven diverse natural waters were collected and treated in the laboratory under five oxidation scenarios (chlorine, chloramine, both with and without preozonation, and chlorine dioxide). The impact of these disinfectants on the formation of disinfection byproducts was investigated. Results showed that preozonation decreased the formation of trihalomethanes (THMs), haloacetic acids (HAAs) and total organic halogen (TOX) for most waters during postchlorination. A net increase in THMs, HAAs and TOX was observed for a water of low humic content. Either decreases or increases were observed in dihaloacetic acids and unknown TOX (UTOX) as a result of preozonation when used with chloramination. Chloramines and chlorine dioxide produced a higher percentage of UTOX than free chlorine. They also formed more iodoform and total organic iodine (TOI) than free chlorine in the presence of iodide. Free chlorine produced a much higher level of total organic chlorine (TOCl) and bromine (TOBr) than chloramines and chlorine dioxide in the presence of bromide.     

Comparison of the disinfection by-product formation potential of treated waters exposed to chlorine and monochloramine

The formation of disinfection by-products (DBPs) from chlorination and monochloramination of treated drinking waters was determined. Samples were collected after treatment at 11 water treatment works but before exposure to chlorine or monochloramine. Formation potential tests were carried out to determine the DBPs formed by chlorination and monochloramination. DBPs measured were trihalomethanes (THMs), haloacetic acids (HAAs), halonitromethanes (HNMs), haloacetonitriles (HANs), haloaldehydes (HAs), haloketones (HKs) and iodo-THMs (i-THMs). All waters had the potential to form significant levels of all the DBPs measured. Compared to chlorine, monochloramination generally resulted in lower concentrations of DBPs with the exception of 1,1-dichloropropanone. The concentrations of THMs correlated well with the HAAs formed. The impact of bromine on the speciation of the DBPs was determined. The literature findings that higher bromide levels lead to higher concentrations of brominated DBPS were confirmed.     

2. Comparison of the disinfection by-product formation potentials between a wastewater effluent and surface waters

In this study, the chemical reactivity with chlorine as measured by disinfection by-product formation potential (DBPFP) is compared among samples of a wastewater effluent and surface waters. Water samples that had higher anthropogenic impacts were found to have higher overall DBPFP due primarily to higher dissolve organic carbon (DOC) concentrations. Effluent-derived organic matter (EfOM), however, was found to be less reactive with chlorine on a per DOC concentration basis. Yet, EfOM had higher proportions of brominated DBP, which may be associated with greater health risks. In this research, pyrolysis-GC/MS was used to establish relationship between structural features of DOC and DBPFP. We show that there is a critical set of pyrolysis fragments that separates the waters based on the degree of anthropogenic influence. Even though no single chemical marker was found to be indicative of the formation potentials of different classes of DBP, combinations of chemical fragments were found to be associated with the formation potentials of total trihalomethane (THM), brominated THM, total haloacetic acid (HAA), and brominated HAA for this set of samples. In contrast to previous work, the phenolic signature of these samples was negatively correlated to DBPFP, whereas strong relationships were found between DBPFP and the organic nitrogen and halogenated signatures.     

Formation of organic chloramines during water disinfection - chlorination versus chloramination

Many of the available studies on formation of organic chloramines during chlorination or chloramination have involved model organic nitrogen compounds (e.g., amino acids), but not naturally occurring organic nitrogen in water. This study assessed organic chloramine formation during chlorination and chloramination of 16 natural organic matter (NOM) solutions and 16 surface waters which contained dissolved organic nitrogen (DON). Chlorination rapidly formed organic chloramines within 10 min, whereas chloramination formed organic chloramination much more slowly, reaching the maximum concentration between 2 and 120 h after the addition of monochloramine into the solutions containing DON. The average organic chloramine formation upon addition of free chlorine and monochloramine into the NOM solutions were 0.78 mg-Cl₂/mg-DON at 10 min and 0.16 mg-Cl₂/mg-DON at 24 h, respectively. Organic chloramine formation upon chlorination and chloramination increased as the dissolved organic carbon/dissolved organic nitrogen (DOC/DON) ratio decreased (i.e., DON contents increased). Chlorination of molecular weight (10,000 Da) fractionated water showed that molecular weight of DON would not impact the amount of organic chloramines produced. Comparison of three different disinfection schemes at water treatment plants (free chlorine, preformed monochloramine, and chlorine/ammonia additions) indicated organic chloramine formation could lead to a possible overestimation of disinfection capacity in many chloraminated water systems that add chlorine followed by an ammonia addition to form monochloramine.     

A new method for differentiating adducts of common drinking water DBPs from higher molecular weight DBPs in electrospray ionization-mass spectrometry analysis

With the presence of bromide in source waters, numerous brominated disinfection byproducts (DBPs) are formed during chlorination. Many of them are polar/highly polar DBPs and thus hard to be detected by gas chromatography mass spectrometry. Electrospray ionization triple quadrupole mass spectrometry (ESI-MS/MS) is reported to be an effective method in finding polar brominated DBPs by setting precursor ion scans of m/z 79 and 81. But as a soft ionization technique, ESI could form adducts of common DBPs, which may complicate ESI-MS/MS spectra and hinder the efforts in finding new brominated DBPs. In this paper, a new method was developed for differentiating adducts of common DBPs from higher molecular weight DBPs. This method was based on the ESI-MS/MS precursor ion scans of the fragments that correspond to the molecular ions of common DBPs. Adducts of common DBPs were selectively detected in the ESI-MS/MS spectra of a simulated drinking water sample. Moreover, the structures of several new brominated DBPs in the sample were tentatively proposed.     

Trichloramine in swimming pools--formation and mass transfer

Trichloramine is a volatile, irritant compound of penetrating odor, which is found as a disinfection by-product in the air of chlorinated indoor swimming pools from reactions of nitrogenous compounds with chlorine. Acid amides, especially urea, ammonium ions and α-amino acids have been found as most efficient trichloramine precursors at acidic and neutral pH. For urea a relative NCl₃ formation of 96% at pH 2.5 and 76% at pH 7.1 was determined. Even under sub-stoichiometric molar ratios of Cl/N the formation of NCl₃ is favored over mono and dichlorinated products. However, the reaction kinetics of urea with chlorine is slow under conditions relevant for swimming pools. Also the mass transfer of NCl₃ from water to the gas phase which was calculated by the Deacon’s boundary layer model could be shown as a relatively slow process. Mass transfer would take 20 h or 5.8 d for a rough or a quiescent surface of the water, respectively. This is much more than a typical turnover rate of 6-8 h of a treatment cycle of a 25 m swimming pool. Therefore processes to remove NCl₃ and its precursors can help to minimize the exposure of bathers.     

典型含氮有机物的氯消毒副产物生成潜能研究

污水再生利用是解决我国城市水资源短缺的有效途径，消毒是保证再生水水质安全的必要措施。氯消毒可以有效杀灭病原微生物，但同时也会生成各种具有毒性和“三致”效应的消毒副产物。由于含氮有机物是污水氯消毒副产物的一类重要前体物，故选取20种基本氨基酸为研究对象，考察了它们经氯消毒后生成三氯甲烷、卤乙酸、卤乙腈、三氯硝基甲烷、1，1-二氯-2-丙酮和1，1，1-三氯-2-丙酮的潜能。结果表明，各种氨基酸的消毒副产物生成潜能与它们的R基结构密切相关，其中R基上带有活性苯环的色氨酸和酪氨酸均表现出了较高的三氯甲烷、卤乙酸和卤乙腈生成潜能。     

Bioanalytical and chemical assessment of the disinfection by-product formation potential: Role of organic matter

Disinfection by-products (DBP) formed from natural organic matter and disinfectants like chlorine and chloramine may cause adverse health effects. Here, we evaluate how the quantity and quality of natural organic matter and other precursors influence the formation of DBPs during chlorination and chloramination using a comprehensive approach including chemical analysis of regulated and emerging DBPs, total organic halogen quantification, organic matter characterisation and bioanalytical tools. In vitro bioassays allow us to assess the hazard potential of DBPs early in the chain of cellular events, when the DBPs react with their molecular target(s) and activate stress response and defence mechanisms. Given the reactive properties of known DBPs, a suite of bioassays targeting reactive modes of toxic action including genotoxicity and sensitive early warning endpoints such as protein damage and oxidative stress were evaluated in addition to cytotoxicity. Coagulated surface water was collected from three different drinking water treatment plants, along with reverse osmosis permeate from a desalination plant, and DBP formation potential was assessed after chlorination and chloramination. While effects were low or below the limit of detection before disinfection, the observed effects and DBP levels increased after disinfection and were generally higher after chlorination than after chloramination, indicating that chlorination forms higher concentrations of DBPs or more potent DBPs in the studied waters. Bacterial cytotoxicity, assessed using the bioluminescence inhibition assay, and induction of the oxidative stress response were the most sensitive endpoints, followed by genotoxicity. Source waters with higher dissolved organic carbon levels induced increased DBP formation and caused greater effects in the endpoints related to DNA damage repair, glutathione conjugation/protein damage and the Nrf2 oxidative stress response pathway after disinfection. Fractionation studies indicated that all molecular weight fractions of organic carbon contributed to the DBP formation potential, with the humic rich fractions forming the greatest amount of DBPs, while the low molecular weight fractions formed more brominated DBPs due to the high bromide to organic carbon ratio. The presence of higher bromide concentrations also led to a higher fraction of brominated DBPs as well as proportionally higher effects. This study demonstrates how a suite of analytical and bioanalytical tools can be used to effectively characterise the precursors and formation potential of DBPs.     

Studies of the halogenation of dissolved organic material during the chlorination of saline cooling waters,the model compounds resorcinol diacetate and resorcinol dimethyl ether

Chlorination of seawater containing resorcinol diacetate or resorcinol dimethyl ether results primarily in the formation of brominated products. At low chlorine concentrations (cf. model compound), ring substitution products dominate whilst at higher chlorine levels ring cleavage occurs and trihalomethanes are produced. Electrophilic chlorination of the model compounds in seawater therefore appears to be slower than the formation of HOBr by oxidation of naturally occurring bromide. The influence of solution acidity on the nature and extent of halogenation is described and reaction mechanisms postulated.     

Simultaneous degradation of disinfection byproducts and earthy-musty odorants by the UV/H2O2 advanced oxidation process

Advanced treatment technologies that control multiple contaminants are beneficial to drinking water treatment. This research applied UV/H₂O₂ for the simultaneous degradation of geosmin, 2-methylisoborneol, four trihalomethanes and six haloacetic acids. Experiments were conducted in de-ionized water at 24 ± 1.0 °C with ng/L amounts of odorants and μg/L amounts of disinfection byproducts. UV was applied with and without 6 mg/L H₂O_2. The results demonstrated that brominated trihalomethanes and brominated haloacetic acids were degraded to a greater extent than geosmin and 2-methylisoborneol. Tribromomethane and dibromochloromethane were degraded by 99% and 80% respectively at the UV dose of 1200 mJ/cm² with 6 mg/L H₂O₂, whereas 90% of the geosmin and 60% of the 2-methylisoborneol were removed. Tribromoacetic acid and dibromoacetic acid were degraded by 99% and 80% respectively under the same conditions. Concentrations of trichloromethane and chlorinated haloacetic acids were not substantially reduced under these conditions and were not effectively removed at doses designed to remove geosmin and 2-methylisoborneol. Brominated compounds were degraded primarily by direct photolysis and cleavage of the C-Br bond with pseudo first order rate constants ranging from 10⁻³ to 10⁻² s⁻¹. Geosmin and 2-methylisoborneol were primarily degraded by reaction with hydroxyl radical with direct photolysis as a minor factor. Perchlorinated disinfection byproducts were degraded by reaction with hydroxyl radicals. These results indicate that the UV/H₂O₂ can be applied to effectively control both odorants and brominated disinfection byproducts.     

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.     

Biodegradability of organic by-products after natural organic matter oxidation with ClO2--case study

Apart from well-known chlorites and chlorates, chlorine dioxide also generates easily biodegradable carbonyl compounds and short chain carboxylic acids during water disinfection. The main goal of the presented study was to examine the influence of natural organic matter (NOM) oxidation with chlorine dioxide, on the quantity as well as the quality of formed biodegradable by-products. In the experiments conducted at the pilot plant the sand filtered water (MWI) and ozonated/biofiltrated water (BAF) were oxidised with ClO2. The amount of BDOC formed as a result of the oxidation of both waters with ClO2 was compared. The results showed considerable differences in formation of ClO2 oxidation by-products between non-ozonated and ozonated/biofiltered waters. The disinfection of ozonated/biofiltrated water with ClO2 generated comparable amounts of aldehydes and much higher amounts of carboxylic acids than ClO2 oxidation of sand filtered water. These findings are essential for waterworks with ozonation/biofiltration units and ClO2 disinfection implemented.