Trihalomethanes In Water Research Articles

Trihalomethanes in Lisbon Indoor Swimming Pools: Occurrence, Determining Factors, and Health Risk Classification

Characterization of water quality from indoor swimming pools, using chorine-based disinfection techniques, was performed during a 6-mo period to study the occurrence, distribution, and concentration factors of trihalomethanes (THM). Several parameters such as levels of water THM, water and air chloroform, water bromodichloromethane (BDCM), water dibromochloromethane (DBCM), water bromoform (BF), free residual chlorine (FrCl), pH, water and air temperature, and permanganate water oxidizability (PWO) were determined in each pool during that period. Chloroform (CFW) was the THM detected at higher concentrations in all pools, followed by BDCM, DBCM, and BF detected at 99, 34, and 6% of the samples, respectively. Water THM concentrations ranged from 10.1 to 155 μg/L, with 6.5% of the samples presenting values above 100 μg/L (parametric value established in Portuguese law DL 306/2007). In this study, air chloroform (CFAir) concentrations ranged from 45 to 373 μg/m3 with 24% of the samples presenting values above 136 μg/m3 (considered high exposure value). Several significant correlations were observed between total THM and other parameters, namely, CFW, CFAir, FrCl, water temperature (TW), and PWO. These correlations indicate that FrCl, TW and PWO are parameters that influence THM formation. The exposure criterion established for water THM enabled the inclusion of 67% of Lisbon pools in the high exposure group, which reinforces the need for an improvement in pool water quality.

Electrochemical Determination of Trihalomethanes in Water by Means of Stripping Analysis

A protocol has been developed and evaluated for the determination of trihalomethanes (THMs) at the submicromolar concentration level in water. This method is based on a three-step stripping analysis that utilizes a single electrochemical cell and that entails (a) direct electrochemical reduction of a trihalomethane at a silver cathode to form halide ions in an aqueous sample containing tetraethylammonium benzoate, (b) capture of the released halide ions as a silver halide film on the surface of a silver gauze anode, and (c) cathodic reduction and quantitation of the silver halide film by means of differential pulse voltammetry. Using this procedure, we have determined THMs individually; bromoform and chloroform have been successfully quantitated in 30 min and with a detection limit of 3.0 μg L(-1) (12 nM) and 6.0 μg L(-1) (50 nM), respectively. In addition, we have employed our methodology to determine the total trihalomethane (TTHM) content in a prepared water sample at a level commensurate with the maximum allowable annual average of 80 μg L(-1) mandated by the United States Environmental Protection Agency. We have compared our TTHM results to those obtained by an independent testing laboratory.

Solvent-minimized extraction for determining halonitromethanes and trihalomethanes in water

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

Comparison of Trihalomethanes in Tap Water and Blood: A Case Study in the United States

Background: Epidemiological studies have used various measures to characterize trihalomethane (THM) exposures, but the relationship of these indicators to exposure biomarkers remains unclear.Objectives: We examined temporal and spatial variability in baseline blood THM concentrations and assessed the relationship between these concentrations and several exposure indicators (tap water concentration, water-use activities, multiroute exposure metrics).Methods: We measured water-use activity and THM concentrations in blood and residential tap water from 150 postpartum women from three U.S. locations.Results: Blood ΣTHM [sum of chloroform (TCM), bromodichloromethane (BDCM), dibromo-chloromethane (DBCM), and bromoform (TBM)] concentrations varied by site and season. As expected based on variable tap water concentrations and toxicokinetic properties, the proportion of brominated species (BDCM, DBCM, and TBM) in blood varied by site (site 1, 24%; site 2, 29%; site 3, 57%) but varied less markedly than in tap water (site 1, 35%; site 2, 75%; site 3, 68%). The blood–water ΣTHM Spearman rank correlation coefficient was 0.36, with correlations higher for individual brominated species (BDCM, 0.62; DBCM, 0.53; TBM, 0.54) than for TCM (0.37). Noningestion water activities contributed more to the total exposure metric than did ingestion, but tap water THM concentrations were more predictive of blood THM levels than were metrics that incorporated water use.Conclusions: Spatial and temporal variability in THM concentrations was greater in water than in blood. We found consistent blood–water correlations across season and site for BDCM and DBCM, and multivariate regression results suggest that water THM concentrations may be an adequate surro-gate for baseline blood levels.

TRIHALOMETHANES INTERNAL DOSE AND MATERNAL GSTT1 AND GSTM1 GENES POLYMORPHISM CONTRIBUTION TO THE RISK OF PRETERM BIRTH

Background and Aims: There is some evidence that prenatal exposure to drinking water trihalomethanes (THM) has a detrimental effect on birth outcome. Both environmental factors and genes involved in metabolic detoxification process may be associated with preterm birth. The relationship between THM exposure and preterm birth in genetically susceptible subjects is not clear. The objective of this study is to investigate whether the polymorphisms of metabolic genes GSTT1 and GSTM1 affect the association of maternal exposure to THM with preterm birth. Methods: We conducted a nested case-control study of 682 pregnant women in Kaunas (Lithuania) using individual information on water drinking, showering and bathing habits during pregnancy, and uptake factors of THMs in blood, estimated as internal dose of THM. We used logistic regression to evaluate the relationship between internal THM dose, preterm births and individual and the joint (modifying) effects of the metabolic gene polymorphisms controlling for family status, maternal smoking, body mass index, alcohol consumption, education, and infant birth year. Results: The estimated individual total uptake of THMs ranged between 0.0025 and 2.40 µg/d. The findings suggest that carriers of the GSTM1–0 genotype and exposed to THM, chloroform and bromodichloromethane had an increased risk for preterm birth compared to carriers of the GSTM1–1 genotype: the ORs during the second trimester among woman GSTM1–1 genotype carriers were 1.0–1.11, while among GSTM1–0 genotype carriers ORs were 1.66–2.07. Exposure to dibromochloromethane during the first trimester among carriers of the GSTM1–1 genotype was associated with an OR of 7.35, 95% CI 2.62–20.6, and among carriers of the GSTM1–0 genotype produced an OR of 2.81, 95% CI 1.21–6.52. Conclusions: These data suggest that THM internal dose may affect preterm birth and that maternal GSTM1 and GSTT1 genotypes modify the THM exposure effects on preterm birth.

Determinants of chlorination by-products in indoor swimming pools

Water and air quality of fifteen swimming pools using chlorine disinfection was measured during eight sampling campaigns in Rennes, France. Concentrations of trihalomethanes (THMs) and trichloramine (NCl(3)) in air as well as concentrations of parameters, including total organic carbon (TOC), chlorine (free, combined and total), pH, Kjeldhal nitrogen (KN), chloride ions and THMs in water and air temperature, were measured. Water and air samples were collected during 3h in the morning and afternoon, during high and low attendance days, in summer and winter. Data analysis was perfomed by multivariate ordinary least square (OLS) and quantile (QR) regressions, from both data quality and other parameters such as the ratio between the number of visitors and the volume of water available V/W, the proportion of air re-circulated and the number of swimmers during sampling. The geometric means (GM±95% CIs) of the sum of THMs (TTHM) and NCl(3) in air were 74.9±6.7 μg/m(3) and 190±10 μg/m(3), respectively. As expected, concentrations of TTHM in air were correlated to concentrations of TTHM in water. Concentrations of TTHM and NCl(3) in air measured in winter were significantly higher than in summer, depicting that low air exchange rate in winter lead to accumulation of pollutants. NCl(3) (especially at higher quantiles) and TTHM concentrations in air were associated to the number of swimmers. NCl(3) was also linked to air temperature and pH. Moreover TTHM and NCl(3) in air seemed to be affected by additional determinants including the volume of hall and the ratio V/W. In a process of reducing exposure, the OLS regression provides useful information on key parameters influencing concentrations of THMs and NCl(3) in indoor swimming pools. In addition, QR allows identifying factors associated to elevated levels of contamination.

Individual exposures to drinking water trihalomethanes, low birth weight and small for gestational age risk: a prospective Kaunas cohort study

BackgroundEvidence for an association between exposure during pregnancy to trihalomethanes (THMs) in drinking water and impaired fetal growth is still inconsistent and inconclusive, in particular, for various exposure routes. We examined the relationship of individual exposures to THMs in drinking water on low birth weight (LBW), small for gestational age (SGA), and birth weight (BW) in singleton births.MethodsWe conducted a cohort study of 4,161 pregnant women in Kaunas (Lithuania), using individual information on drinking water, ingestion, showering and bathing, and uptake factors of THMs in blood, to estimate an internal dose of THM. We used regression analysis to evaluate the relationship between internal THM dose and birth outcomes, adjusting for family status, education, smoking, alcohol consumption, body mass index, blood pressure, ethnic group, previous preterm, infant gender, and birth year.ResultsThe estimated internal dose of THMs ranged from 0.0025 to 2.40 mg/d. We found dose-response relationships for the entire pregnancy and trimester-specific THM and chloroform internal dose and risk for LBW and a reduction in BW. The adjusted odds ratio for third tertile vs. first tertile chloroform internal dose of entire pregnancy was 2.17, 95% CI 1.19-3.98 for LBW; the OR per every 0.1 μg/d increase in chloroform internal dose was 1.10, 95% CI 1.01-1.19. Chloroform internal dose was associated with a slightly increased risk of SGA (OR 1.19, 95% CI 0.87-1.63 and OR 1.22, 95% CI 0.89-1.68, respectively, for second and third tertile of third trimester); the risk increased by 4% per every 0.1 μg/d increase in chloroform internal dose (OR 1.04, 95% CI 1.00-1.09).ConclusionsTHM internal dose in pregnancy varies substantially across individuals, and depends on both water THM levels and water use habits. Increased internal dose may affect fetal growth.

Analysis of trihalomethanes in water and air from indoor swimming pools using HS-SPME/GC/ECD

Headspace solid phase microextraction (HS-SPME) with further quantification by gas chromatography and electron capture detector (GC/ECD) was used to analyze trihalomethanes (THMs) in water and air from indoor swimming pools (ISPs). High correlation coefficients were obtained for the calibration lines in water with detection limits of 0.2 μg/L for trichloromethane (TCM) and bromodichloromethane (BDCM), 0.1 μg/L for dibromochloromethane (DBCM) and 0.5 μg/L for tribromomethane (TBM). Coefficients of variation values were 5–10% for repeatability and 15–25% for reproducibility. In air analysis, high correlation coefficients were also obtained for the calibration lines with detection limits of 2.5 μg/m3 for TCM and BDCM and 1.25 μg/m3 for DBCM and TBM. Repeatability and reproducibility coefficients of variation were the same as in water analysis. Analytical results from a survey in four Portuguese ISPs showed that the mean concentration of total trihalomethanes (TTHMs) in water ranged from 22±2 to 577±58 μg/L. In the lack of European specific regulation for THMs in water from ISPs and taking into consideration that ingestion is a form of exposure, TTHMs’ values were compared with European drinking water maximum contamination level (100 μg/L, Directive 98/83/CE). From the reported TTHMs mean concentration values in ISPs’ water, 40% exceeded that value. TTHMs values determined in the air (T = 30°C) ranged from 98±10 to 1225±123 μg/m3 and from 51±5 μg/m3to 519±52 μg/m3at 5 and 150 cm above the water surface, respectively. As expected, swimmers are more exposed to high concentrations of THMs than lifeguards. As there is no European specific regulation for THMs in ISPs’ air, the highest TCM values were compared with maximum values reported in the literature for ISPs (1630 μg/m3) and with the inhalation exposure limit (10,000 μg/m3) established for TCM by European occupational legislation (Directive 2000/39/CE).

Potential presence of trihalomethanes in water intended for human consumption

Since the 1970s it is well known that, though water for human consumption must generally be disinfected before being distributed along the network, the use of chemicals results in the formation of many different Disinfeection By-Products (DBPs). In the case of chlorine-based disinfectants, trihalomethanes (THMs) are the most widely studied: the present work first compares some national and international regulations on this subject, then, in the experimental part, compares the results of a test carried out by disinfecting water of different origin collected in three different Italian regions with different amounts of chlorine. Samples were stored at ambient temperature for seven days, then the determination of THMs was carrried out by Purge and Trap extraction coupled with gas cromatography with Electron Capture Detection (ECD). The result obtained are finally compared and discussed.

Exposure to Drinking Water Trihalomethanes Through Different Routes and Low Birth Weight Risk in Genetically Susceptible Women

Exposure to Drinking Water Trihalomethanes Through Different Routes and Low Birth Weight Risk in Genetically Susceptible Women

Disinfection By-products: A Question of Balance

Disinfection By-products: A Question of Balance

Ionic liquid-based single drop microextraction and room-temperature gas chromatography for on-site ion mobility spectrometric analysis

The combination of ionic liquid-based headspace single drop microextraction (IL-HS-SDME) and room-temperature gas chromatography/ion mobility spectrometry (RTGC-IMS) is presented for the first time using the direct determination of trihalomethanes in waters as model analytical problem. The ionic liquid allows the transference of the analytes from the sample to the analytical system, at the same time that it provides an increase of the sensitivity and selectivity of the determination. An injection unit has been designed to permit the efficient volatilization of the analytes at room temperature and to avoid the entering of IL in the system. The direct combination allows the determination of the halocompounds in a rapid and simple way taking advance of their characteristic IMS spectra. The limits of the detection range between 0.1 ng mL −1 (bromoform) and 0.9 ng mL −1 (chloroform), the reproducibility of the system being better than 7.1% (RSD). The proposed coupling opens up a new horizon in IMS-based applications.

Purge efficiency in the determination of trihalomethanes in water by purge-and-trap gas chromatography

Purge-and-trap gas chromatography–mass spectrometry (PT-GC–MS) has become an accepted method for the analysis of trihalomethanes (THMs) in water. The purge-and-trap technique is based on an efficient transfer of volatile organic compounds from the liquid (contained in the purge chamber) to the gaseous phase by bubbling with an inert gas. The aim of this work was to study the purge system's efficiency by means of several consecutive purge cycles lasting 11 min each of the same liquid sample. The concentration range chosen of THMs was very wide [5–200 μg L −1]. The inert gas flow rate was 40 mL min −1, and experiments were performed at temperatures of 25, 35 and 50 °C. Bromoform (CHBr 3), the least volatile compound, needed 19 cycles to be purged quantitatively at a concentration of 200 μg L −1 and only 7 cycles at 5 μg L −1 for a 25 mL sample at 25 °C. Chloroform (CHCl 3), the most volatile compound, required 4 cycles to be fully extracted at 200 μg L −1 and 2 at 5 μg L −1. Finally, Novak's theoretical model, based on the distribution constant between gas and liquid phases, was used to correlate the THMs purging extraction data.

Determination of trihalomethanes in waters by ionic liquid-based single drop microextraction/gas chromatographic/mass spectrometry

A simple, rapid, solventless method for the determination of trihalomethanes (THMs) (chloroform, bromodichloromethane, dibromochloromethane and bromoform) in water samples is presented. The analytes are extracted from the headspace of the aqueous matrix into a 2μL drop of the ionic liquid 1-octyl-3-methyl-imidazolium hexafluorophosphate working at 30°C for 30min. The separation and detection of the target compounds is accomplished by gas chromatography/mass spectrometry owing to the use of an interface that efficiently transfers the analytes extracted in the ionic liquid drop to the gas chromatograph while preventing the ionic liquid from entering the column. The detection limits obtained are below the values compelled by the legislation, ranging from 0.5μgL−1 for chloroform and bromodichloromethane to 0.9μgL−1 for dibromochloromethane. The use of ionic liquid in the extraction procedure avoids the use of organic solvents and leads to relative standard deviations that range from 3.1% to 4.8%.

Headspace–programmed temperature vaporizer–fast gas chromatography–mass spectrometry coupling for the determination of trihalomethanes in water

A new method based on the use of a headspace autosampler in combination with a GC equipped with a programmable temperature vaporizer (PTV) and an MS detector has been developed for the screening and quantitative determination of trihalomethanes (THMs) in different aqueous matrices. The use of headspace generation to introduce the sample has the advantage that no prior sample treatment is required, thus minimizing the creation of analytical artifacts and the errors associated with this step of the analytical process. The PTV inlet used was packed with Tenax-TA. The injection mode was solvent vent, in which the analytes are retained in the hydrophobic insert packing by cold trapping, while the water vapour is eliminated through the split line. This allows rapid injection of the sample in splitless mode, very low detection limits being achieved without the critical problem of initial sample bandwidth. The capillary column used allowed rapid separations with half-height widths ranging from 1.68 s (chloroform) to 0.66 s (bromoform). The GC run time was 7.3 min. The use of mass spectrometry allows the identification and quantification of the analytes at the low ppt level. The S/N ratio was at least 10-fold higher when the SIM mode was used in data acquisition as compared to the scan mode. The proposed method is extremely sensitive, with detection limits ranging from 0.4 to 2.6 ppt.

Removal of humic acid using TiO 2 photocatalytic process – Fractionation and molecular weight characterisation studies

The photocatalytic removal of humic acid (HA) using TiO 2 under UVA irradiation was examined by monitoring changes in the UV 254 absorbance, dissolved organic carbon (DOC) concentration, apparent molecular weight distribution, and trihalomethane formation potentials (THMFPs) over treatment time. A resin fractionation technique in which the samples were fractionated into four components: very hydrophobic acids (VHA), slightly hydrophobic acids, hydrophilic charged (CHA) and hydrophilic neutral (NEU) was also employed to elucidate the changes in the chemical nature of the HA components during treatment. The UVA/TiO 2 process was found to be effective in removing more than 80% DOC and 90% UV 254 absorbance. The THMFPs of samples were decreased to below 20 μg l −1 after treatments, which demonstrate the potential to meet increasingly stringent regulatory level of trihalomethanes in water. Resin fractionation analysis showed that the VHA fraction was decreased considerably as a result of photocatalytic treatments, forming CHA intermediates which were further degraded with increased irradiation time. The NEU fraction, which comprised of non-UV-absorbing low molecular weight compounds, was found to be the most persistent component.

Drink a Toast to Tap Water: Study Suggests Water Consumption Benefit Outweighs THM Hazard

Vol. 115, No. 11 EnvironewsOpen AccessDrink a Toast to Tap Water: Study Suggests Water Consumption Benefit Outweighs THM Hazard John Tibbetts John Tibbetts Search for more papers by this author Published:1 November 2007https://doi.org/10.1289/ehp.115-a551aAboutSectionsPDF ToolsDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InReddit Many water treatment systems use chlorine to disinfect drinking water. However, chlorine reacts with dissolved organic matter in water to create trihalomethanes (THMs), which have been associated with excess risk of bladder cancer in people who drink chlorinated water. Now, in a large study conducted in Spain, an international team of scientists has examined the role of tap water and total fluid intake in bladder cancer risk, while also assessing the effect of exposure to THMs in water [EHP 115:1569–1572; Michaud et al.]. The results suggest that higher water consumption is associated with lower risk of bladder cancer, regardless of THM exposure.Some studies have linked high consumption of fluids including tap water with a lower risk of bladder cancer, perhaps because urinating more frequently allows more flushing of the bladder. Other studies suggest that high tap water consumption could increase bladder cancer risk if chlorination by-products or other water contaminants such as arsenic are elevated in the water source. Adding to this complexity is that still other studies have shown a THM-related excess risk of bladder cancer in men but not women.Between June 1998 and June 2001, researchers conducted a hospital-based case–control study of bladder cancer in multiple centers in Spain. Male and female bladder cancer patients aged 20–80 years were recruited from 18 participating hospitals. For the 397 bladder cancer cases available for this analysis, the team recruited 664 matched controls who had been admitted to the same hospitals around the same time for hernias, fractures, orthopedic problems, and other reasons.Trained interviewers collected information during each subject’s hospitalization that included sociodemographic characteristics, family history of cancer, smoking history, occupational history, residential history, drinking water source at each residence, beverage consumption (including water), and medical history. The researchers used local government and water company data on annual average THM levels, water source history since 1920, and chlorination history to calculate average year-by-year THM exposure. These data were available for 78.5% of the total study person-years.The researchers examined the association between total fluid and water consumption and bladder cancer risk, while also examining the interaction between water intake and THM exposure. The results suggest that drinking more water, even from chlorinated sources with high THM levels, is beneficial in reducing risk of bladder cancer. The authors found a 53% lower risk of bladder cancer in people who drank 1,400 mL or more water per day compared with those who drank less than 400 mL per day after adjusting for known and potential confounders. This inverse association held across all strata of smoking status and THM exposure, and for both men and women.The study was strengthened by high response rates from cases and controls, detailed interview data on individual beverage consumption, detailed assessment of THM exposure, and detailed data on smoking, which is believed to be the greatest risk factor for bladder cancer.Drink up! Despite the potential for THM exposure, water is still a healthy choice of beverage.FiguresReferencesRelatedDetails Vol. 115, No. 11 November 2007Metrics About Article Metrics Publication History Originally published1 November 2007Published in print1 November 2007 Financial disclosuresPDF download License information EHP is an open-access journal published with support from the National Institute of Environmental Health Sciences, National Institutes of Health. All content is public domain unless otherwise noted. Note to readers with disabilities EHP strives to ensure that all journal content is accessible to all readers. However, some figures and Supplemental Material published in EHP articles may not conform to 508 standards due to the complexity of the information being presented. If you need assistance accessing journal content, please contact [email protected]. Our staff will work with you to assess and meet your accessibility needs within 3 working days.

Determination of Trihalomethanes in Drinking Water by Dispersive Liquid–Liquid Microextraction then Gas Chromatography with Electron-Capture Detection

Dispersive liquid–liquid microextraction (DLLME) has been used for preconcentration of trihalomethanes (THMs) in drinking water. In DLLME an appropriate mixture of an extraction solvent (20.0 μL carbon disulfide) and a disperser solvent (0.50 mL acetone) was used to form a cloudy solution from a 5.00-mL aqueous sample containing the analytes. After phase separation by centrifugation the enriched analytes in the settled phase (6.5 ± 0.3 μL) were determined by gas chromatography with electron-capture detection (GC–ECD). Different experimental conditions, for example type and volume of extraction solvent, type and volume of disperser solvent, extraction time, and use of salt, were investigated. After optimization of the conditions the enrichment factor ranged from 116 to 355 and the limit of detection from 0.005 to 0.040 μg L−1. The linear range was 0.01–50 μg L−1 (more than three orders of magnitude). Relative standard deviations (RSDs) for 2.00 μg L−1 THMs in water, with internal standard, were in the range 1.3–5.9% (n = 5); without internal standard they were in the range 3.7–8.6% (n = 5). The method was successfully used for extraction and determination of THMs in drinking water. The results showed that total concentrations of THMs in drinking water from two areas of Tehran, Iran, were approximately 10.9 and 14.1 μg L−1. Relative recoveries from samples of drinking water spiked at levels of 2.00 and 5.00 μg L−1 were 95.0–107.8 and 92.2–100.9%, respectively. Comparison of this method with other methods indicates DLLME is a very simple and rapid (less than 2 min) method which requires a small volume of sample (5 mL).

Contribution of the FPA tasting panel to decision making about drinking water treatment facilities

The flavour profile analysis (FPA) panel of Aigües de Barcelona has participated in three engineering projects initiated to improve both the quality of the water supplied and the use of the scarce resources available. The information provided by the panel enables a solid evaluation of the organoleptic quality of the water produced in the facilities, which is very useful in making decisions concerning the development of the projects. The first project refers to the Besòs full scale nanofiltration pilot plant. The study includes characterisation of the organoleptic quality of the water obtained and the behaviour of blends in different proportions with water from the Ter river. Secondly, this article presents the results obtained in El Papiol pilot plant for the reduction of trihalomethanes in water from the Abrera WTP, situated by the Llobregat river. The tasting results indicate that the stripping treatment slightly improves the quality of water, whereas the improvement is more remarkable with carbon filtration. The third project was the reverse osmosis pilot plant installed in the Sant Joan Despi WTP, which also collects water from the Llobregat river. A gradual improvement of the water treated was clearly observed when increasing amounts of reverse osmosis treated water were added. Some trends were also observed according to the characteristics of the feed water to the reverse osmosis facilities.

Cometabolism of trihalomethanes by mixed culture nitrifiers

Three mixed-culture nitrifier sources degraded low concentrations (25–450 μg/L) of four trihalomethanes (THMs) (trichloromethane (TCM) or chloroform, bromodichloromethane (BDCM), dibromochloromethane (DBCM), tribromomethane (TBM) or bromoform) commonly found in treated drinking water. Individual THM rate constants ( k 1 THM ) increased with increasing THM bromine-substitution with TBM>DBCM>BDCM>TCM and were comparable to previous studies with the pure culture nitrifier, Nitrosomonas europaea. A decrease in temperature resulted in a decrease in both ammonia and THM degradation rates with ammonia rates affected to a greater extent than THM degradation rates. The significant effect of temperature indicates that seasonal variations in water temperature should be a consideration for technology implementation. Product toxicity, measured by transformation capacity ( T c), was similar to that observed with N. europaea. Because both rate constants and product toxicities increase with increasing THM bromine-substitution, a water's THM speciation is an important consideration for process implementation during drinking water treatment. Even though a given water is kinetically favored, the resulting THM product toxicity may not allow stable treatment process performance.