Occurrence of THMs and HAAs in experimental chlorinated waters of the Quebec City area (Canada)

Haloacetic acids (HAAs) and trihalomethanes (THMs) were generated in bench-scale chlorination experiments using treated waters (prior to final chlorination) of the three major drinking water utilities of the Quebec City area. The purpose was to investigate the formation and occurrence of these chlorination by-products (CBPs) on a seasonal basis. Data for HAAs, THMs and other physico-chemical parameters were produced through a six-month sampling program with variable conditions of water quality, water temperature, applied chlorine dose and reaction time. In waters from the three utilities, chloroform (THM specie), dichloroacetic and trichloroacetic acid (HAA species) were the most prevalent compounds due to the low concentrations of bromide in the utilities' raw waters. Significant differences in CBP occurrence were noted between the three utilities' chlorinated waters, mainly due to the type of disinfectant applied to raw water. The use of pre-ozonation, as opposed to pre-chlorination (or direct chlorination) in one of the utilities appears to be the major factor contributing to that utility's potential for compliance with current THM and future HAA standards. Seasonal variations in THMs and HAAs were mainly associated with variations in organic precursors and to changes in water temperature (two parameters which vary widely on a seasonal basis in surface waters of southern Quebec), with CBP occurrence at its highest in spring. Statistical correlations between HAAs and THMs were moderate and only temperature appeared to affect the preponderance of one CBP or the other. Finally, a regression analysis was carried out aimed at associating each CBP to water quality and the experimental parameters. Thanks to their predictive ability, multivariate models seem to be the tools with the best potential for decision-making purposes.     

Determination of bromate and chlorinated haloacetic acids in bottled drinking water with chromatographic methods

Disinfection by-products of interest such as bromate, chlorate and chlorinated haloacetic acids in 10 representative brands of bottled drinking water were investigated with ion chromatography. With the developed method, the detection limits of the disinfection by-products were in sub-microgl(-1) level. It was observed that bromate, chlorate and dichloroacetic acid could be detected in some water samples. In the bottled natural water, the concentrations for the three compounds were 0.1, 0.9 and 0.6 microgl(-1), respectively. The total concentration of disinfection by-products in the natural water sample was the highest among all the bottled drinking waters. The concentrations for the sum of disinfection by-products in the four types of bottled drinking water investigated were natural water > mineral water > spring water > purified water. The generation of disinfection by-products was much influenced by the original components and process procedure of the source water. The concentrations of bromate and chlorate in the bottled water samples hardly degraded with the increasing storage time. For dichloroacetic acid, with the prolonging of storage time, the concentration was much decreased.     

Fate of disinfection by-products in groundwater during aquifer storage and recovery with reclaimed water

Knowledge on the behaviour of disinfection by-products (DBPs) during aquifer storage and recovery (ASR) is limited even though this can be an important consideration where recovered waters are used for potable purposes. A reclaimed water ASR trial in an anoxic aquifer in South Australia has provided some of the first quantitative information at field-scale on the fate and transport of trihalomethanes (THMs) and haloacetic acids (HAAs). The results revealed that THM half-lives varied from <1 to 65 days, with persistence of chloroform being highest and bromoform lowest. HAA attenuation was rapid (<1 day). Rates of THM attenuation were shown to be highly dependent on the geochemical environment as evidenced by the 2-5 fold reduction in half-lives at the ASR well which became methanogenic during the storage phase of the trial, as compared to an observation well situated 4 m away, which remained nitrate-reducing. These findings agree with previous laboratory-based studies which also show persistence declining with increased bromination of THMs and reducing redox conditions. Modelling suggests that the chlorinated injectant has sufficient residual chlorine and natural organic matter for substantial increases in THMs to occur within the aquifer, however this is masked in some of the field observations due to concurrent attenuation, particularly for the more rapidly attenuated brominated compounds. The model is based on data taken from water distribution systems and may not be representative for ASR since bromide and ammonia concentrations in the injected water and the possible role of organic carbon in the aquifer were not taken into consideration. During the storage phase DBP formation potentials were reduced as a result of the removal of precursor material despite an increase in the THM formation potential per unit weight of total organic carbon. This suggests that water quality improvements with respect to THMs and HAAs can be achieved through ASR in anoxic aquifers.     

Fate of disinfection by-products in groundwater during aquifer storage and recovery with reclaimed water

Knowledge on the behaviour of disinfection by-products (DBPs) during aquifer storage and recovery (ASR) is limited even though this can be an important consideration where recovered waters are used for potable purposes. A reclaimed water ASR trial in an anoxic aquifer in South Australia has provided some of the first quantitative information at field-scale on the fate and transport of trihalomethanes (THMs) and haloacetic acids (HAAs). The results revealed that THM half-lives varied from <1 to 65 days, with persistence of chloroform being highest and bromoform lowest. HAA attenuation was rapid (<1 day). Rates of THM attenuation were shown to be highly dependent on the geochemical environment as evidenced by the 2-5 fold reduction in half-lives at the ASR well which became methanogenic during the storage phase of the trial, as compared to an observation well situated 4 m away, which remained nitrate-reducing. These findings agree with previous laboratory-based studies which also show persistence declining with increased bromination of THMs and reducing redox conditions. Modelling suggests that the chlorinated injectant has sufficient residual chlorine and natural organic matter for substantial increases in THMs to occur within the aquifer, however this is masked in some of the field observations due to concurrent attenuation, particularly for the more rapidly attenuated brominated compounds. The model is based on data taken from water distribution systems and may not be representative for ASR since bromide and ammonia concentrations in the injected water and the possible role of organic carbon in the aquifer were not taken into consideration. During the storage phase DBP formation potentials were reduced as a result of the removal of precursor material despite an increase in the THM formation potential per unit weight of total organic carbon. This suggests that water quality improvements with respect to THMs and HAAs can be achieved through ASR in anoxic aquifers.     

Formation of halogenated acetaldehydes, and occurrence in Canadian drinking water

Controlled laboratory chlorination of acetaldehyde (ACD) under typical drinking water conditions (pH 6.7, 7.6 and 8.8, and temperature 4 degrees C and 21 degrees C) revealed that the formation of chloral hydrate (CH), the most common halogenated acetaldehyde (HAs), increased with contact time (0-10 days). However, at increased pH and temperature, CH reached maximum levels and subsequently broke down partially to chloroform and other unidentified compounds. After 10 days contact time, a maximum of 63% (molar) of the initial ACD consumed were converted into CH or chloroform (TCM). Various surveys of drinking water systems indicated that ACD is not the only precursor of CH. A suite of aldehydes (including ACD), and chlorinated disinfection by-products (including TCM and CH) were found in most distribution systems. The levels of bromide in source water impacted speciation of HAs. In addition to CH, brominated and other mixed (Cl/Br) acetaldehydes were detected in most samples; the speciation of HAs and THMs followed comparable trends. Similar to chloroform for trihalomethanes, CH contributed from as low as 5% to up to 60% of the total HAs. The bromine incorporation factors (BIF) in THMs and HAs were shown to increase with increasing bromide ion concentrations in the source water. Brominated THMs are more readily formed than their HA analogues; in fact, BIF values for THMs were 2-3 times higher than for the HAs. It was found that HAs may be as high as THMs in some drinking waters. As a result, the determination of the other target HAs, in addition to CH, is necessary for a better assessment of the pool of disinfection by-products in drinking water.     

Relationships among trihalomethane formation potential, organic carbon and lake enrichment

Trihalomethanes (THMs) are potential carcinogens formed from the reaction of the disinfectant chlorine with organic matter in the source water. This study of Kansas drinking water supply lakes evaluates the relationship among THM formation potential (THMFP), organic carbon and lake trophic state (LTS). THMFP was positively correlated to organic carbon. Total THMFP and total organic carbon were positively correlated to LTS, an estimator of lake enrichment, when very turbid lakes were omitted. These very turbid lakes (due to high suspended solids concentrations) had higher than expected THMFP, based on LTS, and higher organic carbon concentrations. THM data measured in the treated drinking water were positively correlated to THMFP, total organic carbon and LTS. The levels of organic carbon that contribute to THMs are a result of lake and watershed factors related to increasing levels of enrichment and suspended sediments. These factors are controllable by appropriate management practices.     

Disinfection by-products in Finnish drinking waters

Disinfection by-products (DBPs) were measured in plant effluents of 35 Finnish waterworks, which utilized different treatment processes and raw water sources. DBPs were measured also from the distribution systems of three waterworks. Di- and trichloroacetic acids, and chloroform were the major DBPs found in treated water samples. The concentration of six haloacetic acids (HAA6) exceeded the concentrations of trihalomethanes (THMs). Chlorinated drinking waters (DWs) originating from surface waters contained the highest concentration of HAA6 and THMs: 108 and 26 microg/l, respectively. The lowest concentrations of DBPs were measured from ozonated and/or activated carbon filtrated and chloraminated DWs. Higher concentrations of HAA6, THMs, and adsorbable organic halogens were measured in summer compared to winter. The levels of chlorinated acetic acids, chloroform, and bromodichloromethane correlated positively with mutagenicity. Past mutagenicity levels of DWs were examined. A major reduction in the use of prechlorination, increased use of chloramine disinfection, and better removal of organic carbon were the most important reasons for the 69% decrease in mutagenicity from 1985 to 1994.     

Trihalomethane formation during water disinfection in four water supplies in the Somes river basin in Romania

Background, aim and scope

After the discovery of chloroform in drinking water, an extensive amount of work has been dedicated to the factors influencing the formation of halogenated disinfections by-products (DBPs). The disinfection practice can vary significantly from one country to another. Whereas no disinfectant is added to many water supplies in Switzerland or no disinfectant residual is maintained in the distribution system, high disinfectant doses are applied together with high residual concentrations in the distribution system in other countries such as the USA or some southern European countries and Romania. In the present study, several treatment plants in the Somes river basin in Romania were investigated with regard to chlorine practice and DBP formation (trihalomethanes (THMs)). Laboratory kinetic studies were also performed to investigate whether there is a relationship between raw water dissolved organic matter, residual chlorine, water temperature and THM formation.

Materials and methods

Drinking water samples were collected from different sampling points in the water treatment plant (WTP) from Gilau and the corresponding distribution system in Cluj-Napoca and also from Beclean, Dej and Jibou WTPs. The water samples were collected once a month from July 2006 to November 2007 and stored in 40-mL vials closed with Teflon lined screw caps. Water samples were preserved at 4°C until analysis after sodium thiosulfate (Na₂S₂O₃) had been added to quench residual chlorine. All samples were analysed for THMs using headspace GC-ECD between 1 and 7 days after sampling. The sample (10 mL) was filled into 20-mL headspace vials and closed with a Teflon-lined screw cap. Thereafter, the samples were equilibrated in an oven at 60°C for 45 min. The headspace (1 mL) was then injected into the GC (Cyanopropylphenyl Polysiloxane column, 30 m × 53 mm, 3 μm film thickness, Thermo Finnigan, USA). The MDLs for THMs were determined from the standard deviation of eight standards at 1 μg/L. The MDLs for CHCl₃, CHBrCl₂, CHBr₂Cl and CHBr₃ were 0.3, 0.2, 0.3 and 0.6 μg/L, respectively. All kinetic laboratory studies were carried out only with water from the WTP Gilau. The experiments were conducted under two conditions: baseline conditions (pH 7, 21°C, 2.5 mg/L Cl₂) to gain information about the change of the organic matter in the raw water and seasonally variable conditions to simulate the actual process at the treatment plant and the distribution system.

Results and discussion

This study shows that the current chlorination practice in the investigated plants complies with the THM drinking water standards of the EU. The THM concentrations in all samples taken in the four treatment plants and distributions systems were below the EU drinking water standard for TTHMs of 100 μg/L. Due to the low bromide levels in the raw waters, the main THM formed in the investigated plants is chloroform. It could also be seen that the THM levels were typically lower in water supplies with groundwater as their water resource. In one plant (Dej) with a pre-ozonation step, a significantly lower (50%) THM formation during post-chlorination was observed. Laboratory chlorination experiments revealed a good correlation between chloroform formation and the consumed chlorine dose. Also, these experiments allowed a semi-quantative prediction of the chloroform formation in the distribution system of Cluj-Napoca.

Conclusions

CHCl₃ was the most important trihalomethane species observed after the chlorination of water in all of the sampled months. However, TTHM concentrations did not exceed the maximum permissible value of 100 μg/L (EU). The THM formation rates in the distribution system of Cluj-Napoca have a high seasonal variability. Kinetic laboratory experiments could be used to predict chloroform formation in the Cluj-Napoca distribution system. Furthermore, an empirical model allowed an estimation of the chloroform formation in the Gilau water treatment plant.

     

Multiple regression models: a methodology for evaluating trihalomethane concentrations in drinking water from raw water characteristics

The presence of trihalomethanes (THMs) in drinking water has attracted the attention of both researchers and professionals, because of the harmful effects of these substances on human health. A multiple regression model was developed to estimate THM concentrations in finished drinking water, using data from the Menidi Treatment Plant of Athens. A number of routinely measured characteristics--including chlorine dose, chlorophyll a, temperature, pH and bromide--of raw water, were used to generate a reliable methodology for predicting both total THM and individual species concentrations. Seasonality effects were also considered during the analysis. In general, these models were found to give acceptable fits, estimating accurately lows and highs over the annual cycle.     

Effects of copper(II) and copper oxides on THMs formation in copper pipe

Little is known about how the growth of trihalomethanes (THMs) in drinking water is affected in copper pipe. The formation of THMs and chlorine consumption in copper pipe under stagnant flow conditions were investigated. Experiments for the same water held in glass bottles were performed for comparison. Results showed that although THMs levels firstly increased in the presence of chlorine in copper pipe, faster decay of chlorine as compared to the glass bottle affected the rate of THMs formation. The analysis of water phase was supplemented by surface analysis of corrosion scales using X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDX). The results showed the scales on the pipe surface mainly consisted of Cu₂O, CuO and Cu(OH)₂ or CuCO₃. Designed experiments confirmed that the fast depletion of chlorine in copper pipe was mainly due to effect of Cu₂O, CuO in corrosion scales on copper pipe. Although copper(II) and copper oxides showed effect on THMs formation, the rapid consumption of chlorine due to copper oxide made THM levels lower than that in glass bottles after 4 h. The transformations of CF, DCBM and CDBM to BF were accelerated in the presence of copper(II), cupric oxide and cuprous oxide. The effect of pH on THMs formation was influenced by effect of pH on corrosion of copper pipe. When pH was below 7, THMs levels in copper pipe was higher as compared to glass bottle, but lower when pH was above 7.     

Trihalomethane formation during water disinfection in four water supplies in the Somes river basin in Romania

Background, aim and scope  

After the discovery of chloroform in drinking water, an extensive amount of work has been dedicated to the factors influencing the formation of halogenated disinfections by-products (DBPs). The disinfection practice can vary significantly from one country to another. Whereas no disinfectant is added to many water supplies in Switzerland or no disinfectant residual is maintained in the distribution system, high disinfectant doses are applied together with high residual concentrations in the distribution system in other countries such as the USA or some southern European countries and Romania. In the present study, several treatment plants in the Somes river basin in Romania were investigated with regard to chlorine practice and DBP formation (trihalomethanes (THMs)). Laboratory kinetic studies were also performed to investigate whether there is a relationship between raw water dissolved organic matter, residual chlorine, water temperature and THM formation.     

Factors influencing formation of trihalomethanes in drinking water with special reference to Swedish conditions

The trihalomethane (THM) concentrations in drinking water are greatly affected by the disinfection methods as well as the organic content of the water. The THM formation was shown to increase considerable during 24 hours. This indicates a higher concentration of THM at the consumers' tap compared to the levels in the outgoing water from the water work. The dosage ratio between chlorine and ammonium sulphate can be used to regulate the THM concentrations. Disinfection with a relatively high dosage of chlorine dramatically increase the THM level while the equal amount of chlorine dioxide produces trace concentrations of THM only. The relatively low THM concentrations in Swedish drinking water as compared to levels found in water from for example the USA may probably depend on the low chlorine dosage practiced in Sweden.     

Formation of Disinfection Byproducts (DBPs) in Surface Water Sources: Differential Ultraviolet (UV) Absorbance Approach

Chlorination for drinking water forms various disinfection byproducts (DBPs) of trihalomethanes (THMs) and haloacetic acids (HAAs). Chlorination has been attributed to the destruction of activated aromatic sites of the natural organic matter (NOM) predominantly at electron rich sites. Experiments with Istanbul surface waters showed that the magnitude of the decrease in the ultraviolet (UV) absorbance at 272 nm (UV₂₇₂) was an excellent indicator of destruction of these sites by chlorine. The main objective of the present study is to develop the differential UV₂₇₂ absorbance (ΔUV₂₇₂) related models for the prediction of the formation of THM, HAA, and their species in raw water samples from Terkos, Buyukcekmece, and Omerli lakes under different chlorination conditions. Significant factors affecting DBP formation in the raw waters were identified through numerical and graphical techniques. The R² values of the models varied between 0.94 and 0.97, indicating excellent predictive ability for THM₄ and HAA₉ in the raw waters. The models were validated using additional data. The results of this study concluded that addition of ΔUV₂₇₂ parameter into THM₄ and HAA₉ models make the prediction of these DBP compounds more precisely than those of DBP models developed in the past. A better understanding of these modeling systems will help the water treatment plant operators to minimize the DBP formation, providing a healthier and better drinking water quality as well as identifying strategies to improve water treatment and disinfection processes.     

Measurement of trihalomethanes in potable and recreational waters using solid phase micro extraction with gas chromatography-mass spectrometry

Solid phase micro extraction (SPME) was applied to the determination of selected trihalomethanes (THMs), chloroform, bromodichloromethane, dibromochloromethane, bromoform, in potable and recreational waters. The selected samples were environmentally significant due to mandatory limits imposed by regulatory agencies. Extraction of the analytes was performed using headspace SPME (fused silica fibre with a 100 microm poly(dimethylsiloxane coating) followed by thermal desorption at 220 degrees C and GC-MS analysis. A linear working range of 10-160 microg/l was established with relative standard deviations (%RSD) within the range, 0.9-19%. Limits of detection (LOD) were 1.0-2.8 microg/l. The highest THM concentration was 61.8 microg/l which was well within the proposed European Union directive of 100 microg/l. The total THMs determined in swimming pool waters ranged from 105-134 microg/l, with chloroform accounting for 84-86% of total THM.     

The fate of chlorine and organic materials in swimming pools

The fate of organic nitrogen and carbon introduced into a swimming pool by pool users has been studied using a 2.2 m(3) model pool. The study made use of a body fluid analogue (BFA), containing the primary endogenous organic amino compounds, and a soiling analogue represented by humic acid (HA). The system was used to examine the effect of organic loading and organic carbon (OC) sources (i.e. amino or HA) on the levels and speciation of the key chlorinated disinfection by-products of trihalomethanes (THMs) and chloramines under operating conditions representative of those employed on a full-scale pool.Results revealed OC, chloramines and THMs to all attain steady-state levels after 200-500 h of operation, reflecting mineralisation of the dosed OC. Steady-state levels of OC were roughly linearly dependent on dose rate over the range of operational conditions investigated and, as with the chloramine levels recorded, were in reasonable agreement with those reported for full-scale pools. THM levels recorded were somewhat lower than those found in real pools, and were dependent on both on pH carbon source: the THM formation propensity for the soling analogue was around eight times than of the BFA. Of the assayed by-products, only nitrate was found to accumulate, accounting for 4-28% of the dosed amino nitrogen. Contrary to previous postulations based on the application of Henry's Law, only insignificant amounts of the volatile by-products were found to be lost to the atmosphere.     

The occurrence of disinfection by-products in the drinking water of Athens,Greece

Application of chlorination for the disinfection of drinking water results in the formation of a wide range of organic compounds, called disinfection by-products (DBPs), which occur due to the reaction of chlorine with natural organic materials. The occurrence of DBPs was studied in samples from four drinking-water treatment plants (WTPs) and from the distribution network of Athens, Greece. Twenty-four compounds, which belong to different categories of DBPs, were monitored, including trihalomethanes (THMs), haloacetic acids (HAAs), haloacetonitriles (HANs), haloketones (HAKs), chloral hydrate (CH) and chloropicrin (CP). Sampling was performed monthly for a period of two years, from three different points at each WTP and from eight points atthe distribution network. Samples were analyzed by GC-ECD methods, which included pretreatment with liquid-liquid extraction for volatile DBPs and acidic methanol esterification for HAAs. The results of the analyses have shown the presence of disinfection by-products belonging to all categories studied in all water samples collected after prechlorination. The major categories of DBPs detected were THMs and HAAs, while the other volatile DBPs occurred at lower concentrations. The concentrations of DBPs did not in any case exceed the maximum contaminant levels (MCL) set by USEPA and WHO. However, monitoring these compounds needs to be continued, because their levels could increase due to changes in the quality of water entering the water treatment plants. Reduction of the concentrations of DBPs could be achieved by optimization of the chlorination conditions, taking into account the effect of time. Moreover, research on alternative disinfection methods (e.g. ozone, chlorine dioxide, chloramines) and their by-products should be conducted to evaluate their applicability in the case of the drinking water of Greece.     

Formation of nitrogenous disinfection by-products from pre-chloramination

A sampling survey investigated the formation of nitrogenous disinfection by-products (N-DBPs) and carbonaceous DBPs (C-DBPs) from pre-chloramination, an increasingly common treatment strategy in China for regulated C-DBP control, followed by subsequent conventional water treatment processes, i.e., coagulation, sedimentation, and filtration. Dihalogenated N-DBPs typically peaked in the summer and early autumn with a relatively higher temperature, with the maximum levels of dichloroacetamide (DCAcAm), dichloroacetonitrile (DCAN), bromochloroacetonitrile, dibromoacetonitrile and dichloroacetone at 1.8, 6.3, 6.0, 2.6 and 1.8 μg L⁻¹ in the finished water, respectively. Also, the levels of all the dichlorinated N-DBPs were correlated with the ratio of dissolved organic nitrogen (DON) to dissolved organic carbon, implying autochthonous DON played an essential role in the formation of these DBPs. In contrast, the yields of trihalogenated DBPs [chloroform (CF), trichloronitromethane (TCNM) and trichloroacetone (TCAce)] appeared not to be significantly affected by seasons. CF and DCAN were the dominant species in trihalomethanes (THMs) and dihaloacetonitriles (DHANs), respectively. Bromine was more readily incorporated into DHANs to form brominated DBPs than THMs during pre-chloramination. Although pre-chloramination can ensure the finished water to meet with the current Chinese THM regulatory limits, the increased levels of TCNM and TCAce may be a new water quality concern.     

Levels of perfluorochemicals in water samples from Catalonia,Spain: is drinking water a significant contribution to human exposure?

Background, aim, and scope  In recent years, due to a high persistence, biomagnification in food webs, presence in remote regions, and potential toxicity, perfluorochemicals (PFCs) have generated a considerable interest. The present study was aimed to determine the levels of perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), and other PFCs in drinking water (tap and bottled) and river water samples from Tarragona Province (Catalonia, Spain). Materials and methods  Municipal drinking (tap) water samples were collected from the four most populated towns in the Tarragona Province, whereas samples of bottled waters were purchased from supermarkets. River water samples were collected from the Ebro (two samples), Cortiella, and Francolí Rivers. After pretreatment, PFC analyses were performed by HPLC-MS. Quantification was done using the internal standard method, with recoveries between 68% and 118%. Results  In tap water, PFOS and PFOA levels ranged between 0.39 and 0.87 ng/L (0.78 and 1.74 pmol/L) and between 0.32 and 6.28 ng/L (0.77 and 15.2 pmol/L), respectively. PFHpA, PFHxS, and PFNA were also other detected PFCs. PFC levels were notably lower in bottled water, where PFOS could not be detected in any sample. Moreover, PFHpA, PFHxS, PFOA, PFNA, PFOS, PFOSA, and PFDA could be detected in the river water samples. PFOS and PFOA concentrations were between <0.24 and 5.88 ng/L (<0.48 and 11.8 pmol/L) and between <0.22 and 24.9 ng/L (<0.53 and 60.1 pmol/L), respectively. Discussion  Assuming a human water consumption of 2 L per day, the daily intake of PFOS and PFOA by the population of the area under evaluation was calculated (0.78–1.74 and 12.6 ng, respectively). It was found that drinking water might be a source of exposure to PFCs as important as the dietary intake of these pollutants. Conclusions  The contribution of drinking water (tap and bottled) to the human daily intake of various PFCs has been compared for the first time with data from dietary intake of these PFCs. It was noted that in certain cases, drinking water can be a source of exposure to PFCs as important as the dietary intake of these pollutants although the current concentrations were similar or lower than those reported in the literature for surface water samples from a number of regions and countries. Recommendations and perspectives  Further studies should be carried out in order to increase the knowledge of the role of drinking water in human exposure to PFCs.     

Probabilistic approach for health hazard assessment of trihalomethanes through successive showering events

Environmental Science and Pollution Research - Trihalomethanes (THMs) are common disinfection by-products in chlorinated tap waters. They can cause various cancers and non-cancer health hazards....     

Predictive model for disinfection by-product in Alexandria drinking water, northern west of Egypt

Chlorine has been utilized in the early stages of water treatment processes as disinfectant. Disinfection for drinking water reduces the risk of pathogenic infection but may pose a chemical threat to human health due to disinfection residues and their by-products (DBP) when the organic and inorganic precursors are present in water. In the last two decades, many modeling attempts have been made to predict the occurrence of DBP in drinking water. Models have been developed based on data generated in laboratory-scale and field-scale investigations. The objective of this paper is to develop a predictive model for DBP formation in the Alexandria governorate located at the northern west of Egypt based on field-scale investigations as well as laboratory-controlled experimentations. The present study showed that the correlation coefficient between trihalomethanes (THM) predicted and THM measured was R ²?=?0.88 and the minimum deviation percentage between THM predicted and THM measured was 0.8 %, the maximum deviation percentage was 89.3 %, and the average deviation was 17.8 %, while the correlation coefficient between dichloroacetic acid (DCAA) predicted and DCAA measured was R ²?=?0.98 and the minimum deviation percentage between DCAA predicted and DCAA measured was 1.3 %, the maximum deviation percentage was 47.2 %, and the average deviation was 16.6 %. In addition, the correlation coefficient between trichloroacetic acid (TCAA) predicted and TCAA measured was R ²?=?0.98 and the minimum deviation percentage between TCAA predicted and TCAA measured was 4.9 %, the maximum deviation percentage was 43.0 %, and the average deviation was 16.0 %.