A study on the distribution of chlorination by-products (CBPs) in treated water in Korea

Perspectives and understanding on the occurrence, toxicity and abatement technologies of disinfection by-products in drinking water

Disinfection by-products (DBPs) are one of the significant emerging contaminants that have caught the attention of researchers worldwide due to their pervasiveness. Their presence in drinking water, even in shallow concentrations (in levels of parts per billion), poses considerable health risks. Therefore, it is crucial to understand their kinetics to understand better their formation and persistence in the water supply systems. This manuscript demonstrates different aspects of research carried out on DBPs in the past. A systematic approach was adopted for the bibliographical research that started with choosing appropriate keywords and identifying the most relevant manuscripts through the screening process. This follows a quantitative assessment of the extracted literature sample, which included the most productive and influential journal sources, the most widely used keywords, the most influential authors active in the research domain, the most cited articles, and the countries most actively engaged in the research field. Critical observations on the literature sample led to the qualitative assessment, wherein the past and current research trends were observed and reported. Finally, we identified the essential gaps in the available literature, which further led to recommending the course ahead in the research domain. This study will prove fruitful for young and established researchers who are or wish to work in this emerging field of research.

Occurrence and spatio-temporal variability of halogenated acetaldehydes in full-scale drinking water systems

As the third largest group of identified disinfection by-products (DBPs) by weight, halogenated acetaldehydes (HALs), were monitored for one year at numerous locations in two full-scale drinking water systems applying an ozone-chlorine sequential disinfection strategy. The HALs that were targeted included four trihalogenated acetaldehydes (THALs): chloral hydrate (CH), bromodichloroacetaldehyde (BDCAL), dibromochloroacetaldehyde (DBCAL) and tribromoacetaldehyde (TBAL). Three dihalogenated acetaldehydes (DHALs) were also included: dichloroacetaldehyde (DCAL), bromochloroacetaldehyde (BCAL) and dibromoacetaldehyde(DBAL). In addition to various sampling points in two distribution networks, this study also investigated the formation of HALs during water treatment and for the first time, reports the formation of DBAL before chlorine is applied. Low bromide levels in source waters from both systems resulted in the rare detection of DBAL and TBAL. CH accounted for >50% of total HALs (HAL7) with DHALs accounting for as little as 10% of HAL7, presumably due to the use of ozone-chlorine instead of ozone-chloramine. In the presence of chlorine residuals and with increasing water residence times, most HALs continued to form, more readily in warm water than in cold water. However, the spatial and temporal patterns for each HAL differed depending on speciation (THAL vs. DHAL) and water temperature. Compared to the relatively stable bromine incorporation factor (BIF) of THMs in the distribution systems, the decreasing BIFs of HALs according to water residence time increases suggested that bromine-containing THMs are more stable than their corresponding HALs. Re-chlorination at the extremities of the distribution networks demonstrated a significant impact on the occurrence and speciation of DBPs. In both full-scale systems, water temperature was shown to be the biggest contributing factor to HAL formation. The strong correlations between THM levels and THAL levels make it possible to predict the occurrence of THALs based on THMs.

Effect modification of CPY2E1 and GSTZ1 genetic polymorphisms on associations between prenatal disinfection by-products exposure and birth outcomes

BACKGROUND

Prenatal disinfection by-products (DBPs) exposure is linked with adverse birth outcomes. Genetic susceptibility to DBP metabolism may modify the exposure-outcome associations.

OBJECT

To investigate whether CYP2E1 and GSTZ1 genetic polymorphisms modified the associations of prenatal DBP exposures with adverse birth outcomes.

METHODS

Two biomarkers of DBP exposures including trihalomethanes (THMs) in blood and trichloroacetic acid (TCAA) in urine were determined among 426 pregnant women from a Chinese cohort study. CYP2E1 (rs2031920, rs3813867, and rs915906) and GSTZ1 (rs7975) polymorphisms in cord blood were genotyped. Statistical interactions between prenatal DBP exposures and newborns CYP2E1 and GSTZ1 polymorphisms on birth outcomes (birth weight, birth length, and gestational age) were examined by multivariable linear regression with adjustment for potential confounders.

RESULTS

We found that newborns CYP2E1 genetic polymorphisms (rs2031920 and rs3813867) modified the associations of maternal blood THMs or urinary TCAA levels with birth outcomes. However, these interactions were nonsignificant after Bonferroni correction for multiple comparisons, except for the interaction between maternal blood BrTHMs [sum of dibromochloromethane (DBCM), bromodichloromethane (BDCM), and bromoform (TBM)] and newborns CYP2E1 gene rs2031920 polymorphisms on birth weight (P for interaction = 0.003).

CONCLUSION

Newborns genetic variations of CYP2E1 rs2031920 may modify the impacts of prenatal BrTHM exposure on birth weight. This finding needs to be further confirmed.

Presence and seasonal variation of trihalomethanes (THMs) levels in drinking tap water in Mostaganem Province in northwest Algeria

Background

The use of chlorine to disinfect water, produces various disinfection byproducts such as trihalomethanes (THMs). These compounds are formed when free available chlorine reacts with natural organic matter in raw water during water disinfection. Epidemiologic studies have shown an association between long-term exposure to THMs and an increased risk of cancer, all of them are suspected of having carcinogenic effects.

Aim

The aim of this study was to determine the presence of THMs in the drinking tap water of Mostaganem Province (Algeria) in order to assess the seasonal variation in trihalomethane levels in tap water and to identify the season of high risk to the consumer.

Methods

This analytical study was conducted in Mostaganem Province, Algeria in March, July, September and December 2015. Primarily, we proceeded to collect 30 samples from different areas of Mostaganem Province which were marked with a higher level of residual chlorine for the year 2015; secondly, we utilised the HS-SPME method for determination of trihalomethanes in drinking tap water over a period of four months. For comparison of trihalomethanes values, we used ANOVA.

Results

The results obtained show variability in total THM concentrations from one district to another, with a maximum of 198 μg/l recorded in the Achaacha district during July, but the lowest value 07.84 μg/l is noted at Salamandre city during the same period, noting that these values decrease progressively during the winter period.

Conclusion

Our drinking tap water samples include a large quantity of THMs with different concentrations, where the dibromochloromethane and the bromoform constitute the major portion of THMs.

Influences of NOM composition and bacteriological characteristics on biological stability in a full-scale drinking water treatment plant

The influences of natural organic matter (NOM) and bacteriological characteristics on the biological stability of water were investigated in a full-scale drinking water treatment plant. We found that prechlorination decreased the hydrophobicity of the organic matter and significantly increased the high-molecular-weight (MW) dissolved organic matter, such as biopolymers and humic substances. High-MW organic matter and structurally complex compounds are known to be relatively slowly biodegradable; however, because of the prechlorination step, the indigenous bacteria could readily utilise these fractions as assimilable organic carbon. Sequential coagulation and sedimentation resulted in the substantial removal of biopolymer (74%), humic substance (33%), bacterial cells (79%), and assimilable organic carbon (67%). Rapid sand and granular activated carbon filtration induced an increase in the low-nucleic-acid content bacteria; however, these bacteria were biologically less active in relation to enzymatic activity and ATP. The granular activated carbon step was essential to securing biological stability (the ability to prevent bacterial growth) by removing the residual assimilable organic carbon that had formed during the ozone treatment. The growth potential of Escherichia coli and indigenous bacteria were found to differ in respect to NOM characteristics. In comparison with E. coli, the indigenous bacteria utilised a broader range of NOM as a carbon source. Principal component analysis demonstrated that the measured biological stability of water could differ, depending on the NOM characteristics, as well as on the bacterial inoculum selected for the analysis.

Characterization of the precursors of trihalomethanes and haloacetic acids in the Yuqiao Reservoir in China

To identify the primary precursors of trihalomethanes and haloacetic acids in the Yuqiao Reservoir in China, dissolved organic matters in the source water were isolated and fractionated into five different fractions (with XAD resin), and both trihalomethane and haloacetic acid formation potentials in each fraction were analysed by liquid-liquid extraction and GC-ECD. The primary precursors of trihalomethanes and haloacetic acids were identified using the index of disinfection by-product formation potential and specific disinfection by-product formation potential. In addition, the relationship between the specific ultraviolet absorbance and the specific disinfection by-product formation potential was studied using correlation analysis. The results indicated that during the sampling period, the hydrophobic acids and hydrophilic matter are the primary organic fractions in the Yuqiao Reservoir, accounting for 27.6-40.9% and 21.2-32.5%, respectively. Among the five fractions, the hydrophobic acids had the highest disinfection by-product formation potential and specific disinfection by-product formation potential, indicating that the hydrophobic acids were the primary precursors of the disinfection by-products in the Yuqiao Reservoir. A correlation analysis indicates that the specific ultraviolet absorbance had a moderately positive correlation with the specific disinfection by-product formation potential; therefore, the specific ultraviolet absorbance can be a reference index to analyse the ability of organic matter to generate disinfection by-products.

Health risk assessment of exposure to organic matter from the use of reclaimed water in toilets

To estimate the carcinogenic and non-carcinogenic risks of six volatile organic compounds (VOCs) found in reclaimed water used for flushing toilets, a probabilistic health risk assessment based on Monte Carlo simulations was used. Before Monte Carlo simulations, the contaminant volatilization model was applied to estimate the concentration of the pollutants in air. Moreover, a questionnaire was used to acquire daily exposure time and the Batch Fit tool of Crystal Ball software was applied to find the best-fitting distribution of a part of the input parameters. The risk analysis indicated that the health risks from six VOCs were lower than the negligible risk level (1 × 10(-8)) in all cases, and the health risk for females was slightly higher than that for males. Overall, exposure to organic pollutants in reclaimed water during toilet flushing does not currently pose a significant carcinogenic risk to humans. In this study, we want to provide some information on the health risk from reclaimed water used for toilet flushing in China and hope that it will be useful to promote the application of reclaimed water in water-deficient areas.

Health risk assessment of inhalation exposure of irrigation workers and the public to trihalomethanes from reclaimed water in landscape irrigation in Tianjin, North China

To estimate the concentration in air and the cancer risk of irrigation workers and the public exposed to the total trihalomethanes (TTHMs) in reclaimed water used for landscape irrigation, a probabilistic health risk assessment was conducted through the integrated use of one-dimensional (1-D) and two-dimensional (2-D) Monte Carlo simulations. Before the 2-D simulation, a sensitivity analysis corresponding to the 1-D simulation was carried out to identity the factors most affecting the outputs. The results reveal that the TTHM concentration level and cancer risk for workers' exposure is much higher than that for public exposure in landscape irrigation. Moreover, the most influential factors are quite different for workers' exposure and public exposure. The 2-D Monte Carlo risk analysis result for the workers indicated that the lowest-risk, highest-risk and two critical points for irrigation height are 0.7 m, 1.53 m, 1.4m and 1.65 m when the mean value of the risk is selected as the reference statistic for risk management. Based on the risk assessment results, different measures can be suggested for the risk control of different populations. Furthermore, the influential variables should be better characterized to improve the accuracy of health risk assessment.

Occurrence of disinfection by-products in tap water distribution systems and their associated health risk

The concentrations of trihalomethanes (THMs), including chloroform, bromodichloromethane, dibromochloromethane, and bromoform, and haloacetic acids (HAAs; monochloroacetic acid, monobromoacetic acid, dibromoacetic acid, dichloroacetic acid, and trichloroacetic acid) were measured in tap waters passing through water distribution systems of six water treatment plants in Seoul, Korea, and their associated health risks from exposure to THMs through ingestion, dermal contact, and inhalation were estimated using a probabilistic approach. The concentration ranges for total THMs and HAA5 were 3.9-53.5 and <LOD-49.5 μg/L, respectively. Among DBPs, chloroform, bromodichloromethane, dichloroacetic acid, and trichloroacetic acid were the most frequently detected. Spatial and seasonal variations in concentrations of THMs and HAAs in the six water distribution systems were significant (P < 0.001).The mean lifetime cancer risks through ingestion, dermal contact, and inhalation during showering ranged as 7.23-10.06 × 10(-6), 2.19-3.63 × 10(-6), and 5.22-7.35 × 10(-5), respectively. The major exposure route to THMs was inhalation during showering. Sensitivity analysis showed that shower time and shower frequency had a great impact on the lifetime cancer risk by the exposure to THMs in tap water.

Occurrence, profiling and prioritization of halogenated disinfection by-products in drinking water of China

The occurrence of 28 disinfection by-products (DBPs), which were divided into 5 groups, in 70 drinking water treatment plants in 31 cities across China was investigated, and the toxic potency of each DBP group was calculated using mammalian cell toxicity data from previous studies for profiling. Of the 28 DBPs, 21 were detected with an average frequency of detection of 50%. Trihalomethanes (THM4) and haloacetic acids (HAAs) were the most predominant species, whose median concentration levels were at 10.53 and 10.95 μg L(-1), respectively. Two of four iodinated trihalomethanes (I-THMs) were detected, and the concentration of the I-THMs ranged from under the detection limit to 5.58 μg L(-1). The total concentration of haloacetonitriles (HANs) in different water samples ranged from under the limit of detection to 39.20 μg L(-1), with a median concentration of 1.11 μg L(-1). Two of four halonitromethanes (HNMs) were detected, and the maximum concentrations of chloronitromethane (CNM) and trichloronitromethane (TCNM) were 0.96 and 0.28 μg L(-1), respectively. HANs were found to be the most potent DBP group in terms of cytotoxicity, and HANs and HAAs had the same level of genotoxic potency. These results indicate that although at a low concentration level, the toxic potency of the unregulated HANs in drinking water may not be neglected.

The effects of subacute exposure of peracetic Acid on lipid peroxidation and hepatic enzymes in wistar rats

OBJECTIVES

This study was undertaken to determine the effect of subacute exposure of peracetic acid on lipid peroxidation and hepatic enzymes in Wistar rats.

METHODS

48 male animals in Treatment Group I, II and III received 0.2%, 2% and 20% peracetic acid daily for 2 and 4 weeks.

RESULTS

Serum malondialdehyde increased and Alanine Transaminase and Aspartate Transaminase decreased significantly in groups 2 and 3, compared to the control group. The malondialdehyde, Alanine Transaminase and Aspartate Transaminase with 0.2% and 2% doses of peracetic acid for 2 weeks do not lead to the alteration of malondialdehyde and enzyme activities.

CONCLUSION

This study demonstrated that the enhancement of malondialdehyde could provide an oxidative damage induced by disinfectant peroxidation at 20% and 2% doses at 2 and 4 weeks. The consumption of peroxidation with 20% for 2 weeks and 2% for 4 weeks can cause the increase of malondialdehyde and the decrease of enzyme activities, respectively.

Temporal variability in trihalomethane and haloacetic acid concentrations in Massachusetts public drinking water systems

Previous epidemiological studies in Massachusetts have reported a risk of adverse health outcomes in relation to disinfection by-product (DBP) exposures. Measurement error due to the use of indirect exposure surrogates can lead to misclassification bias in epidemiological studies; therefore, it is important to characterize exposure variability in these populations to assess the potential for exposure misclassification. We used 19,944 trihalomethane (THM) samples and 9291 haloacetic acid (HAA) samples collected in 201 public water systems (PWSs) in Massachusetts to examine temporal variability under different drinking water sources and disinfection types. Annual and seasonal variability was also examined in 46 PWSs with complete quarterly THM4 (i.e., the sum of 4 individual THMs) data from 1995 to 2004 and 19 PWSs with complete HAA5 (i.e., the sum of 5 individual HAAs) data from 2001 to 2004. The quarterly ratio of THM4 and HAA5 and correlations between THM4, HAA5 and individual DBP species were examined to determine the adequacy of using different exposure surrogates in epidemiological studies. Individual PWSs were used to examine monthly variability in relation to quarterly averages. Based on all available matched samples (n=9003) from 1995 to 2004 data, we found a correlation of 0.52 for THM4 and HAA5. The correlation was stronger among the 62 ground water systems (r(s)=0.62) compared to the 81 surface water (r(s)=0.45) and 40 mixed water (r(s)=0.39) systems. Mean THM4 levels were fairly stable over the 10-year study period for 46 PWSs including 39 PWSs that did not change disinfection. Large reductions (∼40 μg/L) in mean THM4 data were found among seven systems that switched from chlorination to alternative disinfectants. As expected, the highest mean THM4 values were detected for Quarter 3, while the lowest values were found in Quarter 1. The highest HAA5 values were detected in Quarters 2 and 3 and the lowest was found in Quarter 4. Data from four systems showed mean differences up to 66 μg/L (67% change) in successive months and by 46 μg/L compared to quarterly mean concentrations. Although longer-term disinfection by-product temporality may be minimal in this study population, the use of monthly average concentrations for exposure assessment may be needed for some PWSs to minimize misclassification of narrow critical periods of exposure in epidemiological studies.

Evaluating and elucidating the formation of nitrogen-contained disinfection by-products during pre-ozonation and chlorination

The effects of pre-ozonation on the formation of haloacetonitriles (HANs), trichloronitromethane (TCNM), and haloketones (HKs) during chlorination were evaluated. Ozone dose used in this study was 8.0, 10.0 and 25.0 mg O(3)/min. Results showed high UV(254) reduction (>80%) and relatively low dissolved organic carbon removal (40-70%) after ozonation, indicating that ozone might change significantly the chemical properties of natural organic matter presented in the raw water. Undesired ozonation by-products such as aldehydes and ketones were also formed during ozonation. At high ozone dose of 25.0 mg O(3)/min, the formation of dichloroacetonitrile and bromochloroacetonitrile were reduced significantly. Chlorination of the ozonated water formed high concentration of TCNM and HKs were 8-10 and 31-48 microg/L, respectively. It was also found that continuous hydrolysis at longer reaction time rapidly decreased the formation of HKs. Ozonation prior to chlorination practice exhibited a negative effect on TCNM and HKs reduction. A model based on the dissolved organic carbon and chlorine decay was developed not only for determining the reaction rate constants, e.g. formation and hydrolysis of HANs, HKs and TCNM, but also for interpreting the mechanisms of formation and hydrolysis for HANs, HKs and TCNM during the chlorination of natural organic matter.

Effects of crystalline structures and surface functional groups on the adsorption of haloacetic acids by inorganic materials

The effects of the crystalline structure and surface functional groups of porous inorganic materials on the adsorption of dichloroacetic acid (DCAA) were evaluated by using hexagonal mesoporous silicates (HMS), two surface functional group (3-aminopropyltriethoxy- and 3-mercaptopropyl-) modified HMSs, faujasite Y zeolite and activated alumina as adsorbents, and compared with powdered activated carbon (PAC). Selective adsorption of HAA(5) group was studied by comparing single and multiple-solute solution, including effect of common electrolytes in tap water. Adsorption capacities were significantly affected by the crystalline structure. Hydrogen bonding is suggested to be the most important attractive force. Decreasing the pH lower than the pH(zpc) increased the DCAA adsorption capacities of these adsorbents due to electrostatic interaction and hydrogen bonding caused by protonation of the hydronium ion. Adsorption capacities of HAA(5) on HMS did not relate to molecular structure of HAA(5). Common electrolytes did not affect the adsorption capacities and selectivity of HMS for HAA5, while they affected those of PAC.

Factors influencing disinfection by-products formation in drinking water of six cities in China

Based on the measured chemical and physical data in drinking water from six cities in China, the factors including total organic carbon (TOC), ultraviolet absorbance at 254 nm (UV(254)), pH, applied chlorine dosage, temperature, concentrations of bromide ion and several chemical elements which possibly affect the formation of trihalomethane (THM) and haloacetic acid (HAA) have been studied. The results showed that: in all factors, TOC and UV(254) have definite correlations with total THM, but have nonsignificant relationships with total HAA. In the studied pH range of 6.5-8.5 for drinking water, the total THM concentration increased with the increasing of pH value, but the total HAA concentration slightly decreased. A low but significant relationship (r=0.26, p<0.01) occurred between total THM and applied chlorine dosage. Similar relationship (r=0.21, p<0.01) was found between total HAA and applied chlorine dosage. When the water temperature was low, the variation of THMs and HAAs was little, but in warmer water, the concentration of THMs and HAAs varied quickly. The extent of bromine incorporation into the DBPs increases with increasing bromide ion concentration. Based on the effect of chemical elements for the DBPs remove effect, the polyferric chloride could be a preferred flocculant agent in waterworks.

Surveying the mutagenicity of tap water to elicit the effects of purification processes on Japanese tap water

The mutagenicity levels of tap water in Japan were surveyed using the Ames test. Tap water samples (179) were collected at 17 sampling sites located from the northern tip (Hokkaido) to the southern tip (Kagoshima Prefecture). The mutagenicity values ranged from under the detection limit to 3600 net rev x L(-1). The average mutagenicity was 1100 net rev x L(-1) and the levels were significantly higher in the wintertime than in the summertime. The average mutagenicity of each site ranged from under the detection limit to 2000 net rev x L(-1). There was no significant correlation of the mutagenicity with TOC, A(260) or THMs. The highest positive ratios of the Ames test and the umu test were 92% under the condition TA100-S9 and 9% under the condition NM2009-S9, respectively, which indicated that the Ames test has higher sensitivity for the test of tap water than the umu test. This survey incorporated the 1992-1993 survey. The comparison of these survey-results in a further study will reveal the improvement of Japanese tap water quality from the perspective of mutagenicity.

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 KMnO(4) 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 microg/L for chlorine, 23.3+/-2.2 microg/L for ozone/chlorine, and 58.2+/-1.7 microg/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 (7.77x10(-4)-1.36x10(-3)).

Human health risk assessment of chlorinated disinfection by-products in drinking water using a probabilistic approach

The presence of chlorinated disinfection by-products (DBPs) in drinking water is a public health issue, due to their possible adverse health effects on humans. To gauge the risk of chlorinated DBPs on human health, a risk assessment of chloroform (trichloromethane (TCM)), bromodichloromethane (BDCM), dibromochloromethane (DBCM), bromoform (tribromomethane (TBM)), dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) in drinking water was carried out using probabilistic techniques. Literature data on exposure concentrations from more than 15 different countries and adverse health effects on test animals as well as human epidemiological studies were used. The risk assessment showed no overlap between the highest human exposure dose (EXP(D)) and the lowest human equivalent dose (HED) from animal test data, for TCM, BDCM, DBCM, TBM, DCAA and TCAA. All the HED values were approximately 10(4)-10(5) times higher than the 95th percentiles of EXP(D). However, from the human epidemiology data, there was a positive overlap between the highest EXP(D) and the lifetime average daily doses (LADD(H)) for TCM, BDCM, DCAA and TCAA. This suggests that there are possible adverse health risks such as a small increased incidence of cancers in males and developmental effects on infants. However, the epidemiological data comprised several risk factors and exposure classification levels which may affect the overall results.

Occurrence of disinfection by-products in low DOC surface waters in Turkey

A total of 29 surface waters from different regions of Turkey were sampled once a month during 2004. Filtered raw water samples were characterized, chlorinated and the concentrations of disinfection by-products (DBPs) were measured. All waters were low in DOC ranging from 0.91 to 4.42 mg/L. The range of annual average trihalomethanes (THMs) and haloacetic acids (HAAs) concentrations in all waters was 21-189 and 18-149mug/L, respectively. Total mass contributions of halides in THMs and HAAs to absorbable organic halides (AOX) ranged between 10 and 56% in all waters on annual average basis, indicating that significant amounts of other DBPs are being formed in the majority of the tested waters. A strong linear correlation was obtained between the concentrations of THMs and HAAs. Rather poor correlations were found for THMs-AOX and HAAs-AOX levels. For both THMs and HAAs, chlorinated species dominated over brominated ones since the majority of water sources had very low bromide levels. While chloroform and trichloroacetic acid were the major THM and HAA compounds, respectively; the extent of formation and speciation of DBPs varied greatly by season and water source. No consistent general trends were observed in terms of seasonal variations in DBP levels, suggesting that the characteristics of NOM moieties and their chlorine reactivity vary by season in almost all waters tested.

Risk assessment on disinfection by-products of drinking water of different water sources and disinfection processes

The occurrences of trihalomethanes (THMs) and haloacetics (HAAs) in the water supply in Beijing and Canada were investigated. The concentrations of THMs and HAAs in Beijing and Canada were below the maximum contaminant levels specified by the USEPA and WHO standards. The multi-pathway risk assessment (assessed through oral ingestion, dermal absorption and inhalation exposure to drinking water) was used to assess the cancer risk and the hazard index of THMs and HAAs from fifteen waterworks in Beijing, China and three treatment plants using different disinfection processes in Canada. Residents in Beijing and residents who were served by three treatment plants using different disinfection processes in Canada had a higher risk of cancer through oral ingestion than through the other two pathways. The cancer risk resulted from disinfection by-products (DBPs) was 8.50E-05(for males), 9.25E-05(for females) in Beijing, China, while it was 1.18E-04, 1.44E-04 in Canada. The risk was higher when water treatment plants used surface water source than when they used ground water source and mixture water source in Beijing. The risk showed different changes in three treatment plants using different disinfection processes in Canada. The lifetime cancer risk for THMs followed the order: Plant 2>Plant 1>Plant 3. And, the lifetime cancer risk for HAAs was: Plant 1>Plant 2>Plant 3.

Chemometrics in monitoring spatial and temporal variations in drinking water quality

This case study reports multivariate techniques applied for the evaluation of temporal/spatial variations and interpretation of monitoring data obtained by the determination of chloro/bromo disinfection by-products in drinking water at 12 locations in the Gdańsk area (Poland), over the period 1993-2000. The complex data matrix (1756 observations) was treated with various multivariate techniques. Cluster analysis (CA) was successful, yielding two different groups of similarity reflecting different types of drinking water supplied (surface and groundwater). The locations supplied in general with groundwater could be further classified into two subgroups, depending on whether the groundwater was mixed with surface water or not. Analysis of variance (ANOVA) was used to classify and thus confirm the groups found by means of cluster analysis and proved the existence of statistically significant differences between the concentration levels of CHCl3, CHBrCl2+C2HCl3, CHBr2Cl, and CH2Cl2 in the samples collected. Of all the variables evaluated, only three were characterized by statistically significant correlations (CHCl3, CHBrCl2+C2HCl3, CHBr2Cl). The analysis of correlation coefficients revealed that chloroform formed as the main chlorinated disinfection by-product and, furthermore, the natural presence of bromide in water (both ground and surface) results in the formation of brominated disinfection by-products (DBPs). Temporal variations of volatile organic chlorinated compounds (VOCls) were also evaluated by multidimensional ANOVA. Observation of temporal changes in the concentration of VOCls at the location supplied with both surface and groundwater reveals a steady improvement in drinking water quality. In general, the study shows the importance of drinking water monitoring in connection with simple but powerful statistical tools to better understand spatial and temporal variations in water quality.

In vitro potential genotoxic effects of surface drinking water treated with chlorine and alternative disinfectants

A battery of in vitro short-term tests revealing different genetic end-points was set up in order to study surface-water genotoxicity after disinfection with different biocides: sodium hypochlorite (NaClO), chlorine dioxide (ClO(2)) and peracetic acid (PAA). The surface water both before and after disinfection was concentrated by adsorption on C(18) silica cartridges and the concentrates containing non-volatile organics were divided into different portions for chemical analyses and biological assays. The following in vitro tests were conducted on the water concentrates dissolved in DMSO: the Salmonella mutagenicity assay with S. typhimurium strains TA98 and TA100; the SOS Chromotest with Escherichia coli, the Microtox and Mutatox assays with Vibrio fischeri; and gene conversion, point mutation and mitochondrial DNA mutability assays with D7 diploid Saccharomices cerevisiae strain. The results show that the SOS Chromotest and the yeast assays are highly sensitive in detecting genotoxicity. The surface-water extracts were very often toxic to most of the test organisms considered, partially masking their potential mutagenic activity. Therefore, the assays with E. coli and with S. cerevisiae are more likely to show a mutagenic effect because these organisms are generally less sensitive to most toxic compounds. Among the tested disinfectants, NaClO and ClO(2) increased water genotoxicity, whereas PAA was able to slightly reduce raw water activity. However, because the organic compounds in the lake water varied with the season of the year, the disinfection processes, at times, both increased and decreased the raw water activity.

Trihalomethanes and associated potential cancer risks in the water supply in Ankara, Turkey

The occurrence of trihalomethanes (THMs) in the water supply in the Ankara, Turkey was investigated. Total THMs and total organic carbon measurements were carried seasonally in the samples collected form 22 different districts along with the samples taken from the Ivedik Water Treatment Plant serving 90% of the city. The average summer nonpurgeable organic carbon (NPOC) concentration in the raw water was 4.2 mg/L, and the NPOC removal achieved in the treatment plant was 31%. The concentration of total THMs ranged from 25 to 74 microg/L, from 28 to 73 microg/L, and from 25 to 110 microg/L in winter, spring, and summer, respectively. In all of the samples chloroform existed at the highest concentrations, while bromoform was almost absent. The total THM concentrations were highest in summer for all districts. However, none of the concentrations detected exceeded the USEPA's Stage I limit of 80 microg/L and the EU's limit of 100 microg/L. However, the total THM level in 64% of the districts exceeded the USEPA's Stage II limit of 40 microg/L. The risk estimations carried out indicated that each year 1 of the 5 million Ankara residents could get cancer from the daily intake of water, mainly because of exposure to chloroform through oral ingestion.

Comet and micronucleus assays in zebra mussel cells for genotoxicity assessment of surface drinking water treated with three different disinfectants

The aim of this research was to study the influence of classic (sodium hypochlorite and chlorine dioxide) and alternative (peracetic acid [PAA]) disinfectants on the formation of mutagens in surface waters used for human consumption. For this proposal, in vivo genotoxicity tests (Comet and micronucleus assay) were performed in an experimental pilot plant set up near Lake Trasimeno (Central Italy). The effects were detected in different tissues (haemocytes for the Comet assay and gills for the micronucleus test [MN]) of Dreissena polymorpha exposed in experimental basins supplied with lake water with/without the different disinfectants. Specimen collection was performed before disinfectant input for both tests and after the start of disinfection (3 h and 20 days for the Comet assay and 10 and 20 days for micronucleus test, respectively) to assess short- and long- term exposure effects during three sampling campaigns (October 2000, February 2001, and June 2001). Seasonal differences in baseline levels of DNA migration and micronucleus frequency were observed. Raw water quality modulation on disinfection by-product formation was shown. The results of the micronucleus and Comet assays on zebra mussel cells after in situ exposure to water disinfected with the two chlorinated compounds clearly indicate DNA/by-product interaction. PAA did not induce either clastogenic/aneugenic effects or DNA damage on this bioindicator.

[Trihalomethanes in the drinking water of Carabobo State, Venezuela]

OBJECTIVE

Disinfection of water with chlorine in water treatment plants leads to the formation of trihalomethanes (THMs). These compounds are associated with adverse health effects. The aim of this study was to analyze THM concentrations in the water provided for human consumption in the two main water treatment systems of Carabobo State: the Alejo Zuloaga plant and the Pao-Cachinche reservoir, which form the Central Regional System I (CRS I), and the Lucio Baldo Soules plant and the Pao-La Balsa reservoir, which form the Central Regional System II (CRS II).

METHODS

We analyzed 144 water samples collected in 6 samplings carried out in 2000 and 2001. THM concentrations were determined by gas chromatography using the headspace technique. The concentrations of the following THMs were measured: chloroform (CHCl3), bromoform (CHBr3), chlorodibromomethane (CHBr2Cl) and bromodichloromethane (CHCl2Br).

RESULTS

The concentration of total THMs was between 47.84 g/l and 94.23 g/l. CHCl3 was the most commonly formed compound representing 83% of all THMs in the CRS I and 82% in the CRS II. The concentrations of total THMs in the CRS I, specifically in the Baja and San Diego networks, were significantly higher (p < 0.05) than permissible levels set by the American Environmental Protection Agency (80 g/l) for the sum of all four THMs.

CONCLUSIONS

The results show that in the area studied there is a risk of adverse health effects due to THMs in drinking water, especially in the Baja and San Diego networks.