We investigated the concentration of trihalomethanes （THMs） in tap water and swimming pool water in the area of the Nakhon Path- om Municipality during the period April 2005-March 2006. The concentrations of total T...We investigated the concentration of trihalomethanes （THMs） in tap water and swimming pool water in the area of the Nakhon Path- om Municipality during the period April 2005-March 2006. The concentrations of total THMs, chloroform, bromodichloromethane, dibromochloromethane and bromoform in tap water were 12.70-41.74, 6.72-29.19, 1.12-11.75, 0.63-3.55 and 0.08-3.40 μg/L, respectively, whereas those in swimming pool water were 26.15-65.09, 9.50-36.97, 8.90-18.01, 5.19-22.78 and ND-6.56 μg/L, respectively. It implied that the concentration of THMs in swimming pool water was higher than those in tap water, particularly, brominated-THMs. Both tap water and swimming pool water contained concentrations of total THMs below the standards of the World Health Organization （WHO）, European Union （EU） and the United States Environmental Protection Agency （USEPA） phase Ⅰ, but 1 out of 60 tap water samples and 60 out of 72 swimming pool water samples contained those over the Standard of the USEPA phase Ⅱ. From the two cases of cancer risk assessment including Case Ⅰ Non-Swimmer and Case Ⅱ Swimmer, assessment of cancer risk of nonswimmers from exposure to THMs at the highest and the average concentrations was 4.43×10^-5 and 2.19×10^-5, respectively, which can be classified as acceptable risk according to the Standard of USEPA. Assessment of cancer risk of swimmers from exposure to THMs at the highest and the average concentrations was 1.47×10^-3 and 7.99×10^-4, respectively, which can be classified as unacceptable risk and needs to be improved. Risk of THMs exposure from swimming was 93.9%-94.2% of the total risk. Cancer risk of THMs concluded from various routes in descending order was： skin exposure while swimming, gastro-intestinal exposure from tap water intake, and skin exposure to tap water and gastro-intestinal exposure while swimming. Cancer risk from skin exposure while swimming was 94.18% of the total cancer risk.展开更多
Addition of H2O2 has been employed to repress bromate formation during ozonation of bromide-containing source water. However, the addition of H2O2 will change the oxidation pathways of organic compounds due to the gen...Addition of H2O2 has been employed to repress bromate formation during ozonation of bromide-containing source water. However, the addition of H2O2 will change the oxidation pathways of organic compounds due to the generation of abundant hydroxyl radicals, which could affect the removal efficacy of trihalomethane precursors via the combination of ozone and biological activated carbon （O3-BAC）. In this study, we evaluated the effects of H2O2 addition on bromate formation and trihalomethane formation potential （THMFP） reduction during treatment of bromide-containing （97.6-129.1 μg/L） source water by the O3-BAC process. At an ozone dose of 4.2 mg/L, an H2O2/O3 （g/g） ratio of over 1.0 was required to maintain the bromate concentration below 10.0 μg/L, while a much lower H2O2/O3 ratio was sufficient for a lower ozone dose. An H2O2/O3 （g/g） ratio below 0.3 should be avoided since the bromate concentration will increase with increasing H2O2 dose below this ratio. However, the addition of H2O2 at an ozone dose of 3.2 mg/L and an H2O2/O3 ratio of 1.0 resulted in a 43% decrease in THMFP removal when compared with the O3-BAC process. The optimum H2O2/O3 （g/g） ratio for balancing bromate and trihalomethane control was about 0.7-1.0. Fractionation of organic materials showed that the addition of H2O2 decreased the removal efficacy of the hydrophilic matter fraction of DOC by ozonation and increased the reactivity of the hydrophobic fractions during formation of trihalomethane, which may be the two main reasons responsible for the decrease in THMFP reduction efficacy. Overall, this study clearly demonstrated that it is necessary to balance bromate reduction and THMFP control when adopting an H2O2 addition strategy.展开更多
Organic matter is known to be the precursor of numerous chlorination by-products. Organic matter in the secondary effluent from the Wenchang Wastewater Treatment Plant （Harbin, China） was physically separated into t...Organic matter is known to be the precursor of numerous chlorination by-products. Organic matter in the secondary effluent from the Wenchang Wastewater Treatment Plant （Harbin, China） was physically separated into the following fractions： particulate organic carbon （1.2-0.45 μm）, colloidal organic carbon （0.45-0.1 μm）, fine colloidal organic carbon （0.1-0.025 μm）, and dissolved organic carbon （DOC） （〈 0.025 μm）. Moreover, 〈 0.45 μm fraction was chemically separated into hydrophobic acid （HPO-A）, hydrophobic neutral （HPO-N）, transphilic acid （TPI-A）, transphilic neutral （TPI-N）, and hydrophllic fraction （HPI）. The chlorine reactivity of these organic fractions obtained from both size and XAD fractionations were evaluated. The structural and chemical compositions of the HPO-A, HPO-N, TPI-A, and TPI-N isolates were characterized using elemental analysis （C, H, O, and N）, Fourier transform infrared spectroscopy （FT-IR）, and proton nuclear magnetic resonance spectroscopy （1H-NMR）. Results showed that DOC was dominant in terms of total concentration and trihalomethane formation potential （THMFP）, and there was no statistical difference in both specific THMFP （STHMFP） and specific ultraviolet light absorbance among the 0.45, 0.1, and 0.025 ixm filtrates. HPO-A had the highest STHMFP compared to other chemical fractions. HPO-A, HPO-N, TPI-A, and TPI-N contained 3.02%-3.52% of nitrogen. The molar ratio of H/C increased in the order of HPO-A 〈 HPO-N 〈 TPI-A 〈 TPI-N. The O/C ratio was relatively high for TPI-N as compared to those for the other fractions. ^1H-NMR analysis of the four fractions indicated that the relative content of aromatic protons in HPO-A was significantly higher than those in the others. The ratio of aliphatic to aromatic protons increased in the order of HPO-A 〈 HPO-N 〈 TPI-A 〈 TPI-N. FT-IR analysis of the four fractions showed that HPO-A had greater aromatic C=C content whereas HPO-N, TPI-A, and TPI-N had greater aliphatic C-H content. TPI-N contained more oxygen-containing functional groups than the other fractions.展开更多
For the system of water samples collected from Yangtze River,the effects of seasonal variation and Fe（III） concentrations on the formation and distribution of trihalomethanes （THMs） during chlorination have been i...For the system of water samples collected from Yangtze River,the effects of seasonal variation and Fe（III） concentrations on the formation and distribution of trihalomethanes （THMs） during chlorination have been investigated.The corresponding lifetime cancer risk of the formed THMs to human beings was estimated using the parameters and procedure issued by the US EPA.The results indicated that the average concentration of THMs （100.81 μg/L） in spring was significantly higher than that in other seasons,which was related to the higher bromide ion concentration resulted from the intrusion of tidal saltwater.The total cancer risk in spring reached 8.23 × 10 ？5 and 8.86 × 10 ？5 for males and females,respectively,which were about two times of those in summer under the experimental conditions.Furthermore,it was found that the presence of Fe（III） resulted in the increased level of THMs and greater cancer risk from exposure to humans.Under weak basic conditions,about 10% of the increment of THMs from the water samples in spring was found in the presence of 0.5 mg/L Fe（III） compared with the situation without Fe（III）.More attention should be given to the effect of the coexistence of Fe（III） and bromide ions on the risk assessment of human intake of THMs from drinking water should be paid more attention,especially in the coastland and estuaries.展开更多
Reactivity of chlorine towards hydrophobic groups present in natural organic matter（NOM）provokes the formation of carcinogenic disinfection byproducts such as trihalomethanes in chlorinated water. The present study ...Reactivity of chlorine towards hydrophobic groups present in natural organic matter（NOM）provokes the formation of carcinogenic disinfection byproducts such as trihalomethanes in chlorinated water. The present study aimed to investigate the variations in coagulant activity of alum using two different bioflocculants（coagulant aid） namely, Moringa oleifera and Cyamopsis tetragonoloba for the removal of hydrophobic fractions of NOM and subsequent chlorine consumption by treated water. Effect of dual coagulants on trihalomethane surrogate parameters such as total organic carbon, dissolved organic carbon, UV absorbing materials and prominent hydrophobic species such as phenolic groups along with aromatic chromophores, polyhydroxy aromatic moiety have also been studied. The concept of differential spectroscopy and absorbance slope index has been employed to understand the combined effects of alum-bioflocculants on the reactivity of NOM with chlorine. Our result shows that the combination of alum and C. tetragonoloba is more efficient for reducing trihalomethane surrogates from chlorinated water as compared to M. oleifera. C. tetragonoloba elicited synchronized effects of sweep coagulation and particle bridging-adsorption which eventually facilitated efficient removal of hydrophobic fractions of NOM. The variation in the mechanistic approach of bioflocculants was due to the presence of cationic charge on M. oleifera and adhesive property of C. tetragonoloba.展开更多
The effects of the concentration of dissolved total organic carbon (TOC), the TOC/Br- ratio, bromide ion levels, the chlorine to ammonia-N ratio (Cl:N), the monochloramine dose and the chlorine dose on the formation o...The effects of the concentration of dissolved total organic carbon (TOC), the TOC/Br- ratio, bromide ion levels, the chlorine to ammonia-N ratio (Cl:N), the monochloramine dose and the chlorine dose on the formation of trihalomethanes (THMs) (including chloroform, bromodichloromethane, chlorodibromomethane, and bromoform) from chlorination were investigated using aqueous humic acid (HA) solutions. The profile of the chloramine decay was also studied under various bromide ion concentrations. Monochloramine decayed in the presence of organic material and bromide ions. The percentage of chloroform and brominated THMs varied according to the TOC/Br- ratio. Total THMs (TTHMs) formation increased from 112 to 190 μg/L with the increase concentrations of bromide ions from 0.67 to 6.72 mg/L, but the chlorine-substituted THMs were replaced by bromine-substituted THMs. A strong linear correlation was obtained between the monochloramine dose and the formation of THMs for Cl:N ratios of 3:1 and 5:1. These ratios had a distinct effect on the formation of chloroform but had little impact on the formation of bromodichloromethane or chlorodibromomethane. The presence of bromide ions increased the rate of monochloramine decay.展开更多
In a sanitation process of drinking water, carbon from the organic matter reacts with chlorine, forming by-products, among which are trihalomethanes (THM). These substances are carriers of mutagenic and can-cerogenic ...In a sanitation process of drinking water, carbon from the organic matter reacts with chlorine, forming by-products, among which are trihalomethanes (THM). These substances are carriers of mutagenic and can-cerogenic potential and hence should be removed in drinking water treatment. Since the natural organic mat-ters are precursors of THM formation, their removal from the water decreases the concentration of THMs. The THM forming potential is the most reliable indicator in evaluation of organic matter removal during drinking water treatment processes. The results have shown that the reaction producing THMs follows sec-ond order kinetics. The second order rate constant ranged from 0.024 M-1s-1 to 0.065 M-1s-1 at 22 °C and pH = 8.2 for 96 hours. The removal of 78.4% of natural organic matter, by adsorption on anionic exchange res-ins, resulted in the THM forming potential reduction by 63.1%. Various fractions of natural organic matter differ in their reactivity with chlorine, which is important when it comes to selection of the adsorption me-dium in the drinking water treatment processes.展开更多
The use of seawater for industrial cooling is a vital technology that poses some of the most profound environmental impact on the water quality in the Arabian Gulf. Biocide (chlorine) is added to the seawater to contr...The use of seawater for industrial cooling is a vital technology that poses some of the most profound environmental impact on the water quality in the Arabian Gulf. Biocide (chlorine) is added to the seawater to control biofouling of the cooling system. This added chlorine reacts with bromide and other chemicals naturally exist in the water to form a wide range of oxidants. Regrettably, reactions between the residual oxidants and natural organic matter in the water lead to formation of toxic halogenated organic compounds that have detrimental effects on the environment when they are discharged into the Gulf. This paper describes the formation of trihalomethanes (THMs) in seawater cooling systems. Results of kinetic experiments have shown that concentrations of THMs increased rapidly with time during the first half hour. Chlorination of seawater has shown significant increase in total THMs (TTHMs) and in bromoform concentrations. Rapid decrease of UV absorbance at 254 nm was also observed during seawater chlorination which is indicative of natural organic matter degradation into small organic molecules including THMs and other by-products. The increase in chlorine dose was accompanied with an increase in TTHMs and bromoform concentrations. Linear relationships between total chlorine concentration and both final TTHMs and bromoform concentrations were established. First order exponential decay and exponential associate functions were developed to correlate chlorine dose with formed THMs.展开更多
Bottled water consumption is increasing worldwide, despite its huge economic and environmental cost. We aim to describe personal and tap water quality determinants of bottled water use in the city of Barcelona. This c...Bottled water consumption is increasing worldwide, despite its huge economic and environmental cost. We aim to describe personal and tap water quality determinants of bottled water use in the city of Barcelona. This cross-sectional study used data from the Health Survey of Barcelona in 2006（N = 5417 adults）. The use of bottled water to drink and to cook was evaluated in relation to age, gender, educational level, district and levels of trihalomethanes（THMs）, free chlorine, conductivity, chloride, sodium, p H, nitrate and aluminium in municipal tap water using Robust Poisson Regression. The prevalence of bottled water use to drink and cook was 53.9% and 6.7%, respectively. Chemical parameters in water had a large variability（interquartile range of THMs concentrations： 83.2–200.8 μg/L）and were correlated between them, except aluminium. Drinking bottled water increased with educational level, while cooking with bottled water was higher among men than among women and decreased with age. After adjusting by these personal determinants, a dose–response relationship was found between concentrations of all chemicals except aluminium in tap water and bottled water use. The highest association was found for THMs,with a Prevalence Ratio of 2.00（95%CI = 1.86, 2.15） for drinking bottled water and 2.80（95%CI = 1.72, 4.58） for cooking with bottled water, among those with 〉 150 μg/L vs. 〈 100 μg/L THMs in tap water. Conclusion： More than half of Barcelona residents regularly drank bottled water, and the main determinant was the chemical composition of tap water,particularly THM level.展开更多
To ensure the safety of drinking water,ozone (O3) has been extensively applied in drinking water treatment plants to further remove natural organic matter (NOM).However,the surface water and groundwater near the coast...To ensure the safety of drinking water,ozone (O3) has been extensively applied in drinking water treatment plants to further remove natural organic matter (NOM).However,the surface water and groundwater near the coastal areas often contain high concentrations of bromide ion (Br-).Considering the risk of bromate (Br O3-) formation in ozonation of the sand-filtered water,the inhibitory efficiencies of hydrogen peroxide (H2O2) and ammonia(NH3) on Br O3-formation during ozonation process were compared.The addition of H2O2effectively inhibited Br O3-formation at an initial Br-concentration amended to 350μg/L.The inhibition efficiencies reached 59.6 and 100%when the mass ratio of H2O2/O3was 0.25and>0.5,respectively.The UV254and total organic carbon (TOC) also decreased after adding H2O2,while the formation potential of trihalomethanes (THMs FP) increased especially in subsequent chlorination process at a low dose of H2O2.To control the formation of both Br O3-and THMs,a relatively large dose of O3and a high ratio of H2O2/O3were generally needed.NH3addition inhibited Br O3-formation when the background ammonia nitrogen(NH3–N) concentration was low.There was no significant correlation between Br O3-inhibition efficiency and NH3dose,and a small amount of NH3–N (0.2 mg/L) could obviously inhibit Br O3-formation.The oxidation of NOM seemed unaffected by NH3addition,and the structure of NOM reflected by synchronous fluorescence (SF) scanning remained almost unchanged before and after adding NH3.Considering the formation of Br O3-and THMs,the optimal dose of NH3was suggested to be 0.5 mg/L.展开更多
Sulfonamides are used in human therapy, animal husbandry and agriculture but are not easily biodegradable, and are often detected in surface water. Sulfamethazine （SMZ） and sulfadiazine （SDZ） are two widely used s...Sulfonamides are used in human therapy, animal husbandry and agriculture but are not easily biodegradable, and are often detected in surface water. Sulfamethazine （SMZ） and sulfadiazine （SDZ） are two widely used sulfonamide antibiotics that are used heavily in agriculture. In this study, they were degraded in an aqueous system by chlorination after pre-oxidation with ferrate（VI） （FeVIO2-, Fe（VI））, an environmentally friendly oxidation technique that has been shown to be effective in degrading various organics. The kinetics of the degradation were determined as a function of Fe（VI） （0-1.5 mg/L）, free chlorine （0-1.8 mg/L） and temperature （15- 35℃）. According to the experimental results, SMZ chlorination followed second-order kinetics with increasing Fe（VI） dosage, and the effect of the initial free chlorine concentration on the reaction kinetics with pre-oxidation by Fe（VI） fitted a pseudo-first order model. The rate constants of SDZ and SMZ chlorination at different temperatures were related to the Arrhenius equation. Fe（VI） could reduce the levels of THMs formed and the toxicity of the sulfonamide degradation systems with Fe（VI） doses of 0.5-1.5 mg/L, which provides a reference for ensuring water quality in drinking water systems.展开更多
The mechanism of activated carbon fiber (ACF) adsorption trihalomethanes (THMs) was studied. It was found that ACF adsorption THMs was exothermic, the physico-adsorption principally, but not a complete monolayer adsor...The mechanism of activated carbon fiber (ACF) adsorption trihalomethanes (THMs) was studied. It was found that ACF adsorption THMs was exothermic, the physico-adsorption principally, but not a complete monolayer adsorption. The adsorptive capacities of ACF increased as the four species of THMs became more hydrophobic, and as the chlorine atoms in CHCls were substituted by more bromine atoms. The result of fixed-bed reactor adsorption was fitted to that of isotherm experiments.展开更多
An effective technology in controlling trihalomethanes （THMs） formation in the case of large amounts of bromide presenting was proposed, and the water of River Huang seriously polluted by bromide in winter in Tianji...An effective technology in controlling trihalomethanes （THMs） formation in the case of large amounts of bromide presenting was proposed, and the water of River Huang seriously polluted by bromide in winter in Tianjin City was studied. The THMs formation characteristics during prechloramination using preformed chloramines and converted chloramines were studied through jar tests. Results show that, in prechloramination process, the formation of THMs by preformed chloramines is very few, while that by converted ehloramines is a little higher. And the formation of THMs, especially Br^- substituted THMs, increases with the increase of time and Cl2：N ratio as well as the decrease of pH. The result obtained in a pilot plant shows that compared with prechlorination, the prechloramination process can efficiently control the formation of THMs, especially the Br^- substituted species. With equal chlorine dosage, the prechloramination can maintain a larger chlorine residue which offece, a larger CT value than prechlorination.展开更多
Glycine(Gly),cysteine(Cys),aspartic acid(Asp),leucine(Leu),lysine(Lys),and methyl amine(MA) were chosen as typical nitrogenous compounds,and the effects of them on trihalomethanes (THMs) formation and chlorine demand ...Glycine(Gly),cysteine(Cys),aspartic acid(Asp),leucine(Leu),lysine(Lys),and methyl amine(MA) were chosen as typical nitrogenous compounds,and the effects of them on trihalomethanes (THMs) formation and chlorine demand were performed on filtrated water. Results show that the nitrogenous compounds enhance THMs formation,and the increased levels are controlled by characteristics and the concentration of nitrogenous compounds. The increase in THMs formation follows the order of Asp(126 μg/L)>Cys(119 μg/L)>MA(106 μg/L)>Lys(97 μg/L)≈Gly(96 μg/L)>Leu(80 μg/L)(while nitrogenous compounds=1.0 mg/L,and background THMs=60 μg/L). The increase in chlorine demand is approximately proportionate to the content of nitrogenous compounds,which illustrates that the increase is mainly caused by the reaction of nitrogenous compounds with chlorine. And the increase in chlorine demand follows the order of Cys(27.8 mg/L)>Asp(22.6 mg/L)=Gly(22.6 mg/L)>Lys(21.6 mg/L)>MA(14.1 mg/L)>Leu(11.8 mg/L) (while nitrogenous compounds=1.0 mg/L,and background chorine demand=1.8 mg/L). The mechanisms of nitrogenous compounds enhancing THMs formation are summ the increase of chlorine demand raising THMs formation in reaction of NOM with chlorine,and the THMs formation in chlorination of nitrogenous compounds themselves.展开更多
The formation of brominated trihalomethanes (THMs-Br) which is proved more carcinogenic than their chlorinated analogues reported was very different at various water qualities.This study was performed to assess the ef...The formation of brominated trihalomethanes (THMs-Br) which is proved more carcinogenic than their chlorinated analogues reported was very different at various water qualities.This study was performed to assess the effects of water quality parameters (bromide concentration,pH value and ammonia concentration),chlorination conditions (chlorine dose,reaction time) and ratios of Br-/DOC and Br-/Cl2 consumption on the formation and distribution of THMs-Br in chlorination.The results showed good correlation between the bromine incorporation factor (BIF) n(Br) and Br-/Cl2 consumption ratio.The formation of total THM (TTHM) was found to decrease with increasing ammonia concentration but to increase with bromide concentration and pH value.The n(Br) trends were significantly affected by the presence of bromide concentration.The effects on the molar yields of THMs were more strongly influenced by bromide concentration and dissolved organic carbon (DOC) concentration than pH value and natural organic matter (NOM) source.High Br-/DOC and Br-/Cl2 favor the formation of THMs-Br over chlorinated THMs (THMs-Cl).The experimental data including the main parameters such as bromide,DOC,ammonia,pH and reaction time were used for developing the predictive model for THMs-Br.展开更多
Chlorination is an efficient and low-cost technique in disinfecting water for public water supply. However, during the process, the formation of undesirable by-products called halogen compounds, such as trihalome-than...Chlorination is an efficient and low-cost technique in disinfecting water for public water supply. However, during the process, the formation of undesirable by-products called halogen compounds, such as trihalome-thanes (THMs), occurs. Some of these compounds are proven to be carcinogenic to laboratory animals. The goal of this study was to investigate the occurrence of THMs in household reservoirs and the influence of cleaning time of these reservoirs on the formation of THMs. A total of 103 households were investigated in the city of Maringá, State of Paraná, Brazil. The residences were classified according to the cleaning time of the reservoir into: up to one year, one to two years and more than two years. Samples were taken from the reservoirs and total trihalomethanes (THMt) were analyzed by gas chromatography (GC-MS), total organic carbon (TOC) by means of a Hach kit for low concentrations and free residual chlorine (CLres) by means of a kit for in loco determination. According to the results, the highest concentrations of THMt were observed in the reservoirs with cleaning time of more than 2 years. However, no amount has exceeded the maximum limit allowed by law. In general, the longer the time for cleaning the reservoir, the greater the degradation of water quality in THMt.展开更多
The chlorination process is one of the water treatment method used for the disinfection of water. The disinfection by products are trihalomethanes such as chloroform, dichloromethane, dibromochloromethane and bromofor...The chlorination process is one of the water treatment method used for the disinfection of water. The disinfection by products are trihalomethanes such as chloroform, dichloromethane, dibromochloromethane and bromoform. A headspace solid-phase microextraction method has been developed for determination oftrihalomethanes in water samples. The experimental parameters such as the stirring rate, extraction time, extraction temperature and desorption time were investigated. The linearity, detection limits and percentage recovery were evaluated. The optimum conditions were stirring rate 800 rpm/min, extraction time 6 min, extraction temperature 20 ~C, desorption time 2.5 min and desorption temperature 220 ~C. The detection limits were 0.01 ~g/L and the recoveries were in the range of 86-110 %, The proposed method was successfully applied to determination of THM4 in tap water samples. The THM4 contents were varied depending on the sample sites and the season. The total THM4 contents in cool, summer and rainy season were in the range of 27.58-41.89, 32.06-60.73 and 46.26-69.87 p.g/L, respectively. Confirmation of the detected compounds in water samples were performed by gas chromatograph-mass spectrometer. The mass spectra of the target compounds in water samples is in good agreement with trihalomethanes standard spectra.展开更多
We have analyzed the contamination of the three major watersheds in Middle Tennessee (Middle Cumberland River Watershed, Stones River Watershed, and Harpeth River Watershed) by trihalomethanes, such as chloroform, bro...We have analyzed the contamination of the three major watersheds in Middle Tennessee (Middle Cumberland River Watershed, Stones River Watershed, and Harpeth River Watershed) by trihalomethanes, such as chloroform, bromodichloromethane, dibromochloromethane, and bromoform. These chemicals play an important role in the develop-ment of cancer and adverse reproductive outcomes, and were found to be present above the threshold established by the Environmental Protection Agency. Certain portions of each watershed were found to be contaminated by the trihalomethanes, and deemed un-healthy. The household incomes in the major areas in the three watershed regions were also examined to determine a possible relationship with the level of water contamination. We concluded that income did not necessarily relate to water quality. Specific areas within each watershed that had lower average household incomes were found to have a higher concentration of the trihalomethanes in their drinking water, while other high-income areas were also affected by unhealthy water. However, these effects were random, and the level of contamination remained below the guidelines regulated by the State of Tennessee.展开更多
To investigate the characteristics of disinfection by-products （DBPs） in an actual water distribution system using the raw water with high bromide ion concentration, the composition and concentration of trihalometha...To investigate the characteristics of disinfection by-products （DBPs） in an actual water distribution system using the raw water with high bromide ion concentration, the composition and concentration of trihalomethanes （THMs） formed by chlorination of the water in the presence of bromide ion were measured in a city water distribution system during one year. The results show that brominated THMs contributed a great part （83%-89% ） to the index for additive toxicity （ATI） and resulted in the ATI of most of the samples exceeding WHO guideline standard for total THMs （ TTHMs）, especially during the summer （ rainy season）. This indicates that the chlorination of water in the presence of bromide ion leaded to high ratios of brominated THMs to TrHMs. However, a visible increase in the concentration of THMs with increasing residence time in the distribution system was not observed. Additionally, based on alternatives analysis, packed tower aeration method is proposed to reduce THMs level of the finished water leaving the treatment plant.展开更多
Trihalomethanes, such as chloroform, bromoform, dibromo(chloro)methane, and bromo(dichloro)methane, are present in the major watersheds across the United States. These chemicals play an important role in the developme...Trihalomethanes, such as chloroform, bromoform, dibromo(chloro)methane, and bromo(dichloro)methane, are present in the major watersheds across the United States. These chemicals play an important role in the development of cancer, have adverse reproductive outcomes, and were found to be present above the threshold established by the Environmental Protection Agency. To understand the impact of socioeconomic background on the quality of water and possible disparities, we have analyzed the levels of total trihalomethanes in the metropolitan areas in the major watersheds across the United States, in 2018, as they correlated to average household incomes. Our study found that Arkansas, Nevada, and Rhode Island demonstrated higher than federally mandated levels of total trihalomethanes in their watersheds. The median annual household and per capita incomes of the three states (Arkansas, Nevada, and Rhode Island) were lower than the national average. In addition, Delaware, New Hampshire, and Wisconsin, which had higher median income levels, demonstrated the lowest total trihalomethane levels across the United States.展开更多
文摘We investigated the concentration of trihalomethanes （THMs） in tap water and swimming pool water in the area of the Nakhon Path- om Municipality during the period April 2005-March 2006. The concentrations of total THMs, chloroform, bromodichloromethane, dibromochloromethane and bromoform in tap water were 12.70-41.74, 6.72-29.19, 1.12-11.75, 0.63-3.55 and 0.08-3.40 μg/L, respectively, whereas those in swimming pool water were 26.15-65.09, 9.50-36.97, 8.90-18.01, 5.19-22.78 and ND-6.56 μg/L, respectively. It implied that the concentration of THMs in swimming pool water was higher than those in tap water, particularly, brominated-THMs. Both tap water and swimming pool water contained concentrations of total THMs below the standards of the World Health Organization （WHO）, European Union （EU） and the United States Environmental Protection Agency （USEPA） phase Ⅰ, but 1 out of 60 tap water samples and 60 out of 72 swimming pool water samples contained those over the Standard of the USEPA phase Ⅱ. From the two cases of cancer risk assessment including Case Ⅰ Non-Swimmer and Case Ⅱ Swimmer, assessment of cancer risk of nonswimmers from exposure to THMs at the highest and the average concentrations was 4.43×10^-5 and 2.19×10^-5, respectively, which can be classified as acceptable risk according to the Standard of USEPA. Assessment of cancer risk of swimmers from exposure to THMs at the highest and the average concentrations was 1.47×10^-3 and 7.99×10^-4, respectively, which can be classified as unacceptable risk and needs to be improved. Risk of THMs exposure from swimming was 93.9%-94.2% of the total risk. Cancer risk of THMs concluded from various routes in descending order was： skin exposure while swimming, gastro-intestinal exposure from tap water intake, and skin exposure to tap water and gastro-intestinal exposure while swimming. Cancer risk from skin exposure while swimming was 94.18% of the total cancer risk.
基金supported by the National Natural Science Foundation of China (No. 50938007)the Funds for Major Science and Technology Program for Water Pollution Control and Treatment (No. 2012ZX07403-00202)the Special Co-construction Project of the Beijing Municipal Commission of Education
文摘Addition of H2O2 has been employed to repress bromate formation during ozonation of bromide-containing source water. However, the addition of H2O2 will change the oxidation pathways of organic compounds due to the generation of abundant hydroxyl radicals, which could affect the removal efficacy of trihalomethane precursors via the combination of ozone and biological activated carbon （O3-BAC）. In this study, we evaluated the effects of H2O2 addition on bromate formation and trihalomethane formation potential （THMFP） reduction during treatment of bromide-containing （97.6-129.1 μg/L） source water by the O3-BAC process. At an ozone dose of 4.2 mg/L, an H2O2/O3 （g/g） ratio of over 1.0 was required to maintain the bromate concentration below 10.0 μg/L, while a much lower H2O2/O3 ratio was sufficient for a lower ozone dose. An H2O2/O3 （g/g） ratio below 0.3 should be avoided since the bromate concentration will increase with increasing H2O2 dose below this ratio. However, the addition of H2O2 at an ozone dose of 3.2 mg/L and an H2O2/O3 ratio of 1.0 resulted in a 43% decrease in THMFP removal when compared with the O3-BAC process. The optimum H2O2/O3 （g/g） ratio for balancing bromate and trihalomethane control was about 0.7-1.0. Fractionation of organic materials showed that the addition of H2O2 decreased the removal efficacy of the hydrophilic matter fraction of DOC by ozonation and increased the reactivity of the hydrophobic fractions during formation of trihalomethane, which may be the two main reasons responsible for the decrease in THMFP reduction efficacy. Overall, this study clearly demonstrated that it is necessary to balance bromate reduction and THMFP control when adopting an H2O2 addition strategy.
文摘Organic matter is known to be the precursor of numerous chlorination by-products. Organic matter in the secondary effluent from the Wenchang Wastewater Treatment Plant （Harbin, China） was physically separated into the following fractions： particulate organic carbon （1.2-0.45 μm）, colloidal organic carbon （0.45-0.1 μm）, fine colloidal organic carbon （0.1-0.025 μm）, and dissolved organic carbon （DOC） （〈 0.025 μm）. Moreover, 〈 0.45 μm fraction was chemically separated into hydrophobic acid （HPO-A）, hydrophobic neutral （HPO-N）, transphilic acid （TPI-A）, transphilic neutral （TPI-N）, and hydrophllic fraction （HPI）. The chlorine reactivity of these organic fractions obtained from both size and XAD fractionations were evaluated. The structural and chemical compositions of the HPO-A, HPO-N, TPI-A, and TPI-N isolates were characterized using elemental analysis （C, H, O, and N）, Fourier transform infrared spectroscopy （FT-IR）, and proton nuclear magnetic resonance spectroscopy （1H-NMR）. Results showed that DOC was dominant in terms of total concentration and trihalomethane formation potential （THMFP）, and there was no statistical difference in both specific THMFP （STHMFP） and specific ultraviolet light absorbance among the 0.45, 0.1, and 0.025 ixm filtrates. HPO-A had the highest STHMFP compared to other chemical fractions. HPO-A, HPO-N, TPI-A, and TPI-N contained 3.02%-3.52% of nitrogen. The molar ratio of H/C increased in the order of HPO-A 〈 HPO-N 〈 TPI-A 〈 TPI-N. The O/C ratio was relatively high for TPI-N as compared to those for the other fractions. ^1H-NMR analysis of the four fractions indicated that the relative content of aromatic protons in HPO-A was significantly higher than those in the others. The ratio of aliphatic to aromatic protons increased in the order of HPO-A 〈 HPO-N 〈 TPI-A 〈 TPI-N. FT-IR analysis of the four fractions showed that HPO-A had greater aromatic C=C content whereas HPO-N, TPI-A, and TPI-N had greater aliphatic C-H content. TPI-N contained more oxygen-containing functional groups than the other fractions.
基金financially supported by National Mega-Project of Science and Technology of China (No.2008ZX07421-002)the National Eleventh Five-Year Pillar Program of Science and Technology of China (No.2006BAJ04A07)
文摘For the system of water samples collected from Yangtze River,the effects of seasonal variation and Fe（III） concentrations on the formation and distribution of trihalomethanes （THMs） during chlorination have been investigated.The corresponding lifetime cancer risk of the formed THMs to human beings was estimated using the parameters and procedure issued by the US EPA.The results indicated that the average concentration of THMs （100.81 μg/L） in spring was significantly higher than that in other seasons,which was related to the higher bromide ion concentration resulted from the intrusion of tidal saltwater.The total cancer risk in spring reached 8.23 × 10 ？5 and 8.86 × 10 ？5 for males and females,respectively,which were about two times of those in summer under the experimental conditions.Furthermore,it was found that the presence of Fe（III） resulted in the increased level of THMs and greater cancer risk from exposure to humans.Under weak basic conditions,about 10% of the increment of THMs from the water samples in spring was found in the presence of 0.5 mg/L Fe（III） compared with the situation without Fe（III）.More attention should be given to the effect of the coexistence of Fe（III） and bromide ions on the risk assessment of human intake of THMs from drinking water should be paid more attention,especially in the coastland and estuaries.
基金Science and Engineering Research Board (SERB), Department of Science and Technology (DST), Government of India for the financial support received for research project (SR/S3/CEE/0004/2013)Department of Environmental Science and Engineering, Indian Institute of Technology (ISM) Dhanbad
文摘Reactivity of chlorine towards hydrophobic groups present in natural organic matter（NOM）provokes the formation of carcinogenic disinfection byproducts such as trihalomethanes in chlorinated water. The present study aimed to investigate the variations in coagulant activity of alum using two different bioflocculants（coagulant aid） namely, Moringa oleifera and Cyamopsis tetragonoloba for the removal of hydrophobic fractions of NOM and subsequent chlorine consumption by treated water. Effect of dual coagulants on trihalomethane surrogate parameters such as total organic carbon, dissolved organic carbon, UV absorbing materials and prominent hydrophobic species such as phenolic groups along with aromatic chromophores, polyhydroxy aromatic moiety have also been studied. The concept of differential spectroscopy and absorbance slope index has been employed to understand the combined effects of alum-bioflocculants on the reactivity of NOM with chlorine. Our result shows that the combination of alum and C. tetragonoloba is more efficient for reducing trihalomethane surrogates from chlorinated water as compared to M. oleifera. C. tetragonoloba elicited synchronized effects of sweep coagulation and particle bridging-adsorption which eventually facilitated efficient removal of hydrophobic fractions of NOM. The variation in the mechanistic approach of bioflocculants was due to the presence of cationic charge on M. oleifera and adhesive property of C. tetragonoloba.
基金Project supported by the National Natural Science Foundation of China (No. 50878164)the Key Special Program on the S & T for the Pollution Control and Treatment of Water Bodies (No. 2008ZX07-422-005)+1 种基金the Research Fund for the Doctoral Program of Higher Education of China (No. 200802471037)the Foundation of Key Laboratory of Yangtze River Water Environment, Ministry of Edu-cation, Tongji University (No. YRWEY1001), China
文摘The effects of the concentration of dissolved total organic carbon (TOC), the TOC/Br- ratio, bromide ion levels, the chlorine to ammonia-N ratio (Cl:N), the monochloramine dose and the chlorine dose on the formation of trihalomethanes (THMs) (including chloroform, bromodichloromethane, chlorodibromomethane, and bromoform) from chlorination were investigated using aqueous humic acid (HA) solutions. The profile of the chloramine decay was also studied under various bromide ion concentrations. Monochloramine decayed in the presence of organic material and bromide ions. The percentage of chloroform and brominated THMs varied according to the TOC/Br- ratio. Total THMs (TTHMs) formation increased from 112 to 190 μg/L with the increase concentrations of bromide ions from 0.67 to 6.72 mg/L, but the chlorine-substituted THMs were replaced by bromine-substituted THMs. A strong linear correlation was obtained between the monochloramine dose and the formation of THMs for Cl:N ratios of 3:1 and 5:1. These ratios had a distinct effect on the formation of chloroform but had little impact on the formation of bromodichloromethane or chlorodibromomethane. The presence of bromide ions increased the rate of monochloramine decay.
文摘In a sanitation process of drinking water, carbon from the organic matter reacts with chlorine, forming by-products, among which are trihalomethanes (THM). These substances are carriers of mutagenic and can-cerogenic potential and hence should be removed in drinking water treatment. Since the natural organic mat-ters are precursors of THM formation, their removal from the water decreases the concentration of THMs. The THM forming potential is the most reliable indicator in evaluation of organic matter removal during drinking water treatment processes. The results have shown that the reaction producing THMs follows sec-ond order kinetics. The second order rate constant ranged from 0.024 M-1s-1 to 0.065 M-1s-1 at 22 °C and pH = 8.2 for 96 hours. The removal of 78.4% of natural organic matter, by adsorption on anionic exchange res-ins, resulted in the THM forming potential reduction by 63.1%. Various fractions of natural organic matter differ in their reactivity with chlorine, which is important when it comes to selection of the adsorption me-dium in the drinking water treatment processes.
文摘The use of seawater for industrial cooling is a vital technology that poses some of the most profound environmental impact on the water quality in the Arabian Gulf. Biocide (chlorine) is added to the seawater to control biofouling of the cooling system. This added chlorine reacts with bromide and other chemicals naturally exist in the water to form a wide range of oxidants. Regrettably, reactions between the residual oxidants and natural organic matter in the water lead to formation of toxic halogenated organic compounds that have detrimental effects on the environment when they are discharged into the Gulf. This paper describes the formation of trihalomethanes (THMs) in seawater cooling systems. Results of kinetic experiments have shown that concentrations of THMs increased rapidly with time during the first half hour. Chlorination of seawater has shown significant increase in total THMs (TTHMs) and in bromoform concentrations. Rapid decrease of UV absorbance at 254 nm was also observed during seawater chlorination which is indicative of natural organic matter degradation into small organic molecules including THMs and other by-products. The increase in chlorine dose was accompanied with an increase in TTHMs and bromoform concentrations. Linear relationships between total chlorine concentration and both final TTHMs and bromoform concentrations were established. First order exponential decay and exponential associate functions were developed to correlate chlorine dose with formed THMs.
文摘Bottled water consumption is increasing worldwide, despite its huge economic and environmental cost. We aim to describe personal and tap water quality determinants of bottled water use in the city of Barcelona. This cross-sectional study used data from the Health Survey of Barcelona in 2006（N = 5417 adults）. The use of bottled water to drink and to cook was evaluated in relation to age, gender, educational level, district and levels of trihalomethanes（THMs）, free chlorine, conductivity, chloride, sodium, p H, nitrate and aluminium in municipal tap water using Robust Poisson Regression. The prevalence of bottled water use to drink and cook was 53.9% and 6.7%, respectively. Chemical parameters in water had a large variability（interquartile range of THMs concentrations： 83.2–200.8 μg/L）and were correlated between them, except aluminium. Drinking bottled water increased with educational level, while cooking with bottled water was higher among men than among women and decreased with age. After adjusting by these personal determinants, a dose–response relationship was found between concentrations of all chemicals except aluminium in tap water and bottled water use. The highest association was found for THMs,with a Prevalence Ratio of 2.00（95%CI = 1.86, 2.15） for drinking bottled water and 2.80（95%CI = 1.72, 4.58） for cooking with bottled water, among those with 〉 150 μg/L vs. 〈 100 μg/L THMs in tap water. Conclusion： More than half of Barcelona residents regularly drank bottled water, and the main determinant was the chemical composition of tap water,particularly THM level.
基金supported by the National Natural Science Foundation of China(Nos.51878648,52070184)the National Key Research and Development Program of China(No.2019YFD1100100)。
文摘To ensure the safety of drinking water,ozone (O3) has been extensively applied in drinking water treatment plants to further remove natural organic matter (NOM).However,the surface water and groundwater near the coastal areas often contain high concentrations of bromide ion (Br-).Considering the risk of bromate (Br O3-) formation in ozonation of the sand-filtered water,the inhibitory efficiencies of hydrogen peroxide (H2O2) and ammonia(NH3) on Br O3-formation during ozonation process were compared.The addition of H2O2effectively inhibited Br O3-formation at an initial Br-concentration amended to 350μg/L.The inhibition efficiencies reached 59.6 and 100%when the mass ratio of H2O2/O3was 0.25and>0.5,respectively.The UV254and total organic carbon (TOC) also decreased after adding H2O2,while the formation potential of trihalomethanes (THMs FP) increased especially in subsequent chlorination process at a low dose of H2O2.To control the formation of both Br O3-and THMs,a relatively large dose of O3and a high ratio of H2O2/O3were generally needed.NH3addition inhibited Br O3-formation when the background ammonia nitrogen(NH3–N) concentration was low.There was no significant correlation between Br O3-inhibition efficiency and NH3dose,and a small amount of NH3–N (0.2 mg/L) could obviously inhibit Br O3-formation.The oxidation of NOM seemed unaffected by NH3addition,and the structure of NOM reflected by synchronous fluorescence (SF) scanning remained almost unchanged before and after adding NH3.Considering the formation of Br O3-and THMs,the optimal dose of NH3was suggested to be 0.5 mg/L.
基金supported by the National Natural Science Foundation of China(Nos.51778565,51578487)the Zhejiang Provincial Natural Science Foundation of China(No.LY15E080005)
文摘Sulfonamides are used in human therapy, animal husbandry and agriculture but are not easily biodegradable, and are often detected in surface water. Sulfamethazine （SMZ） and sulfadiazine （SDZ） are two widely used sulfonamide antibiotics that are used heavily in agriculture. In this study, they were degraded in an aqueous system by chlorination after pre-oxidation with ferrate（VI） （FeVIO2-, Fe（VI））, an environmentally friendly oxidation technique that has been shown to be effective in degrading various organics. The kinetics of the degradation were determined as a function of Fe（VI） （0-1.5 mg/L）, free chlorine （0-1.8 mg/L） and temperature （15- 35℃）. According to the experimental results, SMZ chlorination followed second-order kinetics with increasing Fe（VI） dosage, and the effect of the initial free chlorine concentration on the reaction kinetics with pre-oxidation by Fe（VI） fitted a pseudo-first order model. The rate constants of SDZ and SMZ chlorination at different temperatures were related to the Arrhenius equation. Fe（VI） could reduce the levels of THMs formed and the toxicity of the sulfonamide degradation systems with Fe（VI） doses of 0.5-1.5 mg/L, which provides a reference for ensuring water quality in drinking water systems.
文摘The mechanism of activated carbon fiber (ACF) adsorption trihalomethanes (THMs) was studied. It was found that ACF adsorption THMs was exothermic, the physico-adsorption principally, but not a complete monolayer adsorption. The adsorptive capacities of ACF increased as the four species of THMs became more hydrophobic, and as the chlorine atoms in CHCls were substituted by more bromine atoms. The result of fixed-bed reactor adsorption was fitted to that of isotherm experiments.
基金Sponsored by the National High Technology Research and Development Program of China(Grant No.2002AA601140)
文摘An effective technology in controlling trihalomethanes （THMs） formation in the case of large amounts of bromide presenting was proposed, and the water of River Huang seriously polluted by bromide in winter in Tianjin City was studied. The THMs formation characteristics during prechloramination using preformed chloramines and converted chloramines were studied through jar tests. Results show that, in prechloramination process, the formation of THMs by preformed chloramines is very few, while that by converted ehloramines is a little higher. And the formation of THMs, especially Br^- substituted THMs, increases with the increase of time and Cl2：N ratio as well as the decrease of pH. The result obtained in a pilot plant shows that compared with prechlorination, the prechloramination process can efficiently control the formation of THMs, especially the Br^- substituted species. With equal chlorine dosage, the prechloramination can maintain a larger chlorine residue which offece, a larger CT value than prechlorination.
基金Sponsored by the National Natural Science Foundation of China(Grant No.50908074)the Fundamental Research Funds for the Central Universities(Grant No.2009B17314)
文摘Glycine(Gly),cysteine(Cys),aspartic acid(Asp),leucine(Leu),lysine(Lys),and methyl amine(MA) were chosen as typical nitrogenous compounds,and the effects of them on trihalomethanes (THMs) formation and chlorine demand were performed on filtrated water. Results show that the nitrogenous compounds enhance THMs formation,and the increased levels are controlled by characteristics and the concentration of nitrogenous compounds. The increase in THMs formation follows the order of Asp(126 μg/L)>Cys(119 μg/L)>MA(106 μg/L)>Lys(97 μg/L)≈Gly(96 μg/L)>Leu(80 μg/L)(while nitrogenous compounds=1.0 mg/L,and background THMs=60 μg/L). The increase in chlorine demand is approximately proportionate to the content of nitrogenous compounds,which illustrates that the increase is mainly caused by the reaction of nitrogenous compounds with chlorine. And the increase in chlorine demand follows the order of Cys(27.8 mg/L)>Asp(22.6 mg/L)=Gly(22.6 mg/L)>Lys(21.6 mg/L)>MA(14.1 mg/L)>Leu(11.8 mg/L) (while nitrogenous compounds=1.0 mg/L,and background chorine demand=1.8 mg/L). The mechanisms of nitrogenous compounds enhancing THMs formation are summ the increase of chlorine demand raising THMs formation in reaction of NOM with chlorine,and the THMs formation in chlorination of nitrogenous compounds themselves.
基金Project supported by the National Hi-Tech Research and Development Program (863) of China (No.2006AA06Z311)the National Natural Science Foundation of China (No.50808052)
文摘The formation of brominated trihalomethanes (THMs-Br) which is proved more carcinogenic than their chlorinated analogues reported was very different at various water qualities.This study was performed to assess the effects of water quality parameters (bromide concentration,pH value and ammonia concentration),chlorination conditions (chlorine dose,reaction time) and ratios of Br-/DOC and Br-/Cl2 consumption on the formation and distribution of THMs-Br in chlorination.The results showed good correlation between the bromine incorporation factor (BIF) n(Br) and Br-/Cl2 consumption ratio.The formation of total THM (TTHM) was found to decrease with increasing ammonia concentration but to increase with bromide concentration and pH value.The n(Br) trends were significantly affected by the presence of bromide concentration.The effects on the molar yields of THMs were more strongly influenced by bromide concentration and dissolved organic carbon (DOC) concentration than pH value and natural organic matter (NOM) source.High Br-/DOC and Br-/Cl2 favor the formation of THMs-Br over chlorinated THMs (THMs-Cl).The experimental data including the main parameters such as bromide,DOC,ammonia,pH and reaction time were used for developing the predictive model for THMs-Br.
文摘Chlorination is an efficient and low-cost technique in disinfecting water for public water supply. However, during the process, the formation of undesirable by-products called halogen compounds, such as trihalome-thanes (THMs), occurs. Some of these compounds are proven to be carcinogenic to laboratory animals. The goal of this study was to investigate the occurrence of THMs in household reservoirs and the influence of cleaning time of these reservoirs on the formation of THMs. A total of 103 households were investigated in the city of Maringá, State of Paraná, Brazil. The residences were classified according to the cleaning time of the reservoir into: up to one year, one to two years and more than two years. Samples were taken from the reservoirs and total trihalomethanes (THMt) were analyzed by gas chromatography (GC-MS), total organic carbon (TOC) by means of a Hach kit for low concentrations and free residual chlorine (CLres) by means of a kit for in loco determination. According to the results, the highest concentrations of THMt were observed in the reservoirs with cleaning time of more than 2 years. However, no amount has exceeded the maximum limit allowed by law. In general, the longer the time for cleaning the reservoir, the greater the degradation of water quality in THMt.
文摘The chlorination process is one of the water treatment method used for the disinfection of water. The disinfection by products are trihalomethanes such as chloroform, dichloromethane, dibromochloromethane and bromoform. A headspace solid-phase microextraction method has been developed for determination oftrihalomethanes in water samples. The experimental parameters such as the stirring rate, extraction time, extraction temperature and desorption time were investigated. The linearity, detection limits and percentage recovery were evaluated. The optimum conditions were stirring rate 800 rpm/min, extraction time 6 min, extraction temperature 20 ~C, desorption time 2.5 min and desorption temperature 220 ~C. The detection limits were 0.01 ~g/L and the recoveries were in the range of 86-110 %, The proposed method was successfully applied to determination of THM4 in tap water samples. The THM4 contents were varied depending on the sample sites and the season. The total THM4 contents in cool, summer and rainy season were in the range of 27.58-41.89, 32.06-60.73 and 46.26-69.87 p.g/L, respectively. Confirmation of the detected compounds in water samples were performed by gas chromatograph-mass spectrometer. The mass spectra of the target compounds in water samples is in good agreement with trihalomethanes standard spectra.
文摘We have analyzed the contamination of the three major watersheds in Middle Tennessee (Middle Cumberland River Watershed, Stones River Watershed, and Harpeth River Watershed) by trihalomethanes, such as chloroform, bromodichloromethane, dibromochloromethane, and bromoform. These chemicals play an important role in the develop-ment of cancer and adverse reproductive outcomes, and were found to be present above the threshold established by the Environmental Protection Agency. Certain portions of each watershed were found to be contaminated by the trihalomethanes, and deemed un-healthy. The household incomes in the major areas in the three watershed regions were also examined to determine a possible relationship with the level of water contamination. We concluded that income did not necessarily relate to water quality. Specific areas within each watershed that had lower average household incomes were found to have a higher concentration of the trihalomethanes in their drinking water, while other high-income areas were also affected by unhealthy water. However, these effects were random, and the level of contamination remained below the guidelines regulated by the State of Tennessee.
基金National High-Tech Research and Development Program of China ( 863 Program ) ( No.2007AA06Z303)
文摘To investigate the characteristics of disinfection by-products （DBPs） in an actual water distribution system using the raw water with high bromide ion concentration, the composition and concentration of trihalomethanes （THMs） formed by chlorination of the water in the presence of bromide ion were measured in a city water distribution system during one year. The results show that brominated THMs contributed a great part （83%-89% ） to the index for additive toxicity （ATI） and resulted in the ATI of most of the samples exceeding WHO guideline standard for total THMs （ TTHMs）, especially during the summer （ rainy season）. This indicates that the chlorination of water in the presence of bromide ion leaded to high ratios of brominated THMs to TrHMs. However, a visible increase in the concentration of THMs with increasing residence time in the distribution system was not observed. Additionally, based on alternatives analysis, packed tower aeration method is proposed to reduce THMs level of the finished water leaving the treatment plant.
文摘Trihalomethanes, such as chloroform, bromoform, dibromo(chloro)methane, and bromo(dichloro)methane, are present in the major watersheds across the United States. These chemicals play an important role in the development of cancer, have adverse reproductive outcomes, and were found to be present above the threshold established by the Environmental Protection Agency. To understand the impact of socioeconomic background on the quality of water and possible disparities, we have analyzed the levels of total trihalomethanes in the metropolitan areas in the major watersheds across the United States, in 2018, as they correlated to average household incomes. Our study found that Arkansas, Nevada, and Rhode Island demonstrated higher than federally mandated levels of total trihalomethanes in their watersheds. The median annual household and per capita incomes of the three states (Arkansas, Nevada, and Rhode Island) were lower than the national average. In addition, Delaware, New Hampshire, and Wisconsin, which had higher median income levels, demonstrated the lowest total trihalomethane levels across the United States.
