Predicting the Formation of Chlorinated and Brominated By-Products

Although disinfection was one of the major public health advances in the last century and continues to be so in the twenty-first century, the disinfectants themselves may react with naturally occurring materials in treated water to form unintended by-products, which may themselves pose risks. This is of particular concern with regard to the use of chlorine. Generation of disinfection by-products (DBPs) has been shown to be a function of various factors including total organic carbon concentration, type of organic precursor, chlorination level, pH, temperature, reaction time, and UV-254 absorbance. Another factor affecting DBP formation is the presence and concentration of the bromide ion in the raw or finished water. Bromine substitutes for chlorine to produce bromine-containing homologues of the more familiar chlorine species. The current list of by-products targeted for regulation contains brominated and mixed bromine-chlorine species of total trihalomethanes and haloacetic acids. These are known to form in bromide-containing waters when chlorinated. To control chlorination DBPs therefore requires an understanding of the factors that influence their formation. This paper presents a model that can be used to predict the formation of chlorinated, brominated, and mixed species compounds based on initial chlorine concentration, chlorine consumption, bromide ion concentration, and pH. The model clearly shows that higher levels of bromide in the water favor the formation of brominated compounds. Brominated compounds also form faster than chlorinated compounds.     

Hydrophobicity and Molecular Size Distribution of Unknown TOX in Drinking Water

The analysis of total organic halogen (TOX) in drinking water indicates that a substantial amount of the halogenated compounds cannot be accounted for by known specific disinfection by-products (DBPs). The primary aim of this research was to characterize the hydrophobicity and molecular size distribution of the unknown halogenated DBPs using XAD resins and ultrafiltration membranes. The impact of membrane rejection on the size analysis of unknown TOX was also investigated using chlorinated fulvic acid. Six finished waters from different locations and treatment processes were collected and fractionated into various hydrophobicity and molecular size groups. The results showed that most unknown TOX was in the size range between 0.5?kDa and 10?kDa, but it could have a wide spectrum of hydrophobicities. Simple ultrafiltration was not always reliable as a characterization tool, as it was shown to reject a significant fraction of DBPs with molecular weight (MW) lower than the membrane cutoffs. Flushing with deionized water was effective in removing these low MW compounds from the ultrafiltration cell. A significant reduction in the apparent size of unknown TOX resulted when low MW DBPs were flushed out of the cell (comparing with classic parallel ultrafiltration). Coagulation of fulvic acid also significantly reduced the apparent size of unknown TOX formed by chlorine.     

Methotrexate suppresses nitric oxide production ex vivo in macrophages from rats with adjuvant-induced arthritis

This review discusses the relation between by-products of drinking water chlorination and cancer in the light of present toxicological and epidemiologic evidence. During the chlorination of drinking water, a complex mixture of by-products forms from chlorine and the organic and inorganic compounds present in raw water. The quality and quantity of such compounds depend on the specific nature of the organic material in raw waters, the inorganic material in raw water, pH, temperature, other water treatment practices, and the chlorine timing and dose added. Chlorination by-products are important mainly when surface water is used for drinking water as more organic compounds are present in surface waters than in ground waters. The gastrointestinal and urinary tract are the cancer sites that are most often associated with the use of chlorinated surface water or with the quantity of chlorination by-products in the water-supply network. Yet the microbial quality of drinking water should not be compromised by excessive caution over the potential long-term effects of disinfection by-products because the risk of illness and death resulting from exposure to pathogens in untreated drinking water may be several orders of magnitude greater than the cancer risks from chlorination by-products.     

Disinfection By-Product Formation during Long-Term Water Storage in Alaska

In many areas of Northern and Western Alaska, small streams and shallow lakes serve as community raw water supplies. These water supplies freeze completely during winter. In order to supply drinking water during the 6–9 month winter, communities store water that was treated during summer. A chlorine residual is maintained in the stored water. Raw water sources derived from surface water may be heavily laden with dissolved organic matter. At utilities where organic matter escapes treatment, the potential for accumulation of disinfection by-products (DBPs) during storage is a significant health concern. The following study was performed to evaluate this potential threat. Water was collected from five operating utilities, four that normally store water for 6–9 months and one that produces drinking water year-round. Raw, filtered (i.e., unchlorinated) and “finished” (i.e., filtered and chlorinated) water samples were collected during the summer pumping season and stored in the laboratory for 8 months. In order to mimic practice in the field, the chlorine residual was maintained in the finished water for the full storage period. While the concentration of DBPs in the finished water varied over the study period, there was not a statistically significant trend from the third to the eighth month of storage. The observed DBP values were strongly a function of the type of treatment system used. Those systems passing more organic matter had higher DBP values throughout the storage period. The ultraviolet absorbance at 254 nanometers ?start(UV254)end? decreased continuously in the finished water coincident with chlorine consumption. ?startUV254end?, often used as a surrogate for DBPs, remained constant during the entire storage periodin raw and filtered water samples. Filtered water that was stored prior to chlorination accumulated fewer DBPs than finished water that was continuously chlorinated during the storage period. This result suggests that storing filtered water instead of finished water for long periods would limit DBP exposure to consumers. This conclusion was based on a comparison of DBP formation potentials (i.e., raw and filtered water) to DBPs (i.e., finished water). It is important to note that DBP formation potentials are based on a ?start24?hend?chlorine contact time. If long term storage were provided for filtered water, a smaller volume of secondary storage would still be needed to provide contact time for disinfection.     

Incorporating Reservoir Transfer into Treatment Optimization Decisions

The Massachusetts Water Resources Authority (MWRA) supplies unfiltered water from two large surface water reservoirs to the metropolitan Boston area, as well as to three smaller communities in central Massachusetts [the Chicopee Valley Aqueduct (CVA) communities]. Quabbin Reservoir is larger than Wachusett Reservoir, and has traditionally been used to supplement the Wachusett during the summer period. Quabbin water is also of better quality, with lower reactive natural organic matter (NOM). The MWRA began to add chlorine at Wachusett in 1997, and a new facility for adding chlorine at Quabbin for the CVA was also started up in 2000 to meet primary disinfection regulations to meet pathogen inactivation. The reaction of chlorine with NOM produces undesirable disinfection by-products (DBPs). The absorption of ultraviolet light at a wavelength of 254 nm was identified in chlorine decay studies to be the most important raw water quality parameter for predicting chlorine decay and DBP formation. This technical note summarizes the chlorine decay model for Wachusett and Quabbin water. The model is extended to ozonation of Wachusett water for the future Walnut Hill treatment plant. The models allowed the development of a trigger using UV-254 to time the Quabbin transfer to optimize treatment results. It is believed that the model for disinfectant decay and the use of UV-254 as a trigger for water treatment decisions are generalized and applicable to other water utilities.     

Temporal and Spatial Variations in Bulk Chlorine Decay within a Water Supply System

Modern water treatment must maintain an acceptable balance between the microbial safety of potable water supply, the costs of treatment, and the formation of potentially harmful disinfection by-products (DBPs). In order to achieve the optimum balance, it is essential to understand and predict both the formation of DBP and the decay of chlorine, in relation to source water, treatment processes, storage, and supply. Reported herein are new data which demonstrate the lack of durability, precision, and accuracy associated with earlier empirical chlorine decay rate equations. This work develops an improved methodology for the prediction of variation in chlorine decay rates in distribution systems enabling practical, cost-effective prediction of the effects of both seasonal variations and management interventions on chlorine levels at treatment works and in distribution systems.     

Effects of Bromide Ion and Natural Organic Matter Fractions on the Formation and Speciation of Chlorination By-Products

The impacts of bromide concentration and natural organic matter (NOM) characteristics on the formation and speciation of disinfection by-products (DBPs) in chlorinated NOM fractions were investigated. A total of 20 bulk water NOM fractions with a wide range of specific ultraviolet (UV) absorbance (SUVA254) values were obtained from a source water employing XAD-8 or XAD-4 resin adsorption in completely mixed batch reactors. SUVA was not a good predictor of DBP [trihalomethanes (THMs), haloacetic acids (HAAs), and adsorbable organic halogens (AOX)] formation and speciation. The destruction in the UV254 absorbance from chlorination did not correlate with DBP formation at any bromide level. NOM moieties which do not absorb UV light at 254?nm significantly contributed to DBP formation. Mass balance calculations on halogens using THMs, HAAs, and AOX data indicated that significant amounts of DBPs (>54% of AOX) other than THMs and HAAs were formed in NOM fractions with 60–110?μg/L bromide concentration. The relative occurrence of such other halogenated by-products decreased with increasing bromide concentrations up to 500?μg/L level. NOM in the studied water was more susceptible to the formation of brominated THM species as opposed to brominated HAAs. At constant dissolved organic carbon concentration, chlorine dose and pH, increasing bromide concentrations in NOM fractions increased the total concentrations of DBPs and resulted in a shift toward the formation of brominated species. Further, increasing bromide concentrations increased the spectrum of detected species (i.e., occurrence of all nine HAAs) and provided a competitive advantage to THM and HAA precursors in NOM over precursors of other DBPs.     

Exposure estimates to disinfection by-products of chlorinated drinking water

Exposure to disinfection by-products (DBPs) of drinking water is multiroute and occurs in households serviced by municipal water treatment facilities that disinfect the water as a necessary step to halt the spread of waterborne infectious diseases. Biomarkers of the two most abundant groups of DBPs of chlorination, exhaled breath levels of trihalomethanes (THMs) and urinary levels of two haloacetic acids, were compared to exposure estimates calculated from in-home tap water concentrations and responses to a questionnaire related to water usage. Background THM breath concentrations were uniformly low. Strong relationships were identified between the THM breath concentrations collected after a shower and both the THM water concentration and the THM exposure from a shower, after adjusting for the postshower delay time in collecting the breath sample. Urinary haloacetic acid excretion rates were not correlated to water concentrations. Urinary trichloroacetic acid excretion rates were correlated with ingestion exposure, and that correlation was stronger in a subset of individuals who consumed beverages primarily within their home where the concentration measurements were made. No correlation was observed between an average 48-hr exposure estimate and the urinary dichloroacetic acid excretion rate, presumably because of its short biological half-life. Valid biomarkers were identified for DBP exposures, but the time between the exposure and sample collection should be considered to account for different metabolic rates among the DBPs. Further, using water concentration as an exposure estimate can introduce misclassification of exposure for DBPs whose primary route is ingestion due to the great variability in the amount of water ingested across a population.     

Effect of monochloramine disinfection of municipal drinking water on risk of nosocomial Legionnaires' disease

BACKGROUND: Many Legionella infections are acquired through inhalation or aspiration of drinking water. Although about 25% of municipalities in the USA use monochloramine for disinfection of drinking water, the effect of monochloramine on the occurrence of Legionnaires' disease has never been studied. METHODS: We used a case-control study to compare disinfection methods for drinking water supplied to 32 hospitals that had had outbreaks of Legionnaires' disease with the disinfection method for water supplied to 48 control-hospitals, with control for selected hospital characteristics and water treatment factors. FINDINGS: Hospitals supplied with drinking water containing free chlorine as a residual disinfectant were more likely to have a reported outbreak of Legionnaires' disease than those that used water with monochloramine as a residual disinfectant (odds ratio 10.2 [95% CI 1.4-460]). This result suggests that 90% of outbreaks associated with drinking water might not have occurred if monochloramine had been used instead of free chlorine for residual disinfection (attributable proportion 0.90 [0.29-1.00]). INTERPRETATION: The protective effect of monochloramine against legionella should be confirmed by other studies. Chloramination of drinking water may be a cost-effective method for control of Legionnaires' disease at the municipal level or in individual hospitals, and widespread implementation could prevent thousands of cases.     

Impact of Booster Chlorination on Chlorine Decay and THM Production: Simulated Analysis

The effect of conventional and booster chlorination on chlorine residuals and trihalomethane (THM) formation in drinking water distribution systems was modeled using the EPANET hydraulic modeling software. The model results suggest that booster chlorination may allow utilities to meet disinfection goals better by carrying chlorine residuals to remote points in the distribution system while lowering the total mass of chlorine applied to the system. The model results suggest that booster chlorination may provide the greatest advantages to points in the distribution system located near storage tanks by providing a more consistent chlorine residual and possibly reducing THM formation. A new version of the EPANET model, the EPANET Multispecies model, was also used to compare chlorine decay due to reactions in the bulk fluid and reactions occurring at the pipe wall. The results suggest that chlorine decay due to wall reactions can be very significant at remote points in the distribution system. Additionally, if THMs are assumed to form primarily through reactions in the bulk fluid, use of the new EPANET Multispecies software allows for calculation of THM formation based solely on chlorine reactions in the bulk fluid rather than on overall chlorine decay.     

城市供水消毒中副产物风险与微生物安全性的控制原则

对城市饮用水消毒过程中如何控制消毒副产物对人体健康影响的风险，同时保证水质的微生物安全性提出了三点原则。     

Clinical research: any future?

Monochloramine has been suggested as an alternative disinfectant to chlorine to reduce levels of trihalomethanes in treated drinking water, but little is known of the toxicological properties and potential health implications of by-products specific to the chloramination process. Model aqueous fulvic acid solutions (200-400 mg C/liter), serving as surrogates for humic surface waters, were chloraminated over a range of molar Cl:C ratios from 1:40 to 1:2. The resulting by-products were extracted into diethyl ether at pH 2 and investigated with the Ames plate incorporation assay. Extractable mutagenicity increased with increasing chlorine and carbon dose up to about 30,000 revertants/liter at Cl:C ratios of 1:2. Mutagenicity was higher in Salmonella typhimurium strain TA100 than in strain TA98, and was decreased in the presence of S9, indicating that the mutagens formed were direct-acting and induced predominantly base-pair substitutions. Bovine serum albumin decreased slightly, and glutathione reduced greatly, the mutagenic activity detected in extracts. HPLC fractionation of the by-products indicated that most of the mutagenic activity was found in the earliest-eluting (most polar) fraction. The mutagenic by-products appeared to be qualitatively similar to 3-chloro-4-dichloromethyl-5-hydroxy-2-(5H)-furanone (MX) in their chromatographic behavior and responses to glutathione and bovine serum albumin, but were less readily detoxified by S9 than was MX.     

Preliminary screening for the potential of drinking water disinfection byproducts to alter male reproduction

There is increasing epidemiologic interest in the role drinking water disinfection byproducts (DBPs) may play in adverse reproductive outcomes such as inability to conceive, spontaneous abortion, and low birth weight. Although dozens of DBPs already have been identified, only a few studies have attempted to determine whether DBPs alter male reproductive parameters such as testicular and epididymal histology, testicular and epididymal sperm numbers, and epididymal sperm morphology and motility in laboratory animals. In these studies, alterations in epididymal sperm motility seemed to be predictive of more generalized toxicity of the male reproductive system. Because there is a need to prioritize DBPs for thorough reproductive and developmental toxicity testing, preliminary screening for the potential of DBPs to alter reproductive function seems warranted. Here, we elected to examine only cauda epididymal sperm motion parameters and testicular and epididymal histopathology. The effects of exposure to two commonly occurring DBPs, bromodichloromethane (BDCM) and chloral hydrate (CH), via drinking water were evaluated in F344 rats at an interim (52 week) necropsy during cancer bioassay studies. Exposure to 22 and 39 mg/kg BDCM and 55 and 188 mg/kg CH did not produce any systemic toxicity. Histopathologic evaluation revealed no gross lesions in the reproductive organs, and no tumors were detected in any tissues. In contrast, exposure to 39 mg/kg BDCM significantly decreased the mean straight-line, average path, and curvilinear velocities of sperm recovered from the cauda epididymidis. This BDCM exposure shifted the average path velocity distribution to a lower modal velocity range. Exposure to 188 mg/kg CH significantly decreased both the percentage of motile and progressively motile sperm. This CH exposure shifted the straight-line velocity distribution to a lower modal velocity range. These are the first reproductive toxicity data from exposure to BDCM and CH. The observed effects on sperm motion occurred in the absence of carcinogenesis. Because the effects of BDCM on sperm motility occurred at a lower exposure than that of other DBPs that compromise sperm motility, a thorough reproductive evaluation now is underway.     

Trihalomethane Species Forecast Using Optimization Methods: Genetic Algorithms and Simulated Annealing

Chlorination is an effective method for disinfection of drinking water. Yet chlorine is a strong oxidizing agent and easily reacts with both organic and inorganic materials. Trihalomethanes (THMs), formed as a by-product of chlorination, are carcinogenic to humans. Models can be derived from linear and nonlinear multiregression analyses to predict the THM species concentration of empirical reaction kinetic equations. The main objective of this study is to predict the concentrations of THM species by minimizing the nonlinear function, representing the errors between the measured and calculated THM concentrations, using the genetic algorithm (GA) and simulated annealing (SA). Additionally, two modifications of SA are employed. The solutions obtained from GA and SA are compared with the measured values and those obtained from a generalized reduced gradient method (GRG2). The results indicate that the proposed heuristic methods are capable of optimizing the nonlinear problem. The predicted concentrations may provide useful information for controlling the chlorination dosage necessary to assure the safety of water drinking.     

Case-control study of bladder cancer and water disinfection methods in Colorado

A population-based case-control study of bladder cancer and drinking water disinfection methods was conducted during 1990-1991 in Colorado. Surface water in Colorado has historically been disinfected with chlorine (chlorination) or with a combination of chlorine and ammonia (chloramination). A total of 327 histologically verified bladder cancer cases were frequency matched by age and sex to 261 other-cancer controls. Subjects were interviewed by telephone about residential and water source histories. This information was linked to data from water utility and Colorado Department of Health records to create a drinking water exposure profile. After adjustment for cigarette smoking, tap water and coffee consumption, and medical history factors by logistic regression, years of exposure to chlorinated surface water were significantly associated with risk for bladder cancer (p = 0.0007). The odds ratio for bladder cancer increased for longer durations of exposure to a level of 1.8 (95% confidence interval 1.1-2.9) for more than 30 years of exposure to chlorinated surface water compared with no exposure. The increased bladder cancer risk was similar for males and females and for nonsmokers and smokers. Levels of total trihalomethanes, nitrates, and residual chlorine were not associated with bladder cancer risk after controlling for years of exposure to chlorinated water.     

Evaluation of Drinking Water Treatment Technology: An Entropy-Based Fuzzy Application

Environmental risk management strategy often encounters conflicting criteria of a subjective and objective nature that are associated with a particular management system concerning multicriteria decision making. In this study, a combination of subjective and objective criteria for risk management has been applied for drinking water treatment technology. Fuzzy set theory has been incorporated in this study. Fuzzy triangular membership functions have been developed to capture uncertainties of the model parameter values. The analytic hierarchy process has been incorporated to construct subjective priority schemes for different hierarchy level attributes. In developing subjective priority schemes, flexible ranges of importance were considered; thus the uncertainties associated with crisp values were incorporated. Using the concept of entropy, subjective importance of the objective attributes have been transformed into integrated importance. The overall ranking was evaluated based on subjective and objective criteria. An example of human health risk management from drinking water disinfection by-products has been presented through several drinking water treatment technologies. Finally, the best treatment technology is outlined.     

Iron Oxide Enhanced Chlorine Decay and Disinfection By-Product Formation

This study investigates the interaction of natural organic matter with iron oxide (goethite) on chlorine decay, disinfection by-product (DBP) formation, and DBP compound speciation [total trihalomethanes (TTHM4) and haloacetic acids (HAA5)]. Batch experiments were conducted with goethite, multiple finished drinking waters, variable chlorine dose, and fixed pH 8. The overall objective was to assess natural organic matter (NOM) adsorption onto goethite and its effect on chlorine decay and DBP formation. Chlorine consumption always increased in the presence of goethite and is attributed to an increase in the reactivity and/or modification of adsorbed NOM. Adsorbed NOM also led to an overall increase in TTHM4, however, HAA5 formation was suppressed during the first 2?h. Chloroform was identified as the increasing species and dichloracetic acid was identified as the suppressed species. This study clearly shows that goethite, which is the predominant iron oxide of pipe deposits, alters both chlorine decay and DBP formation and should be considered when assessing water treatment plant operations and DBP monitoring site selection.     

Trihalomethane and Haloacetic Acid Disinfection By-Products in Full-Scale Drinking Water Systems

Trihalomethane (THM), haloacetic acid (HAA5), and total organic carbon (TOC) data provided by the Missouri Dept. of Natural Resources for drinking water treatment systems in the State of Missouri was analyzed for the years 1997–2001. These data indicated that a significant portion of systems exceeded the current regulatory limits of 80 and 60?μg/L for THM and HAA5 in these years. The vast majority of the treatment plants exceeding the regulatory limits were small plants with service populations less than 10,000 people. No significant temporal trend in either THM or HAA5 was noted for the years 1997–2001. This work suggests that the proposed use of a locational running annual average may have a significant effect on compliance. The use of chloramines (combined chlorine) versus free chlorine (HOCl/OCl?) as a residual disinfectant was shown to significantly reduce both THM and HAA5 in systems that treat their own water (primary systems), but did not have a significant effect in systems which purchase their water from primary systems (secondary systems). Comparison of finished water at the treatment plant versus in the distribution system suggested that a majority of THM and HAA5 may be produced within the plant as opposed to the distribution system. Hence, reducing these chlorinated disinfection byproducts within the treatment plant itself should be a key focus for achieving compliance, and supports Environmental Protection Agency disinfection byproducts compliance guidelines using enhanced coagulation.     

Anchoring of c-myc on nuclear matrix proteins in process of mouse thymic T lymphocyte proliferation induced by ConA

Epidemiologic investigations of the Latin America cholera epidemic have repeatedly implicated untreated drinking water and water touched by hands during storage as important vehicles for disease transmission. To prevent such transmission, we provided a new narrow-mouthed, plastic, water storage vessel and 5% calcium hypochlorite solution for home disinfection of stored water to a Bolivian Aymara Indian community at risk for cholera. We evaluated acceptance of this intervention and its effect on water quality. Each of 42 families in the study obtained water from a household well; fecal coliform bacteria were found in water from 39 (93%) of 42 wells and 33 (79%) of 42 usual water storage vessels. One group of families received the special vessels and chlorine (group A), a second received only the special vessels (group B), and a third served as a control group (group C). Water samples collected every three weeks from group A special vessels had lower geometric mean fecal coliform colony counts (P < 0.0001) and lower geometric mean Escherichia coli colony counts (P < 0.0001) than water from group B or C vessels. Adequate levels of free chlorine persisted in these vessels for at least 5 hr. The special vessels and chlorine solution were well accepted and continued to be used for at least six months. Use of the vessel and chlorine solution produced drinking water from nonpotable sources that met World Health Organization standards for microbiologic quality.     

在生活水消毒中使用二氧化氯替代氯气的安全性分析

分析了马钢第一能源总厂在生活水消毒中使用二氧化氯替代氯气在安全方面存在的问题,提出了在推广应用中必须完善的措施。