Journal - American Water Works Association
1551-8833
0003-150X
Mỹ
Cơ quản chủ quản: John Wiley & Sons Inc. , WILEY
Lĩnh vực:
Chemistry (miscellaneous)Water Science and Technology
Các bài báo tiêu biểu
The Occurrence of Disinfection By‐products in US Drinking Water Data were gathered on the presence of disinfection by‐products (DBPs) in drinking water and on the impact of treatment processes on DBP formation and control. Thirty‐five water treatment facilities were selected to provide a broad range of source water qualities and treatment processes. Trihalomethanes were the largest class of DBPs detected (on a weight basis) in this study, with haloacetic acids being the next most significant DBP fraction. Formaldehyde and acetaldehyde, by‐products of ozonation, were also demonstrated to be produced by chlorination. Cyanogen chloride was found to be preferentially produced in chloraminated water.
Tập 81 Số 8 - Trang 41-53 - 1989
Health implications of arsenic in drinking water Definitive answers regarding arsenic health risks at low exposures will be elusive without additional research. The adequacy of the current maximum contaminant level (MCL) for arsenic is being evaluated by the US Environmental Protection Agency. If recent theoretical estimates of chronic effects and cancer risks prove accurate, the current MCL may not effectively protect health. Knowledge of arsenic pharmacokinetics and mechanisms in humans, however, is not complete enough to provide a definitive answer, and current epidemiologic evidence is too inconsistent and too fraught with uncertainty regarding arsenic exposure to be helpful in assessing low‐level risks.
Tập 86 Số 9 - Trang 52-63 - 1994
Organic Contaminant Removal by Coagulation and Related Process Combinations This article synthesizes work done over the past few decades to better understand the removal of organic contaminants by the coagulation process, alone and in combination with other processes. Published data demonstrate that coagulation can substantially reduce the concentration of certain organic contaminants found in drinking water supplies, and that an understanding of the fundamental mechanisms by which coagulation removes organic contaminants facilitates qualitative prediction of the types of contaminants likely to be removed and the effects of process control variables. Data also demonstrate that removal of organic contaminants by coagulation can be influenced by other processes, such as preozonation, and that coagulation can influence the removal of organic contaminants by subsequent treatment processes, such as filtration and activated carbon adsorption.
Tập 80 Số 5 - Trang 40-56 - 1988
Formation and Control of Bromate During Ozonation of Waters Containing Bromide The results of this study show that the ozonation of waters containing bromide may produce bromate, with ozone dosage playing a critical role. The appropriate staging of ozone through two or three chambers, however, has the potential to minimize ozone residual and bromate formation while still meeting C × T criteria. The addition of hydrogen peroxide (the PEROXONE process) may increase the formation of bromate. As the pH of ozonation was lowered, the ozone dosage necessary to meet C × T criteria dropped, and less bromate was produced. The authors conclude that a better understanding of the mechanisms of bromate formation is required before it can be fully controlled.
Tập 85 Số 1 - Trang 73-81 - 1993
Ozonation: Assessing Its Role in the Formation and Control of Disinfection By‐products An increasing number of chlorinated by‐products resulting from disinfection practices will be regulated as a result of the 1986 amendments to the Safe Drinking Water Act. Consequently, ozone is being employed more frequently for the control of trihalomethanes and other disinfection by‐products (DBPs). To evaluate the impact of ozonation on the formation and control of DBPs in drinking water, studies were conducted at four utilities. Treatment modifications were made on the process trains at each plant either at full or pilot scale to incorporate ozone in the treatment process. Samples were collected before and after ozone was added to the treatment train and were analyzed for selected DBPs. In general, treatment trains that employed ozonation followed by chloramination were the most effective in reducing trihalomethanes and other halogenated DBPs. Increases were found, however, in some compounds such as chloropicrin and aldehydes.
Tập 81 Số 8 - Trang 74-84 - 1989
Factors Affecting DBP Formation During Ozone–Bromide Reactions Ozonation of waters containing bromide ion leads to the formation of organic and inorganic by‐products. By‐product formation is influenced by bromide ion concentration, the source and concentration of organic precursors, pH, ozone dosage, temperature, and alkalinity. Both organic and inorganic by‐products increased when bromide ion concentration increased but decreased with an increase in alkalinity. Organic by‐products were found to increase with a decrease in pH, whereas bromate formation was favored by a high pH. In general, bromoform concentration first increased, then diminished, as the dosage of ozone was increased. Both ozonation and incubation temperatures had a positive effect on the formation of bromoform and bromate. PEROXONE appears to favor bromate formation over organic by‐product formation, whereas the addition of ammonia reduces both bromate and organic by‐products.
Tập 85 Số 1 - Trang 63-72 - 1993
Controlling nitrification in chloraminated systems Data on nitrification occurrence and control in chloraminated distribution systems point to several strategies to preserve water quality during distribution and storage. Of US water systems that chloraminate, an estimated two thirds experience some degree of nitrification in the distribution system. Measures utilities use to control nitrification were investigated through field sampling, evaluation of utility data, laboratory tests, and case studies of systems that have evaluated or attempted to control nitrification episodes. Effective control methods included instituting periodic breakpoint chlorination, reducing the available ammonia concentration, increasing chloramine residuals, cleaning the distribution system, and decreasing system detention time. Some control methods were superior for controlling a specific nitrification episode, whereas others showed more promise for reducing the long‐term potential for nitrification occurrence. According to the authors, the most important steps utilities can take to control nitrification are to thoroughly understand their systems' chloramine chemistry and to establish an effective monitoring strategy.
Tập 88 Số 7 - Trang 86-98 - 1996
Design Considerations for GAC Treatment of Organic Chemicals Procedures with which to determine preliminary fixed‐bed adsorber design calculations for single solutes are described. Correlations are proposed and verified to determine single‐solute isotherm and mass transfer parameters. These correlations are used in combination with a simplified version of a mass transfer model to calculate mass transfer zone lengths and the maximum amount of water that may be treated. The calculated results can then be used to select the optimum fixed‐bed adsorber operation. Comparisons of this simplified procedure with actual pilot‐plant and full‐scale data are presented to demonstrate its validity.
Tập 79 Số 1 - Trang 74-82 - 1987
Bromate ion formation: a critical review Bromate, which forms upon ozonation of water containing bromide ion, can be minimized before production by chemical or physical–hydrodynamic factors or after its formation by removal techniques. As utilities consider changing their primary disinfection practices from free chlorine to ozone in order to minimize the formation of chlorinated disinfection by‐products (DBPs), the potential for producing ozonation DBPs such as bromate ion must be addressed. Important research findings of bromate ion formation studies over the past five years, which have resulted in substantial understanding of ozone‐bromide ion interactions, are summarized. Areas of incomplete information are identified, and a complete list of references is provided.
Tập 87 Số 10 - Trang 58-70 - 1995
Adsorption of Inorganic Compounds by Activated Carbon Little, if any, work has been performed within the water‐supply field relevant to the use of activated carbon for removing trace metals and compounds. The authors extrapolate the results of tests performed elsewhere, and for reasons other than cleansing water supplies, and come to the conclusion that activated carbon under appropriate conditions of pH can do a proper job of purification.
Tập 64 Số 6 - Trang 386-391 - 1972