Journal - American Water Works Association
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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.
Journal - American Water Works Association - Tập 81 Số 8 - Trang 74-84 - 1989
Forward osmosis: Novel desalination of produced water and fracturing flowback Treatment and reuse of oil and gas (O&G) production wastewater in a cost‐effective and environmentally sound manner is critical to sustainable industrial development and for meeting stringent regulations. High salinity, free and emulsified hydrocarbons, silts and clays released from producing formations, and process additives common in O&G drilling wastewater render many conventional treatment technologies ineffective. Forward osmosis (FO) has been established as a promising solution for treatment and desalination of complex industrial streams and especially O&G exploration and production wastewaters. FO has achieved up to 85% water recovery from O&G wastewaters and can concentrate feed streams salinities to greater than 150,000 ppm. The process can operate as a stand‐alone technology with minimal pretreatment or be coupled with other advanced processes such as reverse osmosis or distillation. FO minimizes O&G wastewater disposal and produces clean water for intrabasin reuse. Recent developments in membrane fabrication, system configurations, and draw solutions are briefly reviewed.
Journal - American Water Works Association - Tập 106 Số 2 - 2014
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.
Journal - American Water Works Association - Tập 88 Số 7 - Trang 86-98 - 1996
Kinetics of <i>Nitrosomonas europaea</i> INACTIVATION by chloramine The effect of pH on the inactivation of Nitrosomonas europaea by chloramines was tested for a range of chloramine concentrations. Cell viability was assessed using the most probable number (MPN) technique and a culture‐independent bacterial viability test. For pH 7 to 9, N. europaea inactivation followed Chick‐Watson kinetics with n = 1 and k ranging from 2.5 × 10–03 L/(mgCl2 ·min) at pH 7 to 2.4 × 10–04 L/(mgCl2 ·min) at pH 9 in the bacterial viability–based tests. For the MPN‐based tests, k was approximately 1,000‐fold higher. Although CT 99 values from the MPN‐based experiments agreed with CT 99 reported elsewhere for ammonia‐oxidizing bacteria (AOB), the lower inactivation rates estimated from the bacterial viability tests were more consistent with AOB persistence in distribution systems, suggesting that MPN may overestimate chloramine biocide effectiveness. Finally, the counteracting effect of pH on N. europaea inactivation and chloramine decay indicates that pH control is likely to have a site‐specific effect on nitrification.
Journal - American Water Works Association - Tập 94 Số 10 - Trang 100-110 - 2002
When the Distribution System Needs a NAP: Tackling One City's Nitrification Action Plan Key Takeaways Recovering from nitrification can be difficult for a chloraminated drinking water system, so prevention, early detection, and swift mitigation are key. The City of Corpus Christi (Tex.) changed its complex yet flexible nitrification action plan to make it more stringent and action‐oriented. Using a mobile application in the field has enabled a near‐immediate response to water quality issues, including rechecking samples, flushing the sample station, or flushing nearby hydrants.
Journal - American Water Works Association - Tập 112 Số 1 - Trang 40-51 - 2020
Accelerated chloramine decay and microbial growth by nitrification in premise plumbing Chloramine decay rates are accelerated by nitrifier colonization of premise plumbing, which compromises the effectiveness of secondary disinfection. As expected, in the absence of nitrification, chloramine was more stable than chlorine; but in the presence of nitrification, the relative stability (and efficacy) of the two disinfectants could be reversed. The net result with chloramination can be higher levels of heterotrophic bacteria in the bulk water and pipe biofilms than would be found with free chlorine. These experimental trends were confirmed using field data collected from homes in systems with active nitrification.
Journal - American Water Works Association - Tập 101 Số 11 - Trang 51-62 - 2009
Nitrification in a Distribution System Symptoms indicative of nitrification occurred in the Ann Arbor, Mich., system during the late summer of 1990. The episode was characterized by decreases in monochloramine residual and increases in heterotrophic plate count (HPC) bacteria and nitrite. The cause of the nitrification was most probably a high dosage of ammonia combined with granular activated carbon filtration and discontinuation of the hydrant flushing program. The incident was ultimately halted by free chlorination of the distribution system. During free chlorination, an unexpected increase in HPC bacteria was observed in areas not affected by nitrification. Recommendations for future control of nitrification include more stringent control of ammonia, increased monitoring of nitrite and nitrate, development and implementation of a hydrant flushing program, and experimentation with the effects of pH.
Journal - American Water Works Association - Tập 85 Số 7 - Trang 95-103 - 1993
Biological Nitrification in Covered Reservoirs Containing Chloraminated Water Nitrification occurred in two covered finished‐water reservoirs in Southern California following a change from free chlorine to chloramine disinfection. The proliferation of autotrophic ammonia‐oxidizing bacteria was suspected to be the cause. Adverse water quality effects caused by the nitrification episodes included a rapid decline in the total chlorine and total ammonia‐nitrogen residuals and elevated levels of nitrite and heterotrophic plate count bacteria. As a result, the reservoirs were taken out of service and breakpoint‐chlorinated. This article examines the conditions leading to the development of nitrification in reservoirs containing chloraminated water, along with the measures that can be used to control the process.
Journal - American Water Works Association - Tập 80 Số 9 - Trang 109-114 - 1988
Estimating the Health Risks of Radon in Drinking Water By combining information about the occurrence, transport, exposure, and health effects of radon in drinking water, it has been estimated that over a period of 70 years (the average lifetime in the United States), between 2000 and 40 000 lung cancer fatalities are caused by inhalation of natural radon released from US public water supplies. The average concentration of radon in these water supplies generates a lifetime risk of about 1 in 10 000, the highest level of risk allowed for any contaminant currently regulated under the Safe Drinking Water Act. Reducing the levels of radon in drinking water, which would significantly lessen the risks to health, has been found to be feasible by either aeration or treatment with granular activated carbon.
Journal - American Water Works Association - Tập 79 Số 4 - Trang 153-158 - 1987
Radionuclides in Drinking Water: An Overview Although this article discusses radionuclides in general, its focus is on radium, uranium, and radon, which are the radionuclides of most concern to drinking water suppliers. Developed as the result of literature searches and interviews with personnel from the US Environmental Protection Agency and the California Department of Health Services, the article covers radionuclide chemistry, the occurrence of radionuclides, current and future regulations, treatment technologies, and monitoring.
Journal - American Water Works Association - Tập 79 Số 4 - Trang 144-152 - 1987
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