bluuebunny/crossref_metadata_2025_split huggingface dataset:
Three approaches for characterizing NOM
Authors: Krasner Stuart W. , Croué Jean‐Philippe , Buffle Jacques , Perdue E. Michael 
Published: February 2018

These techniques yield valuable insights into complex natural organic matter.Three research approaches to characterize natural organic matter (NOM) are available: (1) a nonperturbing approach, (2) an approach based on isolation–fractionation, and (3) an approach based on calculations. A nonperturbing approach has been used to assess the aromaticity and morphology of NOM. Characterization of isolated fractions has shown that the two main fractions—fulvic and hydrophilic acids—are in some points structurally different. Furthermore, reasonable estimates of several structural features of NOM have been obtained by analytical‐constraints calculations. Each approach yields valuable insights into NOM—its source and nature in watersheds, how seasonal variations affect it, and its potential to form disinfection by‐products. Each approach also yields insight into the relationship between NOM's structural and compositional properties.
Hydraulic mixing and free chlorine residual in reservoirs
Authors: Boulos Paul F. , Grayman Walter M. , Bowcock Robert W. , Clapp Jonathan W. , Rossman Lewis A. , Clark Robert M. , Deininger Rolf A. , Dhingra Ashok K. 
Published: February 2018

Interior sampling of a reservoir illuminates its mixing characteristics and supports the assumption of stratification or partitioning.An extensive sampling study of reservoir water quality was conducted in Azusa, Calif. Primary emphasis was placed on providing a better understanding of the dynamics of hydraulic mixing and free chlorine residual concentration distribution in the reservoir. The reservoir approached completely mixed behavior with two exceptions: a degree of short‐circuiting between the inlet and outlet (which significantly affected the T10 time) and the presence of a stagnant zone in the center core of the reservoir where there was less mixing and thus older water. These results support the assumption of stratification or partitioning in reservoirs. Regular field sampling is recommended to facilitate the effective management of distribution system water quality. In particular, interior sampling of reservoirs can provide useful information that could not be inferred otherwise.
Occurrence of nitrification in chloraminated distribution systems
Authors: Wilczak Andrzej , Jacangelo Joseph G. , Marcinko Joseph P. , Odell Lee H. , Kirmeyer Gregory J. 
Published: February 2018

Data from US distribution systems that chloraminate are evaluated as predictors of nitrification.Utilities in the United States that chloraminate were surveyed to evaluate the incidence of nitrification in distribution systems and determine whether nitrification can be predicted from basic system and water quality data. An estimated two thirds of medium and large US systems that chloraminate experience nitrification to some degree. About every fourth surveyed utility reported moderate to severe nitrification problems. In addition, every fourth utility did not know the extent of nitrification in its system. The incidence of nitrification was more frequent during summer or when the temperature was greater than 15°C (59°F); nevertheless, several sites sampled under cold water conditions—i.e., below 10°C (50°F)—also evidenced nitrification. No one water quality parameter by itself may be a good indicator of nitrification, but several important factors should be evaluated collectively—nitrite, nitrate, chloramine dosage and residual, ammonia, pH, heterotrophic bacterial counts, and dissolved oxygen.
Controlling nitrification in chloraminated systems
Authors: Odell Lee H. , Kirmeyer Gregory J. , Wilczak Andrzej , Jacangelo Joseph G. , Marcinko Joseph P. , Wolfe Roy L. 
Published: February 2018

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.
Toxicity of chlorine dioxide to adult zebra mussels
Authors: Matisoff Gerald , Brooks Gary , Bourland Brent I. 
Published: February 2018

Effective kills depend on the right combination of concentration and exposure time.Chlorine dioxide (ClO2) was evaluated as a control agent for adult zebra mussels using single, intermittent, and continuous exposures. A single 30‐min exposure to 20 mg/L ClO2 or higher concentration induced at least 50 percent mortality. NaOCl, KMnO4, and H2O2 were ineffective under the same conditions. Intermittent chemical exposure for 30 min each day indicated that ClO2 at concentrations of 10–20 mg/L can induce significant mortality over three to seven consecutive days (LC50 = 13.0 mg/L), but 1–5 mg/L ClO2 applied over 28 consecutive daily exposures are ineffective (<30 percent mortality). Identical intermittent exposure to NaOCl was ineffective at all tested concentrations up to 30 mg/L. Continuous exposure to ClO2 for four days was effective at concentrations >0.5 mg/L (LC50 = 0.35 mg/L), and 100 percent mortality at ClO2 concentrations >1 mg/L was achieved. NaOCl and KMnO4 were less effective. Pooled data yield median lethal dosages at which 50 percent mortality occurred of 14.5 and 82.5 mg h/L for ClO2 and NaOCl, respectively.
Improving GAC performance by optimized coagulation
Authors: Hooper Stuart M. , Summers R. Scott , Solarik Gabriele , Owen Douglas M. 
Published: February 2018

Optimized coagulation results in benefits ranging from DBP reduction to improved GAC run times.The effect of optimized coagulation on granular activated carbon (GAC) performance for removal of natural organic matter and control of disinfection by‐products was investigated. Coagulation optimized for total organic carbon (TOC) removal increased GAC run times by a factor of 2–3 over run times observed for GAC receiving conventionally treated water. The improved performance was mainly a result of reductions in influent TOC and pH after optimized coagulation, as compared with conventional pretreatment. Conventional coagulation prior to GAC was more cost‐effective than optimized coagulation, because of increased costs associated with the high alum dosages used in this study.
Evaluating plant performance with endospores
Authors: Rice Eugene W. , Fox Kim R. , Miltner Richard J. , Lytle Darren A. , Johnson Clifford H. 
Published: February 2018

Monitoring for indigenous spores of aerobic spore‐forming bacteria proves a viable method of assessing treatment plant performance.Spores of aerobic spore‐forming bacteria were used as microbial surrogates for evaluating drinking water treatment plant performance. A method for assaying for the microbial surrogate was developed. Various water sources were surveyed, and data were collected from coagulation and chlorine inactivation studies. Evaluations for spore removals and turbidity and particle removals were compared for pilot‐scale and full‐scale water treatment plants.
Assessing the risk posed by oocysts in drinking water
Authors: Haas Charles N. , Crockett Christopher S. , Rose Joan B. , Gerba Charles P. , Fazil Aamir M. 
Published: February 2018

Dose–response data on human exposure to oocysts of Cryptosporidium were analyzed to determine the dose corresponding to a stated risk level.A recent study of infection and illness in human volunteers subjected to controlled exposure to oocysts of Cryptosporidium parvum provided a suitable data base for dose–response analysis. The authors analyzed the study data, and using exponential and beta‐poisson dose–response models, arrived at an estimate of the waterborne concentrations associated with various risk levels.
Fire flow computation with network models
Authors: Boulos Paul F. , Rossman Lewis A. , Orr Chun‐Hou , Heath J. Erick , Meyer Michael S. 
Published: February 2018

The authors describe a sequential search procedure that produces improved fire flow estimates at each iteration.Water mains are usually designed to meet demands for fire‐fighting. Fire flow is the maximum flow rate available at a specified pressure, typically 20 psi (138 kPa). Water network models provide the capability to compute these flows at all points in a distribution system. This article presents a simple and rigorous sequential search procedure for computing fire flows using network models. The method can be applied manually between runs of the model, or it can easily be incorporated into existing computer codes. Examples illustrate the procedure's excellent convergence properties. Enhancement of water distribution system design, planning, and management is a principal benefit of the proposed methodology.
New York City: To filter or not to filter?
Authors: Okun Daniel A. , Craun Gunther F. , Edzwald James K. , Gilbert Jerome B. , Rose Joan B. 
Published: February 2018

USEPA's expert panel concluded that both filtration and watershed protection are necessary for New York City's water supply.Under the Surface Water Treatment Rule (SWTR), New York City is required to filter its Catskill–Delaware water supply unless it can meet the criteria to avoid filtration. A panel was appointed by the US Environmental Protection Agency (USEPA) in the summer of 1992 to advise the agency about whether to grant New York City permission to avoid filtration. The panel concluded that although the water quality criteria were met marginally, the requirements for watershed control were not met. The panel also concluded that the city would probably not be able to meet the water quality requirements of an enhanced SWTR, which would likely include, among other additional requirements, measures to control Cryptosporidium. Despite the panel's recommendation for filtration, USEPA granted New York City an avoidance of filtration first through 1993, then through 1996, 1999, and 2002. Although the city has negotiated a very useful watershed agreement with the upstate communities in the Catskill–Delaware watershed, the issues remain the same. This article assesses the issues involved.
Coliform bacteria and waterborne disease outbreaks
Authors: Craun Gunther F. , Berger Paul S. , Calderon Rebecca L. 
Published: February 2018

The authors evaluate the utility of coliforms as an indicator of the vulnerability of drinking water systems to outbreaks of waterborne disease.Coliform‐free tap water has previously been thought to be unlikely to cause waterborne disease. However, disease outbreaks (especially those caused by Giardia or Cryptosporidium) and endemic waterborne disease risks have been reported in water systems that have not violated either the 1975 or 1989 maximum contaminant level (MCL) for total coliforms. Focusing on the 1975 rule and using coliform data and investigative reports about outbreaks, the authors compared MCL violations for water systems that did and did not experience an outbreak. Coliforms were usually found in a public system during an outbreak investigation, but in the months before an outbreak, they were detected in only half of the systems and caused an MCL violation in only one fourth of them. The violation rate was not significantly different between community systems that experienced an outbreak and those that did not; usually both met the MCL. To safeguard the public against waterborne disease, microbiological monitoring must be supplemented with periodic sanitary surveys and activities that ensure adequate water quality.
Surveying arsenic occurrence
Authors: Frey Michelle M. , Edwards Marc A. 
Published: February 2018

Data from US arsenic occurrence surveys are used to estimate compliance violations given a range of possible arsenic standards.Three surveys of arsenic occurrence in US drinking water supplies were synthesized to estimate how possible arsenic standards would affect compliance. Detectable levels of arsenic (0.5 μg/L) were found in 73 percent of surface water sources and 58 percent of groundwater sources. For finished water, detectable arsenic occurred in 45 percent of surface water systems and 53 percent of groundwater systems. The authors' compliance projections for arsenic standards ranging from 2 to 20 μg/L agreed fairly well with initial estimates by the US Environmental Protection Agency. It was estimated that approximately 25 percent of all community water suppliers (11,550–11,890 systems) would violate an arsenic standard of 2 μg/L. Between 6 and 17 percent of systems (2,775–7,870) were projected to violate an arsenic standard of 5 μg/L, and 1–3 percent of systems (510–1,360) were estimated to violate an arsenic standard of 20 μg/L.
Reliability of surrogates for determining Cryptosporidium removal
Authors: Li Sylvana Y. , Goodrich James A. , Owens James H. , Willeke Gene E. , Schaefer Frank W. , Clark Robert M. 
Published: February 2018

Tests show 4–6‐μm polystyrene microspheres are an accurate and precise surrogate for determining Cryptosporidium log removal in bag filters.Testing of field‐scale bag filtration systems yielded results indicating that 4–6‐μm polystyrene microspheres can be used as a reliable surrogate for determining Cryptosporidium oocyst removal in bag filtration processes. A nearly perfect linear correlation was observed between log removals of 4–6‐μm polystyrene microspheres and Cryptosporidium parvum oocysts. The correlations between Cryptosporidium removal and other potential surrogates (including 4–6‐μm particle counts, 1–25‐μm particle counts, and turbidity) produced slopes that were substantially >1 and may vary geographically because of variations in raw water quality. The similarities and dissimilarities in log removal between Cryptosporidium oocysts and the potential surrogates for the bag filtration system resulted from their differences in size distribution.
Iron oxide–coated media for NOM sorption and particulate filtration
Authors: Chang Yujung , Li Chi‐Wang , Benjamin Mark M. 
Published: February 2018

Newly developed iron oxide–coated media offers several advantages over conventional sand media for NOM removal and particulate filtration.This study applied newly developed iron oxide–coated media (IOCM) to the removal of natural organic matter (NOM) and particulate filtration in drinking water treatment. The sorption capacity of IOCM for NOM directly depends on the amount of iron retained on the media surfaces and generally increases with the decrease of solution pH, the increase of empty bed contact time, and the concentration of Ca2+. Using olivine as the supporting medium significantly improved the performance of IOCM at neutral pH. Although the sorption capacity of IOCM is limited by the amount of oxides that can be coated on the media surfaces (about 5 percent by weight), results from the pilot studies indicated that frequent regeneration of the media (twice a week) can effectively maintain system performance at the desired level. The NOM‐laden IOCM was nearly completely regenerated using 3 bed volumes of 0.5 N sodium hydroxide solution, and NOM concentration in the regenerant was as high as 4,300 mg/L DOC. The sorption capacity of IOCM deteriorated mildly in a long‐term test, possibly because of loss of iron during the backwash cycles. Results from both bench tests and pilot studies also showed that IOCM outperformed regular sand in particulate filtration in terms of head loss buildup and turbidity breakthrough.
DBP occurrence survey
Authors: Arora Harish , LeChevallier Mark W. , Dixon Kevin L. 
Published: February 2018

Evidence gathered by the American Water System suggests USEPA should revisit the proposed Stage I DBP regulations, especially TOC removal requirements and related conditions for prechlorination.Results of a disinfection by‐product (DBP) survey and two years of distribution system DBP monitoring are presented for more than 100 treatment plants of the American Water System (AWS), the largest investor‐owned water utility in the United States. Monitoring of total organic carbon (TOC) indicated that 83 percent of the AWS surface water treatment plants that exceed a raw water TOC concentration of 2 mg/L will not receive predisinfection credit for the use of chlorine. With existing treatment practices, approximately 20 and 66 percent of the AWS water treatment plants studied will exceed the proposed Stage I and Stage II trihalomethane (THM) maximum contaminant levels (MCLs) of 80 and 40 μg/L, respectively. Similarly, approximately 16 and 52 percent of the AWS systems studied will exceed the proposed Stage I and II haloacetic acids (HAA5) MCLs of 60 and 30 μg/L, respectively. Based on these estimates, it is believed that Stage II requirements may significantly affect future water treatment practices and costs.
Predicting the formation of aldehydes and BOM
Authors: Paode Rajendra D. , Amy Gary L. , Krasner Stuart W. , Summers R. Scott , Rice Eugene W. 
Published: February 2018

A study finds that aldehyde formation in ozonated water is a function of alkalinity, ozone dosage, chlorophyll a, nonhumic fraction of DOC, and DOC.This research attempted to (1) identify water quality and water treatment parameters that can potentially influence the creation of biodegradable organic matter (BOM) and aldehydes and (2) derive correlations of BOM (estimated by measuring assimilable organic carbon [AOC] and biodegradable dissolved organic carbon [BDOC]) and aldehydes, with ozone dosage and water quality variables, through multiple regression analysis. Aldehyde formation was influenced by ozone dosage, alkalinity, nonhumic fraction of DOC, chlorophyll a, and DOC. Ozonated water BDOC level was a function of raw water BDOC concentration and ozone dosage, whereas AOC concentration in ozonated water was related to raw water AOC level, alkalinity, and ozone dosage. Multiple regression analysis showed good correlations of AOC, BDOC, and aldehydes with the variables listed.
Chloramination: its effect on distribution system water quality
Authors: Norton Cheryl D. , LeChevallier Mark W. 
Published: February 2018

Coliform concentrations were reduced or eliminated in two systems after chloramination replaced use of free chlorine.Postdisinfection using chloramines can limit coliform regrowth in pipeline biofilms and formation of disinfection by‐products (DBPs) in distribution systems. Two utilities that have had occurrences of total coliform converted from free chlorine to chloramines. Water in both distribution systems was monitored for biological and chemical quality for a year after the conversion. Coliform occurrences were eliminated in one system and reduced fourfold in the other. However, excessive concentrations of assimilable organic carbon (up to 375 μg/L) were characteristic of the latter system, as was pitting corrosion. Both factors may play a critical role in limiting coliform occurrence. Postdisinfection using chloramines rather than free chlorine has advantages including decreased coliform concentrations, decreased heterotrophic plate count and DBPs, and improved maintenance of a disinfectant residual. However, chloramination alone may not be sufficient to control coliform concentrations in all distribution systems.
Nonbiological surrogate indicators for assessing ozone disinfection
Authors: Chiou Chung‐Fan , Torres‐Lugo Madeline , Marinas Benito J. , Adams Jeffrey Q. 
Published: February 2018

The authors investigate the use of fluorescent‐dyed microspheres for assessing disinfection efficiency in ozone contactors.Fluorescent‐dyed polystyrene microspheres were used as nonbiological surrogate indicators for assessing ozone disinfection efficiency. Microspheres were exposed to various constant dissolved ozone concentrations ranging from 0.1 to 1.5 mg/L in a semibatch reactor. Experimental results showed that fluorescence decay rates were first‐order with respect to dissolved ozone concentration and independent from solution pH in the range of 6.2 to 8.5. Fluorescence intensities from individual microspheres were measured by flow cytometry. Resulting microsphere fluorescence intensity distributions at various ozonation contact times were analyzed by defining a fluorescence intensity threshold. Microspheres with fluorescence intensities above and below the threshold were considered equivalent to viable and nonviable cysts, respectively. Corresponding microsphere survivals correlated well with ozone disinfection data reported for Giardia cysts. The authors propose an experimental protocol for assessing full‐scale ozone contactor disinfection efficiency with fluorescent‐dyed microspheres.
Protozoa in river water: sources, occurrence, and treatment
Authors: States Stanley , Stadterman Kathleen , Ammon Louis , Vogel Paul , Baldizar Julie , Wright Denise , Conley Louis , Sykora Jan 
Published: February 2018

A dairy farm, sewage plant, and backwash water were among sources of protozoa in the raw water treated by the Pittsburgh, Pa., water utility.Giardia and Cryptosporidium were monitored monthly for two years to determine their occurrence in the Allegheny and Youghiogheny rivers, their source, and the efficiency of their removal by the Pittsburgh Drinking Water Treatment Plant. Sources investigated included a dairy farm stream, treated effluent from a sewage plant, and several samples from combined sewer overflows, all of which regularly contribute parasites to rivers. Raw, settled, filtered, and filter backwash waters were also sampled. Clarification and filtration generally control passage of protozoa into the drinking water, but small numbers of Cryptosporidium occasionally pass through even in the absence of treatment difficulties. Cysts and oocysts are also reintroduced into the drinking water plant via recycling of backwash water.
Assessing long‐term hydrologic effects of land use change
Authors: Bhaduri Budhendra , Grove Matt , Lowry Carmen , Harbor Jon 
Published: February 2018

The curve number technique for calculating runoff is modified to estimate lost groundwater recharge.Many communities are seeking to understand how future development may affect a watershed, and they are using this information to develop long‐term watershed management plans that protect their water supply. As part of work on the Cuppy‐McClure watershed in Indiana, a land use–runoff estimation technique was developed based on the local long‐term climate record. The technique, which uses the core of the US Department of Agriculture's curve number method, produces results that can be easily understood and used by managers, planners, and developers. The technique can estimate the effect of development on watershed hydrology, and it can quickly provide sensitivity analyses of alternative proposed land uses. Analysis of Cuppy‐McClure identified six subbasins that dominate the cumulative effects of proposed land uses and that should be the focus of watershed management.