bluuebunny/crossref_metadata_2025 huggingface dataset:
Barometric Efficiency
Authors: Rasmussen Todd
Published: July 2005

The barometric efficiency is used to describe how water levels in wells fluctuate in response to atmospheric pressure. Normally, water levels rise whenever the barometric pressure falls, and vice versa. This phenomenon is observed in both confined and in deep, unconfined aquifers. In confined aquifers, the change in water level is caused by a change in the force applied to the Earth's surface by the atmospheric pressure—higher atmospheric pressure causes a greater load, which is transferred to water at depth, causing the water pressure within the aquifer to rise. In unconfined aquifers, the response is because of the difference in air movement through the borehole vs. the unsaturated zone, resulting in a rapid change in water levels in an open borehole, followed by a slower change to the original level once the air pressure at the water table equals the air pressure in the borehole.
Climate and Society
Authors: Glantz Michael H.
Published: July 2005

At the turn of the twentieth century, scholars who wrote about the interplay between climate and society did so based on their perceptions of climate as a boundary constraint for the development prospects of a society. Perceptions of climate were used as an excuse to dominate societies in Africa, Asia, and Latin America. As a result, climate–society studies soon became viewed as a colonial ploy to control populations in developing areas in the tropics. Perhaps the most cited book in this regard was written by Ellsworth Huntington,
Climate and Civilization
, published in 1915 (1). In his view, inhabitants of the tropics were destined to accept lower levels of economic and social development because their climate setting was not conducive to lively (i.e., productive) human activity or an aggressive work ethic. According to Huntington, tropical climate was the main culprit causing people in the tropics to be less productive than people in temperate regions. Huntington argued that the temperate climate has an energizing effect on humans. With the growing belief that such an argument was racist in intent, Huntington's work was challenged, and discussion of the various ways in which climate might influence human behavior was stifled for decades, notwithstanding a few notable exceptions. One such exception is entitled
Climate and the Energy of Nations
(2) in which Markham referred to the “air‐conditioning revolution,” a revolution based on the development and spread of a new technology into the tropical areas. Markham asserted that technology brings islands of temperate‐zone climate into the tropics, thereby generating a more aggressive work ethic.
Overview: The Climate System
Authors: Dickinson Robert E.
Published: July 2005

The climate system consists of the atmosphere, cryosphere, oceans, and land interacting through physical, chemical, and biological processes. Key ingredients are the hydrological and energy exchanges between subsystems through radiative, convective, and fluid dynamical mechanisms. Climate involves changes on seasonal, year‐to‐year, and decadal or longer periods in contrast to day‐to‐day weather changes. However, extreme events and other statistical measures are as, or more, important than simple averages. Climate is seen to impact human activities most directly through the occurrence of extremes. The frequency of particular threshold extremes, as, for example, the number of days with maximum temperatures above 100°F, can change substantially with shifts in climate averages.
Rain Forests
Authors: Conti Aldo
Published: July 2005

Rain forests are, by definition, those forests that receive more than 2500 mm of rain each year. Rain forests are characterized by very dense vegetation dominated by tall trees and huge biodiversity. Rain forests exist in many parts of the planet, but most of them are along the equator, where the weather is stable throughout the year and there is never a dry season. Rain forests do not have seasons at all. The amount of rain is almost constant during the year, and the temperature seldom dips below 16°C. Rain forests cover 7% of the earth's land surface and 2% of its total surface, but are home to more than half of all animal and plant species. Despite the fact that rain forests cover less than 10% of the earth, they support a third of its plant matter. The largest tropical rain forest in the world is the Amazon Rain Forest, which lies in the countries of Brazil, Bolivia, Peru, Ecuador, and Colombia. There are rain forests in Africa, mainly in the Congo, and in Oceania.
Rainfall and Runoff
Authors: Endreny Theodore A.
Published: July 2005

Rainfall is generated by multiple weather patterns, summarized into frontal, orographic, and convective, that affect the duration and intensity of storm accumulation. Climate data analyses reveal regional and local trends in the seasonal and annual rainfall patterns of duration and intensity and have been reported in map and tabular form for durations of 5 minutes to 24 hours and a variety of return periods in Technical Papers 40 and 49 by the U.S. Weather Bureau and in HYDRO‐35 by the National Weather Service. A large variation in rainfall spatial and temporal duration and intensity has been observed for large and small area, long and short time events, and a combined system of drop‐size spectrometers, recording rain gauges, and microwave radar have helped to capture this detail nationally at the resolution of 5 minutely volume scans for 1 km
2
bins, aggregated to rain‐gauge‐corrected hourly totals at 4 km
2
bins. Internal warm and cold cloud precipitation dynamics, low‐level evaporation of falling precipitation, and distinction between rain, sleet, freezing rain, and snow still provide technological challenges. Time series plots of rainfall are referred to as hyetographs, maps of equal rainfall amounts are known as isopleths, and National Weather Service NEXRAD Doppler radar gauge‐corrected hourly 4 km
2
grid based rainfall maps are known as Stage III products. The spatial aggregation of rainfall point estimates from rain gauges is performed using surface fitting, weighting, and interpolation schemes, including the method of Thiessen polygons.
Relative Humidity
Authors: Ramis Climent , Romero Romualdo , Alonso Sergio
Published: July 2005

The air is a mixture of gases. The pressure exerted by air is the sum of the partial pressures exerted by each of its components (Dalton's law). The partial pressure exerted by water vapor, denoted as vapor pressure (
e
), is then a measure of the water vapor content in the atmosphere. A state can be represented by a point in a diagram whose coordinates are (temperature, vapor pressure) = (
T
,
e
).

For each temperature, a maximum vapor pressure exists that is known as the saturation vapor pressure (
e
s
). That saturation value cannot be surpassed, and if water vapor in excess occurs, condensation or sublimation results.
Coastal Fog Along the Northern Gulf of
M
exico
Authors: Erickson Timothy
Published: July 2005

Coastal fog is a problem for all traffic. It may be present as either a mesoscale or microscale phenomenon. Numerous conditions promote coastal fog. Coastal fog may exist in one of two ways, radiative that does not move or advective that does move. These two fog conditions are further broken down into several categories: radiative, frontal, maritime, advective, and conglomerate. Air, water, and dew point temperatures are the main variables that produce fog when all other atmospheric conditions are supportive. An inversion develops when the atmosphere warms with height, and an inversion must be present for any fog to form. For radiative coastal fog, 0 to 3 knots of wind speeds but no more will be needed to initiate coastal fog. For advective coastal fog, wind speeds of 4 to 12 knots are needed. Radiative coastal fog rarely envelopes the center of cities such as New Orleans. The buildings and pavement will hold heat longer than the surrounding countryside and will normally be enough to dissipate radiative fog. Depths between advective and radiative fogs vary from a few inches to hundreds of feet, with advective fog being the deepest.
Whirlwind
Authors: Meaden Terence
Published: July 2005

Whirlwinds can be divided into two main classes: the greater and the lesser whirlwinds. The former are represented by tornadoes, waterspouts, and funnel clouds. The latter are the momentum‐driven eddy whirlwinds and the thermal‐column wind devils and fire devils.
Desertification
Authors: Conti Aldo
Published: July 2005

Desertification is a degradation of the top layer of the soil that reduces its ability to support plant life and to produce food. As a result, the soil becomes dusty and dry, and it is easily carried away by erosion, which affects wild and domestic animals, wild plants and crops and, finally, humans. Desertification can be the result of human activities or of natural climate changes. In the latter case, the process is very slow and can take several thousand years to produce its effects. A common misconception about desertification is that it spreads from a desert core. The truth is that land degradation can occur where land abuse has become excessive. If it is not stopped in time, desertification spreads from that spot. Eventually, many of these spots merge and form a large homogeneous area. Another misconception is that desertification is the result of droughts. In fact, well‐managed land can recover from even a long period of drought with very little adverse effect as soon as rains return. But it is true that droughts can increase the pace of desertification already taking place.
Dew Deserts
Authors: Kidron Giora J.
Published: July 2005

The term dew deserts denotes deserts that receive dew precipitation throughout the year. Dew is defined as condensation of atmospheric vapor and does not include vapor condensation that stems from the wet ground, i.e., distillation. We term dew desert as a desert that receives at least 10 mm of dew in >0.1 mm of daily precipitation. As a result of dew precipitation, primary production in dew deserts is much higher, affecting the entire food chain.
Filtration With Granular Media
Authors: Ahmad Rasheed
Published: July 2005

Granular media filtration is a water treatment process that uses a porous medium through which water passes to remove particulates or suspended solids. Particulates that are removed by this process include microorganisms (bacteria, viruses, and protozoan cysts), clay and silt particles, colloidal and precipitated humic substances and other organic particulates from natural decay of vegetation, precipitates of an aluminum or iron coagulation process, calcium carbonate and magnesium hydroxide precipitates from lime softening, and iron and manganese precipitates.

For granular media filtration to be effective, source water must be pretreated. Chemical destabilization is an essential prerequisite for effective filtration. Chemicals used for particle destabilization are limited primarily to metal salts or cationic polymers as primary coagulants. Pretreatment may also include aeration or introducing an oxidant if water treatment aims to remove iron or manganese. Sometimes a filter aid polymer is added in the influent to the filter to improve particle capture efficiency.
Potential Risks of Waterborne Transmission ofEscherichiacoliO157:H7
Authors: Weihe Janice , LeChevallier Mark , Bukhari Zia
Published: July 2005

Escherichia coliO157:H7 has emerged as a serious human pathogen, capable of causing severe illness and even death in infected individuals. The annual number ofE. coliO157:H7 infections is estimated at approximately 40,000, and up to 250 deaths. Some researchers estimate that the number of infections is as high as 73,000 annually; is 11,000 of those are from transmission of the organism through ingestion of contaminated water. An increasingly common route of transmission is waterborne via recreational or municipal water sources. Recent incidences of waterborne outbreaks ofE. coliO157:H7 have shown a variety of potential sources for water contamination; the common link is fecal contamination combined with inadequate disinfection of the water supply.Escherichia coliO157 is susceptible to chlorination at levels similar to wildE. coli.Detection methods specific forE. coliO157:H7 in water samples are laborious and time‐consuming; however, new methods are in development.
Chemical Drinking Water Standards, Past, Present, and Future
Authors: Sullivan Patrick , Agardy Franklin
Published: July 2005

In today's chemically dependent society, studies undeniably demonstrate that America's drinking water contains numerous industrial chemicals, pesticides, and pharmaceuticals, as well as chemicals from water treatment processes. Each of these chemicals is allowed in drinking water because it is either (1) regulated by federal drinking water standards, which allow concentrations to a defined level, or (2) because many chemicals remain unregulated. Regulated chemicals are known to be hazardous to humans at high concentrations, yet are deemed safe for human consumption at low concentrations based on risk models that are unsupported by validated human studies or consider the risk of consuming mixtures of chemicals. Meanwhile, a vast number of potentially hazardous chemicals exist in our drinking water that remain unregulated. The ability for the USEPA to regulate chemicals in drinking water when the nation's chemical industry produces an estimated 2,000 new chemical compounds each year would seem impossible and, indeed, is impossible under the existing system. Currently, the USEPA must determine whether to regulate not less than five new chemicals from a proposed list of 42 chemicals, which do not even include pharmaceuticals, for inclusion within the drinking water standards. This approach demonstrates that drinking water standards are incapable of keeping pace with the number of unregulated chemicals that are found in our drinking water. When this failure is combined with the fact that standards are not even based on actual human toxicity studies, drinking water standards cannot be relied on to protect the public health. The alternative is to switch to technology‐based standards with the goal of removing the maximum amount of chemical pollutants. As the public becomes more aware of the hazards in their drinking water, they will have no recourse but to turn to litigation to redress these failings. The alternative, continued reliance on drinking water standards to protect the public health, will only perpetuate a false sense of security. Sadly, if federal, state, and local governments cannot effect a change to technology‐based standards, this issue may ultimately be settled by litigation.
Molecular‐Based Detection ofCryptosporidium Parvumin Water
Authors: Pokorny Nicholas J. , Carey Christine M. , Boulter‐bitzer Jeanine L. , Lee Hung , Trevors Jack T.
Published: July 2005

Molecular‐based methods are discussed for detecting the protozoan parasite,Cryptosporidium parvum, in water samples. These include antibody technologies, the polymerase chain reaction (PCR), and nucleic acid probes.
Modeling Chlorine Residuals in Urban Water Distribution Systems
Authors: Mohan Kumar M. S. , Munavalli G. R.
Published: July 2005

The water to be supplied to a community should be adequate in quantity to satisfy their demands and potable in quality to safeguard their health. It is not enough to treat water in the treatment works for safeguarding the health of consumers without trying to take adequate steps in preventing deterioration of the water quality in a distribution system. Treatment can be adequate to provide an excellent product for the consumer at the plant outlet, but it is inadequate to overcome inferior protective measures in the distribution system (1). There are various causes for which the potable water may turn to an obnoxious liquid in the distribution system and become unfit for drinking as could be found after quality assessment. The various causes of deterioration of water quality are pipe materials, constituents of water, intermittent supply, cross connections, dead‐end pipes, service reservoirs, commissioning of new distribution system without disinfection, and breakages (2). The significant constituents of water generally include residual chlorine, natural organic matter, nutrient concentrations, temperature, and pH of water. The distribution system plays an important role in assuring a good quality of water to the consumer.
Health Effects of Microbial Contaminants and Biotoxins in Drinking Water
Authors: Venkatapathy Raghuraman , Boutin Brenda , Moudgal Chandrika , Bruce Robert
Published: July 2005

Contaminated, untreated, or inadequately treated municipal water is known to transmit disease‐causing pathogens such as bacteria (Escherichia coli, Salmonella paratyphi, Bacillus typhosus, Vibrio cholerae), fungi (Penicillium, Candida), viruses (polio, reo, coxsackie), and protozoan parasites (Giardia lamblia, Cryptosporidium parvum, Entamoeba histolytica). In addition, some algae are not pathogenic, but produce biotoxins that may be harmful to humans at high concentrations. Treatment of source waters using disinfectants such as chlorine, chloramine, chlorine dioxide, ozone, and ultraviolet radiation has resulted in a dramatic reduction of waterborne diseases in the world today. However, waterborne pathogens may still be transmitted because of ingestion of water from contaminated service mains; microorganism growth in pipes and fittings; biofilms; sewage; inhalation of aerosols; or dermal contact with contaminated water such as in swimming pools. Waterborne diseases are usually acute in nature, are rarely fatal, and are often characterized by gastrointestinal symptoms. The severity and duration of illness is generally greater in people with weakened immune systems such as children, the elderly, and the immunocompromised, such as people suffering from AIDS.
Health Effects of Commonly Occurring Disinfection Byproducts in Municipal Water Supplies
Authors: Venkatapathy Raghuraman , Moudgal Chandrika , Boutin Brenda , Bruce Robert
Published: July 2005

Disinfectants such as chlorine, chloramine, chlorine dioxide, ozone, and ultraviolet radiation have been used to disinfect water containing disease‐causing waterborne pathogens at water treatment plants throughout the world. However, the chemical disinfectants can react with dissolved organic and inorganic constituents in treated water to form disinfection byproducts (DBPs). Although over 600 DBPs have been identified, despite recent improvements in analytical instrumentation, less than 50% of the total organic halides have been accounted for in drinking water. From the present knowledge of occurrence and health effects, the DBPs of concern are trihalomethanes, haloacetic acids, bromate, chlorate, and chlorite, although other DBPs, such as acetonitriles, acetaldehydes, ketones, nitromethanes, and other alkanes, have also been identified in drinking water. Epidemiological studies indicate an association between chronic ingestion of drinking water and increased risk of rectal, bladder, and colon cancer in humans, but these studies do not indicate whether the observed health effects are because of one or more of the hundreds of DBPs that are also present in drinking water. The disinfectants can also be hazardous at high concentrations, but toxicological studies show that their toxicity is likely not relevant at the low concentrations encountered in drinking water.
Filtration
Authors:   National Drinking Water Clearinghouse
Published: July 2005

Filtration is the process of removing suspended solids from water by passing the water through a permeable fabric or porous bed of materials. Groundwater is naturally filtered as it flows through porous layers of soil. However, surface water and groundwater under the influence of surface water is subject to contamination from many sources. Some contaminants pose a threat to human health, and filtration is one of the oldest and simplest methods of removing them. Federal and state laws require many water systems to filter their water. Filtration methods include slow and rapid sand filtration, diatomaceous earth filtration, direct filtration, packaged filtration, membrane filtration, and cartridge filtration.
Water Treatment Plant Residuals Management
Authors:   National Drinking Water Clearinghouse
Published: July 2005

Water treatment plants produce a wide variety of waste products as well as safe drinking water. These residuals may be organic and inorganic compounds in liquid, solid, and gaseous forms depending on the source of raw water and the type of treatment processes, commonly, coagulation/filtration, precipitative softening plant, membrane separation, ion exchange, granular activated carbon.
Lime Softening
Authors:   National Drinking Water Clearinghouse
Published: July 2005

Hard water can cause scaling problems in water heaters and soap does not lather well in hard water. Therefore, some water utilities soften water to improve its quality for domestic use. Lime softening is best suited to groundwater sources, which have relatively stable water quality. The combination of variable source water quality and the complexity of the chemistry of lime softening may make lime softening too complex for small systems that use surface water sources.

Although lime softening has been used successfully by groundwater systems serving fewer than 3,000 people, it is unlikely to be suitable for treating groundwater in systems serving 500 or fewer people unless those systems have some form of contract or satellite operation that would enable a trained operator to monitor the treatment process. Prefabricated lime softening equipment is available for small systems. Also, there is an American Water Works Association Standard for quicklime and hydrated lime (ANSI/AWWA B202‐93) that provides purchasers, manufacturers, and suppliers with the minimum requirements, including physical, chemical, packaging, shipping, and testing requirements.

Either hydrated lime [Ca(OH)
2
] or quicklime (CaO) may be used in the softening process. The choice depends upon economic factors, such as the relative cost per ton of the two materials as well as the size and equipment of the softening plant. Hydrated lime is generally used more in smaller plants because it stores better and does not require slaking (producing a chemical change in lime by combining it with water) equipment. On the other hand, quick‐lime costs less per ton of available calcium oxide and is thus more economical for use in large plants.

Softened water has high causticity and scale‐formation potential; hence, recarbonation is employed to reduce pH and mitigate scaling of downstream processes and pipelines. Onsite combustion generation of carbon dioxide (CO
2
) or liquid CO
2
is the most common source of carbon dioxide for recarbonation.
Membrane Filtration
Authors:   National Drinking Water Clearinghouse
Published: July 2005

A membrane or, more properly, a semipermeable membrane, is a thin layer of material capable of separating substances when a driving force is applied across the membrane.

Once considered a viable technology only for desalination, membrane processes are increasingly employed for removal of bacteria and other microorganisms, particulate material, and natural organic material, which can impart color, tastes, and odors to the water and react with disinfectants to form disinfection byproducts (DBP). As advancements are made in membrane production and module design, capital and operating costs continue to decline.

The pressure‐driven membrane processes discussed in this fact sheet are microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO).
Leak Detection and Water Loss Control
Authors: Lahlou Zacharia Michael
Published: July 2005

Utilities can no longer tolerate inefficiencies in water distribution systems and the resulting loss of revenue associated with underground water system leakage. Increases in pumping, treatment and operational costs make these losses prohibitive. To combat water loss, many utilities are developing methods to detect, locate, and correct leaks.
Diatomaceous Earth Filtration for Drinking Water
Authors: Bhardwaj Vipin , Mirliss Mel J.
Published: July 2005

Diatomaceous Earth (DE) filtration is a process that uses diatoms or diatomaceous earth—the skeletal remains of small, single‐celled organisms—as the filter media. DE filtration relies upon a layer of diatomaceous earth placed on a filter element or septum and is frequently referred to as pre‐coat filtration. DE filters are simple to operate and are effective in removing cysts, algae, and asbestos from water. DE has been employed in many food and beverage applications for more than 70 years and was used specifically to filter potable water during WWII. Since then, it has been used to produce high‐quality, low‐cost drinking water. DE filtration is currently one of the U.S. Environmental Protection Agency's (EPA) approved technologies for meeting the requirements of the Surface Water Treatment Rule (SWTR) and is most suitable for small communities that need to comply with the rule.
Reservoirs, Towers, and Tanks Drinking Water Storage Facilities
Authors: Bhardwaj Vipin , Metzgar Chris
Published: July 2005

After water leaves the treatment plant but before it reaches the customer, it must be adequately and safely stored. This Tech Brief explores the various aspects of water storage.
Cross Connection and Backflow Prevention
Authors: Bhardwaj Vipin , Reed Bethany
Published: July 2005

When drinking water is transported to a consumer, it is possible for contaminants to be introduced in the distribution system. This situation may occur due to connections between potable water lines and non‐potable water sources or by a water flow reversal, resulting in contaminated water. This Tech Brief, discusses cross connections and backflow, and explores ways to prevent these situations.
Water Meters
Authors: Satterfield Zane , Bhardwaj Vipin
Published: July 2005

Any viable business must be able to determine how much product it is making and selling and if that product is profitable. Water is a business. And, the best way for a water utility to measure or account for the water produced and then sold is by using water meters. This Tech Brief, discusses the different types of meters, their applications, and their importance for a water utility business.
Answering the Challenge
Authors: Reahl Eugene R.
Published: July 2005

As a result of the need for ever‐expanding drinking water supplies in an area short on such new sources, the City of San Diego purchased an electrodialysis reversal (EDR) system in 1998 to desalinate tertiary treated wastewater. The EDR system was installed to produce a low TDS product from treated wastewater, then blend and supply this high‐quality irrigation water to golf courses, parks, plant nurseries, and other water users. The initial plant produced 3.3 mgd of blended water.

The city elected to use EDR because of its lower costs compared with the conventional use of MF‐RO. EDR also operates at higher water recovery, and with no chemical feed required other than an allowable use of free chlorine in the feedwater.

As a result of the success of the “alternative water supply” program, the EDR system has been expanded to where it will produce a blended flow of up to 12 mgd by early 2005.

This successful installation has been verified by recent testing of EDR and MF‐RO, showing that EDR is up to 40% less costly based on present worth analysis of capital, infrastructure, and long‐term O&M costs.
Use of Redox Potentials in Wastewater Treatment
Authors: Inniss Enos C.
Published: July 2005

Effective process control requires an understanding of where the process is with respect to reaction potential and completion. Online measurements allow for greater monitoring of the state of the process from flowrates to chlorine residuals. A measure of dissolved oxygen in the system is useful until anoxic and anaerobic conditions are encountered. Once those environmental conditions are achieved, as is the case with biological nutrient removal (BNR), the ability to measure a wider range of conditions may be achieved with oxidation–reduction potential (ORP).
Ion Exchange—Use of Magnetic Ion Exchange Resin For
DOC
Removal
Authors: Slunjski Marin
Published: July 2005

Natural organic matter, measured as dissolved organic carbon (DOC), is a major problem in treatment processes for production of drinking water. DOC gives water color and can react with disinfectants to produce by‐products that have adverse health affects. It also interferes with the treatment processes, makes them less effective, and results in increased chemical additions.

Strong base anion exchange resins have a high affinity for DOC. They are currently used in packed columns in the production of drinking water in Norway and the United States. These applications are sensitive to fouling by suspended solids and are limited to smaller scale applications.

MIEX
®

resin, a new approach was developed in Australia by the South Australian Water Corporation, Orica Australia Pty. Ltd. and CSIRO.

It uses a new ion exchange resin designed for DOC removal in a continuous flow, stirred tank system that is not affected by suspended solids (i.e., turbidity).
Competitive Adsorption of Several Organics and Heavy Metals on Activated Carbon in Water
Authors: Mohan Dinesh , Singh Kunwar P.
Published: July 2005

In practice, the water/wastewater/effluents to be treated are multicomponent mixtures. Therefore, other organic or inorganic substances influence the efficacy of activated carbons. In the recent past, most of the research work has been focused on the removal of single solute from its pure solution or a particular solute from a solution having ill‐defined chemical character. The other reports available are addressed to the removal of gross organic/inorganic substances, which are measured in terms of BOD or COD from water/wastewater. In actual practice, the treatment of wastewater by activated carbon normally involves a variety of adsorbates competing for adsorption sites on the carbon surface. Thus, a thorough understanding of the competitive effect on various organic/inorganic compounds on carbon adsorption is a must. Unfortunately, very few reports/papers about the competitive adsorption on activated carbon in aqueous solution are available. Thus, a need exists to explore the current status of the competitive adsorption of various organic/inorganic substances from water/wastewater on activated carbons. Multiion systems received less attention than single ion systems.

The adsorption in multicomponent systems is complicated because of the solute–solute competition and the solute‐surface interaction involved. Multicomponent interactions take place at the active adsorption sites where the solid‐liquid phase equilibrium will emerge showing a different capacity of single solute with a new set of isotherm systems. The interpretation of the multicomponent systems has proved to be complex and may be the function of one or all of the following parameters: ionic radii, electronegativity, system pH, and the availability of the active sites on the adsorbent.
Mixing and Agitation in Water Treatment Systems
Authors: Mavros Paul
Published: July 2005

Mixing is one of the primary processes involved in water and wastewater treatment. In this article, the state of the art in mixing and impeller design is presented.
Ozone–Bromide Interactions
Authors: Siddiqui M.
Published: July 2005

As utilities consider changing their primary disinfection practices from free chlorine to ozone to provide pathogen control while minimizing chlorinated disinfection by‐product (DBP) formation, the potential for producing ozonation DBPs like bromate ion must be addressed. This article focuses on the interactions, not only of molecular ozone and bromide ion, but also of radical species with bromide ion. The data evaluations include discussions of reaction products, potential for bromate ion formation, reaction kinetics, and the effect of various water quality parameters and treatment conditions on bromate ion formation. Based on evaluation of existing data, areas requiring new or intensified research efforts are identified.

An additional aspect of this article is a presentation of most available data on the minimization of bromate ion formation during ozonation. A summary of bromate ion removal processes after ozonation has been incorporated.
Dechlorination
Authors: Ahmad Rasheed
Published: July 2005

Dechlorination is the practice of removing all or a specified fraction of total residual chlorine. In potable water practice, dechlorination is used to reduce the residual chlorine to a specified level at a point where the water enters the distribution system. Dechlorination has been beneficial for waters that are burdened with high concentrations of ammonia nitrogen and organic nitrogen. In some cases where taste and odor control is a severe problem, control is achieved by complete dechlorination, followed by rechlorination. This removes the taste‐producing nuisance residuals and prevents the formation of nitrogen trichloride (NCl
3
) in the distribution systems. Dechlorination of wastewater and power plant cooling water is required to eliminate residual chlorine toxicity, which is harmful to the aquatic life in the receiving waters. Other special applications requiring dechlorination are ahead of demineralizers, boiler makeup water, certain food plant operations, bottled water, and the beverage industry. In these cases, the dechlorination process is arranged to remove all residual chlorine.
Persistence of Pathogens in Water
Authors: Nasser Abid M.
Published: July 2005

Natural water sources become contaminated with pathogenic micro‐organisms by the discharge of inadequately treated wastewater. Four major pathogen groups can be found in wastewater: over 100 types of enteric viruses, 7 types of pathogenic bacteria, 10 types of protozoan parasites, and 6 types of helminthes of health significance to humans and animals. The concentration of pathogenic micro‐organisms in wastewater is affected mainly by the amount of precipitation, the season of the year, and the socioeconomic status of the community. For most pathogenic micro‐organisms, the methods of detection are expensive, time‐consuming, and difficult to perform. Therefore, data on the prevalence of pathogenic micro‐organisms in wastewater effluents and natural water sources is limited to types for which a detection technique was developed. The recently developed molecular biology‐based techniques enhanced our capability in detecting human pathogenic micro‐organisms in water sources.
Review of Parasite Fate and Transport in Karstic Aquifers
Authors: Blanford William J.
Published: July 2005

Every year in the United States, cases of waterborne illness are generally characterized bygastrointestinalproblems (vomiting, diarrhea, etc.). However, these same symptoms can be more serious and even fatal in certain groups, such as the young, elderly, and those with compromised immune systems. Furthermore, viral pathogens found in groundwater are linked to chronic diseases such as adult onset diabetes and myocarditis. Recognizing that preventing contamination of water sources is the first step in the multiple barrier approach to drinking water protection, the Interim Enhanced Surface Water Treatment Rule (IESWTR) and the Disinfectants/Disinfection Byproducts Rule (DBPR) were released in 1999. The two rules will provide additional protection of public water supplies and address microbiological contamination. The rules address the risks of the trade‐offs between disinfection necessary for microbial inactivation and disinfection by‐products. The requirements of 40 CFR 141.72(b) are consistent 99.99% removal and/or inactivation of viruses and 99% removal ofCryptosporidiumoocysts. The code gives public water suppliers the option to demonstrate compliance through pilot plant studies or other means that combine filtration techniques with disinfection as in EPA 1999 Microbial and Disinfection Byproducts Rules Simultaneous Compliance as in Guidance Manual.

Presently, only surface water systems and systems using groundwater under the direct influence of surface water are required to disinfect their water supplies. Though historically considered free of microbial contamination, most recent research has shown that aquifers can be readily contaminated by pathogens. To lessen the requirement for disinfection and to protect water resources, water suppliers have sought to use natural systems to treatCryptosporidium. Thus, there is a critical need for information regarding the transport and fate of pathogens during water infiltration into subsurface systems.
Disinfectants
Authors: Venkatapathy Raghuraman , Weintraub June , Wright J. Michael
Published: July 2005

Disinfection of drinking water was instituted at a time when waterborne infectious diseases were the primary focus in public health. The use of disinfectants such as chlorine, chloramine, chlorine dioxide, ozone, and ultraviolet radiation has resulted in a reduction in the outbreak of diseases such as cholera and polio in many parts of the world. The choice of disinfectant is dependent on their availability, ease of use, cost, and their efficacy in disinfecting water. Some disinfectants commonly used in water treatment plants are not stable in water for long periods of time, which reduces their disinfection efficacy. Current practices to control pathogens in drinking water include using a combination of disinfectants, coagulation, and filtration. A main disadvantage of using disinfectants in drinking water is their ability to react with organic and inorganic matter in water to form disinfection byproducts that may be of health concern. The disinfectants can also be hazardous at high concentrations, but toxicological studies suggest that their toxicity is likely not relevant at the low concentrations encountered in drinking water.
MeasuringCryptosporidium ParvumOocyst Inactivation Following Disinfection With Ultraviolet Light
Authors: Bukhari Zia
Published: July 2005

Historically, ultraviolet light inactivation ofCryptosporidium parvumoocysts was considered ineffective; however, recently it was demonstrated that the methods for measuring oocyst inactivation can yield erroneous results and that neonatal mouse infectivity assays, which indicated that very low UV doses are highly effective for oocyst inactivation, are needed for determining inactivation of UV‐treated oocysts. The moral, ethical, and financial constraints of using mouse infectivity has generated the need for more user‐friendly alternative methods for measuring oocyst inactivation. Cell culture infectivity assays are considered promising alternatives, and this article discusses a cell culture‐immunofluorescence (IFA) procedure, which following optimization, yielded results similar to those expected from mouse infectivity assays. This cell culture‐IFA procedure will be an invaluable analytical tool for control or bench scale studies usingC. parvumoocysts and the same water matrices as those intended for use in UV reactor validation studies.
Ultraviolet Irradiation
Authors: Siddiqui M.
Published: July 2005

Ultraviolet irradiation (UV) is a potential alternative to chlorination for drinking water disinfection. UV provides disinfection without producing the problematic disinfection by‐products of chemical disinfectants such as chlorine. During retrofitting of UV to an existing potable water treatment process or during design of a new installation, there can be significant benefits in reexamining the overall disinfection strategy for the treatment plant and the water distribution system.
Water Filtration
Authors: Ahmad Rasheed
Published: July 2005

The most universally used particulate removal technology in drinking water treatment is filtration. Filtration is the process of removing particulate matter or suspended solids from water by passing the water through a porous medium, permeable fabric, or membrane. The commonly available water filtration processes are rapid gravity filtration, slow sand filtration, diatomaceous earth filtration, membrane filtration, cartridge filtration, and special types of filtration. A variety of modes of operation are available such as downflow, up‐flow, multiple layer, biflow, radial flow, semicontinuous (moving bridge), continuous (media recycle), variable voidage, and pebble matrix. All of these have the same basic objectives: to produce a filtrate that is clear and contains very few particles and to provide a medium‐cleaning process so that operation may be continued with the same medium or by replacing the old medium. The same principles of filtration apply to all these processes.
Zebra Mussel Control Without Chemicals
Authors: Sanderson Charles H. , Molden T. C.
Published: July 2005

Methods to control the zebra mussel became top priority in many municipalities and industries that use water from the Great Lakes. In desperation, chemicals (mostly chlorine) became the quick fix; however, the toxic discharge back into the fresh water lakes increased the fish kill and killed other wildlife species. The U.S. Army Corps of Engineers sought other (nonchemical) means to control the spread of the mussel threat and set up workshops in which academic and industry professionals were invited participate.

The National Research Council listed several technologies more friendly to the environment than chlorine and other chemical biocides. Among those identified were
filtration systems, thermal techniques, electric pulse and pulse plasma techniques, ultraviolet treatment, acoustic systems, magnetic fields, deoxygenation
, and
antifouling coatings
.
Filtration Water Treatment
Authors: Ahmad Rasheed
Published: July 2005

Filtration systems employed at water treatment facilities use a porous medium through which water passes to remove suspended solids. A number of methods have been developed to meet this objective. Currently, rapid gravity filtration is the most commonly used filtration technology in developed countries for drinking water treatment. However, developments in filtration technology have increased the popularity of the other types of filtration systems. Filters can be classified into different types depending on the rate of flow (e.g., rapid sand and slow sand filters), media (single and dual media filters), hydraulic arrangement (gravity and pressure filters), direction of flow (up‐flow and down‐flow filters), and removal depth (cake and deep filters). The two most common types of filtration system used in water treatment are gravity filtration and pressure filtration. The gravity filtration system has two major types: rapid gravity filtration and slow sand filtration. The pressure filtration system commonly consists of four types: rapid rate pressure filtration, diatomaceous earth filtration, membrane filtration, and cartridge filtration.
Plankton
Authors: Juhl Andrew
Published: July 2005

Plankton are aquatic organisms living in the water column that drift, float, or swim only weakly. The term describes a lifestyle used by a tremendous diversity of organisms including plants, animals, and bacteria that range from less than 1 µm to more than 1 m in length. Several common categorization schemes are used to group plankton depending on shared ecological roles, size, and whether they are plankton for their entire lives, or only for a portion of their development. Despite this diversity, consistent patterns of plankton abundance have been documented throughout the world's oceans, both horizontally with distance from land, and vertically with increasing depth. Seasonal patterns of plankton abundance are also well known for many locations. Although individually small, planktonic organisms are numerous. In aggregate, they have global impacts. Plankton are the base of aquatic foodwebs, providing food for larger aquatic organisms, including commercially valuable species. Plankton influence global climate by taking in atmospheric carbon and releasing volatile sulfur compounds. They also supply half of the Earth's oxygen production. Finally, the remnants of plankton settle through the water column, eventually forming the sediments that cover most ocean bottoms.
Distribution and Dynamics of Gas Hydrates in the Marine Environment
Authors: Trehu Anne M. , Torres Marta E.
Published: July 2005

Gas hydrate is an ice‐like substance that forms at low temperature and high pressure when adequate amounts of water and low molecular weight gases are present. In nature, gas hydrates containing primarily methane are widespread in the shallow sediments on continental margins. Under certain geologic conditions, enough methane hydrate may be present for these deposits to represent a fossil fuel resource for the future. Concentrated deposits of gas hydrate near the seafloor form the substratum for unique assemblages of microbes similar to those found at hydrothermal vent sites. Destabilization of gas hydrate in marine sediment may occur as a result of artificial structures, resulting in catastrophic structural collapse. Because methane is a powerful greenhouse gas, sudden destabilization of gas hydrate on a large scale can have an impact on global climate. Indeed, past episodes of climate change linked to gas hydrate destabilization have been documented in the geologic record.
Marine Sources of Halocarbons
Authors: Moore Robert M.
Published: July 2005

Halogens, particularly chlorine and bromine, are important in the atmosphere as catalysts for destruction of stratospheric ozone. The oceans are a major reservoir of dissolved halogens and act as a supply to the atmosphere through the production of sea salt aerosols and organic trace gases. The latter, having in many cases much longer lifetimes in the atmosphere than sea salt particles, are able to mix to high altitude and, on photolysis, release halogen radicals. Organoiodine compounds, notably methyl iodide, have marine sources but, on account of their short atmospheric lifetime, normally release iodine at lower elevations. Nevertheless, the transport of marine‐produced methyl iodide in the atmosphere represents an important source of this biologically essential element to the continents. Marine macrophytes are well established as sources of numerous halogenated gases, and marine phytoplankton are known to be significant sources of bromoform and dibromomethane. While the fluxes of methyl halides between the ocean and atmosphere have been estimated within reasonable limits, the processes that produce them are a subject of active research. Many halocarbons are consumed in seawater by a combination of chemical and biological processes with the result that the direction of flux between ocean and atmosphere can vary temporally and spatially in both magnitude and direction.