bluuebunny/crossref_metadata_2025 huggingface dataset:
Municipal Water Supply: Ozonation
Authors: Kim Jaehong
Published: July 2005

Since the first full‐scale application of ozone for water treatment in late 1800s, ozone has been widely used in municipal water supplies in many countries. The primary goal of the ozonation process in water treatment is often disinfection, but ozonation is also used in many other applications, including taste and odor control, color removal, oxidation of manganese and iron, flocculation enhancement, oxidation of natural organic matter (NOM) and accompanying promotion of its biodegradability, and control of chlorination byproducts (1). Recently, the application of ozone as a disinfectant has been receiving more attention because of its effectiveness in treating pathogens, such as oocysts of the protozoan parasiteCryptosporidium parvum, which have shown strong resistance to chlorine‐based disinfectants (2, 3).

In water treatment, ozone can be applied either at the early stage of treatment (i.e., preozonation) or after other treatment processes, including conventional processes such as coagulation/flocculation and sedimentation. Ozone is sometimes used with hydrogen peroxide or UV to promote the formation of hydroxyl radicals in advanced oxidation processes (AOPs). Due to the increased biodegradability of organic matter after ozonation, ozonation is typically followed by biological filtration to remove biodegradable organic matter and to minimize microbial regrowth in the distribution system. Ozone decomposes relatively fast, so secondary disinfectants such as free chlorine and monochloramine are often applied after ozonation to provide residual disinfectant in the distribution system.
Ozone With Activated Carbon for Drinking Water Treatment
Authors: Ahmad Rasheed
Published: July 2005

Ozone is a very strong oxidant and powerful disinfectant that has been used for water treatment in many countries. In addition to its strong oxidation and disinfection properties, ozone has other beneficial effects. Ozone aids in coagulation and flocculation, acts effectively in taste and odor removal, does not produce halogenated disinfection by‐products (DBPs) except in bromide‐rich water, extends filter runs due to lower rates of head loss, and helps in removing natural organic matter in conventional treatment or in activated carbon adsorption processes. However, the use of ozone has limitations. It does not produce a persistent disinfectant residual. Ozone is relatively costly, and it produces suspected carcinogens like bromates in bromide‐rich water.
Particulate Matter Removal by Coagulation
Authors: Ahmad Rasheed
Published: July 2005

Coagulation is used in water treatment plants as a pretreatment step to remove particulate matter and dissolved materials, especially natural organic material (NOM). Examples of particulate matter in surface water include clay and silt particles, bacteria, viruses, and protozoan cysts such as
Giardia
and
Cryptosporidium
. NOM is formed in surface water from biodegradation and/or transformation of plant and animal material in the watershed. Although the removal of particulate matter continues to be an important reason for using coagulation, recent concern about carcinogenic by‐products has emphasized that the coagulation process must also optimize the removal of NOM to reduce the formation of disinfection by‐products.

The major purposes of coagulation include destabilizing colloidal particles, removing color and precursors of disinfection by‐products, enhancing flocculation, improving filtration, and pretreating to prolong the life of granular activated carbon contactors.
Particulate Matter Removal by Filtration and Sedimentation
Authors: Ahmad Rasheed
Published: July 2005

Sedimentation is the step in conventional water treatment systems that follows flocculation and precedes filtration. Its purpose is to enhance the filtration process by removing particulate matter. Sedimentation requires that the water flow through a basin at a slow enough velocity to permit the particulate matter to settle to the bottom of the basin before the water exits the basin. The equipment required for this process includes a rectangular, square, or circular settling basin. The basin includes provisions for inlet and outlet structures and a sludge collection system. In addition, sedimentation systems are optionally equipped with tube or plate settlers to improve performance.

The settling velocity of the particles or particulate matter is governed by the particle size, shape, density, and water viscosity (which varies with temperature). Stokes' law describes the terminal velocity of discrete spherical particles in a laminar flow regime. In an ideal up‐flow rectangular settling tank, all particles that have a settling velocity greater than the liquid up‐flow velocity will be captured. This up‐flow velocity is more commonly called the hydraulic overflow rate or surface loading rate. The surface overflow rate is the primary design parameter for sizing sedimentation basins. This rate is defined as the rate of inflow (
Q
) divided by the tank surface or floor area (
A
). Units are typically rated in gallons per day per square foot, gallons per minute per square foot, or cubic meters per hour per square meter. Design hydraulic overflow rates vary with the nature of the settling solids, the water temperature, and the hydraulic characteristics of the sedimentation basin.
Particulate Removal
Authors: Ahmad Rasheed
Published: July 2005

Particulate removal is extremely important in providing safe and aesthetically pleasing drinking water. A wide variety of particulate matter is present in raw water sources as a result of either natural events or human activities. Other particulates, mainly chemical precipitants, are created intentionally to remove other contaminants. Naturally occurring particulates are clay, silt, metal oxides, biological and organic detritus, and biota such as bacteria, viruses, protozoa, and algae. Chemical precipitants and particulate oxides, the other type of particulate, are produced when coagulants or chemical oxidants are used.

There are two categories of particulate removal process technologies in drinking water treatment: the particle alteration and particle production process and particle separation process technology. Coagulation and chemical oxidation are considered particle alteration and particle production processes. Sedimentation, filtration, flotation, and membrane processes fall under particle separation technology. For effective and complete particulate removal, a particle alteration and particle production process should be followed by a particle separation process.
Settling Tanks
Authors: Voutchkov Nikolay
Published: July 2005

Settling tanks (clarifiers) are key wastewater treatment facilities used for gravity separation of settleable solids contained in the wastewater. Depending on their geometrical shape settling tanks could be rectangular or circular. Clarifier shape most suitable for a given application depends on a number of factors and has to be selected based on a cost‐benefit analysis. Depending on their function, settling tanks are classified in two general categories: primary and secondary. The main purpose of the primary settling tanks is to remove suspended solids from the wastewater treatment plant influent. Secondary clarifiers are located downstream of the plant's biological treatment facilities, such as aeration basins or tricking filters, and are used to separate the biomass generated during the secondary treatment process from the treated plant effluent. Key design criteria used for sizing primary settling tanks are surface overflow rate and hydraulic detention time, while secondary settling tanks are usually designed based on surface and solids loading rates. Recommended values for these design criteria according to various design guideline sources are presented in a table format.
Slow Sand Filtration and the Impact of
Schmutzdecke
Authors: Rooklidge Stephen J.
Published: July 2005

The use of sand media to filter drinking water dates to the early nineteenth century; and rural areas are the primary benefactors of slow sand technology due to the passive nature of the treatment process and the availability of large tracts of land necessary for filter construction. The source water flows by gravity through the filter column, and biomass forms at the sand/water interface (schmutzdecke) that provides an effective layer for removing pathogenic microorganisms. Although source water quality is an important design consideration when communities consider this technique as a treatment method, slow sand filtration is one of the oldest drinking water treatment techniques and is still a viable method of biological water treatment best suited for raw water sources low in turbidity and suspended solids.
Synthetic and Natural Organic Removal by Biological Filtration
Authors: Ahmad Rasheed
Published: July 2005

The use of biologically active gravity filters to produce biologically stable water has been recognized in Western Europe for at least two decades. In the United States, biological filtration for drinking water treatment is recently gaining interest because of increased use of ozone as a disinfectant. The increased interest also stems from recent stringent water quality regulations. When ozone is used as a predisinfectant in conventional water treatment, rapid gravity filters become biologically active. Without using ozone, there are a variety of approaches to achieve biological filtration or biological treatment of drinking water. Biological treatment can be achieved by slow sand filtration, bank filtration, ground passage, and granular activated carbon (GAC) contact. Although the approaches differ substantially in process configuration, they all have two common and critically important characteristics. The first characteristic is that all of the processes are of the biofilm type in which bacteria are stably retained in the process by natural attachment to a solid surface, such as sand and carbon. The second characteristic is that the processes select oligotrophic bacteria or those bacteria especially adapted to function when their substrate concentrations are very low.
The State of the Water Industry—2004
Authors: Maxwell Steve
Published: July 2005

The water and wastewater treatment industry continues to be an evolving and often unpredictable business, and the year 2003 did not disappoint. The ongoing corporate consolidation in the industry produced surprises and new directions, whereas the headlong rush toward privatization seemed to falter, or at least slow a bit. Water resource issues and water management controversies continued to climb onto the front pages of the popular media; water quality scares, water rights battles, and water security issues gained significant public exposure. Wide‐ranging debate over how to best fund the vast future capital needs of the water business began to take center stage. The extensive regional droughts of 2002 are still fresh in the minds of many people. And although water stocks outperformed the general stock market this year, there still seem to be no big winners emerging.
Water Security: An Emerging Issue
Authors: Purohit Hemant J. , Devotta Sukumar
Published: July 2005

Identification of the links between rapidly growing populations and shrinking freshwater supplies is the essential first step in making water use sustainable. Various models are proposed for prediction of water usage based on climate data. Even water security has been correlated with food security by modeling (8). Yates (9) presented an integrated assessment model for continental scale runoffs where the limiting data for the spatial and temporal variability of freshwater resources is the constraint. An analysis of Western Europe's and Africa's freshwater runoff, which spans a range of climate variability, was performed at varying levels of spatial aggregation and at both monthly and annual time steps. Model results showed that regional runoff characteristics were lost beyond a data aggregation of 1° × 1° resolution. A macroscale hydrological model, designed to simulate stream flow from climatic inputs over a large geographic domain, has been proposed by Arnell (10). In the case of Hydrological Model of WaterGAP 2 (WGHM), the model tuning has aimed at achieving a good representation of the long‐term average discharges (11). It has a strong positive effect on the performance of all proposed water availability indicators.
Well Head Protection
Authors: Makinde‐Odusola Babalola
Published: July 2005

Groundwater, especially karst aquifers (1) or groundwater under the direct influence (2) of surface water, is vulnerable to contamination from possible contaminating activities (PCAs) (3) related to land use. A wellhead protection (WHP) plan (WHPP) essentially includes the integrated proactive management practice(s) that protect the quality of groundwater that is a source of drinking water. WHP is part of an integrated (from source to consumer's tap) multibarrier system to reduce risks to public health from drinking water. WHP fits into the World Health Organization's (WHO's) Water Safety Plan that recommends the use of hazard analysis and critical control points (HACCPs) as a risk management tool in drinking water operations (4). In the United States, many public water systems (PWSs) are required to conduct source water assessment (SWA) (3, 5, 6, 7). For PWSs that source from groundwater, a WHPP can be part of their SWA program (SWAP). A PWS must develop its WHPP in accordance with guidelines established by regulatory agencies (1, 2, 3).
Drinking Water Quality Standards (DWQS)‐UnitedStates
Authors: Makinde‐Odusola Babs A.
Published: July 2005

In 1974, the U.S. Congress, through the Safe Drinking Water Act (SDWA), created the first‐ever mandatory national program to protect consumers from harmful contaminants in drinking water. There have been several amendments to the Act—the most recent in 1996. The SDWA requires the U.S. Environmental Protection Agency (EPA) to set national drinking water quality standards (DWQS). The EPA has set primary and secondary DWQS for chemical, physical, radiological, and microbiological contaminants listed in Tables and. More Americans are now served by water systems without health risk violations since the EPA began tracking violations around 1980.
Evaluation of Microbial Components of Biofouling
Authors: Smith Stuart A.
Published: July 2005

Detecting the occurrence of biofouling and assessing its impact involve a range of analytical techniques, including informed observation and inspection of well components, interpretation of hydraulic and water quality testing, and direct analysis of microbial components of biofouling. The latter is the subject of this article.

Symptoms: Indirect Analysis

clogging (both formation/well and pump/discharge systems).

corrosion

alteration of water quality in pumped samples

distinct coating on surfaces visible during inspections, such as borehole television surveys.

Such symptoms are indications of biofouling and should trigger analysis to determine the nature of the biofouling.
Seawater Temperature Estimates in Paleoceanography
Authors: Cortese Giuseppe
Published: July 2005

Temperature, together with salinity, determines the density of seawater, and therefore, it strongly influences its circulation and sinking characteristics.

In turn, the important role oceanic circulation and deep‐water formation play in past, present, and future climatic change lend a special significance to the estimate of past seawater temperature.

As the past values of this important climatic variable in the distant, geological past are impossible to measure directly, a variety of indirect methods, so‐called “proxies,” have been developed. These methods are usually based on the fossil faunal/floral composition of sediment core samples, as a close link exists between species occurrences/abundances and environmental variables.

Semiquantitative (e.g., faunal provinces indexes) and quantitative (e.g., transfer functions, neural networks) techniques are therefore applied to reconstruct past sea surface water variables, including temperature.

Additionally, several geochemical methods have been recently developed to estimate past ocean temperatures by measuring chemical elements (Mg/Ca, Sr/Ca) or organic compounds (alkenones), which are either incorporated in the organism shell, or produced during its life cycle.
Marine Stock Enhancement Techniques
Authors: Davis Jana
Published: July 2005

The United Nations estimates that as many as 75% of the world's fishery stocks are fully exploited, severely depleted, or overexploited and are therefore not eligible for further exploitation to meet growing demands for fishery products. Due to the pressure on fishery populations, several management techniques have been developed. Traditional fishery management seeks to limit the catch of wild fishery stocks. Aquaculture activities, increasing in number, aim to raise aquatic food organisms in captivity. Stock enhancement techniques have been developed to bolster population sizes in the wild, either by providing habitat for habitat‐limited populations or by providing hatchery‐raised juveniles for recruitment‐limited populations. The latter form of stock enhancement has been controversial for a variety of reasons, including viability and health of hatchery‐raised organisms. In addition, success of stock enhancement efforts is often difficult to quantify. Evaluation of this management technique requires laborious efforts to follow hatchery‐raised organisms over time and develop knowledge about wild con‐specifics.

Despite the controversy and difficulty in assessing the success of stock enhancement programs, stock enhancement may be a required step in the management of species or stocks that are extremely depleted.
Marine Colloids
Authors: Santschi Peter H.
Published: July 2005

Aquatic colloids, nanoparticles and macromolecules in the 1 nm to 1 µm size range, are characterized by large interfacial energies and scatter light. Colloids are most often separated from seawater through ultrafiltration. They are characterized by physical techniques, such as diffusion, permeation, or light scattering, and can be imaged by atomic force and electron microscopy. Chemically, they are composed mostly of organic macromolecules, which make up 20–30% of marine dissolved organic carbon (DOC). Marine colloidal organic matter (COM) contains biologically resistant heteropolycondensations, such as humic‐type molecules (geopolymers), and products of carbon fixation and consumption such as exopolymeric substances (EPS) excreted by microorganisms. Both geopolymers and biopolymers are amphiphilic with charged and uncharged groups, and contain strong metal‐binding ligands, rendering them metal‐ and radionuclide sequestering agents. Therefore, colloids in the ocean can act as vectors of metal and radionuclide removal and of solubilization, depending on the biomolecule, as well as modifiers of metal bioavailability in delicately balanced marine ecosystems. In addition, marine colloids are also important in their response to global change, as they enhance the sinking flux of carbon, and thus, play a role in global carbon cycling.
The Permanent Service for Mean Sea Level
Authors: Jevrejeva S. , Holgate S. , Woodworth P. L.
Published: July 2005

Since 1933, the Permanent Service for Mean Sea Level (PSMSL) has been responsible for the collection, publication, analysis and interpretation of sea level data from the global network of tide gauges. It is based at the Proudman Oceanographic Laboratory (POL). The PSMSL is a member of the Federation of Astronomical and Geophysical Data Analysis Services (FAGS) established by the International Council of Scientific Unions (ICSU). The mission of the PSMSL is to provide the community with a full Service for the acquisition, analysis and interpretation of sea level data. Aside from its central role of operation of the global sea level data bank, the PSMSL provides advice to tide gauge operators and analysts. It occupies a central management role in the development of the Global Sea Level Observing System (GLOSS).
The Role of Oceans in the Global Cycles of Climatically‐Active Trace‐Gases
Authors: Upstill‐Goddard Robert C.
Published: July 2005

The contributions to global warming and atmospheric chemistry made by several atmospheric trace gases with significant marine sources and/or sinks are summarized. Of these, carbon dioxide, methane, nitrous oxide, dimethyl sulphide, and carbonyl sulphide are discussed in more detail. For CO
2
, the global partitioning of anthropogenic emissions is reviewed briefly, and the physical and biological mechanisms by which CO
2
is processed and transported into the ocean interior are discussed. Uncertainties in the global source estimates of methane and nitrous oxide are reviewed briefly. For these gases, and for dimethyl sulphide and carbonyl sulphide, the principal biological and/or biologically related processes driving their marine cycling and the major sites of their production and/or consumption in marine waters are reviewed.
Major Ions in Seawater
Authors: Angelis Marie De
Published: July 2005

Seawater
contains all of the natural elements. However, its composition is dominated by relatively few ionic species. These species, which comprise >99.8% of the mass of the total dissolved salts in the ocean, are known as the major ions and are defined as dissolved species having a concentration in seawater of >1 mg kg
−1
(1 ppm). Na
+
and Cl
−
alone account for 86% of all dissolved chemical species in seawater.

The source of Cl
−
, and most anions in seawater, is
outgassing
of the Earth's interior, or
volcanic emissions
. The majority of the major cations are derived from the effects of continental weathering and are delivered to the ocean via rivers. The gross composition of seawater is the result of the partitioning of elements between continental rock and seawater over geologic time. The major ions represent the more soluble elements, which have preferentially partitioned into seawater.
Water Waves
Authors: Liang Nai Kuang
Published: July 2005

A water wave is a variation in the elevation of the water surface in an ocean, sea, or lake. It influences beach morphology, maritime structures, and human activities very much. Different water waves are distinguished by their wavelengths. Tides, tsunamis, and wind waves are well‐known water waves. The wind wave has the shortest wavelength among the three water waves. During the Second World War, a wind wave forecasting scheme was developed for Normandy landing operations. Modern ocean wave modeling is based on the energy balance equation. Because the wind varies tremendously, a typhoon or hurricane may generate huge waves. This storm usually causes disasters.

As the typhoon is still far away, the swell may arrive, because the swell energy usually propagates faster than the typhoon moves. The swell height if enhanced, as the typhoon approaches a station. This is the same as the well‐known Doppler effect. There were cases when swell heights were larger than those inside the typhoon because the moving velocity was close to the group velocity of the swell.
The Ocean in Climate
Authors: Sarachik Edward S.
Published: July 2005

Earth's present climate is intrinsically affected by the ocean—the climate without the ocean would be different in many essential ways: Without the evaporation of water from the sea surface, the hydrological cycle would be different; without ocean heat transport and uptake, the temperature distribution of the globe would be different; and without the biota in the ocean, the total amount of carbon in the atmosphere would be many time its current value. Yet, while we may appreciate the role of the ocean in climate, the difficulty and expense of making measurements below the ocean's surface has rendered the vast volume of the ocean a sort of
mare incognita
. Why is the ocean so important in Earth's climate, and which of its properties are of special significance for climate? How have we learned about the ocean and its role in climate, and what more do we need to know?
Coastal Water Pollutants
Authors: Kumar Upadhyayula V. K.
Published: July 2005

Domestic sewage and industrial wastes, dissolved or suspended in water, are conveniently disposed of by running them, either untreated or after partial treatment, directly into coastal embayments and estuaries or into open coastal waters. Because of the increase in population density, causing a shift from individual septic systems to local collection networks and centralized treatment plants, the use of the marine environment as a dump for liquid waste is increasing at an even faster rate than that of the population growth of the coastal regions.

The sea has seemed a natural dumping ground for waste materials, but we now know that this is not acceptable practice in many cases. Some of the kinds of wastes man has disposed of in the sea or might consider disposing of include domestic sewage, industrial wastes, radioactive wastes, heat, agricultural drainage, brines from saline water conversion or chemical recovery plants, and insoluble junk. However, a first principle is that if such wastes are mixed with sufficiently large quantities of seawater, their undesirable qualities will be diluted to unobjectionably low levels. The problem then reduces to one of dilution and that of possible reconcentration to objectionable or dangerous levels, generally by biological agencies.

Thus this article is mainly oriented toward three basic issues

types and forms of pollutants that coastal waters receive

assessment of receiving waters

effect of pollutants on coastal habitat.
Larvae and Small Species of Polychaetes in Marine Toxicological Testing
Authors: Qiu Jian‐Wen , Wong Ming Hung
Published: July 2005

Polychaetes have been widely used as bioassay organisms in acute, chronic, and life‐cycle tests since the 1960s to examine the toxicity of metals, sediment, sediment pore water, municipal effluents, petroleum hydrocarbons, pesticides, and other synthetic organic chemicals. In total, 49 polychaete species have been used in bioassays, of which most are small species that are available from laboratory culture. Relatively few studies have used polychaete larvae as bioassay organisms, although they are usually at least an order more sensitive than the adults of the same species. This entry provides a brief introduction of the commonly used polychaete species and types of bioassays, as well as some general conclusions about the bioassay results.
Coagulation and Flocculation
Authors: Exall Kirsten
Published: July 2005

Coagulants and flocculants are commonly used in the destabilization and aggregation of suspended solids during water and wastewater treatment. Both inorganic salts and organic polymers may be used as coagulants, and various synthetic and natural organic polymers are applied as flocculants. Organic matter is quite well removed during coagulation, although it often requires a higher coagulant dosage. Other factors that influence the effectiveness of coagulants and flocculants are pH, temperature, mixing conditions and other ions present in the water. In order to maximize efficiency of contaminant removal while minimizing residuals, careful coagulant or flocculant dose selection and control are essential.
Ion Exchange and Inorganic Adsorption
Authors: Kadirvelu K. , Goel Jyotsna
Published: July 2005

Ion exchange and adsorption are two physical processes that have been effectively applied for inorganic ion removal. The presence of inorganic ions in water is of major concern for water quality because they can interfere with legitimate use of water for various applications. Inorganic ions, particularly heavy metals, are seriously questionable because of their toxicity and threat to human life and the environment.

This article highlights these two processes by defining their use, factors affecting them, and involved process mechanism. Factors affecting the adsorption and ion exchange processes, such as adsorbent nature, its chemistry, solution pH, presence of foreign ions, and temperature, have been enumerated with findings of various available research studies. Adsorption capacities of various adsorbents for inorganic ions have been summarized and compared. Various physicochemical properties of adsorbents used for inorganic ion removal has also been provided for better understanding of the adsorption mechanism involved. This article also presented an insight into the combined mechanism of two processes, which concludes both the processes as a unified one. Functional groups of various ion exchangers are used for inorganic ion removal. A review of potential adsorbents for inorganic removal is also presented.
Analysis of Aqueous Solutions Using Electrospray Ionization Mass Spectrometry (
ESI
MS
)
Authors: Henderson William
Published: July 2005

Electrospray ionization mass spectrometry (ESI MS) is a powerful analytical technique that can be used to analyze species dissolved in aqueous (and other) solutions. The technique operates by spraying a solution of the compound to be analyzed through a charged metal capillary, producing a spray of charged liquid droplets. These are then evaporated producing gas phase ions that undergo mass analysis. Any species that is ionic, or can generate a charged adduct by oxidation, protonation, deprotonation, and so on is potentially analyzable by ESI MS. Numerous applications of the technique in the analysis of biochemical and chemical substances in aqueous solutions have been developed.
Solubility of Chemicals in Water
Authors: Yaws Carl L. , Narasimhan Prasad K. , Lou Helen H. , Pike Ralph W.
Published: July 2005

Correlations are presented for the solubility of chemicals in water. A wide variety of compounds are covered—alcohols, ketones, ethers, aldehydes, acids, acetates, amines, monochloroalkanes, and monobromoalkanes. The new correlation provides reliable solubility values down to very low concentrations (parts per million range). The correlation is based on the boiling point of the compound. The correlation and experimental data are in favorable agreement. The results are useful in process engineering for wastewater minimization.
Solubility of Hydrocarbons in Salt Water
Authors: Yaws Carl L. , Narasimhan Prasad K.
Published: July 2005

Correlations for variation of water solubility with salt concentration are presented for hydrocarbons. The results for solubility in salt water are applicable to the complete range of salt concentrations, including water without salt (
X
 = 0) to water saturated with salt (
X
 = 358, 700 ppm(wt)). The correlation and experimental results are in favorable agreement. The results are provided in an easy to use tabulation which is especially applicable to rapid engineering usage with the personal computer or hand calculator.
Adsorption Capacity of Activated Carbon for Water Purification
Authors: Yaws Carl L. , Narasimhan Prasad K.
Published: July 2005

Adsorption on activated carbon is an effective method for water purification. In this article, results for the adsorption capacity of activated carbon for removing organic chemicals from water are presented for a wide variety of substances—alcohols, ketones, aldehydes, acetates, benzenes, chloroalkanes, chloro‐olefins, and bromoalkanes. The results use the adsorption capacity as a function of the adsorption potential of the chemical in the aqueous liquid. The correlation constants are displayed in an easy to use tabular format that is especially applicable to rapid engineering usage. Correlation results and experimental data are in favorable agreement.
Environmental Photochemistry in Surface Waters
Authors: Young Mark A.
Published: July 2005

Photochemistry in surface waters is an important environmental process, inextricably linked to global geochemical cycles, climate, and biological activity. A wide variety of chromophores reside in natural waters and exhibit significant spectral overlap with the available incident solar flux. Potential chromophores can include dissolved organic material, inorganic nitrate and nitrite ions, metal complexes, colloidal minerals, and various small molecules. Photoexcitation of these chromophores leads to the generation of a range of reactive radical and ionic intermediates that then subsequently react with biogenic and anthropogenic material present in the water system. Possible intermediates include superoxide, singlet oxygen, hydroxyl and peroxyl radicals, redox active metal centers, and organic radical cations. In many surface waters, reactive intermediates are photoproduced with sufficient rates to influence, or even dictate, the lifetime and chemical fate of pollutants, the concentration and availability of critical nutrients and substrates for biogenic processes, and the residence time of carbon in the hydrosphere. The chromophoric starting material is itself degraded in the process, which can significantly influence the optical properties of the surface water as well as the photochemical activity. A brief description of the important species and processes that play a role in environmental photochemistry in surface waters is provided, along with some estimates of relative importance.
Distilled Water
Authors: Conti Aldo
Published: July 2005

Water is never pure in nature. It normally contains some salts and minerals in solution and even bacteria and pollutants. Most of these substances, salts and minerals, in particular come from rocks and soils with which the water has been in contact. All these impurities make water useless for some purposes. It must be cleaned of pollutants and bacteria for human consumption, for instance. But for some other uses, even salts and minerals are dangerous. At home, in our vapor iron, water should be free of calcium carbonate that forms a layer on the heating resistor and eventually breaks it. The easiest method of purification is distillation, during which water is heated until it turns into vapor. The vapor is then collected on a cold surface, where it condenses. Because salts and other impurities do not vaporize, they normally remain in the boiling solution. Distilled water is never perfectly pure, because there are substances with nearly the same boiling point as that of water and some liquid droplets can be carried by the steam. Nevertheless, distilled water can be 99.9% pure and, if needed, can be distilled a second time. Distillation is very efficient in removing heavy metals, radionuclides, and solid particles, and it kills bacteria and viruses.
Infiltration and Soil Moisture Processes
Authors: Houser Paul R.
Published: July 2005

Infiltrationis the process of water entry from surface sources such as rainfall, snowmelt, or irrigation into the soil. The infiltration process is a component in the overall unsaturatedredistributionprocess that results insoil moistureavailability for use by vegetation transpiration, exfiltration (or evaporation) processes, chemical transport, and groundwater recharge. Soil moisture, in turn, controls the partitioning of subsequent precipitation into infiltration and runoff, and the partitioning of available energy between sensible and latent heat flux.

Because of the importance of soil moisture on multiple processes, its definition can be elusive; however, it is most often described as moisture in the unsaturated surface layers (first 1 to 2 m) of soil that can interact with the atmosphere through evapotranspiration and precipitation.
Hydration
Authors: Koh Carolyn Ann
Published: July 2005

Hydration
can be defined as the process by which water is added to produce a
hydrate
. The process is reversible: that is, water can be reextracted from the hydrate. Hydration to form a hydrate can occur when water (
solvent
) interacts with
solute
molecules to form a solution, which involves
hydrophobic hydration
. Hydration of nonpolar molecules and salts and hydrophobic hydration have been studied in detail over the last couple of decades using computer simulation and theory. Recently, microscopic tools such as neutron diffraction with H/D isotopic substitution have been applied to study hydration of nonpolar molecules and salts.
Isotopes
Authors: Conti Aldo
Published: July 2005

Isotopes are atoms with the same atomic number,
Z
, but different atomic weight,
A
. Different isotopes, therefore, have the same chemical but different physical properties, such as melting and boiling point. The name isotope means “at the same place” and comes from the periodic table, where different isotopes of the same element are at the same place. The scientific way of labeling isotopes reflects this. They have the symbol of the corresponding element, but followed by a hyphen and the number of nucleons (neutrons and protons) of the isotope. So, C‐12 is the normal carbon (six protons and six neutrons) and C‐14 is a heavy unstable isotope (six protons and eight neutrons).
Partitioning and Bioavailability
Authors: Philp Jim , Stainsby Fiona , Dunbar Sandra
Published: July 2005

As soon as a chemical is spilled it becomes a pollutant, but the fate of that pollutant depends to a large degree on its chemistry, which determines how it will partition to various “compartments,” or phases, of the environment. This idea is enshrined in risk‐based strategies for assessing contaminated land and water. In many cases a contaminant spill on land quickly becomes a water pollution issue, be it surface or groundwater. As many countries are heavily reliant on groundwater as a source of potable water, investigating the fate of pollutants is an essential prerequisite to any remedial action plan for contaminant cleanup.

Partitioning is governed by some fundamental properties of chemicals, but partitioning should be viewed in relation to the toxicity of the chemical in question and its degradability in the various environmental compartments. In this article, the important properties of chemicals that relate to partitioning are examined, and the theory is reinforced by example. The examples chosen are benzene, phenol, and some chlorinated phenols. All of these compounds are important industrial chemicals.

Bioavailability is a simple concept, but practically it is a complex issue that remains to be resolved. The bioavailability concept is also enshrined in the risk assessment approach to contaminated land and water. If a pollutant is present in soil or water in high concentration, but is not available to the biota, then surely it presents minimal risk. Regardless of the apparent simplicity of the concept, there is great urgency to find methods for quantifying bioavailability. Some approaches to solving this quandary are discussed.
Antimony in Aquatic Systems
Authors: Filella Montserrat
Published: July 2005

Antimony is a naturally occurring element. It belongs to group 15 of the periodic table of the elements. Antimony can exist in a variety of oxidation states (−III, 0, III, V) but it is mainly found in two oxidation states (III and V) in environmental, biological, and geochemical samples. Although antimony was already known to the ancients, it is still often overlooked, both as an element of environmental concern and as a subject for study, probably because of its lower abundance and the relative insolubility of most of its compounds. This is reflected in the poor standard of existing data on the behavior of antimony in natural waters. However, interest in the study of this element seems to be growing and an increasing number of papers on the subject are being published. A useful series of comprehensive reviews on antimony in the environment has recently been published (1, 2).
Sorption Kinetics
Authors: Karapantsios Th.D. , Loukidou M.X. , Matis K.A.
Published: July 2005

Sorption is, by definition, a general term describing the attachment of charged species (such as toxic metal ions) from a solution to a coexisting solid surface. Sorption kinetics may be controlled by several independent processes that can act in series or in parallel. These processes fall in one of the following general categories:

bulk diffusion,

external mass transfer (film diffusion),

chemical reaction (chemisorption), and

intraparticle diffusion.

Kinetic analyses allow estimating sorption rates and also lead to suitable rate expressions characteristic of possible reaction mechanisms.
Sound in Water
Authors: Marrin D. L.
Published: July 2005

As an elastic medium, water transmits sound as longitudinal waves that propagate along a path defined by the compression and subsequent relaxation of adjacent water molecules. Because water is a denser medium than air, water transmits sound waves faster and more efficiently than air. Underwater environments (e.g., oceans, lakes) are characterized by a spectrum of sound frequencies and intensities produced by geologic, meteorologic, biological, and anthropogenic sources. Naturally produced sounds vary in frequency from the high‐pitched clicks and whistles of dolphins to the very low‐pitched (often inaudible) rumblings of earthquakes and hurricanes. Man‐made underwater sounds include everything from communication signals and ship propellers to the high‐intensity audible tones produced by active sonar and acoustic thermography technologies. The behavior of oceanic sound is quite complex as a result of the manner in which it is reflected, adsorbed, scattered, and entrained by surface and bottom features, as well as by laterally extensive water layers that are stratified according to temperature and salinity.
Urban Runoff
Authors: Scholz Miklas
Published: July 2005

Urban runoff comprises the stormwater runoff from urban areas such as roads and roofs. Road and car park runoff is often more contaminated with heavy metals and organic matter than roof runoff. Runoff is usually collected in gully pots that require regular cleaning. Stormwater pipes transfer urban runoff either directly to watercourses or to sustainable urban drainage systems (also called best management practice in the United States) such as ponds or wetlands. However, urban runoff is frequently treated only by silt traps that need to be cleaned regularly. This chapter highlights the main areas in urban runoff research and contain general background information supported by case studies.
Culvert Design
Authors: Fang Xing
Published: July 2005

A culvert is a conduit placed under a road to convey surface water from one side to another. Culvert design involves both hydraulic and structural design. Culvert design involves selection of the type of culvert and size to pass the design discharge without overtopping of the road and without erosion on either end of the culvert. With consideration of the site data, a designer should establish allowable outlet velocity and maximum allowable headwater depth. The most common shapes for culverts are circular, elliptical, box, and arch. Common culvert materials include concrete (reinforced and nonreinforced), smooth and corrugated steel, aluminum, and plastic. Two types of flow controls are in culverts: inlet control and outlet control. Culvert design typically requires complex hydraulic calculations to appropriately incorporate energy losses caused by entrance, friction, and exit. Application of computer software is recommended for culvert design.
Water from Saturated River Sediment— Sand Abstraction
Authors: Hussey Stephen W.
Published: July 2005

Water is available in the saturated sediment of sand‐filled rivers. The removal of water from this sediment is known as sand abstraction. Despite the terminology, it is not the removal of sand but of water from a surface dry, seasonal river where the water is retained in the sediment, not abstraction of water from a flowing river.

Wherever there is erosion of land within the catchment area of a river, soil, sand, or gravel is carried into the river channel. The river becomes silted with sediment retained in depressions in the riverbed, behind rocks, and where the slope of the river is sufficiently low for sediment to be deposited rather than washed away.

In arid and semiarid areas, the sediment that accrues is often coarse grained, and, as the river basin drains, water is retained in the sediment in useable quantities. In spite of the intermittent flow of seasonal rivers, as the rivers drain and dry out, water is held in the sediment.
Water Hyacinth—The World's Most Problematic Weed
Authors: Williams Adrian E.
Published: July 2005

Invasive aquatic weeds have spread throughout the world's waterways as a result of anthropogenic activities. The most problematic species is water hyacinth. With the potential to double in biomass in a matter of days and the ability to migrate easily because of its free‐floating vegetative form, it can successfully colonize new habitats, form dense mats along shorelines, and displace native vegetation. In doing so, it effects ecological processes within lakes and rivers and ultimately decreases biodiversity. Moreover, for human populations living around such waterbodies, it reduces access to and quality of available drinking and irrigation water, prevents fishermen from making a living, clogs water intakes at hydroelectric dams, increases vector‐borne diseases, and generally leads to an increase in human suffering. Cultural eutrophication of lakes is also a major problem around the world, which can amplify the problem of water hyacinth. Methods to manage water hyacinth are available, which include physical, chemical, and biological forms of control. However, for the long‐term sustainability of systems, including the control of water hyacinth, only improved land, air, and watershed management can provide the solution to reducing eutrophication and the potential of water hyacinth outbreaks.
Water Turbine
Authors: Fang Xing
Published: July 2005

Water turbine is a rotary machine to convert the power of flowing water into usable electronic or mechanical power, and it is one of the cleanest producers of electric power. Water turbines are mostly used for hydropower generation, which typically requires a construction of a dam to form a reservoir. Water turbines are divided into two groups: impulse turbines and reaction turbines, according to their hydraulics action. The impulse turbine is used for high‐head hydropower installation; for example, available head for turbine is greater than 1500 ft. The specific speed of a turbine characterizes the turbine's shape and performance, and it is the main criterion to select the correct turbine type for matching a specific hydropower development. The region of a turbine runner where cavitations are most likely to occur is on the downstream side of the turbine impeller blades.
Watershed Management for Environmental Quality and Food Security
Authors: Shrivastava G. S.
Published: July 2005

An awareness of the link among watershed management, environmental quality, and food security is essential for promoting actions, which are necessary for ensuring the sustainability of life on earth. Moreover, this link is based on interactions among soil, water, vegetation, and wildlife in a watershed. Thus, it is not surprising that neglect, or destruction, of watersheds often create difficult socioeconomic circumstances or even incredible poverty. Therefore, watersheds need to be managed in a thoughtful manner, and in this regard, the following issues,
inter alia
, may be considered particularly important: preservation of biodiversity; provision of instream flow in rivers; ecological impact of ecotourism; and the impact of virtual water, embedded in global grain imports, on the pace of socioeconomic reform needed for improving watershed management. This article briefly highlights these issues and concludes that ultimately it is either science and sustainability or crisis and conflict in the sphere of watershed management.