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Drinking Water Quality Standards
Drinking water quality standards describes the quality parameters set for drinking water. Water may contain many harmful constituents, yet there are no universally recognized and accepted international standards for drinking water. Even where standards do exist, the permitted concentration of individual constituents may vary by up to ten times from one set of standards to another. Many countries specify standards to be applied in their own country. In Europe, this includes the European Drinking Water Directive and in the United States, the United States Environmental Protection Agency (EPA) establishes standards as required by the Safe Drinking Water Act. China adopted its own drinking water standard GB3838-2002 (Type II) enacted by Ministry of Environmental Protection in 2002. For countries without a legislative or administrative framework for such standards, the World Health Organization publishes guidelines on the standards that should be achieved. Where drinking water qua ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parameter
A parameter (), generally, is any characteristic that can help in defining or classifying a particular system (meaning an event, project, object, situation, etc.). That is, a parameter is an element of a system that is useful, or critical, when identifying the system, or when evaluating its performance, status, condition, etc. ''Parameter'' has more specific meanings within various disciplines, including mathematics, computer programming, engineering, statistics, logic, linguistics, and electronic musical composition. In addition to its technical uses, there are also extended uses, especially in non-scientific contexts, where it is used to mean defining characteristics or boundaries, as in the phrases 'test parameters' or 'game play parameters'. Modelization When a system theory, system is modeled by equations, the values that describe the system are called ''parameters''. For example, in mechanics, the masses, the dimensions and shapes (for solid bodies), the densities and t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Statistics
Statistics (from German language, German: ', "description of a State (polity), state, a country") is the discipline that concerns the collection, organization, analysis, interpretation, and presentation of data. In applying statistics to a scientific, industrial, or social problem, it is conventional to begin with a statistical population or a statistical model to be studied. Populations can be diverse groups of people or objects such as "all people living in a country" or "every atom composing a crystal". Statistics deals with every aspect of data, including the planning of data collection in terms of the design of statistical survey, surveys and experimental design, experiments. When census data (comprising every member of the target population) cannot be collected, statisticians collect data by developing specific experiment designs and survey sample (statistics), samples. Representative sampling assures that inferences and conclusions can reasonably extend from the sample ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chromium
Chromium is a chemical element; it has Symbol (chemistry), symbol Cr and atomic number 24. It is the first element in Group 6 element, group 6. It is a steely-grey, Luster (mineralogy), lustrous, hard, and brittle transition metal. Chromium is valued for its high corrosion resistance and hardness. A major development in steel production was the discovery that steel could be made highly resistant to corrosion and discoloration by adding metallic chromium to form stainless steel. Stainless steel and chrome plating (electroplating with chromium) together comprise 85% of the commercial use. Chromium is also greatly valued as a metal that is able to be highly polishing, polished while resisting tarnishing. Polished chromium reflects almost 70% of the visible spectrum, and almost 90% of infrared, infrared light. The name of the element is derived from the Ancient Greek, Greek word χρῶμα, ''chrōma'', meaning color, because many chromium compounds are intensely colored. Indust ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cadmium
Cadmium is a chemical element; it has chemical symbol, symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12 element, group 12, zinc and mercury (element), mercury. Like zinc, it demonstrates oxidation state +2 in most of its compounds, and like mercury, it has a lower melting point than the transition metals in group 3 element, groups 3 through group 11 element, 11. Cadmium and its Congener (chemistry), congeners in group 12 are often not considered transition metals, in that they do not have partly filled ''d'' or ''f'' electron shells in the elemental or common oxidation states. The average concentration of cadmium in Earth's crust is between 0.1 and 0.5 parts per million (ppm). It was discovered in 1817 simultaneously by Friedrich Stromeyer, Stromeyer and Karl Samuel Leberecht Hermann, Hermann, both in Germany, as an impurity in zinc carbonate. Cadmium occurs as a minor component in most zinc ores and i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bromate
The bromate anion, , is a bromine-based oxoanion. A bromate is a chemical compound that contains this ion. Examples of bromates include sodium bromate () and potassium bromate (). Bromates are formed many different ways in municipal drinking water. The most common is the reaction of ozone and bromide: : Br + → BrO Electrochemical processes, such as electrolysis of brine without a membrane operating to form hypochlorite, will also produce bromate when bromide ion is present in the brine solution. Photoactivation (sunlight exposure) will encourage liquid or gaseous bromine to generate bromate in bromide-containing water. In laboratories bromates can be synthesized by dissolving in a concentrated solution of potassium hydroxide (KOH). The following reactions will take place (via the intermediate creation of hypobromite): : + 2 OH− → Br + BrO + :3 BrO → BrO + 2 Br Human health issues Bromate in drinking water is toxic because it is a suspected human carcinogen. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Boron
Boron is a chemical element; it has symbol B and atomic number 5. In its crystalline form it is a brittle, dark, lustrous metalloid; in its amorphous form it is a brown powder. As the lightest element of the boron group it has three valence electrons for forming covalent bonds, resulting in many compounds such as boric acid, the mineral sodium borate, and the ultra-hard crystals of boron carbide and boron nitride. Boron is synthesized entirely by cosmic ray spallation and supernovas and not by stellar nucleosynthesis, so it is a low-abundance element in the Solar System and in the Earth's crust. It constitutes about 0.001 percent by weight of Earth's crust. It is concentrated on Earth by the water-solubility of its more common naturally occurring compounds, the borate minerals. These are mined industrially as evaporites, such as borax and kernite. The largest known deposits are in Turkey, the largest producer of boron minerals. Elemental boron is found in smal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Benzo(a)pyrene
Benzo 'a''yrene (B''a''P or B ) is a polycyclic aromatic hydrocarbon and the result of incomplete combustion of organic matter at temperatures between and . The ubiquitous compound can be found in coal tar, tobacco smoke and many foods, especially grilled meats. The substance with the formula C20H12 is one of the benzopyrenes, formed by a benzene ring fused to pyrene. Its diol epoxide metabolites, more commonly known as BPDE, react with and bind to DNA, resulting in mutations and eventually cancer. It is listed as a Group 1 carcinogen by the IARC. In the 18th century a scrotal cancer of chimney sweepers, the chimney sweeps' carcinoma, was already known to be connected to soot. Description Benzo 'a''yrene (B''a''P) is a polycyclic aromatic hydrocarbon found in coal tar with the formula C20H12. The compound is one of the benzopyrenes, formed by a benzene ring fused to pyrene, and is the result of incomplete combustion at temperatures between and . Sources The ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Benzene
Benzene is an Organic compound, organic chemical compound with the Chemical formula#Molecular formula, molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar hexagonal Ring (chemistry), ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms, benzene is classed as a hydrocarbon. Benzene is a natural constituent of petroleum and is one of the elementary petrochemicals. Due to the cyclic continuous pi bonds between the carbon atoms, benzene is classed as an aromatic hydrocarbon. Benzene is a colorless and highly Combustibility and flammability, flammable liquid with a sweet smell, and is partially responsible for the aroma of gasoline. It is used primarily as a Precursor (chemistry), precursor to the manufacture of chemicals with more complex structures, such as ethylbenzene and cumene, of which billions of kilograms are produced annually. Although benzene is a major Chemical industry, industrial che ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arsenic
Arsenic is a chemical element; it has Symbol (chemistry), symbol As and atomic number 33. It is a metalloid and one of the pnictogens, and therefore shares many properties with its group 15 neighbors phosphorus and antimony. Arsenic is notoriously toxic. It occurs naturally in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. It has various Allotropes of arsenic, allotropes, but only the grey form, which has a metallic appearance, is important to industry. The primary use of arsenic is in alloys of lead (for example, in car batteries and ammunition). Arsenic is also a common n-type dopant in semiconductor electronic devices, and a component of the III–V compound semiconductor gallium arsenide. Arsenic and its compounds, especially the trioxide, are used in the production of pesticides, treated wood products, herbicides, and insecticides. These applications are declining with the increasing recognition of the persistent tox ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antimony
Antimony is a chemical element; it has chemical symbol, symbol Sb () and atomic number 51. A lustrous grey metal or metalloid, it is found in nature mainly as the sulfide mineral stibnite (). Antimony compounds have been known since ancient times and were powdered for use as medicine and cosmetics, often known by the Arabic name Kohl (cosmetics), kohl. The earliest known description of this metalloid in the West was written in 1540 by Vannoccio Biringuccio. China is the largest producer of antimony and its compounds, with most production coming from the Xikuangshan Mine in Hunan. The industrial methods for refining antimony from stibnite are Roasting (metallurgy), roasting followed by carbothermic reaction, reduction with carbon, or direct reduction of stibnite with iron. The most common applications for metallic antimony are in alloys with lead and tin, which have improved properties for solders, Bullet, bullets, and plain bearings. It improves the rigidity of lead-alloy pla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acrylamide
Acrylamide (or acrylic amide) is an organic compound with the chemical formula CH2=CHC(O)NH2. It is a white odorless solid, soluble in water and several organic solvents. From the chemistry perspective, acrylamide is a vinyl-substituted primary amide (CONH2). It is produced industrially mainly as a precursor to polyacrylamides, which find many uses as water-soluble thickeners and flocculation agents. Acrylamide forms in burnt areas of food, particularly starchy foods like potatoes, when cooked with high heat, above . Despite health scares following this discovery in 2002, and its classification as a probable carcinogen, acrylamide from diet is thought unlikely to cause cancer in humans; Cancer Research UK categorized the idea that eating burnt food causes cancer as a "myth". Production Acrylamide can be prepared by the hydration of acrylonitrile, which is catalyzed enzymatically: :CH2=CHCN + H2O → CH2=CHC(O)NH2 This reaction also is catalyzed by sulfuric acid as wel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nitrogen
Nitrogen is a chemical element; it has Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a Nonmetal (chemistry), nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the Pnictogen, pnictogens. It is a common element in the universe, estimated at Abundance of the chemical elements, seventh in total abundance in the Milky Way and the Solar System. At standard temperature and pressure, two atoms of the element chemical bond, bond to form N2, a colourless and odourless diatomic molecule, diatomic gas. N2 forms about 78% of Atmosphere of Earth, Earth's atmosphere, making it the most abundant chemical species in air. Because of the volatility of nitrogen compounds, nitrogen is relatively rare in the solid parts of the Earth. It was first discovered and isolated by Scottish physician Daniel Rutherford in 1772 and independently by Carl Wilhelm Scheele and Henry Cavendish at about the same time. The name was suggested by French chemist ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
