Moritz Traube was a German chemist and universal private scholar. Traube worked on chemical, medical, pathophysiological problems, he was engaged in physical chemistry and basic chemical research. Although he was never a staff member of a university and earned his living as a wine merchant, he was able to refute theories of his leading contemporaries, including Justus von Liebig, Louis Pasteur, Felix Hoppe-Seyler and Julius Sachs, to develop significant theories of his own with solid experimental foundations; the chemistry of oxygen and its significance to the organism were the central objects of his research and provided the common thread uniting all of his scientific activity. Moritz Traube was a younger brother of the famous Berlin physician Ludwig Traube, the co-founder of the German experimental pathology. A son, Wilhelm Traube, evolved a process of purine synthesis. Hermann Traube, another son, was a mineralogist. Traube's father was the grandson of a rabbi from Krakow. Traube graduated from the Gymnasium in the provincial town of Ratibor.
His older brother Ludwig advised him to begin scientific studies at the University of Berlin. He studied experimental chemistry with Eilhard Mitscherlich and stoichiometry with Heinrich Rose, mineralogy with Christian Samuel Weiss, physics with Heinrich Wilhelm Dove, he moved to Giessen to participate in Liebig's practical-analytical course in 1844/45. He attended lectures in logic. In 1845 he returned to Berlin. In 1847 he received his doctorate with a thesis entitled "De nonnullis chromii connubiis"; the well-known botanist Nathanael Pringsheim supported him. For a while Traube worked in a Berlin dyeworks continued his studies: anatomy with Friedrich Schlemm and comparative anatomy with Johannes Müller, pathology with Rudolf Virchow and pharmacology with Eilhard Mitscherlich. For a few weeks he attended lectures in clinical disciplines such as surgery and auscultation and percussion; the extraordinarily wide spectrum of his qualifications was a basis of his universal research. When another brother, to have taken over their father's wine business died of diabetes, Traube's father ordered him home to Ratibor to help manage the business.
After agonizing for several weeks, Traube complied. But he could not abandon science. In a poorly-heated attic of his house, lacking time and money, isolated from scientific communication, he developed his extensive chemical-physiological projects, he completed numerous well-planned executed experiments, the correctness of which his contemporaries were forced to acknowledge. Traube was successful as a wine merchant. Together with his brother Ludwig he donated 500 Taler to the Ratibor Gymnasium for students' prizes, he married Bertha Moll of Lissa in 1855. The marriage produced 2 sons. To facilitate his research Traube moved to Breslau, he worked for a time in the laboratory of his friend Theodor Poleck and in the Physiological Institute of Rudolf Heidenhain. He erected his own, well equipped laboratory and employed assistants; every year he travelled to Hungary to purchase wine himself. One of his customers was Otto von Bismarck. In 1886 Traube resigned from business. From 1866 to 1890 he was a member of the "Schlesische Gesellschaft für vaterländische Kultur“.
He was elected to the board of this society in 1884. When Traube came to Berlin, he was ill from diabetes and coronary ischaemia. Here his two sons were employed at the university, he worked tirelessly in the last year of his life. His death attracted great attention, he was laid to rest in the cemetery in Berlin-Lichtenberg. On the grave, no longer preserved, stood a bronze bust by the sculptor Fritz Schaper; the gypsum model survives in the Alte Nationalgalerie in Berlin. Traube showed that sugar excretion in the urine of a diabetic patient rose after starch intake but fell after protein consumption. Additionally he demonstrated the unrestricted intestinal absorption of fats in diabetics, he thus contributed to the scientific basis for a diabetic diet. For diagnosis he proposed to measure sugar levels at specific, regular intervals: in the morning before breakfast and after meals, he thus anticipated modern principles of blood sugar measurements. Elsewhere he investigated the laxative qualities of lactose.
Traube's main work, the Theorie der Fermentwirkungen is the first comprehensive theory of fermentation to be based on experiments and elaborated from the chemical point of view. The discovery in 1837 that yeast was a living organism suggested that fermentation itself was a living process. Only a few scientists rejected this vitalistic protoplasm theory, notably Traube, he was the first to define enzymes as specific protein-like compounds and to formulate the necessity of direct molecular contact between enzyme and substrate for fermentation to occur. He classified enzymes by reaction type, much as is done today. Long before Eduard Buchner discovered non-cellular fermentation in 1897, Traube isolated an enzyme from potatoes which could turn guaiacum blue, thus demonstrating the continued efficacy of plant enzymes after they had been extracted from the cell; until biochemical history has not noted that Traube began to investigate the kinetics of reactions and demonstrated a r
Fresh water is any occurring water except seawater and brackish water. Fresh water includes water in ice sheets, ice caps, icebergs, ponds, rivers and underground water called groundwater. Fresh water is characterized by having low concentrations of dissolved salts and other total dissolved solids. Though the term excludes seawater and brackish water, it does include mineral-rich waters such as chalybeate springs. Fresh water is not the same as potable water. Much of the earth's fresh water is unsuitable for drinking without some treatment. Fresh water can become polluted by human activities or due to occurring processes, such as erosion. Water is critical to the survival of all living organisms; some organisms can thrive on salt water, but the great majority of higher plants and most mammals need fresh water to live. Fresh water can be defined as water with less than 500 parts per million of dissolved salts. Other sources give higher upper salinity limits for e.g. 1000 ppm or 3000 ppm. Fresh water habitats are classified as either lentic systems, which are the stillwaters including ponds, lakes and mires.
There is, in addition, a zone which bridges between groundwater and lotic systems, the hyporheic zone, which underlies many larger rivers and can contain more water than is seen in the open channel. It may be in direct contact with the underlying underground water; the majority of fresh water on Earth is in ice caps. The source of all fresh water is precipitation from the atmosphere, in the form of mist and snow. Fresh water falling as mist, rain or snow contains materials dissolved from the atmosphere and material from the sea and land over which the rain bearing clouds have traveled. In industrialized areas rain is acidic because of dissolved oxides of sulfur and nitrogen formed from burning of fossil fuels in cars, factories and aircraft and from the atmospheric emissions of industry. In some cases this acid rain results in pollution of rivers. In coastal areas fresh water may contain significant concentrations of salts derived from the sea if windy conditions have lifted drops of seawater into the rain-bearing clouds.
This can give rise to elevated concentrations of sodium, chloride and sulfate as well as many other compounds in smaller concentrations. In desert areas, or areas with impoverished or dusty soils, rain-bearing winds can pick up sand and dust and this can be deposited elsewhere in precipitation and causing the freshwater flow to be measurably contaminated both by insoluble solids but by the soluble components of those soils. Significant quantities of iron may be transported in this way including the well-documented transfer of iron-rich rainfall falling in Brazil derived from sand-storms in the Sahara in north Africa. Saline water in oceans and saline groundwater make up about 97% of all the water on Earth. Only 2.5–2.75% is fresh water, including 1.75–2% frozen in glaciers and snow, 0.5–0.75% as fresh groundwater and soil moisture, less than 0.01% of it as surface water in lakes and rivers. Freshwater lakes contain about 87% of this fresh surface water, including 29% in the African Great Lakes, 22% in Lake Baikal in Russia, 21% in the North American Great Lakes, 14% in other lakes.
Swamps have most of the balance with only a small amount in rivers, most notably the Amazon River. The atmosphere contains 0.04% water. In areas with no fresh water on the ground surface, fresh water derived from precipitation may, because of its lower density, overlie saline ground water in lenses or layers. Most of the world's fresh water is frozen in ice sheets. Many areas suffer from lack of distribution such as deserts. Water is a critical issue for the survival of all living organisms; some can use salt water but many organisms including the great majority of higher plants and most mammals must have access to fresh water to live. Some terrestrial mammals desert rodents, appear to survive without drinking, but they do generate water through the metabolism of cereal seeds, they have mechanisms to conserve water to the maximum degree. Fresh water creates a hypotonic environment for aquatic organisms; this is problematic for some organisms with pervious skins or with gill membranes, whose cell membranes may burst if excess water is not excreted.
Some protists accomplish this using contractile vacuoles, while freshwater fish excrete excess water via the kidney. Although most aquatic organisms have a limited ability to regulate their osmotic balance and therefore can only live within a narrow range of salinity, diadromous fish have the ability to migrate between fresh water and saline water bodies. During these migrations they undergo changes to adapt to the surroundings of the changed salinities; the eel uses the hormone prolactin, while in salmon the hormone cortisol plays a key role during this process. Many sea birds have special glands at the base of the bill; the marine iguanas on the Galápagos Islands excrete excess salt through a nasal gland and they sneeze out a salty excretion. Freshwater molluscs include freshwater snails and freshwater bivalves. Freshwater crustaceans include crayfish. Freshwater biodiversity faces many threats; the World Wide Fund for Nature's Living Planet Index noted an 83% decline in the populations of freshwater vertebrates between 1970 and 2014.
These declines continue to outpace
In business, economics or investment, market liquidity is a market's feature whereby an individual or firm can purchase or sell an asset without causing a drastic change in the asset's price. Liquidity is about how big the trade-off is between the speed of the sale and the price it can be sold for. In a liquid market, the trade-off is mild: selling will not reduce the price much. In a illiquid market, selling it will require cutting its price by some amount. Liquidity can be measured either based on trade volume relative to shares outstanding or based on the bid-ask spread or transactions costs of trading. Money, or cash, is the most liquid asset, because it can be "sold" for goods and services with no loss of value. There is no wait for a suitable buyer of the cash. There is no trade-off between value, it can be used to perform economic actions like buying, selling, or paying debt, meeting immediate wants and needs. If an asset is moderately liquid, it has moderate liquidity. In an alternative definition, liquidity can mean the amount of cash equivalents.
If a business has moderate liquidity, it has a moderate amount of liquid assets. If a business has sufficient liquidity, it has a sufficient amount of liquid assets and the ability to meet its payment obligations. An act of exchanging a less liquid asset for a more liquid asset is called liquidation. Liquidation is trading the less liquid asset for cash known as selling it. An asset's liquidity can change. For the same asset, its liquidity can change through time or between different markets, such as in different countries; the change in the asset's liquidity is just based on the market liquidity for the asset at the particular time or in the particular country, etc. The liquidity of a product can be measured as how it is bought and sold. Liquidity can be enhanced through share repurchases. Liquidity is defined formally in many accounting regimes and has in recent years been more defined. For instance, the US Federal Reserve intends to apply quantitative liquidity requirements based on Basel III liquidity rules as of fiscal 2012.
Bank directors will be required to know of, approve, major liquidity risks personally. Other rules require diversifying counterparty risk and portfolio stress testing against extreme scenarios, which tend to identify unusual market liquidity conditions and avoid investments that are vulnerable to sudden liquidity shifts. A liquid asset has some or all of the following features: It can be sold with minimal loss of value, anytime within market hours; the essential characteristic of a liquid market is that there are always ready and willing buyers and sellers. It is similar to, but distinct from, market depth, which relates to the trade-off between quantity being sold and the price it can be sold for, rather than the liquidity trade-off between speed of sale and the price it can be sold for. A market may be considered both deep and liquid if there are ready and willing buyers and sellers in large quantities. An illiquid asset is an asset, not salable due to uncertainty about its value or the lack of a market in which it is traded.
The mortgage-related assets which resulted in the subprime mortgage crisis are examples of illiquid assets, as their value was not determinable despite being secured by real property. Before the crisis, they had moderate liquidity because it was believed that their value was known. Speculators and market makers are key contributors to the liquidity of a asset. Speculators are individuals or institutions that seek to profit from anticipated increases or decreases in a particular market price. Market makers seek to profit by charging for the immediacy of execution: either implicitly by earning a bid/ask spread or explicitly by charging execution commissions. By doing this, they provide; the risk of illiquidity does not apply only to individual investments: whole portfolios are subject to market risk. Financial institutions and asset managers that oversee portfolios are subject to what is called "structural" and "contingent" liquidity risk. Structural liquidity risk, sometimes called funding liquidity risk, is the risk associated with funding asset portfolios in the normal course of business.
Contingent liquidity risk is the risk associated with finding additional funds or replacing maturing liabilities under potential, future stressed market conditions. When a central bank tries to influence the liquidity of money, this process is known as open market operations; the market liquidity of assets affects expected returns. Theory and empirical evidence suggests that investors require higher return on assets with lower market liquidity to compensate them for the higher cost of trading these assets; that is, for an asset with given cash flow, the higher its market liquidity, the higher its price and the lower is its expected return. In addition, risk-averse investors require higher expected return if the asset's market-liquidity risk is greater; this risk involves the exposure of the asset return to shocks in overall market liquidity, the exposure of the asset own liquidity to shocks in market liquidity and the effect of market return on the asset's own liquidity. Here too, the higher the liquidity risk, the higher the expected return on the asset or the lower is its price.
One example of this is a comparison of assets without a liquid secondary market. The liquidity discount is the reduced promised yield or expected a return for such assets, like the difference between newly issued U. S. Treasury bonds compared to off
Water is a transparent, tasteless and nearly colorless chemical substance, the main constituent of Earth's streams and oceans, the fluids of most living organisms. It is vital for all known forms of life though it provides no calories or organic nutrients, its chemical formula is H2O, meaning that each of its molecules contains one oxygen and two hydrogen atoms, connected by covalent bonds. Water is the name of the liquid state of H2O at standard ambient pressure, it forms precipitation in the form of rain and aerosols in the form of fog. Clouds are formed from suspended droplets of its solid state; when finely divided, crystalline ice may precipitate in the form of snow. The gaseous state of water is water vapor. Water moves continually through the water cycle of evaporation, condensation and runoff reaching the sea. Water covers 71% of the Earth's surface in seas and oceans. Small portions of water occur as groundwater, in the glaciers and the ice caps of Antarctica and Greenland, in the air as vapor and precipitation.
Water plays an important role in the world economy. 70% of the freshwater used by humans goes to agriculture. Fishing in salt and fresh water bodies is a major source of food for many parts of the world. Much of long-distance trade of commodities and manufactured products is transported by boats through seas, rivers and canals. Large quantities of water and steam are used for cooling and heating, in industry and homes. Water is an excellent solvent for a wide variety of chemical substances. Water is central to many sports and other forms of entertainment, such as swimming, pleasure boating, boat racing, sport fishing, diving; the word water comes from Old English wæter, from Proto-Germanic *watar, from Proto-Indo-European *wod-or, suffixed form of root *wed-. Cognate, through the Indo-European root, with Greek ύδωρ, Russian вода́, Irish uisce, Albanian ujë; the identification of water as a substance Water is a polar inorganic compound, at room temperature a tasteless and odorless liquid, nearly colorless with a hint of blue.
This simplest hydrogen chalcogenide is by far the most studied chemical compound and is described as the "universal solvent" for its ability to dissolve many substances. This allows it to be the "solvent of life", it is the only common substance to exist as a solid and gas in normal terrestrial conditions. Water is a liquid at the pressures that are most adequate for life. At a standard pressure of 1 atm, water is a liquid between 0 and 100 °C. Increasing the pressure lowers the melting point, about −5 °C at 600 atm and −22 °C at 2100 atm; this effect is relevant, for example, to ice skating, to the buried lakes of Antarctica, to the movement of glaciers. Increasing the pressure has a more dramatic effect on the boiling point, about 374 °C at 220 atm; this effect is important in, among other things, deep-sea hydrothermal vents and geysers, pressure cooking, steam engine design. At the top of Mount Everest, where the atmospheric pressure is about 0.34 atm, water boils at 68 °C. At low pressures, water cannot exist in the liquid state and passes directly from solid to gas by sublimation—a phenomenon exploited in the freeze drying of food.
At high pressures, the liquid and gas states are no longer distinguishable, a state called supercritical steam. Water differs from most liquids in that it becomes less dense as it freezes; the maximum density of water in its liquid form is 1,000 kg/m3. The density of ice is 917 kg/m3. Thus, water expands 9% in volume as it freezes, which accounts for the fact that ice floats on liquid water; the details of the exact chemical nature of liquid water are not well understood. Pure water is described as tasteless and odorless, although humans have specific sensors that can feel the presence of water in their mouths, frogs are known to be able to smell it. However, water from ordinary sources has many dissolved substances, that may give it varying tastes and odors. Humans and other animals have developed senses that enable them to evaluate the potability of water by avoiding water, too salty or putrid; the apparent color of natural bodies of water is determined more by dissolved and suspended solids, or by reflection of the sky, than by water itself.
Light in the visible electromagnetic spectrum can traverse a couple meters of pure water without significant absorption, so that it looks transparent and colorless. Thus aquatic plants and other photosynthetic organisms can live in water up to hundreds of meters deep, because sunlight can reach them. Water vapour is invisible as a gas. Through a thickness of 10 meters or more, the intrinsic color of water is visibly turquoise, as its absorption spectrum has
The cell is the basic structural and biological unit of all known living organisms. A cell is the smallest unit of life. Cells are called the "building blocks of life"; the study of cells is called cellular biology. Cells consist of cytoplasm enclosed within a membrane, which contains many biomolecules such as proteins and nucleic acids. Organisms can be classified as multicellular; the number of cells in plants and animals varies from species to species, it has been estimated that humans contain somewhere around 40 trillion cells. Most plant and animal cells are visible only under a microscope, with dimensions between 1 and 100 micrometres. Cells were discovered by Robert Hooke in 1665, who named them for their resemblance to cells inhabited by Christian monks in a monastery. Cell theory, first developed in 1839 by Matthias Jakob Schleiden and Theodor Schwann, states that all organisms are composed of one or more cells, that cells are the fundamental unit of structure and function in all living organisms, that all cells come from pre-existing cells.
Cells emerged on Earth at least 3.5 billion years ago. Cells are of two types: eukaryotic, which contain a nucleus, prokaryotic, which do not. Prokaryotes are single-celled organisms, while eukaryotes can be either single-celled or multicellular. Prokaryotes include two of the three domains of life. Prokaryotic cells were the first form of life on Earth, characterised by having vital biological processes including cell signaling, they are simpler and smaller than eukaryotic cells, lack membrane-bound organelles such as a nucleus. The DNA of a prokaryotic cell consists of a single chromosome, in direct contact with the cytoplasm; the nuclear region in the cytoplasm is called the nucleoid. Most prokaryotes are the smallest of all organisms ranging from 0.5 to 2.0 µm in diameter. A prokaryotic cell has three architectural regions: Enclosing the cell is the cell envelope – consisting of a plasma membrane covered by a cell wall which, for some bacteria, may be further covered by a third layer called a capsule.
Though most prokaryotes have both a cell membrane and a cell wall, there are exceptions such as Mycoplasma and Thermoplasma which only possess the cell membrane layer. The envelope gives rigidity to the cell and separates the interior of the cell from its environment, serving as a protective filter; the cell wall consists of peptidoglycan in bacteria, acts as an additional barrier against exterior forces. It prevents the cell from expanding and bursting from osmotic pressure due to a hypotonic environment; some eukaryotic cells have a cell wall. Inside the cell is the cytoplasmic region that contains the genome and various sorts of inclusions; the genetic material is found in the cytoplasm. Prokaryotes can carry extrachromosomal DNA elements called plasmids, which are circular. Linear bacterial plasmids have been identified in several species of spirochete bacteria, including members of the genus Borrelia notably Borrelia burgdorferi, which causes Lyme disease. Though not forming a nucleus, the DNA is condensed in a nucleoid.
Plasmids encode additional genes, such as antibiotic resistance genes. On the outside and pili project from the cell's surface; these are structures made of proteins that facilitate communication between cells. Plants, fungi, slime moulds and algae are all eukaryotic; these cells are about fifteen times wider than a typical prokaryote and can be as much as a thousand times greater in volume. The main distinguishing feature of eukaryotes as compared to prokaryotes is compartmentalization: the presence of membrane-bound organelles in which specific activities take place. Most important among these is a cell nucleus, an organelle that houses the cell's DNA; this nucleus gives the eukaryote its name, which means "true kernel". Other differences include: The plasma membrane resembles that of prokaryotes in function, with minor differences in the setup. Cell walls may not be present; the eukaryotic DNA is organized in one or more linear molecules, called chromosomes, which are associated with histone proteins.
All chromosomal DNA is stored in the cell nucleus, separated from the cytoplasm by a membrane. Some eukaryotic organelles such as mitochondria contain some DNA. Many eukaryotic cells are ciliated with primary cilia. Primary cilia play important roles in chemosensation and thermosensation. Cilia may thus be "viewed as a sensory cellular antennae that coordinates a large number of cellular signaling pathways, sometimes coupling the signaling to ciliary motility or alternatively to cell division and differentiation." Motile eukaryotes can move using motile flagella. Motile cells are absent in flowering plants. Eukaryotic flagella are more complex than those of prokaryotes. All cells, whether prokaryotic or eukaryotic, have a membrane that envelops the cell, regulates what moves in and out, maintains the electric potential of the cell. Inside the membrane, the cytoplasm takes up most of the cell's volume. All cells possess DNA, the hereditary material of genes, RNA, containing the information necessary to build various proteins such as enzymes, the cell's primary machinery.
There are other kinds of biomolecules in cells. This article lists these primary cellular components briefly
Plasmolysis is the process in which cells lose water in a hypertonic solution. The reverse process, can occur if the cell is in a hypotonic solution resulting in a lower external osmotic pressure and a net flow of water into the cell. Through observation of plasmolysis and deplasmolysis, it is possible to determine the tonicity of the cell's environment as well as the rate solute molecules cross the cellular membrane. A plant cell in hypotonic solution will absorb water by endosmosis, so that the increased volume of water in the cell will increase pressure, making the protoplasm push against the cell wall, a condition known as turgor. Turgor makes plant cells push against each other in the same way and is the main line method of support in non-woody plant tissue. Plant cell walls resist further water entry after a certain point, known as full turgor, which stops plant cells from bursting as animal cells do in the same conditions; this is the reason that plants stand upright. Without the stiffness of the plant cells the plant would fall under its own weight.
Turgor pressure allows plants to stay firm and erect, plants without turgor pressure wilt. A cell will begin to decline in turgor pressure only when there is no air spaces surrounding it and leads to a greater osmotic pressure than that of the cell. Vacuoles play a role in turgor pressure when water leaves the cell due to hyperosmotic solutions containing solutes such as mannitol and sucrose. If a plant cell is placed in a hypertonic solution, the plant cell loses water and hence turgor pressure by plasmolysis: pressure decreases to the point where the protoplasm of the cell peels away from the cell wall, leaving gaps between the cell wall and the membrane and making the plant cell shrink and crumple. A continued decrease in pressure leads to cytorrhysis – the complete collapse of the cell wall. Plants with cells in this condition wilt. After plasmolysis the gap between the cell wall and the cell membrane in a plant cell is filled with hypertonic solution; this is because as the solution surrounding the cell is hypertonic, exosmosis takes place and the space between the cell wall and cytoplasm is filled with solutes, as most of the water drains away and hence the concentration inside the cell becomes more hypertonic.
There are some mechanisms in plants to prevent excess water loss in the same way as excess water gain. Plasmolysis can be reversed. Stomata help keep water in the plant. Wax keeps water in the plant; the equivalent process in animal cells is called crenation. The liquid content of the cell leaks out due to exosmosis; the cell collapses, the cell membrane pulls away from the cell wall. Most animal cells consist of only a phospholipid bilayer and not a cell wall, therefore shrinking up under such conditions. Plasmolysis only occurs in extreme conditions and happens in nature, it is induced in the laboratory by immersing cells in strong saline or sugar solutions to cause exosmosis using Elodea plants or onion epidermal cells, which have colored cell sap so that the process is visible. Methylene blue can be used to stain plant cells. Plasmolysis is known as shrinking of cell membrane in hypertonic solution and great pressure. Plasmolysis can be of either concave plasmolysis or convex plasmolysis. Convex plasmolysis is always irreversible while concave plasmolysis is reversible.
During concave plasmolysis, the plasma membrane and the enclosed protoplast shrinks from the cell wall due to half-spherical, inwarding curving pockets forming between the plasma membrane and the cell wall. During convex plasmolysis, the plasma membrane and the enclosed protoplast shrinks from the cell wall, with the plasma membrane's ends in a symmetrically, spherically curved pattern. Crenation Cytolysis, where the cell bursts rather than shrinks. Osmosis Pictures of plasmolysis in Elodea and onion skin. Archived April 16, 2008, at the Wayback Machine Wilting and plasymolysis. Archived October 14, 2007, at the Wayback Machine
Water purification is the process of removing undesirable chemicals, biological contaminants, suspended solids, gases from water. The goal is to produce water fit for specific purposes. Most water is purified and disinfected for human consumption, but water purification may be carried out for a variety of other purposes, including medical, pharmacological and industrial applications; the methods used include physical processes such as filtration and distillation. Water purification may reduce the concentration of particulate matter including suspended particles, bacteria, algae and fungi as well as reduce the concentration of a range of dissolved and particulate matter; the standards for drinking water quality are set by governments or by international standards. These standards include minimum and maximum concentrations of contaminants, depending on the intended use of the water. Visual inspection can not determine. Simple procedures such as boiling or the use of a household activated carbon filter are not sufficient for treating all possible contaminants that may be present in water from an unknown source.
Natural spring water – considered safe for all practical purposes in the 19th century – must now be tested before determining what kind of treatment, if any, is needed. Chemical and microbiological analysis, while expensive, are the only way to obtain the information necessary for deciding on the appropriate method of purification. According to a 2007 World Health Organization report, 1.1 billion people lack access to an improved drinking water supply. The WHO estimates that 94% of these diarrheal disease cases are preventable through modifications to the environment, including access to safe water. Simple techniques for treating water at home, such as chlorination and solar disinfection, for storing it in safe containers could save a huge number of lives each year. Reducing deaths from waterborne diseases is a major public health goal in developing countries. Groundwater: The water emerging from some deep ground water may have fallen as rain many tens, hundreds, or thousands of years ago. Soil and rock layers filter the ground water to a high degree of clarity and it does not require additional treatment besides adding chlorine or chloramines as secondary disinfectants.
Such water may be extracted from boreholes or wells. Deep ground water is of high bacteriological quality, but the water may be rich in dissolved solids carbonates and sulfates of calcium and magnesium. Depending on the strata through which the water has flowed, other ions may be present including chloride, bicarbonate. There may be a requirement to reduce the iron or manganese content of this water to make it acceptable for drinking and laundry use. Primary disinfection may be required. Where groundwater recharge is practiced, the groundwater may require additional treatment depending on applicable state and federal regulations. Upland lakes and reservoirs: Typically located in the headwaters of river systems, upland reservoirs are sited above any human habitation and may be surrounded by a protective zone to restrict the opportunities for contamination. Bacteria and pathogen levels are low, but some bacteria, protozoa or algae will be present. Where uplands are forested or peaty, humic acids can colour the water.
Many upland sources have low pH. Rivers and low land reservoirs: Low land surface waters will have a significant bacterial load and may contain algae, suspended solids and a variety of dissolved constituents. Atmospheric water generation is a new technology that can provide high quality drinking water by extracting water from the air by cooling the air and thus condensing water vapor. Rainwater harvesting or fog collection which collect water from the atmosphere can be used in areas with significant dry seasons and in areas which experience fog when there is little rain. Desalination of seawater by distillation or reverse osmosis. Surface Water: Freshwater bodies that are open to the atmosphere and are not designated as groundwater are termed surface waters; the goals of the treatment are to remove unwanted constituents in the water and to make it safe to drink or fit for a specific purpose in industry or medical applications. Varied techniques are available to remove contaminants like fine solids, micro-organisms and some dissolved inorganic and organic materials, or environmental persistent pharmaceutical pollutants.
The choice of method will depend on the quality of the water being treated, the cost of the treatment process and the quality standards expected of the processed water. The processes below are the ones used in water purification plants; some or most may not be used depending on the scale of the quality of the raw water. Pumping and containment – The majority of water must be pumped from its source or directed into pipes or holding tanks. To avoid adding contaminants to the water, this physical infrastructure must be made from appr