1.
Molecule
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A molecule is an electrically neutral group of two or more atoms held together by chemical bonds. Molecules are distinguished from ions by their lack of electrical charge, however, in quantum physics, organic chemistry, and biochemistry, the term molecule is often used less strictly, also being applied to polyatomic ions. In the kinetic theory of gases, the molecule is often used for any gaseous particle regardless of its composition. According to this definition, noble gas atoms are considered molecules as they are in fact monoatomic molecules. A molecule may be homonuclear, that is, it consists of atoms of one element, as with oxygen, or it may be heteronuclear. Atoms and complexes connected by non-covalent interactions, such as hydrogen bonds or ionic bonds, are not considered single molecules. Molecules as components of matter are common in organic substances and they also make up most of the oceans and atmosphere. Also, no typical molecule can be defined for ionic crystals and covalent crystals, the theme of repeated unit-cellular-structure also holds for most condensed phases with metallic bonding, which means that solid metals are also not made of molecules. In glasses, atoms may also be together by chemical bonds with no presence of any definable molecule. The science of molecules is called molecular chemistry or molecular physics, in practice, however, this distinction is vague. In molecular sciences, a molecule consists of a system composed of two or more atoms. Polyatomic ions may sometimes be thought of as electrically charged molecules. The term unstable molecule is used for very reactive species, i. e, according to Merriam-Webster and the Online Etymology Dictionary, the word molecule derives from the Latin moles or small unit of mass. Molecule – extremely minute particle, from French molécule, from New Latin molecula, diminutive of Latin moles mass, a vague meaning at first, the vogue for the word can be traced to the philosophy of Descartes. The definition of the molecule has evolved as knowledge of the structure of molecules has increased, earlier definitions were less precise, defining molecules as the smallest particles of pure chemical substances that still retain their composition and chemical properties. Molecules are held together by covalent bonding or ionic bonding. Several types of non-metal elements exist only as molecules in the environment, for example, hydrogen only exists as hydrogen molecule. A molecule of a compound is made out of two or more elements, a covalent bond is a chemical bond that involves the sharing of electron pairs between atoms
2.
Ion
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An ion is an atom or a molecule in which the total number of electrons is not equal to the total number of protons, giving the atom or molecule a net positive or negative electrical charge. Ions can be created, by chemical or physical means. In chemical terms, if an atom loses one or more electrons. If an atom gains electrons, it has a net charge and is known as an anion. Ions consisting of only a single atom are atomic or monatomic ions, because of their electric charges, cations and anions attract each other and readily form ionic compounds, such as salts. In the case of ionization of a medium, such as a gas, which are known as ion pairs are created by ion impact, and each pair consists of a free electron. The word ion comes from the Greek word ἰόν, ion, going and this term was introduced by English physicist and chemist Michael Faraday in 1834 for the then-unknown species that goes from one electrode to the other through an aqueous medium. Faraday also introduced the words anion for a charged ion. In Faradays nomenclature, cations were named because they were attracted to the cathode in a galvanic device, arrhenius explanation was that in forming a solution, the salt dissociates into Faradays ions. Arrhenius proposed that ions formed even in the absence of an electric current, ions in their gas-like state are highly reactive, and do not occur in large amounts on Earth, except in flames, lightning, electrical sparks, and other plasmas. These gas-like ions rapidly interact with ions of charge to give neutral molecules or ionic salts. These stabilized species are commonly found in the environment at low temperatures. A common example is the present in seawater, which are derived from the dissolved salts. Electrons, due to their mass and thus larger space-filling properties as matter waves, determine the size of atoms. Thus, anions are larger than the parent molecule or atom, as the excess electron repel each other, as such, in general, cations are smaller than the corresponding parent atom or molecule due to the smaller size of its electron cloud. One particular cation contains no electrons, and thus consists of a single proton - very much smaller than the parent hydrogen atom. Since the electric charge on a proton is equal in magnitude to the charge on an electron, an anion, from the Greek word ἄνω, meaning up, is an ion with more electrons than protons, giving it a net negative charge. A cation, from the Greek word κατά, meaning down, is an ion with fewer electrons than protons, there are additional names used for ions with multiple charges
3.
Biological membrane
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A biological membrane or biomembrane is an enclosing or separating membrane that acts as a selectively permeable barrier within living things. Bulk lipid in membrane provides a matrix for proteins to rotate. The cellular membranes should not be confused with isolating tissues formed by layers of cells, such as mucous membranes, the lipid bilayer consists of two layers- an outer leaflet and an inner leaflet. The components of bilayers are distributed unequally between the two surfaces to create asymmetry between the outer and inner surfaces and this asymmetric organization is important for cell functions such as cell signaling. The asymmetry of the biological membrane reflects the different functions of the two leaflets of the membrane, as seen in the fluid membrane model of the phospholipid bilayer, the outer leaflet and inner leaflet of the membrane are asymmetrical in their composition. Certain proteins and lipids rest only on one surface of the membrane, in eucaryotic cells, new phospholipids are manufactured by enzymes bound to the part of the endoplasmic reticulum membrane that faces the cytosol. These enzymes, which use free fatty acids as substrates, deposit all newly made phospholipids into the half of the bilayer. To enable the membrane as a whole to grow evenly, half of the new phospholipid molecules then have to be transferred to the opposite monolayer and this transfer is catalyzed by enzymes called flippases. In the plasma membrane, flippases transfer specific phospholipids selectively, so different types become concentrated in each monolayer. Using selective flippases is not the way to produce asymmetry in lipid bilayers. In particular, a different mechanism operates for glycolipids—the lipids that show the most striking, the biological membrane is made up of lipids with hydrophobic tails and hydrophilic heads. The hydrophobic tails are hydrocarbon tails whose length and saturation is important in characterizing the cell, lipid rafts occur when lipid species and proteins aggregate in domains in the membrane. These help organize membrane components into localized areas that are involved in specific processes, red blood cells, or erythrocytes, have a unique lipid composition. The bilayer of red cells is composed of cholesterol and phospholipids in equal proportions by weight. Erythrocyte membrane plays a role in blood clotting. In the bilayer of red cells is phosphatidylserine. This is usually in the side of the membrane. However, it is flipped to the membrane to be used during blood clotting
4.
Cell membrane
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The cell membrane is a biological membrane that separates the interior of all cells from the outside environment. The cell membrane is permeable to ions and organic molecules and controls the movement of substances in. The basic function of the membrane is to protect the cell from its surroundings. It consists of the bilayer with embedded proteins. Cell membranes can be artificially reassembled, Some authors that did not believe that there was a functional permeable boundary at the surface of the cell preferred to use the term plasmalemma to the extern region of the cell. The cell membrane surrounds the cytoplasm of living cells, physically separating the components from the extracellular environment. The cell membrane also plays a role in anchoring the cytoskeleton to provide shape to the cell, fungi, bacteria, most archaea, and plants also have a cell wall, which provides a mechanical support to the cell and precludes the passage of larger molecules. The cell membrane is permeable and able to regulate what enters and exits the cell. The movement of substances across the membrane can be passive, occurring without the input of cellular energy, or active. The membrane also maintains the cell potential, the cell membrane thus works as a selective filter that allows only certain things to come inside or go outside the cell. The cell employs a number of mechanisms that involve biological membranes,1. Passive osmosis and diffusion, Some substances such as carbon dioxide and oxygen, can move across the membrane by diffusion. Because the membrane acts as a barrier for certain molecules and ions, such a concentration gradient across a semipermeable membrane sets up an osmotic flow for the water. Transmembrane protein channels and transporters, Nutrients, such as sugars or amino acids, must enter the cell, such molecules diffuse passively through protein channels such as aquaporins in facilitated diffusion or are pumped across the membrane by transmembrane transporters. Protein channel proteins, also called permeases, are quite specific, recognizing and transporting only a limited food group of chemical substances. Endocytosis, Endocytosis is the process in which cells absorb molecules by engulfing them, the plasma membrane creates a small deformation inward, called an invagination, in which the substance to be transported is captured. The deformation then pinches off from the membrane on the inside of the cell, Endocytosis is a pathway for internalizing solid particles, small molecules and ions, and macromolecules. Endocytosis requires energy and is thus a form of active transport and this is the process of exocytosis
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Nuclear membrane
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A nuclear membrane, also known as the nucleolemma or karyotheca, is the phospho lipid bilayer membrane which surrounds the genetic material and nucleolus in eukaryotic cells. The nuclear membrane consists of two lipid bilayers—the inner nuclear membrane, and the nuclear membrane. The space between the membranes is called the space, a region contiguous with the lumen of the endoplasmic reticulum. It is usually about 20–40 nm wide, the nuclear membrane also has many small holes called nuclear pores that allow material to move in and out of the nucleus. The outer nuclear membrane also shares a border with the endoplasmic reticulum. While it is linked, the outer nuclear membrane contains proteins found in far higher concentrations than the endoplasmic reticulum. All 4 Nesprin proteins present in mammals are expressed in the nuclear membrane. Nesprin proteins connect cytoskeletal filaments to the nucleoskeleton, nesprin-mediated connections to the cytoskeleton contribute to nuclear positioning and to the cell’s mechanosensory function. Nesprin-3 and-4 may play a role in unloading cargo, Nesprin-3 proteins bind plectin. Nesprin-4 proteins bind the end directed motor kinesin-1. The outer nuclear membrane is also involved in development, as it fuses with the nuclear membrane to form nuclear pores. It is connected to the membrane by nuclear pores which penetrate the membranes. While the two membranes and the reticulum are linked, proteins embedded in the membranes tend to stay put rather than dispersing across the continuum. The nuclear membrane is punctured by thousands of nuclear pore complexes—large hollow proteins about 100 nm across and they link the inner and outer nuclear membranes. During the G2 phase of interphase, the membrane increases its surface area. In lower eukaryotes, such as yeast, which undergo closed mitosis, the spindle fibers either form within the membrane, or penetrate it without tearing it apart. In higher eukaryotes, the membrane must break down during the prometaphase state of mitosis to allow the mitotic spindle fibers to access the chromosomes inside. The breakdown and reformation processes are not well understood, in mammals, the nuclear membrane can break down within minutes, following a set of steps during the early stages of Mitosis
6.
Synthetic membrane
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An artificial membrane, or synthetic membrane, is a synthetically created membrane which is usually intended for separation purposes in laboratory or in industry. Synthetic membranes have been used for small and large-scale industrial processes since the middle of twentieth century. A wide variety of membranes is known. They can be produced from materials such as polymers and liquids. The most of commercially utilized synthetic membranes in separation industry are made of polymeric structures and they can be classified based on their surface chemistry, bulk structure, morphology, and production method. The chemical and physical properties of synthetic membranes and separated particles as well as a choice of driving force define a particular membrane separation process, the most commonly used driving forces of a membrane process in industry are pressure and concentration gradients. The respective membrane process is known as filtration. Synthetic membranes utilized in a process can be of different geometry. They can also be categorized based on their application and separation regime, synthetic membrane can be fabricated from a large number of different materials. It can be made from organic or inorganic materials including solids such as metal or ceramic, homogeneous films, heterogeneous solids, ceramic membranes are produced from inorganic materials such as aluminium oxides, silicon carbide, and zirconium oxide. Ceramic membranes are very resistant to the action of aggressive media and they are very stable chemically, thermally, and mechanically, and biologically inert. Even though ceramic membranes have a weight and substantial production costs. Ceramic membranes are made as monolithic shapes of tubular capillaries. Liquid membranes refer to synthetic membranes made of non-rigid materials, several types of liquid membranes can be encountered in industry, emulsion liquid membranes, immobilized liquid membranes, molten salts, and hollow-fiber contained liquid membranes. Liquid membranes have been studied but thus far have limited commercial applications. Maintaining adequate long-term stability is the problem, due to the tendency of membrane liquids to evaporate or dissolve in the phases in contact with them, polymeric membranes lead the membrane separation industry market because they are very competitive in performance and economics. Many polymers are available, but the choice of membrane polymer is not a trivial task, a polymer has to have appropriate characteristics for the intended application. The polymer sometimes has to offer a low binding affinity for separated molecules and it has to be compatible with chosen membrane fabrication technology
7.
Laboratory
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A laboratory is a facility that provides controlled conditions in which scientific or technological research, experiments, and measurement may be performed. Laboratories used for scientific research take many forms because of the requirements of specialists in the various fields of science. A physics laboratory might contain a particle accelerator or vacuum chamber, a chemist or biologist might use a wet laboratory, while a psychologists laboratory might be a room with one-way mirrors and hidden cameras in which to observe behavior. In some laboratories, such as commonly used by computer scientists. Scientists in other fields will use other types of laboratories. Engineers use laboratories as well to design, build, and test technological devices, scientific laboratories can be found as research and learning spaces in schools and universities, industry, government, or military facilities, and even aboard ships and spacecraft. Early instances of laboratories recorded in English involved alchemy and the preparation of medicines, larger or more sophisticated equipment is generally called a scientific instrument. Both laboratory equipment and scientific instruments are increasingly being designed and shared using open hardware principles, open source labs use open source scientific hardware. The title of laboratory is used for certain other facilities where the processes or equipment used are similar to those in scientific laboratories. In many labs, though, hazards are present, in laboratories where dangerous conditions might exist, safety precautions are important. Rules exist to minimize the risk, and safety equipment is used to protect the lab user from injury or to assist in responding to an emergency. This standard is referred to as the Laboratory Standard. Under this standard, a laboratory is required to produce a Chemical Hygiene Plan which addresses the specific hazards found in its location, the CHP must be reviewed annually. Many schools and businesses employ safety, health, and environmental specialists, such as a Chemical Hygiene Officer to develop, manage, and evaluate their CHP. Additionally, third party review is used to provide an objective outside view which provides a fresh look at areas. An important element of such audits is the review of regulatory compliance, training is critical to the ongoing safe operation of the laboratory facility. Educators, staff and management must be engaged in working to reduce the likelihood of accidents, injuries, efforts are made to ensure laboratory safety videos are both relevant and engaging. The dictionary definition of laboratory at Wiktionary Media related to Laboratory at Wikimedia Commons Nobel Laureates Interactive 360° Laboratories
8.
Chemical plant
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A chemical plant is an industrial process plant that manufactures chemicals, usually on a large scale. The general objective of a plant is to create new material wealth via the chemical or biological transformation. Chemical plants use specialized equipment, units, and technology in the manufacturing process, some would consider an oil refinery or a pharmaceutical or polymer manufacturer to be effectively a chemical plant. Petrochemical plants are located adjacent to an oil refinery to minimize transportation costs for the feedstocks produced by the refinery. Speciality chemical and fine chemical plants are much smaller and not as sensitive to location. Tools have been developed for converting a base project cost from one location to another. Chemical plants use chemical processes, which are detailed industrial-scale methods, the same chemical process can be used at more than one chemical plant, with possibly differently scaled capacities at each plant. Also, a plant at a site may be constructed to utilize more than one chemical process. A chemical plant commonly has usually large vessels or sections called units or lines that are interconnected by piping or other material-moving equipment which can carry streams of material, such material streams can include fluids or sometimes solids or mixtures such as slurries. An overall chemical process is made up of steps called unit operations which occur in the individual units. A raw material going into a process or plant as input to be converted into a product is commonly called a feedstock. In addition to feedstocks for the plant as a whole, a stream of material to be processed in a particular unit can similarly be considered feed for that unit. Output streams from the plant as a whole are final products, however, final products from one plant may be intermediate chemicals used as feedstock in another plant for further processing. For example, some products from an oil refinery may used as feedstock in petrochemical plants, either the feedstock, the product, or both may be individual compounds or mixtures. It is often not worthwhile separating the components in these mixtures completely, specific levels of purity depend on product requirements, chemical processes may be run in continuous or batch operation. In batch operation, production occurs in time-sequential steps in discrete batches, a batch of feedstock is fed into a process or unit, then the chemical process takes place, then the product and any other outputs are removed. Such batch production may be repeated again and again with new batches of feedstock. Batch operation is used in smaller scale plants such as pharmaceutical or specialty chemicals production
9.
Homogeneity and heterogeneity
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Homogeneity and heterogeneity are concepts often used in the sciences and statistics relating to the uniformity in a substance or organism. A material or image that is homogeneous is uniform in composition or character, the alternate spellings homogenous and heterogenous are commonly, but incorrectly, used. Heterogenous meanwhile is a term primarily confined to pathology which refers to the property of an object in the body having its origin outside the body, the concepts are the same to every level of complexity, from atoms to populations of animals or people, and galaxies. Hence, an element may be homogeneous on a larger scale and this is known as an effective medium approach, or effective medium approximations. Various disciplines understand heterogeneity, or being heterogeneous, in different ways, heterogeneous solids, liquids, and gases may be made homogeneous by melting, stirring, or by allowing time to pass for diffusion to distribute the molecules evenly. For example, adding dye to water will create a solution at first. Entropy allows for heterogeneous substances to become homogeneous over time, a heterogeneous mixture is a mixture of two or more compounds. Examples are, mixtures of sand and water or sand and iron filings, a rock, water and oil, a salad, trail mix. A mixture can be determined to be homogeneous when everything is settled and equal, various models have been proposed to model the concentrations in different phases. The phenomena to be considered are mass rates and reaction, homogeneous reactions are chemical reactions in which the reactants and products are in the same phase, while heterogeneous reactions have reactants in two or more phases. Reactions that take place on the surface of a catalyst of a different phase are also heterogeneous, a reaction between two gases or two miscible liquids is homogeneous. A reaction between a gas and a liquid, a gas and a solid or a liquid and a solid is heterogeneous, earth is a heterogeneous substance in many aspects. E. g. rocks are inherently heterogeneous, usually occurring at the micro-scale and mini-scale, in algebra, homogeneous polynomials have the same number of factors of a given kind. This can cause problems in attempts to summarize the meaning of the studies, in medicine and genetics, a genetic or allelic heterogeneous condition is one where the same disease or condition can be caused, or contributed to, by several factors. In the case of genetics, varying different genes or alleles, in cancer research, cancer cell heterogeneity is thought to be one of the underlying reasons that make treatment of cancer difficult. In physics, heterogeneous is understood to mean having physical properties that vary within the medium, in sociology, heterogeneous may refer to a society or group that includes individuals of differing ethnicities, cultural backgrounds, sexes, or ages. Academic Press Dictionary of Science and Technology
10.
Active transport
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Active transport is usually associated with accumulating high concentrations of molecules that the cell needs, such as ions, glucose and amino acids. If the process uses chemical energy, such as adenosine triphosphate. Secondary active transport involves the use of an electrochemical gradient, examples of active transport include the uptake of glucose in the intestines in humans and the uptake of mineral ions into root hair cells of plants. In 1848, the German physiologist Emil Heinrich du Bois-Reymond suggested the possibility of transport of substances across membranes. Rosenberg formulated the concept of transport based on energetic considerations. There are two forms of transport, primary active transport and secondary active transport. In primary active transport, the involved are pumps that normally use the chemical energy in the form of ATP. Secondary active transport, however, makes use of potential energy and this involves pore-forming proteins that form channels across the cell membrane. In an antiporter, one substrate is transported in one direction across the membrane while another is cotransported in the opposite direction, in a symporter, two substrates are transported in the same direction across the membrane. If substrate molecules are moving from areas of concentration to areas of higher concentration. These proteins have receptors that bind to molecules and transport them across the cell membrane. Because energy is required in this process, it is known as active transport, examples of active transport include the transportation of sodium out of the cell and potassium into the cell by the sodium-potassium pump. Active transport often takes place in the lining of the small intestine. Plants need to absorb mineral salts from the soil or other sources, Active transport enables these cells to take up salts from this dilute solution against the direction of the concentration gradient. Primary active transport, also called direct active transport, directly uses metabolic energy to transport molecules across a membrane, most of the enzymes that perform this type of transport are transmembrane ATPases. A primary ATPase universal to all life is the sodium-potassium pump. The sodium-potassium pump maintains the potential by moving three Na+ ions out of the cell for every two K+ ions moved into the cell. Other sources of energy for Primary active transport are redox energy, ATP hydrolysis is used to transport hydrogen ions against the electrochemical gradient
11.
Passive transport
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Passive transport is a movement of ions and other atomic or molecular substances across cell membranes without need of energy input. Unlike active transport, it not require an input of cellular energy because it is instead driven by the tendency of the system to grow in entropy. The rate of passive transport depends on the permeability of the cell membrane, the four main kinds of passive transport are simple diffusion, facilitated diffusion, filtration, and osmosis. Diffusion is the net movement of material from an area of concentration to an area with lower concentration. The difference of concentration between the two areas is termed as the concentration gradient, and diffusion will continue until this gradient has been eliminated. Since diffusion moves materials from an area of concentration to an area of lower concentration. However, in cases the driving force of passive transport can not be simplified to the concentration gradient. It is also true for supersaturated solutions which are more and more important owing to the spreading of the application of amorphous solid dispersions for drug bioavailability enhancement, simple diffusion and osmosis are in some ways similar. Simple diffusion is the movement of solute from a high concentration to a lower concentration until the concentration of the solute is uniform throughout. Simple diffusion and osmosis are both forms of transport and require none of the cells ATP energy. Facilitated diffusion, also called carrier-mediated osmosis, is the movement of molecules across the membrane via special transport proteins that are embedded within the cellular membrane. Large, insoluble molecules, such as glucose, vesicles and proteins require a carrier molecule to move through the plasma membrane, therefore, it will bind with its specific carrier proteins, and the complex will then be bonded to a receptor site and moved through the cellular membrane. Facilitated diffusion is a process, the solutes move down their concentration gradient. Carrier proteins and channel proteins allow for the diffusion of molecules across the cell membrane, carrier proteins undergo conformational alterations to allow molecules to pass, while channel proteins form unblocked pores. Facilitated diffusion may be achieved as a consequence of charge gradients in addition to concentration gradients, plant cells create an unequal distribution of charge across their plasma membrane by actively taking up or excluding ions. Filtration is movement of water and solute molecules across the membrane due to hydrostatic pressure generated by the cardiovascular system. Depending on the size of the pores, only solutes of a certain size may pass through it. For example, the pores of the Bowmans capsule in the kidneys are very small, and only albumins
12.
Membrane bioreactor
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When used with domestic wastewater, MBR processes can produce effluent of high quality enough to be discharged to coastal, surface or brackish waterways or to be reclaimed for urban irrigation. Other advantages of MBRs over conventional processes include small footprint, easy retrofit, recent technical innovation and significant membrane cost reduction have enabled MBRs to become an established process option to treat wastewaters. As a result, the MBR process has now become an option for the treatment and reuse of industrial and municipal wastewaters, as evidenced by their constantly rising numbers. The current MBR market has been estimated to value around US$216 million in 2006, Membrane bioreactors can be used to reduce the footprint of an activated sludge sewage treatment system by removing some of the liquid component of the mixed liquor. This leaves a waste product that is then treated using the activated sludge process. The MBR process was introduced by the late 1960s, as soon as commercial scale ultrafiltration and microfiltration membranes were available, the original process was introduced by Dorr-Oliver Inc. and combined the use of an activated sludge bioreactor with a crossflow membrane filtration loop. The flat sheet membranes used in process were polymeric and featured pore sizes ranging from 0.003 to 0.01 μm. As a result, the focus was on the attainment of high fluxes, because of the poor economics of the first generation MBRs, they only found applications in niche areas with special needs, such as isolated trailer parks or ski resorts. The breakthrough for the MBR came in 1989 with Yamamoto and co-workers idea of submerging the membranes in the bioreactor, until then, MBRs were designed with the separation device located external to the reactor and relied on high transmembrane pressure to maintain filtration. With the membrane directly immersed in the bioreactor, submerged MBR systems are preferred to sidestream configuration. The submerged configuration relies on coarse bubble aeration to produce mixing, the energy demand of the submerged system can be up to 2 orders of magnitude lower than that of the sidestream systems and submerged systems operate at a lower flux, demanding more membrane area. In submerged configurations, aeration is considered as one of the parameters in process performance both hydraulic and biological. Aeration maintains solids in suspension, scours the membrane surface and provides oxygen to the biomass, leading to a better biodegradability, the other key steps in the recent MBR development were the acceptance of modest fluxes, and the idea to use two-phase bubbly flow to control fouling. The lower operating cost obtained with the submerged configuration along with the decrease in the membrane cost encouraged an exponential increase in MBR plant installations from the mid 90s. Since then, further improvements in the MBR design and operation have been introduced and incorporated into larger plants. While early MBRs were operated at solid retention times as high as 100 days with MLSS up to 30 g/L, thanks to these new operating conditions, the oxygen transfer and the pumping cost in the MBR have tended to decrease and overall maintenance has been simplified. Typical hydraulic retention times range between 3 and 10 hours, in terms of membrane configurations, mainly hollow fiber and flat sheet membranes are applied for MBR applications. Despite the more favourable energy usage of submerged membranes, there continued to be a market for the side stream configuration, for ease of maintenance the side stream configuration can be installed on a lower level in a plant building
13.
Reverse osmosis
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Reverse osmosis is a water purification technology that uses a semipermeable membrane to remove ions, molecules, and larger particles from drinking water. In reverse osmosis, a pressure is used to overcome osmotic pressure, a colligative property, that is driven by chemical potential differences of the solvent. Reverse osmosis can remove many types of dissolved and suspended species from water, including bacteria, the result is that the solute is retained on the pressurized side of the membrane and the pure solvent is allowed to pass to the other side. To be selective, this membrane should not allow large molecules or ions through the pores, in the normal osmosis process, the solvent naturally moves from an area of low solute concentration, through a membrane, to an area of high solute concentration. Applying an external pressure to reverse the flow of pure solvent. The process is similar to other membrane technology applications, however, key differences are found between reverse osmosis and filtration. Reverse osmosis also involves diffusion, making the process dependent on pressure, flow rate, reverse osmosis is most commonly known for its use in drinking water purification from seawater, removing the salt and other effluent materials from the water molecules. The process of osmosis through semipermeable membranes was first observed in 1748 by Jean-Antoine Nollet, for the following 200 years, osmosis was only a phenomenon observed in the laboratory. In 1950, the University of California at Los Angeles first investigated desalination of seawater using semipermeable membranes, cadottes patent on this process was the subject of litigation and has since expired. Almost all commercial reverse osmosis membrane is now made by this method, by the end of 2001, about 15,200 desalination plants were in operation or in the planning stages, worldwide. In 1977 Cape Coral, Florida became the first municipality in the United States to use the RO process on a scale with an initial operating capacity of 3 million gallons per day. By 1985, due to the growth in population of Cape Coral. In most cases, the membrane is designed to only water to pass through this dense layer. This process is best known for its use in desalination, but since the early 1970s, it has also used to purify fresh water for medical, industrial. Around the world, household drinking water systems, including a reverse osmosis step, are commonly used for improving water for drinking and cooking. CTA membrane is a paper by-product membrane bonded to a layer and are made to allow contact with chlorine in the water. These require an amount of chlorine in the water source to prevent bacteria from forming on it. The typical rejection rate for CTA membranes is 85–95%, the cellulose triacetate membrane is prone to rotting unless protected by chlorinated water, while the thin film composite membrane is prone to breaking down under the influence of chlorine
14.
Hollow fiber membrane
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Hollow fiber membranes are a class of artificial membranes containing a semi-permeable barrier in the form of a hollow fiber. Most commercial hollow fiber membranes are packed into cartridges which can be used for a variety of liquid, HFMs are commonly produced using artificial polymers. The specific production methods involved are heavily dependent on the type of polymer used as well as its molecular weight, dry Spinning, in which a polymer is dissolved in an appropriate solvent and extruded through a spinneret into air. Dry-Jet Wet Spinning, in which a polymer is dissolved in a solvent and extruded into air. Wet spinning, in which a polymer is dissolved and extruded directly into a coagulant, common to each of these methods is the use of a spinneret, a device containing a needle through which solvent is extruded and an annulus through which a polymer solution is extruded. As the polymer is extruded through the annulus of the spinneret, as the polymer exits the spinneret, it solidifies into a membrane through a process known as phase inversion. Extrusion of the polymer and solvent through the spinneret can be accomplished either through the use of gas-extrusion or a metered pump, some of the polymers most commonly used for fabricating HFMs include cellulose acetate, polysulfone, polyethersulfone, and polyvinylidene fluoride. The properties of HFMs can be characterized using the same techniques used for other types of membranes. Pore diameter can also be measured via a technique known as evapoporometry, depending on the diameters of pores in an HFM, scanning electron microscopy or transmission electron microscopy can be used to yield a qualitative perspective of pore size. Membrane List of synthetic polymers Reverse Osmosis Nanofiltration Ultrafiltration Microfiltration
15.
Cross-flow filtration
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In chemical engineering, biochemical engineering and protein purification, crossflow filtration is a type of filtration. Cross-flow filtration gets its name because the majority of the feed flow travels tangentially across the surface of the filter, rather than into the filter. The principal advantage of this is that the cake is substantially washed away during the filtration process. It can be a process, unlike batch-wise dead-end filtration. Industrial examples of this include the extraction of soluble antibiotics from fermentation liquors, in crossflow filtration, the feed is passed across the filter membrane at positive pressure relative to the permeate side. With crossflow filtration the tangential motion of the bulk of the fluid across the membrane causes trapped particles on the surface to be rubbed off. This means that a filter can operate continuously at relatively high solids loads without blinding. Filtration membranes can be polymeric or ceramic, depending upon the application, the principles of cross-flow filtration are used in reverse osmosis, nanofiltration, ultrafiltration and microfiltration. When purifying water, it can be very cost effective in comparison to the traditional evaporation methods, in protein purification, the term Tangential Flow Filtration is used to describe cross-flow filtration with membranes. The process can be used at different stages during purification, depending on the type of membrane selected, in the photograph of an industrial filtration unit, it is possible to see that the recycle pipework is considerably larger than either the feed pipework or the permeate pipework. These pipe sizes are directly related to the proportion of liquid flows through the unit, a dedicated pump is used to recycle the feed several times around the unit before the solids-rich retentate is transferred to the next part of the process. Backwashing is not applicable to spirally wound membranes and is not a practice in most applications. Clean-in-place systems are used to remove fouling from membranes after extensive use. The CIP process may use detergents, reactive agents such as sodium hypochlorite and acids and alkalis such as citric acid, sodium hypochlorite must be removed from the feed in some membrane plants. Oxidation will degrade the membranes to a point where they no longer perform at rated rejection levels and have to be replaced. Bleach can be added to a NaOH sodium hydroxide CIP during an initial system start-up before spirally-wound membranes are loaded into the plant to help disinfect the system. Bleach is also used to CIP perforated stainless steel membranes, as their tolerance for sodium hypochlorite is much higher than a spirally-wound membrane, caustics and acids are most often used as primary CIP chemicals. Caustic removes organic fouling and acid removes minerals, enzyme solutions are also used in some systems for helping remove organic fouling material from the membrane plant
16.
Biofouling
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Biofouling or biological fouling is the accumulation of microorganisms, plants, algae, or animals on wetted surfaces. Such accumulation is referred to as epibiosis when the host surface is another organism, antifouling is the ability of specifically designed materials and coatings to remove or prevent biofouling by any number of organisms on wetted surfaces. Specifically, the buildup of biofouling on marine vessels poses a significant problem, in some instances, the hull structure and propulsion systems can be damaged. The accumulation of biofoulers on hulls can increase both the volume of a vessel and the hydrodynamic friction, leading to increased drag of up to 60%. The drag increase has been seen to decrease speeds by up to 10%, with fuel typically comprising up to half of marine transport costs, antifouling methods are estimated to save the shipping industry around $60 billion per year. Increased fuel use due to biofouling contributes to environmental effects and is predicted to increase emissions of carbon dioxide. A variety of antifouling methods have historically been implemented to combat biofouling, recently, scientists have begun researching antifouling methods inspired by living organisms. This type of imitation is known as biomimicry. The variety among biofouling organisms is highly diverse, and extends far beyond attachment of barnacles, according to some estimates, over 1700 species comprising over 4000 organisms are responsible for biofouling. Biofouling is divided into microfouling — biofilm formation and bacterial adhesion —, due to the distinct chemistry and biology that determine what prevents them from settling, organisms are also classified as hard- or soft-fouling types. Calcareous fouling organisms include barnacles, encrusting bryozoans, mollusks, polychaete and other tube worms, examples of non-calcareous fouling organisms are seaweed, hydroids, algae and biofilm slime. Together, these form a fouling community. Marine fouling is typically described as following four stages of ecosystem development, the chemistry of biofilm formation describes the initial steps prior to colonization. Within the first minute the van der Waals interaction causes the surface to be covered with a conditioning film of organic polymers. In the next 24 hours, this allows the process of bacterial adhesion to occur. By the end of the first week, the nutrients and ease of attachment into the biofilm allow secondary colonizers of spores of macroalgae. Within 2 to 3 weeks, the tertiary colonizers- the macrofoulers- have attached and these include tunicates, mollusks and sessile Cnidarians. Governments and industry more than US$5.7 billion annually to prevent
17.
Backwashing (water treatment)
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Backwashing is a form of preventive maintenance so that the filter media can be reused. In water treatment plants, backwashing can be a process that is run by local programmable logic controllers. Water treatment filters that can be backwashed include rapid sand filters, pressure filters, diatomaceous earth filters are backwashed according to the proprietary arrangement of pumps, valves and filters associated with the filtration system. Slow sand filters and self-cleaning screen filters employ mechanisms other than backwashing to remove trapped particles, to keep water treatment filters functional, they have to be cleaned periodically to remove particulates. Ineffective backwashing is one of the reasons that water treatment filters fail. Backwashing of granular media filters involves several steps, first, the filter is taken off line and the water is drained to a level that is above the surface of the filter bed. Next, compressed air is pushed up through the filter material causing the bed to expand breaking up the compacted filter bed. In some applications, air and water streams are simultaneously pushed upwards through the media followed by a rinse water wash. Backwashing continues for a time, or until the turbidity of the backwash water is below an established value. At the end of the cycle, the upward flow of water is terminated. Water to be filtered is then applied to the surface until the filter clogs. Some water treatment filters use surface wash systems that break up the heavily clogged, surface wash systems are buried in the top of the filter media or are suspended above the filter media surface. John R. Baylis developed a grid system which consisted of pipes with nozzles that injected jets of water into the filter material during expansion. Rotating arms use jets of water to break up the clogged filter surface, a surface wash step in a backwash cycle usually takes place at the beginning of the filter bed cleaning process. Spent backwash water is discharged without treatment to a sanitary sewer system or is treated and recycled within the plant. Historically, backwash water was discharged directly to water supplies, however. Used backwash water contains high concentrations of particulate material, typical treatment processes include coagulation, flocculation and sedimentation. High molecular weight synthetic polymers are sometimes added to facilitate the formation of settleable floc
18.
Unit operation
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In chemical engineering and related fields, a unit operation is a basic step in a process. Unit operations involve a change or chemical transformation such as separation, crystallization, evaporation, filtration, polymerization, isomerization. For example, in processing, homogenization, pasteurization, chilling. A process may require many unit operations to obtain the product from the starting materials. Historically, the different chemical industries were regarded as different industrial processes, arthur Dehon Little propounded the concept of unit operations to explain industrial chemistry processes in 1916. They summed up these processes into unit operations. Each unit operation follows the physical laws and may be used in all relevant chemical industries. For instance, the engineering is required to design a mixer for either napalm or porridge, even if the use. The unit operations form the principles of chemical engineering. Chemical engineering unit operations consist of five classes, Fluid flow processes, including transportation, filtration. Heat transfer processes, including evaporation and heat exchange, mass transfer processes, including gas absorption, distillation, extraction, adsorption, and drying. Thermodynamic processes, including gas liquefaction, and refrigeration, mechanical processes, including solids transportation, crushing and pulverization, and screening and sieving. A pure unit operation is a transport process, while a mixed chemical/physical process requires modeling both the physical transport, such as diffusion, and the chemical reaction. This is usually necessary for designing catalytic reactions, and is considered a separate discipline, combining a stack of these gives the system of equations for the whole column. There is a range of solutions, because a higher reflux ratio enables fewer plates, the engineer must then find the optimal solution with respect to acceptable volume holdup, column height and cost of construction. Distillation Design Separation process Transport phenomena Unit Operations of Chemical Engineering Process simulation Unit process
19.
Membrane technology
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Membrane technology covers all engineering approaches for the transport of substances between two fractions with the help of permeable membranes. In general, mechanical separation processes for separating gaseous or liquid streams use membrane technology, Membrane separation processes operate without heating and therefore use less energy than conventional thermal separation processes such as distillation, sublimation or crystallization. The separation process is physical and both fractions can be used. Cold separation using membrane technology is used in the food technology, biotechnology. Furthermore, using membranes enables separations to take place that would be impossible using thermal separation methods, depending on the type of membrane, the selective separation of certain individual substances or substance mixtures is possible. In waste water treatment, membrane technology is becoming increasingly important, with the help of ultra/microfiltration it is possible to remove particles, colloids and macromolecules, so that waste-water can be disinfected in this way. This is needed if waste-water is discharged into sensitive waters especially those designated for contact water-sports, about half of the market is in medical applications such as use in artificial kidneys to remove toxic substances by hemodialysis and as artificial lung for bubble-free supply of oxygen in the blood. The importance of technology is growing in the field of environmental protection. Even in modern energy recovery techniques membranes are used, for example in fuel cells. Two basic models can be distinguished for mass transfer through the membrane, the solution-diffusion model, in real membranes, these two transport mechanisms certainly occur side by side, especially during ultra-filtration. In the solution-diffusion model, transport occurs only by diffusion, the component that needs to be transported must first be dissolved in the membrane. This principle is important for dense membranes without natural pores such as those used for reverse osmosis. During the filtration process a boundary layer forms on the membrane and this concentration gradient is created by molecules which cannot pass through the membrane. The effect is referred as concentration polarization and, occurring during the filtration, concentration polarization is, in principle, reversible by cleaning the membrane which results in the initial flux being almost totally restored. Using a tangential flow to the membrane can also minimize concentration polarization, transport through pores – in the simplest case – is done convectively. This requires the size of the pores to be smaller than the diameter of the two separate components, membranes which function according to this principle are used mainly in micro- and ultrafiltration. They are used to separate macromolecules from solutions, colloids from a dispersion or remove bacteria, during this process the retained particles or molecules form a pulpy mass on the membrane, and this blockage of the membrane hampers the filtration. This blockage can be reduced by the use of the cross-flow method, the tangential flow on the front creates a shear stress that cracks the filter cake and reduces the fouling. g
20.
Fouling
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Fouling is the accumulation of unwanted material on solid surfaces to the detriment of function. The fouling materials can consist of living organisms or a non-living substance. Other terms used in the literature to describe fouling include, deposit formation, encrustation, crudding, deposition, scaling, scale formation, slagging, and sludge formation. This article is devoted to the fouling of industrial heat exchangers. In the cooling technology and other fields, a distinction is made between macro fouling and micro fouling. Of the two, micro fouling is the one which is more difficult to prevent and therefore more important. Macro fouling is caused by coarse matter of biological or inorganic origin. Such matter enters into the water circuit through the cooling water pumps from sources like the open sea. In closed circuits, like cooling towers, the ingress of macro fouling into the tower basin is possible through open canals or by the wind. Sometimes, parts of the tower internals detach themselves and are carried into the cooling water circuit. Such substances can foul the surfaces of heat exchangers and may cause deterioration of the relevant heat transfer coefficient and they may also create flow blockages, redistribute the flow inside the components, or cause fretting damage. Examples Manmade refuse, Detached internal parts of components, Tools and other foreign objects accidentally left after maintenance, Algae, Mussels, Leaves and these are most often water solutions, but non-aqueous precipitation fouling is also known. Precipitation fouling is a common problem in boilers and heat exchangers operating with hard water. Through changes in temperature, or solvent evaporation or degasification, the concentration of salts may exceed the saturation, in general, the dependence of the salt solubility on temperature or presence of evaporation will often be the driving force for precipitation fouling. The important distinction is between salts with normal or retrograde dependence of solubility on temperature, the salts with the normal solubility increase their solubility with increasing temperature and thus will foul the cooling surfaces. The salts with inverse or retrograde solubility will foul the heating surfaces, an example of the temperature dependence of solubility is shown in the figure. Calcium sulfate is a common precipitation foulant of heating surfaces due to its retrograde solubility, precipitation fouling can also occur in the absence of heating or vaporization. For example, calcium sulfate decreases it solubility with decreasing pressure and this can lead to precipitation fouling of reservoirs and wells in oil fields, decreasing their productivity with time
21.
Cost
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In production, research, retail, and accounting, a cost is the value of money that has been used up to produce something, and hence is not available for use anymore. In business, the cost may be one of acquisition, in case the amount of money expended to acquire it is counted as cost. In this case, money is the input that is gone in order to acquire the thing, usually, the price also includes a mark-up for profit over the cost of production. More generalized in the field of economics, cost is a metric that is totaling up as a result of a process or as a differential for the result of a decision, hence cost is the metric used in the standard modeling paradigm applied to economic processes. Costs are often further described based on their timing or their applicability, in accounting, costs are the monetary value of expenditures for supplies, services, labor, products, equipment and other items purchased for use by a business or other accounting entity. It is the amount denoted on invoices as the price and recorded in bookkeeping records as an expense or asset cost basis. Opportunity cost, also referred to as economic cost is the value of the best alternative that was not chosen in order to pursue the current endeavor—i. e, what could have been accomplished with the resources expended in the undertaking. In theoretical economics, cost used without qualification often means opportunity cost, when a transaction takes place, it typically involves both private costs and external costs. Private costs are the costs that the buyer of a good or service pays the seller and this can also be described as the costs internal to the firms production function. External costs, in contrast, are the costs that people other than the buyer are forced to pay as a result of the transaction, the bearers of such costs can be either particular individuals or society at large. Note that external costs are often both non-monetary and problematic to quantify for comparison with monetary values. They include things like pollution, things that society will likely have to pay for in some way or at time in the future. Social costs are the sum of private costs and external costs, for example, the manufacturing cost of a car reflects the private cost for the manufacturer. The polluted waters or polluted air also created as part of the process of producing the car is an external cost borne by those who are affected by the pollution or who value unpolluted air or water. Because the manufacturer does not pay for this external cost, and does not include this cost in the price of the car, the air pollution from driving the car is also an externality produced by the car user in the process of using his good. The driver does not compensate for the damage caused by using the car. When developing a plan for a new or existing company, product, or project. This is done in both business and government, costs are often underestimated, resulting in cost overrun during execution
22.
International Standard Book Number
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The International Standard Book Number is a unique numeric commercial book identifier. An ISBN is assigned to each edition and variation of a book, for example, an e-book, a paperback and a hardcover edition of the same book would each have a different ISBN. The ISBN is 13 digits long if assigned on or after 1 January 2007, the method of assigning an ISBN is nation-based and varies from country to country, often depending on how large the publishing industry is within a country. The initial ISBN configuration of recognition was generated in 1967 based upon the 9-digit Standard Book Numbering created in 1966, the 10-digit ISBN format was developed by the International Organization for Standardization and was published in 1970 as international standard ISO2108. Occasionally, a book may appear without a printed ISBN if it is printed privately or the author does not follow the usual ISBN procedure, however, this can be rectified later. Another identifier, the International Standard Serial Number, identifies periodical publications such as magazines, the ISBN configuration of recognition was generated in 1967 in the United Kingdom by David Whitaker and in 1968 in the US by Emery Koltay. The 10-digit ISBN format was developed by the International Organization for Standardization and was published in 1970 as international standard ISO2108, the United Kingdom continued to use the 9-digit SBN code until 1974. The ISO on-line facility only refers back to 1978, an SBN may be converted to an ISBN by prefixing the digit 0. For example, the edition of Mr. J. G. Reeder Returns, published by Hodder in 1965, has SBN340013818 -340 indicating the publisher,01381 their serial number. This can be converted to ISBN 0-340-01381-8, the check digit does not need to be re-calculated, since 1 January 2007, ISBNs have contained 13 digits, a format that is compatible with Bookland European Article Number EAN-13s. An ISBN is assigned to each edition and variation of a book, for example, an ebook, a paperback, and a hardcover edition of the same book would each have a different ISBN. The ISBN is 13 digits long if assigned on or after 1 January 2007, a 13-digit ISBN can be separated into its parts, and when this is done it is customary to separate the parts with hyphens or spaces. Separating the parts of a 10-digit ISBN is also done with either hyphens or spaces, figuring out how to correctly separate a given ISBN number is complicated, because most of the parts do not use a fixed number of digits. ISBN issuance is country-specific, in that ISBNs are issued by the ISBN registration agency that is responsible for country or territory regardless of the publication language. Some ISBN registration agencies are based in national libraries or within ministries of culture, in other cases, the ISBN registration service is provided by organisations such as bibliographic data providers that are not government funded. In Canada, ISBNs are issued at no cost with the purpose of encouraging Canadian culture. In the United Kingdom, United States, and some countries, where the service is provided by non-government-funded organisations. Australia, ISBNs are issued by the library services agency Thorpe-Bowker
Schematic process of dead-end and cross-flow filtration
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