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Encyclopedia > Water purification
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Water purification is the process of removing contaminants from a raw water source. The goal is to produce water for a specific purpose with a treatment profile designed to limit the inclusion of specific materials; most water is purified for human consumption (drinking water). Water purification may also be designed for a variety of other purposes, including to meet the requirements of medical, pharmacology, chemical and industrial applications. Methods include, but are not limited to: ultraviolet light, filtration, water softening, reverse osmosis, ultrafiltration, deionization and powdered activated carbon treatment. Image File history File links Sustainable_development. ... Image File history File links Portal. ... Tap water Mineral Water Water of sufficient quality to serve as drinking water is termed potable water whether it is used as such or not. ... A low pressure mercury vapor discharge tube floods the inside of a hood with shortwave UV light when not in use, sterilizing microbiological contaminants from irradiated surfaces. ... This article is about operation of solid-fluid separation. ... A water softener reduces the calcium or magnesium ion concentration in hard water. ... Reverse osmosis (RO) is a separation process that uses pressure to force a solution through a membrane that retains the solute on one side and allows the pure solvent to pass to the other side. ... Ultrafiltration (UF) is a variety of membrane filtration in which hydrostatic pressure forces a liquid against a semipermeable membrane. ... Deionized water (DI water or de-ionized water; also spelled deionised water, see spelling differences) is water that lacks ions, such as cations from sodium, calcium, iron, copper and anions such as chloride and bromide. ... Powdered Activated Carbon Treatment (PACT) is a wastewater technology in which powdered activated carbon is added to an anaerobic or aerobic treatment system. ...


Water purification may remove: particulate sand; suspended particles of organic material; parasites, Giardia; Cryptosporidium; bacteria; algae; viruses; fungi; minerals such as calcium, silica, and magnesium; and toxic metals like lead, copper, and chromium. Some purification may be elective in the purification process, including smell (hydrogen sulfide remediation), taste (mineral extraction), and appearance (iron incapsulation). For other uses, see Sand (disambiguation). ... It has been suggested that this article or section be merged into Mixture. ... A particle is Look up Particle in Wiktionary, the free dictionary In particle physics, a basic unit of matter or energy. ... Organic material or organic matter is informally used to denote a material that originated as a living organism; most such materials contain carbon and are capable of decay. ... Binomial name Giardia lamblia (Kunstler, 1882) Giardia lamblia (formerly also Lamblia intestinalis) is a protozoan parasite that infects the gastrointestinal tract of humans. ... Species Cryptosporidium bailey Cryptosporidium meleagridis Cryptosporidium muris Cryptosporidium parvum Cryptosporidium serpentis Cryptosporidium is a protozoan pathogen of the Phylum Apicomplexa and causes a diarrheal illness called cryptosporidiosis. ... Phyla Actinobacteria Aquificae Chlamydiae Bacteroidetes/Chlorobi Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Lentisphaerae Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Verrucomicrobia Bacteria (singular: bacterium) are unicellular microorganisms. ... For the programming language, see algae (programming language). ... This article is about biological infectious particles. ... Divisions Chytridiomycota Zygomycota Ascomycota Basidiomycota The Fungi (singular: fungus) are a large group of organisms ranked as a kingdom within the Domain Eukaryota. ... For other uses, see Mineral (disambiguation). ... For other uses, see Calcium (disambiguation). ... The chemical compound silicon dioxide, also known as silica, is the oxide of silicon, chemical formula SiO2. ... General Name, symbol, number magnesium, Mg, 12 Chemical series alkaline earth metals Group, period, block 2, 3, s Appearance silvery white solid at room temp Standard atomic weight 24. ... General Name, Symbol, Number lead, Pb, 82 Chemical series Post-transition metals or poor metals Group, Period, Block 14, 6, p Appearance bluish gray Standard atomic weight 207. ... For other uses, see Copper (disambiguation). ... REDIRECT [[ Insert text]]EWWWWWWWWWWWWW YO General Name, symbol, number chromium, Cr, 24 Chemical series transition metals Group, period, block 6, 4, d Appearance silvery metallic Standard atomic weight 51. ... Hydrogen sulfide (or hydrogen sulphide) is the chemical compound with the formula H2S. This colorless, toxic and flammable gas is responsible for the foul odour of rotten eggs and flatulence. ... Generally, remediation means giving a remedy. ...


Governments usually dictate the standards for drinking water quality. These standards will require minimum / maximum set points of contaminants and the inclusion of control elements that produce drinking water. Quality standards in many countries require specific amounts of disinfectant (such as chlorine) in the water after it leaves the water treatment plant (WTP), to reduce the risk of re-contamination while the water is in the distribution system. Water quality is the physical, chemical and biological characteristics of water, characterized through the methods of hydrometry. ... This is an article about antimicrobial agents. ... General Name, symbol, number chlorine, Cl, 17 Chemical series nonmetals Group, period, block 17, 3, p Appearance yellowish green Standard atomic weight 35. ...

A homemade waterfilter is often employed for making drinking water
A homemade waterfilter is often employed for making drinking water

It is not possible to tell whether water is safe to drink just by looking at it. Simple procedures such as boiling or the use of a household activated carbon filter are not sufficient for treating all the possible contaminants that may be present in water from an unknown source. Even natural spring water - considered safe for all practical purposes in the 1800s - must now be tested before determining what kind of treatment, if any, is needed. Chemical analysis, while expensive, is the only way to obtain the information necessary for deciding on method of purification. Boiling, a type of phase transition, is the rapid vaporization of a liquid, which typically occurs when a liquid is heated to its boiling point, the temperature at which the vapor pressure of the liquid is equal to the pressure exerted on the liquid by the surrounding atmospheric pressure. ... Activated carbon Activated carbon, also called activated charcoal or activated coal, is a general term which covers carbon material mostly derived from charcoal. ... A natural spring on Mackinac Island in Michigan. ... // Invention of the Jacquard loom in 1801. ...

Control room and schematics of the water purification plant to Lac de Bret, Switzerland.
Control room and schematics of the water purification plant to Lac de Bret, Switzerland.

Contents

Image File history File linksMetadata Size of this preview: 800 × 533 pixel Image in higher resolution (4368 × 2912 pixel, file size: 1. ... Image File history File linksMetadata Size of this preview: 800 × 533 pixel Image in higher resolution (4368 × 2912 pixel, file size: 1. ...

Sources of drinking water

Further information: Water supply
  1. Groundwater: The water emerging from some deep ground water may have fallen as rain many decades, hundreds, thousands or in some cases millions of years ago. Soil and rock layers naturally filter the ground water to a high degree of clarity before it is pumped to the treatment plant. Such water may emerge as springs, artesian springs, or may be extracted from boreholes or wells. Deep ground water is generally of very high bacteriological quality (i.e., pathogenic bacteria or the pathogenic protozoa are typically absent), but the water typically is rich in dissolved solids, especially carbonates and sulfates of calcium and magnesium. Depending on the strata through which the water has flowed, other ions may also be present including chloride, and bicarbonate. There may be a requirement to reduce the iron or manganese content of this water to make it pleasant for drinking, cooking, and laundry use. Disinfection may also be required. Where groundwater recharge is practised, it is equivalent to lowland surface waters for treatment purposes.
  2. Upland lakes and reservoirs: Typically located in the headwaters of river systems, upland reservoirs are usually sited above any human habitation and may be surrounded by a protective zone to restrict the opportunities for contamination. Bacteria and pathogen levels are usually 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 which require adjustment.
  3. Rivers, canals and low land reservoirs: Low land surface waters will have a significant bacterial load and may also contain algae, suspended solids and a variety of dissolved constituents.
  4. 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 vapour.
  5. Rainwater harvesting or fog collection which collects water from the atmosphere can be used especially in areas with significant dry seasons and in areas which experience fog even when there is little rain.

Water supply is the process of self-provision or provision by third parties of water of various qualities to different users. ... Loess field in Germany Surface-water-gley developed in glacial till, Northern Ireland For other uses, see Soil (disambiguation). ... Geological strata giving rise to an Artesian well. ... Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Omnibacteria Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular, bacterium) are a major group of living organisms. ... Ball-and-stick model of the carbonate ion, CO32− For other meanings, see Carbonate (disambiguation) In chemistry, a carbonate is a salt or ester of carbonic acid. ... The sulfate anion, SO42− The structure and bonding of the sulfate ion In inorganic chemistry, a sulfate (IUPAC-recommended spelling; also sulphate in British English) is a salt of sulfuric acid. ... For other uses, see Calcium (disambiguation). ... General Name, symbol, number magnesium, Mg, 12 Chemical series alkaline earth metals Group, period, block 2, 3, s Appearance silvery white solid at room temp Standard atomic weight 24. ... For other uses, see strata (novel) and strata title. ... The chloride ion is formed when the element chlorine picks up one electron to form an anion (negatively-charged ion) Cl−. The salts of hydrochloric acid HCl contain chloride ions and can also be called chlorides. ... For baking soda, see Sodium bicarbonate In inorganic chemistry, a bicarbonate (IUPAC-recommended nomenclature: hydrogencarbonate) is an intermediate form in the deprotonation of carbonic acid. ... Fe redirects here. ... General Name, symbol, number manganese, Mn, 25 Chemical series transition metals Group, period, block 7, 4, d Appearance silvery metallic Standard atomic weight 54. ... Disinfection is the destruction of pathogenic and other kinds of microorganisms by physical or chemical means. ... The Ashokan Reservoir, located in Ulster County, New York, USA. It is one of 19 that supplies New York City with drinking water. ... Leishmania donovani, (a species of protozoan) in a bone marrow cell Protozoa (in Greek proton = first and zoa = animals) are unicellular eukaryotes, (singular protozoan). ... For the programming language, see algae (programming language). ... Humic acid is one of the major components of humic substances which are dark brown and major constituents of soil organic matter humus that contributes to soil chemical and physical quality and are also precursors of some fossil fuels. ... For other uses, see PH (disambiguation). ... An Atmospheric water generator (AWG), or atmospheric condenser, produces pure drinking water from the humidity of the surrounding air. ... View of a Johad at village Thathawata View of a stepwell at Fatehpur, Shekhawati. ... To meet Wikipedias quality standards, this article or section may require cleanup. ...

Treatment

The processes below are the ones commonly used in water purification plants. Some or most may not be used depending on the scale of the plant and quality of the water.


Pre-treatment

  1. 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 appropriate materials and constructed so that accidental contamination does not occur.
  2. Screening (see also screen filter) - The first step in purifying surface water is to remove large debris such as sticks, leaves, trash and other large particles which may interfere with subsequent purification steps. Most deep groundwater does not need screening before other purification steps.
  3. Storage - Water from rivers may also be stored in bankside reservoirs for periods between a few days and many months to allow natural biological purification to take place. This is especially important if treatment is by slow sand filters. Storage reservoirs also provide a buffer against short periods of drought or to allow water supply to be maintained during transitory pollution incidents in the source river.
  4. Pre-conditioning - Many waters rich in hardness salts are treated with soda-ash (Sodium carbonate) to precipitate calcium carbonate out utilising the common ion effect.
  5. Pre-chlorination - In many plants the incoming water was chlorinated to minimise the growth of fouling organisms on the pipe-work and tanks. Because of the potential adverse quality effects (see chlorine below), this has largely been discontinued.[citation needed]

Widely varied techniques are available to remove the fine solids, micro-organisms and some dissolved inorganic and organic materials. 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. A screen filter is a type of filter utilizing a rigid or flexible screen to separate sand and other fine particles out of water for irrigation or other applications. ... Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of lithologic formations. ... Bankside reservoirs are man-made reservoirs generally sited close to a river from which water is pumped to be used for potable water supply. ... Slow sand filters are used in water purification for treating raw water to produce a potable product. ... Fields outside Benambra, Victoria, Australia suffering from drought conditions A drought is an extended period of months or years when a region notes a deficiency in its water supply. ... Raw sewage and industrial waste flows into the U.S. from Mexico as the New River passes from Mexicali, Baja California to Calexico, California Water pollution is the contamination of water bodies such as lakes, rivers, oceans, and groundwater caused by human activities, which can be harmful to organisms and... Sodium carbonate (also known as washing soda or soda ash), Na2CO3, is a sodium salt of carbonic acid. ... Calcium carbonate is a chemical compound, with the chemical formula CaCO3. ... The common-ion effect is a term used to describe the effect on a solution of two dissolved solutes that contain the same ion. ...


pH adjustment

Distilled water has an average pH of 7 (neither alkaline nor acidic) and sea water has an average pH of 8.3 (slightly alkaline). If the water is acidic (lower than 7), lime or soda ash is added to raise the pH. Lime is the more common of the two additives because it is cheap, but it also adds to the resulting water hardness. Making the water slightly alkaline ensures that coagulation and flocculation processes work effectively and also helps to minimize the risk of lead being dissolved from lead pipes and lead solder in pipe fittings. If the water is alkaline, acid (HCl) and carbon dioxide (CO2) are commonly added to lower pH. Having an alkaline water does not assure that deposits on the pipe i.e. lead or copper are not released into the water. Changing the electrolytic properties of the water are more indicative to release lead or copper into the water. For other uses, see PH (disambiguation). ... This article or section does not adequately cite its references or sources. ... Sodium carbonate or soda ash, Na2CO3, is a sodium salt of carbonic acid. ... For other uses, see PH (disambiguation). ... This article is about the clotting of blood. ... This article needs additional references or sources for verification. ... General Name, Symbol, Number lead, Pb, 82 Chemical series Post-transition metals or poor metals Group, Period, Block 14, 6, p Appearance bluish gray Standard atomic weight 207. ... A solder is a fusible metal alloy, with a melting point or melting range of 180-190°C (360-370 °F), which is melted to join metallic surfaces, especially in the fields of electronics and plumbing, in a process called soldering. ...

floc floating at the surface of a basin
floc floating at the surface of a basin
Mechanical system to push floc out of the water basin
Mechanical system to push floc out of the water basin

Image File history File linksMetadata Size of this preview: 800 × 533 pixel Image in higher resolution (4368 × 2912 pixel, file size: 4. ... Image File history File linksMetadata Size of this preview: 800 × 533 pixel Image in higher resolution (4368 × 2912 pixel, file size: 4. ... The introduction of this article does not provide enough context for readers unfamiliar with the subject. ... Image File history File linksMetadata Size of this preview: 800 × 533 pixel Image in higher resolution (4368 × 2912 pixel, file size: 4. ... Image File history File linksMetadata Size of this preview: 800 × 533 pixel Image in higher resolution (4368 × 2912 pixel, file size: 4. ...

Flocculation

Flocculation is a process which clarifies the water. Clarifying means removing any turbidity or colour so that the water is clear and colourless. Clarification is done by causing a precipitate to form in the water which can be removed using simple physical methods. Initially the precipitate forms as very small particles but as the water is gently stirred, these particles stick together to form bigger particles - this process is sometimes called flocculation. Many of the small particles that were originally present in the raw water absorb onto the surface of these small precipitate particles and so get incorporated into the larger particles that coagulation produces. In this way the coagulated precipitate takes most of the suspended matter out of the water and is then filtered off, generally by passing the mixture through a coarse sand filter or sometimes through a mixture of sand and granulated anthracite (high carbon and low volatiles coal). Coagulants or flocculating agents that may be used include: Anthracite coal Anthracite (Greek Ανθρακίτης, literally a form of coal, from Anthrax [Άνθραξ], coal) is a hard, compact variety of mineral coal that has a high luster. ... Volatiles are that group of compounds with low boiling points (see volatile) that are associated with a planets or moons crust and/or atmosphere. ...

  1. Iron (III) hydroxide. This is formed by adding a solution of an iron (III) compound such as iron (III) chloride to pre-treated water with a pH of 7 or greater. Iron (III) hydroxide is extremely insoluble and forms even at a pH as low as 7. Commercial formulations of iron salts were traditionally marketed in the UK under the name Cuprus.
  2. Aluminium hydroxide is also widely used as the flocculating precipitate although there have been concerns about possible health impacts and mis-handling led to a severe poisoning incident in 1988 at Camelford in south-west UK when the coagulant was introduced directly into the holding reservoir of final treated water.
  3. Aluminium hydroxychloride is an artificially produced polymer and is one of a class of synthetic polymers that are now widely used. These polymers have a high molecular weight and form very stable and readily removed flocs but tend to be more expensive in use compared to inorganic materials.

R-phrases , S-phrases , Related Compounds Other anions Iron(III) fluoride Iron(III) bromide Other cations Iron(II) chloride Manganese(II) chloride Cobalt(II) chloride Ruthenium(III) chloride Related coagulants Iron(II) sulfate Polyaluminium chloride Except where noted otherwise, data are given for materials in their standard state (at 25... Aluminium hydroxide, Al(OH)3, is the most stable form of aluminium in normal conditions. ... Camelford (Cornish: Ryskammel) is a town in Cornwall, England, United Kingdom. ... A polymer (from Greek: πολυ, polu, many; and μέρος, meros, part) is a substance composed of molecules with large molecular mass composed of repeating structural units, or monomers, connected by covalent chemical bonds. ...

Sedimentation

Water exiting the flocculation basin may enter the sedimentation basin, also called a clarifier or settling basin. It is a large tank with slow flow, allowing floc to settle to the bottom. The sedimentation basin is best located close to the flocculation basin so the transit between does not permit settlement or floc break up. Sedimentation basins can be in the shape of a rectangle, where water flows from end to end, or circular where flow is from the centre outward. Sedimentation basin outflow is typically over a weir so only a thin top layer - furthest from the sediment - exits.The amount of floc that settles out of the water is dependent on the time the water spends in the basin and the depth of the basin. The retention time of the water must therefore be balanced against the cost of a larger basin. The minimum clarifier retention time is normally 4 hours. A deep basin will allow more floc to settle out than a shallow basin. This is because large particles settle faster than smaller ones, so large particles bump into and integrate smaller particles as they settle. In effect, large particles sweep vertically though the basin and clean out smaller particles on their way to the bottom.
As particles settle to the bottom of the basin a layer of sludge is formed on the floor of the tank. This layer of sludge must be removed and treated. The amount of sludge that is generated is significant, often 3%-5% of the total volume of water that is treated. The cost of treating and disposing of the sludge can be a significant part of the operating cost of a water treatment plant. The tank may be equipped with mechanical cleaning devices that continually clean the bottom of the tank or the tank can be taken out of service when the bottom needs to be cleaned. A settling basin, settling pond or decant pond is a place where very fine particles from water are removed by means of gravity. ... The bridge and weir mechanism at Sturminster Newton on the River Stour, Dorset. ...


Filtration

After separating most floc, the water is filtered as the final step to remove remaining suspended particles and unsettled floc. The most common type of filter is a rapid sand filter. Water moves vertically through sand which often has a layer of activated carbon or anthracite coal above the sand. The top layer removes organic compounds, which contribute to taste and odour. The space between sand particles is larger than the smallest suspended particles, so simple filtration is not enough. Most particles pass through surface layers but are trapped in pore spaces or adhere to sand particles. Effective filtration extends into the depth of the filter. This property of the filter is key to its operation: if the top layer of sand were to block all the particles, the filter would quickly clog.
To clean the filter, water is passed quickly upward through the filter, opposite the normal direction (called backflushing or backwashing) to remove embedded particles. Prior to this, compressed air may be blown up through the bottom of the filter to break up the compacted filter media to aid the backwashing process; this is known as air scouring. This contaminated water can be disposed of, along with the sludge from the sedimentation basin, or it can be recycled by mixing with the raw water entering the plant.
Some water treatment plants employ pressure filters. These work on the same principle as rapid gravity filters, differing in that the filter medium is enclosed in a steel vessel and the water is forced through it under pressure. Activated carbon Activated carbon, also called activated charcoal or activated coal, is a general term which covers carbon material mostly derived from charcoal. ... Anthracite coal Anthracite (Greek Ανθρακίτης, literally a form of coal, from Anthrax [Άνθραξ], coal) is a hard, compact variety of mineral coal that has a high luster. ...


Advantages:

Filters out much smaller particles than paper and sand filters can.
Filters out virtually all particles larger than their specified pore sizes.
They are quite thin and so liquids flow through them fairly rapidly.
They are reasonably strong and so can withstand pressure differences across them of typically 2-5 atmospheres.
They can be cleaned (back flushed) and reused.

Membrane filters are widely used for filtering both drinking water and sewage (for reuse). For drinking water, membrane filters can remove virtually all particles larger than 0.2 um--including Giardia and cryptosporidium. Membrane filters are an effective form of tertiary treatment when it is desired to reuse the water for industry, for limited domestic purposes, or before discharging the water into a river that is used by towns further downstream. They are widely used in industry, particularly for beverage preparation (including bottled water). However no filtration can remove substances that are actually dissolved in the water such as phosphorus, nitrates and heavy metal ions.


Slow sand filters

Slow sand filters may be used where there is sufficient land and space as the water must be passed very slowly through the filters. These filters rely on biological treatment processes for their action rather than physical filtration. The filters are carefully constructed using graded layers of sand with the coarsest sand, along with some gravel, at the bottom and finest sand at the top. Drains at the base convey treated water away for disinfection. Filtration depends on the development of a thin biological layer, called the zoogleal layer or Schmutzdecke, on the surface of the filter. An effective slow sand filter may remain in service for many weeks or even months if the pre-treatment is well designed and produces water with a very low available nutrient level which physical methods of treatment rarely achieve. Very low nutrient levels allow water to be safely sent through distribution system with very low disinfectant levels thereby reducing consumer irritation over offensive levels of chlorine and chlorine by-products. Slow sand filters are not backwashed; they are maintained by having the top layer of sand scraped off when flow is eventually obstructed by biological growth.[citation needed] Slow sand filters are used in water purification for treating raw water to produce a potable product. ... Schmutzdecke (German, grime or filth cover, sometimes incorrectly spelt Schmutzedecke) is a complex biological layer formed on the surface of slow sand filter beds. ...


A specific 'large-scale' form of slow sand filter is the process of bank filtration, in which natural sediments in a riverbank are used to provide a first stage of contaminant filtration. While typically not sufficiently clean enough to be used directly for drinking water, the water gained from the associated extraction wells is much less problematic than river water taken directly from the major streams where bank filtration is often used.


Lava filters

Lava filters are similar to sand filters and may also only be used where there is sufficient land and space. Like sand filters, the filters rely on biological treatment processes for their action rather than physical filtration. Unlike slow sand filters however, they are constructed out of 2 layers of lava pebbles and a top layer of nutrient-free soil (only at the plant roots). On top, water-purifying plants (as Iris pseudacorus and Sparganium erectum) are placed. Usually, around 1/4 of the dimension of lavastone is required to purify the water and just like slow sand filters, a series of herringbone drains are placed (with lava filters these are placed at the bottom layer). [1] Binomial name Iris pseudacorus L. The iris bearing the Latin name Iris pseudacorus is known by the common names yellow iris, yellow flag, and bastard fleur de lys. ... Species About 20 species; see text Sparganium (Bur-reed) is a genus of flowering plants, containing about 20 species in temperate regions of both the Northern and Southern Hemispheres. ...


Ultrafiltration

Ultrafiltration membranes are a relatively new development; they use polymer film with chemically formed microscopic pores that can be used in place of granular media to filter water effectively without coagulants. The type of membrane media determines how much pressure is needed to drive the water through and what sizes of micro-organisms can be filtered out. Ultrafiltration (UF) is a variety of membrane filtration in which hydrostatic pressure forces a liquid against a semipermeable membrane. ... An artificial membrane, also called a synthetic membrane, is a membrane prepared for separation tasks in laboratory and industry. ...


Other mechanical and biological techniques

See also: Greywater
See also: Ecological sanitation

In addition to the many techniques used in large-scale water treatment, several small-scale, less (or non)-polluting techniques are also being used to treat polluted water. These techniques include those based on mechanical and biological processes. An overview: Greywater, sometimes spelled graywater, grey water or gray water and also known as sullage, is non-industrial wastewater generated from domestic processes such as washing dishes, laundry and bathing. ... Ecological sanitation, also known as ecosan, is a modern alternative to conventional sanitation techniques. ... Biofiltration is a pollution control technique using living material to filter or chemically process pollutants. ...

In order to purify the water adequately, several of these systems are usually combined to work as a whole. Combination of the systems is done in two to three stages, namely primary and secondary purification. Sometimes tertiary purification is also added. A sand filter is a basic tool water purification. ... Note: Ultraviolet is also the name of a 1998 UK television miniseries about vampires. ... Biofiltration is a pollution control technique using living material to filter or chemically process pollutants. ... // A constructed wetland is an artificial marsh or swamp, created for anthropogenic discharge such as wastewater, stormwater runoff or sewage treatment, and as habitat for wildlife, or for land reclamation after mining or other disturbance. ... A treatment pond is a small lake-sized body of water designed to treat fouled water by anaerobic bacteria. ... Green Wall at Queens University, Kingston, Ontario, Canada A living wall is a vertical garden. ... Activated sludge is a process in sewage treatment in which air or oxygen is forced into sewage liquor to develop a biological floc which reduces the organic content of the sewage. ...


Disinfection

Disinfection is accomplished both by filtering out harmful microbes and also by adding disinfectant chemicals in the last step in purifying drinking water. Water is disinfected to kill any pathogens which pass through the filters. Possible pathogens include viruses, bacteria, including Escherichia coli, Campylobacter and Shigella, and protozoans, including G. lamblia and other cryptosporidia. In most developed countries, public water supplies are required to maintain a residual disinfecting agent throughout the distribution system, in which water may remain for days before reaching the consumer. Following the introduction of any chemical disinfecting agent, the water is usually held in temporary storage - often called a contact tank or clear well to allow the disinfecting action to complete. A pathogen (literally birth of pain from the Greek παθογένεια) is a biological agent that can cause disease to its host. ... Stop editing pages god ... Phyla Actinobacteria Aquificae Chlamydiae Bacteroidetes/Chlorobi Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Lentisphaerae Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Verrucomicrobia Bacteria (singular: bacterium) are unicellular microorganisms. ... E. coli redirects here. ... Species C. fetus C. jejuni Campylobacter is a genus of Gram-negative bacteria. ... Species S. boydii S. dysenteriae S. flexneri S. sonnei This article is about the bacteria. ... Protozoa (in Greek protos = first and zoon = animal) are single-celled creatures with nuclei that show some characteristics usually associated with animals, most notably mobility and heterotrophy. ... Binomial name (Kunstler, 1882) Giardia lamblia (synonymous with Lamblia intestinalis and Giardia duodenalis) is a flagellated protozoan parasite that colonises and reproduces in the small intestine, causing giardiasis. ... Species Cryptosporidium bailey Cryptosporidium meleagridis Cryptosporidium muris Cryptosporidium parvum Cryptosporidium serpentis Cryptosporidium is a protozoan pathogen of the Phylum Apicomplexa and causes a diarrheal illness called cryptosporidiosis. ...

  1. Chlorination- The most common disinfection method is some form of chlorine or its compounds such as chloramine or chlorine dioxide. Chlorine is a strong oxidant that rapidly kills many harmful micro-organisms. Because chlorine is a toxic gas, there is a danger of a release associated with its use. This problem is avoided by the use of sodium hypochlorite, which is a relatively inexpensive solution that releases free chlorine when dissolved in water. Chlorine solutions can be generated on site by electrolyzing common salt solutions. A solid form , calcium hypochlorite exists that releases chlorine on contact with water. Handling the solid, however, requires greater routine human contact through opening bags and pouring than the use of gas cylinders or bleach which are more easily automated. The generation of liquid sodium hypochlorite is both inexpensive and safer than the use of gas or solid chlorine. All forms of chlorine are widely used despite their respective drawbacks. One drawback is that chlorine from any source reacts with natural organic compounds in the water to form potentially harmful chemical by-products trihalomethanes (THMs) and haloacetic acids (HAAs), both of which are carcinogenic in large quantities and regulated by the United States Environmental Protection Agency (EPA). The formation of THMs and haloacetic acids may be minimized by effective removal of as many organics from the water as possible prior to chlorine addition. Although chlorine is effective in killing bacteria, it has limited effectiveness against protozoans that form cysts in water (Giardia lamblia and Cryptosporidium, both of which are pathogenic).
  2. Chlorine dioxide is another faster-acting disinfectant. It is, however, relatively rarely used, because in some circumstances it may create excessive amounts of chlorite, which is a by-product regulated to low allowable levels in the United States. Chlorine dioxide is made in water and added/used in water to avoid gas handling problems; chlorine dioxide gas accumulations may spontaneously detonate.
  3. Chloramines are another chlorine-based disinfectant. Although chloramine is not as strong of an oxidant it does provide a longer-lasting residual than free chlorine, and it won't form THMs or haloacetic acids. It is possible to convert chlorine to chloramine by adding ammonia to the water after addition of chlorine: The chlorine and ammonia react to form chloramine. Water distribution systems disinfected with chloramines may experience nitrification, wherein ammonia is used a nutrient for bacterial growth, with nitrates being generated as a byproduct.
  4. Ozone (O3) is a relatively unstable molecule "free radical" of oxygen which readily gives up one atom of oxygen providing a powerful oxidising agent which is toxic to most waterborne organisms. It is a very strong, broad spectrum disinfectant that is widely used in Europe. It is an effective method to inactivate harmful protozoans that form cysts. It also works well against almost all other pathogens. Ozone is made by passing oxygen through ultraviolet light or a "cold" electrical discharge. To use ozone as a disinfectant, it must be created on-site and added to the water by bubble contact. Some of the advantages of ozone include the production of relatively fewer dangerous by-products (in comparison to chlorination) and the lack of taste and odour produced by ozonation. Although fewer by-products are formed by ozonation, it has been discovered that the use of ozone produces a small amount of the suspected carcinogen bromate, although little bromine should be present in treated water. Another of the main disadvantages of ozone is that it leaves no disinfectant residual in the water. Ozone has been used in drinking water plants since 1906 where the first industrial ozonation plant was built in Nice, France. The U.S. Food and Drug Administration has accepted ozone as being safe; and it is applied as an anti-microbiological agent for the treatment, storage, and processing of foods.
  5. UV radiation (light) is very effective at inactivating cysts, as long as the water has a low level of colour so the UV can pass through without being absorbed. The main disadvantage to the use of UV radiation is that, like ozone treatment, it leaves no residual disinfectant in the water. Because neither ozone nor UV radiation leaves a residual disinfectant in the water, it is sometimes necessary to add a residual disinfectant after they are used. This is often done through the addition of chloramines, discussed above as a primary disinfectant. When used in this manner, chloramines provide an effective residual disinfectant with very little of the negative aspects of chlorination.
  6. Hydrogen peroxide is another disinfectant. It works similar to ozone, yet activators as formic acid are to be added to increase the working of this chemical substance. It also has the disadvantages that it is slow-working, phytotoxic in high dosage, and decreases the PH of the water it purifies.

Chlorination is the process of adding the element chlorine to water as a method of water purification to make it fit for human consumption as drinking water. ... General Name, symbol, number chlorine, Cl, 17 Chemical series nonmetals Group, period, block 17, 3, p Appearance yellowish green Standard atomic weight 35. ... Chloramine (monochloramine) is chemical compound with the formula NH2Cl. ... Chlorine dioxide is a chemical compound with the formula ClO2. ... Sodium hypochlorite is a chemical compound with the formula NaClO. Sodium hypochlorite solution, commonly known as bleach, is frequently used as a disinfectant and as a bleaching agent. ... Trihalomethanes (THMs) are chemical compounds in which three of the four hydrogen atoms of methane (CH4) are replaced by halogen atoms. ... Haloacetic acids are carboxylic acids in which a halogen atom takes the place of a hydrogen atom in acetic acid. ... In pathology, a carcinogen is any substance or agent that promotes cancer. ... EPA redirects here. ... Nitrogen cycle Nitrification is the biological oxidation of ammonia with oxygen into nitrite followed by the oxidation of these nitrites into nitrates. ... For other uses, see Ozone (disambiguation). ... Chlorination is the process of adding the element chlorine to water as a method of water purification to make it fit for human consumption as drinking water. ... The bromate ion is BrO3−. A bromate is a compound that contains this group. ... Bromo redirects here. ... This article is about the French city. ... Note: Ultraviolet is also the name of a 1998 UK television miniseries about vampires. ... Hydrogen peroxide (H2O2) is a very pale blue liquid which appears colorless in a dilute solution, slightly more viscous than water. ... Formic acid (systematically called methanoic acid) is the simplest carboxylic acid. ...

Additional treatment options

  1. Fluoridation: in many areas fluoride is added to water for the purpose of preventing tooth decay. This process is referred to as water fluoridation. Fluoride is usually added after the disinfection process. In the United States, fluoridation is usually accomplished by the addition of hexafluorosilicic acid, which decomposes in water, yielding fluoride ions.
  2. Water conditioning: This is a method of reducing the effects of hard water. Hardness salts are deposited in water systems subject to heating because the decomposition of bicarbonate ions creates carbonate ions which crystalise out of the saturated solution of calcium or magnesium carbonate. Water with high concentrations of hardness salts can be treated with soda ash (sodium carbonate) which precipitates out the excess salts, through the common-ion effect, producing calcium carbonate of very high purity. The precipitated calcium carbonate is traditionally sold to the manufacturers of toothpaste. Several other methods of industrial and residential water treatment are claimed (without general scientific acceptance) to include the use of magnetic or/and electrical fields reducing the effects of hard water.[citation needed]
  3. Plumbosolvency reduction: In areas with naturally acidic waters of low conductivity (i.e surface rainfall in upland mountains of igneous rocks), the water may be capable of dissolving lead from any lead pipes that it is carried in. The addition of small quantities of phosphate ion and increasing the pH slightly both assist in greatly reducing plumbo-solvency by creating insoluble lead salts on the inner surfaces of the pipes.
  4. Radium Removal: Some groundwater sources contain radium, a radioactive chemical element. Typical sources include many groundwater sources north of the Illinois River in Illinois. Radium can be removed by ion exchange, or by water conditioning. The back flush or sludge that is produced is, however, a low-level radioactive waste.
  5. Fluoride Removal: Although fluoride is added to water in many areas, some areas of the world have excessive levels of natural fluoride in the source water. Excessive levels can be toxic or cause undesirable cosmetic effects such as staining of teeth. One method of reducing fluoride levels is through treatment with activated alumina.

Fluoride is the ionic form of fluorine. ... Types of teeth Molars are used for grinding up foods Carnassials are used for slicing food. ... Water fluoridation is the practice of adding fluoride compounds to water with the intended purpose of reducing tooth decay in the general population. ... Dihydrogen hexafluorosilicate is commonly used for fluoridate in the United States. ... Sodium carbonate (also known as washing soda or soda ash), Na2CO3, is a sodium salt of carbonic acid. ... The common-ion effect is a term used to describe the effect on a solution of two dissolved solutes that contain the same ion. ... Modern toothpaste gel Toothpaste is a paste or gel dentifrice used to clean and improve the aesthetic appearance and health of teeth. ... Plumbosolvency is the ability of a solvent, notably water, to dissolve lead. ... Igneous rocks are formed when molten rock (magma) cools and solidifies, with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks. ... General Name, Symbol, Number lead, Pb, 82 Chemical series Post-transition metals or poor metals Group, Period, Block 14, 6, p Appearance bluish gray Standard atomic weight 207. ... A phosphate, in inorganic chemistry, is a salt of phosphoric acid. ... For other uses, see PH (disambiguation). ... For other uses, see Radium (disambiguation). ... This article is about the river in the U.S. state of Illinois. ... This article is about the U.S. State. ... Radioactive wastes are waste types containing radioactive chemical elements that do not have a practical purpose. ... In high concentrations, as with almost all substances, fluoride compounds are toxic. ... Activated alumina is a ceramic compound used as a desiccant (to keep things dry by absorbing water from the air) and as a filter of fluoride, arsenic and selenium in drinking water. ...

Other water purification techniques

Other popular methods for purifying water, especially for local private supplies are listed below. In some countries some of these methods are also used for large scale municipal supplies. Particularly important are distillation (de-salination of seawater) and reverse osmosis.

  1. Boiling: Water is heated hot enough and long enough to inactivate or kill micro-organisms that normally live in water at room temperature. Near sea level, a vigorous rolling boil for at least one minute is sufficient. At high altitudes (greater than two kilometers or 5000 feet) three minutes is recommended.[3] In areas where the water is "hard" (that is, containing significant dissolved calcium salts), boiling decomposes the bicarbonate ions, resulting in partial precipitation as calcium carbonate. This is the "fur" that builds up on kettle elements, etc., in hard water areas. With the exception of calcium, boiling does not remove solutes of higher boiling point than water and in fact increases their concentration (due to some water being lost as vapour). Boiling does not leave a residual disinfectant in the water. Therefore, water that has been boiled and then stored for any length of time may have acquired new pathogens.
  2. Granular Activated Carbon filtering: GAC, a form of activated carbon with a high surface area, absorbs many compounds including many toxic compounds. Water passing through activated carbon is commonly used in municipal regions with organic contamination, taste or odors. Many household water filters and fish tanks use activated carbon filters to further purify the water. Household filters for drinking water sometimes contain silver to release silver ions which have an anti-bacterial effect.
  3. Distillation involves boiling the water to produce water vapour. The vapour contacts a cool surface where it condenses as a liquid. Because the solutes are not normally vaporised, they remain in the boiling solution. Even distillation does not completely purify water, because of contaminants with similar boiling points and droplets of unvaporised liquid carried with the steam. However, 99.9% pure water can be obtained by distillation. Distillation does not confer any residual disinfectant and the distillation apparatus may be the ideal place to harbor Legionnaires' disease.
  4. Reverse osmosis: Mechanical pressure is applied to an impure solution to force pure water through a semi-permeable membrane. Reverse osmosis is theoretically the most thorough method of large scale water purification available, although perfect semi-permeable membranes are difficult to create. Unless membranes are well-maintained, algae and other life forms can colonize the membranes.
  5. Ion exchange: Most common ion exchange systems use a zeolite resin bed to replace unwanted Ca2+ and Mg2+ ions with benign (soap friendly) Na+ or K+ ions. This is the common water softener.
  6. Electrodeionization: Water is passed between a positive electrode and a negative electrode. Ion selective membranes allow the positive ions to separate from the water toward the negative electrode and the negative ions toward the positive electrode. High purity deionized water results. The water is usually passed through a reverse osmosis unit first to remove non-ionic organic contaminants.
  7. The use of iron in removing arsenic from water. See Arsenic contamination of groundwater.
  8. Direct contact membrane distillation (DCMD). Applicable to desalination. Heated seawater is passed along the surface of a hydrophobic polymer membrane. Evaporated water passes from the hot side through pores in the membrane into a stream of cold pure water on the other side. The difference in vapour pressure between the hot and cold side helps to push water molecules through.
  9. Gas hydrate crystals centrifuge method. If carbon dioxide gas is mixed with contaminated water at high pressure and low temperature, gas hydrate crystals will contain only clean water. This is because the water molecules bind to the gas molecules at molecule level. The contaminated water is in liquid form. A centrifuge may be used to separate the crystals and the concentrated contaminated water.

Boiling, a type of phase transition, is the rapid vaporization of a liquid, which typically occurs when a liquid is heated to its boiling point, the temperature at which the vapor pressure of the liquid is equal to the pressure exerted on the liquid by the surrounding atmospheric pressure. ... A microorganism or microbe is an organism that is so small that it is microscopic (invisible to the naked eye). ... For baking soda, see Sodium bicarbonate In inorganic chemistry, a bicarbonate (IUPAC-recommended nomenclature: hydrogencarbonate) is an intermediate form in the deprotonation of carbonic acid. ... Calcium carbonate is a chemical compound, with the chemical formula CaCO3. ... Binomial name (Lour. ... Activated carbon Activated carbon, also called activated charcoal or activated coal, is a general term which covers carbon material mostly derived from charcoal. ... Activated carbon Activated carbon, also called activated charcoal or activated coal, is a general term which covers carbon material mostly derived from charcoal. ... This article is about the chemical element. ... Laboratory distillation set-up: 1: Heat source 2: Still pot 3: Still head 4: Thermometer/Boiling point temperature 5: Condenser 6: Cooling water in 7: Cooling water out 8: Distillate/receiving flask 9: Vacuum/gas inlet 10: Still receiver 11: Heat control 12: Stirrer speed control 13: Stirrer/heat plate... Vapor (US English) or vapour (British English) is the gaseous state of matter. ... Legionellosis is an infectious disease caused by bacteria belonging to the genus Legionella. ... Reverse osmosis (RO) is a separation process that uses pressure to force a solution through a membrane that retains the solute on one side and allows the pure solvent to pass to the other side. ... A semipermeable membrane is a membrane which will allow certain molecules to pass through it by diffusion (sometimes facilitated diffusion). The rate of passage depends on the pressure, concentration and temperature of the molecules (or solutes) on either side, as well as the permeability of the membrane to each kind. ... For the programming language, see algae (programming language). ... Ion exchange is defined as an exchange of ions between two electrolytes. ... Zeolite The micro-porous molecular structure of a zeolite, ZSM-5 Zeolites (Greek, zein, to boil; lithos, a stone) are minerals that have a micro-porous structure. ... For other uses, see Calcium (disambiguation). ... General Name, symbol, number magnesium, Mg, 12 Chemical series alkaline earth metals Group, period, block 2, 3, s Appearance silvery white solid at room temp Standard atomic weight 24. ... This article is about the electrically charged particle. ... For sodium in the diet, see Salt. ... General Name, symbol, number potassium, K, 19 Chemical series alkali metals Group, period, block 1, 4, s Appearance silvery white Standard atomic weight 39. ... For other uses, see Electrode (disambiguation). ... This article or section should include material from Net flux A membrane is a thin, typically planar structure or material that separates two environments. ... Reverse osmosis (RO) is a separation process that uses pressure to force a solution through a membrane that retains the solute on one side and allows the pure solvent to pass to the other side. ... Arsenic contamination of groundwater is a natural occurring high concentration of arsenic in deeper levels of groundwater, which became a high-profile problem in recent years due to the use of deep tubewells for water supply in the Ganges Delta, causing serious arsenic poisoning to large numbers of people. ... In chemistry, hydrophobic or lipophilic species, or hydrophobes, tend to be electrically neutral and nonpolar, and thus prefer other neutral and nonpolar solvents or molecular environments. ... A polymer (from Greek: πολυ, polu, many; and μέρος, meros, part) is a substance composed of molecules with large molecular mass composed of repeating structural units, or monomers, connected by covalent chemical bonds. ...

Portable water purification

Portable techniques for purifying water are used for hiking, camping etc. or for use in rural areas or emergency situations. Common techniques include boiling, disinfection with tablets or ultra-filtration using a small hand pump. Portable water purification is used to treat water in remote or rural locations, or in emergency settings, to make it safe for drinking purposes. ...


In addition to this "portable water purification" may also include residential, commercial or industrial water treatment systems that are regenerated off site (by others). These systems are most commonly used for deionization in industrial applications or softening for residential applications. Also known as Service Deionization (SDI), industrial companies use these portable systems for a variety of reasons. Most commonly, the user has a small application and can not justify the expense of having regenerant chemicals such as sulfuric or hydrochloric acid and sodium hydroxide on site for safety and or manpower reasons. There may be waste water discharge limitations that make owning and operating an in-house deionizer (also known as a demineralizer) too expensive in comparison to the outsourcing of regeneration.


In residential applications a water treatment company delivers portable softener exchange tanks to a household. These softener tanks treat all or some of the water entering the household and remove hardness minerals. They are exchanged on a pre-determined schedule so the household has softened water on a on a continual basis. Although not as cost effective as owning a water softener, portable water softeners require no maintenance by the home owner; furthermore there is no discharge of brine to septic or municipal waste treatment systems.


Water purification for hydrogen production

For the small scale production of hydrogen, water purifiers are installed to prevent formation of minerals on the surface of the electrodes and to remove organics and chlorine from utility water. First, the water passes through a 20 micrometre interference (mesh or screen filter) filter to remove sand and dust particles, then a charcoal filter using activated carbon to remove organics and chlorine and, finally, a de-ionizing filter to remove metallic ions. Testing can be done before and after the filter to verify the proper removal of barium, calcium, potassium, magnesium, sodium and silicon. Hydrogen production is commonly completed from hydrocarbon fossil fuels via a chemical path. ... For other uses, see Mesh (disambiguation). ... A screen filter is a type of filter utilizing a rigid or flexible screen to separate sand and other fine particles out of water for irrigation or other applications. ... Activated carbon from a water filter used for Carbon filtering in powder and block form Carbon filtering is a method of filtering that uses a piece of activated carbon to remove contaminants and impurities, utilizing chemical adsorption. ... Activated carbon Activated carbon, also called activated charcoal or activated coal, is a general term which covers carbon material mostly derived from charcoal. ... General Name, symbol, number chlorine, Cl, 17 Chemical series nonmetals Group, period, block 17, 3, p Appearance yellowish green Standard atomic weight 35. ... Deionized water (DI water or de-ionized water; also spelled deionised water, see spelling differences) is water that lacks ions, such as cations from sodium, calcium, iron, copper and anions such as chloride and bromide. ... For other uses, see Barium (disambiguation). ... For other uses, see Calcium (disambiguation). ... General Name, symbol, number potassium, K, 19 Chemical series alkali metals Group, period, block 1, 4, s Appearance silvery white Standard atomic weight 39. ... General Name, symbol, number magnesium, Mg, 12 Chemical series alkaline earth metals Group, period, block 2, 3, s Appearance silvery white solid at room temp Standard atomic weight 24. ... For sodium in the diet, see Salt. ... Not to be confused with Silicone. ...


Another method that is used is reverse osmosis. Reverse osmosis (RO) is a separation process that uses pressure to force a solution through a membrane that retains the solute on one side and allows the pure solvent to pass to the other side. ...


Safety and controversies

There has been controversy over the fluoridation of water since the 1930s, when the benefits to dental health were first claimed. There is evidence that excessive concentrations of fluorides can make teeth, and bones, more brittle and easily damaged / broken. Fluoridation is banned in many countries. Water fluoridation controversy refers to the debate about the safety of the addition of fluoride to public water supplies. ...


Water supplies have sometimes been the subject of concerns over terrorism or actual terrorist threats. The following is a timeline of acts and failed attempts that can be considered non-state terrorism. ...


Accidents have also been known to happen. In April, 2007, the water supply of Spencer, Massachusetts became contaminated with excess sodium hydroxide (lye) when its treatment equipment malfunctioned. Spencer is a town located in Worcester County, Massachusetts. ... Sodium hydroxide (NaOH), also known as lye, caustic soda and (incorrectly, according to IUPAC nomenclature)[1] sodium hydrate, is a caustic metallic base. ...


References

  1. ^ Pictures and small overview of lavafilters (in dutch)
  2. ^ Overview of biological systems with pictures
  3. ^ US EPA emergency disinfection recommendations
  • Masters, Gilbert M. Introduction to Environmental Engineering. 2nd ed. Upper Saddle River, NJ: Prentice Hall, 1998.
  • United States EPA Ground and Drinking Water Homepage. EPA Ground and Drinking Water Homepage Visited 12/13/05
  • WIPO Patent: METHOD AND DEVICE FOR PURIFICATION OF AIR AND WATER Visited 06/22/08

See also

Wikimedia Commons has media related to:
Water_purification
Water Portal

Image File history File links Drinking_water. ... Aquatic toxicology is the study of the effects of manufactured chemicals and other anthropogenic and natural materials and activities on aquatic organisms at various levels of organization, from subcellular through individual organisms to communities and ecosystems (Rand, 1995). ... Brigadier General Carl Rogers Darnall, MD (25 December 1867, Weston, Texas, USA -18 January 1941, Walter Reed General Hospital, Washington, DC, USA) was a U.S. Army chemist and surgeon credited with originating the technique of liquid chlorination of drinking water. ... The following page consist of a list of waste water treatment technologies: Activated sludge Anaerobic digestion Anaerobic lagoon Cesspit Combined sewer overflow Composting toilet Constructed wetland Imhoff tank Floculation Reed bed Septic tank Sequencing batch reactor UASB Aerobic Granular Reactor This list is incomplete; you can help by expanding it. ... Ecological sanitation, also known as ecosan, is a modern alternative to conventional sanitation techniques. ... Greywater, sometimes spelled graywater, grey water or gray water and also known as sullage, is non-industrial wastewater generated from domestic processes such as washing dishes, laundry and bathing. ... Microfiltration is a filtration process which removes contaminants from a fluid or gas by passage through a microporous membrane. ... Portable water purification is used to treat water in remote or rural locations, or in emergency settings, to make it safe for drinking purposes. ... A treatment pond is a small lake-sized body of water designed to treat fouled water by anaerobic bacteria. ... E. Coli bacteria under magnification Sanitation is the hygienic disposal or recycling of waste, as well as the policy and practice of protecting health through hygienic measures. ... Sewage is the mainly liquid waste containing some solids produced by humans which typically consists of washing water, faeces, urine, laundry waste and other material which goes down drains and toilets from households and industry. ... Sewage treatment, or domestic wastewater treatment, is the process of removing contaminants from wastewater, both runoff and domestic. ... Water conservation refers to reducing use of fresh water, through technological or social methods. ... Recycled water is wastewater that has been recovered for potable or nonpotable use, such as reclaimed water. ... A water treatment plant in northern Portugal. ...

External links

Environmental technology or green technology is the application of the environmental sciences to conserve the natural environment and resources, and by curbing the negative impacts of human involvement. ... It has been suggested that this article or section be merged with Air Pollution#Control devices. ... Bio-energy redirects here. ... For other uses, see Birth control (disambiguation). ... Composting is the aerobic decomposition of biodegradable organic matter, producing compost. ... Conservation biology, or conservation ecology, is the science of analyzing and protecting Earths biological diversity. ... The conservation ethic is an ethic of resource use, allocation, exploitation, and protection. ... Ecoforestry is forestry that emphasizes holistic practices which strive to protect and restore ecosystems1 instead of traditional forestry that maximizes economic productivity. ... For battery powered passenger automobiles, see battery electric vehicle. ... For the physical concepts, see conservation of energy and energy efficiency. ... Higher electricity use per capita correlates with a higher score on the Human Development Index(1997). ... tytytrtyty This article is about energy efficiency as a ratio. ... Environmental design is the process of addressing environmental parameters when devising plans, programs, policies, buildings, or products. ... An Environmental Impact Statement (EIS) is an assessment of the likely influence a project may have on the environment. ... Envirnonmental preservation is the strict setting aside of natural resources to prevent the use or contact by humans or by human intervention. ... This article is about green building construction. ... Green computing is the study and practice of using computing resources efficiently. ... For other types of hybrid transportation, see Hybrid vehicle (disambiguation). ... This article or section is incomplete and may require expansion and/or cleanup. ... Industrial ecology is the shifting of industrial process from open loop systems, in which resource and capital investments move through the system to become waste, to a closed loop system where wastes become inputs for new processes. ... Industrial wastewater treatment covers the mechanisms and processes used to treat waters that have been contaminated in some way by mans industrial or commercial activities prior to its release into the environment or its re-use. ... Natural building involves a range of building systems and materials that place major emphasis on sustainability. ... The international recycling symbol. ... Renewable energy effectively utilizes natural resources such as sunlight, wind, tides and geothermal heat, which are naturally replenished. ... // Renewable energy development covers the advancement, capacity growth, and use of renewable energy sources by humans. ... Generally, remediation means providing a remedy, so environmental remediation deals with the removal of pollution or contaminants from environmental media such as soil, groundwater, sediment, or surface water for the general protection of human health and the environment or from a brownfield site intended for redevelopment. ... The following page contains a list of different forms of waste treatment Anaerobic digestion ArrowBio Composting Gasification Incineration In-vessel composting Landfill Mechanical biological treatment Mechanical heat treatment Plasma Pyrolysis Recycling Sewage treatment Tunnel composting UASB Windrow composting Categories: | ... Sustainable architecture applies techniques of sustainable design to architecture. ... This article is about a concept related to renewable energy, of which sustainable energy is a superset. ... Sustainable development is a pattern of resource use that aims to meet human needs while preserving the environment so that these needs can be met not only in the present, but in the indefinite future. ... The following page consist of a list of waste water treatment technologies: Activated sludge Anaerobic digestion Anaerobic lagoon Cesspit Combined sewer overflow Composting toilet Constructed wetland Imhoff tank Floculation Reed bed Septic tank Sequencing batch reactor UASB Aerobic Granular Reactor This list is incomplete; you can help by expanding it. ... For the company, see Waste Management, Inc. ...

  Results from FactBites:
 
Methods of Water Purification (2177 words)
Water treatment can be defined as any procedure or method used to alter the chemical composition or natural "behavior" of a water supply.
Municipal waters may be pH adjusted to a pH of approximately 7.5 to 8.0 to prevent corrosion of water pipes, particularly to prevent dissolution of lead into the water supply.
In the case of excessive alkalinity, the pH may be reduced by the addition of CO After the water is delivered from the utility or the well, there are many on-site options for further treatment to meet specific end-use requirements.
Water purification - Wikipedia, the free encyclopedia (4162 words)
Water purification is the removal of contaminants from raw water to produce drinking water that is pure enough for human consumption or for industrial use.
Water distribution systems disinfected with chloramines may experience nitrification, wherein ammonia is used a nitrogen source for bacterial growth, with nitrates being generated as a byproduct.
Water with high concentrations of hardness salts can be treated with soda ash (sodium carbonate) which precipitates out the excess salts, through the common ion effect, as calcium carbonate of very high purity.
  More results at FactBites »

 
 

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