Heat therapy, also called thermotherapy, is the application of heat to the body for pain relief and health. It can take the form of a hot cloth, hot water, ultrasound, heating pad, hydrocollator packs, whirlpool baths, cordless FIR heat therapy wrap, and many others. It can be beneficial to those with arthritis and stiff muscles and injuries to the deep tissue of the skin. Heat may be an effective self-care treatment for conditions like rheumatoid arthritis.^[1]

Heat therapy is most commonly used for rehabilitation purposes. The therapeutic effects of heat include increasing the extensibility of collagen tissues; decreasing joint stiffness; reducing pain; relieving muscle spasms; reducing inflammation, edema, and aids in the post acute phase of healing; and increasing blood flow. The increased blood flow to the affected area provides proteins, nutrients, and oxygen for better healing. ^[2]

History

Heat has been used for therapeutic purposes for thousands of years. Many ancient civilizations worshipped figures of the sun, such as the Egyptians, who worshipped the sun god Ra.

Application

Moist heat is more effective at warming tissues than dry heat because water transfers heat more quickly than air. This results in the perception that the tissue is heated more deeply, which increases the effect on muscles, joints, and soft tissue. Heat is typically applied by placing very warm, wet towels on the relevant body part.

The newest breed of heat therapy device such as "FIR Cordless Heat Therapy" such as the one developed by +Venture Heat combines the carbon fiber heater with cordless rechargeable Lithium battery and built into the specific body wrap (ie. shoulder wrap or back wrap) for a targeted heat therapy can be use as an alternative to the chemical or plugged-in heating pads.

Mechanism of action

Heat therapy creates higher superficial tissue temperatures, which aids the healing process in some conditions. Heat applied superficially to the skin directly increases the temperature of the skin and the tissue immediately underneath the skin. Muscle temperature increases through a reflexive effect on circulation and through conduction.

Another use is the treatment of infection and cancers by the use of heat. Cancer cells and many bacteria have poor mechanisms for adapting to and resisting the physiological stresses of heat, and are more vulnerable to heat-induced death than normal cells.

In plants

Thermotherapy may also be used in vine propagation to get rid of viroids (particles smaller than viruses) which may affect the new vine.

A water ionizer is an appliance that ionizes water. Ionized water is purported to be beneficial to human health and marketed with claims that it is an antioxidant which can slow aging and prevent disease.^[1] Others note that such claims contradict basic laws of chemistry and physiology.^[2]

Ionization

A water ionizer separates water into alkaline and acid fractions using a process known as electrolysis.^[3] It does this by exploiting the electric charge of the calcium and magnesium ions present in nearly all sources of drinking water. When a source of water lacks mineral ions, such as distilled water, or has been filtered by reverse osmosis, water ionization has no effect.

Uses

Some research suggests that alkaline reduced water may be useful in scavenging free radicals in the laboratory setting.^[4] Tests on in vitro lymphocytes suggest that reduced water can prevent hydrogen peroxide-induced damage to DNA, RNA and certain proteins.^[5] However, drinking ionized water would not be expected to alter the body's pH, and there is no evidence of any claims made by manufacturers that drinking ionized water will have a noticeable effect on the body.^[2]

Electrolyzed water has been used by the food industry to sanitize food products; though effective in bacterial solutions, it was found less useful when sanitizing utensils, surfaces and food products.^[6][7] Acidic electrolyzed water (pH 2.3–2.6) may have use as a seed surface disinfectant or contact bactericide.^[8]

Medical equipment is designed to aid in the diagnosis, monitoring or treatment of medical conditions. These devices are usually designed with rigorous safety standards. The medical equipment is included in the category Medical technology.

There are several basic types:

• Diagnostic equipment includes medical imaging machines, used to aid in diagnosis. Examples are ultrasound and MRI machines, PET and CT scanners, and x-ray machines.
• Therapeutic equipment includes infusion pumps, medical lasers and LASIK surgical machines.
• Life support equipment is used maintain a patient's bodily function. These include medical ventilators, anaesthetic machines, heart-lung machines, ECMO, and dialysis machines.
• Medical monitors allow medical staff to measure a patient's medical state. Monitors may measure patient vital signs and other parameters including ECG, EEG, blood pressure, and dissolved gases in the blood.
• Medical laboratory equipment automates or helps analyze blood, urine and genes.
• Diagnostic Medical Equipment may also be used in the home for certain purposes, e.g. for the control of diabetes mellitus

A biomedical equipment technician (BMET) is a vital component of the healthcare delivery system. Employed primarily by hospitals, BMETs are the people responsible for maintaining a facility's medical equipment.

Inventions

• 1895, X-ray, by Wilhelm Röntgen
• 1903, electrocardiograph, by Willem Einthoven
• 1956, endoscope, by Basil Hirschowitz
• 1958, ultrasound scan, by Ian Donald
• 1973, CT (CAT) scan, by Godfrey Hounsfield and Allan Cormack
• 1982, artificial heart, by Robert Jarvik

Source

Running Press Cyclopedia, second edition.

Notable medical equipment companies

• Boston Scientific
• Beckman Coulter
• Dräger
• GE Healthcare
• Getinge Group
• Heine Optotechnik
• Johnson & Johnson
• MAQUET
• Medtronic
• Mindray
• Philips
• St. Jude Medical
• Siemens AG

See also

• Medical technology
• Medical device
• Durable medical equipment
• Eucomed
• Home medical equipment
• Surgical instruments
• Medical test
• Medical grade silicone

Amethyst is a violet variety of quartz often used in jewelry. The name comes from the Ancient Greek ἀ a- ("not") and μέθυστος methustos ("intoxicated"), a reference to the belief that the stone protected its owner from drunkenness; the ancient Greeks and Romans wore amethyst and made drinking vessels of it in the belief that it would prevent intoxication.

Chemistry

Amethyst is the violet variety of quartz; its chemical formula is SiO₂.

In the 20th century, the color of amethyst was attributed to the presence of manganese. However, since it is capable of being greatly altered and even discharged by heat, the color was believed by some authorities to be from an organic source. Ferric thiocyanate was suggested, and sulfur was said to have been detected in the mineral.

More recent work has shown that amethyst's coloration is due to ferric iron impurities.^[1] Further study has shown a complex interplay of iron and aluminium is responsible for the color.^[2]

On exposure to heat, amethyst generally becomes yellow, and much of the citrine, cairngorm, or yellow quartz of jewelry is said to be merely "burnt amethyst". Veins of amethystine quartz are apt to lose their color on the exposed outcrop^{[citation needed]}.

Synthetic amethyst is made to imitate the best quality amethyst. Its chemical and physical properties are so similar to that of natural amethyst that it can not be differentiated with absolute certainty without advanced gemological testing (which is often cost-prohibitive). There is one test based on "Brazil law twinning" (a form of quartz twinning where right and left hand quartz structures are combined in a single crystal^[3]) which can be used to identify synthetic amethyst rather easily. In theory however it is possible to create this material synthetically as well, but this type is not available in large quantities in the market.^[4]

Composition

Amethyst is composed of an irregular superposition of alternate lamellae of right-handed and left-handed quartz. It has been shown that this structure may be due to mechanical stresses.

Because it has a hardness of seven on the Mohs scale, amethyst is suitable for use in jewelry.

Hue and tone

Amethyst occurs in primary hues from a light pinkish violet to a deep purple. Amethyst may exhibit one or both secondary hues, red and blue. The ideal grade is called "Deep Siberian" and has a primary purple hue of around 75–80 percent, 15–20 percent blue and (depending on the light source) red secondary hues.^[4]

History

Amethyst was used as a gemstone by the ancient Egyptians and was largely employed in antiquity for intaglio engraved gems. ^[5]

The Greeks believed amethyst gems could prevent intoxication, while medieval European soldiers wore amethyst amulets as protection in battle. ^[6] Beads of amethyst were found in Anglo-Saxon graves in England.^{[citation needed]}

A huge geode, or "amethyst-grotto", from near Santa Cruz in southern Brazil was exhibited at the Düsseldorf, Germany Exhibition of 1902.

Amethyst is the traditional birthstone for February.

Mythology

The Greek word "amethystos" may be translated as "not drunken", from Greek a-, not + methustos, intoxicated^[7]. Amethyst was considered to be a strong antidote against drunkenness, which is why wine goblets were often carved from it. In Greek mythology, Dionysus, the god of intoxication,and wine, was pursuing a maiden named Amethystos, who refused his affections. Amethystos prayed to the gods to remain chaste, which the goddess Artemis granted and transformed her into a white stone. Humbled by Amethystos's desire to remain chaste, Dionysus poured wine over the stone as an offering, dyeing the crystals purple.

Variations of the story include that Dionysus had been insulted by a mortal and swore to slay the next mortal who crossed his path, creating fierce tigers to carry out his wrath. The mortal turned out to be a beautiful young woman, Amethystos, who was on her way to pay tribute to Artemis(the hunter goddess). Her life is spared by Artemis, who transformed the maiden into a statue of pure crystalline quartz to protect her from the brutal claws. Dionysus wept tears of wine in remorse for his action at the sight of the beautiful statue. The god's tears then stained the quartz purple.^[8] Another variation involves the titan Rhea presenting Dionysus with the amethyst stone to preserve the wine-drinker's sanity.^[9]

Geographic distribution

Amethyst is produced in abundance from the state of Minas Gerais in Brazil where it occurs in large geodes within volcanic rocks. It is also found and mined in South Korea. The largest opencast amethyst vein in the world is in Maissau, Lower Austria. Many of the hollow agates of Brazil and Uruguay contain a crop of amethyst crystals in the interior. Much fine amethyst comes from Russia, especially from near Mursinka in the Ekaterinburg district, where it occurs in drusy cavities in granitic rocks. Many localities in India yield amethyst. One of the largest global amethyst producers is Zambia with an annual production of about 1,000 t.

Amethyst occurs at many localities in the United States. Among these may be mentioned: the Mazatzal Mountain region in Gila and Maricopa Counties, Arizona; Amethyst Mountain, Texas; Yellowstone National Park; Delaware County, Pennsylvania; Haywood County, North Carolina; Deer Hill and Stow, Maine and in the Lake Superior region. Amethyst is relatively common in Ontario, and in various locations throughout Nova Scotia. The largest amethyst mine in North America is located in Thunder Bay, Ontario.^[10] .

Value

Up to 18th century amethyst was included in the cardinal, or most valuable, gemstones (along with diamond, sapphire, ruby, and emerald). However since the discovery of extensive deposits in locations such as Brazil it has lost most of its value.

Collectors look for depth of color, possibly with red flashes if cut conventionally. ^[11]. The highest grade amethyst (called "Deep Russian") is exceptionally rare and therefore its value is dependent on the demand of collectors when one is found. It is however still orders of magnitude lower than the highest grade sapphires or rubies (Padparadscha sapphire or "pigeon's blood" ruby).^[4]

Medical equipment is designed to aid in the diagnosis, monitoring or treatment of medical conditions. These devices are usually designed with rigorous safety standards. The medical equipment is included in the category Medical technology.

There are several basic types:

• Diagnostic equipment includes medical imaging machines, used to aid in diagnosis. Examples are ultrasound and MRI machines, PET and CT scanners, and x-ray machines.
• Therapeutic equipment includes infusion pumps, medical lasers and LASIK surgical machines.
• Life support equipment is used maintain a patient's bodily function. These include medical ventilators, anaesthetic machines, heart-lung machines, ECMO, and dialysis machines.
• Medical monitors allow medical staff to measure a patient's medical state. Monitors may measure patient vital signs and other parameters including ECG, EEG, blood pressure, and dissolved gases in the blood.
• Medical laboratory equipment automates or helps analyze blood, urine and genes.
• Diagnostic Medical Equipment may also be used in the home for certain purposes, e.g. for the control of diabetes mellitus

A biomedical equipment technician (BMET) is a vital component of the healthcare delivery system. Employed primarily by hospitals, BMETs are the people responsible for maintaining a facility's medical equipment.

Inventions

• 1895, X-ray, by Wilhelm Röntgen
• 1903, electrocardiograph, by Willem Einthoven
• 1956, endoscope, by Basil Hirschowitz
• 1958, ultrasound scan, by Ian Donald
• 1973, CT (CAT) scan, by Godfrey Hounsfield and Allan Cormack
• 1982, artificial heart, by Robert Jarvik

Source

Running Press Cyclopedia, second edition.

Notable medical equipment companies

• Boston Scientific
• Beckman Coulter
• Dräger
• GE Healthcare
• Getinge Group
• Heine Optotechnik
• Johnson & Johnson
• MAQUET
• Medtronic
• Mindray
• Philips
• St. Jude Medical
• Siemens AG

See also

• Medical technology
• Medical device
• Durable medical equipment
• Eucomed
• Home medical equipment
• Surgical instruments
• Medical test
• Medical grade silicone

     Amethyst healing is an art and practice, done on a metaphysical level that has been re-discovered because of the power of the earth's energies that have been absorbed by these sacred objects. In turn, they inherit vital healing powers for many types of ailments. Amethyst has come to be known as a power crystal with prolific healing powers that can be characterized as purifying, pacifying and transitional.

     Amethyst has the ability to transform lower energies into higher and acts as a healer at all levels of mind, body, and spirit. The healing powers of Amethyst date as far back as the Greeks who believed that Amethyst protected a person from the intoxicating effects of alcohol.

     There are many physical uses which the healing powers of Amethyst are a remedy. As an elixir, Amethyst can be used to treat tooth aches, skeletal discomforts, posture and other bone and joint-related sickness (such as arthritis). Amethyst also cures problems within the stomach and digestive tract, heart and hearing disorders. Amethyst has been known to treat various types of blood disease, and balancing blood sugar.

     As a healing stone or crystal Amethyst is used to treat and heal problems involving the central nervous system, and is a treatment for both convulsions and neuralgia, and contains sobering and calming qualities. This stone is commonly associated with peace. Amethyst soothes those who have engaged in constant rigorous mental activity. Amethyst has been deemed as "natures tranqualizer" by many healers because of its effectiveness in relaxing not only the mind, but also the nervous system. Amethyst is also known for protecting the mind from psychic attacks, and transforming negative energy into that of positive and tranquil tenacity.

     Amethyst is identified as a crystal that functions favorably in clearing certain types of blockage, and in aligning the chakras. By transforming energies on all levels, amethyst also has the ability to balance and stabalize energies located within certain areas. Amethyst is related to and found to heal and align ailments.

     Amethyst healing is an art and practice, done on a metaphysical level that has been re-discovered because of the power of the earth's energies that have been absorbed by these sacred objects. In turn, they inherit vital healing powers for many types of ailments. Amethyst has come to be known as a power crystal with prolific healing powers that can be characterized as purifying, pacifying and transitional.

     Amethyst has the ability to transform lower energies into higher and acts as a healer at all levels of mind, body, and spirit. The healing powers of Amethyst date as far back as the Greeks who believed that Amethyst protected a person from the intoxicating effects of alcohol.

     There are many physical uses which the healing powers of Amethyst are a remedy. As an elixir, Amethyst can be used to treat tooth aches, skeletal discomforts, posture and other bone and joint-related sickness (such as arthritis). Amethyst also cures problems within the stomach and digestive tract, heart and hearing disorders. Amethyst has been known to treat various types of blood disease, and balancing blood sugar.

     As a healing stone or crystal Amethyst is used to treat and heal problems involving the central nervous system, and is a treatment for both convulsions and neuralgia, and contains sobering and calming qualities. This stone is commonly associated with peace. Amethyst soothes those who have engaged in constant rigorous mental activity. Amethyst has been deemed as "natures tranqualizer" by many healers because of its effectiveness in relaxing not only the mind, but also the nervous system. Amethyst is also known for protecting the mind from psychic attacks, and transforming negative energy into that of positive and tranquil tenacity.

     Amethyst is identified as a crystal that functions favorably in clearing certain types of blockage, and in aligning the chakras. By transforming energies on all levels, amethyst also has the ability to balance and stabalize energies located within certain areas. Amethyst is related to and found to heal and align ailments.

A water supply system or water supply network is a system of engineered hydrologic and hydraulic components which provide water supply. A water supply system typically includes:

1. The watershed or geographic area that collects the water (see water purification - sources of drinking water);
2. A raw (untreated) water collection point (above or below ground) where the water accumulates, such as a lake, a river, or groundwater from an underground aquifer. Untreated drinking water (usually water being transferred to the water purification facilities) may be transferred using uncovered ground-level aqueducts, covered tunnels or underground water pipes.
3. Water purification facilities. Treated water is transferred using water pipes (usually underground).
4. Water storage facilities such as reservoirs, water tanks, or watertowers. Smaller water systems may store the water in cisterns or pressure vessels. (Tall buildings may also need to store water locally in pressure vessels in order for the water to reach the upper floors.)
5. Additional water pressurizing components such as pumping stations may need to be situated at the outlet of underground or above ground reservoirs or cisterns (if gravity flow is unfeasible)
6. A pipe network for distribution of water to the consumers (which may be private houses or industrial, commercial or institution establishments) and other usage points (such as fire hydrants)
7. Connections to the sewers (underground pipes, or aboveground ditches in some developing countries) are generally found downstream of the water consumers, but the sewer system is considered to be a separate system, rather than part of the water supply system

Water abstraction and raw water transfer

Raw water (untreated) is collected from a surface water source (such as an intake on a lake or a river) or from a groundwater source (such as a water well drawing from an underground aquifer) within the watershed that provides the water resource.

Shallow dams and reservoirs are susceptible to outbreaks of toxic algae, especially if the water is warmed by a hot sun. The bacteria grow from stormwater runoff carrying fertilizer into the river where it acts as a nutrient for the algae. Such outbreaks render the water unfit for human consumption.

The raw water is transferred to the water purification facilities using uncovered aqueducts, covered tunnels or underground water pipes.

Water treatment

Virtually all large systems must treat the water; a fact that is tightly regulated by global, state and federal agencies, such as the World Health Organization (WHO) or the United States Environmental Protection Agency (EPA). Water treatment must occur before the product reaches the consumer and afterwards (when it is discharged again). Water purification usually occurs close to the final delivery points to reduce pumping costs and the chances of the water becoming contaminated after treatment.

Traditional surface water treatment plants generally consists of three steps: clarification, filtration and disinfection. Clarification refers to the separation of particles (dirt, organic matter, etc.) from the water stream. Chemical addition (i.e. alum, ferric chloride) destabilizes the particle charges and prepares them for clarification either by settling or floating out of the water stream. Sand, anthracite or activated carbon filters refine the water stream, removing smaller particulate matter. While other methods of disinfection exist, the preferred method is via chlorine addition. Chlorine effectively kills bacteria and most viruses and maintains a residual to protect the water supply through the supply network.

Water distribution network

The product, delivered to the point of consumption, is called fresh water if it receives little or no treatment, or drinking water if the treatment achieves the water quality standards required for human consumption.

Once treated, chlorine is added to the water and it is distributed by the local supply network. Today, water supply systems are typically constructed of plastic, ferrous, or concrete circular pipe. However, other "pipe" shapes and material may be used, such as square or rectangular concrete boxes, arched brick pipe, or wood. Near the end point, the network of pipes through which the water is delivered is often referred to as the water mains.

The energy that the system needs to deliver the water is called pressure. That energy is transferred to the water, therefore becoming water pressure, in a number of ways: by a pump, by gravity feed from a water source (such as a water tower) at a higher elevation, or by compressed air. ^[1]

The water is often transferred from a water reserve such as a large communal reservoir before being transported to a more pressurised reserve as a watertower.

In small domestic systems, the water may be pressurised by a pressure vessel or even by an underground cistern (the latter however does need additional pressurizing). This eliminates the need of a watertower or any other heightened water reserve to supply the water pressure.

These systems are usually owned and maintained by local governments, such as cities, or other public entities, but are occasionally operated by a commercial enterprise (see water privatization). Water supply networks are part of the master planning of communities, counties, and municipalities. Their planning and design requires the expertise of city planners and civil engineers, who must consider many factors, such as location, current demand, future growth, leakage, pressure, pipe size, pressure loss, fire fighting flows, etc. — using pipe network analysis and other tools. [[Construction]comparable sewage systems, was one of the great engineering advances that made urbanization possible. Improvement in the quality of the water has been one of the great advances in public health.

As water passes through the distribution system, the water quality can degrade by chemical reactions and biological processes. Corrosion of metal pipe materials in the distribution system can cause the release of metals into the water with undesirable aesthetic and health effects. Release of iron from unlined iron pipes can result in customer reports of "red water" at the tap . Release of copper from copper pipes can result in customer reports of "blue water" and/or a metallic taste. Release of lead can occur from the solder used to join copper pipe together or from brass fixtures. Copper and lead levels at the consumer's tap are regulated to protect consumer health.

Utilities will often adjust the chemistry of the water before distribution to minimize its corrosiveness. The simplest adjustment involves control of pH and alkalinity to produce a water that tends to passivate corrosion by depositing a layer of calcium carbonate. Corrosion inhibitors are often added to reduce release of metals into the water. Common corrosion inhibitors added to the water are phosphates and silicates.

Maintenance of a biologically safe drinking water is another goal in water distribution. Typically, a chlorine based disinfectant, such as sodium hypochlorite or monochloramine is added to the water as it leaves the treatment plant. Booster stations can be placed within the distribution system to ensure that all areas of the distribution system have adequate sustained levels of disinfection.

Topologies of water distribution networks

Like electric power lines, roads, and microwave radio networks, water systems may have a loop or branch network topology, or a combination of both. The piping networks are circular or rectangular. If any one section of water distribution main fails or needs repair, that section can be isolated without disrupting all users on the network.

Most systems are divided into zones. Factors determining the extent or size of a zone can include hydraulics, telemetry systems, history, and population density. Sometimes systems are designed for a specific area then are modified to accommodate development. Terrain affects hydraulics and some forms of telemetry. While each zone may operate as a stand-alone system, there is usually some arrangement to interconnect zones in order to manage equipment failures or system failures.

Water network maintenance

Water supply networks usually represent the majority of assets of a water utility. Systematic documentation of maintenance works using a Computerized Maintenance Management System is a key to a successful operation of a water utility.

[edit] Note on connections to the sewer system

Connections to the sewers are generally found downstream of the water consumers.

However, a hook-up to the sewerage system is unnecessary if the sewage is properly treated on-site. In line with the principle of ecological sanitation, rather than relying on water to transport feces and urine, compost toilets can be used which eliminate this extra water pollution (comprising some 30% of the water requirements).

See also

• Aqueduct
• Domestic water system
• Goldfields Water Supply Scheme
• Hardy Cross
• Hosepipe ban
• Hydrology
• Infrastructure
• Plumbing
• Tap water
• Water supply in Hong Kong
• Water
  • Water pipes
  • Water Meters
    • Automatic meter reading
  • Backflow prevention device
  • Fire hydrant
  • Strainers
  • Valve
  • Water tower
  • Water quality
  • Water resources
  • Water supply

The New Age (also referred to as the New Age movement, New Age spirituality, and Cosmic Humanism) is a decentralized Western social and spiritual movement that seeks "Universal Truth" and the attainment of the highest individual human potential. It includes aspects of Occultism, astrology, esotericism, metaphysics, alternative medicine, music, collectivism, sustainability, and nature. New Age spirituality is characterized by an individual approach to spiritual practices and philosophies, and the rejection of religious doctrine and dogma.

The New Age movement includes elements of older spiritual and religious traditions ranging from atheism and monotheism through classical pantheism, naturalistic pantheism, and panentheism to polytheism combined with science and Gaia philosophy: particularly archaeoastronomy, astronomy, ecology, environmentalism, the Gaia hypothesis, psychology, and physics. New Age practices and philosophies sometimes draw inspiration from major world religions: Buddhism, Chinese folk religion, Christianity, Hinduism, Islam, Judaism; with particularly strong influences from East Asian religions, Gnosticism, Neopaganism, New Thought, Spiritualism, Theosophy, Universalism, and Western esotericism.^[2] Additional terms for the movement include All is One^[3] and Mind-Body-Spirit.^[1]

The modern New Age movement emerged in a distinct form in the late 1960s and early 1970s, although its roots can be traced back to the 19th and early 20th centuries. It gained momentum in the 1980s and strengthened with the Harmonic Convergence event in 1987. Diverse individuals from around the world practice New Age spirituality.^{[citation needed]}

Movement

Origins

The term New Age was used as early as 1809 by William Blake who described a belief in a spiritual and artistic "New Age" in his preface to Milton: a Poem.

Some of the New Age movement's constituent elements appeared initially in 19th century metaphysical movements: Spiritualism, Theosophy, and New Thought; also, alternative medicine movements chiropractic and naturopathy.^[1][3] These movements in turn have roots in Transcendentalism, Mesmerism, Swedenborgianism, and various earlier Western esoteric or occult traditions, such as the hermetic arts of astrology, magic, alchemy, and Kabbalah. The term New Age was used in this context in Madame Blavatsky's book The Secret Doctrine, published in 1888.^[4]

A weekly journal of Christian liberalism and socialism titled The New Age was published as early as 1894;^[5] it was sold to a group of socialist writers headed by Alfred Richard Orage and Holbrook Jackson in 1907. Other historical personalities were involved: H. G. Wells, George Bernard Shaw, and William Butler Yeats; the magazine became a forum for politics, literature, and the arts.^[6][7] Between 1908 and 1914, it was instrumental in pioneering the British avant-garde from vorticism to imagism. After 1914, publisher Orage met P. D. Ouspensky, a follower of G. I. Gurdjieff, and began correspondence with Harry Houdini, becoming less interested in literature and art, with an increased focus on mysticism and other spiritual topics; the magazine was sold in 1921. According to Brown University, The New Age "... helped to shape modernism in literature and the arts from 1907 to 1922."^[8]

Development

Popularisation behind these ideas has roots in the work of early 20th century writers such as D. H. Lawrence and William Butler Yeats. In the early to middle 1900s, American mystic, theologian, and founder of the Association for Research and Enlightenment Edgar Cayce was a seminal influence on what later would be termed the New Age movement; he was known in particular for the practice some refer to as channeling.^[9] Former Theosophist Rudolf Steiner and his Anthroposophical Movement are a major influence. Neo-Theosophist Alice Bailey published the book Discipleship in the New Age (1944), which used the term New Age in reference to the transition from the Astrological Age of Pisces to Aquarius. While claims of racial bias in the writings of Rudolf Steiner and Alice Bailey were made,^[10] Steiner emphasized racial equality as a principle central to anthroposophical thought and humanity's progress.^[11][12] Any racial elements from these influences have not remained part of the Anthroposophical Society as contemporary adherents of the society have either not adopted or repudiated these beliefs.^[13][14] Another early usage of the term, was by the American artist, mystic, and philosopher Walter Russell, who spoke of "... this New Age philosophy of the spiritual re-awakening of man ..." in his essay "Power Through Knowledge", which was also published in 1944.

Carl Gustav Jung was an early articulator of the concept of the Age of Aquarius.^[15] In a letter to H. G. Baynes, dated 12 August 1940, he wrote in a passage concerning the destruction of the temple of Karnak by an earthquake in 26 BC: "1940 is the year when we approach the meridian of the first star in Aquarius. It is the premonitory earthquake of the New Age."^[16]

Postmodern

The subculture that would later be called New Age already existed in the early 1970s, based on and adopting ideas originally present in the counterculture of the 1960s. The Findhorn Foundation – an intentional community near Findhorn, Moray, Scotland founded in 1962 – played an instrumental role during the early growth period of the New Age movement; it continues to operate the Findhorn Ecovillage.

Widespread use of the term New Age began in the mid 1970s (reflected in the title of monthly periodical New Age Journal) and probably influenced several thousand small metaphysical book and gift stores that increasingly defined themselves as "New Age bookstores".^[17][18] As a result of the large-scale activities surrounding the Harmonic Convergence in the mid 1980s – the term was further popularised by the American mass media to describe the alternative spiritual subculture – including practices such as meditation, channeling, crystal healing, astral projection, psychic experience, holistic health, simple living, and environmentalism; or belief in phenomena such as Earth mysteries, ancient astronauts, extraterrestrial life, unidentified flying objects, crop circles, and reincarnation. A range of New Age publications appeared by the late 1980s such as Psychic Guide (later renamed Body, Mind & Spirit), Yoga Journal, New Age Voice, New Age Retailer, and NAPRA ReView by the New Age Publishers and Retailers Alliance.

There were several key moments in raising public awareness of this subculture: the publication of Linda Goodman's best selling astrology books Sun Signs (1968) and Love Signs (1978); Hair: The American Tribal Love-Rock Musical (1967) with the opening song "Aquarius" and its memorable line "This is the dawning of the Age of Aquarius" [emphasis added]; the broadcast of Shirley MacLaine's television mini-series Out on a Limb (1987); and the Harmonic Convergence (1987) organized by José Argüelles in Sedona, Arizona. Also influential were the claims of channelers Jane Roberts (the Seth Material) and J. Z. Knight (Ramtha), as well as revealed writings A Course in Miracles (1976) by Helen Schucman, The Celestine Prophecy (1993) by James Redfield, and Conversations with God (1995) by Neale Donald Walsch. Relevant works also include the writings of Eckhart Tolle, Barbara Marx Hubbard, Marianne Williamson, Deepak Chopra, John Holland, Gary Zukav, and Wayne Dyer; also, The Secret (2006) by Rhonda Byrne, which was based on the writings of Esther Hicks and Jerry Hicks.

In chemistry, an alkali (from Arabic: Al-Qaly القلي, القالي ) is a basic, ionic salt of an alkali metal or alkaline earth metal element. Alkalis are best known for being bases that dissolve in water. Bases are compounds with a pH greater than 7. The adjective alkaline is commonly used in English as a synonym for base, especially for soluble bases. This broad use of the term is likely to have come about because alkalis were the first bases known to obey the Arrhenius definition of a base and are still among the more common bases. Since Brønsted-Lowry acid-base theory, the term alkali in chemistry is normally restricted to those salts containing alkali and alkaline earth metal elements.

Etymology

The word "alkali" is derived from Arabic al qalīy = the calcined ashes, referring to the original source of alkaline substance. Ashes were used in conjunction with animal fat to produce soap, a process known as saponification.

Common properties

Alkalis are all Arrhenius bases, which form hydroxide ions (OH^-) when dissolved in water. Common properties of alkaline aqueous solutions include:

• Moderately-concentrated solutions (over 10^−3 M) have a pH of 7.1 or greater. This means that they will turn phenolphthalein from colorless to pink.
• Concentrated solutions are caustic (causing chemical burns).
• Alkaline solutions are slippery or soapy to the touch, due to the saponification of the fatty acids on the surface of the skin.
• Alkalis are normally water soluble, although some like barium carbonate are only soluble when reacting with an acidic aqueous solution.
• Acids and alkalis are measured on a pH scale
• Alkalis are commonly found in household cleaners and toothpaste

Confusion between alkali and base

The terms "base" and "alkali" are often used interchangeably, particularly outside of a scientific context, but they do not have the same meaning. While all alkaline solutions are basic, not all bases are alkaline. The following are common mistakes:

• The phrase "measuring the alkalinity of soil" is incorrect since the property measured is actually the pH (base property).
• Calling bases that are not alkalis, such as ammonia, alkaline (ammonia is a base but not an alkali).

Also, not all salts formed by alkali metals are alkaline; this designation applies only to those salts that are basic. And while most electropositive metal oxides are basic, only the soluble alkali metal and alkaline earth metal oxides can be correctly called alkalis.

This definition of an alkali as a basic salt of an alkali metal or alkaline earth metal is the most common, based on dictionary definitions [1][2], however conflicting definitions of the term alkali do exist. These include:

• Any base that is water-soluble and forms hydroxide ions [3][4]. In chemistry, this is more accurately called an Arrhenius base.

• The solution of a base in water [5]. This would be an Arrhenius base in solution.

• Name given by chemists to an important group of subtances, the behaviour of bases the main alkali are 1,the hydroxides potassium 2,

Salts

Most basic salts are alkali salts, of which common examples are:

• sodium hydroxide (often called "caustic soda")
• potassium hydroxide (commonly called "caustic potash")
• lye (generic term, for either of the previous two, or even for a mixture)
• calcium carbonate (sometimes called "free lime")
• magnesium hydroxide is an example of an atypical alkali since it has low solubility in water (although the dissolved portion is considered a strong base due to complete dissociation of its ions).

Alkaline soil

Soil with a pH value higher than 7.3 is normally referred to as alkaline. This soil property can occur naturally, due to the presence of alkali salts. Although some plants do prefer slightly basic soil (including vegetables like cabbage and fodder like buffalograss), most plants prefer a mildly acidic soil (pH between 6.0 and 6.8), and alkaline soils can cause problems.

Lakes

In alkali lakes (a type of salt lake), evaporation concentrates the naturally-occurring alkali salts, often forming a crust of mildly-basic salt across a large area.

Examples of alkali lakes:

• Redberry Lake, Saskatchewan, Canada.
• Tramping Lake, Saskatchewan, Canada.
• Mono lake, California, United States
• Summer Lake, Oregon, United States
• Alkali Lake, British Columbia and the adjoining reserves of the Alkali Lake Indian Band are named for a local Alkali Lake, which got its name from a large patch of alkali on the hillside above the lake, which is not itself alkali,^[1] although there are many in the Cariboo district and adjoining regions of the British Columbia Interior.

A water supply system or water supply network is a system of engineered hydrologic and hydraulic components which provide water supply. A water supply system typically includes:

1. The watershed or geographic area that collects the water (see water purification - sources of drinking water);
2. A raw (untreated) water collection point (above or below ground) where the water accumulates, such as a lake, a river, or groundwater from an underground aquifer. Untreated drinking water (usually water being transferred to the water purification facilities) may be transferred using uncovered ground-level aqueducts, covered tunnels or underground water pipes.
3. Water purification facilities. Treated water is transferred using water pipes (usually underground).
4. Water storage facilities such as reservoirs, water tanks, or watertowers. Smaller water systems may store the water in cisterns or pressure vessels. (Tall buildings may also need to store water locally in pressure vessels in order for the water to reach the upper floors.)
5. Additional water pressurizing components such as pumping stations may need to be situated at the outlet of underground or above ground reservoirs or cisterns (if gravity flow is unfeasible)
6. A pipe network for distribution of water to the consumers (which may be private houses or industrial, commercial or institution establishments) and other usage points (such as fire hydrants)
7. Connections to the sewers (underground pipes, or aboveground ditches in some developing countries) are generally found downstream of the water consumers, but the sewer system is considered to be a separate system, rather than part of the water supply system

Water abstraction and raw water transfer

Raw water (untreated) is collected from a surface water source (such as an intake on a lake or a river) or from a groundwater source (such as a water well drawing from an underground aquifer) within the watershed that provides the water resource.

Shallow dams and reservoirs are susceptible to outbreaks of toxic algae, especially if the water is warmed by a hot sun. The bacteria grow from stormwater runoff carrying fertilizer into the river where it acts as a nutrient for the algae. Such outbreaks render the water unfit for human consumption.

The raw water is transferred to the water purification facilities using uncovered aqueducts, covered tunnels or underground water pipes.

Water treatment

Virtually all large systems must treat the water; a fact that is tightly regulated by global, state and federal agencies, such as the World Health Organization (WHO) or the United States Environmental Protection Agency (EPA). Water treatment must occur before the product reaches the consumer and afterwards (when it is discharged again). Water purification usually occurs close to the final delivery points to reduce pumping costs and the chances of the water becoming contaminated after treatment.

Traditional surface water treatment plants generally consists of three steps: clarification, filtration and disinfection. Clarification refers to the separation of particles (dirt, organic matter, etc.) from the water stream. Chemical addition (i.e. alum, ferric chloride) destabilizes the particle charges and prepares them for clarification either by settling or floating out of the water stream. Sand, anthracite or activated carbon filters refine the water stream, removing smaller particulate matter. While other methods of disinfection exist, the preferred method is via chlorine addition. Chlorine effectively kills bacteria and most viruses and maintains a residual to protect the water supply through the supply network.

Water distribution network

The product, delivered to the point of consumption, is called fresh water if it receives little or no treatment, or drinking water if the treatment achieves the water quality standards required for human consumption.

Once treated, chlorine is added to the water and it is distributed by the local supply network. Today, water supply systems are typically constructed of plastic, ferrous, or concrete circular pipe. However, other "pipe" shapes and material may be used, such as square or rectangular concrete boxes, arched brick pipe, or wood. Near the end point, the network of pipes through which the water is delivered is often referred to as the water mains.

The energy that the system needs to deliver the water is called pressure. That energy is transferred to the water, therefore becoming water pressure, in a number of ways: by a pump, by gravity feed from a water source (such as a water tower) at a higher elevation, or by compressed air. ^[1]

The water is often transferred from a water reserve such as a large communal reservoir before being transported to a more pressurised reserve as a watertower.

In small domestic systems, the water may be pressurised by a pressure vessel or even by an underground cistern (the latter however does need additional pressurizing). This eliminates the need of a watertower or any other heightened water reserve to supply the water pressure.

These systems are usually owned and maintained by local governments, such as cities, or other public entities, but are occasionally operated by a commercial enterprise (see water privatization). Water supply networks are part of the master planning of communities, counties, and municipalities. Their planning and design requires the expertise of city planners and civil engineers, who must consider many factors, such as location, current demand, future growth, leakage, pressure, pipe size, pressure loss, fire fighting flows, etc. — using pipe network analysis and other tools. [[Construction]comparable sewage systems, was one of the great engineering advances that made urbanization possible. Improvement in the quality of the water has been one of the great advances in public health.

As water passes through the distribution system, the water quality can degrade by chemical reactions and biological processes. Corrosion of metal pipe materials in the distribution system can cause the release of metals into the water with undesirable aesthetic and health effects. Release of iron from unlined iron pipes can result in customer reports of "red water" at the tap . Release of copper from copper pipes can result in customer reports of "blue water" and/or a metallic taste. Release of lead can occur from the solder used to join copper pipe together or from brass fixtures. Copper and lead levels at the consumer's tap are regulated to protect consumer health.

Utilities will often adjust the chemistry of the water before distribution to minimize its corrosiveness. The simplest adjustment involves control of pH and alkalinity to produce a water that tends to passivate corrosion by depositing a layer of calcium carbonate. Corrosion inhibitors are often added to reduce release of metals into the water. Common corrosion inhibitors added to the water are phosphates and silicates.

Maintenance of a biologically safe drinking water is another goal in water distribution. Typically, a chlorine based disinfectant, such as sodium hypochlorite or monochloramine is added to the water as it leaves the treatment plant. Booster stations can be placed within the distribution system to ensure that all areas of the distribution system have adequate sustained levels of disinfection.

Topologies of water distribution networks

Like electric power lines, roads, and microwave radio networks, water systems may have a loop or branch network topology, or a combination of both. The piping networks are circular or rectangular. If any one section of water distribution main fails or needs repair, that section can be isolated without disrupting all users on the network.

Most systems are divided into zones. Factors determining the extent or size of a zone can include hydraulics, telemetry systems, history, and population density. Sometimes systems are designed for a specific area then are modified to accommodate development. Terrain affects hydraulics and some forms of telemetry. While each zone may operate as a stand-alone system, there is usually some arrangement to interconnect zones in order to manage equipment failures or system failures.

Water network maintenance

Water supply networks usually represent the majority of assets of a water utility. Systematic documentation of maintenance works using a Computerized Maintenance Management System is a key to a successful operation of a water utility.

[edit] Note on connections to the sewer system

Connections to the sewers are generally found downstream of the water consumers.

However, a hook-up to the sewerage system is unnecessary if the sewage is properly treated on-site. In line with the principle of ecological sanitation, rather than relying on water to transport feces and urine, compost toilets can be used which eliminate this extra water pollution (comprising some 30% of the water requirements).

See also

• Aqueduct
• Domestic water system
• Goldfields Water Supply Scheme
• Hardy Cross
• Hosepipe ban
• Hydrology
• Infrastructure
• Plumbing
• Tap water
• Water supply in Hong Kong
• Water
  • Water pipes
  • Water Meters
    • Automatic meter reading
  • Backflow prevention device
  • Fire hydrant
  • Strainers
  • Valve
  • Water tower
  • Water quality
  • Water resources
  • Water supply

The New Age (also referred to as the New Age movement, New Age spirituality, and Cosmic Humanism) is a decentralized Western social and spiritual movement that seeks "Universal Truth" and the attainment of the highest individual human potential. It includes aspects of Occultism, astrology, esotericism, metaphysics, alternative medicine, music, collectivism, sustainability, and nature. New Age spirituality is characterized by an individual approach to spiritual practices and philosophies, and the rejection of religious doctrine and dogma.

The New Age movement includes elements of older spiritual and religious traditions ranging from atheism and monotheism through classical pantheism, naturalistic pantheism, and panentheism to polytheism combined with science and Gaia philosophy: particularly archaeoastronomy, astronomy, ecology, environmentalism, the Gaia hypothesis, psychology, and physics. New Age practices and philosophies sometimes draw inspiration from major world religions: Buddhism, Chinese folk religion, Christianity, Hinduism, Islam, Judaism; with particularly strong influences from East Asian religions, Gnosticism, Neopaganism, New Thought, Spiritualism, Theosophy, Universalism, and Western esotericism.^[2] Additional terms for the movement include All is One^[3] and Mind-Body-Spirit.^[1]

The modern New Age movement emerged in a distinct form in the late 1960s and early 1970s, although its roots can be traced back to the 19th and early 20th centuries. It gained momentum in the 1980s and strengthened with the Harmonic Convergence event in 1987. Diverse individuals from around the world practice New Age spirituality.^{[citation needed]}

Movement

Origins

The term New Age was used as early as 1809 by William Blake who described a belief in a spiritual and artistic "New Age" in his preface to Milton: a Poem.

Some of the New Age movement's constituent elements appeared initially in 19th century metaphysical movements: Spiritualism, Theosophy, and New Thought; also, alternative medicine movements chiropractic and naturopathy.^[1][3] These movements in turn have roots in Transcendentalism, Mesmerism, Swedenborgianism, and various earlier Western esoteric or occult traditions, such as the hermetic arts of astrology, magic, alchemy, and Kabbalah. The term New Age was used in this context in Madame Blavatsky's book The Secret Doctrine, published in 1888.^[4]

A weekly journal of Christian liberalism and socialism titled The New Age was published as early as 1894;^[5] it was sold to a group of socialist writers headed by Alfred Richard Orage and Holbrook Jackson in 1907. Other historical personalities were involved: H. G. Wells, George Bernard Shaw, and William Butler Yeats; the magazine became a forum for politics, literature, and the arts.^[6][7] Between 1908 and 1914, it was instrumental in pioneering the British avant-garde from vorticism to imagism. After 1914, publisher Orage met P. D. Ouspensky, a follower of G. I. Gurdjieff, and began correspondence with Harry Houdini, becoming less interested in literature and art, with an increased focus on mysticism and other spiritual topics; the magazine was sold in 1921. According to Brown University, The New Age "... helped to shape modernism in literature and the arts from 1907 to 1922."^[8]

Development

Popularisation behind these ideas has roots in the work of early 20th century writers such as D. H. Lawrence and William Butler Yeats. In the early to middle 1900s, American mystic, theologian, and founder of the Association for Research and Enlightenment Edgar Cayce was a seminal influence on what later would be termed the New Age movement; he was known in particular for the practice some refer to as channeling.^[9] Former Theosophist Rudolf Steiner and his Anthroposophical Movement are a major influence. Neo-Theosophist Alice Bailey published the book Discipleship in the New Age (1944), which used the term New Age in reference to the transition from the Astrological Age of Pisces to Aquarius. While claims of racial bias in the writings of Rudolf Steiner and Alice Bailey were made,^[10] Steiner emphasized racial equality as a principle central to anthroposophical thought and humanity's progress.^[11][12] Any racial elements from these influences have not remained part of the Anthroposophical Society as contemporary adherents of the society have either not adopted or repudiated these beliefs.^[13][14] Another early usage of the term, was by the American artist, mystic, and philosopher Walter Russell, who spoke of "... this New Age philosophy of the spiritual re-awakening of man ..." in his essay "Power Through Knowledge", which was also published in 1944.

Carl Gustav Jung was an early articulator of the concept of the Age of Aquarius.^[15] In a letter to H. G. Baynes, dated 12 August 1940, he wrote in a passage concerning the destruction of the temple of Karnak by an earthquake in 26 BC: "1940 is the year when we approach the meridian of the first star in Aquarius. It is the premonitory earthquake of the New Age."^[16]

Postmodern

The subculture that would later be called New Age already existed in the early 1970s, based on and adopting ideas originally present in the counterculture of the 1960s. The Findhorn Foundation – an intentional community near Findhorn, Moray, Scotland founded in 1962 – played an instrumental role during the early growth period of the New Age movement; it continues to operate the Findhorn Ecovillage.

Widespread use of the term New Age began in the mid 1970s (reflected in the title of monthly periodical New Age Journal) and probably influenced several thousand small metaphysical book and gift stores that increasingly defined themselves as "New Age bookstores".^[17][18] As a result of the large-scale activities surrounding the Harmonic Convergence in the mid 1980s – the term was further popularised by the American mass media to describe the alternative spiritual subculture – including practices such as meditation, channeling, crystal healing, astral projection, psychic experience, holistic health, simple living, and environmentalism; or belief in phenomena such as Earth mysteries, ancient astronauts, extraterrestrial life, unidentified flying objects, crop circles, and reincarnation. A range of New Age publications appeared by the late 1980s such as Psychic Guide (later renamed Body, Mind & Spirit), Yoga Journal, New Age Voice, New Age Retailer, and NAPRA ReView by the New Age Publishers and Retailers Alliance.

There were several key moments in raising public awareness of this subculture: the publication of Linda Goodman's best selling astrology books Sun Signs (1968) and Love Signs (1978); Hair: The American Tribal Love-Rock Musical (1967) with the opening song "Aquarius" and its memorable line "This is the dawning of the Age of Aquarius" [emphasis added]; the broadcast of Shirley MacLaine's television mini-series Out on a Limb (1987); and the Harmonic Convergence (1987) organized by José Argüelles in Sedona, Arizona. Also influential were the claims of channelers Jane Roberts (the Seth Material) and J. Z. Knight (Ramtha), as well as revealed writings A Course in Miracles (1976) by Helen Schucman, The Celestine Prophecy (1993) by James Redfield, and Conversations with God (1995) by Neale Donald Walsch. Relevant works also include the writings of Eckhart Tolle, Barbara Marx Hubbard, Marianne Williamson, Deepak Chopra, John Holland, Gary Zukav, and Wayne Dyer; also, The Secret (2006) by Rhonda Byrne, which was based on the writings of Esther Hicks and Jerry Hicks.

The New Age (also referred to as the New Age movement, New Age spirituality, and Cosmic Humanism) is a decentralized Western social and spiritual movement that seeks "Universal Truth" and the attainment of the highest individual human potential. It includes aspects of Occultism, astrology, esotericism, metaphysics, alternative medicine, music, collectivism, sustainability, and nature. New Age spirituality is characterized by an individual approach to spiritual practices and philosophies, and the rejection of religious doctrine and dogma.

The New Age movement includes elements of older spiritual and religious traditions ranging from atheism and monotheism through classical pantheism, naturalistic pantheism, and panentheism to polytheism combined with science and Gaia philosophy: particularly archaeoastronomy, astronomy, ecology, environmentalism, the Gaia hypothesis, psychology, and physics. New Age practices and philosophies sometimes draw inspiration from major world religions: Buddhism, Chinese folk religion, Christianity, Hinduism, Islam, Judaism; with particularly strong influences from East Asian religions, Gnosticism, Neopaganism, New Thought, Spiritualism, Theosophy, Universalism, and Western esotericism.^[2] Additional terms for the movement include All is One^[3] and Mind-Body-Spirit.^[1]

The modern New Age movement emerged in a distinct form in the late 1960s and early 1970s, although its roots can be traced back to the 19th and early 20th centuries. It gained momentum in the 1980s and strengthened with the Harmonic Convergence event in 1987. Diverse individuals from around the world practice New Age spirituality.^{[citation needed]}

Movement

Origins

The term New Age was used as early as 1809 by William Blake who described a belief in a spiritual and artistic "New Age" in his preface to Milton: a Poem.

Some of the New Age movement's constituent elements appeared initially in 19th century metaphysical movements: Spiritualism, Theosophy, and New Thought; also, alternative medicine movements chiropractic and naturopathy.^[1][3] These movements in turn have roots in Transcendentalism, Mesmerism, Swedenborgianism, and various earlier Western esoteric or occult traditions, such as the hermetic arts of astrology, magic, alchemy, and Kabbalah. The term New Age was used in this context in Madame Blavatsky's book The Secret Doctrine, published in 1888.^[4]

A weekly journal of Christian liberalism and socialism titled The New Age was published as early as 1894;^[5] it was sold to a group of socialist writers headed by Alfred Richard Orage and Holbrook Jackson in 1907. Other historical personalities were involved: H. G. Wells, George Bernard Shaw, and William Butler Yeats; the magazine became a forum for politics, literature, and the arts.^[6][7] Between 1908 and 1914, it was instrumental in pioneering the British avant-garde from vorticism to imagism. After 1914, publisher Orage met P. D. Ouspensky, a follower of G. I. Gurdjieff, and began correspondence with Harry Houdini, becoming less interested in literature and art, with an increased focus on mysticism and other spiritual topics; the magazine was sold in 1921. According to Brown University, The New Age "... helped to shape modernism in literature and the arts from 1907 to 1922."^[8]

Development

Popularisation behind these ideas has roots in the work of early 20th century writers such as D. H. Lawrence and William Butler Yeats. In the early to middle 1900s, American mystic, theologian, and founder of the Association for Research and Enlightenment Edgar Cayce was a seminal influence on what later would be termed the New Age movement; he was known in particular for the practice some refer to as channeling.^[9] Former Theosophist Rudolf Steiner and his Anthroposophical Movement are a major influence. Neo-Theosophist Alice Bailey published the book Discipleship in the New Age (1944), which used the term New Age in reference to the transition from the Astrological Age of Pisces to Aquarius. While claims of racial bias in the writings of Rudolf Steiner and Alice Bailey were made,^[10] Steiner emphasized racial equality as a principle central to anthroposophical thought and humanity's progress.^[11][12] Any racial elements from these influences have not remained part of the Anthroposophical Society as contemporary adherents of the society have either not adopted or repudiated these beliefs.^[13][14] Another early usage of the term, was by the American artist, mystic, and philosopher Walter Russell, who spoke of "... this New Age philosophy of the spiritual re-awakening of man ..." in his essay "Power Through Knowledge", which was also published in 1944.

Carl Gustav Jung was an early articulator of the concept of the Age of Aquarius.^[15] In a letter to H. G. Baynes, dated 12 August 1940, he wrote in a passage concerning the destruction of the temple of Karnak by an earthquake in 26 BC: "1940 is the year when we approach the meridian of the first star in Aquarius. It is the premonitory earthquake of the New Age."^[16]

Postmodern

The subculture that would later be called New Age already existed in the early 1970s, based on and adopting ideas originally present in the counterculture of the 1960s. The Findhorn Foundation – an intentional community near Findhorn, Moray, Scotland founded in 1962 – played an instrumental role during the early growth period of the New Age movement; it continues to operate the Findhorn Ecovillage.

Widespread use of the term New Age began in the mid 1970s (reflected in the title of monthly periodical New Age Journal) and probably influenced several thousand small metaphysical book and gift stores that increasingly defined themselves as "New Age bookstores".^[17][18] As a result of the large-scale activities surrounding the Harmonic Convergence in the mid 1980s – the term was further popularised by the American mass media to describe the alternative spiritual subculture – including practices such as meditation, channeling, crystal healing, astral projection, psychic experience, holistic health, simple living, and environmentalism; or belief in phenomena such as Earth mysteries, ancient astronauts, extraterrestrial life, unidentified flying objects, crop circles, and reincarnation. A range of New Age publications appeared by the late 1980s such as Psychic Guide (later renamed Body, Mind & Spirit), Yoga Journal, New Age Voice, New Age Retailer, and NAPRA ReView by the New Age Publishers and Retailers Alliance.

There were several key moments in raising public awareness of this subculture: the publication of Linda Goodman's best selling astrology books Sun Signs (1968) and Love Signs (1978); Hair: The American Tribal Love-Rock Musical (1967) with the opening song "Aquarius" and its memorable line "This is the dawning of the Age of Aquarius" [emphasis added]; the broadcast of Shirley MacLaine's television mini-series Out on a Limb (1987); and the Harmonic Convergence (1987) organized by José Argüelles in Sedona, Arizona. Also influential were the claims of channelers Jane Roberts (the Seth Material) and J. Z. Knight (Ramtha), as well as revealed writings A Course in Miracles (1976) by Helen Schucman, The Celestine Prophecy (1993) by James Redfield, and Conversations with God (1995) by Neale Donald Walsch. Relevant works also include the writings of Eckhart Tolle, Barbara Marx Hubbard, Marianne Williamson, Deepak Chopra, John Holland, Gary Zukav, and Wayne Dyer; also, The Secret (2006) by Rhonda Byrne, which was based on the writings of Esther Hicks and Jerry Hicks.

The New Age (also referred to as the New Age movement, New Age spirituality, and Cosmic Humanism) is a decentralized Western social and spiritual movement that seeks "Universal Truth" and the attainment of the highest individual human potential. It includes aspects of Occultism, astrology, esotericism, metaphysics, alternative medicine, music, collectivism, sustainability, and nature. New Age spirituality is characterized by an individual approach to spiritual practices and philosophies, and the rejection of religious doctrine and dogma.

The New Age movement includes elements of older spiritual and religious traditions ranging from atheism and monotheism through classical pantheism, naturalistic pantheism, and panentheism to polytheism combined with science and Gaia philosophy: particularly archaeoastronomy, astronomy, ecology, environmentalism, the Gaia hypothesis, psychology, and physics. New Age practices and philosophies sometimes draw inspiration from major world religions: Buddhism, Chinese folk religion, Christianity, Hinduism, Islam, Judaism; with particularly strong influences from East Asian religions, Gnosticism, Neopaganism, New Thought, Spiritualism, Theosophy, Universalism, and Western esotericism.^[2] Additional terms for the movement include All is One^[3] and Mind-Body-Spirit.^[1]

The modern New Age movement emerged in a distinct form in the late 1960s and early 1970s, although its roots can be traced back to the 19th and early 20th centuries. It gained momentum in the 1980s and strengthened with the Harmonic Convergence event in 1987. Diverse individuals from around the world practice New Age spirituality.^{[citation needed]}

Movement

Origins

The term New Age was used as early as 1809 by William Blake who described a belief in a spiritual and artistic "New Age" in his preface to Milton: a Poem.

Some of the New Age movement's constituent elements appeared initially in 19th century metaphysical movements: Spiritualism, Theosophy, and New Thought; also, alternative medicine movements chiropractic and naturopathy.^[1][3] These movements in turn have roots in Transcendentalism, Mesmerism, Swedenborgianism, and various earlier Western esoteric or occult traditions, such as the hermetic arts of astrology, magic, alchemy, and Kabbalah. The term New Age was used in this context in Madame Blavatsky's book The Secret Doctrine, published in 1888.^[4]

A weekly journal of Christian liberalism and socialism titled The New Age was published as early as 1894;^[5] it was sold to a group of socialist writers headed by Alfred Richard Orage and Holbrook Jackson in 1907. Other historical personalities were involved: H. G. Wells, George Bernard Shaw, and William Butler Yeats; the magazine became a forum for politics, literature, and the arts.^[6][7] Between 1908 and 1914, it was instrumental in pioneering the British avant-garde from vorticism to imagism. After 1914, publisher Orage met P. D. Ouspensky, a follower of G. I. Gurdjieff, and began correspondence with Harry Houdini, becoming less interested in literature and art, with an increased focus on mysticism and other spiritual topics; the magazine was sold in 1921. According to Brown University, The New Age "... helped to shape modernism in literature and the arts from 1907 to 1922."^[8]

Development

Popularisation behind these ideas has roots in the work of early 20th century writers such as D. H. Lawrence and William Butler Yeats. In the early to middle 1900s, American mystic, theologian, and founder of the Association for Research and Enlightenment Edgar Cayce was a seminal influence on what later would be termed the New Age movement; he was known in particular for the practice some refer to as channeling.^[9] Former Theosophist Rudolf Steiner and his Anthroposophical Movement are a major influence. Neo-Theosophist Alice Bailey published the book Discipleship in the New Age (1944), which used the term New Age in reference to the transition from the Astrological Age of Pisces to Aquarius. While claims of racial bias in the writings of Rudolf Steiner and Alice Bailey were made,^[10] Steiner emphasized racial equality as a principle central to anthroposophical thought and humanity's progress.^[11][12] Any racial elements from these influences have not remained part of the Anthroposophical Society as contemporary adherents of the society have either not adopted or repudiated these beliefs.^[13][14] Another early usage of the term, was by the American artist, mystic, and philosopher Walter Russell, who spoke of "... this New Age philosophy of the spiritual re-awakening of man ..." in his essay "Power Through Knowledge", which was also published in 1944.

Carl Gustav Jung was an early articulator of the concept of the Age of Aquarius.^[15] In a letter to H. G. Baynes, dated 12 August 1940, he wrote in a passage concerning the destruction of the temple of Karnak by an earthquake in 26 BC: "1940 is the year when we approach the meridian of the first star in Aquarius. It is the premonitory earthquake of the New Age."^[16]

Postmodern

The subculture that would later be called New Age already existed in the early 1970s, based on and adopting ideas originally present in the counterculture of the 1960s. The Findhorn Foundation – an intentional community near Findhorn, Moray, Scotland founded in 1962 – played an instrumental role during the early growth period of the New Age movement; it continues to operate the Findhorn Ecovillage.

Widespread use of the term New Age began in the mid 1970s (reflected in the title of monthly periodical New Age Journal) and probably influenced several thousand small metaphysical book and gift stores that increasingly defined themselves as "New Age bookstores".^[17][18] As a result of the large-scale activities surrounding the Harmonic Convergence in the mid 1980s – the term was further popularised by the American mass media to describe the alternative spiritual subculture – including practices such as meditation, channeling, crystal healing, astral projection, psychic experience, holistic health, simple living, and environmentalism; or belief in phenomena such as Earth mysteries, ancient astronauts, extraterrestrial life, unidentified flying objects, crop circles, and reincarnation. A range of New Age publications appeared by the late 1980s such as Psychic Guide (later renamed Body, Mind & Spirit), Yoga Journal, New Age Voice, New Age Retailer, and NAPRA ReView by the New Age Publishers and Retailers Alliance.

There were several key moments in raising public awareness of this subculture: the publication of Linda Goodman's best selling astrology books Sun Signs (1968) and Love Signs (1978); Hair: The American Tribal Love-Rock Musical (1967) with the opening song "Aquarius" and its memorable line "This is the dawning of the Age of Aquarius" [emphasis added]; the broadcast of Shirley MacLaine's television mini-series Out on a Limb (1987); and the Harmonic Convergence (1987) organized by José Argüelles in Sedona, Arizona. Also influential were the claims of channelers Jane Roberts (the Seth Material) and J. Z. Knight (Ramtha), as well as revealed writings A Course in Miracles (1976) by Helen Schucman, The Celestine Prophecy (1993) by James Redfield, and Conversations with God (1995) by Neale Donald Walsch. Relevant works also include the writings of Eckhart Tolle, Barbara Marx Hubbard, Marianne Williamson, Deepak Chopra, John Holland, Gary Zukav, and Wayne Dyer; also, The Secret (2006) by Rhonda Byrne, which was based on the writings of Esther Hicks and Jerry Hicks.

The New Age (also referred to as the New Age movement, New Age spirituality, and Cosmic Humanism) is a decentralized Western social and spiritual movement that seeks "Universal Truth" and the attainment of the highest individual human potential. It includes aspects of Occultism, astrology, esotericism, metaphysics, alternative medicine, music, collectivism, sustainability, and nature. New Age spirituality is characterized by an individual approach to spiritual practices and philosophies, and the rejection of religious doctrine and dogma.

The New Age movement includes elements of older spiritual and religious traditions ranging from atheism and monotheism through classical pantheism, naturalistic pantheism, and panentheism to polytheism combined with science and Gaia philosophy: particularly archaeoastronomy, astronomy, ecology, environmentalism, the Gaia hypothesis, psychology, and physics. New Age practices and philosophies sometimes draw inspiration from major world religions: Buddhism, Chinese folk religion, Christianity, Hinduism, Islam, Judaism; with particularly strong influences from East Asian religions, Gnosticism, Neopaganism, New Thought, Spiritualism, Theosophy, Universalism, and Western esotericism.^[2] Additional terms for the movement include All is One^[3] and Mind-Body-Spirit.^[1]

The modern New Age movement emerged in a distinct form in the late 1960s and early 1970s, although its roots can be traced back to the 19th and early 20th centuries. It gained momentum in the 1980s and strengthened with the Harmonic Convergence event in 1987. Diverse individuals from around the world practice New Age spirituality.^{[citation needed]}

Movement

Origins

The term New Age was used as early as 1809 by William Blake who described a belief in a spiritual and artistic "New Age" in his preface to Milton: a Poem.

Some of the New Age movement's constituent elements appeared initially in 19th century metaphysical movements: Spiritualism, Theosophy, and New Thought; also, alternative medicine movements chiropractic and naturopathy.^[1][3] These movements in turn have roots in Transcendentalism, Mesmerism, Swedenborgianism, and various earlier Western esoteric or occult traditions, such as the hermetic arts of astrology, magic, alchemy, and Kabbalah. The term New Age was used in this context in Madame Blavatsky's book The Secret Doctrine, published in 1888.^[4]

A weekly journal of Christian liberalism and socialism titled The New Age was published as early as 1894;^[5] it was sold to a group of socialist writers headed by Alfred Richard Orage and Holbrook Jackson in 1907. Other historical personalities were involved: H. G. Wells, George Bernard Shaw, and William Butler Yeats; the magazine became a forum for politics, literature, and the arts.^[6][7] Between 1908 and 1914, it was instrumental in pioneering the British avant-garde from vorticism to imagism. After 1914, publisher Orage met P. D. Ouspensky, a follower of G. I. Gurdjieff, and began correspondence with Harry Houdini, becoming less interested in literature and art, with an increased focus on mysticism and other spiritual topics; the magazine was sold in 1921. According to Brown University, The New Age "... helped to shape modernism in literature and the arts from 1907 to 1922."^[8]

Development

Popularisation behind these ideas has roots in the work of early 20th century writers such as D. H. Lawrence and William Butler Yeats. In the early to middle 1900s, American mystic, theologian, and founder of the Association for Research and Enlightenment Edgar Cayce was a seminal influence on what later would be termed the New Age movement; he was known in particular for the practice some refer to as channeling.^[9] Former Theosophist Rudolf Steiner and his Anthroposophical Movement are a major influence. Neo-Theosophist Alice Bailey published the book Discipleship in the New Age (1944), which used the term New Age in reference to the transition from the Astrological Age of Pisces to Aquarius. While claims of racial bias in the writings of Rudolf Steiner and Alice Bailey were made,^[10] Steiner emphasized racial equality as a principle central to anthroposophical thought and humanity's progress.^[11][12] Any racial elements from these influences have not remained part of the Anthroposophical Society as contemporary adherents of the society have either not adopted or repudiated these beliefs.^[13][14] Another early usage of the term, was by the American artist, mystic, and philosopher Walter Russell, who spoke of "... this New Age philosophy of the spiritual re-awakening of man ..." in his essay "Power Through Knowledge", which was also published in 1944.

Carl Gustav Jung was an early articulator of the concept of the Age of Aquarius.^[15] In a letter to H. G. Baynes, dated 12 August 1940, he wrote in a passage concerning the destruction of the temple of Karnak by an earthquake in 26 BC: "1940 is the year when we approach the meridian of the first star in Aquarius. It is the premonitory earthquake of the New Age."^[16]

Postmodern

The subculture that would later be called New Age already existed in the early 1970s, based on and adopting ideas originally present in the counterculture of the 1960s. The Findhorn Foundation – an intentional community near Findhorn, Moray, Scotland founded in 1962 – played an instrumental role during the early growth period of the New Age movement; it continues to operate the Findhorn Ecovillage.

Widespread use of the term New Age began in the mid 1970s (reflected in the title of monthly periodical New Age Journal) and probably influenced several thousand small metaphysical book and gift stores that increasingly defined themselves as "New Age bookstores".^[17][18] As a result of the large-scale activities surrounding the Harmonic Convergence in the mid 1980s – the term was further popularised by the American mass media to describe the alternative spiritual subculture – including practices such as meditation, channeling, crystal healing, astral projection, psychic experience, holistic health, simple living, and environmentalism; or belief in phenomena such as Earth mysteries, ancient astronauts, extraterrestrial life, unidentified flying objects, crop circles, and reincarnation. A range of New Age publications appeared by the late 1980s such as Psychic Guide (later renamed Body, Mind & Spirit), Yoga Journal, New Age Voice, New Age Retailer, and NAPRA ReView by the New Age Publishers and Retailers Alliance.

There were several key moments in raising public awareness of this subculture: the publication of Linda Goodman's best selling astrology books Sun Signs (1968) and Love Signs (1978); Hair: The American Tribal Love-Rock Musical (1967) with the opening song "Aquarius" and its memorable line "This is the dawning of the Age of Aquarius" [emphasis added]; the broadcast of Shirley MacLaine's television mini-series Out on a Limb (1987); and the Harmonic Convergence (1987) organized by José Argüelles in Sedona, Arizona. Also influential were the claims of channelers Jane Roberts (the Seth Material) and J. Z. Knight (Ramtha), as well as revealed writings A Course in Miracles (1976) by Helen Schucman, The Celestine Prophecy (1993) by James Redfield, and Conversations with God (1995) by Neale Donald Walsch. Relevant works also include the writings of Eckhart Tolle, Barbara Marx Hubbard, Marianne Williamson, Deepak Chopra, John Holland, Gary Zukav, and Wayne Dyer; also, The Secret (2006) by Rhonda Byrne, which was based on the writings of Esther Hicks and Jerry Hicks.

A water ionizer is an appliance that ionizes water. Ionized water is purported to be beneficial to human health and marketed with claims that it is an antioxidant which can slow aging and prevent disease.^[1] Others note that such claims contradict basic laws of chemistry and physiology.^[2]

Ionization

A water ionizer separates water into alkaline and acid fractions using a process known as electrolysis.^[3] It does this by exploiting the electric charge of the calcium and magnesium ions present in nearly all sources of drinking water. When a source of water lacks mineral ions, such as distilled water, or has been filtered by reverse osmosis, water ionization has no effect.

Uses

Some research suggests that alkaline reduced water may be useful in scavenging free radicals in the laboratory setting.^[4] Tests on in vitro lymphocytes suggest that reduced water can prevent hydrogen peroxide-induced damage to DNA, RNA and certain proteins.^[5] However, drinking ionized water would not be expected to alter the body's pH, and there is no evidence of any claims made by manufacturers that drinking ionized water will have a noticeable effect on the body.^[2]

Electrolyzed water has been used by the food industry to sanitize food products; though effective in bacterial solutions, it was found less useful when sanitizing utensils, surfaces and food products.^[6][7] Acidic electrolyzed water (pH 2.3–2.6) may have use as a seed surface disinfectant or contact bactericide.^[8]

In typical usage, water refers only to its liquid form or state, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam. Water covers 71% of the Earth's surface^[2]. On Earth, it is found mostly in oceans and other large water bodies, with 1.6% of water below ground in aquifers and 0.001% in the air as vapor, clouds (formed of solid and liquid water particles suspended in air), and precipitation.^[3] Oceans hold 97% of surface water, glaciers and polar ice caps 2.4%, and other land surface water such as rivers, lakes and ponds 0.6%. A very small amount of the Earth's water is contained within biological bodies and manufactured products.

Water on Earth moves continually through a cycle of evaporation or transpiration (evapotranspiration), precipitation, and runoff, usually reaching the sea. Over land, evaporation and transpiration contribute to the precipitation over land.

Clean, fresh drinking water is essential to human and other lifeforms. Access to safe drinking water has improved steadily and substantially over the last decades in almost every part of the world.^[4][5] There is a clear correlation between access to safe water and GDP per capita.^[6] However, some observers have estimated that by 2025 more than half of the world population will be facing water-based vulnerability.^[7] A recent report (November 2009) suggests that by 2030, in some developing regions of the world, water demand will exceed supply by 50%.^[8] Water plays an important role in the world economy, as it functions as a solvent for a wide variety of chemical substances and facilitates industrial cooling and transportation. Approximately 70% of freshwater is consumed by agriculture.^[9]

Chemical and physical properties

Water is the chemical substance with chemical formula H₂O: one molecule of water has two hydrogen atoms covalently bonded to a single oxygen atom.

Water appears in nature in all three common states of matter and may take many different forms on Earth: water vapor and clouds in the sky; seawater and icebergs in the polar oceans; glaciers and rivers in the mountains; and the liquid in aquifers in the ground.

The major chemical and physical properties of water are:

• Water is a tasteless, odorless liquid at standard temperature and pressure. The color of water and ice is, intrinsically, a very light blue hue, although water appears colorless in small quantities. Ice also appears colorless, and water vapor is essentially invisible as a gas.^[10]

• Water is transparent, and thus aquatic plants can live within the water because sunlight can reach them. Only strong UV light is slightly absorbed.

• Since the water molecule is not linear and the oxygen atom has a higher electronegativity than hydrogen atoms, it carries a slight negative charge, whereas the hydrogen atoms are slightly positive. As a result, water is a polar molecule with an electrical dipole moment. The net interactions between the dipoles on each molecule cause an effective skin effect at the interface of water with other substances, or air at the surface, the latter given rise to water's high surface tension. This dipolar nature contributes to water molecules' tendency to form hydrogen bonds which cause water's many special properties.^[11] The polar nature also favors adhesion to other materials.

• Each hydrogen nucleus is bound to the central oxygen atom by a pair of electrons that are shared between them; chemists call this shared electron pair a covalent chemical bond. In H₂O, only two of the six outer-shell electrons of oxygen are used for this purpose, leaving four electrons which are organized into two non-bonding pairs. The four electron pairs surrounding the oxygen tend to arrange themselves as far from each other as possible in order to minimize repulsions between these clouds of negative charge. This would ordinarily result in a tetrahedral geometry in which the angle between electron pairs (and therefore the H-O-H bond angle) is 109.5°. However, because the two non-bonding pairs remain closer to the oxygen atom, these exert a stronger repulsion against the two covalent bonding pairs, effectively pushing the two hydrogen atoms closer together. The result is a distorted tetrahedral arrangement in which the H-O-H angle is 104.5°. ^[12]

• A result of interplay of these properties, Capillary action refers to the tendency of water to move up a narrow tube against the force of gravity. This property is relied upon by all vascular plants, such as trees.

• Water is a good solvent and is often referred to as the universal solvent. Substances that dissolve in water, e.g., salts, sugars, acids, alkalis, and some gases – especially oxygen, carbon dioxide (carbonation) are known as hydrophilic (water-loving) substances, while those that do not mix well with water (e.g., fats and oils), are known as hydrophobic (water-fearing) substances.

• All the major components in cells (proteins, DNA and polysaccharides) are also dissolved in water.

• Pure water has a low electrical conductivity, but this increases significantly with the dissolution of a small amount of ionic material such as sodium chloride.

• The boiling point of water (and all other liquids) is dependent on the barometric pressure. For example, on the top of Mt. Everest water boils at about 68 °C (154 °F), compared to 100 °C (212 °F) at sea level. Conversely, water deep in the ocean near geothermal vents can reach temperatures of hundreds of degrees and remain liquid.

• Water has the second highest specific heat capacity of any known substance, after ammonia, as well as a high heat of vaporization (40.65 kJ·mol^−1), both of which are a result of the extensive hydrogen bonding between its molecules. These two unusual properties allow water to moderate Earth's climate by buffering large fluctuations in temperature.

• The maximum density of water occurs at 3.98 °C (39.16 °F).^[13] Water becomes even less dense upon freezing, expanding 9%. This results in an unusual phenomenon: water's solid form, ice, floats upon water, allowing organisms to survive inside a partially-frozen water body because the water on the bottom has a temperature of around 4 °C (39 °F).

• Water is miscible with many liquids, such as ethanol, in all proportions, forming a single homogeneous liquid. On the other hand, water and most oils are immiscible usually forming layers according to increasing density from the top. As a gas, water vapor is completely miscible with air.

• Water forms an azeotrope with many other solvents.

• Water can be split by electrolysis into hydrogen and oxygen.

• As an oxide of hydrogen, water is formed when hydrogen or hydrogen-containing compounds burn or react with oxygen or oxygen-containing compounds. Water is not a fuel, it is an end-product of the combustion of hydrogen. The energy required to split water into hydrogen and oxygen by electrolysis or any other means is greater than the energy released when the hydrogen and oxygen recombine.^[14]

• Elements which are more electropositive than hydrogen such as lithium, sodium, calcium, potassium and caesium displace hydrogen from water, forming hydroxides. Being a flammable gas, the hydrogen given off is dangerous and the reaction of water with the more electropositive of these elements may be violently explosive.

Taste and odor

Water can dissolve many different substances, giving it varying tastes and odors. Humans and other animals have developed senses which (more or less) enable them to evaluate the potability of water by avoiding water that is too salty or putrid. Humans also tend to prefer cold water to lukewarm water since cold water is likely to contain fewer microbes. The taste advertised in spring water or mineral water derives from the minerals dissolved in it: Pure H₂O is tasteless and odorless. The advertised purity of spring and mineral water refers to absence of toxins, pollutants and microbes.

Distribution of water in nature

Water in the universe

Much of the universe's water may be produced as a byproduct of star formation. When stars are born, their birth is accompanied by a strong outward wind of gas and dust. When this outflow of material eventually impacts the surrounding gas, the shock waves that are created compress and heat the gas. The water observed is quickly produced in this warm dense gas.^[15]

Water has been detected in interstellar clouds within our galaxy, the Milky Way. Water probably exists in abundance in other galaxies, too, because its components, hydrogen and oxygen, are among the most abundant elements in the universe. Interstellar clouds eventually condense into solar nebulae and solar systems such as ours.

Water vapor is present in:

• Atmosphere of Mercury: 3.4%, and large amounts of water in Mercury's exosphere^[16]
• Atmosphere of Venus: 0.002%
• Earth's atmosphere: ~0.40% over full atmosphere, typically 1%-4% at surface
• Atmosphere of Mars: 0.03%
• Atmosphere of Jupiter: 0.0004%
• Atmosphere of Saturn - in ices only
• Enceladus (moon of Saturn): 91%
• exoplanets known as HD 189733 b^[17] and HD 209458 b.^[18]

Liquid water is present on:

• Earth - 71% of surface
• Moon - small amounts of water have been found (in 2008) in the inside of volcanic pearls brought from Moon to Earth by the Apollo 15 crew in 1971.^[19] NASA reported the detection of water molecules by NASA's Moon Mineralogy Mapper aboard the Indian Space Research Organization's Chandrayaan-1 spacecraft in September 2009.^[20]

Strong evidence suggests that liquid water is present just under the surface of Saturn's moon Enceladus and on Jupiter's moon Europa where it may exist as a 100 km deep ocean covering the whole moon which would amount to more water than is in all the Earth's oceans.

Water ice is present on:

• Earth - mainly as ice sheets
• polar ice caps on Mars
• Moon
• Titan
• Europa
• Saturn's rings ^[21]
• Enceladus
• Pluto and Charon^[22]
• Comets and comet source populations (Kuiper belt and Oort cloud objects).

Water ice may be present on Ceres and Tethys. Water and other volatiles probably comprise much of the internal structures of Uranus and Neptune.

Water and habitable zone

The existence of liquid water, and to a lesser extent its gaseous and solid forms, on Earth are vital to the existence of life on Earth as we know it. The Earth is located in the habitable zone of the solar system; if it were slightly closer to or further from the Sun (about 5%, or about 8 million kilometers), the conditions which allow the three forms to be present simultaneously would be far less likely to exist.^[23][24]

Earth's gravity allows it to hold an atmosphere. Water vapor and carbon dioxide in the atmosphere provide a temperature buffer (greenhouse effect) which helps maintain a relatively steady surface temperature. If Earth were smaller, a thinner atmosphere would allow temperature extremes, thus preventing the accumulation of water except in polar ice caps (as on Mars).

The surface temperature of Earth has been relatively constant through geologic time despite varying levels of incoming solar radiation (insolation), indicating that a dynamic process governs Earth's temperature via a combination of greenhouse gases and surface or atmospheric albedo. This proposal is known as the Gaia hypothesis.

The state of water on a planet depends on ambient pressure, which is determined by the planet's gravity. If a planet is sufficiently massive, the water on it may be solid even at high temperatures, because of the high pressure caused by gravity.

There are various theories about origin of water on Earth.

Water on Earth

Hydrology is the study of the movement, distribution, and quality of water throughout the Earth. The study of the distribution of water is hydrography. The study of the distribution and movement of groundwater is hydrogeology, of glaciers is glaciology, of inland waters is limnology and distribution of oceans is oceanography. Ecological processes with hydrology are in focus of ecohydrology.

The collective mass of water found on, under, and over the surface of a planet is called the hydrosphere. Earth's approximate water volume (the total water supply of the world) is 1,360,000,000 km³ (326,000,000 mi³).

Groundwater and fresh water are useful or potentially useful to humans as water resources.

Liquid water is found in bodies of water, such as an ocean, sea, lake, river, stream, canal, pond, or puddle. The majority of water on Earth is sea water. Water is also present in the atmosphere in solid, liquid, and vapor states. It also exists as groundwater in aquifers.

Water is important in many geological processes. Groundwater is ubiquitous in rocks, and the pressure of this groundwater affects patterns of faulting. Water in the mantle is responsible for the melt that produces volcanoes at subduction zones. On the surface of the Earth, water is important in both chemical and physical weathering processes. Water and, to a lesser but still significant extent, ice, are also responsible for a large amount of sediment transport that occurs on the surface of the earth. Deposition of transported sediment forms many types of sedimentary rocks, which make up the geologic record of Earth history.

Water cycle

The water cycle (known scientifically as the hydrologic cycle) refers to the continuous exchange of water within the hydrosphere, between the atmosphere, soil water, surface water, groundwater, and plants.

Water moves perpetually through each of these regions in the water cycle consisting of following transfer processes:

• evaporation from oceans and other water bodies into the air and transpiration from land plants and animals into air.
• precipitation, from water vapor condensing from the air and falling to earth or ocean.
• runoff from the land usually reaching the sea.

Most water vapor over the oceans returns to the oceans, but winds carry water vapor over land at the same rate as runoff into the sea, about 36 Tt per year. Over land, evaporation and transpiration contribute another 71 Tt per year. Precipitation, at a rate of 107 Tt per year over land, has several forms: most commonly rain, snow, and hail, with some contribution from fog and dew. Condensed water in the air may also refract sunlight to produce rainbows.

Water runoff often collects over watersheds flowing into rivers. A mathematical model used to simulate river or stream flow and calculate water quality parameters is hydrological transport model. Some of water is diverted to irrigation for agriculture. Rivers and seas offer opportunity for travel and commerce. Through erosion, runoff shapes the environment creating river valleys and deltas which provide rich soil and level ground for the establishment of population centers. A flood occurs when an area of land, usually low-lying, is covered with water. It is when a river overflows its banks or flood from the sea. A drought is an extended period of months or years when a region notes a deficiency in its water supply. This occurs when a region receives consistently below average precipitation.

Fresh water storage

Some runoff water is trapped for periods of time, for example in lakes. At high altitude, during winter, and in the far north and south, snow collects in ice caps, snow pack and glaciers. Water also infiltrates the ground and goes into aquifers. This groundwater later flows back to the surface in springs, or more spectacularly in hot springs and geysers. Groundwater is also extracted artificially in wells. This water storage is important, since clean, fresh water is essential to human and other land-based life. In many parts of the world, it is in short supply.

Sea water

Sea water contains about 3.5% salt on average, plus smaller amounts of other substances. The physical properties of sea water differ from fresh water in some important respects. It freezes at a lower temperature (about -1.9C) and its density increases with decreasing temperature to the freezing point, instead of reaching maximum density at a temperature above freezing. The salinity of water in major seas varies from about 0.7% in the Baltic Sea to 4.0% in the Red Sea.

Tides

Tides are the cyclic rising and falling of Earth's ocean surface caused by the tidal forces of the Moon and the Sun acting on the oceans. Tides cause changes in the depth of the marine and estuarine water bodies and produce oscillating currents known as tidal streams. The changing tide produced at a given location is the result of the changing positions of the Moon and Sun relative to the Earth coupled with the effects of Earth rotation and the local bathymetry. The strip of seashore that is submerged at high tide and exposed at low tide, the intertidal zone, is an important ecological product of ocean tides.

Effects on life

From a biological standpoint, water has many distinct properties that are critical for the proliferation of life that set it apart from other substances. It carries out this role by allowing organic compounds to react in ways that ultimately allow replication. All known forms of life depend on water. Water is vital both as a solvent in which many of the body's solutes dissolve and as an essential part of many metabolic processes within the body. Metabolism is the sum total of anabolism and catabolism. In anabolism, water is removed from molecules (through energy requiring enzymatic chemical reactions) in order to grow larger molecules (e.g. starches, triglycerides and proteins for storage of fuels and information). In catabolism, water is used to break bonds in order to generate smaller molecules (e.g. glucose, fatty acids and amino acids to be used for fuels for energy use or other purposes). Water is thus essential and central to these metabolic processes. Therefore, without water, these metabolic processes would cease to exist, leaving us to muse about what processes would be in its place, such as gas absorption, dust collection, etc.

Water is also central to photosynthesis and respiration. Photosynthetic cells use the sun's energy to split off water's hydrogen from oxygen. Hydrogen is combined with CO₂ (absorbed from air or water) to form glucose and release oxygen. All living cells use such fuels and oxidize the hydrogen and carbon to capture the sun's energy and reform water and CO₂ in the process (cellular respiration).

Water is also central to acid-base neutrality and enzyme function. An acid, a hydrogen ion (H⁺, that is, a proton) donor, can be neutralized by a base, a proton acceptor such as hydroxide ion (OH^−) to form water. Water is considered to be neutral, with a pH (the negative log of the hydrogen ion concentration) of 7. Acids have pH values less than 7 while bases have values greater than 7.

Stomach acid (HCl) is useful to digestion. However, its corrosive effect on the esophagus during reflux can temporarily be neutralized by ingestion of a base such as aluminum hydroxide to produce the neutral molecules water and the salt aluminum chloride. Human biochemistry that involves enzymes usually performs optimally around a biologically neutral pH of 7.4.

For example, a cell of Escherichia coli contains 70% of water, a human body 60–70%, plant body up to 90% and the body of an adult jellyfish is made up of 94–98% water.

Aquatic life forms

Earth's waters are filled with life. The earliest life forms appeared in water; nearly all fish live exclusively in water, and there are many types of marine mammals, such as dolphins and whales that also live in the water. Some kinds of animals, such as amphibians, spend portions of their lives in water and portions on land. Plants such as kelp and algae grow in the water and are the basis for some underwater ecosystems. Plankton is generally the foundation of the ocean food chain.

Aquatic animals must obtain oxygen to survive, and they do so in various ways. Fish have gills instead of lungs, although some species of fish, such as the lungfish, have both. Marine mammals, such as dolphins, whales, otters, and seals need to surface periodically to breathe air. Smaller life forms are able to absorb oxygen through their skin.

Effects on human civilization

Civilization has historically flourished around rivers and major waterways; Mesopotamia, the so-called cradle of civilization, was situated between the major rivers Tigris and Euphrates; the ancient society of the Egyptians depended entirely upon the Nile. Large metropolises like Rotterdam, London, Montreal, Paris, New York City, Buenos Aires, Shanghai, Tokyo, Chicago, and Hong Kong owe their success in part to their easy accessibility via water and the resultant expansion of trade. Islands with safe water ports, like Singapore, have flourished for the same reason. In places such as North Africa and the Middle East, where water is more scarce, access to clean drinking water was and is a major factor in human development.

Health and pollution

Water fit for human consumption is called drinking water or potable water. Water that is not potable can be made potable by filtration or distillation (heating it until it becomes water vapor, and then capturing the vapor without any of the impurities it leaves behind), or by other methods (chemical or heat treatment that kills bacteria). Sometimes the term safe water is applied to potable water of a lower quality threshold (i.e., it is used effectively for nutrition in humans that have weak access to water cleaning processes, and does more good than harm). Water that is not fit for drinking but is not harmful for humans when used for swimming or bathing is called by various names other than potable or drinking water, and is sometimes called safe water, or "safe for bathing". Chlorine is a skin and mucous membrane irritant that is used to make water safe for bathing or drinking. Its use is highly technical and is usually monitored by government regulations (typically 1 part per million (ppm) for drinking water, and 1–2 ppm of chlorine not yet reacted with impurities for bathing water).

This natural resource is becoming scarcer in certain places, and its availability is a major social and economic concern. Currently, about a billion people around the world routinely drink unhealthy water. Most countries accepted the goal of halving by 2015 the number of people worldwide who do not have access to safe water and sanitation during the 2003 G8 Evian summit.^[25] Even if this difficult goal is met, it will still leave more than an estimated half a billion people without access to safe drinking water and over a billion without access to adequate sanitation. Poor water quality and bad sanitation are deadly; some five million deaths a year are caused by polluted drinking water. The World Health Organization estimates that safe water could prevent 1.4 million child deaths from diarrhea each year.^[26] Water, however, is not a finite resource, but rather re-circulated as potable water in precipitation in quantities many degrees of magnitude higher than human consumption. Therefore, it is the relatively small quantity of water in reserve in the earth (about 1% of our drinking water supply, which is replenished in aquifers around every 1 to 10 years), that is a non-renewable resource, and it is, rather, the distribution of potable and irrigation water which is scarce, rather than the actual amount of it that exists on the earth. Water-poor countries use importation of goods as the primary method of importing water (to leave enough for local human consumption), since the manufacturing process uses around 10 to 100 times products' masses in water.

In the developing world, 90% of all wastewater still goes untreated into local rivers and streams.^[27] Some 50 countries, with roughly a third of the world’s population, also suffer from medium or high water stress, and 17 of these extract more water annually than is recharged through their natural water cycles.^[28] The strain not only affects surface freshwater bodies like rivers and lakes, but it also degrades groundwater resources.

Human uses

Agriculture

The most important use of water in agriculture is for irrigation, which is a key component to produce enough food. Irrigation takes up to 90% of water withdrawn in some developing countries^[29] and significant proportions in more economically developed countries (United States, 30% of freshwater usage is for irrigation).^[30]

Water as a scientific standard

On 7 April 1795, the gram was defined in France to be equal to "the absolute weight of a volume of pure water equal to a cube of one hundredth of a meter, and to the temperature of the melting ice."^[31] For practical purposes though, a metallic reference standard was required, one thousand times more massive, the kilogram. Work was therefore commissioned to determine precisely the mass of one liter of water. In spite of the fact that the decreed definition of the gram specified water at 0 °C—a highly reproducible temperature—the scientists chose to redefine the standard and to perform their measurements at the temperature of highest water density, which was measured at the time as 4 °C (39 °F).^[32]

The Kelvin temperature scale of the SI system is based on the triple point of water, defined as exactly 273.16 K or 0.01 °C. The scale is a more accurate development of the Celsius temperature scale, which was originally defined according the boiling point (set to 100 °C) and melting point (set to 0 °C) of water.

Natural water consists mainly of the isotopes hydrogen-1 and oxygen-16, but there is also small quantity of heavier isotopes such as hydrogen-2 (deuterium). The amount of deuterium oxides or heavy water is very small, but it still affects the properties of water. Water from rivers and lakes tends to contain less deuterium than seawater. Therefore, standard water is defined in the Vienna Standard Mean Ocean Water specification.

For drinking

The human body is anywhere from 55% to 78% water depending on body size.^[33] To function properly, the body requires between one and seven liters of water per day to avoid dehydration; the precise amount depends on the level of activity, temperature, humidity, and other factors. Most of this is ingested through foods or beverages other than drinking straight water. It is not clear how much water intake is needed by healthy people, though most advocates agree that 6–7 glasses of water (approximately 2 liters) daily is the minimum to maintain proper hydration.^[34] Medical literature favors a lower consumption, typically 1 liter of water for an average male, excluding extra requirements due to fluid loss from exercise or warm weather.^[35] For those who have healthy kidneys, it is rather difficult to drink too much water, but (especially in warm humid weather and while exercising) it is dangerous to drink too little. People can drink far more water than necessary while exercising, however, putting them at risk of water intoxication (hyperhydration), which can be fatal. The "fact" that a person should consume eight glasses of water per day cannot be traced back to a scientific source.^[36] There are other myths such as the effect of water on weight loss and constipation that have been dispelled.^[37]

An original recommendation for water intake in 1945 by the Food and Nutrition Board of the National Research Council read: "An ordinary standard for diverse persons is 1 milliliter for each calorie of food. Most of this quantity is contained in prepared foods."^[38] The latest dietary reference intake report by the United States National Research Council in general recommended (including food sources): 2.7 liters of water total for women and 3.7 liters for men.^[39] Specifically, pregnant and breastfeeding women need additional fluids to stay hydrated. According to the Institute of Medicine—who recommend that, on average, women consume 2.2 liters and men 3.0 liters—this is recommended to be 2.4 liters (10 cups) for pregnant women and 3 liters (12 cups) for breastfeeding women since an especially large amount of fluid is lost during nursing.^[40] Also noted is that normally, about 20% of water intake comes from food, while the rest comes from drinking water and beverages (caffeinated included). Water is excreted from the body in multiple forms; through urine and faeces, through sweating, and by exhalation of water vapor in the breath. With physical exertion and heat exposure, water loss will increase and daily fluid needs may increase as well.

Humans require water that does not contain too many impurities. Common impurities include metal salts and oxides (including copper, iron, calcium and lead)^[41] and/or harmful bacteria, such as Vibrio. Some solutes are acceptable and even desirable for taste enhancement and to provide needed electrolytes.^[42]

The single largest freshwater resource suitable for drinking is Lake Baikal in Siberia, which has a very low salt and calcium content and is therefore very clean.

Hygiene

The ability of water to make solutions and emulsions is used for washing. Many industrial processes rely on reactions using chemicals dissolved in water, suspension of solids in water slurries or using water to dissolve and extract substances.

Chemical uses

Water is widely used in chemical reactions as a solvent or reactant and less commonly as a solute or catalyst. In inorganic reactions, water is a common solvent, dissolving many ionic compounds. In organic reactions, it is not usually used as a reaction solvent, because it does not dissolve the reactants well and is amphoteric (acidic and basic) and nucleophilic. Nevertheless, these properties are sometimes desirable. Also, acceleration of Diels-Alder reactions by water has been observed. Supercritical water has recently been a topic of research. Oxygen-saturated supercritical water combusts organic pollutants efficiently.

As a heat transfer fluid

Water and steam are used as heat transfer fluids in diverse heat exchange systems, due to its availability and high heat capacity, both as a coolant and for heating. Cool water may even be naturally available from a lake or the sea. Condensing steam is a particularly efficient heating fluid because of the large heat of vaporization. A disadvantage is that water and steam are somewhat corrosive. In almost all electric power stations, water is the coolant, which vaporizes and drives steam turbines to drive generators. In the U.S., cooling power plants is the largest use of water.^[30]

In the nuclear industry, water can also be used as a neutron moderator. In a pressurized water reactor, water is both a coolant and a moderator. This provides a passive safety measure, as removing the water from the reactor also slows the nuclear reaction down.

Extinguishing fires

Water has a high heat of vaporization and is relatively inert, which makes it a good fire extinguishing fluid. The evaporation of water carries heat away from the fire. However, water cannot be used to fight fires of electric equipment, because impure water is electrically conductive, or of oils and organic solvents, because they float on water and the explosive boiling of water tends to spread the burning liquid.

Use of water in fire fighting should also take into account the hazards of a steam explosion, which may occur when water is used on very hot fires in confined spaces, and of a hydrogen explosion, when substances which react with water, such as certain metals or hot graphite, decompose the water, producing hydrogen gas.

The power of such explosions was seen in the Chernobyl disaster, although the water involved did not come from fire-fighting at that time but the reactor's own water cooling system. A steam explosion occurred when the extreme over-heating of the core caused water to flash into steam. A hydrogen explosion may have occurred as a result of reaction between steam and hot zirconium.

Recreation

Humans use water for many recreational purposes, as well as for exercising and for sports. Some of these include swimming, waterskiing, boating, surfing and diving. In addition, some sports, like ice hockey and ice skating, are played on ice. Lakesides, beaches and waterparks are popular places for people to go to relax and enjoy recreation. Many find the sound and appearance of flowing water to be calming, and fountains and other water features in public or private decorations.. Some keep fish and other life in aquariums or ponds for show, fun, and companionship. Humans also use water for snow sports i.e. skiing, sledding, snowmobiling or snowboarding, which requires the water to be frozen. People may also use water for play fighting such as with snowballs, water guns or water balloons.

Water industry

The water industry provides drinking water and wastewater services (including sewage treatment) to households and industry. Water supply facilities include water wells cisterns for rainwater harvesting, water supply network, water purification facilities, water tanks, water towers, water pipes including old aqueducts. Atmospheric water generators are in development.

Drinking water is often collected at springs, extracted from artificial borings (wells) in the ground, or pumped from lakes and rivers. Building more wells in adequate places is thus a possible way to produce more water, assuming the aquifers can supply an adequate flow. Other water sources include rainwater collection. Water may require purification for human consumption. This may involve removal of undissolved substances, dissolved substances and harmful microbes. Popular methods are filtering with sand which only removes undissolved material, while chlorination and boiling kill harmful microbes. Distillation does all three functions. More advanced techniques exist, such as reverse osmosis. Desalination of abundant seawater is a more expensive solution used in coastal arid climates.

The distribution of drinking water is done through municipal water systems, tanker delivery or as bottled water. Governments in many countries have programs to distribute water to the needy at no charge. Others argue that the market mechanism and free enterprise are best to manage this rare resource and to finance the boring of wells or the construction of dams and reservoirs.

Reducing usage by using drinking (potable) water only for human consumption is another option. In some cities such as Hong Kong, sea water is extensively used for flushing toilets citywide in order to conserve fresh water resources.

Polluting water may be the biggest single misuse of water; to the extent that a pollutant limits other uses of the water, it becomes a waste of the resource, regardless of benefits to the polluter. Like other types of pollution, this does not enter standard accounting of market costs, being conceived as externalities for which the market cannot account. Thus other people pay the price of water pollution, while the private firms' profits are not redistributed to the local population victim of this pollution. Pharmaceuticals consumed by humans often end up in the waterways and can have detrimental effects on aquatic life if they bioaccumulate and if they are not biodegradable.

Wastewater facilities are storm sewers and wastewater treatment plants. Another way to remove pollution from surface runoff water is bioswale.

Industrial applications

Water is used in power generation. Hydroelectricity is electricity obtained from hydropower. Hydroelectric power comes from water driving a water turbine connected to a generator. Hydroelectricity is a low-cost, non-polluting, renewable energy source. The energy is supplied by the sun. Heat from the sun evaporates water, which condenses as rain in higher altitudes, from where it flows down.

Pressurized water is used in water blasting and water jet cutters. Also, very high pressure water guns are used for precise cutting. It works very well, is relatively safe, and is not harmful to the environment. It is also used in the cooling of machinery to prevent over-heating, or prevent saw blades from over-heating.

Water is also used in many industrial processes and machines, such as the steam turbine and heat exchanger, in addition to its use as a chemical solvent. Discharge of untreated water from industrial uses is pollution. Pollution includes discharged solutes (chemical pollution) and discharged coolant water (thermal pollution). Industry requires pure water for many applications and utilizes a variety of purification techniques both in water supply and discharge.

Food processing

Water plays many critical roles within the field of food science. It is important for a food scientist to understand the roles that water plays within food processing to ensure the success of their products.

Solutes such as salts and sugars found in water affect the physical properties of water. The boiling and freezing points of water is affected by solutes. One mole of sucrose (sugar) per kilogram of water raises the boiling point of water by 0.51 °C, and one mole of salt per kg raises the boiling point by 1.02 °C; similarly, increasing the number of dissolved particles lowers water's freezing point.^[43] Solutes in water also affect water activity which affects many chemical reactions and the growth of microbes in food.^[44] Water activity can be described as a ratio of the vapor pressure of water in a solution to the vapor pressure of pure water.^[43] Solutes in water lower water activity. This is important to know because most bacterial growth ceases at low levels of water activity.^[44] Not only does microbial growth affect the safety of food but also the preservation and shelf life of food.

Water hardness is also a critical factor in food processing. It can dramatically affect the quality of a product as well as playing a role in sanitation. Water hardness is classified based on the amounts of removable calcium carbonate salt it contains per gallon. Water hardness is measured in grains; 0.064 g calcium carbonate is equivalent to one grain of hardness.^[43] Water is classified as soft if it contains 1 to 4 grains, medium if it contains 5 to 10 grains and hard if it contains 11 to 20 grains.^{[vague] [43]} The hardness of water may be altered or treated by using a chemical ion exchange system. The hardness of water also affects its pH balance which plays a critical role in food processing. For example, hard water prevents successful production of clear beverages. Water hardness also affects sanitation; with increasing hardness, there is a loss of effectiveness for its use as a sanitizer.^[43]

Boiling, steaming, and simmering are popular cooking methods that often require immersing food in water or its gaseous state, steam. Water is also used for dishwashing.

Water law, water politics and water crisis

Water politics is politics affected by water and water resources. For this reason, water is a strategic resource in the globe and an important element in many political conflicts. It causes health impacts and damage to biodiversity.

1.6 billion people have gained access to a safe water source since 1990 [1]. The proportion of people in developing countries with access to safe water is calculated to have improved from 30% in 1970^[4] to 71% in 1990, 79% in 2000 and 84% in 2004. This trend is projected to continue.^[5] To halve, by 2015, the proportion of people without sustainable access to safe drinking water is one of the Millennium Development Goals. This goal is projected to be reached.

A 2006 United Nations report stated that "there is enough water for everyone", but that access to it is hampered by mismanagement and corruption.^[45]

The UN World Water Development Report (WWDR, 2003) from the World Water Assessment Program indicates that, in the next 20 years, the quantity of water available to everyone is predicted to decrease by 30%. 40% of the world's inhabitants currently have insufficient fresh water for minimal hygiene. More than 2.2 million people died in 2000 from waterborne diseases (related to the consumption of contaminated water) or drought. In 2004, the UK charity WaterAid reported that a child dies every 15 seconds from easily preventable water-related diseases; often this means lack of sewage disposal; see toilet.

Organizations concerned with water protection include International Water Association (IWA), WaterAid, Water 1st, American Water Resources Association. Water related conventions are United Nations Convention to Combat Desertification (UNCCD), International Convention for the Prevention of Pollution from Ships, United Nations Convention on the Law of the Sea and Ramsar Convention. World Day for Water takes place on 22 March and World Ocean Day on 8 June.

Water used in the production of a good or service is virtual water.

Water in culture

Religion

Water is considered a purifier in most religions. Major faiths that incorporate ritual washing (ablution) include Christianity, Hinduism, Rastafari movement, Islam, Shinto, Taoism, and Judaism. Immersion (or aspersion or affusion) of a person in water is a central sacrament of Christianity (where it is called baptism); it is also a part of the practice of other religions, including Judaism (mikvah) and Sikhism (Amrit Sanskar). In addition, a ritual bath in pure water is performed for the dead in many religions including Judaism and Islam. In Islam, the five daily prayers can be done in most cases (see Tayammum) after completing washing certain parts of the body using clean water (wudu). In Shinto, water is used in almost all rituals to cleanse a person or an area (e.g., in the ritual of misogi). Water is mentioned in the Bible 442 times in the New International Version and 363 times in the King James Version: 2 Peter 3:5(b) states, "The earth was formed out of water and by water" (NIV). In the Koran it is stated that "Living things are made of water" and it is often used to described Paradise.

Philosophy

The Ancient Greek philosopher Empedocles held that water is one of the four classical elements along with fire, earth and air, and was regarded as the ylem, or basic substance of the universe. Water was considered cold and moist. In the theory of the four bodily humors, water was associated with phlegm. The classical element of Water was also one of the five elements in traditional Chinese philosophy, along with earth, fire, wood, and metal.

Water is also taken as a role model in some parts of traditional and popular Asian philosophy. James Legge's 1891 translation of the Dao De Jing states "The highest excellence is like (that of) water. The excellence of water appears in its benefiting all things, and in its occupying, without striving (to the contrary), the low place which all men dislike. Hence (its way) is near to (that of) the Tao" and "There is nothing in the world more soft and weak than water, and yet for attacking things that are firm and strong there is nothing that can take precedence of it—for there is nothing (so effectual) for which it can be changed."^[46]

Literature

Water is used in literature as a symbol of purification. Examples include the critical importance of a river in As I Lay Dying by William Faulkner and the drowning of Ophelia in Hamlet.

Sherlock Holmes held that "From a drop of water, a logician could infer the possibility of an Atlantic or a Niagara without having seen or heard of one or the other."^[47]

The New Age (also referred to as the New Age movement, New Age spirituality, and Cosmic Humanism) is a decentralized Western social and spiritual movement that seeks "Universal Truth" and the attainment of the highest individual human potential. It includes aspects of Occultism, astrology, esotericism, metaphysics, alternative medicine, music, collectivism, sustainability, and nature. New Age spirituality is characterized by an individual approach to spiritual practices and philosophies, and the rejection of religious doctrine and dogma.

The New Age movement includes elements of older spiritual and religious traditions ranging from atheism and monotheism through classical pantheism, naturalistic pantheism, and panentheism to polytheism combined with science and Gaia philosophy: particularly archaeoastronomy, astronomy, ecology, environmentalism, the Gaia hypothesis, psychology, and physics. New Age practices and philosophies sometimes draw inspiration from major world religions: Buddhism, Chinese folk religion, Christianity, Hinduism, Islam, Judaism; with particularly strong influences from East Asian religions, Gnosticism, Neopaganism, New Thought, Spiritualism, Theosophy, Universalism, and Western esotericism.^[2] Additional terms for the movement include All is One^[3] and Mind-Body-Spirit.^[1]

The modern New Age movement emerged in a distinct form in the late 1960s and early 1970s, although its roots can be traced back to the 19th and early 20th centuries. It gained momentum in the 1980s and strengthened with the Harmonic Convergence event in 1987. Diverse individuals from around the world practice New Age spirituality.^{[citation needed]}

Movement

Origins

The term New Age was used as early as 1809 by William Blake who described a belief in a spiritual and artistic "New Age" in his preface to Milton: a Poem.

Some of the New Age movement's constituent elements appeared initially in 19th century metaphysical movements: Spiritualism, Theosophy, and New Thought; also, alternative medicine movements chiropractic and naturopathy.^[1][3] These movements in turn have roots in Transcendentalism, Mesmerism, Swedenborgianism, and various earlier Western esoteric or occult traditions, such as the hermetic arts of astrology, magic, alchemy, and Kabbalah. The term New Age was used in this context in Madame Blavatsky's book The Secret Doctrine, published in 1888.^[4]

A weekly journal of Christian liberalism and socialism titled The New Age was published as early as 1894;^[5] it was sold to a group of socialist writers headed by Alfred Richard Orage and Holbrook Jackson in 1907. Other historical personalities were involved: H. G. Wells, George Bernard Shaw, and William Butler Yeats; the magazine became a forum for politics, literature, and the arts.^[6][7] Between 1908 and 1914, it was instrumental in pioneering the British avant-garde from vorticism to imagism. After 1914, publisher Orage met P. D. Ouspensky, a follower of G. I. Gurdjieff, and began correspondence with Harry Houdini, becoming less interested in literature and art, with an increased focus on mysticism and other spiritual topics; the magazine was sold in 1921. According to Brown University, The New Age "... helped to shape modernism in literature and the arts from 1907 to 1922."^[8]

Development

Popularisation behind these ideas has roots in the work of early 20th century writers such as D. H. Lawrence and William Butler Yeats. In the early to middle 1900s, American mystic, theologian, and founder of the Association for Research and Enlightenment Edgar Cayce was a seminal influence on what later would be termed the New Age movement; he was known in particular for the practice some refer to as channeling.^[9] Former Theosophist Rudolf Steiner and his Anthroposophical Movement are a major influence. Neo-Theosophist Alice Bailey published the book Discipleship in the New Age (1944), which used the term New Age in reference to the transition from the Astrological Age of Pisces to Aquarius. While claims of racial bias in the writings of Rudolf Steiner and Alice Bailey were made,^[10] Steiner emphasized racial equality as a principle central to anthroposophical thought and humanity's progress.^[11][12] Any racial elements from these influences have not remained part of the Anthroposophical Society as contemporary adherents of the society have either not adopted or repudiated these beliefs.^[13][14] Another early usage of the term, was by the American artist, mystic, and philosopher Walter Russell, who spoke of "... this New Age philosophy of the spiritual re-awakening of man ..." in his essay "Power Through Knowledge", which was also published in 1944.

Carl Gustav Jung was an early articulator of the concept of the Age of Aquarius.^[15] In a letter to H. G. Baynes, dated 12 August 1940, he wrote in a passage concerning the destruction of the temple of Karnak by an earthquake in 26 BC: "1940 is the year when we approach the meridian of the first star in Aquarius. It is the premonitory earthquake of the New Age."^[16]

Postmodern

The subculture that would later be called New Age already existed in the early 1970s, based on and adopting ideas originally present in the counterculture of the 1960s. The Findhorn Foundation – an intentional community near Findhorn, Moray, Scotland founded in 1962 – played an instrumental role during the early growth period of the New Age movement; it continues to operate the Findhorn Ecovillage.

Widespread use of the term New Age began in the mid 1970s (reflected in the title of monthly periodical New Age Journal) and probably influenced several thousand small metaphysical book and gift stores that increasingly defined themselves as "New Age bookstores".^[17][18] As a result of the large-scale activities surrounding the Harmonic Convergence in the mid 1980s – the term was further popularised by the American mass media to describe the alternative spiritual subculture – including practices such as meditation, channeling, crystal healing, astral projection, psychic experience, holistic health, simple living, and environmentalism; or belief in phenomena such as Earth mysteries, ancient astronauts, extraterrestrial life, unidentified flying objects, crop circles, and reincarnation. A range of New Age publications appeared by the late 1980s such as Psychic Guide (later renamed Body, Mind & Spirit), Yoga Journal, New Age Voice, New Age Retailer, and NAPRA ReView by the New Age Publishers and Retailers Alliance.

There were several key moments in raising public awareness of this subculture: the publication of Linda Goodman's best selling astrology books Sun Signs (1968) and Love Signs (1978); Hair: The American Tribal Love-Rock Musical (1967) with the opening song "Aquarius" and its memorable line "This is the dawning of the Age of Aquarius" [emphasis added]; the broadcast of Shirley MacLaine's television mini-series Out on a Limb (1987); and the Harmonic Convergence (1987) organized by José Argüelles in Sedona, Arizona. Also influential were the claims of channelers Jane Roberts (the Seth Material) and J. Z. Knight (Ramtha), as well as revealed writings A Course in Miracles (1976) by Helen Schucman, The Celestine Prophecy (1993) by James Redfield, and Conversations with God (1995) by Neale Donald Walsch. Relevant works also include the writings of Eckhart Tolle, Barbara Marx Hubbard, Marianne Williamson, Deepak Chopra, John Holland, Gary Zukav, and Wayne Dyer; also, The Secret (2006) by Rhonda Byrne, which was based on the writings of Esther Hicks and Jerry Hicks.

A water ionizer is an appliance that ionizes water. Ionized water is purported to be beneficial to human health and marketed with claims that it is an antioxidant which can slow aging and prevent disease.^[1] Others note that such claims contradict basic laws of chemistry and physiology.^[2]

Ionization

A water ionizer separates water into alkaline and acid fractions using a process known as electrolysis.^[3] It does this by exploiting the electric charge of the calcium and magnesium ions present in nearly all sources of drinking water. When a source of water lacks mineral ions, such as distilled water, or has been filtered by reverse osmosis, water ionization has no effect.

Uses

Some research suggests that alkaline reduced water may be useful in scavenging free radicals in the laboratory setting.^[4] Tests on in vitro lymphocytes suggest that reduced water can prevent hydrogen peroxide-induced damage to DNA, RNA and certain proteins.^[5] However, drinking ionized water would not be expected to alter the body's pH, and there is no evidence of any claims made by manufacturers that drinking ionized water will have a noticeable effect on the body.^[2]

Electrolyzed water has been used by the food industry to sanitize food products; though effective in bacterial solutions, it was found less useful when sanitizing utensils, surfaces and food products.^[6][7] Acidic electrolyzed water (pH 2.3–2.6) may have use as a seed surface disinfectant or contact bactericide.^[8]

Water purification is the process of removing undesirable chemicals, materials, and biological contaminants from raw water. The goal is to produce water fit for a specific purpose. Most water is purified for human consumption (drinking water) but water purification may also be designed for a variety of other purposes, including meeting the requirements of medical, pharmacology, chemical and industrial applications. In general the methods used include physical process such as filtration and sedimentation, biological processes such as slow sand filters or activated sludge, chemical process such as flocculation and chlorination and the use of electromagnetic radiation such as ultraviolet light.

The purification process of water may reduce the concentration of particulate matter including suspended particles, parasites, bacteria, algae, viruses, fungi; and a range of dissolved and particulate material derived from the surfaces that water may have made contact with after falling as rain.

The standards for drinking water quality are typically set by governments or by international standards. These standards will typically set minimum and maximum concentrations of contaminants for the use that is to be made of the water.

It is not possible to tell whether water is of an appropriate quality by visual examination. 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 the appropriate method of purification.

According to a 2007 World Health Organization report, 1.1 billion people lack access to an improved drinking water supply, 88% of the 4 billion annual cases of diarrheal disease are attributed to unsafe water and inadequate sanitation and hygiene, and 1.8 million people die from diarrheal diseases each year. The WHO estimates that 94% of these diarrheal cases are preventable through modifications to the environment, including access to safe water.^[1] Simple techniques for treating water at home, such as chlorination, filters, and solar disinfection, and storing it in safe containers could save a huge number of lives each year.^[2] Reducing deaths from waterborne diseases is a major public health goal in developing countries.

Sources of water

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; a process in which river water is injected into an aquifer to store the water in times of plenty so that it is available in times of drought; 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 vapor.
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.
6. Desalination of seawater by distillation or reverse osmosis.

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 - Water 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.

pH adjustment

Distilled water has a 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, soda ash, or sodium hydroxide is added to raise the pH. For somewhat acidic, alkaline waters (lower than 6.5), forced draft degassifiers are the cheapest way to lower the pH, as the process raises the pH by stripping dissolved carbon dioxide (carbonic acid) from the water. Lime is commonly used for pH adjustment for municipal water, or at the start of a treatment plant for process water, as it is cheap, but it also increases the ionic load by raising the 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. Acid (HCl or H₂SO₄) may be added to alkaline waters in some circumstances to lower the pH. Having an alkaline water does not necessarily mean that lead or copper from the plumbing system will not be dissolved into the water but as a generality, water with a pH above 7 is much less likely to dissolve heavy metals than a water with a pH below 7.

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 / flocculating agents that may be used include:

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. PolyDADMAC 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. The materials can also be biodegradable.

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 through 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.

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.

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]}

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 (such 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). ^[3]

Removal of ions and other dissolved substances

Ultrafiltration membranes use polymer membranes with chemically formed microscopic pores that can be used to filter out dissolved substances avoiding the use of 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.

Ion exchange:^{[4][5][6][7][8]} Ion exchange systems use ion exchange resin- or zeolite-packed columns to replace unwanted ions. The most common case is water softening consisting of removal of Ca²⁺ and Mg²⁺ ions replacing them with benign (soap friendly) Na⁺ or K⁺ ions. Ion exchange resins are also used to remove toxic ions such as nitrate, nitrite, lead, mercury, arsenic and many others.

Electrodeionization:^[8][4] Water is passed between a positive electrode and a negative electrode. Ion exchange membranes allow only positive ions to migrate from the treated water toward the negative electrode and only negative ions toward the positive electrode. High purity deionized water is produced with a little worse degree of purification in comparison with ion exchange treatment. Complete removal of ions from water is regarded as electrodialysis. The water is often pre-treated with a reverse osmosis unit to remove non-ionic organic contaminants.

Other mechanical and biological techniques

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:

• mechanical systems: sand filtration, lava filter systems and systems based on UV-radiation)
• biological systems:
  • plant systems as constructed wetlands and treatment ponds (sometimes incorrectly called reedbeds and living walls) and
  • compact systems as activated sludge systems, biorotors, aerobic biofilters and anaerobic biofilters, submerged aerated filters, and biorolls ^[9]

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.

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 protozoa, including Giardia 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.

Chlorine disinfection

The most common disinfection method involves 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) and the Drinking Water Inspectorate in the UK. 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 protozoa that form cysts in water (Giardia lamblia and Cryptosporidium, both of which are pathogenic).

Chlorine Dioxide Disinfection

Chlorine dioxide is a faster-acting disinfectant than elemental chlorine, however it is 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 supplied as an aqueous solution and added to water to avoid gas handling problems; chlorine dioxide gas accumulations may spontaneously detonate.

The use of chloramine is becoming more common as a disinfectant. Although chloramine is not as strong 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, as ammonia is used a nutrient for bacterial growth, with nitrates being generated as a by-product.

Ozone disinfection

O₃ is an unstable molecule, a "free radical" of oxygen which readily gives up one atom of oxygen providing a powerful oxidizing 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 protozoa 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 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.

Ultraviolet disinfection

Ultraviolet 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.

Hydrogen peroxide disinfection

Works in a similar way to ozone. Activators such as formic acid are often added to increase the efficacy of disinfection. It has the disadvantages that it is slow-working, phytotoxic in high dosage, and decreases the pH of the water it purifies.

Various portable methods of disinfection

Available for disinfection in emergencies or in remote locations. Disinfection is the primary goal, since aesthetic considerations such as taste, odour, appearance, and trace chemical contamination do not affect the short-term safety of drinking water.

Solar water disinfection

One low-cost method of disinfecting water that can often be implemented with locally available materials is solar disinfection (SODIS).^{[10][11][12][13]} Unlike methods that rely on firewood, it has low impact on the environment.

One recent study has found that the wild Salmonella which would reproduce quickly during subsequent dark storage of solar-disinfected water could be controlled by the addition of just 10 parts per million of hydrogen peroxide.^[14]

Additional treatment options

1. Water fluoridation: in many areas fluoride is added to water with the goal of preventing tooth decay.^[15] Fluoride is usually added after the disinfection process. In the U.S., fluoridation is usually accomplished by the addition of hexafluorosilicic acid,^[16] which decomposes in water, yielding fluoride ions.^[17]
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 that crystallise 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. Flouride is also a known carcinogen. One method of reducing fluoride levels is through treatment with activated alumina.

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 kilometres or 5000 feet) three minutes is recommended.^[18] 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: a form of activated carbon with a high surface area, adsorbs 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 as metallic silver nanoparticle. if water is held in the carbon block for longer period, microorganisms can grow inside which results in fouling and contamination. Silver nanoparticles are excellent anti-bacterial material and they can decompose toxic halo-organic compounds such as pesticides into non-toxic organic products.
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 unvapourised liquid carried with the steam. However, 99.9% pure water can be obtained by distillation.
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. The use of iron in removing arsenic from water. See Arsenic contamination of groundwater.
6. 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.
7. 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.

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 silica.

Another method that is used is reverse osmosis.

Safety and controversies

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.^{[citation needed]}

Many municipalities have moved from free chlorine to chloramine as a disinfection agent. However, chloramine in some water systems, appears to be a corrosive agent. Chloramine can dissolve the "protective" film inside older service line, with the leaching of lead into residential spigots. This can result in harmful exposure to lead, with elevated blood levels of lead the outcome. Lead is a known neurotoxin. ^[19]

Demineralized water

Distillation removes all minerals from water, and the membrane methods of reverse osmosis and nanofiltration remove most to all minerals. This results in demineralized water which is not considered ideal drinking water. The World Health Organization has investigated the health effects of demineralized water since 1980.^[20] Experiments in humans found that demineralized water increased diuresis and the elimination of electrolytes, with decreased blood serum potassium concentration. Magnesium, calcium, and other minerals in water can help to protect against nutritional deficiency. Demineralized water may also increase the risk from toxic metals because it more readily leaches materials from piping like lead and cadmium, which is prevented by dissolved minerals such as calcium and magnesium. Low-mineral water has been implicated in specific cases of lead poisoning in infants, when lead from pipes leached at especially high rates into the water. Recommendations for magnesium have been put at a minimum of 10 mg/L with 20–30 mg/L optimum; for calcium a 20 mg/L minimum and a 40–80 mg/L optimum, and a total water hardness (adding magnesium and calcium) of 2 to 4 mmol/L. At water hardness above 5 mmol/L, higher incidence of gallstones, kidney stones, urinary stones, arthrosis, and arthropathies have been observed.^[21] Additionally, desalination processes can increase the risk of bacterial contamination.^[21]

Manufacturers of home water distillers, of course, claim the opposite -- that minerals in water are the cause of many diseases, and that most beneficial minerals come from food, not water.^[22][23][24] They quote the American Medical Association as saying "The body's need for minerals is largely met through foods, not drinking water."^[25] The WHO report agrees that "drinking water, with some rare exceptions, is not the major source of essential elements for humans" and is "not the major source of our calcium and magnesium intake", yet states that demineralized water is harmful anyway. "Additional evidence comes from animal experiments and clinical observations in several countries. Animals given zinc or magnesium dosed in their drinking water had a significantly higher concentration of these elements in the serum than animals given the same elements in much higher amounts with food and provided with low-mineral water to drink."

A water filter removes impurities from water by means of a fine physical barrier, a chemical process or a biological process. Filters cleanse water to various extents for irrigation, drinking water, aquariums, and swimming pools.

Methods of filtration

Filters use sieving, adsorption, ion exchanges and other processes. Unlike a sieve or screen, a filter can remove particles much smaller than the holes through which the water passes.

Types of filters

Water treatment plant filters

Types of water filters include media filters, screen filters, disk filters, slow sand filter beds, rapid sand filters and cloth filters.^[1]

Point-of-use filters

Point-of-use filters for home use include granular activated carbon filters (GAC) used for carbon filtering, metallic alloy filters, microporous ceramic filters, carbon block resin (CBR) and ultrafiltration membranes. Some filters use more than one filtration method. An example of this is a multi-barrier system. Jug filters can be used for small quantities of drinking water. Some kettles have built-in filters, primarily to reduce limescale buildup.

Portable water filters

Water filters are used by hikers, by aid organizations during humanitarian emergencies, and by the military. These filters are usually small, portable and light (1-2 pounds/0.5-1.0 kg or less), and usually filter water by working a mechanical hand pump, although some use a siphon drip system to force water through while others are built into water bottles. Dirty water is pumped via a screen-filtered flexible silicon tube through a specialized filter, ending up in a container. These filters work to remove bacteria, protozoa and microbial cysts that can cause disease. Filters may have fine meshes that must be replaced or cleaned, and ceramic water filters must have their outside abraded when they have become clogged with impurities.

These water filters should not be confused with devices or tablets that are water purifiers, some of which remove or kill viruses such as hepatitis A and rotavirus.

Homemade water filters

Water filters can be made on-site using local materials such as grass, charcoal (e.g. from burned firewood), and sand. These filters have been used by soldiers and outdoor enthusiasts.^[2] Due to their low cost they can be made and used by anyone, including the poor, who often do not have access to safe drinking water. Regrettably such filters do little if anything to mitigate against pathogens and other harmful constituents and can give a false sense of security that the water so produced is potable.

Water polishing

The term water polishing can refer to any process that removes small (usually microscopic) unwanted material from a portion of water. The process and its meaning vary from setting to setting: a manufacturer of aquarium filters may claim that its filters perform water polishing by capturing "micro particles" within nylon or polyester pads^[3] just as a chemical engineer can use the term to refer to the removal of magnetic resins from a solution by passing the solution over a bed of magnetic particulate.^[4] In this sense, water polishing is simply another term for water filtration.

Drinking water or potable water is water of sufficiently high quality that it can be consumed or used without risk of immediate or long term harm. In most developed countries, the water supplied to households, commerce and industry is all of drinking water standard, even though only a very small proportion is actually consumed or used in food preparation.

Over large parts of the world, humans have inadequate access to potable water and use sources contaminated with disease vectors, pathogens or unacceptable levels of dissolved chemicals or suspended solids. Such water is not potable and drinking or using such water in food preparation leads to widespread acute and chronic illnesses and is a major cause of death in many countries. Reduction of waterborne diseases is a major public health goal in developing countries.

Typically, water supply networks deliver potable water, whether it is to be used for drinking, washing or landscape irrigation. One counterexample is urban China, where drinking water can optionally be delivered by a separate tap.

General

Essential to the survival of all organisms,^[1] water has always been an important and life-sustaining drink to humans. Excluding fat, water composes approximately 70% of the human body by mass. It is a crucial component of metabolic processes and serves as a solvent for many bodily solutes. Health authorities have historically suggested at least eight glasses, eight fluid ounces each (168 ml), of water per day (64 fluid ounces, or 1.89 litres),^[2][3] and the British Dietetic Association recommends 1.8 litres.^[1] The United States Environmental Protection Agency has determined that the average adult actually ingests 2.0 litres per day.^[3]

Spring water, a natural resource from which much bottled water comes, is generally imbued with minerals.^[4] Tap water, delivered by domestic water systems in developed nations, refers to water piped to homes through a tap. All of these forms of water are commonly drunk, often purified through filtration.^[5]

Water quality and contaminants

Throughout most of the world, the most common contamination of raw water sources is from human sewage and in particular human faecal pathogens and parasites. In 2006, waterborne diseases were estimated to cause 1.8 million deaths each year while about 1.1 billion people lacked proper drinking water.^[6]. It is clear that people in the developing world need to have access to good quality water in sufficient quantity, water purification technology and availability and distribution systems for water. In many parts of the world the only sources of water are from small streams often directly contaminated by sewage.

Most water requires some type of treatment before use, even water from deep wells or springs. The extent of treatment depends on the source of the water. Appropriate technology options in water treatment include both community-scale and household-scale point-of-use (POU) designs.^[7]. A few large urban areas such as Christchurch. New Zealand have access to sufficiently pure water of sufficient volume that no treatment of the raw water is required.^[8]

The most reliable way to kill microbial pathogenic agents is to heat water to a rolling boil^[9] but this requires abundant sources of fuel and is very onerous on the households, especially where it is difficult to store boiled water in sterile conditions. Other techniques, such as filtration, chemical disinfection, and exposure to ultraviolet radiation (including solar UV) have been demonstrated in an array of randomized control trials to significantly reduce levels of water-borne disease among users in low-income countries^[10], but these suffer from the same problems as boiling methods.

Over the past decade, an increasing number of field-based studies have been undertaken to determine the success of POU measures in reducing waterborne disease. The ability of POU options to reduce disease is a function of both their ability to remove microbial pathogens if properly applied and such social factors as ease of use and cultural appropriateness. Technologies may generate more (or less) health benefit than their lab-based microbial removal performance would suggest.

The current priority of the proponents of POU treatment is to reach large numbers of low-income households on a sustainable basis. Few POU measures have reached significant scale thus far, but efforts to promote and commercially distribute these products to the world's poor have only been under way for a few years.

Parameters for drinking water quality typically fall under two categories: chemical/physical and microbiological. Chemical/physical parameters include heavy metals, trace organic compounds, total suspended solids (TSS), and turbidity. Microbiological parameters include Coliform bacteria, E. coli, and specific pathogenic species of bacteria (such as cholera-causing Vibrio cholerae), viruses, and protozoan parasites.

Chemical parameters tend to pose more of a chronic health risk through buildup of heavy metals although some components like nitrates/nitrites and arsenic may have a more immediate impact. Physical parameters affect the aesthetics and taste of the drinking water and may complicate the removal of microbial pathogens.

Originally, fecal contamination was determined with the presence of coliform bacteria, a convenient marker for a class of harmful fecal pathogens. The presence of fecal coliforms (like E. Coli) serves as an indication of contamination by sewage. Additional contaminants include protozoan oocysts such as Cryptosporidium sp., Giardia lamblia, Legionella, and viruses (enteric).^[11] Microbial pathogenic parameters are typically of greatest concern because of their immediate health risk.

Access

70% of the Earth's surface is covered by water. Water is available almost everywhere if proper methods are used to get it. Sources where water may be obtained include:

• ground sources such as groundwater, hyporheic zones and aquifers.
• precipitation which includes rain, hail, snow, fog, etc.
• surface water such as rivers, streams, glaciers
• biological sources such as plants.
• the sea through desalination

Access to drinkable water is a complicated, yet vital issue. There is great diversity in access not only between countries but within countries and even cities.

Cost is the major limiting factor of access to drinkable water.

The most efficient way to transport and deliver potable water is through pipes. However, this requires a enormous up front infrastructure costs. Further the high continual operating costs mean many systems fall into disrepair in both developed and undeveloped countries. The cost to replace the deteriorating water and sanitation infrastructure of industrialized countries may be as high as $200 billion a year. Further, Leakage of pipes reduces access to water. Leakage rates of 50% are not uncommon in urban systems ^[12]

Because of the high initial investments, many debt impoverished nations cannot afford to develop this infrastructure. So people in these areas end up paying a much higher percentage of their income on water. ^[13] 2003 statistics from El Salvador, for example, indicate that the poorest 20% of households spend more than 10% of their total income on water. In the United Kingdom authorities define spending of more than 3% of one's income on water as a hardship.^[14]

The Millennium Development Goal of halving the proportion of people without access to safe drinking water between 1990 and 2015 will probably be reached. Although some countries still face enormous challenges. ^[15]

Rural communities are the furthest from meeting the 2015 MDGs drinking water target. Globally only 27% of the rural population has water piped directly to their home and 24% rely on unimproved sources. Of the 884 million people without access to an improved water source, 746 million people (84%) live in rural areas. Sub-Saharan Africa has made the least progress in improved water sources since 1990, improving only 9% to 2006. In contrast, the Eastern Asian region saw a dramatic drop from 45% to 9% reliance on unimproved water in the same time period.^[16]

In the U.S, the typical nonconserving single family home uses 69.3 gallons of water per capita per day. In some parts of the country there are water supplies that are dangerously low due to drought, particularly in the West and the South East region of the U.S.^[18].

Requirements

Water is necessary for most life on Earth. Humans can survive for several weeks without food, but for only a few days without water. The exact amount of water a human needs is highly individual, as it depends on the condition of the subject, the amount of physical exercise, and on the environmental temperature and humidity.^[19] In the US, the reference daily intake (RDI) for water is 3.7 litres per day for human males older than 18, and 2.7 litres for human females older than 18^[20] including water contained in food, beverages, and drinking water. It is a common misconception that everyone should drink two litres (68 ounces, or about eight 8-oz glasses) of water per day and is not supported by scientific research. Various reviews of all the scientific literature on the topic performed in 2002 and 2008 could not find any solid scientific evidence that recommended drinking eight glasses of water per day.^{[21] [22] [23]} For example, people in hotter climates will require greater water intake than those in cooler climates. An individual's thirst provides a better guide for how much water they require rather than a specific, fixed number. A more flexible guideline is that a normal person should urinate 4 times per day, and the urine should be a light yellow color.

A constant supply is needed to replenish the fluids lost through normal physiological activities, such as respiration, perspiration and urination. Food contributes 0.5 to 1 litre, and the metabolism of protein, fat, and carbohydrates produces another 0.25 to 0.4 litres^[24], which means that 2 to 3 litres of water for men and 1 to 2 litres of water for women should be taken in as fluid in order to meet the RDI. In terms of mineral nutrients intake, it is unclear what the drinking water contribution is. However, inorganic minerals generally enter surface water and ground water via storm water runoff or through the Earth's crust. Treatment processes also lead to the presence of some mineral nutrients. Examples include fluoride, calcium, zinc, manganese, phosphate, and sodium compounds.^[25] Water generated from the biochemical metabolism of nutrients provides a significant proportion of the daily water requirements for some arthropods and desert animals, but provides only a small fraction of a human's necessary intake. There are a variety of trace elements present in virtually all potable water, some of which play a role in metabolism. For example sodium, potassium and chloride are common chemicals found in small quantities in most waters, and these elements play a role (not necessarily major) in body metabolism. Other elements such as fluoride, while beneficial in low concentrations, can cause dental problems and other issues when present at high levels. Water is essential for the growth and maintenance of our bodies, as it is involved in a number of biological processes.

Profuse sweating can increase the need for electrolyte (salt) replacement. Water intoxication (which results in hyponatremia), the process of consuming too much water too quickly, can be fatal.

The human kidneys will normally adjust to varying levels of water intake. The kidneys will require time to adjust to the new water intake level. This can cause someone who drinks a lot of water to become dehydrated more easily than someone who routinely drinks less. Survival classes recommend that someone who expects to be in an environment with little water (such as a desert), not to drink water excessively, but rather to drink gradually decreasing amounts for several days before their trip to accustom the kidneys to making concentrated urine. Not using this method can, and has been known to be fatal.^[26]

Indicators of safe drinking water

Access to safe drinking water is indicated by the number of people using proper sanitary sources. These improved drinking water sources include household connection, public standpipe, borehole condition, protected dug well, protected spring, and rain water collection. Sources that don't encourage improved drinking water to the same extent as previously mentioned include: unprotected well, unprotected spring, rivers or ponds, vender-provided water, bottled water (consequential of limitations in quantity, not quality of water), and tanker truck water. Access to sanitary water comes hand in hand with access to improved sanitation facilities for excreta. These facilities include connection to public sewer, connection to septic system, pour-flush latrine, and ventilated improved pit latrine. Unimproved sanitation facilities are: public or shared latrine, open pit latrine, or bucket latrine^[27].

Diarrhea as a major health effect among children

Diarrheal diseases cause ninety percent of all deaths of children under five years old in developing countries. Malnutrition, especially protein-energy malnutrition, can decrease the children's resistance to infections, including water-related diarrheal diseases. In 2000-2003, 769,000 children under five years old in sub-Saharan Africa died each year from diarrheal diseases. As a result of only thirty-six percent of the population in the sub-Saharan region having access to proper means of sanitation, more than 2000 childrens' lives are lost every day. In South Asia, 683,000 children under five years old died each year from diarrheal disease from 2000-2003. During the same time period, in developed countries, 700 children under five years old died from diarrheal disease. Improved water supply reduces diarrhea morbidity by twenty-five percent and improvements in drinking water through proper storage in the home and chlorination reduces diarrhea episodes by thirty-nine percent.^[28]

Improving the availability of drinking water

One of the Millennium Development Goals (MDGs) set by the UN includes environmental sustainability. In 2004, only forty-two percent of people in rural areas had access to clean water.^[29].

Solar water disinfection is a low-cost method of purifying water that can often be implemented with locally available materials.^{[30][31][32][33]} Unlike methods that rely on firewood, it has low impact on the environment.

One program developed to help people gain access to safe drinking water is the Water Aid program. Working in 17 countries to help provide water, Water Aid international is helping the sanitation and hygiene education to some of the world's poorest people.[10]

The Global Framework for Action (GF4A) is a organization that brings together stakeholders, national governments, donors and NGOs (such as Water aid) to define manageable targets and deadlines. 23 Countries are off-track to meet the MDG goals for improved water availability. ^[34]

However, not all efforts to increase availability of safe drinking water have been effective, and some have been damaging. The 1980s was declared the International Decade of water by the UN. However, the assumption was made that groundwater is inherently safer than water from rivers, ponds and canals. While instances of cholera, typhoid and diarrhea were reduced toxic level of fluoride were found. Borehole wells were either not tested or not tested thoroughly. Fluoride slowly dissolved from the granite rocks underneath India and slowly poisoned the population, particularly evident in the bone deformations of children. ^[35]. Further, in Bangladesh, it is estimated that half of the countries 12 million tube wells have unacceptable levels of arsenic due to the wells not being dug deep enough (past 100 M). The Bangladeshi government had spent less than $7 million of the 34 million allocated for solving the problem by the World Bank in 1998. ^{[36] [37]}. Natural arsenic poisoning is a global threat, 140 million people affected in 70 countries on all continents. ^[38] These examples illustrate the need to examine each location on a case by case basis and not assume what works in one area will work in another.

In education

In Britain, many schools have poor provision of drinking water to pupils through the day. Studies have been made upon the effect of increasing the provision of water and significant improvements in test scores have been observed. Areas such as Brighton have introduced a Schools Water Policy to ensure an adequate intake of 1.5 to 1.75 litres for 5-10 year olds.^[39]

Drinking water regulation

European Union

The EU sets legislation on drinking water quality in addition to factors such as how, where and when water can be extracted from the environment. Directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000 establishing a framework for Community action in the field of water policy, known as the water framework directive, is the primary piece of legislation governing drinking water.^[40]

Each member state is responsible for establishing the required policing measures to ensure that the legislation is implemented. For example, in the UK the Drinking Water Inspectorate polices the water companies.

United States of America

In the United States, the Environmental Protection Agency (EPA) sets standards for tap and public water systems under the Safe Drinking Water Act (SDWA).^[41] The Food and Drug Administration (FDA) regulates bottled water as a food product under the Federal Food, Drug, and Cosmetic Act (FFDCA).^[42] Bottled water is not necessarily more pure, or more tested, than public tap water.^[43] However, there is evidence that the United States federal regulations of drinking water do not ensure safe water, as some of the regulations have not been updated with more recent science. Dr. Peter W. Pruess, who became the head of the U.S. EPA's division analyzing environmental risks in 2004, has been "particularly concerned", and has faced controversy in studies which suggest that regulations against certain chemicals should be tightened.^[44]

Standard potability testing

A standard testing of water's potability consists of drawing a sample from a known property or water source, providing State Certified Nitrate/Nitrogen and Coliform Bacteria Testing, along with E.Coli testing (FHA/VA). It also means providing testing for Total Dissolved Solids, Water Hardness, pH, and Iron Content Testing. A Certified Laboratory must provide proper operation of all Water Softening and Filtration Systems, and provide written results of the above testing with a standarized time frame (2 weeks general).

Bottled water

Drinking water of a variety of qualities is bottled and sold for public consumption throughout the world. Trends in sales and consumption of bottled water have risen significantly in the last two decades in both developed and developing countries.

Drinking water preferences of animals

The qualitative and quantitative aspects of drinking water requirements of domesticated animals are studied and described within the context of animal husbandry. However, relatively few studies have been focused on the drinking behavior of wild animals. A recent study has shown, e.g., that feral pigeons do not discriminate drinking water according to its content of methabolic wastes, such as uric acid or urea (mimicing faeces- or urine-pollution by birds or mammals respectively). ^[45]

In chemistry, an alkali (from Arabic: Al-Qaly القلي, القالي ) is a basic, ionic salt of an alkali metal or alkaline earth metal element. Alkalis are best known for being bases that dissolve in water. Bases are compounds with a pH greater than 7. The adjective alkaline is commonly used in English as a synonym for base, especially for soluble bases. This broad use of the term is likely to have come about because alkalis were the first bases known to obey the Arrhenius definition of a base and are still among the more common bases. Since Brønsted-Lowry acid-base theory, the term alkali in chemistry is normally restricted to those salts containing alkali and alkaline earth metal elements.

Etymology

The word "alkali" is derived from Arabic al qalīy = the calcined ashes, referring to the original source of alkaline substance. Ashes were used in conjunction with animal fat to produce soap, a process known as saponification.

Common properties

Alkalis are all Arrhenius bases, which form hydroxide ions (OH^-) when dissolved in water. Common properties of alkaline aqueous solutions include:

• Moderately-concentrated solutions (over 10^−3 M) have a pH of 7.1 or greater. This means that they will turn phenolphthalein from colorless to pink.
• Concentrated solutions are caustic (causing chemical burns).
• Alkaline solutions are slippery or soapy to the touch, due to the saponification of the fatty acids on the surface of the skin.
• Alkalis are normally water soluble, although some like barium carbonate are only soluble when reacting with an acidic aqueous solution.
• Acids and alkalis are measured on a pH scale
• Alkalis are commonly found in household cleaners and toothpaste

Confusion between alkali and base

The terms "base" and "alkali" are often used interchangeably, particularly outside of a scientific context, but they do not have the same meaning. While all alkaline solutions are basic, not all bases are alkaline. The following are common mistakes:

• The phrase "measuring the alkalinity of soil" is incorrect since the property measured is actually the pH (base property).
• Calling bases that are not alkalis, such as ammonia, alkaline (ammonia is a base but not an alkali).

Also, not all salts formed by alkali metals are alkaline; this designation applies only to those salts that are basic. And while most electropositive metal oxides are basic, only the soluble alkali metal and alkaline earth metal oxides can be correctly called alkalis.

This definition of an alkali as a basic salt of an alkali metal or alkaline earth metal is the most common, based on dictionary definitions [1][2], however conflicting definitions of the term alkali do exist. These include:

• Any base that is water-soluble and forms hydroxide ions [3][4]. In chemistry, this is more accurately called an Arrhenius base.

• The solution of a base in water [5]. This would be an Arrhenius base in solution.

• Name given by chemists to an important group of subtances, the behaviour of bases the main alkali are 1,the hydroxides potassium 2,

Salts

Most basic salts are alkali salts, of which common examples are:

• sodium hydroxide (often called "caustic soda")
• potassium hydroxide (commonly called "caustic potash")
• lye (generic term, for either of the previous two, or even for a mixture)
• calcium carbonate (sometimes called "free lime")
• magnesium hydroxide is an example of an atypical alkali since it has low solubility in water (although the dissolved portion is considered a strong base due to complete dissociation of its ions).

Alkaline soil

Soil with a pH value higher than 7.3 is normally referred to as alkaline. This soil property can occur naturally, due to the presence of alkali salts. Although some plants do prefer slightly basic soil (including vegetables like cabbage and fodder like buffalograss), most plants prefer a mildly acidic soil (pH between 6.0 and 6.8), and alkaline soils can cause problems.

Lakes

In alkali lakes (a type of salt lake), evaporation concentrates the naturally-occurring alkali salts, often forming a crust of mildly-basic salt across a large area.

Examples of alkali lakes:

• Redberry Lake, Saskatchewan, Canada.
• Tramping Lake, Saskatchewan, Canada.
• Mono lake, California, United States
• Summer Lake, Oregon, United States
• Alkali Lake, British Columbia and the adjoining reserves of the Alkali Lake Indian Band are named for a local Alkali Lake, which got its name from a large patch of alkali on the hillside above the lake, which is not itself alkali,^[1] although there are many in the Cariboo district and adjoining regions of the British Columbia Interior.

In chemistry, an alkali (from Arabic: Al-Qaly القلي, القالي ) is a basic, ionic salt of an alkali metal or alkaline earth metal element. Alkalis are best known for being bases that dissolve in water. Bases are compounds with a pH greater than 7. The adjective alkaline is commonly used in English as a synonym for base, especially for soluble bases. This broad use of the term is likely to have come about because alkalis were the first bases known to obey the Arrhenius definition of a base and are still among the more common bases. Since Brønsted-Lowry acid-base theory, the term alkali in chemistry is normally restricted to those salts containing alkali and alkaline earth metal elements.

Etymology

The word "alkali" is derived from Arabic al qalīy = the calcined ashes, referring to the original source of alkaline substance. Ashes were used in conjunction with animal fat to produce soap, a process known as saponification.

Common properties

Alkalis are all Arrhenius bases, which form hydroxide ions (OH^-) when dissolved in water. Common properties of alkaline aqueous solutions include:

• Moderately-concentrated solutions (over 10^−3 M) have a pH of 7.1 or greater. This means that they will turn phenolphthalein from colorless to pink.
• Concentrated solutions are caustic (causing chemical burns).
• Alkaline solutions are slippery or soapy to the touch, due to the saponification of the fatty acids on the surface of the skin.
• Alkalis are normally water soluble, although some like barium carbonate are only soluble when reacting with an acidic aqueous solution.
• Acids and alkalis are measured on a pH scale
• Alkalis are commonly found in household cleaners and toothpaste

Confusion between alkali and base

The terms "base" and "alkali" are often used interchangeably, particularly outside of a scientific context, but they do not have the same meaning. While all alkaline solutions are basic, not all bases are alkaline. The following are common mistakes:

• The phrase "measuring the alkalinity of soil" is incorrect since the property measured is actually the pH (base property).
• Calling bases that are not alkalis, such as ammonia, alkaline (ammonia is a base but not an alkali).

Also, not all salts formed by alkali metals are alkaline; this designation applies only to those salts that are basic. And while most electropositive metal oxides are basic, only the soluble alkali metal and alkaline earth metal oxides can be correctly called alkalis.

This definition of an alkali as a basic salt of an alkali metal or alkaline earth metal is the most common, based on dictionary definitions [1][2], however conflicting definitions of the term alkali do exist. These include:

• Any base that is water-soluble and forms hydroxide ions [3][4]. In chemistry, this is more accurately called an Arrhenius base.

• The solution of a base in water [5]. This would be an Arrhenius base in solution.

• Name given by chemists to an important group of subtances, the behaviour of bases the main alkali are 1,the hydroxides potassium 2,

Salts

Most basic salts are alkali salts, of which common examples are:

• sodium hydroxide (often called "caustic soda")
• potassium hydroxide (commonly called "caustic potash")
• lye (generic term, for either of the previous two, or even for a mixture)
• calcium carbonate (sometimes called "free lime")
• magnesium hydroxide is an example of an atypical alkali since it has low solubility in water (although the dissolved portion is considered a strong base due to complete dissociation of its ions).

Alkaline soil

Soil with a pH value higher than 7.3 is normally referred to as alkaline. This soil property can occur naturally, due to the presence of alkali salts. Although some plants do prefer slightly basic soil (including vegetables like cabbage and fodder like buffalograss), most plants prefer a mildly acidic soil (pH between 6.0 and 6.8), and alkaline soils can cause problems.

Lakes

In alkali lakes (a type of salt lake), evaporation concentrates the naturally-occurring alkali salts, often forming a crust of mildly-basic salt across a large area.

Examples of alkali lakes:

• Redberry Lake, Saskatchewan, Canada.
• Tramping Lake, Saskatchewan, Canada.
• Mono lake, California, United States
• Summer Lake, Oregon, United States
• Alkali Lake, British Columbia and the adjoining reserves of the Alkali Lake Indian Band are named for a local Alkali Lake, which got its name from a large patch of alkali on the hillside above the lake, which is not itself alkali,^[1] although there are many in the Cariboo district and adjoining regions of the British Columbia Interior.

In typical usage, water refers only to its liquid form or state, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam. Water covers 71% of the Earth's surface^[2]. On Earth, it is found mostly in oceans and other large water bodies, with 1.6% of water below ground in aquifers and 0.001% in the air as vapor, clouds (formed of solid and liquid water particles suspended in air), and precipitation.^[3] Oceans hold 97% of surface water, glaciers and polar ice caps 2.4%, and other land surface water such as rivers, lakes and ponds 0.6%. A very small amount of the Earth's water is contained within biological bodies and manufactured products.

Water on Earth moves continually through a cycle of evaporation or transpiration (evapotranspiration), precipitation, and runoff, usually reaching the sea. Over land, evaporation and transpiration contribute to the precipitation over land.

Clean, fresh drinking water is essential to human and other lifeforms. Access to safe drinking water has improved steadily and substantially over the last decades in almost every part of the world.^[4][5] There is a clear correlation between access to safe water and GDP per capita.^[6] However, some observers have estimated that by 2025 more than half of the world population will be facing water-based vulnerability.^[7] A recent report (November 2009) suggests that by 2030, in some developing regions of the world, water demand will exceed supply by 50%.^[8] Water plays an important role in the world economy, as it functions as a solvent for a wide variety of chemical substances and facilitates industrial cooling and transportation. Approximately 70% of freshwater is consumed by agriculture.^[9]

Chemical and physical properties

Water is the chemical substance with chemical formula H₂O: one molecule of water has two hydrogen atoms covalently bonded to a single oxygen atom.

Water appears in nature in all three common states of matter and may take many different forms on Earth: water vapor and clouds in the sky; seawater and icebergs in the polar oceans; glaciers and rivers in the mountains; and the liquid in aquifers in the ground.

The major chemical and physical properties of water are:

• Water is a tasteless, odorless liquid at standard temperature and pressure. The color of water and ice is, intrinsically, a very light blue hue, although water appears colorless in small quantities. Ice also appears colorless, and water vapor is essentially invisible as a gas.^[10]

• Water is transparent, and thus aquatic plants can live within the water because sunlight can reach them. Only strong UV light is slightly absorbed.

• Since the water molecule is not linear and the oxygen atom has a higher electronegativity than hydrogen atoms, it carries a slight negative charge, whereas the hydrogen atoms are slightly positive. As a result, water is a polar molecule with an electrical dipole moment. The net interactions between the dipoles on each molecule cause an effective skin effect at the interface of water with other substances, or air at the surface, the latter given rise to water's high surface tension. This dipolar nature contributes to water molecules' tendency to form hydrogen bonds which cause water's many special properties.^[11] The polar nature also favors adhesion to other materials.

• Each hydrogen nucleus is bound to the central oxygen atom by a pair of electrons that are shared between them; chemists call this shared electron pair a covalent chemical bond. In H₂O, only two of the six outer-shell electrons of oxygen are used for this purpose, leaving four electrons which are organized into two non-bonding pairs. The four electron pairs surrounding the oxygen tend to arrange themselves as far from each other as possible in order to minimize repulsions between these clouds of negative charge. This would ordinarily result in a tetrahedral geometry in which the angle between electron pairs (and therefore the H-O-H bond angle) is 109.5°. However, because the two non-bonding pairs remain closer to the oxygen atom, these exert a stronger repulsion against the two covalent bonding pairs, effectively pushing the two hydrogen atoms closer together. The result is a distorted tetrahedral arrangement in which the H-O-H angle is 104.5°. ^[12]

• A result of interplay of these properties, Capillary action refers to the tendency of water to move up a narrow tube against the force of gravity. This property is relied upon by all vascular plants, such as trees.

• Water is a good solvent and is often referred to as the universal solvent. Substances that dissolve in water, e.g., salts, sugars, acids, alkalis, and some gases – especially oxygen, carbon dioxide (carbonation) are known as hydrophilic (water-loving) substances, while those that do not mix well with water (e.g., fats and oils), are known as hydrophobic (water-fearing) substances.

• All the major components in cells (proteins, DNA and polysaccharides) are also dissolved in water.

• Pure water has a low electrical conductivity, but this increases significantly with the dissolution of a small amount of ionic material such as sodium chloride.

• The boiling point of water (and all other liquids) is dependent on the barometric pressure. For example, on the top of Mt. Everest water boils at about 68 °C (154 °F), compared to 100 °C (212 °F) at sea level. Conversely, water deep in the ocean near geothermal vents can reach temperatures of hundreds of degrees and remain liquid.

• Water has the second highest specific heat capacity of any known substance, after ammonia, as well as a high heat of vaporization (40.65 kJ·mol^−1), both of which are a result of the extensive hydrogen bonding between its molecules. These two unusual properties allow water to moderate Earth's climate by buffering large fluctuations in temperature.

• The maximum density of water occurs at 3.98 °C (39.16 °F).^[13] Water becomes even less dense upon freezing, expanding 9%. This results in an unusual phenomenon: water's solid form, ice, floats upon water, allowing organisms to survive inside a partially-frozen water body because the water on the bottom has a temperature of around 4 °C (39 °F).

• Water is miscible with many liquids, such as ethanol, in all proportions, forming a single homogeneous liquid. On the other hand, water and most oils are immiscible usually forming layers according to increasing density from the top. As a gas, water vapor is completely miscible with air.

• Water forms an azeotrope with many other solvents.

• Water can be split by electrolysis into hydrogen and oxygen.

• As an oxide of hydrogen, water is formed when hydrogen or hydrogen-containing compounds burn or react with oxygen or oxygen-containing compounds. Water is not a fuel, it is an end-product of the combustion of hydrogen. The energy required to split water into hydrogen and oxygen by electrolysis or any other means is greater than the energy released when the hydrogen and oxygen recombine.^[14]

• Elements which are more electropositive than hydrogen such as lithium, sodium, calcium, potassium and caesium displace hydrogen from water, forming hydroxides. Being a flammable gas, the hydrogen given off is dangerous and the reaction of water with the more electropositive of these elements may be violently explosive.

Taste and odor

Water can dissolve many different substances, giving it varying tastes and odors. Humans and other animals have developed senses which (more or less) enable them to evaluate the potability of water by avoiding water that is too salty or putrid. Humans also tend to prefer cold water to lukewarm water since cold water is likely to contain fewer microbes. The taste advertised in spring water or mineral water derives from the minerals dissolved in it: Pure H₂O is tasteless and odorless. The advertised purity of spring and mineral water refers to absence of toxins, pollutants and microbes.

Distribution of water in nature

Water in the universe

Much of the universe's water may be produced as a byproduct of star formation. When stars are born, their birth is accompanied by a strong outward wind of gas and dust. When this outflow of material eventually impacts the surrounding gas, the shock waves that are created compress and heat the gas. The water observed is quickly produced in this warm dense gas.^[15]

Water has been detected in interstellar clouds within our galaxy, the Milky Way. Water probably exists in abundance in other galaxies, too, because its components, hydrogen and oxygen, are among the most abundant elements in the universe. Interstellar clouds eventually condense into solar nebulae and solar systems such as ours.

Water vapor is present in:

• Atmosphere of Mercury: 3.4%, and large amounts of water in Mercury's exosphere^[16]
• Atmosphere of Venus: 0.002%
• Earth's atmosphere: ~0.40% over full atmosphere, typically 1%-4% at surface
• Atmosphere of Mars: 0.03%
• Atmosphere of Jupiter: 0.0004%
• Atmosphere of Saturn - in ices only
• Enceladus (moon of Saturn): 91%
• exoplanets known as HD 189733 b^[17] and HD 209458 b.^[18]

Liquid water is present on:

• Earth - 71% of surface
• Moon - small amounts of water have been found (in 2008) in the inside of volcanic pearls brought from Moon to Earth by the Apollo 15 crew in 1971.^[19] NASA reported the detection of water molecules by NASA's Moon Mineralogy Mapper aboard the Indian Space Research Organization's Chandrayaan-1 spacecraft in September 2009.^[20]

Strong evidence suggests that liquid water is present just under the surface of Saturn's moon Enceladus and on Jupiter's moon Europa where it may exist as a 100 km deep ocean covering the whole moon which would amount to more water than is in all the Earth's oceans.

Water ice is present on:

• Earth - mainly as ice sheets
• polar ice caps on Mars
• Moon
• Titan
• Europa
• Saturn's rings ^[21]
• Enceladus
• Pluto and Charon^[22]
• Comets and comet source populations (Kuiper belt and Oort cloud objects).

Water ice may be present on Ceres and Tethys. Water and other volatiles probably comprise much of the internal structures of Uranus and Neptune.

Water and habitable zone

The existence of liquid water, and to a lesser extent its gaseous and solid forms, on Earth are vital to the existence of life on Earth as we know it. The Earth is located in the habitable zone of the solar system; if it were slightly closer to or further from the Sun (about 5%, or about 8 million kilometers), the conditions which allow the three forms to be present simultaneously would be far less likely to exist.^[23][24]

Earth's gravity allows it to hold an atmosphere. Water vapor and carbon dioxide in the atmosphere provide a temperature buffer (greenhouse effect) which helps maintain a relatively steady surface temperature. If Earth were smaller, a thinner atmosphere would allow temperature extremes, thus preventing the accumulation of water except in polar ice caps (as on Mars).

The surface temperature of Earth has been relatively constant through geologic time despite varying levels of incoming solar radiation (insolation), indicating that a dynamic process governs Earth's temperature via a combination of greenhouse gases and surface or atmospheric albedo. This proposal is known as the Gaia hypothesis.

The state of water on a planet depends on ambient pressure, which is determined by the planet's gravity. If a planet is sufficiently massive, the water on it may be solid even at high temperatures, because of the high pressure caused by gravity.

There are various theories about origin of water on Earth.

Water on Earth

Hydrology is the study of the movement, distribution, and quality of water throughout the Earth. The study of the distribution of water is hydrography. The study of the distribution and movement of groundwater is hydrogeology, of glaciers is glaciology, of inland waters is limnology and distribution of oceans is oceanography. Ecological processes with hydrology are in focus of ecohydrology.

The collective mass of water found on, under, and over the surface of a planet is called the hydrosphere. Earth's approximate water volume (the total water supply of the world) is 1,360,000,000 km³ (326,000,000 mi³).

Groundwater and fresh water are useful or potentially useful to humans as water resources.

Liquid water is found in bodies of water, such as an ocean, sea, lake, river, stream, canal, pond, or puddle. The majority of water on Earth is sea water. Water is also present in the atmosphere in solid, liquid, and vapor states. It also exists as groundwater in aquifers.

Water is important in many geological processes. Groundwater is ubiquitous in rocks, and the pressure of this groundwater affects patterns of faulting. Water in the mantle is responsible for the melt that produces volcanoes at subduction zones. On the surface of the Earth, water is important in both chemical and physical weathering processes. Water and, to a lesser but still significant extent, ice, are also responsible for a large amount of sediment transport that occurs on the surface of the earth. Deposition of transported sediment forms many types of sedimentary rocks, which make up the geologic record of Earth history.

Water cycle

The water cycle (known scientifically as the hydrologic cycle) refers to the continuous exchange of water within the hydrosphere, between the atmosphere, soil water, surface water, groundwater, and plants.

Water moves perpetually through each of these regions in the water cycle consisting of following transfer processes:

• evaporation from oceans and other water bodies into the air and transpiration from land plants and animals into air.
• precipitation, from water vapor condensing from the air and falling to earth or ocean.
• runoff from the land usually reaching the sea.

Most water vapor over the oceans returns to the oceans, but winds carry water vapor over land at the same rate as runoff into the sea, about 36 Tt per year. Over land, evaporation and transpiration contribute another 71 Tt per year. Precipitation, at a rate of 107 Tt per year over land, has several forms: most commonly rain, snow, and hail, with some contribution from fog and dew. Condensed water in the air may also refract sunlight to produce rainbows.

Water runoff often collects over watersheds flowing into rivers. A mathematical model used to simulate river or stream flow and calculate water quality parameters is hydrological transport model. Some of water is diverted to irrigation for agriculture. Rivers and seas offer opportunity for travel and commerce. Through erosion, runoff shapes the environment creating river valleys and deltas which provide rich soil and level ground for the establishment of population centers. A flood occurs when an area of land, usually low-lying, is covered with water. It is when a river overflows its banks or flood from the sea. A drought is an extended period of months or years when a region notes a deficiency in its water supply. This occurs when a region receives consistently below average precipitation.

Fresh water storage

Some runoff water is trapped for periods of time, for example in lakes. At high altitude, during winter, and in the far north and south, snow collects in ice caps, snow pack and glaciers. Water also infiltrates the ground and goes into aquifers. This groundwater later flows back to the surface in springs, or more spectacularly in hot springs and geysers. Groundwater is also extracted artificially in wells. This water storage is important, since clean, fresh water is essential to human and other land-based life. In many parts of the world, it is in short supply.

Sea water

Sea water contains about 3.5% salt on average, plus smaller amounts of other substances. The physical properties of sea water differ from fresh water in some important respects. It freezes at a lower temperature (about -1.9C) and its density increases with decreasing temperature to the freezing point, instead of reaching maximum density at a temperature above freezing. The salinity of water in major seas varies from about 0.7% in the Baltic Sea to 4.0% in the Red Sea.

Tides

Tides are the cyclic rising and falling of Earth's ocean surface caused by the tidal forces of the Moon and the Sun acting on the oceans. Tides cause changes in the depth of the marine and estuarine water bodies and produce oscillating currents known as tidal streams. The changing tide produced at a given location is the result of the changing positions of the Moon and Sun relative to the Earth coupled with the effects of Earth rotation and the local bathymetry. The strip of seashore that is submerged at high tide and exposed at low tide, the intertidal zone, is an important ecological product of ocean tides.

Effects on life

From a biological standpoint, water has many distinct properties that are critical for the proliferation of life that set it apart from other substances. It carries out this role by allowing organic compounds to react in ways that ultimately allow replication. All known forms of life depend on water. Water is vital both as a solvent in which many of the body's solutes dissolve and as an essential part of many metabolic processes within the body. Metabolism is the sum total of anabolism and catabolism. In anabolism, water is removed from molecules (through energy requiring enzymatic chemical reactions) in order to grow larger molecules (e.g. starches, triglycerides and proteins for storage of fuels and information). In catabolism, water is used to break bonds in order to generate smaller molecules (e.g. glucose, fatty acids and amino acids to be used for fuels for energy use or other purposes). Water is thus essential and central to these metabolic processes. Therefore, without water, these metabolic processes would cease to exist, leaving us to muse about what processes would be in its place, such as gas absorption, dust collection, etc.

Water is also central to photosynthesis and respiration. Photosynthetic cells use the sun's energy to split off water's hydrogen from oxygen. Hydrogen is combined with CO₂ (absorbed from air or water) to form glucose and release oxygen. All living cells use such fuels and oxidize the hydrogen and carbon to capture the sun's energy and reform water and CO₂ in the process (cellular respiration).

Water is also central to acid-base neutrality and enzyme function. An acid, a hydrogen ion (H⁺, that is, a proton) donor, can be neutralized by a base, a proton acceptor such as hydroxide ion (OH^−) to form water. Water is considered to be neutral, with a pH (the negative log of the hydrogen ion concentration) of 7. Acids have pH values less than 7 while bases have values greater than 7.

Stomach acid (HCl) is useful to digestion. However, its corrosive effect on the esophagus during reflux can temporarily be neutralized by ingestion of a base such as aluminum hydroxide to produce the neutral molecules water and the salt aluminum chloride. Human biochemistry that involves enzymes usually performs optimally around a biologically neutral pH of 7.4.

For example, a cell of Escherichia coli contains 70% of water, a human body 60–70%, plant body up to 90% and the body of an adult jellyfish is made up of 94–98% water.

Aquatic life forms

Earth's waters are filled with life. The earliest life forms appeared in water; nearly all fish live exclusively in water, and there are many types of marine mammals, such as dolphins and whales that also live in the water. Some kinds of animals, such as amphibians, spend portions of their lives in water and portions on land. Plants such as kelp and algae grow in the water and are the basis for some underwater ecosystems. Plankton is generally the foundation of the ocean food chain.

Aquatic animals must obtain oxygen to survive, and they do so in various ways. Fish have gills instead of lungs, although some species of fish, such as the lungfish, have both. Marine mammals, such as dolphins, whales, otters, and seals need to surface periodically to breathe air. Smaller life forms are able to absorb oxygen through their skin.

Effects on human civilization

Civilization has historically flourished around rivers and major waterways; Mesopotamia, the so-called cradle of civilization, was situated between the major rivers Tigris and Euphrates; the ancient society of the Egyptians depended entirely upon the Nile. Large metropolises like Rotterdam, London, Montreal, Paris, New York City, Buenos Aires, Shanghai, Tokyo, Chicago, and Hong Kong owe their success in part to their easy accessibility via water and the resultant expansion of trade. Islands with safe water ports, like Singapore, have flourished for the same reason. In places such as North Africa and the Middle East, where water is more scarce, access to clean drinking water was and is a major factor in human development.

Health and pollution

Water fit for human consumption is called drinking water or potable water. Water that is not potable can be made potable by filtration or distillation (heating it until it becomes water vapor, and then capturing the vapor without any of the impurities it leaves behind), or by other methods (chemical or heat treatment that kills bacteria). Sometimes the term safe water is applied to potable water of a lower quality threshold (i.e., it is used effectively for nutrition in humans that have weak access to water cleaning processes, and does more good than harm). Water that is not fit for drinking but is not harmful for humans when used for swimming or bathing is called by various names other than potable or drinking water, and is sometimes called safe water, or "safe for bathing". Chlorine is a skin and mucous membrane irritant that is used to make water safe for bathing or drinking. Its use is highly technical and is usually monitored by government regulations (typically 1 part per million (ppm) for drinking water, and 1–2 ppm of chlorine not yet reacted with impurities for bathing water).

This natural resource is becoming scarcer in certain places, and its availability is a major social and economic concern. Currently, about a billion people around the world routinely drink unhealthy water. Most countries accepted the goal of halving by 2015 the number of people worldwide who do not have access to safe water and sanitation during the 2003 G8 Evian summit.^[25] Even if this difficult goal is met, it will still leave more than an estimated half a billion people without access to safe drinking water and over a billion without access to adequate sanitation. Poor water quality and bad sanitation are deadly; some five million deaths a year are caused by polluted drinking water. The World Health Organization estimates that safe water could prevent 1.4 million child deaths from diarrhea each year.^[26] Water, however, is not a finite resource, but rather re-circulated as potable water in precipitation in quantities many degrees of magnitude higher than human consumption. Therefore, it is the relatively small quantity of water in reserve in the earth (about 1% of our drinking water supply, which is replenished in aquifers around every 1 to 10 years), that is a non-renewable resource, and it is, rather, the distribution of potable and irrigation water which is scarce, rather than the actual amount of it that exists on the earth. Water-poor countries use importation of goods as the primary method of importing water (to leave enough for local human consumption), since the manufacturing process uses around 10 to 100 times products' masses in water.

In the developing world, 90% of all wastewater still goes untreated into local rivers and streams.^[27] Some 50 countries, with roughly a third of the world’s population, also suffer from medium or high water stress, and 17 of these extract more water annually than is recharged through their natural water cycles.^[28] The strain not only affects surface freshwater bodies like rivers and lakes, but it also degrades groundwater resources.

Human uses

Agriculture

The most important use of water in agriculture is for irrigation, which is a key component to produce enough food. Irrigation takes up to 90% of water withdrawn in some developing countries^[29] and significant proportions in more economically developed countries (United States, 30% of freshwater usage is for irrigation).^[30]

Water as a scientific standard

On 7 April 1795, the gram was defined in France to be equal to "the absolute weight of a volume of pure water equal to a cube of one hundredth of a meter, and to the temperature of the melting ice."^[31] For practical purposes though, a metallic reference standard was required, one thousand times more massive, the kilogram. Work was therefore commissioned to determine precisely the mass of one liter of water. In spite of the fact that the decreed definition of the gram specified water at 0 °C—a highly reproducible temperature—the scientists chose to redefine the standard and to perform their measurements at the temperature of highest water density, which was measured at the time as 4 °C (39 °F).^[32]

The Kelvin temperature scale of the SI system is based on the triple point of water, defined as exactly 273.16 K or 0.01 °C. The scale is a more accurate development of the Celsius temperature scale, which was originally defined according the boiling point (set to 100 °C) and melting point (set to 0 °C) of water.

Natural water consists mainly of the isotopes hydrogen-1 and oxygen-16, but there is also small quantity of heavier isotopes such as hydrogen-2 (deuterium). The amount of deuterium oxides or heavy water is very small, but it still affects the properties of water. Water from rivers and lakes tends to contain less deuterium than seawater. Therefore, standard water is defined in the Vienna Standard Mean Ocean Water specification.

For drinking

The human body is anywhere from 55% to 78% water depending on body size.^[33] To function properly, the body requires between one and seven liters of water per day to avoid dehydration; the precise amount depends on the level of activity, temperature, humidity, and other factors. Most of this is ingested through foods or beverages other than drinking straight water. It is not clear how much water intake is needed by healthy people, though most advocates agree that 6–7 glasses of water (approximately 2 liters) daily is the minimum to maintain proper hydration.^[34] Medical literature favors a lower consumption, typically 1 liter of water for an average male, excluding extra requirements due to fluid loss from exercise or warm weather.^[35] For those who have healthy kidneys, it is rather difficult to drink too much water, but (especially in warm humid weather and while exercising) it is dangerous to drink too little. People can drink far more water than necessary while exercising, however, putting them at risk of water intoxication (hyperhydration), which can be fatal. The "fact" that a person should consume eight glasses of water per day cannot be traced back to a scientific source.^[36] There are other myths such as the effect of water on weight loss and constipation that have been dispelled.^[37]

An original recommendation for water intake in 1945 by the Food and Nutrition Board of the National Research Council read: "An ordinary standard for diverse persons is 1 milliliter for each calorie of food. Most of this quantity is contained in prepared foods."^[38] The latest dietary reference intake report by the United States National Research Council in general recommended (including food sources): 2.7 liters of water total for women and 3.7 liters for men.^[39] Specifically, pregnant and breastfeeding women need additional fluids to stay hydrated. According to the Institute of Medicine—who recommend that, on average, women consume 2.2 liters and men 3.0 liters—this is recommended to be 2.4 liters (10 cups) for pregnant women and 3 liters (12 cups) for breastfeeding women since an especially large amount of fluid is lost during nursing.^[40] Also noted is that normally, about 20% of water intake comes from food, while the rest comes from drinking water and beverages (caffeinated included). Water is excreted from the body in multiple forms; through urine and faeces, through sweating, and by exhalation of water vapor in the breath. With physical exertion and heat exposure, water loss will increase and daily fluid needs may increase as well.

Humans require water that does not contain too many impurities. Common impurities include metal salts and oxides (including copper, iron, calcium and lead)^[41] and/or harmful bacteria, such as Vibrio. Some solutes are acceptable and even desirable for taste enhancement and to provide needed electrolytes.^[42]

The single largest freshwater resource suitable for drinking is Lake Baikal in Siberia, which has a very low salt and calcium content and is therefore very clean.

Hygiene

The ability of water to make solutions and emulsions is used for washing. Many industrial processes rely on reactions using chemicals dissolved in water, suspension of solids in water slurries or using water to dissolve and extract substances.

Chemical uses

Water is widely used in chemical reactions as a solvent or reactant and less commonly as a solute or catalyst. In inorganic reactions, water is a common solvent, dissolving many ionic compounds. In organic reactions, it is not usually used as a reaction solvent, because it does not dissolve the reactants well and is amphoteric (acidic and basic) and nucleophilic. Nevertheless, these properties are sometimes desirable. Also, acceleration of Diels-Alder reactions by water has been observed. Supercritical water has recently been a topic of research. Oxygen-saturated supercritical water combusts organic pollutants efficiently.

As a heat transfer fluid

Water and steam are used as heat transfer fluids in diverse heat exchange systems, due to its availability and high heat capacity, both as a coolant and for heating. Cool water may even be naturally available from a lake or the sea. Condensing steam is a particularly efficient heating fluid because of the large heat of vaporization. A disadvantage is that water and steam are somewhat corrosive. In almost all electric power stations, water is the coolant, which vaporizes and drives steam turbines to drive generators. In the U.S., cooling power plants is the largest use of water.^[30]

In the nuclear industry, water can also be used as a neutron moderator. In a pressurized water reactor, water is both a coolant and a moderator. This provides a passive safety measure, as removing the water from the reactor also slows the nuclear reaction down.

Extinguishing fires

Water has a high heat of vaporization and is relatively inert, which makes it a good fire extinguishing fluid. The evaporation of water carries heat away from the fire. However, water cannot be used to fight fires of electric equipment, because impure water is electrically conductive, or of oils and organic solvents, because they float on water and the explosive boiling of water tends to spread the burning liquid.

Use of water in fire fighting should also take into account the hazards of a steam explosion, which may occur when water is used on very hot fires in confined spaces, and of a hydrogen explosion, when substances which react with water, such as certain metals or hot graphite, decompose the water, producing hydrogen gas.

The power of such explosions was seen in the Chernobyl disaster, although the water involved did not come from fire-fighting at that time but the reactor's own water cooling system. A steam explosion occurred when the extreme over-heating of the core caused water to flash into steam. A hydrogen explosion may have occurred as a result of reaction between steam and hot zirconium.

Recreation

Humans use water for many recreational purposes, as well as for exercising and for sports. Some of these include swimming, waterskiing, boating, surfing and diving. In addition, some sports, like ice hockey and ice skating, are played on ice. Lakesides, beaches and waterparks are popular places for people to go to relax and enjoy recreation. Many find the sound and appearance of flowing water to be calming, and fountains and other water features in public or private decorations.. Some keep fish and other life in aquariums or ponds for show, fun, and companionship. Humans also use water for snow sports i.e. skiing, sledding, snowmobiling or snowboarding, which requires the water to be frozen. People may also use water for play fighting such as with snowballs, water guns or water balloons.

Water industry

The water industry provides drinking water and wastewater services (including sewage treatment) to households and industry. Water supply facilities include water wells cisterns for rainwater harvesting, water supply network, water purification facilities, water tanks, water towers, water pipes including old aqueducts. Atmospheric water generators are in development.

Drinking water is often collected at springs, extracted from artificial borings (wells) in the ground, or pumped from lakes and rivers. Building more wells in adequate places is thus a possible way to produce more water, assuming the aquifers can supply an adequate flow. Other water sources include rainwater collection. Water may require purification for human consumption. This may involve removal of undissolved substances, dissolved substances and harmful microbes. Popular methods are filtering with sand which only removes undissolved material, while chlorination and boiling kill harmful microbes. Distillation does all three functions. More advanced techniques exist, such as reverse osmosis. Desalination of abundant seawater is a more expensive solution used in coastal arid climates.

The distribution of drinking water is done through municipal water systems, tanker delivery or as bottled water. Governments in many countries have programs to distribute water to the needy at no charge. Others argue that the market mechanism and free enterprise are best to manage this rare resource and to finance the boring of wells or the construction of dams and reservoirs.

Reducing usage by using drinking (potable) water only for human consumption is another option. In some cities such as Hong Kong, sea water is extensively used for flushing toilets citywide in order to conserve fresh water resources.

Polluting water may be the biggest single misuse of water; to the extent that a pollutant limits other uses of the water, it becomes a waste of the resource, regardless of benefits to the polluter. Like other types of pollution, this does not enter standard accounting of market costs, being conceived as externalities for which the market cannot account. Thus other people pay the price of water pollution, while the private firms' profits are not redistributed to the local population victim of this pollution. Pharmaceuticals consumed by humans often end up in the waterways and can have detrimental effects on aquatic life if they bioaccumulate and if they are not biodegradable.

Wastewater facilities are storm sewers and wastewater treatment plants. Another way to remove pollution from surface runoff water is bioswale.

Industrial applications

Water is used in power generation. Hydroelectricity is electricity obtained from hydropower. Hydroelectric power comes from water driving a water turbine connected to a generator. Hydroelectricity is a low-cost, non-polluting, renewable energy source. The energy is supplied by the sun. Heat from the sun evaporates water, which condenses as rain in higher altitudes, from where it flows down.

Pressurized water is used in water blasting and water jet cutters. Also, very high pressure water guns are used for precise cutting. It works very well, is relatively safe, and is not harmful to the environment. It is also used in the cooling of machinery to prevent over-heating, or prevent saw blades from over-heating.

Water is also used in many industrial processes and machines, such as the steam turbine and heat exchanger, in addition to its use as a chemical solvent. Discharge of untreated water from industrial uses is pollution. Pollution includes discharged solutes (chemical pollution) and discharged coolant water (thermal pollution). Industry requires pure water for many applications and utilizes a variety of purification techniques both in water supply and discharge.

Food processing

Water plays many critical roles within the field of food science. It is important for a food scientist to understand the roles that water plays within food processing to ensure the success of their products.

Solutes such as salts and sugars found in water affect the physical properties of water. The boiling and freezing points of water is affected by solutes. One mole of sucrose (sugar) per kilogram of water raises the boiling point of water by 0.51 °C, and one mole of salt per kg raises the boiling point by 1.02 °C; similarly, increasing the number of dissolved particles lowers water's freezing point.^[43] Solutes in water also affect water activity which affects many chemical reactions and the growth of microbes in food.^[44] Water activity can be described as a ratio of the vapor pressure of water in a solution to the vapor pressure of pure water.^[43] Solutes in water lower water activity. This is important to know because most bacterial growth ceases at low levels of water activity.^[44] Not only does microbial growth affect the safety of food but also the preservation and shelf life of food.

Water hardness is also a critical factor in food processing. It can dramatically affect the quality of a product as well as playing a role in sanitation. Water hardness is classified based on the amounts of removable calcium carbonate salt it contains per gallon. Water hardness is measured in grains; 0.064 g calcium carbonate is equivalent to one grain of hardness.^[43] Water is classified as soft if it contains 1 to 4 grains, medium if it contains 5 to 10 grains and hard if it contains 11 to 20 grains.^{[vague] [43]} The hardness of water may be altered or treated by using a chemical ion exchange system. The hardness of water also affects its pH balance which plays a critical role in food processing. For example, hard water prevents successful production of clear beverages. Water hardness also affects sanitation; with increasing hardness, there is a loss of effectiveness for its use as a sanitizer.^[43]

Boiling, steaming, and simmering are popular cooking methods that often require immersing food in water or its gaseous state, steam. Water is also used for dishwashing.

Water law, water politics and water crisis

Water politics is politics affected by water and water resources. For this reason, water is a strategic resource in the globe and an important element in many political conflicts. It causes health impacts and damage to biodiversity.

1.6 billion people have gained access to a safe water source since 1990 [1]. The proportion of people in developing countries with access to safe water is calculated to have improved from 30% in 1970^[4] to 71% in 1990, 79% in 2000 and 84% in 2004. This trend is projected to continue.^[5] To halve, by 2015, the proportion of people without sustainable access to safe drinking water is one of the Millennium Development Goals. This goal is projected to be reached.

A 2006 United Nations report stated that "there is enough water for everyone", but that access to it is hampered by mismanagement and corruption.^[45]

The UN World Water Development Report (WWDR, 2003) from the World Water Assessment Program indicates that, in the next 20 years, the quantity of water available to everyone is predicted to decrease by 30%. 40% of the world's inhabitants currently have insufficient fresh water for minimal hygiene. More than 2.2 million people died in 2000 from waterborne diseases (related to the consumption of contaminated water) or drought. In 2004, the UK charity WaterAid reported that a child dies every 15 seconds from easily preventable water-related diseases; often this means lack of sewage disposal; see toilet.

Organizations concerned with water protection include International Water Association (IWA), WaterAid, Water 1st, American Water Resources Association. Water related conventions are United Nations Convention to Combat Desertification (UNCCD), International Convention for the Prevention of Pollution from Ships, United Nations Convention on the Law of the Sea and Ramsar Convention. World Day for Water takes place on 22 March and World Ocean Day on 8 June.

Water used in the production of a good or service is virtual water.

Water in culture

Religion

Water is considered a purifier in most religions. Major faiths that incorporate ritual washing (ablution) include Christianity, Hinduism, Rastafari movement, Islam, Shinto, Taoism, and Judaism. Immersion (or aspersion or affusion) of a person in water is a central sacrament of Christianity (where it is called baptism); it is also a part of the practice of other religions, including Judaism (mikvah) and Sikhism (Amrit Sanskar). In addition, a ritual bath in pure water is performed for the dead in many religions including Judaism and Islam. In Islam, the five daily prayers can be done in most cases (see Tayammum) after completing washing certain parts of the body using clean water (wudu). In Shinto, water is used in almost all rituals to cleanse a person or an area (e.g., in the ritual of misogi). Water is mentioned in the Bible 442 times in the New International Version and 363 times in the King James Version: 2 Peter 3:5(b) states, "The earth was formed out of water and by water" (NIV). In the Koran it is stated that "Living things are made of water" and it is often used to described Paradise.

Philosophy

The Ancient Greek philosopher Empedocles held that water is one of the four classical elements along with fire, earth and air, and was regarded as the ylem, or basic substance of the universe. Water was considered cold and moist. In the theory of the four bodily humors, water was associated with phlegm. The classical element of Water was also one of the five elements in traditional Chinese philosophy, along with earth, fire, wood, and metal.

Water is also taken as a role model in some parts of traditional and popular Asian philosophy. James Legge's 1891 translation of the Dao De Jing states "The highest excellence is like (that of) water. The excellence of water appears in its benefiting all things, and in its occupying, without striving (to the contrary), the low place which all men dislike. Hence (its way) is near to (that of) the Tao" and "There is nothing in the world more soft and weak than water, and yet for attacking things that are firm and strong there is nothing that can take precedence of it—for there is nothing (so effectual) for which it can be changed."^[46]

Literature

Water is used in literature as a symbol of purification. Examples include the critical importance of a river in As I Lay Dying by William Faulkner and the drowning of Ophelia in Hamlet.

Sherlock Holmes held that "From a drop of water, a logician could infer the possibility of an Atlantic or a Niagara without having seen or heard of one or the other."^[47]