In most areas of the United States, low levels of uranium are found in the drinking water. Higher levels may be found in areas with elevated levels of naturally occurring uranium in rocks and soil. The chemical effects of uranium in drinking water are of greater concern than the possible effects of its radioactivity. Bathing and showering with water that contains uranium is not a health concern. People who work at factories that process uranium, work with phosphate fertilizers, or live near uranium mines have a chance of taking in more uranium than most other people.
Larger-than-normal amounts of uranium might also enter the environment from erosion of tailings from mines and mills for uranium and other metals. Accidental discharges from uranium processing plants are possible, but these compounds spread out quickly into the air. EPA strongly encourages people to learn more about their drinking water, and to support local efforts to protect and upgrade the supply of safe drinking water. Your water bill or telephone book's government listings are a good starting point for local information.
Bromide can be found in fresh water supplies in sufficient concentrations to produce after ozonation more than 10 parts per billion ppb of bromate — the maximum contaminant level established by the USEPA. Ultraviolet light UV is very effective at inactivating cysts, in low turbidity water. UV light's disinfection effectiveness decreases as turbidity increases, a result of the absorption , scattering , and shadowing caused by the suspended solids. The main disadvantage to the use of UV radiation is that, like ozone treatment, it leaves no residual disinfectant in the water; therefore, it is sometimes necessary to add a residual disinfectant after the primary disinfection process.
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 few of the negative effects of chlorination. Over 2 million people in 28 developing countries use Solar Disinfection for daily drinking water treatment. Like UV, ionizing radiation X-rays, gamma rays, and electron beams has been used to sterilize water. Bromine and iodine can also be used as disinfectants. However, chlorine in water is over three times more effective as a disinfectant against Escherichia coli than an equivalent concentration of bromine , and over six times more effective than an equivalent concentration of iodine.
Potable water purification devices and methods are available for disinfection and treatment 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. 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. In April, , the water supply of Spencer, Massachusetts in the United States of America, became contaminated with excess sodium hydroxide lye when its treatment equipment malfunctioned. Many municipalities have moved from free chlorine to chloramine as a disinfection agent.
However, chloramine appears to be a corrosive agent in some water systems. Chloramine can dissolve the "protective" film inside older service lines, leading to the leaching of lead into residential spigots. This can result in harmful exposure, including elevated blood lead levels. Lead is a known neurotoxin. 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 Magnesium , calcium , and other minerals in water can help to protect against nutritional deficiency.
Why Filter Your Water?
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. Manufacturers of home water distillers claim the opposite—that minerals in water are the cause of many diseases, and that most beneficial minerals come from food, not water. The first experiments into water filtration were made in the 17th century.
Sir Francis Bacon attempted to desalinate sea water by passing the flow through a sand filter. Although his experiment did not succeed, it marked the beginning of a new interest in the field. The fathers of microscopy , Antonie van Leeuwenhoek and Robert Hooke , used the newly invented microscope to observe for the first time small material particles that lay suspended in the water, laying the groundwork for the future understanding of waterborne pathogens.
The first documented use of sand filters to purify the water supply dates to , when the owner of a bleachery in Paisley, Scotland , John Gibb, installed an experimental filter, selling his unwanted surplus to the public. The practice of water treatment soon became mainstream and common, and the virtues of the system were made starkly apparent after the investigations of the physician John Snow during the Broad Street cholera outbreak. Snow was sceptical of the then-dominant miasma theory that stated that diseases were caused by noxious "bad airs".
Although the germ theory of disease had not yet been developed, Snow's observations led him to discount the prevailing theory. His essay On the Mode of Communication of Cholera conclusively demonstrated the role of the water supply in spreading the cholera epidemic in Soho ,   with the use of a dot distribution map and statistical proof to illustrate the connection between the quality of the water source and cholera cases.
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His data convinced the local council to disable the water pump, which promptly ended the outbreak. The Metropolis Water Act introduced the regulation of the water supply companies in London , including minimum standards of water quality for the first time. The Act "made provision for securing the supply to the Metropolis of pure and wholesome water", and required that all water be "effectually filtered" from 31 December This legislation set a worldwide precedent for similar state public health interventions across Europe.
The Metropolitan Commission of Sewers was formed at the same time, water filtration was adopted throughout the country, and new water intakes on the Thames were established above Teddington Lock.
Water purification - Wikipedia
Automatic pressure filters, where the water is forced under pressure through the filtration system, were innovated in in England. John Snow was the first to successfully use chlorine to disinfect the water supply in Soho that had helped spread the cholera outbreak. William Soper also used chlorinated lime to treat the sewage produced by typhoid patients in In a paper published in , Moritz Traube formally proposed the addition of chloride of lime calcium hypochlorite to water to render it "germ-free.
Permanent water chlorination began in , when a faulty slow sand filter and a contaminated water supply led to a serious typhoid fever epidemic in Lincoln, England. Alexander Cruickshank Houston used chlorination of the water to stem the epidemic. His installation fed a concentrated solution of chloride of lime to the water being treated. The chlorination of the water supply helped stop the epidemic and as a precaution, the chlorination was continued until when a new water supply was instituted. The first continuous use of chlorine in the United States for disinfection took place in at Boonton Reservoir on the Rockaway River , which served as the supply for Jersey City, New Jersey.
The treatment process was conceived by Dr. John L. Leal and the chlorination plant was designed by George Warren Fuller.
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The technique of purification of drinking water by use of compressed liquefied chlorine gas was developed by a British officer in the Indian Medical Service , Vincent B. Nesfield, in According to his own account:. It occurred to me that chlorine gas might be found satisfactory The next important question was how to render the gas portable.
This might be accomplished in two ways: By liquefying it, and storing it in lead-lined iron vessels, having a jet with a very fine capillary canal, and fitted with a tap or a screw cap. The tap is turned on, and the cylinder placed in the amount of water required. The chlorine bubbles out, and in ten to fifteen minutes the water is absolutely safe. This method would be of use on a large scale, as for service water carts.
Shortly thereafter, Major William J. Lyster of the Army Medical Department used a solution of calcium hypochlorite in a linen bag to treat water. For many decades, Lyster's method remained the standard for U. This work became the basis for present day systems of municipal water purification. From Wikipedia, the free encyclopedia. This article is about large scale, municipal water purification.
For other uses, see Purification of water. Further information: Water supply.