Chlorinated water is the process of adding chlorine ( Cl
2 ) or hypochlorite to water. This method is used to kill certain bacteria and other microbes in tap water because chlorine is very toxic. In particular, chlorination is used to prevent the spread of waterborne diseases such as cholera, dysentery, and typhoid.
Video Water chlorination
History
In a paper published in 1894, it was formally proposed to add chlorine to water to make it "germ-free". Two other authorities supported this proposal and published it in many other papers in 1895. The initial attempt to apply water chlorination at a water treatment plant was made in 1893 in Hamburg, Germany. In 1897 the city of Maidstone, England was the first to have all its water supply processed with chlorine.
Permanent water chlorination began in 1905, when a slow sand filter was wrong and the contaminated water supply caused a serious epidemic of typhoid fever in Lincoln, England. Dr. Alexander Cruickshank Houston uses water chlorination to stop the epidemic. The installation gives a concentrated solution called lime chloride to the water being treated. It is not only modern calcium chloride, but it contains chlorine gas dissolved in lime water (aqueous calcium hydroxide) to form calcium hypochlorite (chlorinated lime). Chlorination of water supplies helped stop the epidemic and as a precautionary measure, chlorination continued until 1911 when new water supply was instituted.
The continuous use of chlorine in the United States for disinfection was done in 1908 at Boonton Reservoir (on the Rockaway River), which serves as a supply for Jersey City, New Jersey. Chlorination was achieved by additionally controlled aqueous chloride dilute solution (calcium hypochlorite) at a dose of 0.2-0.35 ppm. Treatment process conceived by Dr. John L. Leal, and chlorination plants designed by George Warren Fuller. Over the next few years, chlorine disinfection using chalk chloride (calcium hypochlorite) is rapidly installed in drinking water systems around the world.
The technique of purifying drinking water using liquid liquid chlorine gas was developed by a British officer in Indian Medical Services, Vincent B. Nesfield, in 1903. According to his own notes, "I am aware that chlorine gas may be found satisfactory... if the appropriate means can found to use it.... The next important question is how to make a portable gas.This can be achieved in two ways: By liquefying it, and storing it in tin-coated iron, the vessel, has a jet with a very smooth capillary channel, and equipped with a tap or the screw cap is turned on, and the cylinder is placed in the required amount of water, chlorine bubbles out, and within ten to fifteen minutes the water is completely safe.This method will be useful on a large scale, such as for service water carts.
Major Carl Rogers Darnall, Professor of Chemistry at the Army Medical School, gave this first practical demonstration in 1910. This work became the basis for the city's current water purification system . Shortly after Darnall's demonstration, Maj. William J. L. Lyster of the Army Medical Department used a calcium hypochlorite solution in a linen bag to treat water.
For decades, the Lyster method remained the standard for US ground forces in the field and in camps, implemented in the familiar Lyster Bag (also spelled Lister Bag). "Bags, water, sterilization" of canvas is a common component of field kitchens, published per 100 people, of a standard capacity of 36 gallons depending on the often-improvised tripods in the field. In the use of World War I through the Vietnam War, it has been replaced by a reverse osmosis system that produces drinking water by pressures suppressing local water through microscopic level filters: Reverse Osmosis Water Purification Unit (1980) and Tactical Water Purification System (2007) for scale production large and Light Air Purifier units for smaller scale needs that include ultrafiltration technology to generate drinking water from any source and use an automatic backwash cycle every 15 minutes to simplify cleaning operations.
Chlorine gas was first used sustainably to disinfect water supply at Belmont filter mill, Philadelphia, Pennsylvania using a machine invented by Charles Frederick Wallace dubbed Chlorinator. It's manufactured by Wallace & amp; The Tiernan Company started in 1913. In 1941, disinfection of US drinking water by chlorine gas has replaced the use of chloride chloride.
Chlorination can also be done using sodium hypochlorite or various other chemicals.
Maps Water chlorination
Biochemistry
As halogen, chlorine is a highly efficient disinfectant, and added to public water supplies to kill disease-causing pathogens, such as bacteria, viruses, and protozoa, which usually grow in water supply reservoirs, in plumbing walls and in storage tanks. Microscopic agents of many diseases such as cholera, typhoid fever, and dysentery kill many people each year before disinfection methods are used routinely.
Chlorine is made from salt by electrolysis or other methods. It is a gas at atmospheric pressure but melts under pressure. Liquid gas is transported and used as such.
As a strong oxidizing agent, chlorine kills through the oxidation of organic molecules. Chlorine and hydrolysis products are neutral charged hydrolysis and therefore readily penetrate the surface of negatively charged pathogens. It is able to break down lipids that form cell walls and react with intracellular enzymes and proteins, making them non-functional. The microorganisms then die or can no longer reproduce.
Principles
When dissolved in water, chlorine is converted into a mixture of chlorine equilibrium, hypochlorite acid (HOCl), and hydrochloric acid (HCl):
- Cl 2 H 2 O? HOCl HCl
In acidic solutions, the main species are Cl 2 and HOCl, whereas in an alkaline solution, effectively only ClO - (hypochlorite ion) is present. Very small ClO concentrations 2 - , ClO 3 - , ClO 4 < soup> - is also found.
Shock chlorination
Shock chlorination is a process used in many swimming pools, wells, springs, and other water sources to reduce residual bacteria and algae in the water. Chlorination of shock is done by mixing large amounts of hypochlorite into the water. Hypochlorite can be in the form of powders or liquids such as chlorine bleach (sodium hypochlorite or calcium hypochlorite solution in water). Water that is being feared should not enter or drink until the amount of sodium hypochlorite in water drops to three parts per million (PPM) or until the amount of calcium hypochlorite falls to 0.2 to 0.35 PPM.
Weakness
Disinfection by chlorination can be a problem, in some circumstances. Chlorine can react with natural organic compounds found in the water supply to produce compounds known as byproducts of disinfection (DBPs). The most common DBPs are trihalomethanes (THMs) and haloacetic acids (HAAs). Trihalomethanes are a major disinfectant byproduct made from chlorination with two different types, bromoform and dibromochloromethane, which are primarily responsible for the health hazards. The effect depends greatly on the duration of their exposure to chemicals and the amount ingested into the body. In high doses, bromoform primarily slows ordinary brain activity, which is manifested by symptoms such as drowsiness or sedation. Chronic exposure of both bromoform and dibromochloromethane can lead to liver and kidney cancer, as well as heart disease, unconsciousness, or death in high doses. Due to the potential carcinogenicity of these compounds, drinking water regulations throughout the developed world require regular monitoring of the concentrations of these compounds in the municipal water system distribution system. The World Health Organization has stated that "the health risks of these byproducts are very small compared to the risks associated with inadequate disinfection".
There are also other concerns about chlorine, including its volatile nature which causes it to disappear too quickly from the water system, and organoleptic problems such as taste and odor.
Alternate methods for water disinfection
Chlorine dioxide
The use of chlorine dioxide as an alternative to chlorine is now widespread in both urban and industrial applications. This eliminates the potential of harmful DBP and is a highly efficient disinfectant.
Ozonation
Ozonation is used by many European countries and also in some municipalities in the United States and Canada. This alternative is more cost effective but energy intensive. It involves ozone bubbling through water, destroying all parasites, bacteria, and all other harmful organic substances. However, this method leaves no residual ozone to control the contamination of water after the process is complete.
The advantage of chlorine compared to ozone is that the residue remains in water for long periods of time. This feature allows chlorine to travel through the water supply system, effectively controlling the contamination of backflow pathogens. In this large system may be inadequate, and chlorine levels may be increased at points in the distribution system, or chloramine may be used, which remain in the water longer before reacting or disappearing.
Chlorine
Chloramination is also becoming increasingly common. Disinfection with chloramine produces undesirable byproducts rather than chlorine (gas or hypochlorite). Chloramine has a longer half-life in the distribution system, and maintains an effective protection against pathogens. Chlorine remains in the distribution because its redox potential is lower than that of free chlorine. Chlorine is formed by adding ammonia and chlorine to the drinking water to form monochloramine and/or chlorine. While Helicobacter pylori can be more resistant to chlorine than Escherichia coli , both organisms are equally susceptible to the disinfectant effects of chloramine.
Bromination and iodination
Chlorine in water is more than three times as effective as a disinfectant against Escherichia coli than equivalent bromine concentrations, and more than six times more effective than equivalent iodine concentrations.
Home screening
Water treated by filtration and home filtration may not need further disinfection; the proportion of very high pathogens is removed by the materials in the filter bed. Filtered water should be used as soon as it is filtered, as the amount of microbes left can multiply over time. In general, this house filter removes more than 90% of the available chlorine for a glass of processed water. These filters should be replaced periodically otherwise bacterial content of water may increase due to bacterial growth in the filter unit.
UV radiation
UV disinfection is getting popular. UV treatment leaves minimal residue in the water. In UV water produces ozone in situ and thus has many advantages of ozone disinfection. However, irradiation of ultraviolet germs alone (as well as chlorination alone) will not remove toxins from bacteria, pesticides, heavy metals, etc. from water.
Ionizing radiation
Like UV, ionizing radiation (X-rays, gamma rays, and electron beams) has been used to sterilize water.
See also
- Drinking water
- Safe Drinking Water Act
- Sodium hypochlorite
- Sterilization (microbiology)
- Trichloroisocyanuric Acid a.k.a Symclosene, a chemical in chlorinated tablets
- Water filter
- Water Fluorine
- Water industry
- Water pollution
- Water purification
- Water supply network
- Water treatment
References
External links
- Milwaukee City, Wisconsin Water Works
- Emergency Disinfection from Drinking Water (US EPA)
- National Pollutant Inventory - Chlorine
- Alcoholic Beverages (IARC Monograph)
- NTP Study Report TR-392: Chlorinated & amp; Water Chloraminated (US NIH)
- The Chlorine Chemistry Division of the American Chemistry Council
- Disinfection Practices
- http://ukwta.org/
Source of the article : Wikipedia
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