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The hardness of the water results in a calcification
The hardness of the water results in a calcification

Hard water is a type of water that has high mineral content (in contrast with soft water). Water is a common Chemical substance that is essential for the survival of all known forms of Life. A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition a highly ordered atomic structure and specific Soft water the term used to describe types of Water that contain few or no Calcium or Magnesium metal cations. Hard water primarily consists of calcium (Ca2+), and magnesium (Mg2+) metal cations, and sometimes other dissolved compounds such as bicarbonates and sulfates. Calcium (ˈkælsiəm is the Chemical element with the symbol Ca and Atomic number 20 Magnesium (mægˈniːziəm is a Chemical element with the symbol Mg, Atomic number 12 Atomic weight 24 An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge In Inorganic chemistry, bicarbonate ( IUPAC -recommended nomenclature hydrogencarbonate) is an intermediate form in the Deprotonation Calcium usually enters the water as either calcium carbonate (CaCO3), in the form of limestone and chalk, or calcium sulfate (CaSO4), in the form of other mineral deposits. Limestone is a Sedimentary rock composed largely of the Mineral Calcite ( Calcium carbonate: CaCO3 Chalk (ʧɔːk is a soft white porous Sedimentary rock, a form of Limestone composed of the Mineral Calcite. Calcium sulfate is a common laboratory and industrial chemical The predominant source of magnesium is dolomite (CaMg(CO3)2). Dolomite (ˈdɒləmaɪt is the name of a Sedimentary Carbonate rock and a Mineral, both composed Hard water is generally not harmful.

The simplest way to determine the hardness of water is the lather/froth test: soap or toothpaste, when agitated, lathers easily in soft water but not in hard water. SOAP (see below for name and origins is a protocol for exchanging XML -based messages over Computer networks normally using Toothpaste is a Paste or Gel Dentifrice used to clean and maintain the aesthetics and health of Teeth. More exact measurements of hardness can be obtained through a wet titration. Titration is a common laboratory method of Quantitative chemical analysis that is used to determine the unknown Concentration of a known Reactant The total water 'hardness' (including both Ca2+ and Mg2+ ions) is read as parts per million or weight/volume (mg/L) of calcium carbonate (CaCO3) in the water. "Parts-per" notation is used especially in Science and Engineering, to denote Ratios (relative proportions in measured quantities particularly In Biology, percentage solutions are often preferred to molar ones Although water hardness usually only measures the total concentrations of calcium and magnesium (the two most prevalent, divalent metal ions), iron, aluminium, and manganese may also be present at elevated levels in some geographical locations. In chemistry divalent Anions are atoms or radicals with 2 additional Electrons when compared to their elemental state (that is with 2 more electrons than Protons Iron (ˈаɪɚn is a Chemical element with the symbol Fe (ferrum and Atomic number 26 WikipediaNaming Manganese (ˈmæŋgəniːz is a Chemical element, designated by the symbol Mn.

Contents

Hardness

Hardness in water is defined as the presence of multivalent cations. An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge Hardness in water can cause water to form scales and a resistance to soap. It can also be defined as water that doesn’t produce lather with soap solutions, but produces white precipitate (scum). Example :

2C17H35COONa + Ca++ → (C17H35COO)2Ca + 2Na+

Types of hard water

In the 1960's, scientist Chris Gilby discovered that hard water can be categorized by the ions found in the water. A distinction is also made between 'temporary' and 'permanent' hard water.

Temporary hardness

Temporary hardness is caused by a combination of calcium ions and bicarbonate ions in the water. It can be removed by boiling the water or by the addition of lime (calcium hydroxide). Lime is a general term for various naturally occurring Minerals and materials derived from them in which Carbonates Oxides and Hydroxides of Calcium hydroxide, traditionally called slaked lime, hydrated lime, or pickling lime, is a Chemical compound with the chemical formula Boiling promotes the formation of carbonate from the bicarbonate and precipitates calcium carbonate out of solution, leaving water that is softer upon cooling.

The following is the equilibrium reaction when calcium carbonate (CaCO3) is dissolved in water:

CaCO3(s) + H2CO3(aq) ⇋ Ca2+(aq) + 2HCO3-(aq)

Upon heating, less CO2 is able to dissolve into the water (see Solubility). Calcium carbonate is a Chemical compound with the Chemical formula Ca[[Carbon C]] O 3 Solubility is the characteristic Physical property referring to the ability of a given substance the Solute, to dissolve in a Solvent. Since there is not enough CO2 around, the reaction cannot proceed from left to right, and therefore the CaCO3 will not dissolve as rapidly. Instead, the reaction is forced to the left (i. e. products to reactants) to re-establish equilibrium, and solid CaCO3 is formed. Boiling the water will remove hardness as long as the solid CaCO3 that precipitates out is removed. After cooling, if enough time passes the water will pick up CO2 from the air and the reaction will again proceed from left to right, allowing the CaCO3 to "re-dissolve" into the water.

For more information on the solubility of calcium carbonate in water and how it is affected by atmospheric carbon dioxide, see calcium carbonate. Calcium carbonate is a Chemical compound with the Chemical formula Ca[[Carbon C]] O 3

Permanent hardness

Permanent hardness is hardness (mineral content) that cannot be removed by boiling. It is usually caused by the presence of calcium and magnesium sulfates and/or chlorides in the water, which become more soluble as the temperature rises. Despite the name, permanent hardness can be removed using a water softener or ion exchange column, where the calcium and magnesium ions are exchanged with the sodium ions in the column. A water softener reduces the dissolved Calcium, Magnesium, and to some degree Manganese and Ferrous iron ion concentration in Hard water


Hard water causes scaling, which is the left over mineral deposits that are formed after the hard water had evaporated. This is also known as limescale. Limescale is the hard off-white chalky deposit found in kettles hot-water boilers and the inside of inadequately maintained hot-water central heating systems The scale can clog pipes, ruin water heaters, coat the insides of tea and coffee pots, and decrease the life of toilet flushing units.

Similarly, insoluble salt residues that remain in hair after shampooing with hard water tend to leave hair rougher and harder to untangle. [1]

In industrial settings, water hardness must be constantly monitored to avoid costly breakdowns in boilers, cooling towers, and other equipment that comes in contact with water. A boiler is a closed vessel in which Water or other Fluid is heated Cooling towers are heat removal devices used to transfer process waste heat to the Atmosphere. Hardness is controlled by the addition of chemicals and by large-scale softening with zeolite and ion exchange resins. Zeolites (Greek zein, "to boil" lithos, "a stone" are hydrated Aluminosilicate Minerals and have a micro-porous structure ion-exchange resin is an insoluble matrix (or support structure normally in the form of small (1-2 mm diameter beads usually white or yellowish fabricated from an organic Polymer

Measurement

It is possible to measure the level of hard water by obtaining a free water testing kit. These are supplied by most water softening companies. There are several different scales used to describe the hardness of water in different contexts.

Because it is the precise mixture of minerals dissolved in the water, together with the water's pH and temperature, that determines the behaviour of the hardness, a single-number scale does not adequately describe hardness. Degrees of General Hardness (dGH is a unit of water hardness, specifically of General Hardness pH is the measure of the acidity or alkalinity of a Solution. Descriptions of hardness correspond roughly with ranges of mineral concentrations:

Indices

Several indices are used to describe the behaviour of calcium carbonate in water, oil, or gas mixtures. [2]

Langelier Saturation Index (LSI)

The Langelier Saturation Index (sometimes Langelier Stability Index) is a calculated number used to predict the calcium carbonate stability of water. It indicates whether the water will precipitate, dissolve, or be in equilibrium with calcium carbonate. Langelier developed a method for predicting the pH at which water is saturated in calcium carbonate (called pHs). The LSI is expressed as the difference between the actual system pH and the saturation pH.

LSI = pH - pHs

If the actual pH of the water is below the calculated saturation pH, the LSI is negative and the water has a very limited scaling potential. If the actual pH exceeds pHs, the LSI is positive, and being supersaturated with CaCO3, the water has a tendency to form scale. At increasing positive index values, the scaling potential increases.

Langelier saturation index is defined as:

LSI = pH (measured) - pHs


In practice, water with an LSI between -0. 5 and +0. 5 will not display enhanced mineral dissolving or scale forming properties. Water with an LSI below -0. 5 tends to exhibit noticeably increased dissolving abilities while water with an LSI above +0. 5 tends to exhibit noticeably increased scale forming properties.

It is also worth noting that the LSI is temperature sensitive. The LSI becomes more positive as the water temperature increases. This has particular implications in situations where well water is used. The temperature of the water when it first exits the well is often significantly lower than the temperature inside the building served by the well or at the laboratory where the LSI measurement is made.

Ryznar Stability Index (RSI)

The Ryznar stability index (RSI) uses a database of scale thickness measurements in municipal water systems to predict the effect of water chemistry.

Ryznar saturation index (RSI) was developed from empirical observations of corrosion rates and film formation in steel mains.

Ryznar saturation index is defined as:

RSI = 2 pHs – pH (measured)

Puckorius Scaling Index (PSI)

The Puckorius Scaling Index (PSI) uses slightly different parameters to quantify the relationship between the saturation state of the water and the amount of limescale deposited.

Other indices

Other indices include the Larson-Skold Index[3], the Stiff-Davis Index[4], and the Oddo-Tomson Index[5].

Health considerations

The World Health Organization says, "There does not appear to be any convincing evidence that water hardness causes adverse health effects in humans. "[6]

Some studies have shown a weak inverse relationship between water hardness and cardiovascular disease in men, up to a level of 170 mg calcium carbonate per litre of water. Cardiovascular disease or cardiovascular diseases refers to the class of diseases that involve the Heart or Blood vessels ( arteries and The World Health Organization has reviewed the evidence and concluded the data were inadequate to allow for a recommendation for a level of hardness. [6]

In a review by František Kožíšek, M. D. , Ph. D. National Institute of Public Health, Czech Republic there is a good overview of the topic, and unlike the WHO, sets some recommendations for the maximum and minimum levels of calcium (40-80 mg/L) and magnesium (20-30 mg/L) in drinking water, and a total hardness expressed as the sum of the calcium and magnesium concentrations of 2-4 mmol/L. [7]

Other studies have shown weak correlations between cardiovascular health and water hardness. [8][9][10]

Very soft water can corrode the metal pipes in which it is carried and as a result the water may contain elevated levels of cadmium, copper, lead and zinc [6]. Corrosion means the breaking down of essential properties in a material due to Chemical reactions with its surroundings Pipes may refer to Pipe (cylindrical conveyance PIPES (buffering agent in biochemistry Daniel Pipes Cadmium (ˈkædmiəm is a Chemical element with the symbol Cd and Atomic number 48 Copper (ˈkɒpɚ is a Chemical element with the symbol Cu (cuprum and Atomic number 29 Characteristics Lead has a dull luster and is a dense, Ductile, very soft highly Zinc (ˈzɪŋk from Zink is a Metallic Chemical element with the symbol Zn and Atomic number 30

Softening

It is often desirable to soften hard water, as it does not readily form lather with soap. The most general definition of foam is a substance that is formed by trapping many gas Bubbles in a Liquid or Solid. Soap is wasted when trying to form lather, and in the process, scum forms. Hard water may be treated to reduce the effects of scaling and to make it more suitable for laundry and bathing.

Process

A water softener, like a fabric softener, works on the principle of cation or ion exchange in which ions of the hardness minerals are exchanged for sodium or potassium ions, effectively reducing the concentration of hardness minerals to tolerable levels and thus making the water softer and gives it a smoother feeling. A water softener reduces the dissolved Calcium, Magnesium, and to some degree Manganese and Ferrous iron ion concentration in Hard water An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge Ion exchange is an exchange of Ions between two Electrolytes or between an electrolyte Solution and a complex. Sodium (ˈsoʊdiəm is an element which has the symbol Na( Latin natrium, from Arabic natrun) atomic number 11 atomic mass 22 Potassium (pəˈtæsiəm is a Chemical element. It has the symbol K (kalium from qalīy Atomic number 19 and Atomic mass 39 In Chemistry, concentration is the measure of how much of a given substance there is mixed with another substance [11]

The most economical way to soften household water is with an ion exchange water softener. This unit uses sodium chloride (table salt) to recharge beads made of the ion exchange resins that exchange hardness mineral ions for sodium ions. For sodium chloride in the diet see Salt. Sodium chloride, also known as common salt, table salt, or Halite, is a ion-exchange resin is an insoluble matrix (or support structure normally in the form of small (1-2 mm diameter beads usually white or yellowish fabricated from an organic Polymer Artificial or natural zeolites can also be used. Zeolites (Greek zein, "to boil" lithos, "a stone" are hydrated Aluminosilicate Minerals and have a micro-porous structure As the hard water passes through and around the beads, the hardness mineral ions are preferentially absorbed, displacing the sodium ions. This process is called ion exchange. Ion exchange is an exchange of Ions between two Electrolytes or between an electrolyte Solution and a complex. When the bead or sodium zeolite has a low concentration of sodium ions left, it is exhausted, and can no longer soften water. The resin is recharged by flushing (often back-flushing) with saltwater. The high excess concentration of sodium ions alter the equilibrium between the ions in solution and the ions held on the surface of the resin, resulting in replacement of the hardness mineral ions on the resin or zeolite with sodium ions. The resulting saltwater and mineral ion solution is then rinsed away, and the resin is ready to start the process all over again. This cycle can be repeated many times.

The discharge of brine water during this regeneration process has been banned in some jurisdictions (notably California, USA) due to concerns about the environmental impact of the discharged sodium.

Some softening processes in industry use the same method, but on a much larger scale. These methods create an enormous amount of salty water that is costly to treat and dispose of.

Temporary hardness, caused by hydrogen carbonate (or bicarbonate) ions, can be removed by boiling. In Inorganic chemistry, bicarbonate ( IUPAC -recommended nomenclature hydrogencarbonate) is an intermediate form in the Deprotonation For example, calcium hydrogen carbonate, often present in temporary hard water, is boiled in a kettle to remove the hardness. In the process, a scale forms on the inside of the kettle in a process known as "furring of kettles". This scale is composed of calcium carbonate. Calcium carbonate is a Chemical compound with the Chemical formula Ca[[Carbon C]] O 3

Ca(HCO3)2 → CaCO3 + CO2 + H2O

Hardness can also be reduced with a lime-soda ash treatment. This process, developed by Thomas Clark in 1841, involves the addition of slaked lime (calcium hydroxide — Ca(OH)2) to a hard water supply to convert the hydrogen carbonate hardness to carbonate, which precipitates and can be removed by filtration:

Ca(HCO3)2 + Ca(OH)2 → 2CaCO3 + 2H2O

The addition of sodium carbonate also softens permanently hard water containing calcium sulfate, as the calcium ions form calcium carbonate which precipitates out and sodium sulfate is formed which is soluble. Thomas Clark (1801 - 1867 was a British chemist Clark was born in Ayr; he became well known for the discovery of the phosphate of soda and the process of softening For the game see 1841 (board game. Year 1841 ( MDCCCXLI) was a Common year starting on Friday (link Calcium hydroxide, traditionally called slaked lime, hydrated lime, or pickling lime, is a Chemical compound with the chemical formula Calcium sulfate is a common laboratory and industrial chemical Sodium sulfate is the Sodium salt of Sulfuric acid The calcium carbonate that is formed sinks to the bottom. Sodium sulfate has no effect on the hardness of water.

Na2CO3 + CaSO4 → Na2SO4 + CaCO3

Effects on Skin

Some confusion may arise after a first experience with soft water. Hard water does not lather well with soap and leaves a "less than clean" feeling. Soft water lathers better than hard water but leaves a "slippery feeling" on the skin after use with soap. For example, a certain water softener manufacturer contests that the "slippery feeling" after showering in soft water is due to "cleaner skin" and the absence of "friction-causing" soap scum.

However, the chemical explanation is that softened water, due to its sodium content, has a much reduced ability to combine with the soap film on your body and therefore, it is much more difficult to rinse off. [12] Solutions are to use less soap or a synthetic liquid body wash.

Regional Information

Hard water in Australia

Analysis of water hardness in major Australian cities by the Australian Water Association shows a range from very soft (Melbourne) to very hard (Adelaide). Total Hardness levels of Calcium Carbonate in mg/L are: Canberra: 40[13]; Melbourne: 10 - 26[14]; Sydney: 39. Canberra ( is the capital city of Australia With a population of over 340000 it is Australia's largest inland City. Melbourne ( is the second most populous city in Australia, with a Metropolitan area population of approximately 3 Sydney (ˈsɪdniː is the most populous city in Australia, with a Metropolitan area population of approximately 4 4 - 60. 1[15]; Perth: 29 - 226[16]; Brisbane: 100[17]; Adelaide: 134 - 148[18]; Hobart: 5. Perth is the capital and largest city of the Australian state of Western Australia. Brisbane ( is the state capital of Queensland. Brisbane is the third most populous city in Australia and the most populous city of Queensland Adelaide is the capital and most populous city of the Australian state of South Australia, and is the fifth largest city in Australia with a Hobart is the state capital and most populous city of the Australian island state of Tasmania. 8 - 34. 4[19]; Darwin: 31[20].

Hard water in Canada

Prairie provinces (mainly Saskatchewan and Manitoba) contain high quantities of calcium and magnesium, often as dolomite, which are readily soluble in the groundwater that contains high concentrations of trapped carbon dioxide from the last glaciation. Prairie, from the French prairie ("meadow" "grassland" "pasture" refers to an area of land of low topographic relief that historically Saskatchewan (səˈskætʃəwən) is a prairie province in Canada, which has an area of 588276 Manitoba (English ˌmænɨˈtoʊbə French /manitoba/ is a province of Canada, spanning 647797 square kilometres (250116  sq mi of North America Dolomite (ˈdɒləmaɪt is the name of a Sedimentary Carbonate rock and a Mineral, both composed Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single "Glacial" and "Glaciation" redirect here For the geological periods see Glacial period. In these parts of Canada, the total hardness in mg/L of calcium carbonate equivalent frequently exceed 200 mg/L, if groundwater is the only source of potable water. The west coast, by contrast, has unusually soft water, derived mainly from mountain lakes fed by glaciers and snowmelt.

Some typical values are: Calgary 165 mg/L, Saskatoon < 140 mg/L, Winnipeg 77 mg/L,[21] Toronto 121 mg/L,[22] Vancouver < 3 mg/L,[23] Charlottetown PEI 140 - 150 mg/L. Calgary (ˈkælgəriː is the largest city in the Province of Alberta, Canada Saskatoon is a city located in central Saskatchewan, Canada, on the South Saskatchewan River, with a Winnipeg (ˈwɪnɨpɛg is the capital and largest city in the Canadian province of Manitoba, and 7th largest municipality in Canada with a population Toronto (təˈrɒntoʊ colloquially pronounced or) is the largest city in Canada and is the provincial capital of Ontario Vancouver (vænˈkuːvɚ is a coastal [24]

Hard water in England and Wales

Information from the British Drinking Water Inspectorate shows that drinking water in England is generally considered to be 'very hard', with most areas of England, particularly the East, exhibiting above 200 mg/L for the calcium carbonate equivalent. England is a Country which is part of the United Kingdom. Its inhabitants account for more than 83% of the total UK population whilst its mainland Wales, Devon, Cornwall and parts of North-West England are softer water areas, and range from 0 to 200 mg/L. Devon is a large county in the South West of England. The county is also referred to as Devonshire, but that is an entirely unofficial name Cornwall ( Kernow ˈkɛɹnɔʊ is the most southwesterly county of England, on the Peninsula that lies to the west of the River Tamar In the brewing industry in England and Wales, water is often deliberately hardened with gypsum in the process of Burtonisation. Brewing is the production of Alcoholic beverage and Alcohol fuel through fermentation. Gypsum is a very soft Mineral composed of Calcium sulfate dihydrate with the Chemical formula Ca[[sulfur S]] O 4·2 Burtonisation is the act of adding sulfate, often in the form of Gypsum, to the water used for the Brewing of Beer, in order to bring out the

Hard water in the US

According to the United States Geological Survey, 89. The United States Geological Survey ( USGS) is a scientific agency of the United States government. 3% of US homes have hard water. The softest waters occur in parts of the New England, South Atlantic-Gulf, Pacific Northwest, and Hawaii regions. History See also History of New England New England's earliest inhabitants were Algonquian -speaking Native Americans including the The Pacific Northwest is a region in the northwest of North America (the term refers to the land not the ocean The State of Hawaii ( or həˈwaɪʔiː Hawaiian: Mokuāina o Hawaii) is a state in the United States located on an Archipelago in the Moderately hard waters are common in many of the rivers of the Tennessee, Great Lakes, Pacific Northwest, and Alaska regions. Tennessee ( is a state located in the Southern United States. The Laurentian Great Lakes are a chain of freshwater lakes located in eastern North America, on the Canada–United States border. The Pacific Northwest is a region in the northwest of North America (the term refers to the land not the ocean Alaska ( Аляска Alyaska) is a state in the United States of America, in the northwest of the North American continent Hard and very hard waters are found in some of the streams in most of the regions throughout the country. Hardest waters (greater than 1,000 mg/L) are in streams in Texas, New Mexico, Kansas, Arizona, and southern California. Texas ( is a state geographically located in the South Central United States and is also known as the Lone Star State. [25]

See also

References

  1. ^ Body And Fitness Healthy Hair Tips
  2. ^ Corrosion by water
  3. ^ T. A water softener reduces the dissolved Calcium, Magnesium, and to some degree Manganese and Ferrous iron ion concentration in Hard water Water quality is the physical chemical and biological characteristics of Water in relationship to a set of standards Water treatment describes those processes used to make water more acceptable for a desired end-use Water purification is the process of removing contaminants and other harmful microorganisms from a raw water source The Well of Zamzam (or the Zamzam Well, or just Zamzam; Arabic: زمزم) is a well located within the Masjid al Haram in E. , Larson and R. V. Skold, Laboratory Studies Relating Mineral Quality of Water to Corrosion of Steel and Cast Iron, 1958 Illinois State Water Survey, Champaign, IL pp. [43] - 46: ill. ISWS C-71
  4. ^ Stiff, Jr. , H. A. , Davis, L. E. , A Method For Predicting The Tendency of Oil Field Water to Deposit Calcium Carbonate, Pet. Trans. AIME 195;213 (1952).
  5. ^ Oddo,J. E. , Tomson, M. B. ,Scale Control, Prediction and Treatment Or How Companies Evaluate A Scaling Problem and What They Do Wrong, CORROSION/92, Paper No. 34, (Houston, TX:NACE INTERNATIONAL 1992).
  6. ^ a b c World Health Organization Hardness in Drinking-Water, 2003
  7. ^ František Kožíšek Health significance of drinking water calcium and magnesium, February 2003
  8. ^ Studies of water quality and cardiovascular diseas...[Sci Total Environ. 1981] - PubMed Result
  9. ^ Cardiovascular mortality and calcium and magnesium...[Eur J Epidemiol. 2003] - PubMed Result
  10. ^ Magnesium and calcium in drinking water and death ...[Epidemiology. 1999] - PubMed Result
  11. ^ How does a water softener work? at Howstuffworks. com
  12. ^ With soft water, why can't we rinse off all the soap?
  13. ^ ACTewAGL: Dishwashers and Water Hardness
  14. ^ Melbourne Water Public Health Compliance Report - July-September 2006
  15. ^ Sydney Typical Drinking Water Analysis
  16. ^ Perth Drinking Water Quality Annual report 2005-06
  17. ^ Brisbane Drinking Water
  18. ^ Adelaide Water Quality
  19. ^ Hobart Drinking Water Quality
  20. ^ Darwin Water Quality
  21. ^ 2006 Winnipeg drinking water quality test results
  22. ^ City of Toronto: Toronto Water - FAQ
  23. ^ GVRD Wash Smart - Water Facts
  24. ^ http://www.city.charlottetown.pe.ca/allaire/spectra/system/mediastore/Water_Report_2006.pdf
  25. ^ Briggs, J. C. , and Ficke, J. F. ; Quality of Rivers of the United States, 1975 Water Year -- Based on the National Stream Quality Accounting Network (NASQAN): U. S. Geological Survey Open-File Report 78-200, 436 p. (1977)

External links

Dictionary

hard water

-noun

  1. (chemistry) water with a high concentration of dissolved minerals, especially calcium, making it difficult to lather with soap
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