Types of stiffness. Methods of water softening. Water hardness what is it

(eng. Hardness of water, hardness of water, stiffness of water; him Härte f, Härte f des Wassers, Wasserhärte f) - a set of properties due to the content of calcium and magnesium cations in water.

general description

Determined by the number of salts of calcium and magnesium in it. If water contains significant amounts of such salts, then such water is called tough and when these salts are completely absent, or they are contained in insignificant quantities, — soft.

There are temporary, or carbonate, water hardness and constant. Temporary rigidity is due to the presence of acid carbonates (hydrocarbonates) of calcium and magnesium: Ca (HCO 3) 2 and Mg (HCO 3) 2, and became the presence of sulfates and chlorides of calcium and magnesium: CaSO 4, MgSO 4, CaCl 2 and MgCl 2. The total water hardness is the sum of the temporary and permanent hardness.

Hard water is unsuitable for almost all industries. For example, hard water can not be used for washing clothes, washing wool and dyeing fabrics, because soap loses its washing ability in it. This is explained by the fact that water-soluble sodium stearate C 17 H 35 COONa, which constitutes the main component of the soap, goes into insoluble calcium stearate (or magnesium), forming the so-called calcium (or magnesium) soap:

2C 17 H 35 COONa + CaSO 4 = Ca (C 17 H 35 COO) 2 ↓ + Na 2 SO 4

At the same time, soap foam is formed only after the complete precipitation of calcium and magnesium ions, for which much soap is unproductively consumed. In addition, the precipitate of calcium and magnesium soaps is firmly deposited on the fibers of the tissues and zabrudyue them, and when stained to form stains.

Hard water is unsuitable for a number of other industries: paper, leather, starch, alcohol, and the like. It is also unsuitable for steam power, as when boiling water forms scum, which conducts heat poorly, as a result of which fuel consumption increases. Scale causes intense destruction of the walls of the boilers, which can lead to an accident.

Hard water is also not used for cooking, because meat and vegetables are badly boiled soft in it. It is also unsuitable for drinking.

Methods for determining water hardness

Water hardness is most often determined by titration with a solution of disodium salt of ethylene diamine tetraacetate acid (complexones III, Trilon B) in an alkaline medium in the presence of an indicator, special black chromogen or black eriochrome. Using another special indicator - murexide, determine the calcium TV; Magnesium TV calculated by the difference between the results of the two definitions. If the content of calcium and magnesium in water was determined by other methods, the total TV can be calculated by the formula: T = Ca 2+ + Mg 2+, where T is the total TV, mmol / dm3; Ca 2+ and Mg 2+ - the concentration of calcium and magnesium, mmol / dm3.

Water hardness classification

Water with T. less than 4 mmol / dm3 is characterized as soft, from 4 to 8 mmol / dm3 - medium hardness, from 8 to 12 mmol / dm 3 - solid, more than 12 mmol / dm3 - very hard.

According to A. A. Alekinim:

very soft - up to 1.5 mmol / dm;
soft - 1.5-3.0 mmol / dm;
moderately hard - 3.0-6.0 mmol / dm3;
solid - 6.0-9.0 mmol / dm3;
very hard - more than 9.0 mmol / dm3.

Units

Different countries use different off-system units - degrees of hardness.

Ways to eliminate water hardness

To eliminate the hardness of water, that is, its softening, it is necessary to remove the Ca 2+ and Mg 2+ ions in the form of insoluble salts from the water.

Temporary water hardness eliminate by boiling:
- Ca (HCO 3) 2 = CaCO3 ↓ + H 2 O + CO 2
- Mg (HCO 3) 2 = MgCO 3 ↓ + H 2 O + CO 2

When heated, the Ca 2+ and Mg 2+ ions are removed from the solution as insoluble carbonates. It is the ease of removing the temporary hardness of water when heated leads the name - "temporary".

Constant water hardness caused by sulphates and chlorides of calcium and magnesium cannot be eliminated by boiling, since these salts do not decompose. The name “constant stiffness” comes precisely from the fact that it cannot be eliminated by simply heating water. It is eliminated by introducing some reagents into the water — sodium carbonate (soda ash), calcium hydroxide (lime water), orthophosphate sodium. At the same time, both temporary and permanent, that is, the total water hardness is eliminated. For example:
- Ca (HCO 3) 2 + Ca (OH) 2 = 2CaCO 3 ↓ + 2H 2 O
- MgSO 4 + Na 2 CO 3 = MgCO 3 ↓ + Na 2 SO 4
- Ca (HCO 3) 2 + Na 2 CO 3 = CaCO3 ↓ + 2NaHCO 3
- 3CaSO 4 + 2Na 3 PO 4 = Ca 3 (PO 4) 2 ↓ + 3Na 2 SO 4

Modern way of water softening based on the use of ion exchange resins - cation exchangers. Cation exchangers are solids that are insoluble in water and contain mobile Na + cations in the form of salts of organic acids fixed on the surface of the carrier. Simplistically, they are designated as follows: Na 2 R. Na + cations can be exchanged for environmental cations, such as Ca 2+ and Mg 2+. When hard water is passed through a column with cation exchanger, the Ca 2+ and Mg 2+ ions are retained in it, and the Na + cations from the cation exchanger pass into the water:
- Na 2 R + Ca 2+ = CaR + 2Na +

The cation exchanger is periodically regenerated by washing it with a concentrated solution of sodium chloride.

Natural water hardness

The hardness of natural water varies widely; it varies in different natural waters, in the same water body its value varies in seasons. In surface waters, T. reaches the highest values at the end of winter, small ones - during the flood period. In the surface waters, carbonate T is usually predominant (70–80% of the total). Magneva T.V. rarely exceeds 30% of the total, but in some areas (Donbass, Krivoy Rog) it reaches 60% of the total. T. groundwater, especially in artesian wells, changes less during the year.
The hardness of the river waters of Ukraine, as well as the mineralization of water, increases from northwest to southeast. In the Polesia river waters, the hardness is 2-3 mmol / dm³, in the Dnieper - 4-5 mmol / dm³, and in the small and medium rivers of the Azov region - 15-30 mmol / dm³, which limits the possibilities of using local water resources.
Sea water hardness: Black Sea - calcium 12.0 mmol / dm 3, magnesium 53.5 mmol / dm 3, total 65.5 mmol / dm 3; The Caspian Sea - calcium, 36.4 mmol / dm 3, magnesium, 30 mmol / dm 3, total 66.4 mmol / dm3; ocean - calcium 22.5 mmol / dm 3, magnesium 108 mmol / dm 3, total 130.5 mmol / dm 3.

Drinking water hardness

In Ukraine, according to the State Sanitary Regulations and Rules “Hygienic requirements for drinking water intended for human consumption” (GOSanPiN 2.2.4-171-10), approved by the Ministry of Health of Ukraine 12.05. 2010, which generally regulate the quality of drinking water - the following standards have been adopted for hardness (hardness) indicators of drinking water:

tap water - up to 6.5 mmol / dm³ (in some cases with the permission of sanitary services - up to 10 mmol / dm³)
water wells and capturing sources - up to 10 mmol / dm;
water packaged from spill points and from drinking pump rooms - 7 mmol / dm³.

The effect of stiffness on human health

Drinking water according to the degree of hardness can vary significantly depending on local conditions, which can be learned at the waterworks. The taste threshold for calcium ions is (in terms of mEq) in the range of 2-6 mEq / L, depending on the corresponding anion, and the taste threshold for magnesium is even lower. In some cases, water with hardness above 10 mEq / L is acceptable for consumers. High zheskost degrades the organoleptic properties of water, giving it a bitter taste and exerting a negative effect on the digestive organs.

The World Health Organization does not offer any recommended amount of hardness for health effects. The WHO materials state that although a number of studies have revealed a statistically inverse relationship between drinking water hardness and cardiovascular diseases, the available data are insufficient for conclusions about the causal nature of this relationship. However, it is not proven that soft water has a negative effect on the balance of minerals in the human body.

However, using soft water consumes 2 times less detergent. Calcium ions, interacting with soap, form salts, which are not washed off with water and leave stains on the dishes and plumbing surfaces. These salts also do not wash off the surface of human skin, clogging the pores and covering every hair on the body.
When water is heated, the hardness salts it contains crystallize to form in a form of scale. Scale causes 90% of water heater failures. Therefore, the water subjected to heating in boilers, boilers, are more stringent requirements for rigidity.

How to reduce stiffness?

There are special softening filters for water softening. The most common options are with ion-exchange materials, which "pull" from the water ions of calcium and magnesium. A more effective way to remove hardness salts from the reverse osmotic membranes. Another simple and affordable way is to boil water. At the same time, the lime contained in it will settle on the walls of the dish in the form of lime scale. This is a very effective method, but when it comes to large amounts of water, it requires a lot of effort and energy. To soften small amounts of water in the domestic environment, you can use regular soda.

Hardness - the most important property of fresh aquarium water. By tradition, it is measured in degrees, but in different countries its particular degrees of rigidity. To translate one degree into another and understand what all the same they mean will help this novice aquarist.

"Degrees are different ..."
Popular wisdom

Hardness is one of the most important properties of aquarium water. Want to do aquarism seriously? Then you just need to figure out what it is and how it is measured!
Water hardness is a combination of its properties due to the presence in it calcium cations (Ca 2+), magnesium (Mg 2+), and partly ferrous iron (Fe 2+). Distinguish between permanent, temporary and total hardness.
Total hardness determined by the total water content of all of the above cations. These ions are in water as a result of the dissolution of the corresponding salts in it. How this happens and, moreover, the methods of expressing ion concentrations adopted in science are described in a separate article. The content of dissolved salts in fresh water (not only calcium and magnesium, but also others) is described in the article "".
Constant stiffness not polluted by industrial effluents of low-mineralized surface natural waters characterizes the amount of dissolved sulfates, chlorides and some other salts of calcium and magnesium. That is, in these waters, along with the Ca 2+ and Mg 2+ cations, there are anions SO 4 2-, Cl -, etc. When such water is boiled, the concentrations of these cations and anions remain virtually unchanged - hence the name “constant hardness”.
Temporary stiffness associated with the presence in water along with the cations Ca 2+, Mg 2+ and Fe 2+ hydrocarbonate, or bicarbonate anions (HCO 3 -). When boiling water bicarbonates decompose, forming a very poorly soluble calcium carbonate, carbon dioxide and water:

Ca 2+ + 2HCO 3 - = CaCO 3 ↓ + H 2 O + CO 2

Thus, temporary stiffness can be eliminated by long-term boiling, so it is also “temporary.”

With iron ions, the reaction is more complicated due to the fact that FeCO 3 is an unstable substance in water. In the presence of oxygen, the final product of the reaction chain is Fe (OH) 3, which is a dark-red precipitate. Therefore, the more iron in the water, the stronger the color of scale, which is deposited on the walls and bottom of the vessel during boiling.
Separate tests are sold in stores to measure total and temporary stiffness. In addition, our website describes the methods for determining the temporal and total stiffness using readily available reagents, so it is quite possible to determine the stiffness in the home, even without having branded tests. How to do this, read the article " Methods for determining overall stiffness "and" Determination of temporal or carbonate hardness ".
Why use a separate concept of "WATER HARDNESS", because the concept of "MINERALIZATION" covers the presence of all salts in the water and the above mentioned ones too? The difference between these two concepts is still there, and significant. For example, the mineralization can be raised by dissolving in water any salt (another thing is whether your fish will like this salt or not, more about this in the article "Composition and properties of aquarium water"). Aquarists with this purpose most often use sodium chloride - NaCl). But stiffness is primarily related precisely with dissolved calcium and magnesium salts. Contrary to prejudice among aquarists, dilution of salt in water (especially well cleaned) stiffness does not raise! So, HARDNESS AND MINERALIZATION of water are interrelated but DIFFERENT concepts !!!
Rigidity is the special properties of water, which largely determine its consumer qualities and therefore are of great economic importance. Hard water forms scale on the walls of heating boilers, batteries, etc., which significantly impairs their thermal performance. Hard water is not very suitable for washing. Not only does the scale on the heaters of washing machines put them out of operation ... however, I won't retell television advertising - I already got everyone out, it also worsens the washing properties of soap. Ca 2+ and Mg 2+ cations react with the fatty acids of the soap, forming poorly soluble salts, which create films and sediments, ultimately reducing the quality of washing and increasing the consumption of detergent. Simply put, hard water does not boil well. It is only now, thanks to the tremendous success of mankind in the field of chemistry, good shampoos have been created that can be washed in any water. And in old clay times in places with hard water, beauties who want to have soft and silky hair, in order to wash their hair, were forced to collect rainwater - it is soft. Not for nothing, Peter I, who demanded that people come to the assembly in a decent form, and who could not tolerate dirty beards, was forced to build a new capital on the Neva River. Here, the water is very soft, well washed and you can wash and shave your heart! In general, the rigidity of the concept rather technical and hygienic. People in different countries for a long time came to the need to ration it, because high rigidity is bad: the pipes are clogged and it is impossible to wash them properly. But they began to do this in each country in their own way, who how, based on traditional units of measurement and methods for determining calcium and magnesium ions, because there were no uniform standardized international units at that time.
It is known that there is nothing worse than bad habits - it is very difficult to get rid of them! In the aquarium literature (although the rigidity is inherently a concept not from the field of aquarium husbandry!) In different countries, rigidity is still measured in degrees, and in each country in its own, different from all others. Identical only Russian and German degrees of rigidity, however, a long time ago canceled in both these countries, but stubbornly existing in aquarium books.
In Russia, since 1952, the hardness of water for technical and hygienic needs is expressed in mEq / l (before that - in German degrees), in other countries it is common to designate hardness in CONDITIONAL degrees:

AMERICAN DEGREES (usH):

1 ° = 1 grain (0.0648 g) CaCO 3 in 1 gallon (American! 3.785 l) of water. Dividing grams per liters we get: 17.12 mg / l of caso 3. However, there is another definition of American degree: 1 part CaCO 3 per 1,000,000 parts water (in the English-language literature, the expression of the concentration as 1 part per 1,000,000 parts is called ppm - part per million (one part per million), and is often used. In practice, it is identical to 1 mg / l) . In this way this 1 American degree = 1 mg CaCO 3 in 1 liter of water. It is this value of the American degree adopted in all tables. with transient coefficients for converting one stiffness measurement unit to another; (a strange case, for people knowledgeable in shtatovskoy life, such as, for example, the author of the famous aquarium site Miklukh (whom I specifically asked about it, but he kindly answered me, for which MANY THANKS) state that the first American degree mentioned is used in the USA ).

Feel like everything is not easy ?! Therefore, I will give a table that allows you to compare and translate some degrees of rigidity to others:

Table 1
Name of units	Mg eq / l	Degree of rigidity
Name of units	Mg eq / l	deutsch	french	american	english
1 mEq / l	1	2.804	5.005	50.045	3.511
1 German degree dH	0.3566	1	1.785	17.847	1.253
1 french degree	0.1998	0.560	1	10,000	0.702
1 American degree	0.0200	0.056	0.100	1	0.070
1 English degree	0.2848	0.799	1.426	14.253	1

How to use this table?
Suppose that from the laboratory you obtained the results of the analysis of aquarium water: "Total hardness" = 3.25 mEq / l. You need to convert this value to German degrees. In the cell corresponding to the intersection of the string mcq / l and the column of German degrees, we find the coefficient, which is also a factor equal to 2.804. Now it is necessary to multiply 3.25 by 2.804. The product of these numbers will be the rigidity in German degrees (dHG). The hardness of your water in dGH = 9.110. That is, compared with mEq / l, German degrees are smaller units. If you are a happy owner of the American test, and he gave the result, for example, 14 American degrees (usH), and you need all the same German ones, then the answer in dGH will be: 14 × 0.056 = 0.780. But this is only if we believe that the American degree is 1 mg CaCO 3 in 1 liter of water (as they say in all Russian-language literature), the Americans themselves believe that their degree of hardness is 17.12 times greater (see above), respectively, and the measurement result in dGH will be equal to 13.35. I.e these American degrees are pretty close to German.

Using different units of measurement of stiffness without recalculating them (after all, they are degrees, you can not "sharpen" on what they are) can lead to a significant distortion of the data. So 14 American degrees is just 0.78 German. Therefore, reading the message of the American fish farmer, that his fish spawned at 14 ° hail. hardness, do not think that hard water is suitable for spawning, this water is actually very soft. It's funny that if other American degrees were meant, then the error will be small, so in fact, you can not sharpen ... In general, the first thing to do is to find out in what units the results are presented.
As an example of another kind of confusion associated with the recalculation of the calcium content in CaO and CaCO 3 molecules, I will cite a fragment from a book that is very popular today:

Water hardness units expressed in ppm of dissolved calcium salts *
1 English degree (Clark) 1 German degree (dH) ** 1 American degree 1 French degree (fh)	= 14.3 ppm = 17.9 ppm = 17.1 ppm = 10.0 ppm
1 ppm = 1 milligram per liter

What is wrong here? With Clark, everything is in order - the value of 14.3 ppm is essentially the same that we cited earlier on this page, only rounded. But 1 German degree is somehow strange: we know that it is equal to 10 mg of CaO in 1 liter. The authors of the book also claim that German degrees show CaO content, but where did they get the figure of 17.9 ppm from then? This is not to say that this figure was taken from the “ceiling,” that is, random, no: after working out a little arithmetic, I found that it corresponds to the amount of CaCO 3 that contains as much Ca as 10 mg of CaO! That is, it expresses the amount of CaCO 3 equivalent in calcium. And how much is Ca in CaO? Let us calculate: the CaO molecule has a mass, expressed in amu. equal to 40.08 + 16 = 56.08 (the sum of atomic masses of calcium and oxygen). What is the contribution of calcium to this mass, we know, so you can make this proportion:

Here Y is the mass of CaCO 3 (in mg), in which calcium contains 7.15 mg. Y = 17.85 (rounded, the same 17.9). That is, contrary to the note made by them, the authors of the book presented 1 German degree (10 mg / l CaO) in terms of the equivalent (equivalent) calcium for CaCO 3. Did they eventually make a mistake? Of course! After all, they indicated that these 17.9 mg / l belong to CaO. How much calcium would there be in this case?

40.08	-	56.08
X	-	17.9

X = 12.8 mg. This amount of calcium to the German degree of hardness has nothing to do!
As can be seen from the above example, the main drawback of degrees, as units of measurement of hardness, is that they show the content of calcium and magnesium not DIRECTLY, but in TRANSFER to oxide or to carbonate salt. As mentioned earlier - these are CONDITIONAL units. In fact, calcium oxide (CaO) cannot exist in water. A caso 3 - little soluble substance in water: under standard conditions at a pressure of 1 atm. and a temperature of 25 ° C dissolves only 6.7 mg / l, which can raise its hardness only to 0.24 mg-eq / l, or dGH = 0.670. It turns out that if an aquarist, eager to find out how much calcium and magnesium ions are present in the water of his aquarium, will make a test (all purchased tests measure the rigidity in degrees), then he doesn’t know it at all, but how many there would be CaO or Caso 3 if the mass really present in water, calcium and magnesium ions (Ca 2+ and Mg 2+) should be counted on an equivalent amount of these substances, which is actually not in the water!
Let me give you another plate that shows how much mg / l of calcium and magnesium ions (those that are actually in water, but not in the form of conditional substances, but in the form of actually dissolved ions) correspond to different units (degrees) of the measurement of rigidity.

table 2
Unit of measure for stiffness	The content of a substance reflect	The numerical value of 1 unit		Equivalent mass of ions that actually exist in water
Unit of measure for stiffness	The content of a substance reflect	For calcium	For magnesium	Ca 2+	Mg 2+
Mg eq / l	Ca 2+ and Mg 2+	1 mEq / l	1 mEq / l	20.04	12.15
German degree dGH	CaO and MgO	10 mg / l CaO	7.19 mg / l MgO	7.15 mg / l	4.34 mg / l
French degree fh	CaCO 3	10 mg / l CaCO 3	8.425 mg / l MgCO 3	4.005	2.429
American degree usH	CaCO 3	1 mg / l CaCO 3	0.8425 mg / l MgCO 3	0.4005	0.2429
English degree (Clark)	CaCO 3	14.254 mg / l CaCO 3	12.008 mg / l MgCO 3	5.708	3.463

In the literature available to me regarding French, American and English degrees, I did not find any mention of MgCO 3 equivalent amounts for these degrees. On the other hand, without magnesium something as?! Therefore, I, by analogy with German degrees, made recalculations from the mass of CaCO 3 to equivalent amounts of MgCO 3 and resulted in the table everything corresponding magnesium hardness values.

In general, very inconvenient units of measurement are these degrees. From that with them and the eternal confusion. Especially "encouraging" is the second note from the above fragment of the book (marked with **), it follows that it is not always clear what degrees the dH symbol means, which means confusion will grow. And it grows. Authors of books on aquarism from different countries link to each other using translations. And some translators and editors do not delve into the essence of the issue. And yet there are still simple typographical errors, which migrate from edition to edition. So sometimes it is not clear what exactly the degrees are in question, and whether these are the degrees that the author had in mind. As an example, I will cite a tablet from the well-known book of G. Mayland (p.52).

Table 3
	Him ° dH	English ° eH	Franz ° fH	Americas ° usH	CIS ° suH
1 him degree	1.00	1.25	1.78	17.8	7.15
1 eng degree	0.798	1.00	1.43	14,3	5.70
1 fr. degree	0.560	0.702	1.00	10.0	4.0
1 amerik. degree*	0.056	0.070	0.10	1.0	0.40
1 Russian Grade	0.14	0.111	0.078	0.0078	1.00
* Data in ppm (parts per million) provided that the mass of 1 liter of water is 1 kg.

I copied this tablet completely. In principle, this is the same table as table 1 above, but less accurate. In it, almost everything is correct, with the exception of data relating to certain "Russian degrees" (suH). Judging by the extreme right column of the table, they are equal to 1 mg / l Ca 2+ and then this whole column is correct. The multiplier 0.14 in the bottom line is also correct. This is easy to verify: we know (Table 2) that 1 ° dGH is equivalent to 7.15 mg of Ca 2+ per liter. If 1 ° suH is really equal to 0.14 dGH, then 1 ° suH of calcium contains 7.15 × 0.14 = 1 mg / l. Everything came together, and that means that all this is true. But then the subsequent numbers in this line do not have any reasonable explanation. The multiplication of the corresponding degrees of rigidity of the equivalent mass of calcium by the reduced coefficients of 1 mg does not. I wondered this way and that what the author wanted to show, or what he was wrong in - failed to guess (if you guess - please write). Shortly speaking, even if "Russian degrees" equal There is 1 mg / l of calcium, it is still impossible to use this table to convert them to other units!

In serious science and technology it is customary to use units of measure common to all, regardless of the "country of measurement." Just to understand each other better.
The expression of hardness in milligram equivalents per liter of water (mEq / l, sometimes milliequivalent is also written) is much more convenient than it is unclear what degrees it is not clear what.
Concluding this material, I will mention the paradoxical results that can be obtained by measuring the temporal and total rigidity. Namely: temporary rigidity may be more common. Tests can be redone anew several times, but the “weird result” will stubbornly reproduce - this is not a random test error. Mialand also mentions the possibility of obtaining such results in his book, but he does not give a sensible explanation (although it may just be an unintelligible translation of the book). Meanwhile, this casket opens very simply. About how - you can read in the article about temporary stiffness .

The editorial department of "Living Water".

1) OS Zaytsev, "Research Workshop on General Chemistry", Moscow, Moscow State University Press, 1994
2) M. Bailey, P. Bergess, "The Golden Book of the Acariumist", Moscow, "Aquarium", 2002 (page 116).
3) CaO - quicklime, or burnt lime reacts with water to form a large amount of heat: CaO + H 2 O = Ca (OH) 2 + 65 kJ. This process is called lime slaking, and the resulting product is called slaked lime. Ca (OH) 2 is slightly soluble in water. In 1 liter it dissolves at 20 ° C of about 1.56 g. A saturated solution of calcium hydroxide is called lime water and has an alkaline reaction. In the air, lime water quickly becomes turbid due to its absorption of carbon dioxide (CO 2) and the formation of insoluble calcium carbonate. Back to text

Hard water. This phrase is firmly entrenched in our consciousness. But what do we know about her? That it is very difficult to wash in it - the powder does not lather, and the fabric becomes unpleasant to the touch. We also know that water with a high level of hardness is harmful to the skin and hair. It causes dryness and flaking. We also heard that it causes scale formation on electrical appliances and failure. But where does the rigidity come from, what is its effect on human health and the most important thing - how to deal with it? Today we will help you figure it out.

What water is called hard

Hardness is a characteristic of water, which means the level of hardness salts dissolved in it. These are mainly calcium and magnesium salts.

The term "hard water" is actively used in everyday life. However, not everyone fully understands the meaning. It does not indicate the immediate properties of water. We can’t touch hardness or softness. This term arose because the fabrics that are washed in such water become less soft and pliable. The reason is the porous structure of the fabric, which is able to add salts formed during washing.

Where does the increased water hardness come from

Although we are used to associate environmental problems with human activity, it has nothing to do with the hardness of natural water from sources. The reason lies underground. And more precisely, in the deposits of rocks: gypsum, limestone, dolomite. Groundwater dissolves these rocks in itself. Cations of calcium and magnesium and other metals appear in the water, which react with anions and directly affect hardness.

Therefore, in the underground sources and in the well hard water. Fresh water in surface sources is softer than underground. However, surface waters have greater hardness in winter. But the onset of spring they receive meltwater and reduce hardness.

Types of water hardness

The total hardness expresses the total amount of salts in the water. In turn, it is divided into two types: temporary (carbonate) and permanent (non-carbonate). The apparent difference is in the formation of sediment when heated. Salts of temporary stiffness precipitate, and the constants are vice versa. Temporary hardness is special content of bicarbonate or bicarbonate compounds, which decompose when boiled and form water, carbon dioxide and calcium carbonate. Therefore, temporary rigidity is completely or partially eliminated by boiling.

The situation is different with constant rigidity. It arises due to the content in the salts of chlorides, sulfates, phosphates, nitrates and other elements. It is impossible to get rid of it by heating water. Substances do not decompose and do not form a precipitate. And in excessive quantities they harm human health. When cleaning water, it is important to pay attention to temporary and permanent stiffness.

How is water hardness measured?

On the territory of the Russian Federation, it is measured by degrees of hardness. I will give a comparative table of measurement in different countries:

In different cities of European countries, the rigidity index is significantly different. For comparison, I will give a table:

Hard water quality

The hardness index significantly affects the taste of drinking water. She gets an unpleasant bitter taste. However, there are no unambiguous requirements regarding the permissible level of rigidity. It all depends on the specific area of residence. For some consumers, there is one allowable rate, and for others it can be 2 times higher.

The World Health Organization, in a number of its materials, indicates a connection between rigidity and certain diseases. However, according to experts, these data are not enough to establish a valid indicator. According to the state standard of the Russian Federation, the hardness of drinking water should not exceed 7 mEq / l. But for heating and water heaters, the properties of hard water are of great importance. After all, the higher it is, the more likely the formation of slag and scale in pipes, boilers and kettles. Therefore, the most acceptable indicator is less than 4 mEq / l.

A significant disadvantage of hard water is weak foaming of detergents. This causes a significant overrun. And after drying on the surface of linen, plumbing, washed surfaces, and even the skin and hair of a person an invisible bloom.

At the same time, too soft water with an index of less than 2 mEq / l has a low alkalinity. This entails an increased corrosion capacity of water pipes. Therefore, it is important to maintain the right balance between hardness and softness.

I will give a table of indicators of stiffness and classification:

Effect of hard water on the human body

Hard water contains elements, the overabundance of which adversely affects health. Moreover, this influence has visible and invisible consequences. Consider them in detail.

The reaction of the skin to hard water is most noticeable and manifests itself almost immediately. Hardness salts react with substances in shampoo and other cosmetics and form a special foam that is difficult to wash off. After it dries, a film appears on the skin.

The main harm of hard water and this sediment is the destruction of the natural greasy film, which is always present on the skin of a healthy person. It is a protective mechanism of the skin and resists microbes and aggressive manifestations of the external environment. Hard water dries the skin, promotes the appearance of peeling and allergies. Because of her worries dandruff, get rid of that does not help even special shampoos. The disappearance of the protective fatty film contributes to the appearance of wrinkles and rapid aging of the skin.

Less noticeable is the effect of hard water on the digestive system. More often, we attribute these effects to food eaten. However, the properties of hard water often cause a violation of the stomach and intestines. They form compounds with animal proteins from food and accumulate in the digestive organs, settling on the walls. Salts can interfere with fermentation and contribute to the accumulation of toxins.

Hard water hurts the heart and blood vessels. An excess of calcium and magnesium leads to disruption of the heart muscle. However, the lack of these elements threatens problems with the cardiovascular system. Water purification filters help avoid these problems. They contribute to the normal balance of water hardness. Problems with the musculoskeletal system. The mobility of our body is provided by synovial fluid, which serves as a lubricant for the joints. The use of water with increased hardness contributes to the accumulation of mineral substances that significantly impede the body's motor abilities. There are pains when bending and unbending joints.

Until recently, hard water was attributed to the appearance of stones in the kidneys and biliary tract. However, research scientists dispel this misconception. In fact, the stones do not appear when there is a surplus, but when there is a shortage of calcium. If the body does not get enough of this element from food, then it begins to take calcium from the bones. Most are not digestible and form stones in the internal organs and spurs on the bones. In this case, a surplus of magnesium in water does not allow calcium to be properly absorbed and displaces it from the body. Therefore, partly hard water is the cause of the appearance of stones.

How to determine the increased water hardness at home

Externally, water with increased hardness is not at all different from normal. Often it does not have a specific smell or turbidity. And the exact content of hardness salts will show only the analysis. However, there are several signs that will accurately indicate its presence and help to avoid the harm of hard water.

Water softening methods

Water softening refers to the elimination or minimization of hardness salts in the composition. To determine the need for this process, water analysis is performed. Only by the results conclusions are drawn about the hardness index of water. For softening such methods are used:

heat treatment;
chemical treatment;
physical methods;
membrane method;
ion exchange.

Heat treatment

Simple language - boiling. This method is one of the most common for softening water at home. As we said to the wound, when heated, bicarbonate compounds (which cause hard water) decompose and form a precipitate. In this way, partial elimination of hard water is possible.

The advantages of the method include ease of implementation, low cost and the possibility of water softening at home. It does not require additional equipment and materials. The disadvantages of the method:

small amount of purified water obtained;
wait until it cools down;
scale formation on boiling dishes;
incomplete elimination of hardness salts.

Chemical processing

This method involves the extraction of hardness salts using chemical reactions. Special substances - reagents are added to the water. Their task is to neutralize calcium and magnesium ions. This is due to precipitation. Reagents are selected based on the initial composition of the water. They can be: lime, caustic soda, soda ash and baking soda, synthetic reagents. Let's consider the ways and cases in which they are applied.

Lime. It is used to soften water with high carbonate hardness and low non-carbonate. In addition to lime, coagulant reagents are added.
Lime and soda. The combination of these substances makes it possible to obtain soft water with a hardness index of up to 1.4-1.8 mEq / l.
If carbonate hardness is significantly expressed in water, then soda-sodium reagent is used.
Synthetic reagents. This is a cocktail of substances that effectively cope with the hardness in water. For example, capsules and tablets for dishwashers and washing machines.

The use of reagents for water softening can significantly reduce the rigidity and remove the suspension. However, this approach has several drawbacks:

the appearance of waste that requires further disposal;
accurate dose calculation Otherwise it turns out unsuitable and even toxic water;
after using the reagents, the water becomes suitable only for domestic purposes. Can not be used for drinking and for cooking. The only exception is baking soda. However, the disadvantage is partial water purification.
reagents require special storage conditions.

Physical methods

Combine several methods of water purification from hardness salts, which are based on physical processes:

Electrodialysis It consists in the movement of ions to the electrodes. Thus, the metals that make up the hardness salts are retained.
Magnets. Water passes through magnetic fields of different directions. During this process, large compounds are formed that precipitate.
Magnetic Ionization Method. It is similar to the previous one, but ionization is used for the best result.
Ultrasound. The principle of operation resembles a magnetic method. Also formed large particles.
Electromagnetic radiation. The method that began to be applied not so long ago. Under the influence of electromagnetic waves of a certain frequency, metal ions lose their ability to create scale and settle. This way of dealing with stiffness is good both for preventing scale and for exfoliating existing layers.

Membrane method

The main tool is a high pressure, under which water is passed through a translucent film (membrane). It detains impurities and passes only water molecules. By its properties, the resulting water is similar to distilled. This is almost an ideal method, which gives high quality liquid.

However, there are several significant drawbacks:

requires a lot of pressure;
water is purified, but for its use requires additional mineralization;
expensive equipment and materials.

Ion exchange

This method of softening is based on the exchange of hardness ions in water (calcium and magnesium) with ions of filter materials (sodium). Filtering materials are special fine-grained resins.

Constant exchange of ions leads to the disappearance of ions from the load, therefore, replacement or restoration is required. With the replacement, everything is clear. But what is recovery? This is the process when a special solution is passed through the spent resin. Most often in the filters for the purification of hard water is used ordinary salt. It gives sodium ions to the load, and hard metal ions are replaced and eliminated.

There are several types of filters that work with this method:

with temporary cartridges that require replacement;
bulb with a load that requires replacement;
filters with the ability to recover. Feature - in the presence of additional equipment with a cleansing load.

Ion exchange is a method that allows you to get well-softened water in a short time. Another feature is a long service life. However, there are several disadvantages:

non-refillable filters require replacement downloads or cartridges.
price of equipment.

Combined approach

Each method is selected on the basis of certain features: the initial hardness content, the presence of additional impurities, the water source, the facility for the equipment. In some cases, several methods are used simultaneously to achieve maximum softened water.

Instead of conclusions

Water softening is an important step in cleaning. Hard water can destroy boilers and kettles, lead to the formation of scale inside the heating pipes. It also has low palatability, is unsuitable for drinking, and can cause health problems.

The properties of hard water do not allow its full use for domestic needs. Therefore, be sure to pay attention to the softening. And the company Prof Water is ready to help you with this. We will conduct a free analysis of water hardness and determine the level. And we will help you choose equipment that is suitable for your well or well so that you and your loved ones enjoy only high-quality water.

Problems associated with increased water hardness:

On the heating elements of household appliances (washing machines, dishwashers, electric kettles, etc.) a lime scale is formed;

Hard water is not applicable in a number of technological processes (for example, when making beer or when dyeing with water-soluble paints);

Hard water has a bad effect on the human skin (when washing, the skin becomes too dry, which can cause itching and irritation);

Washing the head with hard water not only does not cleanse, but also spoils the hair, as the salts in hard water leave a sticky residue on the hair, contribute to the appearance of dryness, brittle hair and peeling of the scalp;

Use for drinking hard water with a high content of calcium salts can contribute to the development of urolithiasis (urolithiasis);

In hard water, some products, such as meat and legumes, boil much longer, since calcium ions form insoluble compounds with food proteins;

Poor foaming of hard water leads to excessive consumption of detergents;

When washing with hard water, it is difficult to achieve the whitening effect, it is impossible to thoroughly rinse clothes, which leads to the loss of the original color of the fabric: white fabrics become grayish, colored ones become dull;

Hard water with a high content of calcium and magnesium spoils not only the color, but also the taste of tea;

Water hardness due to the formation of deposits has a negative effect on boiler equipment. Kotlonadzor Russia imposed strict requirements for water quality in terms of hardness. Therefore, for boilers of thermal power plants, power plants, industrial water heaters water softening (water treatment) is imperative.

Currently water softening by the following methods:

- thermal (water heating above 100 0 С or freezing of water);

- reagent (adding reagents, such as lime and soda, and binding these reagents calcium and magnesium ions to practically insoluble compounds);

- dialysis (filtration of source water through a semipermeable membrane);

- combined representing various combinations of the above methods.

In the same time, use too soft water:

It can lead to corrosion of pipes, as in this case there is no acid-base buffering, which is provided by hydrocarbonate (temporary) hardness;

The lack of magnesium and calcium salts in drinking water increases the risk of cardiovascular diseases;

Too soft water is detrimental to many aquarium fish and plants.

According to Mosvodokanal, hardness of tap water in Moscow during the year ranges from 2 to 5-5.5 degrees of hardness (or mEq / l). It is minimal during the period of melting snow, and maximum - in winter. The value of hardness is largely determined by the specific weather conditions of each year (rainfall, including snow, thaw in winter, timing and intensity of spring flood, temperature in April-May, precipitation intensity in summer and autumn, etc.). Water hardness is a characteristic of a particular water source and does not change during the preparation of drinking water in the centralized water supply system of Moscow. A part of the city (north-west, west, south-west, south and south-east) is supplied with water from the Moskvoretsky spring, which, as a rule, has a somewhat higher hardness than the water of the Volga spring, which flows north, north-east and east of Moscow .

In the Moscow Region and adjacent areas, the hardness of water in underground sources is from 5 to 30 mEq / l. In the southern regions of Russia, the hardness rate is even higher due to the release of salted sea water closer to the surface of the earth. Soft water in St. Petersburg.

Permissible water hardness limitused for centralized water supply - 7 mEq / l.

Accurate information about the hardness of water in your area is available at the Sanitary and Epidemiological Station and Vodokanal (an organization that supplies you with drinking and process water, as well as cleaning drinking and wastewater and wastewater).