RU2106316C1 - Method of softening water - Google Patents

Abstract

FIELD: drinking water treatment. SUBSTANCE: calcium hydroxide, potassium carbonate, and potassium hydroxide are consecutively added to water, potassium carbonate quantity being determined from equation 48-53h where h is constant hardness of water and quantity of potassium hydroxide not exceeding 50 mg/l. Once precipitate separated, water is treated by food acid until pH ≤ 8 is attained. Instead of potassium carbonate, soluble part of sunflower ashes can be used with 15% K₂CO₃, 3.3% KCl, and 1.7% K₂SO₄, or soluble part of slop coal and ashes with their solid part containing 81-96% K₂CO₃, 0.5-2.5% K₂SO₄, 1.0-6.4% KCl, and 0.5-10.0% Na₂CO₃. Before adding salts, water is warmed to 35-50 C and, with all salts added, treated in alternate electric field. EFFECT: improved quality of water. 5 cl, 2 tbl

Description

 The proposed method relates to softening methods for hard (superhard) water and can be used to soften water (for drinking and food purposes) from natural sources containing a large amount of hardness salts. In addition, this method is applicable for the clarification and purification of manure and wastewater of food and chemical industries.

A known method of softening hard water, in which at the first stage using a calcium compound, for example calcium hydroxide added to water in an amount determined by the dependence of 37 W _BP +1.7 CO ₂ +1.8 MgO, where W _BP - temporary hardness, mg-equivalent / l, MgO and CO ₂ - the amounts of MgO and CO ₂ found in the analysis of water in mg per 1 liter of water eliminate the stiffness caused by compounds Ca (HCO ₃ ) ₂ , Mg (HCO ₃ ) ₂ , MgCO ₃ , MgSO ₄ (and other salts of magnesium), as well as CO ₂ [1,2].

 This stage allows, basically, to eliminate temporary stiffness.

To further soften the water in the second stage of the method, alkali metal compounds, for example NaOH and (or) Na ₂ CO _{3 are used} . When Na ₂ CO _{3 is} added to water, the stiffness caused by the compounds CaCI ₂ , CaSO ₄ , MgSO ₄ (and other magnesium compounds) is eliminated [1,2].

When NaOH is used to soften water, Ca (OH) ₂ and Na ₂ CO ₃ are formed in water, the effect of which on water softening is described above.

 The disadvantage of using alkali metal compounds of sodium for water softening is a relatively slow decrease in the hardness of softened water.

 In addition, a side negative effect of using sodium alkali metal compounds is that with high constant hardness of the source water in softened water, large quantities of sodium sulfates and chlorides are formed, and the content of sodium carbonate and bicarbonate is not excluded. The use of such soft water for drinking and food purposes is harmful, because such water causes cardiovascular disease. The British were convinced of this, for example, when statistics showed that in Glasgow, where soft water contains a lot of sodium (its content reaches 200 mg / l), mortality from cardiovascular disease is 50% higher than in London, where the sodium content does not exceed 10 ml / l [3, p. 48].

 Similar statistical studies conducted in other countries gave the same results [3, p. 49].

 For drinking water, a sodium concentration of not more than 10 mg / l is recommended [4], and as a maximum concentration limit of 50 mg / l [5]. True, in recent years, in connection with the worsening situation with the quality of drinking water, MPC has been doubled, but this change does not benefit human health.

 Closest to the proposal is the method [1, 2].

 The disadvantages of this method are the relatively slow decrease in water hardness and the low quality of the resulting water.

 The aim of the invention is to intensify the method and improve the quality of drinking water obtained by softening superhard natural water.

The goal is achieved in that according to the method of water softening by introducing calcium compounds, for example calcium hydroxide, into the mixture with stirring in an amount determined by the dependence of 37 W _BP +1.7 CO ₂ + 1.8 MgO, where W _BP is the temporary hardness, MgO and CO ₂ — the amounts of MgO and CO ₂ found in the analysis of water in mg per 1 liter of water, the subsequent introduction of an alkali metal compound into the softened water with stirring, sediment sedimentation, separation of clarified water from the precipitate, in contrast to the prototype as an alkali metal compound use a mixture of K ₂ CO ₃ and KOH, moreover, K ₂ CO _{3 is} used in an amount determined by the dependence 48-53 Ж _p , where Ж _p is the constant hardness of the source water, and KOH is used in an amount of 0-50 mg / l, while KOH is introduced into the softened water with stirring not earlier than 30 minutes after the introduction of K ₂ CO ₃ , while after settling the precipitate and separating the settled water from the precipitate, the softened water is neutralized with food, for example phosphoric acid, to pH≤8.

In order to further intensify the method, softened water is preheated to 35-50 ^o C.

In order to expand the raw material base, a soluble part of sunflower ash (a concentrated solution of medium composition K ₂ CO ₃ -15%, KCl - 3.3%, K ₂ SO ₄ - 1.7%) or a soluble part is used as a source of K ₂ CO ₃ distillery coal and ash, the dry matter of which contains 81-96% K ₂ CO ₃ , as well as 0.5-2.5% K ₂ SO ₄ , 1 - 6.4% KCl, 0.5 - 1% Na ₂ CO ₃ .

 In order to intensify the process of coagulation of precipitated particles, alternating electric current is passed through water after all additives have been added to it.

 Justification for the selection of method parameters.

The use of K ₂ CO ₃ and KOH as the alkali metal compounds makes it possible to intensify the process of water softening. So, for example, after introducing into the water with the initial hardness of 12 mEq / l (in two samples) 0.2 g / l of Ca (OH) ₂ and holding for 2 hours, equal amounts were introduced into the water (at 0, 2 g / l) Na ₂ CO ₃ and K ₂ CO ₃ , measuring water hardness every hour. These measurements showed that in the sample with the addition of Na ₂ CO _{3 the} decrease in stiffness is slower than in the sample with the addition of K ₂ CO ₃ (see table 1).

In addition, the use of K ₂ CO ₃ and KOH as alkaline metal compounds can reduce the harmful effects of softened water on human health.

 It has been established that potassium salts cannot be replaced in the human body by any other salts, including sodium salts. The cells of the human body selectively concentrate potassium, which is contained mainly in the protoplasm of cells and blood. Rich in potassium, the liver and spleen. A significant role of this element in the regulation of enzyme activity. Potassium ions are involved in the generation and conduct of bioelectric potentials in the nerves and muscles, in the regulation of contractions of the heart and other muscles, maintain the osmotic pressure and hydration of colloids in the cells, activate some enzymes. Potassium metabolism is closely related to carbohydrate metabolism, potassium ions affect protein synthesis.

 Inhibition of glycolysis, respiration, and violation of the permeability of the outer cell membrane lead to the release of potassium from the cells, often in exchange for sodium, which further exacerbates the painful state of the body [6].

 The body of a child, like a young plant, requires more potassium than the body of an adult. The daily requirement for potassium in a child is 30 mg per 1 kg of weight, in an adult - 2-3 g per day, i.e. same as in sodium.

 If we receive sodium in large quantities with sodium chloride (from 2-3 g to 15 g with large losses of sweat per day) per person who is naturally healthy (salt is contraindicated for many patients), as well as with food, then potassium deficiency is more pronounced, especially with unbalanced nutrition. To cover this deficiency in potassium can be partially due to the water processed by the proposed method.

 Unlike sodium, the content of which in drinking water should not exceed 10 mg / l, a potassium concentration of 1000-2000 mg / l (100-200 times more than sodium) in drinking water is considered acceptable [7].

 Based on the foregoing, it can be concluded that sodium compounds cannot be used to soften drinking water, especially superhard water, because such water is toxic to humans. For potassium compounds, such a ban is not traced.

On the other hand, the precipitate released during water softening with potassium compounds can be used as a fertilizer, while sodium softening of water, along with calcium and magnesium compounds, contains NaCl, Na ₂ CO ₃ , which are toxic compounds plants. Especially harmful is the compound Na ₂ CO ₃ , which actually kills plants [8]. The use of precipitates obtained with sodium compounds for other purposes is also difficult due to the presence of the same sodium compounds.

Thus, from the point of view of protecting human health and the environment, the use of potassium alkali metal compounds (KOH, K ₂ CO ₃ ) is more justified than the use of sodium compounds, although the production of potassium compounds costs about two times more.

 The apparent value in terms of sodium compounds results in high mortality and destruction of soil fertility (at least through the discharge of sediments into water bodies or their storage in dumps).

The use of a mixture of K ₂ CO ₃ and KOH is explained by the fact that K ₂ CO ₃ is used to eliminate constant hardness, and KOH is used to neutralize organochlorine compounds (pesticides, etc.) that fall into natural waters from the fields. So, for example, a very dangerous organochlorine compound in the waters of Bashkiria is pesticide 2,4-a (dioxin). As preliminary studies have shown, in the presence of KOH in water, the concentration of this pesticide drops sharply.

The use of K ₂ CO ₃ in an amount determined by the dependence 48-53 W _p , where W _p is the constant hardness, is explained by the fact that in some cases there is no point in softening drinking water very much, because such water is unnecessarily devoid of calcium and magnesium compounds, which are also necessary in certain quantities for the human body.

 The human need for calcium is 600-1200 mg per day. With food, a person consumes 0.4-2 g of calcium per day [9]. But according to [10], calcium in drinking water at a concentration of 100–150 mg / l increases the incidence of the population with kidney diseases, arthritis, and polyarthritis.

 Calcium consumed with food is mainly represented by more digestible organic compounds than calcium, which is contained in water in the form of mineral salts. However, in the form of mineral compounds, calcium is necessary for the human body and is well absorbed if its content in the human diet is relatively small.

 The maximum permissible concentration of calcium in drinking water is recommended 75 mg / l [11], in water for food purposes - 10 mg / l, in water for breweries: for dark beer - 200-500 mg / l, for light beer - 100- 200 mg / l [13].

 The human need for magnesium is also 600-1200 mg / day [3]. Magnesium is extremely necessary to eliminate sclerosis, heart disease, relieve states of nervousness, fear, insomnia, eliminate sudden dizziness, fatigue and much more [3, p. 54-72].

 The maximum permissible concentration of magnesium in drinking water was recommended at 15 mg / l [11], B03 was established at 30 mg / l with a sulfate content of less than 250 mg / l [14], in France it was established 125 mg / l [12], for breweries - 30 mg / l [13].

 A person’s need for magnesium should be mainly covered by MgO (magnesium oxide), magnesium sulfate is less preferable, and magnesium chloride, for example, is toxic to humans at a concentration of 100 mg / l [15].

 Scientists have found that the absorption of calcium is enhanced in the presence of a sufficient amount of magnesium, so it is necessary to leave part of the compounds of these elements in drinking water, taking into account the area of use of drinking water and the information that water with a hardness of about 3-5 mEq / l is much more useful for people than soft water (with hardness less than 3 mEq / l) [3, p. 50]. So, according to the recommendations of the American doctor Dawson, you need to use daily 2 liters of water containing 60 mg of magnesium and 100 mg of calcium. It is estimated that if all people drinking soft water (with hardness less than 3 mEq. / L) would follow Dr. Dawson's advice and make up for the deficiency of magnesium and calcium with water containing 30 mg / L of magnesium and 50 mg / L of calcium then within 10 years for every 100,000 inhabitants there would be less than 100 deaths from heart attacks than now [3, p. 50].

Thus, based on a generalization of the above information, we adopted the amount of K ₂ CO ₃ in the proposed method, which allows you to leave the final hardness of softened water of the order of 3-5 mEq. / L (in some cases up to 9 mEq. / l, for example, when using softened water to dilute milk powder).

The introduction of KOH into softened water no earlier than 20 minutes after adding K ₂ CO ₃ in the presence of chlorinated hydrocarbons and organochlorine acids in the water, which enter the water in the form of intense environmental pollution by industrial and agricultural enterprises, makes it possible to partially neutralize these toxic compounds due to substitution of a chlorine ion for other non-toxic ions.

So, for example, when the content of 2,4-a herbicide in the Ufa tap water in the amount of 0.86 • 10 ^-4 mg / l after water treatment by the proposed method, the content of this toxic compound decreased to 0.03 • 10 ^-4 mg / l .

 If organochlorine compounds are not contained in water, then KOH can be omitted, i.e. its concentration in water will be 0, but if there is a need to convert organochlorine into less toxic compounds, then KOH can be used at a concentration of up to 50 mg / l. This is his MPC in drinking water. Part of this compound reacts with hardness salts (softens water), and part, obviously, displaces toxic chlorine from organochlorine compounds.

The need to separate the precipitate from softened water is due to the fact that this stage of the method can significantly reduce the subsequent consumption of H ₃ PO ₄ by adjusting the pH of the resulting water to 8. Otherwise, the precipitate binds the introduced H ₃ PO ₄ into phosphates and its consumption increases by 5-10 .

Pre-heating water to 35-50 ^o C allows you to accelerate the softening of water by at least 2-3 times.

 As the analyzes showed, when softening agents are introduced into heated water, the formation of flakes in water occurs much more intensively and they are much more aggregated, precipitation faster, because the flocs formed are large and heavy.

So, for example, when Ca (OH) ₂ is introduced into cold water (10-15 ^o C), a fine suspension is formed, which must be kept for at least 2-3 hours to completely complete the process of eliminating temporary hardness, and when the same compound is introduced into heated up to 35-50 ^o C water, this process ends in about 0.5-1 h (the higher the hardness of the source water, the slower the process of its softening). The same is observed with the subsequent introduction of K ₂ CO ₃ . If in cold water it is necessary at least 10-15 hours to remove the required value of constant hardness, then in heated water this process is completed in 6-7 hours.

It should be added to the above that in those cases when milder water is needed for food use, then K ₂ CO ₃ must be used in an amount determined by the dependence 53 W _p .

 The use of food phosphoric acid to bring the pH of water to a value of ≤ 8 is explained by the fact that as a result of the treatment of water with softening agents, the pH of the water can increase to 11 (with softening of superhard water). To reduce the pH to an acceptable norm and, in addition, to obtain calcium phosphate compounds in water, the need for which is about 55 mg per day for humans (in Switzerland, the multivitamin preparation Supradin is produced, containing 51.3 mg of calcium phosphate in 1 tablet and recommended for use at 1 tablet per day for adults and children), it is proposed to use dietary phosphoric acid. In this case, preliminary elimination of the precipitate from the settled water allows to increase the consumption of this additive to 15-30 ml per 1000 l of water, while the concentration of phosphorus in the water is 7-14 mg / l. Having bound to calcium phosphate, part of this phosphorus precipitates in the form of phosphates, and part remains. The content of the water-containing compound does not exceed the above-mentioned need of the human body for this compound.

 The phosphorus content in the above preparation "Supradin Roche" is 23.8 mg per tablet.

The use of a soluble part of sunflower ash or a soluble part of hard coal and ash instead of K ₂ CO ₃ to eliminate constant hardness makes it possible to expand the raw material base, reduce the cost of water treatment, and also use the proposed method for wastewater treatment (manure or sewage from food industry enterprises).

 Passing alternating current through water after introducing all additives into it allows to intensify the process of coagulation of precipitated particles, which will be shown in the examples of the method.

 Proof of the material differences of the proposed method.

 In the scientific, technical and patent literature, no information was found that the claimed combination of features is known.

 Due to the fact that the scientific and technical literature does not contain information from the claimed combination of features of the proposed method, as well as the fact that this combination of features serves to achieve the goal - to intensify the method and improve the quality of drinking water obtained by softening superhard natural water, then it meets the criterion of "significant differences".

 In the table. 2 presents examples of the proposed method, as well as examples with transcendental parameters of the method.

 Sources of information taken into account.

 1. Quick reference chemist. Compiled by V.I. Perelman, edition 6, State Scientific and Technical Publishing House of Chemical Literature, M., 1963, p. 366-370.

 2. F.I. Belan, Water Treatment, M .: Energy, 1979.

 3. Aleksandrovich Yu., Gumovska I. Kitchen and medicine. Per. with the floor. M .: Nauka, 1001, p. 224.

 4. Hibbard P.L. - J. Am. Water Works Assoc., 1934, v. 21, p. 884.

 5. Cheremisinoff P., Valent J., Wright D. - Water Senage Works, 1976, v. 123, N 3, p. 80.

 6. The Great Soviet Encyclopedia. M .: Soviet Encyclopedia, 1073, v. 11, p. 598, 599.

 7. Moore E.W. Thge desalting of saline waters: A review of the present status. Report to the subcommitee on water supply comm. on san. engin. and environm natl research couneil (24 may 1950).

 8. Radov A. S. et al. Workshop on agrochemistry. / Ed. I.V. Empty. 4th ed., Revised. and add. M .: Agropromizdat. 1985, p. 312 and 173.

 9. Taytor E.W. the examination of waters and waters supplies. P. Blakiston s son and Co., 1949.

 10. Litte A. D. Water quality criteria data book. v.2. Inorganic chemical pollution of fresh water U. S. environmental protection agency. Water pollutionn control series. wash, 1971, 273 p.

 11. International standards for drinking water. 3rd ed. Geneva, World Health Organization, 1973, p. 36.

 12. Lund H. F. (ed.). Industrial pollution control handbook. New York ets., 1971, 864 p.

 13. McKim I. M., Wold H. W. Water quality criteria. 2 nd ed. Sacramento, 1963.554 p.

 14. European standards for drinking water. 2nd ed. WHO, Geneva. M .: Medicine, 1972, p. 60.

 15. Dawcon G. W., Chuckrow A. I., Swift W.H., Control of spillage of hazardous polluting substances. Water pollution control series 15090 F02. Depart. of interior. Federal water quality administration. Wash., 1970, p. 55.

Claims (5)

1. A method of softening water by introducing into it with stirring calcium hydroxide in an amount determined by the dependence of 37 W _{in p} + 1.7 CO ₂ + 1.8 MgO, where W _{in p} is the temporary hardness of water, mmol / l, MgO and CO ₂ - the concentration of MgO and CO ₂ in the source water, mg / l, the subsequent introduction with stirring of an alkali metal compound, sedimentation and separation of the precipitate, characterized in that as the alkali metal compounds are used potassium carbonate and potassium hydroxide, and potassium carbonate is introduced in an amount determined dependence of 48 - 53 F _n, where F _n - of toyannaya untreated water hardness, potassium hydroxide is introduced in an amount of not more than 50 mg / L of not less than 30 minutes after administration of potassium carbonate and, after settling and separation of sludge water, neutralized with a food grade acid to pH ≤ 8. 2. The method according to claim 1, characterized in that the water is preheated to 35 - 50 ^o C.  3. The method according to claims 1 and 2, characterized in that phosphoric acid is used as food acid.  4. The method according to claims 1 to 3, characterized in that the soluble portion of sunflower ash in the form of a solution containing potassium carbonate 15%, potassium chloride 3.3% and potassium sulfate 1.7%, or soluble, is used as a source of potassium carbonate. part of distillery coal and ash containing, in terms of dry matter, potassium carbonate 81 - 96%, potassium sulfate 0.5 - 2.5%, potassium chloride 1.0 - 6.4% and sodium carbonate 0.5 - 10.0 %  5. The method according to claims 1 to 4, characterized in that the water after the introduction of all reagents is treated in an alternating electric field.

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