RU2286840C2 - Method for producing partially demineralized water - Google Patents

Abstract

FIELD: demineralization.

SUBSTANCE: method comprises withdrawing initial riverine water, treating the water in the clarifying units by means of liming, flocculating, removing suspended particles, additional filtering with a 5-μm cartridge filters, partial demineralization by means of nano-filtering with subsequent softening, and supplying to the boiler deaerators.

EFFECT: enhanced reliability.

1 dwg, 1 tbl, 2 ex

Description

The invention relates to the field of water treatment using nanofiltration and can be used in energy, chemical and other industries to produce feed water for power boilers with a pressure of 4.0 MPa and boilers for acid recovery plants, also relates to environmental protection in the field of water consumption and protection rivers from effluents containing harmful chemicals.

One of the problems of the Donetsk region is, on the one hand, the presence of a large amount of saline mine water that needs to be desalinated, and on the other hand, the lack of fresh water in the Seversky Donets-Donbass canal. The rational use of water resources, the search and implementation of new technologies for the treatment of natural and waste water is one of the main problems of our time.

There are various ways to clean the source water from impurities.

In Ukraine, the main way to obtain demineralized water is ion exchange and distillation. Ion exchange is widely used in many industries for the desalination of water with a salinity of up to 2 g / l [1. Yu.S. Veselov, I.S. Lavrov, N.I. Rukobratsky. Water-purifying equipment, Leningrad, Mechanical Engineering, 1985, p.21-24].

To remove the carbonate hardness of water, well-known methods of liming, ion exchange (Na-cation), and acidification are used. With high alkalinity, magnesian hardness of wastewater or with a high iron content in it, it is advisable to use a combined method of water softening: liming with further Na-cation. Wastewater treatment with lime leads to a significant reduction in the amount of pollution: suspended solids by 90-95%, COD by 65-94, BOD by 77-94, phosphate by 80-90, and the degree of water disinfection reaches 99%.

The disadvantages of the ionic desalination method are the limited or inability to use natural waters with high salinity, significant costs of chemicals and the formation of a large volume of wastewater. The nature of ion exchange is such that it requires reagents (acid, alkali, salt) to restore the exchange ability of ion exchangers 3-5 times higher than stoichiometric costs, i.e. 3-5 gram equivalents of reagents are required per gram equivalent of absorbed salts. Simultaneously with the increase in reagent costs, the unit costs for own needs of water and electricity also increase. Water consumption for own needs in the form of highly saline wastewater is 25-30% of the total volume of demineralized water by the ionic method.

In light of the above drawbacks, the non-reagent membrane method of water purification - nanofiltration is of great interest.

The nanofiltration membranes and nanofiltration of the last 5-10 years have been widely used in food (processing of beer, mineral waters, milk, etc.), the pharmaceutical industry and biotechnology. In addition, nanofiltration is used to treat natural and wastewater. In particular, coagulation and filtration are replaced by nanofiltration, water is softened [2. Russian patent No. 2222371, C 02 F 1/44, publ. 01/27/27; RF application No. 98100355, C 02 F 3/00, C 02 F 1/44, publ. January 10, 2000].

Nanofiltration makes it possible to remove 98-99% hardness salts and other sparingly soluble inorganic compounds from water. Using nanofiltration, it is possible to successfully solve the problem of removing silicon and iron compounds. Currently, certain chemical enterprises and industries have already accumulated positive experience in this area. However, the domestic experience in the development of this important area of the chemical industry has not been sufficiently studied and rarely applied in practice and has not found industrial application in the preparation of source water as feedwater for power boilers with a pressure of 4.0 MPa and boilers for utilizing acidic plants.

The closest in technical essence and the achieved result to the claimed technical solution is a method for producing partially demineralized water for supplying energy boilers with a pressure of 4.0 MPa and boilers for acid production utilizers, which consists in collecting river water, its reagent treatment in clarifiers using liming, flocculation, partial demineralization by ion exchange at the 1st stage of Na-cationization by sequential transmission through H-cation and OH-anion filters [3. Book: N. A. Yankovsky, V. A. Stepanov, B. V. Kravchenko “Creation of a closed water supply system for an industrial enterprise”, LLC “Lebed”, Donetsk - 2004, p.20-23].

In the known method, as a result of cationization, the hardness of water is reduced, the carbonate hardness is completely removed, as a result of which there is a decrease in salinity and elimination of alkalinity of water.

To load the N-cation exchange filter, KU 2-8 resin, a sulfonated styrene polymer with 8% divenylbenzene, is used. OH-anion exchange filters are loaded with weakly basic anion exchange resin - An-31 resin. After depletion of the absorption capacity, H-cation exchange filters are regenerated with high concentration sulfuric acid with preliminary regeneration of a 6-8% salt solution. OH filters are regenerated by filtering NaOH reagent solution through anion exchange bed.

A disadvantage of the known technology is the negative impact on the environment in the region, the high cost of producing feed water due to the high costs of chemical reagents, resins for water treatment and the use of salts for the regeneration of filters with the discharge of waste washing water into the environment, significant costs and heat losses during purge boilers.

In the known method used earlier at the concern, the scarce river water from the Seversky Donets-Donbass canal with a total salt content of up to 500 mg / l, with a river water intake of about 1000 m ³ / h served as the source water for purification. Large unit costs for own needs of water, heat and electricity led to a decrease in the competitiveness of the company's products on the world market in the face of fierce competition.

In addition, due to the limit of feed water, a mixture of partially demineralized water and distillate from evaporation plants was used to fuel critical production cycles. At the concern, two multistage evaporator units with I-1000 type evaporators with a distillate capacity of 265 m ³ / h were operated at the concern for producing discillate. The distillate of these plants with a salinity of up to 10 mg / L was used as feed water for the GM-50-1 boiler units with a pressure of 4.0 MPa. A mixture of river and regeneration effluents of ion-exchange ammonia water treatment with a total salinity of 3–4 g / l was used as the initial water for the pretreatments of evaporation plants [3. N.A. Yankovsky, V.A. Stepanov, B.V. Kravchenko. “Creation of a closed water supply system for an industrial enterprise”, LLC “Lebed”, Donetsk - 2004, p.55-57].

The disadvantages of the evaporative technology of demineralization of water include, first of all, the high cost of producing distillate due to high energy costs and low mobility on load.

The basis of the invention is the task of improving the method of producing partially demineralized water to obtain feedwater for boilers, excluding the intake of river water, using highly mineralized biologically treated sewage from chemical production, storm drains, mine water and others as the source water, creating a closed water consumption system using reagent-free nanomembrane technology for water purification from dissolved impurities, ensuring water quality corresponding to ebovaniyam imposed on feedwater quality company standard, preventing or substantially reducing the salinity of water sources, saving energy.

The problem is solved in that in the method of producing partially demineralized water for supplying power boilers with a pressure of 4.0 MPa and boilers for acid production utilizers, which consists in taking the initial water, its subsequent reagent treatment in clarifiers using liming, flocculation with further filtering of mechanical and suspended particles, partial demineralization by ion exchange, according to the invention, biologically purified chemical wastewater is used as a source water, high effluents, mine sewage and other effluents or mixtures thereof with a total hardness of up to 15 mEq / l and with a total salt content of 3 ÷ 4 g / l, with a total microbial number of up to 10 thousand units / ml, the water is additionally purified from suspended particles in 5-micron cartridge filters, partial demineralization of water is carried out by nanofiltration, carrying out the process of separation from dissolved impurities on nanofiltration membranes with a filtration spectrum from 0.001 to 0.01 μm at a pressure of 2.0 MPa to obtain a permeate with a salinity of 110 mg / l , subsequent softening it on Na-kati onitic filters up to a hardness of 10 mEq / l and feeding boiler boilers, diverting the resulting concentrate to biocleaning to purify microbiological and nitrogen-containing contaminants, while the initial water is chlorinated, sodium hypochlorite solution is added, an antikakipin solution and metabisulfate solution are introduced into the clarified water sodium, sulfuric acid is dosed at the input of cartridge filters in an amount necessary to maintain a pH of water of 3.0 ÷ 7.0; sodium hydroxide solution is introduced before the softeners; with a decrease in the productivity of the nanofiltration unit by 10 ÷ 15%, the membrane elements are cleaned by feeding and circulating through the membranes of washing acidic and alkaline solutions; waste water after mechanical filters, nanofiltration machines and regenerative water after softeners are discharged into storm sewers and sent to a reservoir, after which they are reused as source water.

Today, the concern has created a unique system of environmental protection in the field of water consumption and the protection of the Donbass rivers from effluents containing harmful chemicals.

For technological needs, chemical production uses waste water: it is biologically treated waste water. On the territory of the concern, these waters are treated with a modern and perfect method, eliminating the use of chemicals that contribute their share of harmful effects on the environment.

The use of biologically treated wastewater of chemical production, mine water, stormwater, drainage and others as the source water will allow to stop the intake of river water and help to solve the concern's problems associated with the lack of water resources in the Donbass.

The use of nanofiltration separation of water as part of the proposed method allows using biologically treated chemical wastewater, storm sewage, mine wastewater and others, instead of scarce river water from the Seversky Donets-Donbass canal with a salinity of 500 mg / l, as source water differing from natural waters with a high total salt content of 3 ÷ 4 g / l and a total hardness of up to 15 mEq / l, to obtain feed water with a total salt content of 110 mg / l and a hardness of 10 mEq / l for the boiler units of much better quality, with reduced energy costs, meeting the requirements of the enterprise standard STP 74-2004 “Quality Management System. Water is partially demineralized. Quality Requirements. ”

The technology for producing feed water through two-stage Na-cationization for feeding boilers has been replaced by a membrane technology for the removal of salts from a closed ecosystem by nanofiltration, followed by softening of partially demineralized water using sodium-cation exchange filters.

The inventive technology will significantly reduce the loss of feed water and thermal energy lost during the purge of boilers. Due to the decommissioning of the 1st-stage Na-cation exchange filters, the consumption of sodium chloride previously used for their regeneration will decrease by 90-95%. In addition, the filter cycle of the softeners used will increase, which will also reduce the consumption of sodium chloride and softened water for their regeneration and washing. This will create a reagent-free and environmentally friendly technology for producing feedwater to feed critical production cycles.

In the process of nanofiltration, low molecular weight electrolytes are partially delayed (for example, Na chloride - by 40 ÷ 60%, and salts with doubly charged ions - by 80 ÷ 98%, silicon is eliminated, organic compounds (alcohols, almost completely (98 ÷ 99.9%) are retained solvents, dyes, saccharides, humic and fulvic acids, pesticides, etc.).

Low working pressure and a narrow range of molecular masses of substances that are separated on these membranes are associated with their special macro- and microstructure (multilayer, ultrathin selective layers).

Water transfer through the membrane is possible if the filtration is carried out under a pressure exceeding the osmotic pressure of the initial solution.

The work of new equipment using a new technology based on nanofiltration will allow decommissioning of water demineralization using the ion exchange method and separation of water distillation, and reducing the emission of harmful substances into the environment.

Preliminary reagent treatment of the source water will allow the nanofiltration unit to efficiently and reliably carry out the process of partial demineralization. Submission of permeate after nanofiltration to Na-cation exchange filters will reduce its hardness from 15 to 10 mEq / l, prevent the formation of sludge crystals on equipment and fine filters of reverse osmosis plants.

The claimed sequence of stages of wastewater treatment and their interconnection will allow to create an effective and reliable technology of large-scale salt-free water to feed critical production cycles with relatively low specific energy consumption, reduced volumes of effluents, and improved ecology.

The drawing shows a schematic diagram of the implementation of the method.

The scheme includes a clarifier 1, a collection of lime-coagulated water 2, a mechanical filter 3, a cartridge filter 4, a nanofiltration unit 5, a collector of permeate 6, a collection of concentrate 7, and a softener 8.

The method is as follows.

A mixture of biologically treated chemical wastewater, storm water, mine wastewater with a total hardness of up to 15 mEq / l and with a total salt content of 3 ÷ 4 g / l with a total microbial number of up to 10 thousand units in ml in an amount of 627 m ³ / h, pumps are fed on clarifiers to four clarifiers 1. Before entering clarifiers 1, the initial water is heated in the winter with steam on mixing-type heaters to a temperature of 30 ° C (not specified), then passing air separators, where air and other gases dissolved in it are removed from the water, water is supplied to the lower part of clarifiers. In clarifiers 1, water is clarified, the permanganate oxidation decreases, the alkalinity of the initial water decreases and the salts of temporary hardness are removed from it. Why, in the lower part of clarifiers 1, pumps are supplied with a solution of milk of lime and a solution of flocculant. The salts of temporary hardness enter into a chemical reaction with lime, as a result of which they precipitate in the form of calcium carbonate Ca (CO) ₃ and magnesium hydroxide Mg (OH) ₂ .

Ca (HCO ₃ ) ₂ + Ca (OH) ₂ = 2COCO ₃ + 2H ₂ O

Mg (HCO ₃ ) ₂ + Ca (OH) ₂ = Mg (OH) ₂ + 2CaCo ₃ + H ₂ O

The precipitates of CaCO ₃ , Mg (OH) ₂ , Fe (OH) ₃ released from the water are removed from clarifiers when they are purged.

After treatment in clarifiers 1, water from the upper part flows by gravity into the tanks of lime-coagulated water 2. The lime-coagulated water from the tanks 2 is fed to mechanical filters 3. The volumetric supply of lime-coagulated water to each mechanical filter 3 is 150 m ³ / h .

Before the supply of lime-coagulated water to the mechanical filters 3, sodium hypochlorite is supplied to the common collector to disinfect the water and protect the membranes from biological contaminants, which, when concentrated, can be deposited on the surface of the membranes.

NaClO + H ₂ O = NaOH + HClO

At pH> 5.6, HClO = H ⁺ + Cl ^-

The dose of sodium hypochlorite is 0.5 mg / l in terms of pure chlorine. When chlorine is introduced into water, organic compounds are oxidized and coagulation improves. In addition, chlorine destroys organometallic compounds that are in a dissolved state and cannot be removed by coagulation, and increases the oxidation rate of Fe (II) compounds.

2Fe ⁺⁺ + Cl ₂ + 6НСО ₃ ^- = 2Fe (OH) ₃ + 2Cl ^- + 6CO ₂

The mechanical filter 3 is a vertical cylindrical apparatus with a drainage distribution device designed for uniform distribution and discharge of water over the entire cross-sectional area of the filter. The mixture is cleaned from suspensions due to their mechanical filtration through a layer of quartz sand or anthracite chips. These filters are designed to remove suspended and colloidal particles from water after reagent treatment of water larger than 10 microns. All n mechanical filters are connected in parallel and operate simultaneously.

Source water under pressure up to 0.7 MPa is fed into the upper part of the filter 3 through the inlet switchgear. Water flows from top to bottom a layer of silica sand or anthracite chips. The mechanical impurities of the water are retained by the filter layers, and the clarified water exits through the drainage system located at the bottom of the filter.

After the catheter filters 4, an anti-scale is introduced into the water stream, which neutralizes substances that cause scale formation to protect the membranes from insoluble and poorly soluble salts, which, when concentrated in water treatment, can precipitate on the membrane surface and form scale, in particular calcium sulfate, calcium carbonate. A solution of anti-scale is introduced based on the content of anti-scale in the treated water within 3.5 mg / l.

To bind the residual free chlorine, which can destroy the working surface of the polyamide membranes of nanofilter machines 5, sodium metabisulfite is introduced into the water stream. The dose of 2 mg / l in terms of pure product.

After mechanical filters 3, water enters the cartridge filters 4 of the membrane nanofiltration units 5.

To prevent the precipitation of salts of iron and manganese in the sediment, to prevent carbonate deposits on the membranes of the nanofiltration unit, sulfuric acid is dosed in the amount necessary to maintain a pH of 3.0–7.0 at the entrance to the carbon filter 4.

4 filter filters are designed for the final purification of water from suspended particles larger than 5 microns. As a filter material, cartridges made of porous polypropylene with a pore size of 5 microns are used. Filters 4 serve as a mixing chamber and ensure uniform distribution of reagents in the water stream before it enters the membranes of nanofiltration units.

From the filters 4, purified water from suspensions with a pressure of up to 2.0 MPa is fed to the nanofiltration unit 5.

The effectiveness of nanofiltration desalination of water depends on the specific productivity of the membranes and on the ability of the membranes to retain any substance (selectivity). In relation to the ions of various substances, the selectivity of the membranes is characterized by a number of:

Al ³⁺ > Zn ²⁺ > Cd '> Mg ²⁺ > Ca ²⁺ > Ba ²⁺ > SO ⁴⁺ > Na ⁺ > F ^- > K ⁺ > Cl ^- > Br ⁺ > I ^- > NO ^3- > H ⁺

The process of nanofiltration desalination takes place in a roll type apparatus. The source water is supplied to the outer surface of the roll filter element, moves along the turbulizer-separator in a spiral to the center of the element and is divided into two flows: partially desalted water - permeate depleted in dissolved substances and concentrated salt solution, concentrate.

The separation coefficient of the source water at the membrane plants 0.75. Of the total amount of source water, permeate is 75%, and 25% is concentrate.

Before applying permeate to softeners (Na-cation exchange filters), a solution of sodium hydroxide (alkali) is introduced to increase the permeate pH to 6.0-7.5.

After nanofiltration units 5, the permeate enters the permeate collector 6, from where permeate is transferred to the softeners 8 by transfer pumps.

The softener 8 is a vertical cylindrical apparatus with drainage and distribution devices. The softening of permeate by sodium cationization consists in filtering it through a layer of cation exchange resin containing sodium cations as exchange ions. In this case, cation exchange resin absorbs ions (Ca ²⁺ and Mg ²⁺ ) from water. It determines its rigidity, and an equivalent amount of Na ⁺ ions passes into the water from cation exchanger. During Na-cationization of hard water, the following cationic exchange occurs:

2Na ⁺ K _r ^- - + Ca ²⁺ → Ca ²⁺ + K _r2 - + 2Na ⁺ ;

2Na ⁺ K _r ^- _r + Mg ²⁺ → Mg ²⁺ + K _r2 ^- + 2Na ⁺

where K _r ^- means a complex complex of cation exchange resin.

Ion exchange processes are reversible. Therefore, when a high concentration of Na ⁺ ions in solution in contact with the cation exchange resin containing Ca ²⁺ ions and Mg ^2+, the reaction proceeds in the reverse direction (right to left). This process is used for the regeneration of exhausted cation resin (i.e., substantially Ca ² + and Mg ² + - cation exchanger) by displacing it from the previously sequestered calcium and magnesium ions with a concentrated solution of salt (NaCl).

In the process of permeate softening (sodium cationization), the permeate hardness decreases to 10 μg-eq / L.

Purified permeate with a salt content of not higher than 110 mg / l as partly demineralized water enters the collectors, preheated with steam to 50-60 ° C on mixing heaters.

Partially demineralized water is supplied from the collections to boiler deaerators.

To restore the filtering ability of the membranes, which decreases during their operation, periodic washing with washing solutions is provided. Rinsing is carried out with a decrease in the productivity of the nanofiltration unit by 10-15% by circulation through the membranes of a washing solution, for example phosphoric acid, to remove inorganic deposits and caustic soda to remove organic deposits.

In normal process control, the nanofiltration unit has a salt concentrate, washing and regeneration water as liquid waste. Wastewater after mechanical filters and nanofiltration machines and regenerative water after softeners are discharged into storm sewers and sent to a reservoir, after which they are reused as source water for water treatment with reverse osmosis plants.

The concentrate after the nanofiltration units is fed to the concentrate collector 7, from there for biochemical treatment, where it is mixed with other industrial nitrogen-containing effluents and storm water.

Biochemical purification is carried out by nitri-denitrification of nitrogen-containing water in the presence of aerobic and anaerobic microorganisms. Nitrites are oxidized to nitrates by supplying air, and then nitrates are decomposed in aerotanks using microorganisms to nitrogen and water. To maintain the purification reaction, methanol is added to the water, which is supplied as a source of readily oxidizable organics for the denitrification process.

The wastewater and concentrate treated at BWC to the established standards are sent to the reservoir and subsequently fed to the enterprise for reuse. The water cycle closes.

The process of obtaining partially demineralized water is automated and controlled by a software logic device.

Examples of the method.

Example 1 (Prototype). The source water for water treatment is river water from the Seversky Donets-Donbass canal with a salinity of 500 mg / l, with a total hardness of 3.05 mEq / l. Water, after being treated in clarifiers, is sent to H-cation filters in an amount of 549 m ³ / h, where, passing through a layer of cation exchange resin, it is purified from Ca ²⁺ , Mg ²⁺ , Na ⁺ cations. Then it comes to OH-anion exchange filters, in which the anions of strong acids SO ₄ ²⁺ , NO ₃ ^- , Cl ^- are captured from the treated water. Anionized water in an amount of 235 m ³ / h is mixed with a distillate of evaporators 36 m ³ / h and clarified water 179 m ³ / h and served to consumers. The capacity of the installation for partially demineralized water is 450 m ³ / h.

The quality of the partially demineralized water obtained complies with the requirements set forth in the standard of the enterprise STP-113-03-04-03.90-86, the total hardness was 4.5 mEq / l, and the salinity of 280 mg / l.

The consumption of the main types of raw materials for 1000 m ^{3 of} partially demineralized water amounted to: clarified water 1250 m ³ with a mass salt concentration of 500 mg / l, hardness 3.05 mEq / l; steam 0.9 t / tp; chemical reagents 1719.2 kg. The amount of wastewater was 0.92 m ³ per 1000 m ^{3 of} water. Contaminated wastewater is discharged into the environment [4. The technological regulations of the chemical preparation workshop, Concern Stirol OJSC, Gorlovka, 1996, pp. 2-3, 12-13].

The production cost of Na-cationized water amounted to 401.53 US dollars per 1000 m ^{3 of} water [5. Technical and economic calculation. Installation for obtaining partially desalted water (softened) using nanofiltration membranes. Concern Stirol OJSC, Gorlovka, 2004].

Example 2. (The inventive technology). A mixture of biologically treated wastewater, storm water, regenerative and mine water after liming and coagulation with a flow rate of 627 m ³ / h with a mass salt concentration of not more than 3.5 g / l, hardness not exceeding 15 mEq / l is fed to water treatment. At the same time, 27 m ³ / hour of water is taken for backwashing of the mechanical filters. The nanofiltration machines receive water in an amount of 600 m ³ / hour. Received permeate 450 and 150 m ³ / hour of concentrate. Permeate with a total salinity of not more than 110 mg / l and a total hardness of not more than 50 mg / l is supplied to the softeners. The products are partially demineralized softened water with a total hardness of not more than 10 μg-eq / l, total salt content <110 mg / l, the quality of which meets the requirements set forth in the standard of the enterprise STP 74-2004.

The flow of lime-coagulated water amounted to 1334 m ³ to obtain 1000 m ³ partially demineralized water. In the production of this water used 252.5 kg of chemicals per 1000 m ^{3 of} water, which is 1556.7 kg less compared to the prototype. Excludes steam consumption for the production of distillate by evaporators. The production cost of partially demineralized water amounted to 268.47 US dollars per 1000 m ^{3 of} water, which is lower than the cost of water prepared using the technology of the prototype by 243.06 US dollars [4]. There is no discharge of polluted wastewater into the environment. Comparative characteristics are given in table 1.

As can be seen from table 1, the technology for producing partially demineralized water using nanofiltration in its economic and environmental qualities significantly surpasses the technology for demineralization using ion exchange.

Using the inventive technology will reduce the river water intake by the concern by about 5 million m ³ per year, and the discharge of salts into the body due to the cessation of regeneration based on Na-cation exchange filters with sodium chloride will decrease by 2000 tons per year [4].

Table 1
COMPARATIVE CHARACTERISTICS OF THE WATER DEMINERALIZATION PROCESS No. Water Treatment Method Water The flow coefficient of river water The amount of chemical reagents, kg / t Number of polluted water discharged, m ³ per 1000 m ^{3 of} water Cost, USD per 1000 m ^{3 of} water Salt content of purified water, mg / l one. Demineralization of water by ion exchange (prototype). River water 1,334 1719.2 0.92 401.53 No more than 280 2. Demineralization of water using nanofiltration (the proposed method). Mixtures: biologically treated waters, storm drains, mine wastewater. absent 252,517 absent 268.47 No more than 110

Claims (1)

The method of producing partially demineralized water for powering 4.0 MPa power boilers and acid recovery boiler plants, which consists in collecting the initial river water, subsequent reagent treatment in clarifiers using liming, flocculation, subsequent filtration of mechanical and suspended particles, partial demineralization by ion exchange, characterized the fact that biologically treated wastewater of chemical production, storm drains, mine wastewater and other effluents or mixtures thereof with a total hardness of up to 15 mEq / l and with a total salt content of 3 ÷ 4 g / l with a total microbial number of up to 10 thousand units / ml, the water is additionally purified from suspended particles in 5-micron cartridge filters partial demineralization of water is carried out by nanofiltration, carrying out the process of separation from dissolved impurities on nanofiltration membranes with a filtration spectrum from 0.001 to 0.01 μm at a pressure of 2.0 MPa, at pH 3.0 ÷ 7.0 to obtain a permeate with a salinity of 110 mg / l, its subsequent softening on Na-cation exchange filters to a gesture it is 10 mEq / l and feeding boilers to the deaerators, discharging the obtained concentrate to biochemical cleaning to remove microbiological and nitrogen-containing contaminants, while the source water is disinfected by chlorination: a solution of Na hypochlorite is added to the source water, an anti-calcine solution and a metabisulfate solution are introduced into the clarified water sodium, before the water is supplied to the cartridge filters, sulfuric acid is introduced in an amount necessary to maintain the pH of the water 3.0 ÷ 7.0, sodium peroxide solution is introduced into the permeate in front of the softeners, while reducing the productivity of the nanofiltration unit, they clean the membrane elements by 10–15% by feeding and circulating washing acid and alkaline solutions through the membranes, wastewater after mechanical filters, nanofiltration machines and regenerative water after softeners are discharged into the storm sewer and sent to the reservoir, and then reused as source water.