SU1412232A1 - Method of preparing drinkable water - Google Patents

Abstract

The invention relates to water supply and can be used to prepare drinking water on the basis of thermal desalination plants for seawater. The aim of the invention is to improve the quality of the water, simplify the process, as well as provide waste-free technology. For carrying out the process, a solution of carbon dioxide and fine calcium carbonate — containing material taken in quantities of 62–165 and 700–1300 mg / l, respectively, are introduced into the mixing device at the same time as the thermally desalinated water. The subsequent filtering of the mixture is carried out for at least 6 minutes at a speed of up to 30 m / h through the calcium carbonate-containing charge until it becomes clogged, then it is stabilized and neutralized with ozone through the alluvial layer of activated carbon; 6 as a source of fine calcium carbonate-containing material is preferably used downloads. Using the proposed method of preparing drinking water as compared to the known, it allows to obtain bicarbonate-grade drinking water with a salt content of more than 250 mg / l and calcium concentration of more than 50 mg / l with an increase in the specific building capacity by 6 times and ensuring standards for the content of fluorine in bromine water, sodium and chlorine. In addition, the corrosivity of water is suppressed. 1 hp ff, 1 tab. g (L with

Description

The invention relates to water supply and can be used to prepare drinking water on the basis of thermal desalination plants for seawater.

The aim of the invention is to understand the quality of water and simplify the process, as well as to provide non-waste technology.

For carrying out the process, desalinated water injected a solution of carbon dioxide and fine calcium carbonate-containing material into a mixing device (for example, an ejector) in an amount of 66-165 and 700-1300 mg / l, respectively. The subsequent filtration of water is carried out until the filter loading is granulated with a contact time of at least 6 minutes and a filtering rate of no more than 3.7 m / h, after which the loading is loosened. The flushing water with a finely dispersed material is preferably sent to the process. Next, sorption purification of water in the alluvial layer of activated carbon is carried out.

The method makes it possible to more effectively carry out the enrichment process in a mixing device with high-turbulent mixing of the reacting components and developed mass transfer surfaces. Moreover, carbon dioxide is introduced in the form of a solution, which makes it possible to regulate and automate the process of carbon dioxide supply, and the excess of fine-grained material leads to a larger surface mass transfer. Then, the reaction mixture is passed through a filter with a granular load, as which any granular calcium carbonate-containing material (limestone, shell rock, marble, corals, etc.) can be used. The filter serves to purify calcium bicarbonate enriched with desalinated water from excess fine material. At the same time, a finely dispersed material, forming a alluvial layer on the surface of the grains of the enrichment filter load, gives a large phase contact surface and allows to increase the filtrating speed or shorten the contact time of the phases of the heterogeneous enrichment system;

The use of fine CaCO allows refusal from periodic loading of the filter, preparation and

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sieving load, which significantly reduces operating costs.

With an increase in the Bbmie filter's nominal resistance, which indicates its clogging with fine material, the filter is washed and the washed calcium carbonate is reused in the process.

Thus, the use of highly dispersed material increases the intensity of mass transfer during enrichment both in the mixing device and in the filtering layer of the granular charge. At the same time, distillate enrichment with bicarbonate to alci in the mixing device amounts to 70 of the total content and 30% during filtration.

The water treatment in sorption filters is carried out after purification from finely dispersed material, which means that their use is more efficient. .

The use of pressure sorption filters with a precoat layer of the AU sorbent instead of the traditional use for purifying water with granular loading filters increases the use of the sorption capacity in the alluvial layer up to 85% (instead of 25-30% in the granulated one), and also allows you to refuse thermal regeneration of the sorbent, because The loss of coal in the namgen filter is equal to the natural loss during the operation of bulk. ; filters. In addition, due to the intensification of the sorption purification process in a thin layer, the volume of structures is sharply reduced (for example, to produce 40 thousand m of water per day, instead of seven filters with a bulk layer and an area of 26.8 m each, filter with a cross section of 7 m each, equipped with a cartridge filtering system with an area of 80 m) .v

Prepared drinking water is disinfected by ozonation, which improves its organoleptic characteristics and eliminates the formation of chlorine derivatives, in particular trihalomethanes, when disinfecting with chlorine.

According to the recommended technological scheme, a distillate after heat exchangers is supplied to the high-pressure nozzle of the ejector, and at the same time to the low-pressure nozzle - carbon fiber pulp3, 4

This calcium, for example, chalky pulp from desalination batteries (OB), and carbon dioxide ftacTBop, for example, obtained by dissolving non-suspended gases (OB).

Under the conditions of highly turbulent mixing, the reaction of common phases in an ejector with a larger contact surface with an excess of fine CaCO 2 enriches with an effect up to 70%. Next, the mixture containing the undissolved solid phase and carbon dioxide 8 of the aggressive form is fed to granularly fed enrichment filters, for example, limestone. The contact time is at least 6 minutes; the filtration speed is 30 m / h. A shorter contact time Ci: (min) results in the removal of fine material from the enrichment filter and contamination of the sorption filter loading, which reduces their effectiveness. An increase in contact time leads to an increase in loading height (or the number of filters), which is associated with an increase in capital and operating costs. When filtering occurs alluvium fine material. for grains of limestone, as a result of which the specific surface of the phase contact increases per unit volume of the apparatus. This gives an additional effect of intensifying the enrichment process of the distillate calcium carbonate. When the filter clogs up, which is fixed by the pressure loss, it is rinsed with a reverse flow of water. At the same time, the washings are sent to the tank and calcium carbonate is reused.

in the enrichment cycle. The enriched dc-tyl is further directed to alluvial sorption filters for deep-reading. stacks from organic microagents and are subjected to corrective treatment |) treatment according to the scheme: fluoridation (NaF solution), stabilization (solution

Na CO,) and ozone disinfection (0,). 2 o. about

The finished water is collected in a tank, from where it is sent to the consumer.

. The optimal mineralization of drinking water of bicarbonate class is not less than 250 mg / l. The upper limit of the mineralization of drinking water is limited by sanitary requirements to 500 mg / L. Calcium ion content should be

 not less than 30 mg / l. It is advisable to obtain drinking water with salinity

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at the lower limit of the optimal range of 250-500 mg / l, since a higher concentration of salts due to the enrichment of calcium bicarbonate corresponds to higher costs of reagents.

The optimal dose of finely dispersed calcium of the base material for the conditions of obtaining 70% of hydrocarbon calcium calcium in an ejector is not less than 700 mg / l and not more than 1300 mg / l. With an increase in the amount of chalky pulp over 1300 mg / l, the output of calcium does not change, and the filter operation time is

5 clogging is reduced. Due to the fact that the operating parameters of the filters are determined by the conditions of binding on them to equilibrium with 1 mEq / l of aggressive carbon dioxide and get NIL on the ejector up to 70% Ca (HCO.j) 2, the lower limit of dosing is chalky pulp 700 mg / l. The optimal carbon dioxide dose is 66-165 mg / l.

Justification of the carbon monoxide carbon dioxide consumption at an optimal salinity range of drinking desalinated water of 250–500 mg / l is based on the following calculation. When the salt content of the original distillate

Q 10 mg / l, taking into account the increase in salt content due to the introduction of salt with seed, as well as during fluorination (NaF) and water stabilization (NajCOj) to ensure overproduction of calcium carbonate E within 4-10 mg / l CaCoi overall increase salt content for the lower limit is 42 mg / l and the top 88 mg / l.

To achieve the limiting values of the salt content range, it is necessary to obtain the following increase due to the enrichment of water with calcium bicarbonate:

dL content 250 mg / l - 208 mg / l or 2.6 mg eq / l, Ca (HCO.j),

for 500 mg / l, 412 mg / l or 5.1 mEq / l. Ca (HCO3) 5 ...

The specified amounts of hydrocarbon and calcium are obtained by dosing

 correspondingly 66 - 165 mg / l CO2, (or 3.0 - 7.5 mg-eq / l).

Deviations beyond these values of concentration allow to obtain drinking water of hydrocarbonate class with onTHManbHbLMH mineralization limits.

Example 1. The method is sold on the basis of a thermal desalinator 0

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plant operating on seed technology. using calcium carbonate-containing material. As the main components of the enrichment process of desalinated seawater, by-products1 desalination are used, resulting from the thermal decomposition of seawater bicarbonates: excess pulp with a particle size of 1 -50 microns as a fine calcium carbonate-containing material and carbon dioxide non-condensed gases of the evaporation chamber of the second apparatus of the ten-body distillation desalination flax installation.

The distillate (salt content 10 mg / l) obtained at the thermal desalination plant is fed to a high-pressure nozzle of a water-jet ejector, the carbon dioxide solution (66 mg / l), obtained by dissolving nonstandard gases of the second evaporator of a desiccant, is metered into the low-pressure nozzle installation, and chalky slurry from from stead in the amount of 700 mg / l.

After the ejector, the calcium hydrocarbonate content in the desalinated water is 147 mg / l or t, 8 mEq / ls. Then the reaction mixture is fed at a rate of 30 m / h to filters with a height of 3ym loading of shell limestone ( The content of CaCO is 98%) with a particle size of 058-2.0 mm where desalinated. water is additionally enriched with calcium bicarbonate up to 200 mg / LU Enriched water is collected in a receiving tank from which it is pumped; Iodine on fresh sorption filters with a speed of 10 m / h per 1 m of filtering G of the surface of the filter cartridge elements. The specific temperature of the AG sorbent is 3 with a particle size of 40-80 µm 1 kg / m. Oxidation of water at the top of the filter 0.1 MrOj / n

Enriched and purified desalinated water is fluorinated with sodium fluoride stabilized with soda ash to obtain a calcium carbonate supersaturation effect in the range of 4-10; mg / l CaCO, and disinfect ozonir cue.

: The table shows the data of physics - the chemical composition of drinking desalinated water obtained by the known and proposed methods.

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The salt content of the drinking water obtained by the proposed method in this example is 290 mg / l (calculated as 250 mg / l) due to the introduction of brine with chalky slurry of the desalination complex, as evidenced by the increase in the concentration of chlorides and sulfates (compared to calculated for this process). The resulting drinking water is bicarbonate grade, complies with GOST 2874-82 and sanitary standards.

Example 2 When feeding carbon dioxide on an ejector in the amount of 165 mg / l (7.5 mg-eq / l) in aggressive form and 1300 mg / l of chalky seed, 3.6 mggkv / l of Ca was obtained after the ejector, and filtration through granular shell rock with contact time t 6 min and speed V 30 m / h - 5.08 mEq / l Ca, Total salt water 500 mg / l, hydrocarbonates 358.0 mg / l, calcium 101.7 mg / l, magnesium 5 mg / l, chlorides 1-2.6 mg / l, sulfates 3.1 mg / l total sodium and potassium 19.0 mg / l, fluorine 0.7 mg / l, pH 7.2, At. In this case, the duration of the filter cycle is reduced, therefore, the process is advisable to AesFi, as in Example 1,

As regards the minimum possible filtration rate at which the positive effect is achieved, it should be noted that m / h is adopted based on the minimum possible contact time for the selected enrichment range in. the conditions for the use of standard pressure filters with a diameter of 3 m and a loading height of calcium carbonate-containing material of 3 m,

For accepted enrichment conditions, the indicated rate is optimal, since with a decrease in its performance over the final product decreases, and with an increase, aggressive carbonic acid leaks into the filtrate.

Water obtained in a known manner belongs to the sodium chloride class, does not meet the requirements of GOST on the fluorine content. The content of bromine is 3.5 times higher than the hygienic standard approved by the World Health Organization for drinking desalinated water. In addition, in the water yoder sits

a significant amount of sodium ion (122 mg / l), which is currently limited to sanitary authorities (for example, in the standards of the European Economic Community, sodium content is limited to 4-20 mg / l). Calcium is at the lower end of hygiene requirements.

, i -. . . Using the proposed method of preparation of drinking water in comparison with the existing one allows obtaining drinking water of a hydro carbonate class with a salinity of more than 250 mg / l and calcium concentration of more than 50 mg / l with an increase in the useful capacity of the structure by 6 times and minimal operating costs. The use of carbon dioxide and chalky pulp in the enrichment of a distillate with calcium bicarbonate makes it possible to reduce the size and intensity of the enrichment unit of the freshwater water and the associated operating costs. Reduces water consumption for filter rinsing. Corrosion is suppressed: water activity, leading to a significant amount of accidents in the water ducts, an increase in irrational water losses, contamination by its corrosion products, deterioration

cue of its organoleptic and sanitary - hygienic indices.

Claims (2)

1. The method of preparation of drinking water, including the introduction of carbon dioxide in the form of non-condensed. gases of desalination plants of seawater evaporators into thermally desalinated water, filtration through granular calcium carbonate, keeping loading, stabilizing and disinfecting, so that with the aim of improving water quality and simplifying the way the introduction carbon dioxide is carried out in the form of a solution simultaneously with the treatment of finely dispersed calcium carbonate-. containing material, taken in quantities of 66-165 and 700-1300 mg / l, respectively, filtering is carried out until coagulation of the granular load and, in addition, water is filtered through the washing layer of activated carbon. 2. The method according to claim 1, characterized in that, with the aim of providing non-waste technology, as a source of fine calcium carbonate-containing material, wash water is used from the regeyration of the granular load. Water The proposed method A known method Content, mg / l - TsOJ- F THEIONES pH 14.1 52.7 10.1 39.0 16.2 158.1 0.1 0.7 290.8 8.0 V22, A 30.4 19.7 250.1 16.3 73.2 0, 7 0.3 513.1 7.8