Water treatment systems and wastewater treatment technologies - exchange rate

Contents

Contents:

P

Introduction    

1. Description of demineralized water treatment unit

2. Description of water demineralization process diagram

  2.1. Demineralized water storage tanks

     2.1.1 Calculation of storage tanks

  2.2. Coal pressure filter

     2.2.1. Calculation of pressure coal filter

  2.3. Essence and methods of water desalination

     2.3.1. Ioning Machines

     2.3.2.Checks of complete desalination units by method

                   ion exchange 

     2.3.3. Calculation of three-stage ionite plant

     2.3.4. Regeneration farm

     2.3.5. Calculation of ionite plant regeneration farm 

  2.4. The essence of the degassing method

2.4.1. Removal of free carbon dioxide from water

     2.4.2. Calculation of film type decarbonizer with nozzle  from

                    Rashig rings                                                                                             

3. Basic Provisions of Station Layout 

Conclusion                                                                                                             

List of used literature                                                                   

Applications

Design Task:

Design an ionite plant (water) with a capacity of 6 thousand m3/day (complete desalination) with a reagent farm.

Introduction

In industrial enterprises of various profiles, demineralized water is spent on a variety of needs, but it is mainly used for the following main purposes:

1. For cooling of operating units, for example, condensers of steam turbines of thermal power plants;

2. To power boilers of various structures;

For cleaning of the manufactured product, for example, for cleaning textiles, food products, electronic equipment, etc.;

3. For some chemical industries.

Thus, many industries place high demands on the quality of water consumed. Especially to its salt composition and rigidity. I.e. the supplied water must be completely desalted before use.

There are several methods of desalting water. But, at the moment, the most widely used is ion exchange. There are other methods that are more economically viable with low water consumption, but they are not applicable in industrial settings. 

Complete desalting is carried out mainly by natural waters with a small suspension content. The main pollutants of such waters are calcium and magnesium ions, which cause the stiffness of water, nitrates, free carbon dioxide, which is very aggressive, sodium ions, sulfuric acid anions, chlorides, etc. The concentrations of all these substances vary widely, so there are different schemes for desalination with ionites, and each time they are individual.

For example, in the preparation of additional water for the main cycles of modern thermal and nuclear power plants, the water desalination method is very widely used, based on the sequential implementation of H-cation and ONanionation processes. In the H-cation process, the cations contained in the water are replaced with H + ions; in the ONanionation process, the anions contained in the water are replaced with ON- ions. Interacting with each other, the H + and OH ions form a  water molecule.

The very simple method of ionite desalination of water is implemented using various technological solutions aimed at achieving the required effect of water purification with minimum costs. At existing prices for ionites, reagents and water treatment equipment, the method of chemical desalination of water using granular ion-exchange materials is economically feasible.

The preparation of demineralized water at the TPP, as a rule, is combined with its desalination. The need to remove very weak silicic acid from the water predisposes the use of strongly basic anionites.

Depending on the requirements for the quality of demineralized water and the composition of impurities of the source water, the basic process diagrams for demineralizing water are carried out with a different number of ionization stages. When natural waters are demineralized, clarified water undergoing the corresponding preliminary treatment steps is ionized. Coal filters are included in ionite plants, since in demineralization, the preliminary release of water from suspended substances, iron and organic impurities is of great importance. The oxidability of the water to be demineralized shall be within the range of 1-2 mg/l of oxygen. If this value is greater, activated carbon filters are provided at the beginning of the circuit.

Description of demineralized water treatment unit

Water taken from the natural source in the amount of 6 thousand m3 per day is supplied to the storage tank using pumps. Installation of storage tank is required to ensure uninterrupted operation of water treatment facilities. Initial characteristics of incoming water

After averaging, water flow is directed to desalting station. Which includes:

Pressure filters loaded with activated carbon to reduce chroma, odor, turbidity (i.e. fine suspended substances causing premature ionite attrition), iron content and oxidability up to 1 mg/l.

Three stages of Nkathionite and three stages of anionite filters, which remove all anions and cations from the water (purification efficiency is 99.9%).

Decarbonizer to remove free carbon dioxide, the concentration of which is reduced to 3 mg/l.

Description of water demineralization process diagram

The process diagram of water desalination is given in Fig. 2.

2.1. Sewage storage tanks

Wastewater storage tanks are installed in order to accumulate this wastewater at relatively low wastewater consumption and at relatively constant concentrations to ensure uninterrupted operation of subsequent treatment facilities. Water is collected in the tanks, and then gradually removed from them for further purification. Storage tanks are rectangular in plan, made of reinforced concrete.

2.1.1. Calculation of intake tanks 

Calculate the storage tank for the incoming water flow for further desalination as follows.

Coal pressure filter

Experience with ionite plants has shown that anionites greatly reduce their exchange capacity over time. The most likely explanation for this phenomenon is the irreversible absorption of certain types of organic substances by anionite. 

Therefore, filters loaded with activated carbon should be installed in the schemes of plants for ionite demineralization of water in front of Nkathionite filters of the first stage. Brands of activated coals are different: BAU, AG3 AG-5, etc.

But, in addition to organic substances, suspended substances and iron are also contained in the source water, which also negatively affects the purification process. These impurities must also be removed by activated carbon filters. The purpose of these filters is to extract organic and suspended substances from demineralized water. Such filters reduce the oxidability of water subjected to desalination to 1-2 mg/l of oxygen.

Such filters can be regenerated by batch steaming or replaced with activated carbon once every 4-6 months.

The pressure filter is a closed steel tank (vertical or horizontal), designed for an internal pressure of up to 6 atm. In some cases, this allows you to supply filtered water to the dilution network of pipes with a sufficient head.

Pressure filters are used without gravel underlying layers, with tubular drainage. In addition to the drainage system for the removal of filtered water and the distribution of water during washing, a distribution system is arranged, through which compressed air is supplied. If the drainage design ensures uniform distribution of compressed air, a separate air distribution system may not be provided. The drain is a collector running along the cross-sectional axis of the filter, with branches through 250300 mm.

In pressure filters, special drain systems of caps are used, through the slots of which water passes. But loading grains are not allowed. Water supply to the pressure filter and washing water discharge is carried out either through a funnel facing the wide end up, or through an annular hole pipe (see Fig. 3)

Since the concentrations of suspended particles in the source water, oxidability and iron do not meet the requirements of ion exchange purification immediately after the tank, carbon vertical pressure filters with steam recovery are installed before ion exchange.

2.3. Essence and methods of water desalination

Desalination of water is meant to reduce the content of salts in the source water to a certain concentration. Depending on the required degree of purification, complete and partial desalination of water is distinguished.

Complete (deep) desalination of water is the elimination of all the salts dissolved in it from the water, usually up to a salt content of several milligrams or fractions of milligrams per 1 liter, depending on the requirements of consumers. 

Complete desalination of water can be achieved by one of the following methods: distillation in evaporators - thermal method; ion exchange is an ionite method. The electrodialysis method - the electrochemical method - in multi-chamber electrodialysers filled with special mixtures of ionites is very promising. 

Partial desalination, in addition to the above three methods, can be achieved by liming or barite softening; during H-cation of water; freezing of water. The latter method has not yet found wide application.

When choosing the method of desalination of water, it should be taken into account: the salt content of the source water specified by the productive desalting plant, the cost of heat sources, electricity, required chemicals and materials.

Let us discuss in more detail the methods of complete desalination of water:

Desalting water by distillation.

The production of demineralized water by evaporation and condensation of steam is the oldest and up to now widespread method of demineralizing water with increased calcined dissolved residue. Evaporators of different types are used to desalinate water by distillation. They differ in performance, design and type of energy consumed. Electric or steam distillers are usually used, which is very expensive.

Evaporators are low pressure boilers where incoming water is converted into steam and a concentrate with significant salt content, which is continuously or periodically discharged. To obtain high purity water, it is necessary to ensure slow boiling so that heavy impurities are not carried away by steam and do not enter the distillate. In order to reduce energy consumption, distillation plants are multi-stage. However, with an increase in the number of evaporation stages, the area of ​ ​ the total heating surface of the apparatus increases and, accordingly, capital costs increase. 

It should be noted that evaporators, heat exchangers, piping, fittings and installations must be made of transparent quartz or platinum to obtain desalinated water of particular purity. Other materials and metals are not suitable for them. 

Electrochemical method.

The essence of electrochemical desalination of water lies in the fact that in the electric field created when direct current passes through the water layer, ions of salts dissolved in water are transferred, wherein cations move to the cathode and anions move to the anode.

Space between cathode and anode is divided into three compartments by means of cathode and anode diaphragms. In the middle compartment is demineralized water. Under the action of direct current, anions pass into the anode section, and cations into the cathode section.

This method requires very expensive equipment and high energy costs.

Thus, both methods are not widely used on an industrial scale.

Water desalination by ion exchange

Pure water, compared to the water produced by single distillation on an industrial scale (which is very important), gives it treatment on ion exchange resins - cationites and anionites, previously converted to H + and O- - form .

Let's talk about this method, because to solve the problem of complete desalination of water, it is the most optimal and draining in terms of the degree of purification, and draining in terms of economic efficiency.

With this desalting method, cations and anions of salts dissolved in it are removed from the water. Depending on the scheme of demineralization plant and its operation mode, almost complete desalination of water can be achieved.

Desalting is carried out using ionites. Ionites are substantially water-insoluble polymeric substances having a mobile ion capable of exchange under certain conditions with ions of the same sign in solution. Upon contact with water, the ionites swell and increase in volume by 1.52 times.

An important characteristic for ionites is their exchange capacity (full, static, dynamic and working). The exchange capacity of the ionite is expressed in terms of the mass of the substances to be sorbed per unit mass or volume of the ionite.

During purification, the ionites are sealed. As the ionites are saturated, they are regenerated. Before regeneration, they are loosened with purified water. After regeneration, they are washed with water .

The regeneration products are eluates - solutions of acids and alkalis containing components extracted from ionites. The first portions of eluates are most concentrated in the extractable components. They are neutralized or processed in order to dispose of valuable products. Neutralization is carried out by mixing acidic and alkaline eluates, as well as by additional introduction of acid or alkali.

Properties of cationites

The exchange of cations into cationite occurs according to a typical reaction:

Me++ H [K] Me [K] + H +

where [K] is a complex cationite complex; Me + - salt cations to be extracted from water.

Cationites are artificial and natural mineral and organic. Mineral cationites, despite the low cost, were not widely used due to low exchange capacity and insufficient resistance. More often, organic artificial cationites are used. Let's stop at the last. 

When water is filtered through the Nkathionite filter, H-ions are transferred to water and anions are converted to the corresponding mineral acids. The dry remainder of the water is reduced .

Cationites are synthetic high molecular weight compounds. Of great importance is the selective ability of cationites.

Cationites are divided into weakly and strongly acidic in their properties.

Strong acid cations allow the process to be carried out in any media, and weak acid cations in alkaline and neutral ones. Therefore, we choose strong acid cationite KU-2 for loading cationite filters of all three purification stages.

Regeneration of cationite - reverse substitution of its sorbed ions with hydrogen ions - is achieved by washing the treated cationite with sulfuric acid

Properties of anionites

Anionites are artificial resins obtained by polycondensation or polymerization of certain organic compounds.

The exchange of anions on anionite is carried out according to a typical reaction:

2 [A] Oh + H2SOO4 [A] 2SO4 + 2H2O.

By their properties, they are divided into weakly basic and strongly basic anionites.

Weakly basic anionites can only absorb strong acid ions. They are used to unload strongly basic anionite filters.

Strongly basic anionites differ from weakly basic ones in that, in addition to ions of strong acids, they can also absorb ions of weak acids, for example, carbonic, replacing them with ions of ON-.

Therefore, based on the initial data, we install filters with both strongly basic and weakly basic anionites in the ionite plant.

2.3.1. Ioning Machines

Ion-exchange filters of water treatment plants are very close in design to mechanical pressure filters. Different characteristics are used when classifying filters. According to the method of creating the water head, which is necessary to overcome the hydraulic resistances arising during filtration, all ionite filters are pressure filters, i.e. they operate under the pressure created by pumps.

By the nature of the ion exchange material forming the filter layer, ionite filters are divided into cationite, anionite and mixed-action filters. In the latter, the working layer is represented by a mixture of cationite and anionite. But mixed-action filters are very difficult to operate (regeneration, thorough loosening, low consumption). 

Thus, we choose conventional anionite and cationite pressure filters.

Depending on the size of the particles of the filter medium and the method of creating the filter layer, fill and wash filters are distinguished. Creation of a filter layer in bulk type filters is achieved by filling the vessel body with ion-exchange material with relatively large particle size (0.3-1.5 mm). In filters of alluvial type, filtering layers are created by washing powder ionites (particle size 50-70 mcm) onto filtering elements located inside the apparatus body. Currently, the first place in terms of latitude of application belongs to bulk type filters. 

According to the method of performing technological operations of regeneration, ionite filters of bulk type are divided into parallel-current, counter-current, step-counter-current and filters with remote regeneration. The method of remote regeneration is based on the use of special equipment for regeneration; and removing the filter layer from the ionite filter. The remaining regeneration methods involve regeneration of the spent ionite layer in the ionite filter housing. In parallel-exact filters, water and regeneration solution are allowed to pass through the ionite layer in the same direction. In countercurrent filters, water and regeneration solution are passed through the ionite layer in opposite directions . In step countercurrent filters containing two loading layers, the kind and the regeneration solution are passed through the loading layers in reverse sequence. Bulk filters with the same type of ion exchange material are also divided according to their technological purpose into filters of the 1st, 2nd or 3rd stage. Typically, these filters differ in the grades of ionites used, the height of the filter bed, and the filtration rate. According to location in space of longitudinal axis of apparatus filters are divided into vertical and horizontal ones.

Thus, we install pressure bulk vertical parallel-exact filters at all cleaning stages.

2.3.2.Checks of complete demineralization plants by ion exchange method

Processes of ion-exchange purification of water, including alternating stages of sorption and regeneration of ionites, are carried out in apparatus of periodic or continuous action. Ion exchange purification is carried out by sequential filtration through cationites and anionites. Depending on the required degree of purification, a single, two-stage three-stage purification scheme is installed.

In a single-stage desalting scheme, Nkathionite filters and anionite filters are installed, which allows reducing the total content of dissolved salts to 2-10 mg/l, but the silicic acid anion practically remains unsettled. In the interval between the filters or at the end of the unit, a decarbonizer is installed that removes free carbon dioxide from the water. In a single stage scheme, water is passed through a Nkathionite filter loaded with strongly acidic cationite sorbing Ca2 +, Mg2 +, Na + cations and replacing them with hydrogen ions. The salt content of water is reduced by an amount equivalent to the alkalinity of the source water, which corresponds to the bicarbonate ion content in it. The water is then passed through a low-base anionite filter in which sulphate and chloride ions are exchanged for the OH-anionite ions. This scheme does not meet the requirements of our project.

When desalting water in two stages, the total content of dissolved salts in water can be reduced to 1-3 mg/l, the content of silicic acid - to 0.15 mg/l. In this case, the groups of cationite filters and anionite filters are alternated. Water is passed first through the first stage Nkathionite filters with loading with strongly acidic cationite, which retains calcium and magnesium cations, and then through the first stage anionite filters with loading with weakly basic anionite, which retains strong acid ions (sulphates, chlorides, nitrates). The water then passes through the II stage Nkathionite filters containing sodium cations, and finally through the II stage anionite filters charged from the strongly basic anionite. Silicic acid anions and free carbon dioxide residues not eliminated in the decarbonizer, which is located after the Nkathionite filters of the second stage, are recovered here.

We choose a three-stage scheme. If it is necessary to remove not only calcium and magnesium ions from the water, but also iron, sodium sulphates, chlorides, etc. A three-stage cleaning scheme shall be provided. This allows reducing the salt content to 0.05 0.1 mg/l, silicic acid to 0.02-0.05 mg/l. This satisfies higher requirements for water quality, for example in the preparation of feedwater for high and ultra-high pressure boilers. At the same time, all three stages of Nkathionite filters are loaded with strong acid cation "KU2, anionite filters of the first two stages are loaded with weakly basic anionite AN2F, and anionite filters of the second and third stages are loaded with salt base anionite AB17.

After Nkathionite filters of the II stage, a decarbonizer is installed.

We accept a three-stage purification scheme for desalination of the water given to us.

2.3.4. Regeneration farm

Depending on the requirements for demineralized water, the preparation of regenerative solutions can be carried out on the initial, clarified, or on demineralized water. Similarly, depending on the requirements for demineralized water, the washing of ionites from regeneration products and the loosening of the charge can be carried out by the original clarified water, Nkationated water or demineralized water.

Since the requirements for the water we clean are quite stringent, that is, it is necessary to obtain completely demineralized water for the subsequent supply of high pressure boilers, we will use demineralized water in the preparation of regeneration solutions, the supply of washing and flushing waters.

Note that the flushing and blasting water tanks are arranged together, i.e. we install one tank and divide it into two parts.

For the regeneration of cationites and anionites of demineralizing plants, the organization of regeneration farms is provided at purification stations, which include: tanks for storing concentrated solutions, solution tanks, meters, vacuum pumps, flowmeters, etc.

Sulfuric acid is selected for regeneration of Nkathionite filters. And for the regeneration of anionite filters of the first and second stages, we will provide for the supply of sodium hydroxide solution (since it is necessary to remove silicic acid). Regeneration of third stage anionite filters is carried out with ammonia solution.

So that sulfuric acid is supplied to Nkathionite filters at the required concentration and in sufficient amount we envisage the development of sulphuric acid at our desalting station, which is shown in Figure 6. The acid farm shall provide a monthly supply of reagent. Due to the fact that the railways in which sulfuric acid is supplied have a carrying capacity of up to 5060 tons, the volume of storage should ensure their complete emptying. Concentrated acid is usually delivered to water treatment plants in railway tanks, from where it is discharged into acid storage tanks. The drain is due to vacuum in this tank created by the vacuum pump. Acid is drained from the storage tank into the gauge, also by creating a vacuum in the gauge. It is sucked from the meter by the ejector and already in the water of a one percent solution is supplied to the regenerated filter. The ratio of water to acid supplied to the ejector to obtain a one percent solution is controlled by the flow meter readings on the water line and by lowering the acid level in the gauge water glass. Sulfuric acid solutions with a concentration of more than 11.5% should not be used, since the risk of stacking of cationite increases due to an increase in the concentration exceeding its solubility in water.

For supply of caustic soda solution for regeneration of anionite filters we envisage device of edconat farm, shown in Figure 7. 

The scheme of this farm provides for the possibility of using both liquid and solid caustic soda, with its dissolution in a special tank. In tank 1, solid caustic soda is dissolved or the finished concentrated solution is drained from special containers or from storage tank 5. If it is necessary to supply 2% sodium hydroxide solution to the anionite filter, the concentrated solution of the latter from the gauge 8 is pumped into the pipe 11 going to the filter. The ratio between the amount of water supplied through the conduit 11 and the solution of concentrated caustic soda supplied by the pump 9 to obtain a given concentration of solution can be established by the readings of the flowmeter 13 on the conduit 11 and by the flow rate of concentrated solution from the meter 8 (on the water metering glass).

To supply 0.2% sodium hydroxide solution, a dosing pump 10 is used, which supplies the necessary dose of concentrated alkali to obtain 0.2% sodium hydroxide solution in pipe 11.

2.4.1. The essence of the degassing method

The gases whose removal is most often necessary during water treatment are; carbon dioxide, oxygen and hydrogen sulfide. All three gases are corrosive gases that cause or enhance metal corrosion processes. Carbon dioxide, in addition, is aggressive in relation to concrete.

A set of measures related to the removal of dissolved gases from water is called water degassing.

There are chemical and physical methods of water degassing.

The essence of the former lies in the use of certain reagents that bind gases dissolved in water.

The physical methods of removing dissolved gases from water are as follows: water containing the gas to be removed is brought into contact with air if the partial pressure of the gas to be removed in air is close to zero; or conditions are created under which the solubility of gases in water becomes close to zero.

By means of the first intake, i.e. by aeration, free carbon dioxide is usually removed from the water, since the partial pressure of this gas in the atmospheric air is close to zero.

Degasser Classification

The removal of dissolved gases from water during water treatment is carried out on degasifiers of various types, which, according to their design, the nature of the movement of water and air and the environment in which the degassing process is carried out, can be classified as follows:

Film degassers, which are columns loaded with a particular nozzle (wooden, Rashig rings, etc.), along which water flows with a thin film. The nozzle serves to create a developed surface of contact between water and air injected by the fan towards the water flow.

Bubble degassers in which compressed air is blown through a layer of slowly moving water of degassed water.

Vacuum degassers in which special devices (vacuum pumps, steam or water jet ejectors) create a pressure at which water boils at a given temperature.

2.4.1. Removal of free carbon dioxide from water

The CO32, HCO3- and CO2 carbon dioxide ions in the water are linked by carbon dioxide equilibrium. The part of free carbon dioxide that is in equilibrium with bicarbonates is called equilibrium and does not enter into chemical reactions. Excessive free (or aggressive) carbon dioxide, in contrast to equilibrium, is very active. Its presence in the water causes corrosion of concrete structures and metal pipes.

The method of removing free carbon dioxide by the aeration method is widely used in water treatment plants. Carbon dioxide is removed in devices called decarbonizers, and the process itself is called decarbonization. For this purpose, it is most advantageous to use film decarbonizers loaded with a nozzle and equipped with a fan to force air from below, i.e. in a direction opposite to the top-down water. A schematic diagram of the operation of the film type decarbonizer is shown in Fig. 8. The decarbonizer is a cylindrical steel tank 1, inside of which there is a nozzle 2, consisting of wooden boards staggered with a gap, or of Rashig rings, which are ceramic rings with a size of 25x25x3 mm. Water is supplied to decarbonizer from above through branch pipe 4. It is drained from shield 6 through distributing nozzles 5 onto nozzle surface. The treated water washes the nozzle elements with a thin layer, and air supplied to the decarbonizer by the fan through the branch pipe 7 moves towards it. The carbon dioxide removed from the water passes into the air and with it is discharged from the decarbonizer to the atmosphere through the branch pipe 3. The purified water flows into the decarbonizer tray and through the hydraulic gate through the branch pipe 8 enters the decarbonizer water tank, which is located under the decarbonizer bottom.

2.4.2. Calculation of film type decarbonizer with Rashig ring nozzle

To remove free carbon dioxide from the water after cation, we choose a physical method for removing gas dissolved in water - aeration. We choose a film-type decarbonizer with a nozzle of Rashig rings. This choice is due to the fact that Rashig rings compared to other types of nozzles have a number of advantages: a large specific surface area, a small weight of a unit volume, a significant free volume. Because of this, degassers loaded with Rashig rings occupy smaller areas and have a lower height. They also provide a more stable degassing effect than degatters with a wooden chord nozzle.

The film-type decarbonizer reduces the concentration of dissolved carbon dioxide in decorbanized water to 3-7 mg/l, which corresponds to MPC.

Basic Provisions of Station Layout

Composition of treatment facilities is determined on the basis of the results of initial water analyses and the requirements that are imposed on the quality of treated water.

The basic principles of the treatment plant layout are as follows: 1.) In ensuring a compact layout of all structures and office premises; 2.) in the creation of conditions of gravity movement of water throughout the whole complex of knowledge structures (if this is feasible).

When placing individual structures, it is necessary to strive to reduce the length of water pipelines between them, as well as to implement the possibility of commissioning and further expansion of structures without terminating their operation. Equipment and fittings shall be easily accessible for repair and maintenance .

All technological structures and office premises of the station are economically feasible to combine (block) in a common building. This facilitates the operation of the station and reduces the amount of capital costs during construction.

The main dimensions of the water treatment facilities shall be taken according to the pitch between the columns and the axes of the walls, taking into account the main standard sizes of the prefabricated reinforced concrete elements produced by the industry.

Pumping and transformer stations, chlorine and ammonia warehouses, a boiler room, workshops and a passing booth are allowed to be located on the territory of the water treatment plant. 

Based on the above principles of the treatment plant company, we arrange a water desalination plant in one building. In this station, we provide a pumping station in the basement, a bathroom for staff, showers, a rest and meal room, a control room, a laboratory, we install concentrated sulfuric acid, concentrated caustic soda and ammonia in separate rooms, as well as equip the station with a fan, decarbonizer, meters, vacuum pumps, tanks for various purposes, coal and ionite filters of various stages. The building provides for the passage of trucks.

 For the plan of the building and its section, see the annexes.

Conclusion

As a result of this course project, a scheme for the complete desalination of water was developed. The content of salts in water has decreased to standards that allow the further use of demineralized water at thermal power plants. On the basis of this, it is possible to draw conclusions about the shortcomings and advantages of the developed scheme.

Disadvantages:

The eluates and washings from the ionite filters have increased acidity or alkalinity. Therefore, the discharge of such solutions into the sewage system is impossible. They need to be neutralized or disposed of. And these processes, in turn, lead to the development of additional technological schemes and investments;

The need for large amounts of concentrated reagents, which entails high costs, provision of safety measures during their storage and operation of structures. A large number of structures are also needed to dissolve, transport and store them. The structures are very voluminous;

The treatment plant should be arranged near the railway, since such volumes of reagents are delivered via it; 

In the scheme, desalting is the number of structures, since the source water is quite strongly mineralized.

Benefits:

All water after purification complies with MPC standards and can be used by enterprises with stringent requirements for demineralized water quality;

Demineralized water is used to prepare reagent solutions and wash ionite and coal filters of the station itself;

Wastewater treatment uses similar facilities, which simplifies their construction, operation, and, therefore, cost;

Water desalination by ion exchange is used on an industrial scale;

The relative cheapness of ionites, compared with the cost of electricity when cleaned by other methods.