RU2747102C1 - Wastewater treatment installation - Google Patents

Abstract

FIELD: water treatment.SUBSTANCE: invention relates to the field of water treatment, industrial and domestic wastewater, wastewater sludge, and more precisely to devices for the treatment of wastewater from chemical workshops of thermal power plants with the receipt of purified water returned to the technological cycle, and the release of salts of sulfate and sodium chloride in the form of commercial products or hazard class 4 waste for disposal. The installation consists of a wash water homogenizer, an eluate accumulator, a sulfuric acid accumulator, an alkaline agent accumulator, two granular filters, two reverse osmosis units, two flow mixers, a reactor for reagent softening, a clarifier, a filter press for dehydration, two evaporators-crystallizers and two centrifuges. In this case, the rinse water equalizer is connected to the first granular filter, which in turn is connected to the first reverse osmosis unit, which is further connected to the first flow mixer; an eluate accumulator and an alkaline agent (milk of lime and soda) accumulator are connected to the first flow mixer, which in turn is connected to the reactor for reagent softening, where a mixed stream of eluates, alkaline agents and concentrate of the first reverse osmosis unit is fed; the reactor, in turn, is associated with a clarifier, which is associated with a filter press and a second granular filter; the filter press, the second granular filter and the sulfuric acid accumulator are connected to the second flow mixer, which in turn is connected to the second reverse osmosis unit, which in turn is connected to the first evaporator-crystallizer operating on the principle of crystallization by cooling, which is connected to the first centrifuge, which is connected to the second evaporator-crystallizer, working on the principle of vacuum evaporation, which is connected to the second centrifuge.EFFECT: increased efficiency of wastewater treatment.6 cl, 1 dwg

Description

The invention relates to the field of water treatment, industrial and domestic wastewater, wastewater sludge, and more precisely to devices for the treatment of wastewater from chemical workshops of thermal power plants with the receipt of purified water returned to the technological cycle, and the release of salts of sulfate and sodium chloride in the form of commercial products or hazard class 4 waste for disposal.

The intensive development of the national economy and, in particular, the operation of the CHP plant sharply raises the issue of cleaning wastewater with a high content of suspended solids, contaminated with heavy metals and other components.

A large number of various contaminants in wastewater determines the numerous methods, techniques and technological schemes used in their purification.

Based on the current state of the art, it is possible to identify the most common methods of purification of industrial saline wastewater, incl. waste water from energy enterprises. These methods are:

- reagent (designed for cleaning from heavy metals and sulfates, neutralizing effluents, intensifying the processes of decantation and dehydration of sludge);

- settling (designed to remove suspended solids);

- filtration (designed to remove suspended solids);

- baromembrane methods (designed for deep purification and desalination of effluents by membrane methods);

- sorption methods (designed for deep post-treatment, selective extraction of solution components);

- electrochemical methods (concentration of sulfate anions by the electrodialysis method with ion-selective membranes);

- thermal methods (desalination by evaporation and concentration of waste water);

- ion exchange (selective extraction of ions).

The existing cleaning methods can be divided into four groups:

1) chemical - neutralization, precipitation and oxidation;

2) mechanical - averaging, filtering, settling (clarification), filtration;

3) biological - aerobic oxidation and anaerobic digestion;

4) physicochemical - flotation, sorption, electrochemical (electrocoagulation, electrolysis, electrodialysis), extraction, ion exchange, membrane methods, thermal methods (evaporation, combustion, sludge drying), aeration, crystallization, etc.

Chemical methods are used to neutralize acidic and alkaline effluents, purify salts of heavy metals (chromium, cadmium, lead, etc.), cyanides, phenol, and cresol dissolved in water.

Mechanical methods are used to purify wastewater (SW) from large contaminants: wire, rags, wood, coal, sand, earth, scale, suspended organic matter, oils and petroleum products, etc.

Biological methods are used to purify wastewater from organic pollutants dissolved in water (phenols, thiocyanates, etc.), purify domestic wastewater after baths and laundries, catering units, etc.

Physicochemical methods are used to purify wastewater from all types of pollutants in dissolved, suspended, colloidal and other types of state.

Wastewater treatment methods are determined by their physicochemical and technical properties. In most cases, purification by one method is ineffective, and therefore various methods are combined in the technological schemes of water processing. Only in this way can a high effect of wastewater treatment be achieved. The choice of a specific wastewater treatment scheme is usually preceded by a comparative feasibility study of several options, taking into account environmental protection and environmental impact assessment of the project.

Modern technologies make it possible to purify almost any water and make it suitable for household needs and even for drinking. Everything is determined by the feasibility of costs to achieve a particular level of wastewater treatment in accordance with the environmental standards. Let's take a closer look at some of these methods.

The most widespread and simplest method of wastewater treatment is the reagent method. Its essence lies in the introduction of reagents into the effluents to ensure such processes as neutralization of effluents, coagulation and flocculation, and chemical precipitation.

Coagulation and flocculation processes facilitate the removal of suspended solids and colloids by concentrating them in the form of flocs (floccules), followed by separation in sedimentation, flotation and / or filtration systems. Coagulation is the process of destabilizing colloidal particles by adding a coagulant that introduces multivalent cations into the colloidal medium, which can be either free or bound to an organic macromolecule (cationic polyelectrolytes). Flocculation consists in the agglomeration of particles with the formation of microflocules, which then combine into larger floccules. This process can be optimized by adding a flocculant reagent.

When treating water using chemical precipitation (in addition to the coagulation-flocculation process), one or more mineral compounds are mainly insoluble. In each specific case, it is necessary to introduce ions into the water (in the form of a soluble reagent), which, together with the impurities to be removed, form a precipitate of a less soluble compound.

The main disadvantages of reagent wastewater treatment methods: a large amount of toxic waste - sludge with a high moisture content, the impossibility, in most cases, of wastewater treatment to the maximum permissible concentration (MPC), high consumption of reagents, leading to additional salinization of wastewater. Therefore, the return of water to production when using reagent cleaning can only be partial.

Sedimentation is the simplest, least energy-intensive and cheapest method of separating coarse impurities with a density different from that of water from wastewater. Under the influence of gravity, dirt particles settle to the bottom of the structure or float to its surface. The relative simplicity of the settling facilities determines their widespread use at various stages of wastewater treatment. Structurally, sedimentation facilities are divided in the direction of water movement into vertical, horizontal, radial and thin-layer sedimentation tanks.

Clarification of water is based on the settling of particles (suspended solids) with a density greater than water when it moves at low speed. The sedimentation of suspended particles occurs at different rates and depends on their shape, size, density, surface roughness and water temperature.

Filtration is a separation process in which a mixture of a liquid and a solid phase is passed through a porous medium (filter media or filter material), which retains the solid particles and allows the liquid phase (filtrate) to pass through. There are two main types of filtration: depth-of-bed filtration (filtration on a granular bed) and filtration with a filter cake layer (filtration on a filter base). Filtration on a granular bed is carried out in filters with a granular load.

As a load for filtering wastewater, the following are used: sand, crushed anthracite, expanded clay, burnt rocks, heavy minerals (granite, ilmenite, magnetite), synthetic granular materials (polystyrene, polyethylene, etc.) and other materials.

The filter layer is the main element of the filter design; it is made of sorted granular material, most often of quartz sand, with a particle size of 0.5 to 2.0 mm.

Sludge dehydration is carried out in order to reduce its volume and change its physical state: from liquid to pasty and drier state.

The sludge can be dewatered by pressure filtration (belt or chamber filter presses) or centrifugation. In belt filter presses and centrifuges, the dewatering process is continuous, in chamber filter presses it is periodic.

Filter presses are a group of aggregates for separating (filtering) the solid phase of suspensions. A characteristic feature of the operation of such units is their periodic operation (the cycle of operation is divided into separate phases), as well as external forced supply of filtrate under a relatively high pressure (up to 2-6 MPa). The general name of this type of filters comes from the design of the sealing mechanism of the working chambers, similar to that for mechanical presses or hydraulic presses.

Filter presses are widely used to filter suspensions with a relatively small proportion of solids. Depending on the type of construction, frame and chamber filter presses, as well as chamber-membrane filter presses with a similar operating principle are distinguished. Under the action of an external pump, the filtered suspension enters the inner cavities of the frames / chambers of the filter. In this case, the liquid phase passes through the filtering partitions and through the drainage channels is discharged into a sump or a closed collector (in the first case, they speak of an "open filtrate outlet", in the second - of a "closed filtrate outlet").

Filter presses are characterized by a large filtration surface per unit area, a significant pressure drop (i.e. powerful driving force), no moving parts, and the ability to control the operation of individual plates.

In addition, the advantages of chamber-membrane presses include:

- a wide range of applications;

- the highest concentration of dry matter in the cake;

- adaptation to changing filtration conditions and concentrations of dry matter in suspension;

- small dimensions in comparison with performance;

- the best results when washing the cake;

- low power consumption.

Sludge dewatering in centrifuges is the process of separating heterogeneous systems (emulsions, suspensions) under the action of centrifugal forces in a rotating drum.

The filter centrifuge is an apparatus for separating suspensions using centrifugal force. The main component of the device is a rotating drum, the inner surface of which is covered with filter material.

When the drum rotates, centrifugal force acts on the suspension. As a result, the filtrate passes through the partition, and solid particles settle on its surface. The resulting pressure difference on both sides of the filter baffle is significantly higher than in filters. This makes it possible to use a filter centrifuge to separate suspensions with non-deformable particles that form little compressible sediments.

The main disadvantages of the method are the low efficiency of retaining the dry matter of the sediment, i.e. a centrate with a high content of suspended solids is formed and must be sent for further processing. The efficiency of retaining the solid phase of the sludge and the moisture content of the cake depend on the characteristics of the dewatered sludge.

Membrane processes are widely used for wastewater treatment, for water treatment, for the purification of aqueous solutions, and the scope of their application is constantly expanding.

There are many membrane processes based on different separation principles or mechanisms that can be used to separate objects of different sizes, from particles to molecules.

It is currently a transitional process between the development of first generation membrane processes such as microfiltration, ultrafiltration, reverse osmosis, electrodialysis and dialysis, and second generation membrane processes such as gas separation, pervaporation, membrane distillation and separation using liquid membranes.

What all these processes have in common is that the separation in them is carried out by means of membranes.

The membrane can be considered as a selectively permeable barrier between two homogeneous phases, and the term "selective" can refer to both membranes and membrane processes. The most specific is the following definition: a membrane is a phase or group of phases that separate two different phases that are physically and / or chemically different from the phases of the membrane; in this case, the membrane has properties that allow it, under the action of the applied force field, to control the processes of mass transfer between the separated phases.

The process of separating mixtures using selectively permeable membranes is characterized by the presence of 3 streams:

- initial stream;

- the flow that has passed through the filtrate membrane;

- the flow that did not pass through the concentrate membrane.

The membrane separation process can be driven by gradients of pressure, concentration, or electrical potential.

Membrane processes occurring under the influence of pressure are called baromembrane processes.

Reverse osmosis is the process of filtration of solutions under pressure exceeding osmotic pressure through membranes that allow the solvent to pass and retain molecules and ions of dissolved substances. Reverse osmosis is characterized by high retention capacity (selectivity) for all salts, including monovalent ions.

This method is based on the phenomenon of osmosis - a spontaneous transition of a solvent through a semi-permeable partition into a solution. The pressure at which equilibrium occurs is called osmotic. If a pressure exceeding the osmotic pressure is applied from the side of the solution, then the transfer of the solvent will be carried out in the opposite direction, this is reflected in the name of the process "reverse osmosis". The reverse osmosis method is a method of desalination and demineralization of water and is widely used in energy, medical, food, chemical industries, as well as to improve the quality of industrial and drinking water:

- the degree of water purification from mineral salts and salts of heavy metals reaches 95-99.7%;

- relatively small dimensions of the installation, which does not require large production areas;

- simplicity of hardware design;

Thus, in terms of the achieved purification depth, reverse osmosis takes one of the first places and is the most promising method for creating water circulation cycles.

The main disadvantage of membrane desalination is the need for thorough preliminary wastewater treatment. Mechanical and adsorption filters, microfiltration, ultrafiltration are used for pre-cleaning.

Requirements for the source water supplied to reverse osmosis plants relate to a number of water quality indicators, such as the color of water, the content of oil products, surfactants, colloidal and suspended substances, and organic compounds. Therefore, much attention should be paid to the processes of preliminary preparation of the source water before supplying water to the reverse osmosis unit.

The electrochemical methods of wastewater treatment include: electrocoagulation, electrolysis, and to some extent also galvanic coagulation.

Electrochemical methods are a variety of reagent methods in which reagents are produced by the use of electricity.

At the same time, very often a reagent is used to increase the electrical conductivity of water - table salt. Table salt is also used to obtain reagents by electrolysis - oxidizing agents (sodium hypochlorite, etc.), which are used to neutralize wastewater with a high content of organic substances.

Electrochemical methods of wastewater treatment are based on the use of electrical energy during the process of electrolysis of aqueous solutions of electrolytes. The process involves: electrolyte solution - a conductor of the second kind; electrodes - conductors of the first kind, immersed in a solution; external current source by drain lines.

During electrolysis, redox processes take place; oxidation at the anode, reduction at the cathode. Redox processes can be accompanied by the formation of solid or gaseous substances. In this case, the material of the electrodes may dissolve and not dissolve. During electrolysis, the pH of the medium, the Eh of the system, changes in the volume of the solution. In this case, water impurities undergo various phase-dispersed transformations.

A number of transformations occur in the volume of the electrolyte under the influence of an electric field, such as coagulation and flocculation of colloidal particles, a change in the valence of ions during redox reactions involving water impurities; formation of solid, gaseous and liquid phases, destruction of complex organic contaminants, sorption, etc.

Electrochemical wastewater treatment methods, with the exception of the galvanocoagulation method, are quite energy-intensive and their use in each specific case must be justified by technical and economic calculations (efficiency), or by the absence of other more effective treatment methods for this type of wastewater.

Regeneration solutions of ion-exchange plants - aqueous solutions of chemical reagents used to restore the exchange properties of ion-exchange materials (cation and anion exchangers) used in water softening and desalination plants. The salt content of the regeneration solutions of ion-exchange plants reaches 5-20 g / l, which is several times higher than the salt content of the source water. Regeneration solutions of ion-exchange plants for this indicator are classified as waste water. According to water protection standards, regeneration solutions of ion-exchange plants cannot be directed either into water bodies or into the city sewage system without preliminary treatment and purification or dilution, because they pollute water bodies with mineral salts.

A separate issue is the technology of desalting and salt separation. The choice of the method of desalting and the separation of salts in the form of secondary products is determined by the quality of the source and the requirements for the quality of the treated water, the productivity of the installation and technical and economic considerations. Evaluation of economic indicators meets certain difficulties, since they depend on many factors of a natural, technical and economic nature. To eliminate the harmful effect of saline wastewater on natural reservoirs, a number of measures are applied in practice, including the construction of storage ponds and evaporation ponds, regulated discharge into watercourses, maximum use for the production needs of enterprises, as well as in agriculture. However, the methods used are not effective enough.

A radical solution to the problem of neutralizing saline waters, especially with a salt content of more than 2-3 g / l, is the construction of demineralization plants with a comprehensive processing of the resulting brines into commercial salt products. There are general recommendations for the use of one or another method of desalination, given below.

Baromembrane methods: reverse osmosis.

Recently, baromembrane processes are promising and increasingly widespread for wastewater desalination in order to return them to the production cycle.

Ideally, the filtrate and concentrate after the reverse osmosis unit are returned to the technological cycle.

The advantages of reverse osmosis over other desalination methods include:

- no need to use a large amount of reagents (for pH adjustment, inhibition of scale deposits and periodic flushing of membranes);

- no need to consume heating steam, heating source water;

- simplicity of hardware design and standardization of components, due to which the systems are easily repaired, reconstructed and increased;

compactness of the reverse osmosis system, which reduces the occupied space and increases ergonomics;

- the ability to easily automate the process;

- versatility for demineralization of waters difficult from the point of view of salt composition.

The disadvantage of using reverse osmosis is the previously mentioned need for careful pre-preparation - the following requirements are imposed on the quality of feed water for reverse osmosis plants: the content of active chlorine must be less than 0.1 mg / l; turbidity no more than 1 NTU; SDI index less than 5; COD less than 15 mg O2 / l; oxidizability less than 2 mg O2 / l; BOD less than 5 mg O2 / l, low bacterial contamination.

It can be concluded that in terms of the achieved purification depth, reverse osmosis takes one of the first places and is the most promising for creating water circulation cycles.

Evaporation method.

In the implementation and improvement of the distillation method (evaporation), the main efforts are aimed at increasing the efficiency of various types of evaporators and reducing heat costs through the use of secondary heat and cheap thermal energy generated by nuclear power plants. Analysis of current trends in seawater desalination technology shows that multistage vertical tube evaporators are more reliable than others and are more preferable in terms of preventing scale formation.

Distillation methods based on the use of film evaporators in the upward and downward flow, as well as horizontal-tubular film evaporators, are being intensively developed. Steam compression, use of secondary steam heat is used in conditions of limited thermal energy resources for medium and small installations.

Methods of desalting wastewater of various composition by evaporation of contaminated wastewater with subsequent condensation of secondary water vapor are widely presented. After evaporation, concentrated waste in the form of saturated brines or solid products (salt crystals) is sent for utilization or disposal, and the vapor condensate is sent for reuse to production.

Evaporators of various types are used for evaporation of solutions, including reactor-type evaporators, circulating, film, with heating steam recompression, flash boiling evaporators, etc. A high heat exchange rate is achieved in film-type evaporators, in which the evaporation process is carried out in a thin layer liquids. Such devices include vacuum-evaporated film-tube evaporators of vertical or horizontal design (VPU), direct-flow rotary-film evaporators (RPI), flash boiling evaporators.

Evaporation usually takes place in two stages:

1st stage. Evaporative multistage block of vertical-tube film evaporators. The stages are assembled into a small-sized monoblock with a built-in condenser for condensing the formed secondary steam, pumping equipment, instrumentation. At the first stage, in the evaporation block, the solution is evaporated to a state close to a saturated solution with a salinity of 22-26%. This type of evaporator with pipes of a special profile provides the highest heat transfer coefficient and is less prone to salt deposits. The process takes place under vacuum.

2nd stage. Vacuum - crystallizer with a remote heating chamber - the salt concentrate of the 1st stage is concentrated to a supersaturated state (40-45%) with the formation of salt crystals and the withdrawal of the salt suspension to further stages of thickening and obtaining solid salt crystals.

Recently, a new energy-saving type of evaporators has become widespread - with a heat pump, as well as with mechanical recompression of secondary water vapor (MRP). In conventional evaporators, the secondary steam generated during the evaporation of the solution is condensed and cooled in heat exchangers with circulating water, and the secondary steam condensate is used for production needs. In MRP - evaporators, the secondary vapor is compressed by a mechanical compressor, while the mechanical energy is converted into heat. During condensation, the compressed steam gives off heat to the evaporated solution, and the resulting condensate heats the original solution entering the evaporator.

An evaporator with an MRP of a film type cannot concentrate the saline solution above the onset of salt crystallization (about 20-29%, which is determined by the composition of the saline solution) and does not allow the production of crystalline salt products, therefore, to obtain salts in a dry form at the second stage, a preconcentration unit is required. which has recently also been developed and used devices with water vapor recompression (MRP), carried out by a heating chamber, a circulation circuit.

The main advantages of using evaporators for wastewater desalination are noted:

- allows you to return to production up to 90% of purified water;

- provides water purification to a salinity of 20-80 mg / l;

- allows you to get waste in the form of solid salts;

- does not require additional reagents for the processes, additional volumes of contaminated wastewater are not formed;

- carrying out demineralization of water with different salinity;

- simplicity of the organization of control;

- Requires small production areas and heights to accommodate equipment.

Main disadvantages:

- the need for additional costs of heating steam, electricity and the organization of the equipment cooling cycle; for energy-saving evaporators and crystallizers with MRS - there is no need for heating steam and cooling water.

Each of the considered methods has its own advantages and disadvantages, and often when using combined methods, a greater positive effect is achieved compared to using each method separately.

A separate issue is the processing of spent regeneration solutions of ion-exchange plants.

The technology of treatment of regeneration solutions of ion-exchange plants is determined by the content of components in wastewater, depending on the type of ion-exchange filters, the possibility of using certain reagents for processing and the completeness of utilization of the resulting by-products. The simplest technology for the treatment of such waters consists in the separation of the most mineralized part of them during the regeneration of ion-exchange filters, followed by its lime-soda softening. The solution after the treatment of sodium-cationic filters contains predominantly sodium chloride and can be used for subsequent regeneration of the filters. In some cases, sodium hydroxide can be used instead of lime to precipitate magnesium.

When using caustic soda, the operation of installations for desalting and softening water is simplified, the total amount of sludge formed is reduced, but the properties of the sludge and economic indicators are somewhat deteriorated.

Regardless of the type of installations in which the reagent softening of the spent regeneration solution occurs, the sludge compaction is provided, which depends on the chemical composition and the initial concentration of the solid phase.

In order to reduce the discharge of excess spent regeneration solution, it can be concentrated by evaporation or electrodialysis. The concentration unit is installed both before and after the reagent softening.

The disadvantage of this method is its high cost due to the increased energy consumption due to the need to evaporate the regeneration solution and capital costs for the construction and operation of complex equipment.

To exclude the use of scarce soda, the production of which is not environmentally friendly, a technology can be used that provides for the concentration of the spent regeneration solution on Na-cation exchange filters with salt separation. At the same time, crystalline table salt is obtained, returned for filter regeneration, and a commercial 35-40% solution of calcium and magnesium chlorides, which can be used in the low-temperature production of certain types of cement.

The technology for processing the spent regeneration solution, which does not require the use of soda ash, is based on the use of sodium sulfate for the regeneration of Na - cation exchange filters. In this case, the spent regeneration solution will contain sodium, magnesium, calcium sulfates. Oversaturation of the solution causes the release of calcium sulfate, and additional lime treatment leads to the formation of magnesium hydroxide. After additional strengthening with technical sodium sulfate, the treated solution is sent to filter regeneration.

In order to reduce the load on the ion-exchange filters and thereby reduce the amount of formed mineralized regeneration solutions, technologies with preliminary water purification by non-ion-exchange methods can be used. These methods include membrane technologies (electrodialysis and reverse osmosis), which allow, simultaneously with partial softening, to reduce the salinity of the treated water.

The consequence of the processing of spent regeneration solutions of ion-exchange plants can be not only a decrease in the negative impact on the natural environment in general and water bodies in particular, but also the production of various by-products that will reduce the consumption of reagents for subsequent regenerations, obtain raw materials for building materials, and reagents used in agriculture.

Based on the above presented, we can conclude that there are a large number of different methods of purification of highly mineralized wastewater, incl. formed after the processes of regeneration of ion-exchange desalting installations.

However, not one of the above methods alone does not allow to completely purify this waste water, returning the purified water to the production cycle and receiving the extracted cations and anions as a product.

Only the use of an integrated purification technology, including all modern technologies for the separation of solutions and the extraction of certain salts at different stages of the process, will make it possible to solve this problem, which is urgent for industry and ecology.

Known technical solutions for wastewater treatment under patents for inventions RU 2235069 and RU 2426699, selected as prototypes.

According to the invention RU 2235069, an automatic oily wastewater treatment complex containing a series-connected equalizer, a water supply control unit and a combined settling tank, a reagent dispenser, connected by two outputs to two reagent treatment chambers of a combined settling tank, and the third output to the first decanter input, connected in series through automatic valve decanter and centrifuge, sorption filter, wash water tank, compressor, pumps, proportional control valve, automatic valves, pneumatic air valves and automatic control unit, while the second outlet of the homogenizer is connected through two automatic valves to the second input of the decanter, flow control unit water contains a pump and a proportional control valve connected in parallel, which are connected in series with a flow sensor, a combined sump contains four sedimentation chambers connected through an automatic attic valves with the third inlet of the decanter, the reagent treatment chambers are placed in series, the outlet of the wash water tank through the pump and the automatic valve is connected to the first inlet of the sorption filter, the compressor outlet through the pneumatic air valve is connected to the second inlet of the sorption filter, the outlet of the sorption filter through the automatic valve is connected to the input of the averager, the outputs of the automatic control unit are connected to the inputs of the compressor, the reagent dispenser, the valve for proportional control of the purified water flow rate, the air pneumatic valve and automatic valves, and the output of the level sensor is connected to the input of the automatic control unit, characterized in that two parallel branches of preliminary water purification, each consisting of a series-connected buffer tank equipped with a level sensor, a pump, an automatic gate valve and a double-layer filter equipped with a temperature sensor, in the passages of each buffer tank are connected through automatic valves with the outlet of the combined clarifier, and the outputs of each filter with a two-layer loading through automatic valves with the third inlet of the sorption filter, as well as a series-connected heat exchanger, a third buffer tank, a pump, a reverse osmosis unit and a conductivity control unit, a block inhibitor, a hydrogen index control unit, a level sensor located in the homogenizer, automatic valves, air pneumatic valves and pump performance control units, while the outlet of the flushing water tank through the pump and the corresponding automatic valves is connected to the second inputs of filters with a double-layer load, and the second outputs filters with two-layer loading are connected through automatic valves to the inlets of the flushing water tank, the second and third compressor outlets are connected through the corresponding air pneumatic valves to the third inlets of filters with a two-layer loading, the third outputs of both filters with double-layer loading are connected through automatic valves with an equalizer, the second outlet of the sorption filter is connected through the corresponding automatic valves to the inlet of the heat exchanger and to the second inlet of the third buffer tank, the outlet of the inhibitor unit is connected to the second inlet of the reverse osmosis unit, the input of the control unit hydrogen exponent is connected to the second outlet of the reverse osmosis device, the second outlet of the flushing water tank through the pump is connected to the second input of the conductivity control unit, and the control inputs of all pumps are connected to the outputs of the automatic control unit through the pump performance control units.

In the preferred embodiment, an automatic oily wastewater treatment complex, characterized in that:

- the combined settling tank is equipped with a third reagent treatment chamber, which is connected to the fourth outlet of the reagent dispenser, and a device for collecting surfaced oil products, connected to the fourth inlet of the decanter;

- the inhibitor unit is equipped with a series-connected inhibitor storage and a pump with a pump performance control unit, a conductivity control unit is equipped with a mixing tank with a conductivity sensor, a hydrogen index control unit is equipped with a series-connected alkali storage unit, a pump with a pump performance control unit and a mixing tank with a sensor located in it pH value;

- the outputs of the temperature sensors, the conductivity sensor and the hydrogen index sensor are connected to the inputs of the automatic control unit, and the inputs of the pump capacity control units are connected to the outputs of the automatic control unit;

- in the water supply control unit, the pump and the control valve are connected through the automatic control unit with a level sensor.

The disadvantages of the method (and device) include the following.

- this automatic complex is intended for physical and chemical cleaning of oily wastewater and is not very applicable for the purification of saline effluents from chemical workshops of thermal power plants and other contaminated waters;

- economically ineffective for desalting wastewater with high hardness and salt content, due to the need to ensure high pressure at the stage of reverse osmosis separation and, as a result, a low degree of concentration;

- the device allows you to receive waste only in liquid form, which requires high costs for their disposal;

- the complex lacks a block for reagent softening of wastewater before membrane desalination, which would increase the efficiency of reverse osmosis separation and the degree of concentration;

- the device does not contain crystallization and centrifugation units for obtaining dry salts, including in the form of a commercial product.

The invention of the Russian Federation 2426699 relates to methods of purification of circulating waters of metallurgical production with an increased content of phosphates, heavy metals and their salts and can be used in metallurgical production. The method consists in the fact that the reagent precipitation is additionally carried out with milk of lime and a flocculant at pH 10.5-11.5, then the precipitate is compacted after settling in a sediment compactor and the precipitate is dried on a filter press, water is purified from suspended solids on a filter with granular loading, then water softening is carried out on an ion-exchange filter filled with a weakly acidic cation-exchange resin in the Na-form, then water is purified on a fine filter, then desalting is carried out on a 2-stage reverse osmosis unit at pH 7-7.5, the working pressure of water is the first stage of the reverse osmosis unit is 20 kgf / cm ² , and at the second stage - 55 kgf / cm ² , the filtrate of the first stage is used as purified water, the filtrate of the second stage is returned to the first stage in terms of concentrate for repeated purification.

The disadvantages of the scheme include the following

- to remove hardness salts and other impurities, reagent treatment with milk of lime and flocculant is used, a deeper degree of softening can be achieved using the lime-soda method, which makes it possible to abandon the use of cation-exchange filters;

- due to the higher residual hardness, there is a need for additional cation-exchange filters. Cation-exchange filters with a weakly acidic resin in this technology require double regeneration, first with acid and then with alkali to convert to a working sodium form. Double regeneration will require increased consumption of reagents and water for own needs.

- according to the technology, additional eluates appear, the purification block of which is absent;

- the technology does not provide for evaporation, crystallization and centrifugation units for obtaining dry salts, including in the form of a commercial product.

However, none of the above methods does not allow to completely purify the wastewater of the chemical workshops of the CHPP, returning the purified water to the production cycle and receiving dry salts during waste processing as target marketable products.

Only the use of an integrated purification technology, including all modern technologies for separating solutions and extracting certain salts at different stages of the process, will allow us to solve this problem, which is urgent for our industry and ecology.

The proposed technical solution sets as its task the purification of wastewater from the chemical workshops of CHPPs with the receipt of purified water returned to the technological cycle, and the release of sulfate and sodium chloride salts in the form of commercial products or waste of hazard class 4 for disposal.

On the basis of the calculated volumes and compositions of wastewater, quantitative chemical analyzes of real samples from individual stages of water treatment plants, and the development of technological parameters of wastewater treatment, a device-installation for wastewater treatment of chemical workshops of CHPPs has been developed.

The installation consists of a wash water homogenizer, an eluate accumulator, a sulfuric acid accumulator, an alkaline agent accumulator, two granular filters, two reverse osmosis units, two flow mixers, a reactor for reagent softening, a clarifier, a filter press for dewatering, two evaporators-crystallizers and two centrifuges. In this case, the rinse water equalizer is connected to the first granular filter, which in turn is connected to the first reverse osmosis unit, which is further connected to the first flow mixer; an eluate accumulator and an alkaline agent (milk of lime and soda) accumulator are connected to the first flow mixer, which in turn is connected to the reactor for reagent softening, where a mixed stream of eluates, alkaline agents and concentrate of the first reverse osmosis unit is fed; the reactor, in turn, is associated with a clarifier, which is associated with a filter press and a second granular filter; the filter press, the second granular filter and the sulfuric acid accumulator are connected to the second flow mixer, which in turn is connected to the second reverse osmosis unit, which in turn is connected to the first evaporator-crystallizer operating on the principle of crystallization by cooling, which is connected to the first centrifuge , which is connected to the second evaporator-crystallizer, working on the principle of vacuum evaporation, which is connected to the second centrifuge.

Evaporators-crystallizers are structurally made with external heating chambers, which, along with the use of a new generation of sediment inhibitors, provides high circulation rates of concentrated effluent and does not lead to the formation of scale on the heat transfer surfaces of the evaporators.

These evaporators-crystallizers are installations where low pressure steam (no more than 1.2 atm) is used. Here, optimal evaporation technologies are used to obtain individual crystalline products - sodium sulfate, sodium chloride, and the centrifuge leaves the centrifuge in an amount of 35-40 kg / hour, containing concentrated humic compounds of the fourth hazard class. This solution can be added to the "soil" to improve its quality.

The device works as follows. See figure 1. Wash water from the homogenizer 1 through the first granular filter 2 is directed to the first stage of reverse osmotic desalination 3, where it is divided into two streams: filtrate and concentrate.

The filtrate is sent for further use in the technological cycle of the chemical department of the CHPP.

The concentrate is mixed in the first mixer 4 with the stream from the eluate accumulator 5 and the alkaline agent accumulator 6. The mixed stream is directed to the reagent treatment unit 7 and then to the clarifier 8.

At the stage of reagent softening, which is carried out in the reactor 7, the precipitation process begins, and then in the clarifier 8, salts of calcium sulfate, calcium carbonate, magnesium hydroxide "sit down" from the combined stream, and the thickened suspension of these salts is fed to the filter press 9 for dehydration.

And the clarified water from the clarifier 8 is fed to the second granular filter 10 and then from it to the second mixer of the stream 11, where the filtrate from the filter press 9 also enters.

The sediment of the fourth hazard class from the filter press 9, the so-called "soil", is sent to storage, then to the consumer, and the filtrate, a highly mineralized solution that does not contain hardness ions, is mixed in the second mixer 11 with clarified softened water that has passed the clarifier 8 and then the second granular filter 10, acidified there with sulfuric acid from the sulfuric acid storage 12 to pH 6.5-7.0, and enters the second stage of high-pressure reverse osmosis desalination 13. The reverse osmosis filtrate is supplied for further use in the technological cycle of the CHP chemical workshop, and the concentrate is fed to further processing in the first evaporator-crystallizer 14, operating according to the method of crystallization by cooling. After that, the concentrated suspension goes to the first centrifuge 15 in order to isolate the target products - decahydrate sodium sulfate Na ₂ SO ₄ * 10H ₂ O. The centrifuge from the first centrifuge 15 goes to the second evaporator-crystallizer 16 operating by the vacuum evaporation method. The centrifuge from it goes to the second centrifuge 17 for teaching sodium chloride NaCl.

The centrifuge obtained after the second centrifuge is enriched with organic impurities, which enter the eluates after the regeneration of OH-filters of the CHP chemical department and represent a mixture of humic and fulvic compounds contained in river water (COD value 150 mg O / L in the initial solution and 4000- 9500 mg O / L in centrifuge after the second centrifuge).

The advantages of this device.

Separation of effluents from the CHP plant's chemical department into wash water and highly concentrated eluates allows reducing energy and operating costs, returning more than 50% of the treated water to the production cycle of the CHP plant's chemical plant with minimal costs.

The use of the stage of reverse osmosis desalting as a preliminary one allows to obtain a good quality filtrate sent directly to the VPU, and reduces the amount of reagents and energy consumption for further purification. At the first stage, low-pressure elements and modern sediment inhibitors are used to concentrate salts without significant deposits on the membrane surface and without increasing the frequency of chemical washes.

The use of a technological bundle: a reverse osmosis installation - a block of evaporators-crystallizers makes the scheme economically feasible and more reliable from the point of view of operation.

The obtained salts are sold as a commercial product.

The availability of a full range of technologies allows for the purification of wastewater from chemical workshops of CHP plants with the receipt of purified water returned to the technological cycle and the release of sulfate and sodium chloride salts in the form of commercial products or waste of hazard class 4 for disposal.

Claims (6)

1. Wastewater treatment plant, consisting of a flushing water homogenizer, an eluate accumulator, a sulfuric acid accumulator, an alkaline agent accumulator, two granular filters, two reverse osmosis units, two flow mixers, a reactor for reagent softening, a clarifier, a filter press for dehydration, two evaporators-crystallizers and two centrifuges, characterized in that the wash water equalizer is connected to the first granular filter, which in turn is connected to the first reverse osmosis unit, which is further connected to the first flow mixer; an eluate accumulator and an alkaline agent accumulator are connected to the first flow mixer, which in turn is connected to the reactor for carrying out reagent softening; the reactor, in turn, is associated with a clarifier, which is associated with a filter press and a second granular filter; the filter press, the second granular filter and the sulfuric acid accumulator are connected to the second flow mixer, which in turn is connected to the second reverse osmosis unit, which in turn is connected to the first evaporator-crystallizer, which is connected to the first centrifuge, which is connected to the second an evaporator-crystallizer, which is connected to the second centrifuge. 2. Installation of wastewater treatment according to claim 1, characterized in that the storage of lime milk and soda is used as the storage for the alkaline agent. 3. Wastewater treatment plant according to claim 1, characterized in that the first evaporator-crystallizer operates on the principle of crystallization by cooling. 4. Wastewater treatment plant according to claim 1, characterized in that the second evaporator-crystallizer operates on the principle of vacuum evaporation. 5. Wastewater treatment plant according to claim 1, characterized in that both evaporators-crystallizers are structurally made with external heating chambers. 6. Wastewater treatment plant according to claim 1, characterized in that both evaporators-crystallizers are low-pressure steam installations - no more than 1.2 atm.

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