Modern water treatment and water purification systems. Water treatment project, water treatment technology

Surface and underground waters, depending on geological and hydrogeological conditions, contain various chemical substances, the concentrations of which may exceed the requirements for water quality when used in public utilities, production in various industries and agriculture. To fulfill these requirements, there are such areas of activity as water treatment and water purification.

Modern methods of water purification make it possible to prepare water of the required quality for any production, as well as for use for domestic purposes.

Water treatment systems, depending on the water treatment method used (method of water purification), can be divided into two functional groups: reagent-free, which do not use chemical reagents in the water purification process, and reagent-based, which are implemented using chemical reagents.

The reagent-free method of water purification is used for deferrization, demanganization, desiliconization and extraction of various microorganisms, provided that the quality of the treated water meets certain requirements. Reagent-free modern methods of water treatment can be carried out on DEFERRIT installations in the processes of biological purification of groundwater and on reverse osmosis membrane installations UMO. This method eliminates the entry of harmful chemicals into the water and at the same time perfectly disinfects the water.

A modern method of water purification includes installations for reagent-free disinfection by irradiating water with ultraviolet rays or ozone, which can be used at various stages of water treatment.

Modern water purification and water disinfection systems involve the use of various types coagulants and flocculants, alkali or acid solutions, sodium hypochlorite or other specific disinfectants.

Modern methods of water treatment, based on the use of reagents, are successfully carried out on the installations "STRUYA", "MOISTURE", "DEFERRITE".

The choice of a modern water treatment system depends on the type of water source (surface or underground), the physical, chemical and microbiological composition of the source water, as well as the drainage conditions and the environmental situation at the site.

The EKOHOLDING Group of Companies is ready to offer a number of modern water treatment methods that allow us to achieve high quality drinking water from almost any water source. "ECHOLDING" is one of the leading companies in the market for the development of modern methods of water purification, as well as modern methods of water treatment, which make it possible to achieve high quality purified water that meets the requirements. Many years of experience and the use of modern water purification methods make it possible to provide water of the required quality not only to rural and urban facilities, but also to large industrial enterprises. Modern water treatment methods are used in installations developed by our specialists and allow us to achieve the best results at a reasonable price.

In modern conditions big city, with polluted air and a rather poor environment, every person strives to maintain health. Water is the main product for each of us. Lately everything more people think about what kind of water they use. In this regard, water hardness and water purification are not empty terms, but important parameters. Today, specialists successfully use water treatment and water purification technologies, which helps obtain much cleaner water suitable for consumption. Professionals also pay attention to water softening, carrying out a number of measures to improve its properties.

What do water treatment technologies provide?

Let's take a closer look at what water treatment technologies are. This is primarily the purification of water from plankton. This microorganism, which lives in rivers, began to develop most intensively after large reservoirs appeared. Note that when plankton develops in large quantities, the water begins to smell unpleasant, change color and acquire a characteristic taste.

Today, many industrial companies are pouring their untreated waste into rivers. wastewater with a huge content of organic contaminants and chemical impurities. From these open reservoirs they subsequently extract drinking water. As a result, most of them, mainly those located in or near megacities, are very polluted. The water contains phenols, organochlorine pesticides, ammonium and nitrite nitrogen, petroleum products and other harmful substances. Of course, water from such sources is unsuitable for consumption without prior preparation.

We should not forget about new production technologies, various emergencies and accidents. All these factors can also worsen the condition of water in sources and negatively affect its quality. Thanks to modern methods Research scientists managed to find petroleum products, amines, phenols, and manganese in water.

Water treatment technologies, if we're talking about about the city, including the construction of water treatment plants. By passing through several stages of purification, water becomes more suitable for drinking. But nevertheless, even with the use of water treatment facilities, it is not completely freed from harmful impurities, and therefore it enters our homes still quite contaminated.

Today, there are various technologies for water treatment and purification of drinking and waste water. As part of these measures, mechanical purification is used to remove various impurities using installed filters, remove residual chlorine and chlorine-containing elements, purify water from a large amount of mineral salts contained in it, and also soften and remove salts and iron.

Basic water treatment and water purification technologies

Technology 1. Lightening

Clarification is the stage of water purification at which its turbidity is eliminated, reducing the amount of mechanical impurities in natural and waste waters. The level of turbidity in water, especially in surface sources during floods, sometimes reaches 2000-2500 mg/l, while the norm for water suitable for drinking and household use is no more than 1500 mg/l.

Water is clarified by precipitating suspended substances using special clarifiers, settling tanks and filters, which are the most well-known water treatment facilities. One of the most well-known methods widely used in practice is coagulation, that is, reducing the amount of fine impurities in water. As part of this water treatment technology, coagulants are used - complexes for sedimentation and filtration of suspended substances. Next, the clarified liquid enters clean water tanks.

Technology 2. Discoloration

Coagulation, the use of various oxidizing agents (for example, chlorine along with its derivatives, ozone, manganese) and sorbents (active carbon, artificial resins) make it possible to decolorize water, that is, eliminate or discolor colored colloids or completely dissolved substances in it.

Thanks to this water treatment technology, water contamination can be significantly reduced by eliminating most bacteria. Moreover, even after removing some harmful substances Others often remain in the water, for example, bacilli of tuberculosis, typhoid fever, dysentery, Vibrio cholera, encephalitis and polio viruses that cause infectious diseases. In order to completely destroy them, water used for domestic and economic needs must be disinfected.

Coagulation, sedimentation and filtration have their disadvantages. These water treatment technologies are insufficiently efficient and expensive, and therefore it is necessary to use other methods of purification and improvement of water quality.

Technology 3. Desalting

With this water treatment technology, all anions and cations that affect the salt content in general and the level of its electrical conductivity are removed from the water. When desalting, reverse osmosis, ion exchange and electrodeionization are used. Depending on the level of salt content and what requirements exist for demineralized water, the appropriate method is chosen.

Technology 4. Disinfection

The final stage of water purification is disinfection, or disinfection. The main task of this water treatment technology is to suppress the activity of harmful bacteria in the water. To completely purify water from microbes, filtration and sedimentation are not used. To disinfect it, it is chlorinated, and other water treatment technologies are also used, which we will discuss later.

Today, experts use many methods of water disinfection. Water treatment technologies can be divided into five main groups. The first method is thermal. The second is sorption on active carbon. The third is chemical, in which strong oxidizing agents are used. The fourth is oligodynamy, in which ions act on noble metals. The fifth is physical. This water treatment technology uses radioactive radiation, ultraviolet rays and ultrasound.

As a rule, when disinfecting water, chemical methods are used using ozone, chlorine, chlorine dioxide, potassium permanganate, hydrogen peroxide, sodium hypochlorite and calcium as oxidizing agents. As for a specific oxidizing agent, in this case chlorine, sodium hypochloride, and bleach are most often used. The disinfection method is chosen based on the consumption and quality of the water being treated, the effectiveness of its initial purification, the conditions for transportation and storage of reagents, the ability to automate processes and mechanize complex work.

Specialists disinfect water that has been pre-treated, coagulated, clarified and discolored in a layer of suspended sediment, or settled, filtered, since the filter does not contain particles on or inside of which adsorbed microbes that have not been disinfected can be located.

Technology 5.Disinfection using strong oxidizing agents

IN this moment in the housing and communal services sector, water is usually chlorinated in order to purify and disinfect it. When drinking tap water, be aware of the chlorine content. organic compounds, the level of which after disinfection using chlorine is up to 300 μg/l. At the same time, the initial threshold of contamination does not affect this indicator, since it is chlorination that causes the formation of these 300 microelements. It is highly undesirable to consume water with such indicators. Chlorine, combining with organic substances, forms trihalomethanes - methane derivatives, which have a pronounced carcinogenic effect, as a result of which cancer cells appear.

When chlorinated water is boiled, it produces a highly toxic substance called dioxin. You can reduce the level of trihalomenates in water by reducing the amount of chlorine used during disinfection and replacing it with other disinfection substances. In some cases, granular activated carbon is used to remove organic compounds formed during disinfection. Of course, we should not forget about complete and regular monitoring of drinking water quality indicators.

If natural waters are very cloudy and have a high color, they often resort to preliminary chlorination. But, as mentioned earlier, this water treatment technology does not have sufficient efficiency, and it is also very harmful to our health.

The disadvantages of chlorination as a water treatment technology, therefore, include low efficiency plus enormous damage to the body. When the carcinogen trihalomethane is formed, cancer cells appear. Regarding the formation of dioxin, this element, as noted above, is a powerful poison.

Without the use of chlorine, water disinfection is not feasible from an economic point of view. Various alternative water treatment technologies (for example, disinfection using UV radiation) are quite expensive. The best option today is water disinfection using ozone.

Technology 6.Ozonation

Disinfection using ozone seems safer than chlorination. But this water treatment technology also has its disadvantages. Ozone does not have increased resistance and is prone to rapid destruction, and therefore has a bactericidal effect for a very short time. This requires water to pass through the plumbing system before entering our homes. This is where difficulties arise, since we all have an idea of ​​the approximate degree of deterioration of water pipelines.

Another nuance of this water treatment technology is that ozone reacts with many substances, including, for example, phenol. The elements formed during their interaction are even more toxic. Disinfecting water using ozone is a dangerous undertaking if the water contains a tiny percentage of bromine ions (it is difficult to detect even in the laboratory). When ozonation is performed, toxic bromine compounds appear - bromides, which pose a danger to humans even in microdoses.

In this case, ozonation is the best option for disinfecting large volumes of water, requiring thorough disinfection. But do not forget that ozone, like the substances that appear during its reactions with organochlorines, is a toxic element. In this regard, a high concentration of organochlorines at the stage of water purification can pose great harm and a health hazard.

So, the disadvantages of disinfection using ozone include even greater toxicity when interacting with phenol, which is even more dangerous than chlorination, as well as a short bactericidal effect.

Technology 7.Disinfection using bactericidal rays

To disinfect groundwater, bactericidal rays are often used. They can be used only if the coli index of the initial state of the water is not higher than 1000 units/l, the iron content is up to 0.3 mg/l, and the turbidity is up to 2 mg/l. Compared to disinfection with chlorine, the bactericidal effect on water is optimal. In the taste of water and its chemical properties When using this water treatment technology, no changes occur. The rays penetrate the water almost instantly, and after their exposure it becomes suitable for consumption. Using this method, not only vegetative but also spore-forming bacteria are destroyed. In addition, using installations for water disinfection in this way is much more convenient than using chlorination.

In the case of untreated, turbid, colored or waters in which the level of iron content is high, the absorption coefficient turns out to be so strong that the use of bactericidal rays becomes unjustified from an economic point of view and not sufficiently reliable from a sanitary point of view. In this regard, the bactericidal method is better used to disinfect already purified water or to disinfect groundwater that does not require purification, but requires disinfection for prevention.

The disadvantages of disinfection using bactericidal rays include the economic unjustification and unreliability of this water treatment technology from a sanitation point of view.

Technology 8.Deferrization

The main sources of iron compounds in natural water are weathering processes, soil erosion and rock dissolution. As for drinking water, iron may be present in it due to corrosion of water supply pipes, and also because municipal treatment plants used iron-containing coagulants to clarify the water.

Exists modern direction in non-chemical methods of groundwater purification. This is a biological method. This water treatment technology is based on the use of microorganisms, most often iron bacteria, which convert Fe 2 + (ferrous iron) into Fe 3 + (rust). These elements are not hazardous to human health, but their waste products are quite toxic.

The basis of modern biotechnologies is the use of the properties of a catalytic film, which is formed on a load of sand and gravel or other similar material with small pores, as well as the ability of iron bacteria to ensure the flow of complex chemical reactions without energy costs and reagents. These processes are natural, and they are based on biological natural laws. Iron bacteria actively and in large numbers develop in water, the iron content of which is from 10 to 30 mg/l, but practice shows that they can live at a lower concentration (100 times). The only condition here is to maintain a sufficiently low level of acidity of the environment and the simultaneous access of oxygen from the air, at least in a small volume.

The final stage of application of this water treatment technology is sorption purification. It is used to retain bacterial waste products and carry out final disinfection of water using bactericidal rays.

This method has quite a few advantages, the most important of which is, for example, environmental friendliness. He has every chance to further development. However, this water treatment technology also has a disadvantage - the process takes a lot of time. This means that in order to ensure large production volumes, tank structures must be large-sized.

Technology 9. Dgassing

The corrosive aggressiveness of water is influenced by certain physical and chemical factors. In particular, water becomes aggressive if it contains dissolved gases. As for the most common and corrosive elements, carbon dioxide and oxygen can be noted here. It is no secret that if water contains free carbon dioxide, oxygen corrosion the metal becomes three times more intense. In this regard, water treatment technologies always involve the removal of dissolved gases from water.

There are main ways to remove dissolved gases. Within their framework, physical desorption is used, and they also use chemical methods of binding them to remove residual gas. The use of such water treatment technologies, as a rule, requires high energy costs, large production areas, and consumption of reagents. In addition, all this can cause secondary microbiological contamination of water.

All of the above circumstances contributed to the emergence of a fundamentally new water treatment technology. This is membrane degassing, or degasification. Applying this method, specialists, using a special porous membrane into which gases can penetrate, but water cannot penetrate, remove gases dissolved in water.

The basis of membrane degassing is the use of special membranes large area(usually hollow fiber based) housed in pressure housings. Gas exchange processes occur in their micropores. Membrane water treatment technology makes it possible to use more compact installations, and the risks that water will again be subject to biological and mechanical contamination are minimized.

Thanks to membrane degassers (or MDs), it is possible to remove dissolved gases from water without dispersing it. The process itself is carried out in water, then in a membrane, then in a gas flow. Despite the presence of an ultraporous membrane in MD, the operating principle of a membrane degasser differs from other types of membranes (reverse osmosis, ultrafiltration). In the space of the degasser membranes, there is no flow of liquid through the membrane pores. The membrane is an inert gas-tight wall that serves as a separator for the liquid and gaseous phases.

Expert opinion

Features of the application of groundwater ozonation technology

V.V. Dzyubo,

L.I. Alferova,

Senior Researcher, Department of Water Supply and Sanitation, Tomsk State University of Architecture and Civil Engineering

How effective ozonation will be as a technology for water treatment and purification of groundwater is influenced not only by the parameters of ozone synthesis: costs electrical energy, price, etc. It is also important how effectively the ozone is mixed and dissolved in the water being treated. We should not forget about the quality composition.

More suitable for better dissolution of ozone cold water, and the substance disintegrates faster when the temperature of the aquatic environment increases. As saturation pressure increases, ozone also dissolves better. All this needs to be taken into account. For example, ozone dissolves up to 10 times faster in a certain temperature environment than oxygen.

Research related to water ozonation has been repeatedly conducted in Russia and abroad. The results of studies of this water treatment technology showed that the level of water saturation with ozone (the maximum possible concentration) is influenced by the following factors:

• the ratio of the volume of the supplied mixture of ozone and air (m 3) and the amount of treated water Qw (m 3) - (Qoz / Qw);
• ozone concentration in the mixture of ozone and air that is supplied to the water;
• volume of water being treated;
• temperature of the water being treated;
• saturation pressure;
• duration of saturation.

If the source of water supply is groundwater, it should be remembered that it may change depending on the season, in particular its quality becomes different. This must be taken into account when justifying water treatment technologies for organizing public water supply, especially if it uses ozonation.

If ozone is used in groundwater treatment technologies, one should not forget about significant differences in their quality in different regions Russia. In addition, the quality of groundwater differs from the composition of previously studied clean water. In this regard, the use of any known water treatment technology or technological parameters for water treatment will be incorrect, since the qualitative composition and specifics of the water to be treated should always be taken into account. For example, there will always be differences between the real or actually achieved ozone concentration in natural groundwater subject to treatment and the theoretically possible or achieved values ​​using clean water. When justifying certain water treatment technologies, a detailed study of the qualitative composition of the water source is required first of all.

Modern water treatment technologies and innovative methods

By introducing new methods and technologies of water treatment, it is possible to solve certain problems, the achievement of which ensures:

• production of drinking water in accordance with GOST and current standards that meet the requirements of customers;
• reliable water purification and disinfection;
• uninterrupted and reliable operation of water treatment facilities;
• reducing the cost of water preparation and purification processes;
• saving reagents, electrical energy and water for personal needs;
• high quality water production.

It should also be mentioned Newest technologies water treatment, which is used to improve water.

1. Membrane methods

Membrane methods are based on modern water treatment technologies, which include macro- and micro-, ultra- and nanofiltration, as well as reverse osmosis. Membrane water treatment technology is used to desalinate wastewater and solve problems associated with water treatment. At the same time, purified water cannot yet be called useful and safe for the body. Note that membrane methods are expensive and energy-intensive, and their use is associated with constant maintenance costs.

2. Reagent-free methods

Here we should first of all highlight the structuring, or activation, of the liquid as the most frequently used method. Today there are various ways activation of water (for example, the use of magnetic and electromagnetic waves, cavitation, ultrasonic frequency waves, exposure using various minerals, resonant methods). Using structuring, you can solve a number of problems in water preparation (bleach, soften, disinfect, degas, deferrize water and carry out a number of other manipulations). Chemical water treatment technologies are not used.

Activated water and liquid to which traditional water treatment technologies have been applied are different from each other. The disadvantages of traditional methods have already been mentioned earlier. The structure of activated water is similar to the structure of water from a spring, “living” water. It has many healing properties and great benefits for the human body.

To remove turbidity (thin suspensions that are difficult to settle) from a liquid, another method of activated water is used - its ability to accelerate the coagulation (adhesion and sedimentation) of particles and the subsequent formation of large flakes. Chemical processes and crystallization of dissolved substances occur much faster, absorption becomes more intense, and there is an improvement in the coagulation of impurities and their precipitation. In addition, such methods are often used to prevent the formation of scale in heat exchange equipment.

Water quality is directly affected by the activation methods and water treatment technologies used. Among them:

• magnetic water treatment devices;
• electromagnetic methods;
• cavitation;
• resonant wave structuring of liquid (this water treatment technology is non-contact, and is based on piezocrystals).

3. Hydromagnetic systems

The purpose of HMS (hydromagnetic systems) is to process water flows using constant magnetic field special spatial configuration. HMS is used to neutralize scale in heat exchange equipment, as well as to clarify water (for example, after disinfection with chlorine). Works this system So: metal ions in water interact with each other at the magnetic level. At the same time, chemical crystallization occurs.

Treatment using hydromagnetic systems does not require chemical reagents, and therefore this cleaning method is environmentally friendly. But there are also disadvantages to GMS. As part of this water treatment technology, permanent powerful magnets are used, which are based on rare earth elements that retain their parameters (magnetic field strength) for a long time (decades). But if these elements overheat above 110-120 o C, weakening is possible magnetic properties. In this regard, the installation of hydromagnetic systems should be carried out in places where the water temperature does not exceed these values, i.e. before it is heated (return line).

So, the disadvantages of HMS include the possibility of use at a temperature of no more than 110-120 o C, insufficient efficiency, and the need to use other methods with it, which is unprofitable from an economic point of view.

4. Cavitation method

During cavitation, cavities (cavities or cavitation bubbles) are formed in water, inside which there is gas, steam or a mixture of them. During cavitation, water passes into another phase, that is, it turns from liquid to vapor. Cavitation appears when the pressure in the water decreases. A change in pressure is caused by an increase in its speed (with hydrodynamic cavitation), the passage of acoustic water during the rarefaction half-period (with acoustic cavitation).

When cavitation bubbles suddenly disappear, water hammer occurs. As a result, a compression and tension wave is created in water at ultrasonic frequency. The cavitation method is used to purify water from iron, hard salts and other substances that exceed the maximum permissible concentration. At the same time, water disinfection by cavitation is not very effective. Other disadvantages of using the method include significant energy consumption and expensive maintenance with consumable filter elements (resource from 500 to 6000 m 3 of water).

Technologies for water treatment of drinking water for housing and communal services according to the scheme

Scheme 1.Aeration-degassing - filtration - disinfection

This water treatment technology can be called the simplest from a technological point of view and constructive in implementation. The scheme is implemented using different methods of aeration and degassing - it all depends on the qualitative composition of the groundwater. Here are two key uses of this water treatment technology:

• aeration-degassation of liquid in the initial state in the tank; forced air supply and subsequent filtration using granular filters and disinfection by UV irradiation are not used. During aeration-degassing, spraying is carried out onto a hard contact layer using ejector nozzles and vortex nozzles. A contact pool, a water tower, etc. can act as a reservoir of initial water. The filters here are albitophyres and burnt rocks. This technology is usually used to purify groundwater that contains mineral forms of dissolved Fe 2 + and Mn 2 + that do not contain H 2 S, CH 4 and anthropogenic pollutants;
• aeration-degassing, carried out in a similar way to the previous method, but with the additional use of forced air supply. This method is used if the groundwater contains dissolved gases.

Purified water can be supplied to special RWCs (clean water reservoirs) or towers, which are special storage tanks, provided that they have not already been used as a receiving tank. The water is then transported to consumers via distribution networks.

Scheme 2.Aeration-degassing - filtration - ozonation - filtration on GAC - disinfection

As for this water treatment technology, its use is advisable for complex purification of groundwater if there are strong contaminants in high concentrations: Fe, Mn, organic matter, ammonia. During this method, single or double ozonation is carried out:

• if there are dissolved gases CH 4, CO 2, H 2 S, organic matter and anthropogenic pollution in the water, ozonation is carried out after aeration-degassing with filtration using inert materials;
• if there is no CH 4, at (Fe 2 +/Mn 2 +)< 3: 1 озонирование нужно проводить на первом этапе аэрации-дегазации. Уровень доз озона в воде не должен быть выше 1,5 мг/л, чтобы не допустить окисления Mn 2 + до Mn 7 +.

You can use those filter materials that are indicated in diagram A. If sorption purification is used, they often use activated carbons and clinoptilolite.

Scheme 3. Aeration-degassing - filtration - deep aeration in vortex aerators with ozonation - filtration - disinfection

This technology develops the technology for purifying groundwater according to scheme B. It can be used to purify water that contains increased level Fe (up to 20 mg/l) and Mn (up to 3 mg/l), petroleum products up to 5 mg/l, phenols up to 3 μg/l and organics up to 5 mg/l with the pH of the source water close to neutral.

Within this water treatment technology, it is best to use UV irradiation to disinfect purified water. Territories for bactericidal installations can be:

• places located directly before the supply of purified water to consumers (if the length of the networks is short);
• right in front of the water points.

Taking into account the quality of groundwater from a sanitary point of view and the state of the water supply system (networks, structures on them, RHF, etc.), equipping stations or water treatment equipment for the purpose of disinfecting water before supplying it to consumers may imply the presence any equipment acceptable for the conditions of a particular territory.

Scheme 4.Intensive degassing-aeration - filtration (AB; GP) - disinfection (Ural irradiation)

This water treatment technology includes stages of intensive degassing-aeration and filtration (sometimes two-stage). The use of this method is advisable when it is necessary to remove dissolved CH 4, H 2 S and CO 2, which are present in high concentrations with a fairly low content of dissolved forms of Fe and Mn - up to 5 and 0.3 mg/l, respectively.

As part of the application of water treatment technology, enhanced aeration and filtration are performed in 1-2 stages.

To perform aeration, they use vortex nozzles (in relation to individual systems), vortex degassers - aerators, combined degassing and aeration units (columns) with simultaneous removal of gases.

As for filter materials, they are similar to those indicated in scheme A. When the groundwater contains phenols and petroleum products, filtration is carried out using sorbents - activated carbons.

In accordance with this scheme, water is filtered using two-stage filters:

• 1st stage - to purify water from Fe and Mn compounds;
• 2nd stage - to carry out sorption purification of water, which has already been purified, from petroleum products and phenols.

If possible, only the first stage of filtering is performed, due to which the circuit becomes more flexible. At the same time, the implementation of such water treatment technology requires more costs.

If we consider small and medium settlements, the use of this water treatment technology is preferable in the pressure version.

As part of the application of water treatment technology, you can use any method of disinfection of water that has already been purified. It all depends on how productive the water supply system is and what are the conditions of the territory where the water treatment technology is used.

Scheme 5.Ozonation - filtration - filtration - disinfection (NaClO)

If it is necessary to remove anthropogenic and natural contaminants, they resort to ozonation with further filtration through a granular load and adsorption on GAC and disinfection with sodium hypochlorite when the total iron content in the water is up to 12 mg/l, potassium permanganate is up to 1.4 mg/l and oxidability is up to 14 mg O 2 /l.

Scheme 6.Aeration-degassing - coagulation - filtration - ozonation - filtration - disinfection (NaClO)

This option is similar to the previous scheme, but here aeration-degassing is used and a coagulant is introduced before the deferrization and demanganization filters. Thanks to water treatment technology, it is possible to remove anthropogenic pollutants in more difficult situation, when the iron content reaches up to 20 mg/l, manganese up to 4 mg/l and high permanganate oxidation is present - 21 mg O 2 /l.

Scheme 7.Aeration-degassing - filtration - filtration - ion exchange - disinfection (NaClO)

This scheme is recommended for districts Western Siberia, where there are significant oil and gas deposits. As part of the water treatment technology, water is freed from iron, sorbtion is carried out on GAC, ion exchange is carried out on clinoptilolite in Na-form with further disinfection and sodium hypochlorite. Let us note that the scheme is already being successfully used in Western Siberia. Thanks to this water treatment technology, the water complies with all SanPiN 2.1.4.1074-01 standards.

Water treatment technology also has disadvantages: periodically, ion exchange filters must be regenerated using a solution of table salt. Accordingly, the issue of destruction or secondary use of the regeneration solution arises here.

Scheme 8. Aeration-degassation - filtration (C + KMnO 4) - ozonation - sedimentation - adsorption (C) - filtration (C + KMnO 4) (demanganation) - adsorption (C) - disinfection (Cl)

Thanks to the water treatment technology according to this scheme, heavy metals, ammonium, radionuclides, anthropogenic organic pollutants, etc., as well as manganese and iron are removed from the water in two stages - using coagulation and filtration through loading from natural zeolite (clinoptilolite), ozonation and sorption on zeolite . Regenerate the load using the reagent method.

Scheme 9. Aeration-degassation - ozonation - filtration (clarification, iron removal, demanganation) - adsorption on GAC - disinfection (Ural irradiation)

Within the framework of this water treatment technology, the following activities are carried out:

• Methane is completely removed with a concomitant increase in pH as a result of partial stripping of carbon dioxide, hydrogen sulfide, as well as volatile organochlorine compounds (VOC), preozonation, oxidation of preozonation and hydrolysis of iron are performed (deep aeration-degassation stage);
• 2-3-valent iron and iron phosphate complexes, partially manganese and heavy metals are removed (filtration stage of water treatment technology);
• destroy residual persistent complexes of iron, potassium permanganate, hydrogen sulfide, anthropogenic and natural organic substances, sorption of ozonation products, nitrify ammonium nitrogen (ozonation and sorption stage).

Purified water must be disinfected. To do this, UV irradiation is performed, a small dose of chlorine is introduced, and only then the liquid is supplied to the water distribution networks.

Expert opinion

How to choose the right water treatment technology

V.V. Dzyubo,

Dr. Tech. Sciences, Professor of the Department of Water Supply and Sanitation, Tomsk State University of Architecture and Civil Engineering

From an engineering point of view, it is quite difficult to design water treatment technologies and draw up technological schemes according to which it is necessary to bring water to drinking standards. The determination of the method of processing groundwater as a separate stage in the preparation of a general water treatment technology is influenced by the qualitative composition natural waters and the required cleaning depth.

Groundwater in Russian regions are different. It is on their composition that water treatment technologies and achieving water compliance with drinking standards depend on SanPiN 2.1.4.1074-01 “Drinking water. Hygienic requirements for water quality of centralized drinking water supply systems. Quality control. Sanitary and epidemiological rules and regulations.” The water treatment technologies used, their complexity and, of course, the cost of purification equipment also depend on the initial quality and content of drinking water.

As already noted, the composition of waters is different. Its formation is influenced by the geographic, climatic, and geological conditions of the area. For example, the results of natural studies of the composition of waters in different territories of Siberia indicate that they have different characteristics in different seasons, since their nutrition changes depending on the time of year.

When the conditions for the extraction of groundwater from aquifers are violated, water flows from neighboring horizons, which also affects the change in characteristics and qualitative composition of liquids.

Since the choice of one or another water treatment technology depends on the characteristics of water, it is necessary to analyze their composition in detail and completely in order to choose the least expensive and most effective option.

A standard reverse osmosis installation includes: a block of fine filters; Cartridge filters with five-micron cartridges are used; high pressure pump unit; block of membrane modules; consists of rolled membrane elements enclosed in fiberglass or stainless steel housings; acid and inhibitor dosing unit to prevent membrane contamination by salt deposits (the need for acid and inhibitor dosing and doses are determined by calculation based on the value of the Langelier index of the concentrate); flushing unit - flushing is necessary to extend the service life of the membranes, because in any case, during operation, salts are deposited on their surface (the frequency of washing depends on the quality of the source water and the correct calculation of the installation and can be no more than once every three to four months). Additionally, in industrial installations, conductometers are installed to monitor the quality of permeate, an automation cabinet with a controller, and many other devices for automation and process control.

The productivity of reverse osmosis plants for permeate is on average 60-75%. Standard installations are limited to a working pressure of 16 bar, because... This is the maximum pressure for PVC pipes. The use of stainless steel pipes increases the cost of installation. When the salinity content is above 2000-3000 mg/l, the operating pressure becomes higher than 16 bar, and to reduce it, as a rule, the concentrate discharge is increased and the permeate productivity is correspondingly reduced. The selectivity of reverse osmosis membranes is from 98 to 99.7% for NaCl, operating pressure is from 6 to 25 bar.

Both chemical desalination and reverse osmosis make it possible to obtain water with a specific electrical conductivity of 5-50 µS/cm, depending on the salt content of the source water. Deeper desalting is carried out in two stages. Each installation, be it H-cationization, chemical desalting and especially reverse osmosis, must be calculated and selected individually for a specific case.

Corrective water treatment
Traditionally, the following are used for corrective water treatment: phosphates (trisodium phosphate, hexametaphosphate, tripolyphosphate and various mixtures thereof) to prevent the appearance of calcium scale and maintain the pH level of the water, which protects steel from corrosion; sodium sulfite for chemical deoxygenation of water after a deaerator or instead of a deaerator with a low flow rate of make-up water (up to 2 m3/h); ammonia for binding carbon dioxide in feed water and steam in order to protect the feed and steam-condensate ducts from carbon dioxide corrosion.

The use of these reagents requires special reagent facilities. Phosphates are first dissolved in a special solution tank, then the solution is filtered using a clarification filter to remove contaminants. When preparing a solution of sodium sulfite, it is necessary to take measures to isolate it from air. To dissolve sulfite, a sealed tank is used, which must be purged with steam before supplying water for dissolution. Special requirements are imposed on the premises and qualifications of operating personnel when working with ammonia, which belongs to the class of hazardous substances. In addition, ammonia causes corrosion of copper-containing alloys. For small boiler houses (as opposed to thermal power plants), it is simply unrealistic to use traditional corrective water treatment technologies for the reasons listed above. There are two options left: not to carry out corrective treatment at all, reducing the operating efficiency and service life of the main equipment, or to use effective and easy-to-use modern reagents (albeit quite expensive), the costs of which may not be so high at low replenishment volumes. Modern reagents are supplied in liquid form, ready for use, and can be diluted with softened water in any proportions. When using them, no special reagent facilities are required; only a solution tank and a dispenser pump are sufficient.

Water treatment– the process of changing the composition of water by removing organic and mineral impurities and microorganisms or adding substances to bring its composition and properties in accordance with consumer requirements. According to the final purpose of water use, a distinction is made between water treatment for drinking (including domestic) and industrial needs.

Water for drinking needs must meet the requirements of sanitary, epidemiological and radiation safety, be harmless in chemical composition and have favorable organoleptic properties. This is achieved by removing nutrients, heavy metals, halogen derivatives, bacteria, etc., as well as, if necessary, adding missing microelements.

When preparing water for industrial needs, coarse and colloidal impurities, salts and microorganisms are removed from the water to prevent the formation of scale, corrosion of metals, clogging of pipelines and contamination of processed materials when water is used in technological processes. Thus, in heat power engineering, where water is the coolant, it is important to remove hardness salts and other impurities in ionic form from water, since an increase in temperature during the heating process leads to the formation of scale in the technical elements of the system - boilers, pipelines, cooling towers. Technological stages of water treatment for industrial needs and for drinking purposes often completely coincide.

History of water treatment

The first mention of the use of drinking water preparation methods to improve its quality - improving taste and removing odor - dates back to the 4th millennium BC. e. At that time, water treatment methods such as filtration through charcoal, standing in the sun and boiling. To eliminate turbidity, i.e., remove suspended particles from water, the ancient Egyptians, as early as 1.5 thousand years BC. e. aluminum alum was used. In the 17th century The filtration method began to be used to prepare drinking water, but the degree of water purification was insufficient. WITH early XIX V. sand filters were used in most European cities. In 1806, the first large water treatment station was put into operation in Paris, where the water went through the stages of sedimentation and filtration through sand and coal filters. In 1870, R. Koch and D. Lister proved that microorganisms found in water supplies can cause infectious diseases. Subsequently, at the beginning of the twentieth century. these discoveries led to the use of drinking water disinfection methods. In 1906 in Nice, the ozonation method was used to disinfect drinking water, and in 1908 in the USA, calcium hypochlorite began to be used as a disinfectant. Since 1926, the coagulation method began to be used to remove suspended particles. In the 1940s The development of ion exchange technologies for water desalination began, and in 1957 the first membrane filters appeared, but they entered widespread water treatment practice much later. In the second half of the twentieth century. In most developed countries, complex schemes for the preparation of drinking water have begun to be used, including technologies for sedimentation, filtration, coagulation, disinfection, etc.

Target components of surface and groundwater during water treatment

When preparing water for drinking or industrial needs, depending on the end use, the content of representatives of the following groups of substances is brought to standard values:

The chemical and biological composition of water determines the choice of water treatment technologies used and the technological schemes used.

Water treatment technologies

When drawing water from a surface water body (river, reservoir, lake, etc.), the first stage of water preparation is preliminary purification, which usually includes the following methods:

• filtering is the process of passing water through permeable partitions of various designs to remove large floating contaminants and suspended impurities. It is carried out through gratings and sieves with cell sizes from 0.005 mm to 1 cm;
• primary sedimentation is the process of sedimentation of suspended substances under the influence of gravity, which also leads to water clarification. Depends on flow speed, relative density and particle diameter. Particles larger than 100 microns (10 -4 m) are removed from water;
• coagulation is the process of enlargement of colloidal and dispersed particles with the introduction of reagents - coagulants, which occurs due to the adhesion of particles under the influence of molecular attraction forces. The stuck together particles are subsequently deposited. Suspended substances and a significant part of microorganisms are removed from the water, which leads to its deep clarification.

Water softening– the process of removing dissolved alkaline earth metal salts (Ca 2+ and Mg 2+) from water, which cause water hardness. Hardness salts can be removed in four ways:

• reagent softening - adding reagents that increase the concentration of anions; as a result, poorly soluble salts with Ca 2+ and Mg 2+ ions are formed, which subsequently precipitate. Sedimentation processes are carried out in settling tanks and clarifiers. The sedimentation of the resulting flocs occurs very slowly, so the equipment has low productivity. Reagent methods are used only in the preparation of water for technical needs, since the water as a result acquires a highly alkaline reaction;
• Ion exchange is a process in which anions and cations present in water are replaced by other ions as they pass through a layer of ion-exchange material. The exchange of Ca 2+ and Mg 2+ cations for Na + leads to water softening. The anionic composition of the water does not change, and the solution remains neutral;
• electrochemical treatment - the passage of water through the interelectrode space, during which, due to electrolysis, less soluble forms of hardness salts are formed;
• membrane filtration – passing water through nanofiltration and reverse osmosis membranes under high pressure, resulting in selective retention of multi-charged and large ions. Suspended substances, colloids, bacteria, viruses, etc. are also removed. The content of hardness salts is reduced by 10–50 times.

Deferrization of water. In the water of surface sources, iron, as a rule, is usually in the form of organomineral colloidal complexes, in underground water sources - in the form of dissolved ferrous bicarbonate. To deferrize water from surface sources, reagent methods are used followed by filtration in combination with pre-treatment of water:

• aeration oxidizes ferrous iron with air oxygen, while carbon dioxide is removed from the water, which accelerates the process of formation of iron hydroxide;
• coagulation and clarification are used for iron in the form of suspensions and colloidal dispersed matter (see above);
• treatment with oxidizing reagents (chlorine, sodium or calcium hypochlorite, ozone, potassium permanganate) leads to the destruction of humates and other iron-containing organic compounds. As a result, easily hydrolyzed inorganic salts of ferric iron are formed.

Deferrization of groundwater is also carried out by membrane filtration (micro-, ultra-, nanofiltration or reverse osmosis).

Disinfection– the process of destroying viruses and pathogenic microorganisms (bacteria, protozoa) by disinfecting agents and/or physical influences. The effectiveness of water disinfection directly depends on the degree of its preliminary purification, since the removal of colloidal and dispersed particles from water increases the supply of disinfectant to the target objects of disinfection - bacteria, viruses, protozoa. The following methods are used for disinfection:

In practice, a combination of various disinfection methods is most often used to reduce the negative effect of some and enhance the dignity of others.

Degassing of water. The presence of dissolved gases in water – oxygen, free carbon dioxide and hydrogen sulfide – determines its corrosive properties. The following methods of water degassing are used:

• chemical methods involve adding reagents that bind gases dissolved in water, or passing water through filters loaded with steel filings;
• physical methods of degassing - the most common are aeration and boiling water. Boiling is used to remove oxygen from water, and aeration is used to remove free carbon dioxide and hydrogen sulfide.

Correction of drinking water quality. A number of macro- and microelements important for the body (iodine, fluorine, calcium, magnesium, etc.) enter the human body along with drinking water. However, often water from a water source does not contain such substances in the required quantities. To adjust the composition of drinking water, the following methods are used:

• fluoride enrichment (fluoridation) is an accessible and safe method of preventing caries by increasing the fluoride concentration to 0.6–1.1 mg/l;
• enrichment with iodine (iodization). Lack of iodine in some cases causes the development of congenital anomalies, increased perinatal mortality, decreased mental abilities in children and adults, and deaf-muteness. The iodine content in drinking water should be at the level of 40–60 μg/l;
• enrichment with selenium. Selenium is an antioxidant, strengthens the immune system and metabolic processes in the body. Addition of selenium to drinking water is used as a concomitant factor in reducing the risk of developing oncological diseases, cardiovascular pathologies, arthritis, premature aging of the population;
• calcium enrichment. Lack of calcium leads to cardiovascular diseases (hypertension, coronary and coronary heart disease, stroke), rickets in children, osteomalacia, and impaired blood clotting;
• magnesium enrichment. Magnesium deficiency leads to an increase in the severity of cardiovascular diseases and infant mortality;
• enrichment with bicarbonate ions is used to correct the pH value of water and increase its alkalinity.

The active development of industry and the growth of urbanization led over several centuries to current state ecology, in which you cannot risk drinking water even from a well, not to mention some surface source. When building new houses outside the city, people prefer to drill wells. Other nearby sources are also adapted, but they certainly use filtering installations, and sometimes even entire stations. In its “raw” form, water always has various impurities, especially if it is extracted from the depths. There may even be toxic substances present: natural hydrogen sulfide or phenols, nitrates and other contaminants that have entered the groundwater from industrial waste. If the house is connected to the municipal supply system, thenbuy water treatmentI'll have to go there too. City filtration stations actively use chlorine, which remains in the liquid after use. Other quality characteristics of water are also brought only to compliance with SanPiN requirements. That is, many substances are not completely eliminated, but only their concentration is reduced.

use of membrane or other low-permeability materials;

ion exchange;

magnetic and electromagnetic influence;

ultraviolet radiation.

The use of each of these technologies must be justified by the characteristics of the object, the required cleaning parameters, the availability of purchase, maintenance and other nuances. Modern water treatment has a serious approach and several stages. Professionals first carry out a laboratory analysis of the source, and based on its results, specific cleaning methods and equipment are selected that are best suited to the individual characteristics of each object. By contacting NTK Soltek LLC, you can receive a full range of services: from design calculations to installation and further maintenance of treatment plants.