is a complex of special structures designed to purify wastewater from the contaminants it contains. Purified water is either used further or discharged into natural reservoirs (Great Soviet Encyclopedia).

Every settlement needs effective wastewater treatment plants. The operation of these complexes determines what water will enter the environment and how this will subsequently affect the ecosystem. If liquid waste is not cleaned up at all, not only will plants and animals die, but the soil will also be poisoned, and harmful bacteria can enter the human body and cause serious consequences.

Every enterprise that has toxic liquid waste is required to operate a treatment plant system. Thus, this will affect the state of nature and improve human living conditions. If treatment systems work effectively, wastewater will become harmless when it enters the ground and water bodies. The size of treatment facilities (hereinafter - OS) and the complexity of treatment strongly depend on the contamination of wastewater and its volume. More details about the stages of wastewater treatment and types of O.S. read on.

Stages of wastewater treatment

The most indicative in terms of the presence of water purification stages are urban or local OS, designed for large populated areas. It is household wastewater that is most difficult to treat, as it contains various pollutants.

It is typical for sewerage water treatment facilities that they are built in a certain sequence. Such a complex is called a treatment plant line. The scheme begins with mechanical cleaning. Grates and sand traps are most often used here. This is the initial stage of the entire water treatment process.

This could be leftover paper, rags, cotton wool, bags and other debris. After the grates, sand traps come into operation. They are necessary in order to retain sand, including large sizes.

Mechanical stage of wastewater treatment

Initially, all water from the sewer enters the main pumping station into a special reservoir. This reservoir is designed to compensate for the increased load during peak hours. A powerful pump evenly pumps the appropriate volume of water to pass through all stages of cleaning.

catch large debris larger than 16 mm - cans, bottles, rags, bags, food, plastic, etc. Subsequently, this waste is either processed on site or transported to sites for processing solid household and industrial waste. The gratings are a type of transverse metal beams, the distance between which is several centimeters.

In fact, they catch not only sand, but also small pebbles, glass fragments, slag, etc. Sand settles to the bottom quite quickly under the influence of gravity. Then the settled particles are raked by a special device into a recess at the bottom, from where they are pumped out. The sand is washed and disposed of.

. Here all impurities that float to the surface of the water (fats, oils, petroleum products, etc.) are removed. By analogy with a sand trap, they are also removed with a special scraper, only from the surface of the water.

4. Settling tanks– an important element of any treatment plant line. In them, water is freed from suspended substances, including helminth eggs. They can be vertical and horizontal, single-tier and two-tier. The latter are the most optimal, since in this case the water from the sewer in the first tier is purified, and the sediment (silt) that has formed there is discharged through a special hole into the lower tier. How does the process of releasing suspended solids from sewer water take place in such structures? The mechanism is quite simple. Sedimentation tanks are large, round or rectangular shaped tanks where substances settle under the influence of gravity.

To speed up this process, you can use special additives - coagulants or flocculants. They promote the sticking together of small particles due to a change in charge; larger substances settle faster. Thus, sedimentation tanks are indispensable structures for purifying water from sewers. It is important to take into account that they are also actively used in simple water treatment. The principle of operation is based on the fact that water enters from one end of the device, while the diameter of the pipe at the exit becomes larger and the flow of liquid slows down. All this contributes to the sedimentation of particles.

mechanical wastewater treatment can be used depending on the degree of water contamination and the design of a specific treatment facility. These include: membranes, filters, septic tanks, etc.

If we compare this stage with conventional water treatment for drinking purposes, then in the latter version such structures are not used and there is no need for them. Instead, processes of water clarification and discoloration occur. Mechanical cleaning is very important, since in the future it will allow for more effective biological treatment.

Biological wastewater treatment plants

Biological treatment can be either an independent treatment facility or an important stage in a multi-stage system of large urban treatment complexes.

The essence of biological treatment is to remove various pollutants (organics, nitrogen, phosphorus, etc.) from water using special microorganisms (bacteria and protozoa). These microorganisms feed on harmful contaminants contained in the water, thereby purifying it.

From a technical point of view, biological treatment is carried out in several stages:

– a rectangular tank where water, after mechanical purification, is mixed with activated sludge (special microorganisms), which purifies it. There are 2 types of microorganisms:

• Aerobic– using oxygen to purify water. When using these microorganisms, the water must be enriched with oxygen before entering the aeration tank.
• Anaerobic– DO NOT use oxygen to purify water.

Necessary for removing unpleasantly smelling air with its subsequent purification. This workshop is necessary when the volume of wastewater is large enough and/or treatment facilities are located near populated areas.

Here the water is purified from activated sludge by settling it. Microorganisms settle to the bottom, where they are transported to the pit using a bottom scraper. A surface scraper mechanism is provided to remove floating sludge.

The purification scheme also includes sludge digestion. The most important treatment facility is the digester. It is a reservoir for the fermentation of sludge, which is formed during settling in two-tier primary settling tanks. During the fermentation process, methane is produced, which can be used in other technological operations. The resulting sludge is collected and transported to special sites for thorough drying. Sludge beds and vacuum filters are widely used for sludge dewatering. After this, it can be disposed of or used for other needs. Fermentation occurs under the influence of active bacteria, algae, and oxygen. The sewer water purification scheme may also include biofilters.

It is best to place them before the secondary settling tanks, so that substances that are carried away with the flow of water from the filters can settle in the settling tanks. It is advisable to use so-called pre-aerators to speed up cleaning. These are devices that help saturate water with oxygen to accelerate aerobic processes of oxidation of substances and biological treatment. It should be noted that sewerage water purification is conventionally divided into 2 stages: preliminary and final.

The treatment plant system may include biofilters instead of filtration and irrigation fields.

- These are devices where wastewater is purified by passing through a filter containing active bacteria. It consists of solid substances, which can be granite chips, polyurethane foam, polystyrene foam and other substances. A biological film consisting of microorganisms forms on the surface of these particles. They decompose organic matter. As biofilters become dirty, they need to be cleaned periodically.

Wastewater is fed into the filter in doses, otherwise high pressure can destroy beneficial bacteria. After biofilters, secondary settling tanks are used. The sludge formed in them goes partly into the aeration tank, and the rest of it goes to the sludge compactors. The choice of one or another biological treatment method and type of treatment facility largely depends on the required degree of wastewater treatment, topography, soil type and economic indicators.

Wastewater tertiary treatment

After passing through the main stages of treatment, 90-95% of all contaminants are removed from wastewater. But the remaining pollutants, as well as residual microorganisms and their metabolic products, do not allow this water to be discharged into natural reservoirs. In this regard, various wastewater treatment systems were introduced at wastewater treatment plants.

In bioreactors the process of oxidation of the following pollutants occurs:

• organic compounds that were too tough for microorganisms,
• these microorganisms themselves,
• ammonium nitrogen.

This happens by creating conditions for the development of autotrophic microorganisms, i.e. converting inorganic compounds into organic ones. For this purpose, special plastic backfill discs with a high specific surface area are used. Simply put, these are disks with a hole in the center. To speed up processes in the bioreactor, intensive aeration is used.

Filters purify water using sand. The sand is continuously updated automatically. Filtration is carried out in several installations by supplying water to them from the bottom up. In order to avoid using pumps and not wasting electricity, these filters are installed at a level lower than other systems. Filter washing is designed in such a way that it does not require a large amount of water. Therefore, they do not occupy such a large area.

Ultraviolet water disinfection

Disinfection or disinfection of water is an important component that ensures its safety for the body of water into which it will be discharged. Disinfection, that is, the destruction of microorganisms, is the final stage of sewerage wastewater treatment. A wide variety of methods can be used for disinfection: ultraviolet irradiation, alternating current, ultrasound, gamma irradiation, chlorination.

Ural irradiation is a very effective method that destroys approximately 99% of all microorganisms, including bacteria, viruses, protozoa, and helminth eggs. It is based on the ability to destroy the membrane of bacteria. But this method is not used so widely. In addition, its effectiveness depends on the turbidity of the water and the content of suspended substances in it. And UV lamps quickly become covered with a coating of mineral and biological substances. To prevent this, special emitters of ultrasonic waves are provided.

The most commonly used method after treatment facilities is chlorination. Chlorination can be different: double, superchlorination, with preammonization. The latter is necessary to prevent unpleasant odors. Superchlorination involves exposure to very large doses of chlorine. Double action means that chlorination is carried out in 2 stages. This is more typical for water treatment. The method of chlorinating sewer water is very effective, in addition, chlorine has an aftereffect that other cleaning methods cannot boast of. After disinfection, the wastewater is discharged into a reservoir.

Phosphate removal

Phosphates are salts of phosphoric acids. They are widely used in synthetic detergents (washing powders, dishwashing detergents, etc.). Phosphates entering water bodies lead to their eutrophication, i.e. turning into a swamp.

Purification of wastewater from phosphates is carried out by dosed addition of special coagulants to the water before biological treatment facilities and before sand filters.

Auxiliary premises of treatment facilities

Aeration shop

is the active process of saturating water with air, in this case by passing air bubbles through the water. Aeration is used in many processes in wastewater treatment plants. Air supply is carried out by one or more blowers with frequency converters. Special oxygen sensors regulate the amount of air supplied so that its content in the water is optimal.

Disposal of excess activated sludge (microorganisms)

At the biological stage of wastewater treatment, excess sludge is formed, as microorganisms actively multiply in aeration tanks. Excess sludge is dewatered and disposed of.

The dehydration process takes place in several stages:

1. Added to excess sludge special reagents, which suspend the activity of microorganisms and promote their thickening
2. IN sludge compactor the sludge is compacted and partially dewatered.
3. On centrifuge the sludge is squeezed out and any remaining moisture is removed from it.
4. In-line dryers With the help of continuous circulation of warm air, the sludge is finally dried. The dried sludge has a residual moisture content of 20-30%.
5. Then packed into sealed containers and disposed of
6. The water removed from the sludge is sent back to the beginning of the cleaning cycle.

Air cleaning

Unfortunately, wastewater treatment plants don't smell the best. The biological wastewater treatment stage is especially smelly. Therefore, if the treatment plant is located near populated areas or the volume of wastewater is so large that a lot of bad-smelling air is generated, you need to think about cleaning not only the water, but also the air.

Air purification usually takes place in 2 stages:

1. Initially, polluted air is supplied to bioreactors, where it comes into contact with specialized microflora adapted for recycling organic substances contained in the air. It is these organic substances that cause bad odors.
2. The air goes through a disinfection stage with ultraviolet light to prevent these microorganisms from entering the atmosphere.

Laboratory at wastewater treatment plants

All water that leaves treatment plants must be systematically monitored in the laboratory. The laboratory determines the presence of harmful impurities in water and whether their concentrations comply with established standards. If one or another indicator is exceeded, treatment plant workers conduct a thorough inspection of the corresponding treatment stage. And if a malfunction is detected, it is eliminated.

Administrative and amenity complex

The personnel servicing the treatment plant can reach several dozen people. For their comfortable work, an administrative and amenity complex is being created, which includes:

• Equipment repair workshops
• Laboratory
• Control room
• Offices of administrative and management personnel (accounting, human resources, engineering, etc.)
• Head office.

Power supply O.S. performed according to the first reliability category. Since a long shutdown of O.S. due to lack of electricity may cause O.S. output. out of service.

To prevent emergency situations, power supply O.S. carried out from several independent sources. The branch of the transformer substation provides for the input of a power cable from the city power supply system. As well as the introduction of an independent source of electric current, for example, from a diesel generator, in case of an emergency in the city power grid.

Conclusion

Based on all of the above, we can conclude that the design of treatment facilities is very complex and includes various stages of treating wastewater from sewers. First of all, you need to know that this scheme applies only to domestic wastewater. If industrial wastewater occurs, then in this case special methods are additionally included that will be aimed at reducing the concentration of hazardous chemicals. In our case, the cleaning scheme includes the following main stages: mechanical, biological cleaning and disinfection (disinfection).

Mechanical cleaning begins with the use of grates and sand traps, which trap large debris (rags, paper, cotton wool). Sand traps are needed to sediment excess sand, especially coarse sand. This is of great importance for subsequent stages. After screens and sand traps, the sewer water treatment plant scheme includes the use of primary settling tanks. Suspended substances settle in them under the force of gravity. To speed up this process, coagulants are often used.

After settling tanks, the filtration process begins, which is carried out mainly in biofilters. The mechanism of action of the biofilter is based on the action of bacteria that destroy organic substances.

The next stage is secondary settling tanks. The silt that was carried away by the current of liquid settles in them. After them, it is advisable to use a digester, in which the sludge is fermented and transported to sludge sites.

The next stage is biological treatment using an aeration tank, filtration fields or irrigation fields. The final stage is disinfection.

Types of treatment facilities

A variety of structures are used for water treatment. If it is planned to carry out this work on surface water immediately before its supply to the city’s distribution network, then the following structures are used: settling tanks, filters. For wastewater, a wider range of devices can be used: septic tanks, aeration tanks, digesters, biological ponds, irrigation fields, filtration fields, and so on. There are several types of treatment plants depending on their purpose. They differ not only in the volume of water being purified, but also in the presence of stages of its purification.

City wastewater treatment plants

Data from O.S. are the largest of all, they are used in large cities and towns. In such systems, particularly effective methods of liquid purification are used, for example, chemical treatment, methane tanks, flotation units. They are designed for the treatment of municipal wastewater. These waters are a mixture of domestic and industrial wastewater. Therefore, there are a lot of pollutants in them, and they are very diverse. The water is purified to meet the standards for discharge into a fishery reservoir. The standards are regulated by Order of the Ministry of Agriculture of Russia dated December 13, 2016 No. 552 “On approval of water quality standards for water bodies of fishery importance, including standards for maximum permissible concentrations of harmful substances in the waters of water bodies of fishery importance.”

In OS data, as a rule, all stages of water purification described above are used. The most illustrative example is the Kuryanovsky wastewater treatment plant.

Kuryanovsky O.S. are the largest in Europe. Its capacity is 2.2 million m3/day. They serve 60% of Moscow's wastewater. The history of these objects goes back to 1939.

Local treatment facilities

Local treatment facilities are structures and devices designed to treat the subscriber's wastewater before discharging it into the public sewerage system (defined by Decree of the Government of the Russian Federation of February 12, 1999 No. 167).

There are several classifications of local OS, for example, there are local OS. connected to the central sewerage and autonomous. Local O.S. can be used on the following objects:

• In small towns
• In the villages
• In sanatoriums and boarding houses
• At car washes
• On personal plots
• At manufacturing plants
• And at other facilities.

Local O.S. can vary greatly from small units to capital structures that are maintained daily by qualified personnel.

Treatment facilities for a private home.

Several solutions are used to dispose of wastewater from a private home. They all have their advantages and disadvantages. However, the choice always remains with the home owner.

1. Cesspool. In truth, this is not even a treatment facility, but simply a tank for temporary storage of wastewater. When the pit is filled, a sewage disposal truck is called, which pumps out the contents and takes it away for further processing.

This archaic technology is still used today due to its cheapness and simplicity. However, it also has significant disadvantages, which sometimes negate all its advantages. Wastewater can enter the environment and groundwater, thereby polluting it. It is necessary to provide a normal entrance for the sewer truck, since it will have to be called quite often.

2. Storage. It is a container made of plastic, fiberglass, metal or concrete into which wastewater is drained and stored. They are then pumped out and disposed of by a sewer truck. The technology is similar to a cesspool, but the water does not pollute the environment. The disadvantage of such a system is the fact that in the spring, when there is a large amount of water in the ground, the storage tank can be squeezed out to the surface of the earth.

3. Septic tank- are large containers, in which substances such as coarse dirt, organic compounds, stones and sand precipitate, and elements such as various oils, fats and petroleum products remain on the surface of the liquid. The bacteria that live inside the septic tank extract oxygen for life from the fallen sediment, while reducing the level of nitrogen in the wastewater. When the liquid leaves the sump, it becomes clarified. It is then purified using bacteria. However, it is important to understand that phosphorus remains in such water. For final biological treatment, irrigation fields, filtration fields or filter wells can be used, the operation of which is also based on the action of bacteria and activated sludge. Plants with a deep root system cannot be grown in this area.

A septic tank is very expensive and can take up a large area. It should be borne in mind that this is a structure that is designed to treat small amounts of domestic wastewater from the sewer system. However, the result is worth the money spent. The structure of a septic tank is shown more clearly in the figure below.

4. Deep biological treatment stations are already a more serious treatment facility, unlike a septic tank. This device requires electricity to operate. However, the quality of water purification is up to 98%. The design is quite compact and durable (up to 50 years of operation). To service the station, there is a special hatch at the top, above the ground surface.

Stormwater treatment plants

Despite the fact that rainwater is considered quite clean, it collects various harmful elements from asphalt, roofs and lawns. Garbage, sand and petroleum products. To ensure that all this does not end up in nearby water bodies, stormwater treatment facilities are being created.

In them, water undergoes mechanical purification in several stages:

1. Sump. Here, under the influence of the Earth's gravity, large particles - pebbles, glass fragments, metal parts, etc. - settle to the bottom.
2. Thin layer module. Here, oils and petroleum products collect on the surface of the water, where they are collected on special hydrophobic plates.
3. Sorption fiber filter. It catches everything that the thin-layer filter missed.
4. Coalescent module. It helps to separate oil particles that float to the surface and are larger than 0.2 mm in size.
5. Carbon filter after purification. It finally rids the water of all petroleum products that remain in it after passing through the previous stages of purification.

Design of wastewater treatment plants

Design of O.S. determine their cost, choose the right treatment technology, ensure reliable operation of the structure, and bring wastewater to quality standards. Experienced specialists will help you find effective installations and reagents, draw up a wastewater treatment plan and put the installation into operation. Another important point is drawing up an estimate that will allow you to plan and control expenses, as well as make adjustments if necessary.

For the project O.S. The following factors greatly influence:

• Wastewater volumes. Designing structures for a personal plot is one thing, but designing structures for treating wastewater in a cottage community is another. Moreover, it must be taken into account that the capabilities of O.S. must be greater than the current amount of wastewater.
• Terrain. Wastewater treatment facilities require access to special vehicles. It is also necessary to provide for the power supply of the facility, the removal of purified water, and the location of the sewage system. O.S. may occupy a large area, but they should not interfere with neighboring buildings, structures, roads and other structures.
• Wastewater pollution. The technology for treating storm water is very different from treating domestic water.
• Required level of cleaning. If the customer wants to save on the quality of purified water, then it is necessary to use simple technologies. However, if you need to discharge water into natural reservoirs, then the quality of treatment must be appropriate.
• Competence of the performer. If you order O.S. from inexperienced companies, then get ready for unpleasant surprises in the form of an increase in construction estimates or a septic tank floating in the spring. This happens because they forget to include quite critical points in the project.
• Technological features. The technologies used, the presence or absence of treatment stages, the need to construct systems servicing the treatment facility - all this must be reflected in the project.
• Other. It is impossible to foresee everything in advance. As the treatment plant is designed and installed, various changes may be made to the design plan that could not be foreseen at the initial stage.

Stages of designing a treatment plant:

1. Preliminary work. They include studying the site, clarifying the customer’s wishes, analyzing wastewater, etc.
2. Collection of permits. This point is usually relevant for the construction of large and complex structures. For their construction, it is necessary to obtain and approve the relevant documentation from the supervisory authorities: MOBVU, MOSRYBVOD, Rosprirodnadzor, SES, Hydromet, etc.
3. Choice of technology. Based on paragraphs 1 and 2, the necessary technologies used for water purification are selected.
4. Drawing up an estimate. Construction costs O.S. must be transparent. The customer must know exactly how much the materials cost, what the price of the installed equipment is, what the workers' wage fund is, etc. You should also consider the costs of subsequent system maintenance.
5. Cleaning efficiency. Despite all the calculations, the cleaning results may be far from desired. Therefore, already at the planning stage O.S. it is necessary to conduct experiments and laboratory studies that will help avoid unpleasant surprises after construction is completed.
6. Development and approval of project documentation. To begin construction of treatment facilities, it is necessary to develop and agree on the following documents: a draft sanitary protection zone, a draft standards for permissible discharges, a draft maximum permissible emissions.

Installation of treatment facilities

After the O.S. project has been prepared and all necessary permits have been obtained, the installation stage begins. Although the installation of a country septic tank is very different from the construction of a sewage treatment plant in a cottage community, they still go through several stages.

First, the area is prepared. A pit is being dug to install a treatment plant. The floor of the pit is filled with sand and compacted or concreted. If a treatment plant is designed for a large amount of wastewater, then, as a rule, it is built on the surface of the earth. In this case, the foundation is poured and a building or structure is already installed on it.

Secondly, the installation of equipment is carried out. It is installed, connected to the sewerage and drainage system, and to the electrical network. This stage is very important because it requires personnel to know the specifics of the operation of the equipment being configured. It is incorrect installation that most often causes equipment failure.

Thirdly, inspection and delivery of the object. After installation, the finished treatment facility is tested for the quality of water treatment, as well as for its ability to operate under high load conditions. After checking O.S. is handed over to the customer or his representative, and also, if necessary, undergoes a state control procedure.

Treatment plant maintenance

Like any equipment, the treatment plant also needs maintenance. Primarily from O.S. It is necessary to remove large debris, sand, and excess silt that are formed during cleaning. On large O.S. the number and type of elements removed can be significantly greater. But in any case, they will have to be deleted.

Secondly, the functionality of the equipment is checked. Malfunctions in any element can lead not only to a decrease in the quality of water purification, but also to the failure of all equipment.

Thirdly, if a breakdown is detected, the equipment must be repaired. And it’s good if the equipment is under warranty. If the warranty period has expired, then repair O.S. you will have to do it at your own expense.

Water at modern water supply stations undergoes multi-stage purification to remove solid impurities, fibers, colloidal suspensions, microorganisms, and to improve organoleptic properties. The highest quality result is achieved by a combination of two technologies: mechanical filtration and chemical treatment.

Features of cleaning technologies

Mechanical filtration. The first stage of water treatment allows you to remove visible solid and fibrous inclusions from the medium: sand, rust, etc. During mechanical treatment, water is successively passed through a series of filters with decreasing cell sizes.

Chemical treatment. The technology is used to bring the chemical composition and quality indicators of water to normal. Depending on the initial characteristics of the medium, treatment may include several stages: settling, disinfection, coagulation, softening, clarification, aeration, demineralization, filtration.

Methods of chemical water purification at waterworks

Advocacy

At water supply stations, special tanks with an overflow mechanism are installed or reinforced concrete settling tanks are installed at a depth of 4–5 m. The speed of water movement inside the tank is maintained at a minimum level, and the upper layers flow faster than the lower ones. Under such conditions, heavy particles settle to the bottom of the tank and are removed from the system through drainage channels. On average, it takes 5–8 hours for water to settle. During this time, up to 70% of heavy impurities settle.

Disinfection

Purification technology is aimed at removing dangerous microorganisms from water. Disinfection installations are present in all water supply systems without exception. Disinfection of water can be done by irradiation or the addition of chemicals. Despite the advent of modern technologies, the use of chlorine-based disinfectants is preferable. The reason for the popularity of the reagents is the good solubility of chlorine-containing compounds in water, the ability to remain active in a moving environment, and have a disinfecting effect on the internal walls of the pipeline.

Coagulation

The technology allows you to remove dissolved impurities that are not captured by filter meshes. Polyoxychloride or aluminum sulfate and potassium-aluminum alum are used as coagulants for water. The reagents cause coagulation, that is, the sticking together of organic impurities, large protein molecules, and suspended plankton. Large heavy flakes form in the water, which precipitate, carrying with them organic suspensions and some microorganisms. To speed up the reaction, flocculants are used at treatment stations. Soft water is alkalized with soda or lime to quickly form flakes.

Softening

The content of calcium and magnesium compounds (hardness salts) in water is strictly regulated. To remove impurities, filters with cationic or anionic ion exchange resins are used. When water passes through the load, hardness ions are replaced by hydrogen or sodium, which is safe for human health and the plumbing system. The resin's absorption capacity is restored by backwashing, but the capacity decreases each time. Due to the high cost of materials, this water softening technology is used mainly in local treatment plants.

Lightening

The technique is used to purify surface waters contaminated with fulvic acids, humic acids, and organic impurities. Liquid from such sources often has a characteristic color, taste, and greenish-brown tint. At the first stage, water is sent to the mixing chamber with the addition of a chemical coagulant and a chlorine-containing reagent. Chlorine destroys organic inclusions, and coagulants remove them into sediment.

Aeration

The technology is used to remove ferrous iron, manganese, and other oxidizing impurities from water. With pressure aeration, the liquid is bubbled with an air mixture. Oxygen dissolves in water, oxidizes gases and metal salts, removing them from the environment in the form of sediment or insoluble volatile substances. The aeration column is not completely filled with liquid. An air cushion above the surface of the water softens water hammer and increases the area of ​​contact with air.

Non-pressure aeration requires simpler equipment and is carried out in special shower installations. Inside the chamber, water is sprayed through ejectors to increase the area of ​​contact with air. If the iron content is high, aeration complexes can be supplemented with ozonizing equipment or filter cassettes.

Demineralization

The technology is used to prepare water in industrial water supply systems. Demineralization removes excess iron, calcium, sodium, copper, manganese and other cations and anions from the environment, increasing the service life of process pipelines and equipment. To purify water, reverse osmosis, electrodialysis, distillation or deionization technology is used.

Filtration

Water is filtered by passing through carbon filters, or charcoalization. The sorbent absorbs up to 95% of impurities, both chemical and biological. Until recently, pressed cartridges were used to filter water at waterworks, but their regeneration is a rather expensive process. Modern complexes include a powdered or granular coal charge, which is simply poured into a container. When mixed with water, coal actively removes impurities without changing its state of aggregation. The technology is cheaper but just as effective as block filters. Coal loading removes heavy metals, organics, and surfactants from the water. The technology can be used at treatment plants of any type.

What quality of water does the consumer receive?

Water becomes potable only after undergoing a full range of treatment measures. Then it goes to city communications for delivery to the consumer.

It is necessary to take into account that even if the water parameters at treatment plants fully comply with sanitary and hygienic standards at the water collection points, its quality may be significantly lower. The reason is old, rusty communications. Water becomes contaminated as it passes through the pipeline. Therefore, the installation of additional filters in apartments, private houses and enterprises remains a pressing issue. Properly selected equipment ensures that water meets regulatory requirements and even makes it healthy.

Due to the fact that the volume of water consumption is continuously growing, and underground water sources are limited, the water shortage is compensated by surface water bodies.
The quality of drinking water must meet high standard requirements. And the normal and stable operation of devices and equipment depends on the quality of water used for industrial purposes. Therefore, this water must be well purified and meet the standards.

But in most cases, the quality of water is low, and the problem of water purification today is of great relevance.
It is possible to improve the quality of wastewater treatment, which is then planned to be used for drinking and economic purposes, by using special methods for their purification. For this purpose, complexes of treatment facilities are built, which are then combined into water treatment plants.

But attention should be paid to the problem of purifying not only the water that will then be used for food. Any wastewater, after going through certain stages of purification, is discharged into water bodies or onto the terrain. And if they contain harmful impurities, and their concentration is higher than permissible values, then a serious blow is dealt to the environment. Therefore, all measures to protect reservoirs, rivers and nature in general begin with improving the quality of wastewater treatment. Special facilities that serve for wastewater treatment, in addition to their main function, also allow the extraction of useful impurities from wastewater, which can be used in the future, possibly even in other industries.
The degree of wastewater treatment is regulated by legislative acts, namely “Rules for the protection of surface waters from pollution by wastewater” and “Fundamentals of water legislation of the Russian Federation”.
All complexes of treatment facilities can be divided into water supply and sewerage. Each type can be further divided into subspecies, differing in structural features, composition, as well as technological purification processes.

Water treatment plants

The methods of water purification used, and, accordingly, the composition of the treatment facilities themselves, are determined by the quality of the source water and the requirements for the water that needs to be obtained at the outlet.
Cleaning technology includes the processes of clarification, bleaching and disinfection. This happens through the processes of sedimentation, coagulation, filtration and treatment with chlorine. If the water is not initially very polluted, then some technological processes are skipped.

The most common methods for clarification and decolorization of wastewater in water treatment plants are coagulation, filtration and sedimentation. Often, water is settled in horizontal settling tanks and filtered using various media or contact clarifiers.
The practice of constructing water treatment facilities in our country has shown that the most widely used devices are those that are designed in such a way that horizontal settling tanks and fast filters act as the main treatment elements.

Uniform requirements for purified drinking water predetermine the almost identical composition and structure of structures. Let's give an example. Without exception, all water treatment plants (regardless of their power, performance, type and other features) include the following components:
- reagent devices with a mixer;
- flocculation chambers;
- horizontal (less often vertical) settling chambers and clarifiers;
- ;
- containers for purified water;
- ;
- auxiliary, administrative and household facilities.

Sewage treatment plants

Sewage treatment plants have a complex engineering structure, just like water treatment systems. At such facilities, wastewater goes through the stages of mechanical, biochemical (also called) and chemical treatment.

Mechanical wastewater treatment allows you to separate suspended solids, as well as coarse impurities, by straining, filtering and settling. In some treatment facilities, mechanical cleaning is the final stage of the process. But often it is only a preparatory stage for biochemical purification.

The mechanical component of the wastewater treatment complex consists of the following elements:
- gratings that retain large impurities of mineral and organic origin;
- sand traps, which allow you to separate heavy mechanical impurities (usually sand);
- settling tanks for separating suspended particles (often of organic origin);
- chlorination devices with contact tanks, where clarified wastewater is disinfected under the influence of chlorine.
Such wastewater after disinfection can be discharged into a reservoir.

Unlike mechanical cleaning, with the chemical cleaning method, mixers and reagent units are installed in front of the settling tanks. Thus, after passing through the grate and sand trap, wastewater enters the mixer, where a special coagulation reagent is added to it. And then the mixture is sent to the settling tank for clarification. After the settling tank, the water is released either into the reservoir, or to the subsequent purification stage, where additional clarification occurs, and then it is released into the reservoir.

The biochemical method of wastewater treatment is often carried out in the following facilities: filtration fields, or in biofilters.
In filtration fields, wastewater, after passing through the purification stage in screens and sand traps, enters settling tanks for clarification and deworming. They then follow to irrigation or filtration fields, after which they are discharged into the reservoir.
When treated in biofilters, wastewater goes through stages of mechanical treatment and then undergoes forced aeration. Next, the wastewater containing oxygen enters the biofilter structures, and after it is sent to a secondary settling tank, where suspended substances and excess water removed from the biofilter are deposited. After this, the treated wastewater is disinfected and discharged into the reservoir.
Wastewater treatment in aeration tanks goes through the following stages: grates, sand traps, forced aeration, settling. Then the pre-treated wastewater enters the aeration tank, and then into secondary settling tanks. This cleaning method ends in the same way as the previous one - with a disinfection procedure, after which the wastewater can be discharged into a reservoir.

The main methods for improving the quality of natural water and the composition of structures depend on the quality of the water at the source and the purpose of the water supply system. The main methods of water purification include:

1. lightening, which is achieved by settling water in a settling tank or clarifiers to settle suspended particles in the water and filtering the water through a filter material;

2. disinfection(disinfection) to destroy pathogenic bacteria;

3. softening– reduction of calcium and magnesium salts in water;

4. special water treatment– desalting (desalination), deferrization, stabilization – used mainly for production purposes.

The diagram of facilities for the preparation of drinking water using a settling tank and filter is shown in Fig. 1.8.

Purification of natural water for drinking purposes consists of the following measures: coagulation, clarification, filtration, disinfection using chlorination.

Coagulation used to accelerate the process of sedimentation of suspended substances. To do this, chemical reagents, so-called coagulants, are added to the water, which react with the salts in the water, promoting the precipitation of suspended and colloidal particles. The coagulant solution is prepared and dosed in installations called reagent facilities. Coagulation is a very complex process. Basically, coagulants enlarge suspended substances by sticking them together. Aluminum or iron salts are added to water as a coagulant. The most commonly used are aluminum sulfate Al2(SO4)3, ferrous sulfate FeSO4, and ferric chloride FeCl3. Their quantity depends on the pH of the water (the active pH reaction of the water is determined by the concentration of hydrogen ions: pH=7 neutral environment, pH>7 acidic, pH<7-щелочная). Доза коагулянта зависит от мутности и цветности воды и определяется согласно СНиП РК 04.01.02.–2001 «Водоснабжение. Наружные сети и сооружения». Для коагулирования используют мокрый способ дозирования реагентов. Коагулянт вводят в воду уже растворенный. Для этого имеется растворный бак, два расходных бака, где готовится раствор определенной концентрации путем добавления воды. Готовый раствор коагулянта подается в дозировочный бачок, имеющий поплавковый клапан, поддерживающий постоянный уровень воды. Затем из него раствор подается в смесители.

Rice. 1.8. Schemes of water treatment stations: with a floc formation chamber, settling tanks and filters (A); with clarifier with suspended sediment and filters (B)

1 – first lift pump; 2 – reagent shop; 3 – mixer; 4 – flocculation chamber; 5 – settling tank; 6 – filter; 7 – pipeline for chlorine inlet; 8 – purified water tank; 9 – second lift pump; 10 – clarifier with suspended sediment

To speed up the coagulation process, flocculants are introduced: polyacrylamide, silicic acid. The most common designs of mixers are: baffle, perforated and vortex. The mixing process must take place until flakes form, so the water stays in the mixer for no more than 2 minutes. The baffle mixer is a tray with partitions at an angle of 45°. The water changes its direction several times, forming intense vortices, and promotes mixing of the coagulant. Hole mixers - there are holes in the transverse partitions; water passing through them also forms turbulence, promoting mixing of the coagulant. Vortex mixers are vertical mixers where mixing occurs due to the turbulization of a vertical flow.

From the mixer, water flows into the flocculation chamber (reaction chamber). Here it stays for 10 - 40 minutes to obtain large flakes. The speed of movement in the chamber is such that the flakes do not fall out and are destroyed.

The flocculation chambers are distinguished: whirlpool, baffle, bladed, vortex, depending on the mixing method. Partitioned - a reinforced concrete tank is divided by partitions (longitudinal) into corridors. Water passes through them at a speed of 0.2 - 0.3 m/s. The number of corridors depends on the turbidity of the water. Blade – with a vertical or horizontal shaft arrangement of the mixers. Vortex - a reservoir in the form of a hydrocyclone (conical, expanding upward). Water enters from below and moves at a decreasing speed from 0.7 m/s to 4 - 5 mm/s, while the peripheral layers of water are drawn into the main one, creating a vortex movement, which promotes good mixing and flocculation. From the flocculation chamber, water flows into the settling tank or clarifiers for clarification.

Lightening is the process of separating suspended substances from water as it moves at low speeds through special structures: settling tanks, clarifiers. The sedimentation of particles occurs under the influence of gravity, because The specific gravity of particles is greater than the specific gravity of water. Water supply sources have different levels of suspended solids, i.e. have different turbidity, therefore, the duration of clarification will be different.

There are horizontal, vertical and radial sedimentation tanks.

Horizontal settling tanks are used when the station capacity is more than 30,000 m 3 /day; they are a rectangular tank with a reverse bottom slope to remove accumulated sediment by backwashing. Water is supplied from the end. Relatively uniform movement is achieved by installing perforated partitions, spillways, collection pockets, and gutters. The settling tank can be two-sectional, with a section width of no more than 6 m. The settling time is 4 hours.

Vertical settling tanks – with a treatment station capacity of up to 3000 m 3 /day. In the center of the sump there is a pipe into which water is supplied. The settling tank is round or square in plan with a conical bottom (a=50-70°). The water flows down the sump through a pipe, and then rises up at low speed into the working part of the sump, where it is collected through a weir in a circular tray. The upward flow speed is 0.5 – 0.75 mm/s, i.e. it must be less than the sedimentation rate of suspended particles. In this case, the diameter of the settling tank is no more than 10 m, the ratio of the settling tank diameter to the settling height is 1.5. The number of settling tanks is at least 2. Sometimes the settling tank is combined with a flocculation chamber, which is located instead of the central pipe. In this case, water flows out of the nozzle tangentially at a speed of 2–3 m/s, creating conditions for floc formation. To dampen rotational motion, grates are installed at the bottom of the settling tank. The settling time in vertical settling tanks is 2 hours.

Radial settling tanks are round tanks with a slightly conical bottom; they are used in industrial water supply with a high content of suspended particles and a capacity of more than 40,000 m 3 /day.

Water is supplied to the center and then moves radially to a collection tray around the periphery of the sump, from which it is discharged through a pipe. Lightening also occurs due to the creation of low speeds of movement. The settling tanks have a shallow depth of 3–5 m in the center, 1.5–3 m at the periphery, and a diameter of 20–60 m. The sediment is removed mechanically, with scrapers, without stopping the operation of the settling tank.

Clarifiers. The lightening process in them occurs more intensely, because After coagulation, water passes through a layer of suspended sediment, which is maintained in this state by a flow of water (Fig. 1.9).

Particles of suspended sediment contribute to greater enlargement of coagulant flakes. Large flakes can retain more suspended particles in the clarified water. This principle underlies the operation of clarifiers with suspended sediment. With equal volumes to settling tanks, clarifiers have greater productivity and require less coagulant. To remove air that can agitate suspended sediment, water is first directed to the air separator. In a corridor-type clarifier, the clarified water is supplied through a pipe from below and distributed through perforated pipes in the side compartments (corridors) in the lower part.

The speed of the upward flow in the working part should be 1-1.2 mm/s so that the coagulant flakes are suspended. When passing through a layer of suspended sediment, suspended particles are retained, the height of the suspended sediment is 2 - 2.5 m. The degree of clarification is higher than in a settling tank. Above the working part there is a protective zone where there is no suspended sediment. Then the clarified water enters a collection tray, from which it is supplied to the filter through a pipeline. The height of the working part (clarification zone) is 1.5-2 m.

Water filtering. After clarification, the water is filtered; for this purpose, filters are used that have a layer of fine-grained filter material, in which fine suspended particles are retained as the water passes. Filter material – quartz sand, gravel, crushed anthracite. Filters are fast, ultra-high-speed, slow: fast - work with coagulation; slow – without coagulation; ultra-high-speed – with and without coagulation.

There are pressure filters (high-speed), non-pressure filters (fast and slow). In pressure filters, water passes through the filter layer under pressure created by pumps. In non-pressure ones - under the pressure created by the difference in water levels in the filter and at the outlet from it.

Rice. 1.9. Corridor type suspended sediment clarifier

1 – working chamber; 2 – sediment compactor; 3 – windows covered with visors; 4 – pipelines for supplying clarified water; 5 – pipelines for sediment release; 6 – pipelines for collecting water from the sediment compactor; 7 – valve; 8 – gutters; 9 – collection tray

In open (non-pressure) rapid filters, water is supplied from the end into a pocket and passes from top to bottom through the filter layer and the supporting layer of gravel, then through the perforated bottom it enters the drainage, from there through a pipeline into a clean water reservoir. The filter is flushed with reverse current through the outlet pipeline from the bottom up, the water is collected in the flush gutters and then discharged into the sewer. The thickness of the filter media depends on the sand size and is assumed to be 0.7 - 2 m. The estimated filtration speed is 5.5-10 m/h. Washing time is 5-8 minutes. The purpose of drainage is to uniformly discharge filtered water. Now they use two-layer filters, first loading (from top to bottom) crushed anthracite (400 - 500 mm), then sand (600 - 700 mm), supporting a gravel layer (650 mm). The last layer serves to prevent the filter media from being washed out.

In addition to the single-flow filter (which has already been mentioned), double-flow filters are used, in which water is supplied in two flows: from above and from below, and filtered water is discharged through one pipe. Filtration speed – 12 m/hour. The productivity of a double-flow filter is 2 times greater than that of a single-flow filter.

Water disinfection. When settling and filtering, most of the bacteria are retained, up to 95%. The remaining bacteria are destroyed as a result of disinfection.

Water disinfection is achieved in the following ways:

1. Chlorination is carried out with liquid chlorine and bleach. The chlorination effect is achieved by intensively mixing chlorine with water in a pipeline or in a special tank for 30 minutes. 2-3 mg of chlorine is added per 1 liter of filtered water, and 6 mg of chlorine per 1 liter of unfiltered water. Water supplied to the consumer must contain 0.3 - 0.5 mg of chlorine per 1 liter, the so-called residual chlorine. Usually double chlorination is used: before and after filtration.

Chlorine is dosed in special chlorinators, which are either pressure or vacuum. Pressure chlorinators have a disadvantage: liquid chlorine is under pressure above atmospheric pressure, so gas leaks are possible, which is toxic; vacuum ones do not have this drawback. Chlorine is delivered in liquefied form in cylinders, from which chlorine is poured into an intermediate one, where it turns into a gaseous state. The gas enters the chlorinator, where it dissolves in tap water to form chlorine water, which is then introduced into the pipeline transporting the water intended for chlorination. When the dose of chlorine increases, an unpleasant odor remains in the water; such water must be dechlorinated.

2. Ozonation is the disinfection of water with ozone (oxidation of bacteria with atomic oxygen obtained from the splitting of ozone). Ozone removes color, odors and tastes from water. To disinfect 1 liter of underground sources, 0.75 - 1 mg of ozone is required, 1 liter of filtered water from surface sources requires 1-3 mg of ozone.

3. Ultraviolet irradiation is produced using ultraviolet rays. This method is used to disinfect underground sources with low flow rates and filtered water from surface sources. High- and low-pressure mercury-quartz lamps serve as radiation sources. There are pressure units that are installed in pressure pipelines, non-pressure units - on horizontal pipelines and in special channels. The disinfection effect depends on the duration and intensity of the radiation. This method is not applicable to waters of high turbidity.

Water supply network

Water supply networks are divided into main and distribution networks. Main - transport transit masses of water to objects of consumption, distribution - supply water from mains to individual buildings.

When routing water supply networks, one should take into account the layout of the water supply facility, the location of consumers, and the terrain.

Rice. 1.10. Water supply network diagrams

a – branched (dead-end); b – ring

Based on their plan outline, water supply networks are divided into: dead-end and ring.

Dead-end networks are used for those water supply facilities that allow interruptions in the water supply (Fig. 1.10, a). Ring networks are more reliable in operation because... in the event of an accident on one of the lines, consumers will be supplied with water through the other line (Fig. 1.10, b). Fire-fighting water supply networks must be ring-shaped.

For external water supply, cast iron, steel, reinforced concrete, asbestos-cement, and polyethylene pipes are used.

Cast iron pipes with anti-corrosion coating are durable and widely used. Disadvantage: poor resistance to dynamic loads. Cast iron pipes are socketed, with a diameter of 50–1200 mm and a length of 2–7 m. The pipes are asphalted from the inside and outside to prevent corrosion. The joints are sealed with tarred strands using caulk, then the joint is sealed with asbestos cement and compacted using a hammer and caulking.

Steel pipes with a diameter of 200 – 1400 mm are used for laying water pipelines and distribution networks at pressures greater than 10 atm. Steel pipes are connected by welding. Water and gas pipes - on threaded couplings. The outside of steel pipes is covered with bitumen mastic or kraft paper in 1 - 3 layers. According to the method of manufacturing the pipes, they are distinguished: straight-seam welded pipes with a diameter of 400 - 1400 mm, a length of 5 - 6 m; seamless (hot rolled) with a diameter of 200 – 800 mm.

Asbestos cement pipes They are produced with a diameter of 50 - 500 mm, a length of 3 - 4 m. The advantage is dielectricity (they are not affected by stray electric currents). Disadvantage: subject to mechanical stress associated with dynamic loads. Therefore, care must be taken during transportation. The connection is a coupling with rubber rings.

Reinforced concrete pipes with a diameter of 500 - 1600 mm are used as water conduits, the connection is finger-type.

Polyethylene pipes are resistant to corrosion, strong, durable, and have less hydraulic resistance. The disadvantage is the large coefficient of linear expansion. When choosing pipe material, design conditions and climatic data should be taken into account. For normal operation, the following fittings are installed on water supply networks: shut-off and control fittings (gate valves, valves), water taps (dispensers, taps, hydrants), safety fittings (check valves, air plungers). Inspection wells are installed in places where fittings and fittings are installed. Water supply wells on networks are made of precast reinforced concrete.

Calculation of the water supply network consists of establishing a pipe diameter sufficient to pass the calculated flow rates and determining the pressure losses in them. The depth of laying water pipes depends on the depth of soil freezing and the material of the pipes. The depth of pipes (to the bottom of the pipe) should be 0.5 m below the calculated depth of soil freezing in a given climatic region.

One of the main objectives of the enterprise is the effective purification of water obtained from natural surface sources in order to provide residents with high-quality drinking water. The classic technological scheme used at Moscow water treatment stations allows this task to be accomplished. However, ongoing trends in the deterioration of water quality in water sources due to anthropogenic impact and the tightening of drinking water quality standards dictate the need to increase the degree of purification.

With the beginning of the new millennium in Moscow, for the first time in Russia, in addition to the classical scheme, highly efficient innovative technologies for the preparation of drinking water of a new generation are being used. Projects of the 21st century are modern treatment plants, in which classical technology is supplemented with ozonation and sorption processes on activated carbon. Thanks to ozone sorption, water is better purified from chemical contaminants, unpleasant odors and tastes are eliminated, and additional disinfection occurs.

The use of innovative technologies eliminates the influence of seasonal changes in the quality of natural water, ensures reliable deodorization of drinking water, and its guaranteed epidemic safety even in cases of emergency contamination of the water supply source. In total, about 50% of all treated water is prepared using new technologies.

Along with the introduction of new methods of water purification, disinfection processes are being improved. In order to increase the reliability and safety of drinking water production by eliminating liquid chlorine from circulation, in 2012 the transition of all water treatment stations to a new reagent - sodium hypochlorite was completed. In connection with the tightening of state standards for the content of chloroform in drinking water, a targeted development of disinfection regimes was carried out, as a result why the concentration of chloroform in Moscow tap water, according to average data for 2018, did not exceed 5 - 13 μg/l, with the standard being 60 μg/l.

Technological schemes for the purification of artesian waters are individual for each facility, taking into account the characteristics of the water quality of the exploited aquifers and contain the following steps: deferrization; softening; water conditioning using carbon sorption filters; removal of heavy metal impurities; disinfection with sodium hypochlorite or using ultraviolet lamps.

Today, in the Troitsky and Novomoskovsky administrative districts of Moscow, about half of the water intake units supply water that has undergone technological processing.

The phased introduction of new technologies is carried out in accordance with the General Scheme for the development of the water supply system, which provides that the complete reconstruction of all water treatment facilities will make it possible to supply water of the highest quality to all residents of the Moscow metropolis.