The Village continues to tell how the things that the townspeople use every day work. In this issue - the sewerage system. After we press the flush button on the toilet, turn off the faucet and go about our business, tap water turns into sewage and begins its journey. To get back into the Moscow River, she needs to go through kilometers of sewer networks and several stages of cleaning. How this happens, The Village found out by visiting the city's wastewater treatment plant.

Through the pipes

At the very beginning, water enters the internal pipes of the house with a diameter of only 50-100 millimeters. Then it goes along the network a little wider - courtyards, and from there - to street ones. At the border of each yard network and at the point of its transition to the street, a manhole is installed, through which you can monitor the operation of the network and clean it if necessary.

The length of city sewer pipes in Moscow is more than 8 thousand kilometers. The entire territory through which the pipes pass is divided into parts - pools. The section of the network that collects wastewater from the pool is called a collector. Its diameter reaches three meters, which is twice as large as the pipe in the water park.

Basically, due to the depth of the foundation and the natural topography of the territory, the water flows through the pipes itself, but in some places pumping stations are required, there are 156 of them in Moscow.

Wastewater enters one of the four treatment facilities. The cleaning process is continuous, and the peaks of the hydraulic load occur at 12 noon and 12 noon. Kuryanovskie treatment facilities, which are located near Maryin and are considered one of the largest in Europe, receive water from the southern, southeastern and southwestern parts of the city. Effluent from the northern and eastern parts of the city is fed to treatment plants in Lyubertsy.

Treatment

Kuryanovsk treatment facilities are designed for 3 million cubic meters of wastewater per day, but only one and a half comes here. 1.5 million cubic meters is 600 Olympic pools.

Previously, this place was called the aeration station, it was launched in December 1950. Now the treatment plant is 66 years old, and Vadim Gelievich Isakov worked here for 36 of them. He came here as a foreman of one of the workshops and became the head of the technological department. When asked if he expected to spend his whole life in such a place, Vadim Gelievich replies that he no longer remembers, it was so long ago.

Isakov says that the station consists of three cleaning units. In addition, there is a whole complex of facilities for the treatment of sediments that are formed in the process.

mechanical cleaning

Muddy and foul-smelling sewage comes to the treatment plant warm. Even in the coldest time of the year, its temperature does not fall below plus 18 degrees. Waste water is met by a receiving and distributing chamber. But what happens there, we will not see: the cell was completely closed so that the smell did not spread. By the way, the smell on the huge (almost 160 hectares) territory of the treatment plant is quite tolerable.

After that, the stage of mechanical cleaning begins. Here, on special gratings, garbage that floated along with the water is retained. Most often, these are rags, paper, personal hygiene products (napkins, diapers), as well as food waste - for example, potato peelings and chicken bones. “What you will not meet. It used to be that bones and skins from meat processing plants sailed, ”they say with a shudder in the sewage treatment plants. Of the pleasant - only gold jewelry, although we did not find eyewitnesses of such a catch. Seeing the trash-retaining grate is the most terrible part of the tour. In addition to all the nastiness, many, many circles of lemons were stuck in it: “You can guess the time of the year by the contents,” the employees say.

A lot of sand comes with wastewater, and so that it does not settle on structures and clog pipelines, it is removed in sand traps. Sand in liquid form enters a special area, where it is washed with technical water and becomes ordinary, that is, suitable for landscaping. Wastewater treatment plants use sand for their own needs.

The stage of mechanical cleaning in the primary settling tanks is being completed. These are large tanks in which fine suspension is removed from the water. Here the water comes in cloudy, and leaves clarified.

Biological treatment

Biological treatment begins. It takes place in structures called aerotanks. They artificially support the vital activity of a community of microorganisms, which are called activated sludge. Organic pollution in water is the most desirable food for microorganisms. Air is supplied to the aeration tanks, which does not allow the sludge to settle, so that it comes into contact with the wastewater as much as possible. This goes on for eight or ten hours. “Similar processes take place in any natural reservoir. The concentration of microorganisms there is hundreds of times lower than what we create. Under natural conditions, this would last for weeks and months,” Isakov says.

The aerotank is a rectangular tank divided into sections, in which waste water snakes. “If you look through a microscope, then everything is crawling, moving, moving, swimming. We make them work for our benefit,” our guide says.

At the outlet of the aeration tanks, a mixture of purified water and activated sludge is obtained, which now need to be separated from each other. This problem is solved in secondary settling tanks. There, the sludge settles on the bottom, is collected by sludge pumps, after which 90% is returned to the aeration tanks for a continuous cleaning process, and 10% is considered excess and is disposed of.

Return to the river

Biologically purified water undergoes tertiary treatment. To check it, it is filtered through a very fine sieve, and then it is dumped into the outlet channel of the station, on which there is an ultraviolet disinfection unit. Ultraviolet disinfection is the fourth and final stage of cleaning. At the station, the water is divided into 17 channels, each of which is illuminated by a lamp: the water in this place acquires an acidic hue. This is a modern and the largest such block in the world. Although according to the old project it was not, earlier they wanted to disinfect the water with liquid chlorine. “It’s good that it didn’t come to that. We would have killed all living things in the Moscow River. The reservoir would be sterile, but dead,” says Vadim Gelievich.

Simultaneously with water treatment, sludge is dealt with at the station. Sludge from the primary clarifiers and excess activated sludge are treated together. They enter the digesters, where, at a temperature of plus 50-55 degrees, the process of fermentation goes on for almost a week. As a result, the sediment loses its ability to rot and does not emit an unpleasant odor. This sludge is then pumped to dewatering facilities outside the Moscow Ring Road. “30–40 years ago, the sediment was dried on silt beds under natural conditions. This process lasted from three to five years, but now the dehydration is instantaneous. The sediment itself is a valuable mineral fertilizer, in Soviet times it was popular, state farms took it with pleasure. But now no one needs it, and the station pays up to 30% of the total cleaning costs for disposal, ”says Vadim Gelievich.

A third of the sludge breaks down, turning into water and biogas, which saves on disposal. Part of the biogas is burned in a boiler house, and part is sent to a combined heat and power plant. A thermal power plant is not an ordinary element of treatment facilities, but rather a useful addition that gives treatment plants relative energy independence.

Fish in the sewers

Previously, there was an engineering center with its own production base on the territory of the Kuryanovsky wastewater treatment plant. Employees set up unusual experiments, for example, they bred sterlet and carp. Some of the fish lived in tap water, and some in the sewer, which was cleaned. Now, fish is found only in the discharge channel, there are even signs “Fishing is prohibited” hanging there.

After all the purification processes, the water flows through the discharge channel - a small river 650 meters long - into the Moscow River. Here and everywhere, where the process takes place in the open air, many seagulls swim on the water. “They do not interfere with the processes, but spoil the aesthetic appearance,” Isakov is sure.

The quality of treated wastewater released into the river is much better than the water in the river in terms of all sanitary indicators. But drinking such water without boiling is not recommended.

The volume of treated waste water is equal to approximately one third of all water in the Moscow River above the discharge. If the sewage treatment plants were to fail, the settlements downstream would be on the verge of an ecological catastrophe. But this is practically impossible.

- This is a complex of special facilities designed to treat wastewater from the contaminants contained in them. Purified water is either used in the future, or discharged into natural reservoirs (Great Soviet Encyclopedia).

Each settlement needs effective treatment facilities. The operation of these complexes determines what water will enter the environment and how it will affect the ecosystem in the future. If liquid waste is not treated at all, then not only plants and animals will die, but the soil will also be poisoned, and harmful bacteria can enter the human body and cause serious consequences.

Each enterprise that has toxic liquid waste is obliged to deal with a system of treatment facilities. Thus, it will affect the state of nature, and improve the conditions of human life. If the treatment complexes work effectively, then the wastewater will become harmless when it enters the ground and water bodies. The size of treatment facilities (hereinafter referred to as O.S.) and the complexity of treatment are highly dependent on the contamination of wastewater and their volumes. In more detail 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 stages of water purification are urban or local OS, designed for large settlements. It is domestic wastewater that is the most difficult to treat, as it contains heterogeneous pollutants.

For facilities for the purification of water from sewerage, it is characteristic that they line up in a certain sequence. Such a complex is called a line of treatment facilities. The scheme begins with mechanical cleaning. Here gratings and sand traps are most often used. This is the initial stage of the entire water treatment process.

It can be the remains of paper, rags, cotton wool, bags and other debris. After gratings, sand traps come into operation. They are necessary in order to retain sand, including large sizes.

Mechanical Stage Wastewater Treatment

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

catch large debris over 16 mm - cans, bottles, rags, bags, food, plastic, etc. In the future, this garbage is either processed on site or taken to the places of processing of solid household and industrial waste. Lattices are a type of transverse metal beams, the distance between which is equal to several centimeters.

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

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

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

To speed up this process, you can use special additives - coagulants or flocculants. They contribute to the adhesion of small particles due to a change in charge, larger substances are deposited faster. Thus, sedimentation tanks are indispensable facilities for purifying water from sewers. It is important to consider that with simple water treatment they are also actively used. 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 fluid flow slows down. All this contributes to the deposition of particles.

mechanical wastewater treatment can be used depending on the degree of water pollution and the design of a particular treatment plant. 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 facilities are not used, they are not necessary. Instead, the processes of clarification and discoloration of water occur. Mechanical cleaning is very important, as in the future it will allow more efficient biological cleaning.

Biological wastewater treatment plants

Biological treatment can be both an independent treatment facility and an important stage in a multi-stage system of large urban treatment facilities.

The essence of biological treatment is to remove various pollutants (organics, nitrogen, phosphorus, etc.) from water with the help of 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 cleaning is mixed with activated sludge (special microorganisms), which cleans it. Microorganisms are of 2 types:

• Aerobic using oxygen to purify water. When using these microorganisms, the water must be enriched with oxygen before it enters the aerotank.
• Anaerobic– NOT using oxygen for water purification.

It is necessary to remove 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 settlements.

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

The treatment scheme also includes sludge digestion. Of the treatment facilities, the methane tank is important. It is a tank for the digestion of sediment, which is formed during settling in two-tiered primary clarifiers. During the digestion 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 dehydration. After that, it can be disposed of or used for other needs. Fermentation occurs under the influence of active bacteria, algae, oxygen. Biofilters may also be included in the sewerage water treatment scheme.

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

The system of treatment facilities 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 used as granite chips, polyurethane foam, polystyrene and other substances. A biological film consisting of microorganisms forms on the surface of these particles. They decompose organic matter. Biofilters need to be cleaned periodically as they get dirty.

Wastewater is fed into the filter in a dosed manner, otherwise a large pressure can kill beneficial bacteria. After biofilters, secondary clarifiers are used. The sludge formed in them enters partly into the aerotank, and the rest of it goes to the sludge thickeners. The choice of one or another method of biological treatment and the type of treatment facilities largely depends on the required degree of wastewater treatment, topography, soil type and economic indicators.

Post-treatment of wastewater

After passing 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 systems for post-treatment of wastewater were introduced at treatment facilities.

In bioreactors, the following pollutants are oxidized:

• 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, special plastic charging disks with a high specific surface area are used. Simply put, these discs have a hole in the center. Intensive aeration is used to speed up the processes in the bioreactor.

Filters purify water with sand. The sand is continuously updated automatically. Filtration is carried out on several installations by supplying water to them from the bottom up. In order not to use pumps and not to waste 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.

Disinfection of water with ultraviolet light

Disinfection or disinfection of water is an important component that ensures its safety for the reservoir into which it will be discharged. Disinfection, that is, the destruction of microorganisms, is the final step in the purification of sewage effluents. A wide variety of methods can be used for disinfection: ultraviolet irradiation, alternating current, ultrasound, gamma irradiation, chlorination.

UVR is a very effective method by which approximately 99% of all microorganisms are destroyed, including bacteria, viruses, protozoa, helminth eggs. It is based on the ability to destroy the bacterial membrane. But this method is not widely used. In addition, its effectiveness depends on the turbidity of the water, the content of suspended solids in it. And UVI lamps quite 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 of chlorination after sewage treatment plants. Chlorination can be different: double, superchlorination, with preammonization. The latter is necessary to prevent an unpleasant odor. Superchlorination involves exposure to very large doses of chlorine. Dual action is that chlorination is carried out in 2 stages. This is more typical for water treatment. The method of chlorinating water from the sewer is very effective, in addition, chlorine has an aftereffect that other cleaning methods cannot boast of. After disinfection, the waste 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, getting into water bodies, lead to their eutrophication, i.e. turning into a swamp.

Wastewater treatment from phosphates is carried out by dosed addition of special coagulants to water in front of biological treatment facilities and in front of sand filters.

Auxiliary premises of treatment facilities

Aeration shop

- this is an 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 is supplied 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, since microorganisms actively multiply in the aeration tanks. Excess sludge is dehydrated and disposed of.

The dehydration process takes place in several stages:

1. In excess sludge is added special reagents, which stop the activity of microorganisms and contribute to their thickening
2. AT sludge thickener the sludge is compacted and partially dehydrated.
3. On the centrifuge the sludge is squeezed out and the remaining moisture is removed from it.
4. Inline 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 ooze packed in sealed containers and disposed of
6. The water removed from the sludge is sent back to the beginning of the purification cycle.

Air cleaning

Unfortunately, the sewage treatment plant does not smell the best. Particularly smelly is the stage of biological wastewater treatment. Therefore, if the treatment plant is located near settlements or the volume of wastewater is so large that there is a lot of bad-smelling air, you need to think about cleaning not only water, but also air.

Air purification, as a rule, takes place in 2 stages:

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

Laboratory at the wastewater treatment plant

All water that leaves the treatment plant must be systematically monitored in the laboratory. The laboratory determines the presence of harmful impurities in the water and the compliance of their concentration with the established standards. In case of exceeding one or another indicator, the workers of the treatment plant conduct a thorough inspection of the corresponding stage of treatment. And if a problem is found, they fix it.

Administrative and amenity complex

The personnel serving the treatment plant can reach several tens of people. For their comfortable work, an administrative and amenity complex is being created, it includes:

• Equipment repair shops
• Laboratory
• control room
• Offices of administrative and managerial personnel (accounting, personnel service, engineering, etc.)
• Head office.

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

To prevent emergency situations, the power supply of O.S. comes from several independent sources. In the department of the transformer substation, the input of a power cable from the city power supply system is provided. As well as the input of an independent source of electric current, for example, from a diesel generator, in case of an accident in the city power grid.

Conclusion

Based on the foregoing, it can be concluded that the scheme of treatment facilities is very complex and includes various stages of wastewater treatment from sewers. First of all, you need to know that this scheme applies only to domestic wastewater. If there are industrial effluents, then in this case they additionally include special methods 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 gratings and sand traps, in which large debris (rags, paper, cotton wool) is retained. Sand traps are needed to settle excess sand, especially coarse sand. This is of great importance for the next steps. After gratings and grit traps, the sewerage treatment plant scheme includes the use of primary clarifiers. Suspended matter settles in them under the force of gravity. Coagulants are often used to speed up this process.

After the 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 matter.

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

The next stage is biological treatment with the help of an aeration tank, filtration fields or irrigation fields. The final step is disinfection.

Types of treatment facilities

A variety of facilities are used for water treatment. If it is planned to carry out these works in relation to surface waters immediately before they are supplied to the distribution network of the city, then the following facilities are used: sedimentation 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. Wastewater treatment plants are of several types depending on their purpose. They differ not only in the volume of treated water, but also in the presence of stages of its purification.

City wastewater treatment plant

Data from O.S. are the largest of all, they are used in large metropolitan areas and cities. Such systems use particularly effective liquid treatment methods, such as chemical treatment, methane tanks, flotation units. They are designed to treat 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 waters are purified to the standards for discharge into a reservoir for fishery purposes. The standards are regulated by the order of the Ministry of Agriculture of Russia dated December 13, 2016 No. 552 “On approval of water quality standards for fishery water bodies, including standards for maximum permissible concentrations of harmful substances in the waters of fishery water bodies”.

On O.S. data, as a rule, all stages of water purification described above are used. The most illustrative example is the Kuryanovsk treatment facilities.

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

Local treatment facilities

Local treatment facilities are facilities and devices designed to treat the subscriber's wastewater before they are discharged into the public sewerage system (the definition is given by Decree of the Government of the Russian Federation of February 12, 1999 No. 167).

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

• In small towns
• In the settlements
• In sanatoriums and boarding houses
• At car washes
• On household plots
• At manufacturing plants
• And on other sites.

Local O.S. can be very different from small units to permanent structures that are serviced daily by qualified personnel.

Treatment facilities for a private house.

Several solutions are used for the disposal of wastewater from a private house. All of them have their advantages and disadvantages. However, the choice always remains with the owner of the house.

1. Cesspool. In truth, this is not even a treatment plant, but simply a reservoir for temporary storage of wastewater. When the pit is filled, a sewage truck is called in, which pumps out the contents and transports it for further processing.

This archaic technology is still used today because of its cheapness and simplicity. However, it also has significant drawbacks, which, at times, nullify all its advantages. Wastewater can enter the environment and groundwater, thereby polluting them. For a sewage truck, it is necessary to provide for a normal entrance, since it will have to be called quite often.

2. Drive. It is a container made of plastic, fiberglass, metal or concrete, where wastewater is drained and stored. Then they are pumped out and disposed of by a sewage machine. The technology is similar to a cesspool, but the waters do not pollute the environment. The disadvantage of such a system is the fact that in the spring, with a large amount of water in the soil, the drive can be squeezed out to the surface of the earth.

3. Septic tank- is a large container, 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 precipitated sludge, while reducing the level of nitrogen in the wastewater. When the liquid leaves the sump, it becomes clarified. Then it is cleaned with bacteria. However, it is important to understand that phosphorus remains in such water. For the 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. It will not be possible to grow plants with a deep root system 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 facility that is designed to treat a small amount of domestic wastewater from the sewer. However, the result is worth the money spent. The septic tank device is more clearly shown in the figure below.

4. Stations for deep biological treatment are already a more serious treatment plant, 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 at the top, above the ground, there is a special hatch.

Stormwater treatment plants

Despite the fact that rainwater is considered quite clean, however, it collects various harmful elements from asphalt, roofs and lawns. Garbage, sand and oil products. In order to prevent all this from falling into the nearest reservoirs, stormwater treatment facilities are being created.

In them, water undergoes mechanical purification in several stages:

1. Sump. Here, under the influence of the gravity of the Earth, large particles settle to the bottom - pebbles, glass fragments, metal parts, etc.
2. thin layer module. Here, oils and oil products are collected on the surface of the water, where they are collected on special hydrophobic plates.
3. Sorption fibrous filter. It captures everything that the thin layer filter missed.
4. coalescence module. It contributes to the separation of particles of oil products that float to the surface, the size of which is greater than 0.2 mm.
5. Coal filter aftertreatment. It finally rids the water of all oil products that remain in it after passing through the previous stages of purification.

Design of treatment facilities

Designing O.S. determine their cost, choose the right treatment technology, ensure the reliability of the structure, bring wastewater to quality standards. Experienced specialists will help you find effective plants and reagents, draw up a wastewater treatment scheme and put the plant into operation. Another important point is the preparation of a budget that will allow you to plan and control costs, as well as make adjustments if necessary.

For the project O.S. The following factors are strongly influenced:

• Waste water volumes. The design of facilities for a personal plot is one thing, but the design of facilities for wastewater treatment of a cottage village is another. Moreover, it must be taken into account that the possibilities of O.S. must be greater than the current amount of wastewater.
• Locality. Wastewater treatment facilities require the access of special vehicles. It is also necessary to provide for the power supply of the facility, the disposal of purified water, the location of the sewerage system. O.S. can occupy a large area, but they should not interfere with neighboring buildings, structures, road sections and other structures.
• Waste water pollution. Storm water treatment technology is very different from household water treatment.
• Required level of cleaning. If the customer wants to save on the quality of treated water, then it is necessary to use simple technologies. However, if it is necessary 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 that floated up in the spring. This happens because the project forgets to include enough critical points.
• Technological features. The technologies used, the presence or absence of treatment stages, the need to build systems serving the treatment plant - all this should be reflected in the project.
• Other. It is impossible to foresee everything in advance. As the treatment plant is being designed and installed, various changes may be made to the draft plan that could not have been foreseen at the initial stage.

Stages of designing a treatment plant:

1. Preliminary work. They include studying the object, clarifying the wishes of the customer, analyzing wastewater, etc.
2. Collection of permits. This item is usually relevant for the construction of large and complex structures. For their construction, it is necessary to obtain and agree on the relevant documentation from 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 a budget. Construction costs O.S. must be transparent. The customer must know exactly how much the materials cost, what is the price of the installed equipment, what wage fund for workers, etc. You should also take into account the cost of subsequent maintenance of the system.
5. cleaning efficiency. Despite all 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 to avoid unpleasant surprises after construction is completed.
6. Development and approval of project documentation. To start the construction of treatment facilities, it is necessary to develop and agree on the following documents: a draft of a sanitary protection zone, a draft of standards for permissible discharges, a draft of maximum permissible emissions.

Installation of treatment facilities

After the project O.S. has been prepared and all the 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 treatment plant in a cottage village, they still go through several stages.

First, the terrain is being prepared. A pit is being dug for the installation of a treatment plant. The floor of the pit is covered with sand and tamped or concreted. If the 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, to the electrical network. This stage is very important because it requires the personnel to know the specifics of the operation of the configured equipment. It is improper installation that most often causes equipment failure.

Thirdly, checking and handing over the object. After installation, the finished treatment plant is tested for the quality of water treatment, as well as for the ability to work in conditions of increased load. After checking O.S. is handed over to the customer or his representative, and, if necessary, passes the procedure of state control.

Maintenance of treatment facilities

Like any equipment, a sewage treatment plant also needs maintenance. First of all from O.S. it is necessary to remove large debris, sand, as well as excess sludge that are formed during cleaning. On large O.S. the number and type of elements to be removed can be much larger. But in any case, they will have to be removed.

Secondly, the performance of the equipment is checked. Malfunctions in any element can be fraught not only with a decrease in the quality of water purification, but also with the failure of all equipment.

Thirdly, in case of detection of a breakdown, the equipment is subject to repair. And it's good if the equipment is under warranty. If the warranty period has expired, then the repair of O.S. will have to be done at your own expense.

Kuryanovsk treatment facilities (KOS) design capacity 2.2 million m 3 / day, which are the largest in Europe, provide reception and treatment of household and industrial wastewater from the northwestern, western, southern, southeastern regions of Moscow (60% of the city) and, in addition, a number of cities and towns of the Moscow region.
The composition of the WWTP includes three independently functioning wastewater treatment units: the old station (KTPst.) with a design capacity of 1.0 million m 3 per day and the II block of the Novokurianovsk treatment facilities (NKOS-II) - 600 thousand m 3 per day.

WWTPs operate according to the technological scheme of complete biological treatment, including at the reconstructed facilities of NKOS-I and NKOS-II with the removal of biogenic elements: the first stage is mechanical treatment, including filtering water on grates, trapping mineral impurities in sand traps and settling water in primary sedimentation tanks ; the second stage is the biological treatment of water in aerotanks and secondary settling tanks. Part of the biologically treated wastewater undergoes post-treatment on fast filters and is used for the needs of industrial enterprises instead of tap water.

With sewage, a large number of different types of waste enter the WWTP: household items of citizens, waste from food production, plastic containers and plastic bags, as well as construction and other waste. To remove them at the WWTP, mechanized gratings with 10 mm gaps are used.

The second stage of mechanical wastewater treatment is sand traps - structures that serve to remove mineral impurities contained in incoming water. Mineral contaminants in wastewater include: sand, clay particles, solutions of mineral salts, mineral oils. Various types of sand traps are operated at the WWTP - vertical, horizontal and aerated.

After passing the first two stages of mechanical treatment, wastewater enters the primary settling tanks, designed to precipitate undissolved impurities from wastewater. Structurally, all primary settling tanks at the WWTP are of open type and have a radial shape, with different diameters - 33, 40 and 54 m.

The clarified wastewater after the primary settling tanks is subjected to complete biological treatment in aeration tanks. Aerotanks – open reinforced concrete structures of rectangular shape, 4-corridor type. The working depth of the aerotanks of the old block is 4 m, the aerotanks of the NKOS - 6 m. Biological wastewater treatment is carried out using activated sludge with forced air supply.

The sludge mixture from the aeration tanks enters the secondary settling tanks, where the activated sludge is separated from the purified water. Secondary clarifiers are structurally similar to primary clarifiers.

The entire volume of wastewater treated at the WWTP is delivered to the post-treatment facilities. The productivity of the straining section is 3 million m 3 /day, which allows the entire volume of biologically purified water to be passed through flat slotted sieves. Part of the water after filtering is filtered on fast filters and used for technical needs as a circulating water supply.

Starting from 2012, all wastewater that has undergone a full treatment cycle at the Kuryanovsk treatment facilities is subjected to ultraviolet disinfection before being discharged into the Moskva River (capacity 3 million m 3 /day). Thanks to this, the indicators of bacterial contamination of the biologically purified water of the WWTP reached the standard values, which had a beneficial effect on the quality of the water of the Moscow River and the sanitary and epidemiological state of the water area as a whole.

Sludge generated at various stages of wastewater treatment is fed to a single sludge treatment complex, which includes:

• belt thickeners to reduce sludge moisture,
• digesters for digestion and stabilization of sludge in thermophilic mode (50-53 0 C),
• decanter centrifuges for sludge dewatering using flocculants.

The dehydrated sludge is taken out by third parties outside the territory of the treatment facilities for the purpose of neutralization/utilization and/or use for the production of finished products.

Sewer treatment facilities OS, KOS, BOS.

One of the main ways to protect the natural environment from pollution is to prevent the ingress of untreated water and other harmful components into water bodies. Modern treatment facilities are a set of engineering and technical solutions for sequential filtration and disinfection of polluted effluents with a view to their reuse in production or for discharge into natural water bodies. For this, a number of methods and technologies have been developed, which will be discussed below.

More about wastewater treatment technology

Since centralized sewerage systems are not laid in all places, and some industrial enterprises require preliminary preparation of wastewater, today local sewer facilities are very often equipped. They are also in demand in private houses, suburban cottage towns and detached residential complexes, industrial enterprises, workshops.

Wastewater differs in the source of pollution: household, industrial and surface (occurring from atmospheric precipitation). Household drains are called household fecal. They consist of contaminated water removed from showers, toilets, kitchens, canteens and hospitals. The main pollutants are physiological and household waste.

Industrial effluents include water masses that were formed during:

• performance of various production and technological operations;
• washing of raw materials and finished products;
• equipment cooling.

This variety also includes water pumped out of the bowels during the extraction of minerals. Industrial waste is the main source of pollution here. They may contain toxic, potentially hazardous substances, as well as waste that can be recovered and used as secondary raw materials.

Surface (atmospheric) effluents most often contain only mineral contaminants, minimal requirements are imposed on their purification. In addition, wastewater is classified according to the concentration of various pollutants. These characteristics influence the choice of method and number of purification steps. To determine the composition of the equipment, the need for construction, as well as the capacity of various types of structures, a calculation is made of the production of wastewater treatment.

Basic cleaning steps

At the first stage, mechanical wastewater treatment is performed, the purpose of which is filtration from various insoluble impurities. For this, special self-cleaning grids and sieves are used. The retained waste, together with other sludge, is sent for further processing or taken to landfills along with municipal solid waste.

In the sand trap, fine particles of sand, slag and other similar mineral elements are deposited under the influence of gravity. In this case, the filtered composition is suitable for further use after processing. The remaining undissolved substances are reliably retained in special settling tanks and septic tanks, and fats and oil products are extracted using grease traps, oil traps and flotators. At the mechanical treatment stage, up to three quarters of mineral contaminants are removed from waste streams. This ensures the uniformity of the liquid supply to the next stages of processing.

After that, biological cleaning methods are used, performed with the help of microorganisms and protozoa. The first structure where water enters at the biological stage is special primary settling tanks, in which suspended organic matter settles. At the same time, another type of settling tanks is used, in which activated sludge is removed from the bottom. Biological treatment allows you to remove more than 90% of organic contaminants.

At the physico-chemical stage, the dissolved impurities are removed. This is done using special techniques and reagents. It uses coagulation, filtration, and settling. Along with them, various additional processing technologies are used, including: hyperfiltration, sorption, ion exchange, removal of nitrogen-containing substances and phosphates.

The last stage of treatment is chlorine disinfection of the liquid from the remaining bacterial contaminants. The diagram below shows in detail all the stages described, indicating the equipment used in each stage. It is important to note that treatment methods for various industrial enterprises differ depending on the presence of certain pollutants in wastewater.

Features and requirements for the arrangement of treatment facilities

Domestic sewage is classified as monotonous in composition, since the concentration of pollutants depends only on the volume of water consumed by residents. They contain insoluble impurities, emulsions, foams and suspensions, various colloidal particles, and other elements. Their main part is mineral and soluble substances. For the treatment of domestic wastewater, a basic set of treatment facilities is used, the principle of operation of which is described above.

In general, domestic sewers are considered simpler, since they are built to treat wastewater from one or more private houses and outbuildings. They do not require relatively high performance. For this purpose, specially designed installations are used that provide biological wastewater treatment.

Thanks to them, in suburban housing it became possible not only to equip a shower room, bathroom or toilet, but also to connect various household appliances. Typically, such installations are easy to install and operate, do not require additional components.

For industrial effluents, the composition and degree of pollution vary depending on the nature of the production, as well as options for using water to ensure the technological process. In the production of food products, wastewater is characterized by high pollution with organic substances, therefore, biological treatment is considered the main method of treating such water. The best option can be called the use of an aerobic and anaerobic method or a combination of both.

In other industries, the main problem is the treatment of oil and fat-containing effluents. For such enterprises, special oil separators or grease traps are used. But the most safe for the environment are water-circulation systems for the purification of polluted water. Such local treatment complexes are installed at car washes, as well as at manufacturing enterprises. They allow you to organize a closed cycle of water use without its discharge into external water bodies.

Special systems and methods are used to determine the method of organizing cleaning and choosing a specific facility (there are many enterprises, so the process must be individualized). Equally important is the price of equipment and work on its installation. Only experts will help you choose the best option for each case.

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Examples of wastewater treatment plants in major cities

Before considering specific examples of wastewater treatment plants, it is necessary to define what the concepts of the largest, large, medium and small city mean.

With a certain degree of conventionality, cities can be classified according to the number of inhabitants or, taking into account professional specialization, according to the amount of wastewater entering the treatment plant. So for the largest cities with a population of more than 1 million people, the amount of wastewater exceeds 0.4 million m3 / day, for large cities with a population of 100 thousand to 1 million people, the amount of wastewater is 25-400 thousand m3 / day . In medium-sized cities, 50-100 thousand people live, and the amount of wastewater is 10-25 thousand m3 / day. In small towns and urban-type settlements, the number of inhabitants is from 3-50 thousand people (with a possible gradation of 3-10 thousand people; 10-20 thousand people; 25-50 thousand people). At the same time, the estimated amount of wastewater varies in a fairly wide range: from 0.5 to 10-15 thousand m3 / day.

The share of small towns in the Russian Federation is 90% of the total number of towns. It should also be taken into account that the water disposal system in cities can be decentralized and have several treatment facilities.

Let's consider the most significant examples of large treatment facilities in the cities of the Russian Federation: Moscow, St. Petersburg and Nizhny Novgorod.

Kuryanovskaya aeration station (KSA), Moscow. Kuryanovskaya aeration station is the oldest and largest aeration station in Russia; using its example, one can quite clearly study the history of the development of equipment and technology for wastewater treatment in our country.

The area occupied by the station is 380 ha; design capacity - 3.125 million m3 per day; of which almost 2/3 are domestic and 1/3 industrial wastewater. The station has four independent blocks of structures.

The development of the Kuryanovskaya aeration station began in 1950 after the commissioning of a complex of facilities with a capacity of 250 thousand m3 per day. An industrial-experimental technological and constructive base was laid on this block, which was the basis for the development of almost all aeration stations in the country, and was also used in the expansion of the Kuryanovskaya station itself.

On fig. 19.3 and 19.4 are technological schemes for wastewater treatment and sludge treatment of the Kuryanovskaya aeration station.

Wastewater treatment technology includes the following main facilities: gratings, sand traps, primary settling tanks, aeration tanks, secondary settling tanks, wastewater disinfection facilities. Part of the biologically treated wastewater undergoes post-treatment on granular filters.

Rice. 19.3. Technological scheme of wastewater treatment of the Kuryanovskaya aeration station:
1 - lattice; 2 - sand trap; 3 - primary sump; 4 - aerotank; 5 - secondary sump; 6 - flat slotted sieve; 7 - quick filter; 8 – regenerator; 9 - the main machine building of the CBO; 10 – sludge thickener; 11 – gravity belt thickener; 12 – flocculant solution preparation unit; 13 - industrial water pipeline structures; 14 – sand processing shop; 75 - incoming waste water; 16 - wash water from quick filters; 17 - sand pulp; 18 - water from the sand shop; 19 - floating substances; 20 - air; 21 – sludge from primary settling tanks at sludge treatment facilities; 22 - circulating activated sludge; 23 - filtrate; 24 - disinfected process water; 25 - industrial water; 26 - air; 27 - thickened activated sludge for sludge treatment facilities; 28 - disinfected industrial water to the city; 29 - purified water in the river. Moscow; 30 - additionally treated wastewater in the river. Moscow

The KSA is equipped with mechanized gratings with 6 mm gaps with continuously moving scraper mechanisms.

Three types of sand traps are operated at KSA - vertical, horizontal and aerated. After dehydration and processing in a special workshop, sand can be used in road construction and for other purposes.

Radial-type settlers with diameters of 33, 40 and 54 m are used as primary settling tanks at KSA. The design duration of sedimentation is 2 hours. Primary settling tanks in the central part have built-in preaerators.

Biological wastewater treatment is carried out in four-corridor displacer aerotanks, the percentage of regeneration is from 25 to 50%.

Air for aeration is supplied to the aeration tanks through filter plates. At present, to select the optimal aeration system in a number of sections of aeration tanks, tubular polyethylene aerators from the Ecopolymer company, plate aerators from the Greenfrog and Patfil companies are being tested.

Rice. 19.4. Technological scheme for processing sediments of the Kuryanovskaya aeration station:
1 – loading chamber of the digester; 2 – digester; 3 – unloading chamber of digesters; 4 - gas holder; 5 - heat exchanger; 6 - mixing chamber; 7 - washing tank; 8 – digested sludge compactor; 9 - filter press; 10 – flocculant solution preparation unit; 11 - silt platform; 12 – sludge from primary settling tanks; 13 - excess activated sludge; 14 - gas per candle; 15 - fermentation gas to the boiler room of the aeration station; 16 - technical water; 17 - sand on sand platforms; 18 - air; 19 - filtrate; 20 - drain water; 21 - sludge water to the city sewer

One of the sections of the aeration tanks was reconstructed to operate on a single-sludge nitride-denitrification system, which also includes a phosphate removal system.

Secondary settling tanks, as well as primary ones, are of the radial type, with diameters of 33, 40 and 54 m.

About 30% of biologically treated wastewater undergoes post-treatment, which is first treated on flat slotted sieves and then on granular filters.

For sludge digestion at the KSA, buried methane tanks with a diameter of 24 m made of monolithic reinforced concrete with earthen filling are used, ground-based ones with a diameter of 18 m with thermal insulation of the walls. All digesters operate according to the flow scheme, in thermophilic mode. The escaping gas is diverted to the local boiler house. After the digesters, the fermented mixture of raw sludge and excess activated sludge is subjected to compaction. Of the total amount of the mixture, 40-45% is sent to sludge sites, and 55-60% is sent to the mechanical dehydration shop. The total area of ​​silt pads is 380 ha.

Mechanical dehydration of sludge is carried out on eight filter presses.

Luberetskaya aeration station (LbSA), Moscow. More than 40% of wastewater in Moscow and large cities of the Moscow region is treated at the Luberetskaya aeration station (LbSA), located in the village of Nekrasovka, Moscow region (Fig. 19.5).

LbSA was built in the pre-war years. The technological process of cleaning consisted in the mechanical treatment of wastewater and subsequent treatment in the fields of irrigation. In 1959, by decision of the government, construction of an aeration station began on the site of the Lyubertsy irrigation fields.

Rice. 19.5. The plan of the treatment facilities of the Luberetskaya and Novoluberetskaya aeration stations:
1 – wastewater supply to LbSA; 2 – wastewater supply to NLbSA; 3 - LbSA; 4 - NLbSA; 5 – facilities for sludge treatment; b - releases of treated wastewater

The technological scheme of wastewater treatment at the LbSA practically does not differ from the adopted scheme at the KSA and includes the following facilities: grids; sand traps; primary settling tanks with preaerators; aeration tanks-displacers; secondary clarifiers; sludge treatment and wastewater disinfection facilities (Fig. 19.6).

In contrast to the structures of the KSA, most of which were built of monolithic reinforced concrete, prefabricated reinforced concrete structures were widely used at the LbSA.

After the construction and commissioning in 1984 of the first block, and subsequently the second block of the treatment facilities of the Novoluberetskaya aeration station (NLbSA), the design capacity of the LbSA is 3.125 million m3 / day. The technological scheme of wastewater treatment and sludge treatment at LbSA is practically no different from the classical scheme adopted at KSA.

However, in recent years, a lot of work has been carried out at the Lyubertsy station to modernize and reconstruct wastewater treatment facilities.

New foreign and domestic small-gauge mechanized gratings (4-6 mm) were installed at the station, as well as the modernization of existing mechanized gratings was carried out according to the technology developed at the Moscow State Enterprise "Mosvodokanal" with a decrease in the size of the ditches to 4-5 mm.

Rice. 19.6. Technological scheme of wastewater treatment of the Luberetskaya aeration station:
1 - waste water; 2 - gratings; 3 - sand traps; 4 - preaerators; 5 - primary settling tanks; 6 - air; 7 - aeration tanks; 8 - secondary settling tanks; 9 – sludge thickeners; 10 - filter presses; 11 – dehydrated sludge storage areas; 12 - reagent facilities; 13 – digested sludge compactors before filter presses; 14 – sludge preparation unit; 15 – digesters; 16 - sand bunker; 17 - sand classifier; 18 - hydrocyclone; 19 - gas holder; 20 - boiler room; 21 - hydraulic presses for waste dewatering; 22 - emergency release

Of greatest interest is the technological scheme of block II of the NLbSa, which is a modern single-silt scheme of nit-ri-denitrification with two stages of nitrification. Along with the deep oxidation of carbon-containing organic substances, a deeper process of nitrogen oxidation of ammonium salts occurs with the formation of nitrates and a decrease in phosphates. The introduction of this technology makes it possible in the near future to obtain purified wastewater at the Lyubertsy aeration station, which would meet modern regulatory requirements for discharge into fishery water bodies (Fig. 19.7). For the first time, about 1 million m3/day of wastewater at LbSA is subjected to deep biological treatment with the removal of nutrients from treated wastewater.

Almost all raw sludge from primary settling tanks, before fermentation in digesters, undergoes preliminary processing on grates. The main technological processes for the treatment of sewage sludge at LbSA are: gravity compaction of excess activated sludge and wet sludge; thermophilic fermentation; washing and compaction of digested sludge; polymer conditioning; mechanical neutralization; deposit; natural drying (emergency silt pads).

Rice. 19.7. Technological scheme of wastewater treatment at LbSA according to the single-silt scheme of nitrification-denitrification:
1 - initial waste water; 2 – primary settler; 3 - clarified waste water; 4 - aerotank-denitrifier; 5 - air; 6 - secondary sump; 7 - treated waste water; 8 - recirculating activated sludge; 9 - raw sediment

For sludge dehydration, new frame filter-presses were installed, which make it possible to obtain a cake with a moisture content of 70-75%.

Central aeration station, St. Petersburg. Treatment facilities of the Central aeration station in St. Petersburg are located at the mouth of the river. Neva on the artificially reclaimed Bely Island. The station was put into operation in 1978; the design capacity of 1.5 million m3 per day was reached in 1985. The built-up area is 57 hectares.

The central aeration station of St. Petersburg receives and processes about 60% of domestic and 40% of industrial wastewater in the city. St. Petersburg is the largest city in the Baltic Sea basin, which places a special responsibility for ensuring its environmental safety.

The technological scheme of wastewater treatment and sludge treatment of the Central aeration station in St. Petersburg is shown in fig. 19.8.

The maximum flow rate of wastewater pumped by the pumping station in dry weather is 20 m3/s and in rainy weather - 30 m/s. Wastewater coming from the inlet collector of the city drainage network is pumped into the mechanical treatment inlet chamber.

The structure of mechanical treatment facilities includes: a receiving chamber, a grate building, primary settling tanks with grease collectors. Initially, wastewater is treated on 14 mechanized rake and stepped screens. After the screens, the wastewater enters the sand traps (12 pcs.) and then through the distribution channel is discharged to three groups of primary sedimentation tanks. Primary settling tanks of radial type, in the amount of 12 pieces. The diameter of each sump is 54 m at a depth of 5 m.

Rice. 19.8. Technological scheme of wastewater treatment and sludge treatment of the Central Station of St. Petersburg:
1 - sewage from the city; 2 - main pumping station; 3 - supply channel; 4 - mechanized gratings; 5 - sand traps; 6 - garbage; 7 - sand; 8 - sand; sites; 9 - primary settling tanks; 10 – raw sediment reservoir; 11 - aeration tanks; 12 - air; 13 - superchargers; 14 - return activated sludge; 15 - sludge pumping station; 16 - secondary settling tanks; 17 - release chamber; 18 - Neva river; 19 - activated sludge; 20 - sludge thickeners; 21 - receiving tank;
22 - centrifuges; 23 – cake for combustion; 24 - sludge incineration; 25 - furnace; 26 - ash; 27 - flocculant; 28 - drain water of sludge thickeners; 29 - water; 30 - solution
flocculant; 31 - centrifuge

The structure of biological treatment facilities includes aerotanks, radial settling tanks and the main machine building, which includes a block of blowers and sludge pumps. Aerotanks consist of two groups, each of which is six parallel three-corridor aerotanks 192 m long with a common upper and lower channels, the width and depth of the corridors are 8 and 5.5 m, respectively. Air is supplied to the aerotanks through fine-bubble aerators. The regeneration of activated sludge is 33%, while the return activated sludge from the secondary settling tanks is fed into one of the corridors of the aeration tank, which serves as a regenerator.

From the aerotanks, purified water is sent to 12 secondary settling tanks to separate activated sludge from biologically treated wastewater. Secondary settling tanks, as well as primary ones, are of a radial type with a diameter of 54 m and a settling zone depth of 5 m. From the secondary settling tanks, activated sludge enters the sludge pumping station under hydrostatic pressure. After the secondary settling tanks, the purified water is discharged into the river through the outlet chamber. Neva.

In the shop for mechanical sludge dewatering, raw sludge from primary settling tanks and compacted activated sludge from secondary settling tanks are processed. The main equipment of this workshop is ten centrifuges equipped with systems for preheating a mixture of raw sludge and activated sludge. To increase the degree of moisture transfer of the mixture, a flocculant solution is fed into the centrifuges. After processing in centrifuges, the moisture content of the cake reaches 76.5%.

In the sludge incineration shop, 4 fluidized bed furnaces (French company OTV) are installed.

A distinctive feature of these treatment facilities is that there is no pre-digestion in digesters in the sludge treatment cycle. Dehydration of the mixture of sediments and excess activated sludge occurs directly in the centrifuges. The combination of centrifuges and incineration of compacted sludge dramatically reduces the volume of the final ash product. Compared to conventional mechanical sludge treatment, the resulting ash is 10 times less than dehydrated cake. Using the method of burning a mixture of sludge and excess activated sludge in fluidized bed furnaces guarantees sanitary safety.

Aeration station, Nizhny Novgorod. The Nizhny Novgorod aeration station is a complex of facilities designed for the complete biological treatment of domestic and industrial wastewater in Nizhny Novgorod and the city of Bor. The following structures are included in the technological scheme: mechanical treatment unit - gratings, sand traps, primary settling tanks; biological treatment unit - aerotanks and secondary settling tanks; post-treatment; sludge treatment facilities (Figure 19.9).

Rice. 19.9. Technological scheme of wastewater treatment at the Nizhny Novgorod aeration station:
1 - wastewater receiving chamber; 2 - gratings; 3 - sand traps; 4 - sand platforms; 5 - primary settling tanks; 6 - aeration tanks; 7 - secondary settling tanks; 8 - pumping station for excess activated sludge; 9 – airlift chamber; 10 - biological ponds; 11 - contact reservoirs; 12 - release in the river. Volga; 13 – sludge thickeners; 14 – raw sludge pumping station (from primary settling tanks); 75 - digesters; 16 - sludge pumping station; 17 - flocculant; 18 - filter press; 19 - silt pads

The design capacity of the facilities is 1.2 million m3/day. The building has 4 mechanized gratings with a capacity of 400 thousand m3/day each. Waste from the grates is moved by means of conveyors, dumped into bunkers, chlorinated and taken to the landfill for composting.

Sand traps include two blocks: the first consists of 7 horizontal aerated sand traps with a capacity of 600 m3/h each, the second - of 2 horizontal slotted sand traps with a capacity of 600 m3/h each.

The station has 8 primary radial settling tanks with a diameter of 54 m. To remove floating impurities, the settling tanks are equipped with grease collectors.
4-corridor aeration tanks-mixers are used as biological treatment facilities. The dispersed inlet of wastewater into the aerotanks allows changing the volume of regenerators from 25 to 50%, ensuring good mixing of incoming water with activated sludge and uniform oxygen consumption along the entire length of the corridors. The length of each aeration tank is 120 m, the total width is 36 m, and the depth is 5.2 m.

The design of the secondary settling tanks and their dimensions are similar to the primary ones; in total, 10 secondary settling tanks were built at the station.

After the secondary settling tanks, the water is sent for post-treatment to two biological ponds with natural aeration. Biological ponds are built on a natural foundation and lined with earthen dams; the water surface area of ​​each pond is 20 ha. The residence time in biological ponds is 18-20 hours.

After bioponds, treated wastewater is disinfected in contact tanks using chlorine.

Purified and disinfected water through the Parshall trays enters the drainage canals and, after saturation with oxygen in the spillway overflow device, enters the river. Volga.

A mixture of raw sludge from primary settling tanks and compacted excess activated sludge is sent to digesters. Thermophilic mode is maintained in the digesters.

The digested sludge is partly fed to sludge beds and partly to a belt filter press.