Stairs. Entry group. Materials. Doors. Locks. Design

Today we will once again talk about a topic close to each of us, without exception.

Most people, when they press the toilet button, don't think about what happens to what they flush. It leaked and flowed, that's business. In a large city like Moscow, no less than four million cubic meters of wastewater flow into the sewer system every day. This is approximately the same amount of water flowing in the Moscow River in a day opposite the Kremlin. All this huge volume of wastewater needs to be purified and this is a very difficult task.

Moscow has two largest wastewater treatment plants of approximately the same size. Each of them purifies half of what Moscow “produces.” I have already spoken in detail about the Kuryanovskaya station. Today I will talk about the Lyubertsy station - we will again go over the main stages of water purification, but we will also touch on one very important topic - how treatment stations fight unpleasant odors using low-temperature plasma and waste from the perfume industry, and why this problem has become more relevant than ever .

First, a little history. For the first time, sewerage “came” to the area of ​​modern Lyubertsy at the beginning of the twentieth century. Then the Lyubertsy irrigation fields were created, in which wastewater, still using old technology, seeped through the ground and was thereby purified. Over time, this technology became unacceptable for the ever-increasing amount of wastewater and in 1963 a new treatment station was built - Lyuberetskaya. A little later, another station was built - Novolubertskaya, which actually borders the first one and uses part of its infrastructure. In fact, now it is one large cleaning station, but consisting of two parts - old and new.

Let's look at the map - on the left, in the west - the old part of the station, on the right, in the east - the new one:

The station area is huge, about two kilometers in a straight line from corner to corner.

As you might guess, there is a smell coming from the station. Previously, few people worried about it, but now this problem has become relevant for two main reasons:

1) When the station was built, in the 60s, practically no one lived around it. Nearby there was a small village where the station workers themselves lived. At that time this area was far, far from Moscow. Now there is very active construction going on. The station is virtually surrounded on all sides by new buildings and there will be even more of them. New houses are even being built on the station’s former sludge sites (fields to which sludge left over from wastewater treatment was transported). As a result, residents of nearby houses are forced to periodically sniff “sewer” odors, and of course they constantly complain.

2) Sewage water has become more concentrated than before, in Soviet times. This happened due to the fact that the volume of water used has recently decreased significantly, while people have not gone to the toilet less, but on the contrary, the population has grown. There are quite a few reasons why the amount of “diluting” water has become much smaller:
a) use of meters - water has become more economical;
b) the use of more modern plumbing - it is increasingly rare to see a running faucet or toilet;
c) use of more economical household appliances - washing machines, dishwashers, etc.;
d) closure of a huge number of industrial enterprises that consumed a lot of water - AZLK, ZIL, Serp and Molot (partially), etc.
As a result, if the station during construction was designed for a volume of 800 liters of water per person per day, now this figure is actually no more than 200. An increase in concentration and a decrease in flow led to a number of side effects - sediment began to be deposited in sewer pipes designed for a higher flow, leading to to unpleasant odors. The station itself began to smell more.

To combat the smell, Mosvodokanal, which manages the treatment facilities, is carrying out a phased reconstruction of the facilities, using several different methods of getting rid of odors, which will be discussed below.

Let's go in order, or rather, in the flow of water. Wastewater from Moscow enters the station through the Lyubertsy sewer canal, which is a huge underground collector filled with wastewater. The canal is gravity-flowing and runs at a very shallow depth almost throughout its entire length, and sometimes even above the ground. Its scale can be appreciated from the roof of the administrative building of the wastewater treatment plant:

The width of the canal is about 15 meters (divided into three parts), the height is 3 meters.

At the station, the channel enters the so-called receiving chamber, from where it is divided into two streams - part goes to the old part of the station, part to the new one. The receiving chamber looks like this:

The channel itself comes from the right-back, and the flow, divided into two parts, leaves through the green channels in the background, each of which can be blocked by a so-called gate - a special shutter (dark structures in the photo). Here you can notice the first innovation to combat odors. The receiving chamber is completely covered with sheets of metal. Previously, it looked like a “swimming pool” filled with fecal water, but now it is not visible; naturally, the solid metal coating almost completely blocks the smell.

For technological purposes, only a very small hatch was left, by lifting it you can enjoy the whole bouquet of smells.

These huge gates allow you to block the channels coming from the receiving chamber if necessary.

There are two channels from the receiving chamber. They, too, were open quite recently, but now they are completely covered with a metal ceiling.

Gases released from wastewater accumulate under the ceiling. These are mainly methane and hydrogen sulfide - both gases are explosive at high concentrations, so the space under the ceiling must be ventilated, but here the following problem arises - if you just install a fan, then the whole point of the ceiling will simply disappear - the smell will get outside. Therefore, to solve the problem, MKB "Horizon" developed and manufactured a special installation for air purification. The installation is located in a separate booth and a ventilation pipe from the duct goes to it.

This installation is experimental, to test the technology. In the near future, such installations will begin to be installed en masse at treatment plants and at sewerage pumping stations, of which there are more than 150 in Moscow and from which unpleasant odors also emanate. On the right in the photo is one of the developers and testers of the installation, Alexander Pozinovsky.

The operating principle of the installation is as follows:
Polluted air is supplied into four vertical stainless steel pipes from below. These same pipes contain electrodes, to which high voltage (tens of thousands of volts) is applied several hundred times per second, resulting in discharges and low-temperature plasma. When interacting with it, most smelling gases turn into a liquid state and settle on the walls of the pipes. A thin layer of water constantly flows down the walls of the pipes, with which these substances mix. The water circulates in a circle, the water tank is the blue container on the right, below in the photo. Purified air comes out of stainless steel pipes from above and is simply released into the atmosphere.

For patriots - the installation was completely developed and created in Russia, with the exception of the power stabilizer (bottom in the cabinet in the photo). High voltage part of the installation:

Since the installation is experimental, it contains additional measuring equipment - a gas analyzer and an oscilloscope.

The oscilloscope shows the voltage across the capacitors. During each discharge, the capacitors are discharged and the process of their charging is clearly visible on the oscillogram.

There are two tubes going to the gas analyzer - one takes in air before installation, the other after. In addition, there is a faucet that allows you to select the tube that connects to the gas analyzer sensor. Alexander first shows us the “dirty” air. Hydrogen sulfide content - 10.3 mg/m3. After switching the tap, the content drops to almost zero: 0.0-0.1.

Next, the supply channel abuts a special distribution chamber (also covered with metal), where the flow is divided into 12 parts and goes further into the so-called grid building, which is visible in the background. There, wastewater undergoes the very first stage of purification - removal of large debris. As you might guess from the name, it is passed through special gratings with a cell size of about 5-6 mm.

Each of the channels is also blocked by a separate gate. Generally speaking, there are a huge number of them at the station - sticking out here and there

After cleaning from large debris, the water enters sand traps, which, as again it is not difficult to guess from the name, are designed to remove small solid particles. The principle of operation of sand traps is quite simple - essentially it is a long rectangular tank in which water moves at a certain speed, as a result the sand simply has time to settle. Air is also supplied there, which facilitates the process. Sand is removed from below using special mechanisms.

As often happens in technology, the idea is simple, but the execution is complex. So here too - visually this is the most sophisticated design on the way to water purification.

Sand traps are favored by seagulls. In general, there were a lot of seagulls at the Lyubertsy station, but it was in the sand traps that there were the most of them.

I enlarged the photo at home and laughed at the sight of them - funny birds. They are called black-headed gulls. No, they don’t have a dark head because they constantly dip it where it shouldn’t, it’s just a design feature
Soon, however, they will have a hard time - many open water surfaces at the station will be covered.

Let's get back to technology. The photo shows the bottom of the sand trap (not working at the moment). This is where the sand settles and is removed from there.

After the sand traps, the water again flows into the common channel.

Here you can see what all the channels at the station looked like before they began to be covered. This channel is closing right now.

The frame is made of stainless steel, like most metal structures in the sewer system. The fact is that the sewer system has a very aggressive environment - water full of all sorts of substances, 100% humidity, gases that promote corrosion. Ordinary iron very quickly turns to dust in such conditions.

The work is being carried out directly above the active channel - since this is one of the two main channels, it cannot be turned off (Muscovites will not wait :)).

In the photo there is a small level difference, about 50 centimeters. The bottom in this place is made of a special shape to dampen the horizontal velocity of the water. The result is very active seething.

After sand traps, water flows to primary settling tanks. In the photo - in the foreground there is a chamber into which water flows, from which it flows into the central part of the sump in the background.

A classic sump looks like this:

And without water - like this:

Dirty water comes from a hole in the center of the sump and enters the general volume. In the settling tank itself, the suspension contained in the dirty water gradually settles to the bottom, along which a sludge scraper, mounted on a truss rotating in a circle, constantly moves. The scraper scrapes the sediment into a special ring tray, and from it, in turn, it falls into a round pit, from where it is pumped out through a pipe by special pumps. Excess water flows into a channel laid around the sump and from there into the pipe.

Primary settling tanks are another source of unpleasant odors at the plant, because... they contain actually dirty (purified only from solid impurities) sewage water. In order to get rid of the smell, Moskvodokanal decided to cover the sedimentation tanks, but a big problem arose. The diameter of the sump is 54 meters (!). Photo with a person for scale:

Moreover, if you make a roof, then it must, firstly, withstand snow loads in winter, and secondly, have only one support in the center - supports cannot be made above the sump itself, because the farm is constantly rotating there. As a result, an elegant solution was made - to make the ceiling floating.

The ceiling is assembled from floating stainless steel blocks. Moreover, the outer ring of blocks is fixed motionless, and the inner part rotates floating, together with the truss.

This decision turned out to be very successful, because... firstly, the problem with snow load disappears, and secondly, there is no volume of air that would have to be ventilated and additionally purified.

According to Mosvodokanal, this design reduced emissions of odorous gases by 97%.

This settling tank was the first and experimental one where this technology was tested. The experiment was considered successful and now other settling tanks at the Kuryanovskaya station are already covered in a similar way. Over time, all primary settling tanks will be covered in a similar manner.

However, the reconstruction process is lengthy - it is impossible to turn off the entire station at once; the settling tanks can only be reconstructed one after another, turning off one by one. Yes, and a lot of money is needed. Therefore, while not all sedimentation tanks are covered, a third method of combating odors is used - spraying neutralizing substances.

Special sprayers were installed around the primary settling tanks, which create a cloud of substances that neutralize odors. The substances themselves smell, not very pleasant or unpleasant, but quite specific, however, their task is not to mask the smell, but to neutralize it. Unfortunately, I don’t remember the specific substances that are used, but as they said at the station, these are waste products from the French perfume industry.

For spraying, special nozzles are used that create particles with a diameter of 5-10 microns. The pressure in the pipes, if I'm not mistaken, is 6-8 atmospheres.

After the primary settling tanks, the water enters aeration tanks - long concrete tanks. They supply a huge amount of air through pipes and also contain activated sludge - the basis of the entire biological method. Activated sludge processes “waste” and multiplies quickly. The process is similar to what happens in nature in reservoirs, but it proceeds many times faster due to warm water, a large amount of air and silt.

The air is supplied from the main machine room, in which turbo blowers are installed. Three turrets above the building are air intakes. The air supply process requires a huge amount of electricity, and stopping the air supply leads to catastrophic consequences, because activated sludge dies very quickly, and its restoration can take months (!).

Aerotanks, oddly enough, do not particularly emit strong unpleasant odors, so there are no plans to cover them.

This photo shows how dirty water enters the aeration tank (dark) and mixes with activated sludge (brown).

Some of the structures are currently shut down and mothballed, for reasons that I wrote about at the beginning of the post - a decrease in water flow in recent years.

After the aeration tanks, the water enters secondary settling tanks. Structurally, they completely repeat the primary ones. Their purpose is to separate activated sludge from already purified water.

Preserved secondary settling tanks.

Secondary settling tanks do not smell - in fact, the water here is already clean.

The water collected in the sump ring tray flows into the pipe. Part of the water undergoes additional UV disinfection and is discharged into the Pekhorka River, while part of the water goes through an underground canal to the Moscow River.

The settled activated sludge is used to produce methane, which is then stored in semi-underground reservoirs - methane tanks and used at its own thermal power plant.

The spent sludge is sent to sludge sites in the Moscow region, where it is further dewatered and either buried or burned.

Every Russian city has a system of special structures that are designed to treat wastewater containing a wide variety of mineral and organic compounds to a state in which they can be discharged into the environment without harming the environment. Modern wastewater treatment plants for the city, which are developed and manufactured by the Flotenk company, are quite technically complex complexes, consisting of several separate blocks, each of which performs a strictly defined function.

To order and calculate treatment facilities, send a request to E-mail: or call toll-free 8 800 700-48-87 Or fill out the questionnaire:

KNS:

Advantages of municipal wastewater treatment plants produced by Flotenk

The development, production and installation of treatment facilities is one of the main specializations of the Flotenk company. Its systems, as practice shows, have many advantages over similar products produced by many other domestic and foreign companies. Among them, it is worth noting the high efficiency of urban wastewater treatment plants from Flotenk, which is due to a carefully calculated, well-thought-out and perfectly implemented design. In addition, they are characterized by increased reliability and long service life, since their main components are made of fiberglass that is durable and resistant to various types of adverse effects.

How is city wastewater treated?

The city's wastewater is treated in stages. The wastewater entering the sewage treatment plant through the sewer system first enters a unit where the mechanical impurities contained in it are separated. After this, the wastewater goes to biological treatment, during which most of the organic compounds, as well as nitrogen compounds, are removed from it. In the next, third block, wastewater is further purified, as well as disinfected either with chlorine or treated with ultraviolet radiation. Once in the last block, municipal wastewater settles and produces sediment, which is subject to further processing.

Treatment facilities, which are developed and manufactured by the Flotenk company for cities, have mechanical wastewater treatment units, in which specialized meshes with very small cells are installed to remove fairly large waste. In addition, these blocks are also equipped with sand traps. They are containers of sufficiently large volume, in which sand settles out due to a sharp decrease in the speed of wastewater flow under the influence of gravity. These tanks are manufactured at Flotenk's own production facilities, have several components and are assembled directly at the installation site.

Biological treatment of municipal wastewater is also carried out in special tanks called aeration tanks. In them, a component such as activated sludge is added to the wastewater, which contains microorganisms that decompose various substances of organic origin. In order for the biological treatment process to proceed faster, air is pumped into the aeration tanks using compressors.

Secondary settling tanks, into which wastewater is sent after biological treatment, are necessary in order to separate the activated sludge contained in them, which is then sent back to aeration tanks. In addition, wastewater is disinfected in these containers, which, at the end of this process, is sent to discharge points (most often these are open reservoirs).

Modern ecology, alas, leaves much to be desired - all pollution of biological, chemical, mechanical, organic origin sooner or later penetrates the soil and water bodies. The supply of “healthy” clean water is becoming smaller every year, in which the constant use of household chemicals and the active development of production play a certain role. The wastewater contains a huge amount of toxic impurities, the removal of which must be complex and multi-level.

Different methods are used for water purification - the optimal choice is made taking into account the type of contaminants, desired results, and available capabilities.

The simplest option is . It is aimed at removing insoluble components that pollute water - these are fats and solid inclusions. First, the wastewater passes through grates, then sieves and ends up in settling tanks. Small components are deposited in sand traps, petroleum products are deposited in gasoline and oil traps, and in grease traps.

A more advanced cleaning method is membrane. It guarantees the most precise removal of contaminants. involves the use of appropriate organisms that oxidize organic inclusions. The basis of the technique is the natural purification of reservoirs and rivers at the expense of their population with beneficial microflora that removes phosphorus, nitrogen and other unnecessary impurities. The biological cleaning method can be anaerobic or aerobic. Aerobic requires bacteria, the life of which is impossible without oxygen - biofilters and aeration tanks filled with activated sludge are installed. The degree of purification and efficiency is higher than for a biofilter for wastewater treatment. Anaerobic purification does not require access to oxygen.

It involves the use of electrolysis, coagulation, as well as the precipitation of phosphorus with metal salts. Disinfection is carried out by ultraviolet irradiation, chlorine treatment, and ozonation. Disinfection with ultraviolet irradiation is a much safer and more effective method than chlorination, since it is carried out without the formation of toxic substances. UV radiation is harmful to all organisms, therefore it destroys all dangerous pathogens. Chlorination is based on the ability of active chlorine to act on microorganisms and destroy them. A significant drawback of the method is the formation of chlorine-containing toxins, carcinogenic substances.

Ozonation involves the disinfection of wastewater with ozone. Ozone is a gas with a triatomic molecular structure, a strong oxidizing agent that kills bacteria. The technique is expensive and is used to release ketones and aldehydes.

Thermal recovery is optimal for treating process wastewater when other methods are not effective. At modern treatment complexes, wastewater undergoes multi-component step-by-step treatment.

Wastewater treatment facilities: requirements for treatment systems, types of treatment facilities

Primary mechanical treatment is always recommended, followed by biological treatment, additional treatment and disinfection of wastewater.

• For mechanical cleaning, rods, gratings, sand traps, homogenizers, settling tanks, septic tanks, hydrocyclones, centrifuges, flotation units, and degassers are used.
• A sludge pump is a special device for purifying water with activated sludge. Other components of the biotreatment system are biocoagulators, suction pumps, aeration tanks, filters, secondary settling tanks, sludge separators, filtration fields, and biological ponds.
• As part of post-treatment, neutralization and filtration of wastewater is used.
• Disinfection and disinfection are carried out with chlorine and electrolysis.

What is meant by wastewater?

Wastewater is water masses contaminated with industrial waste, for the removal of which from the areas of settlements and industrial enterprises appropriate sewer systems are used. Runoff also includes water formed as a result of precipitation. Organic inclusions begin to rot en masse, which causes deterioration in the condition of water bodies and air, and leads to the massive spread of bacterial flora. For this reason, important tasks of water treatment are the organization of drainage, wastewater treatment, and the prevention of active harm to the environment and human health.

Indicators of the degree of purification

The level of wastewater pollution must be calculated taking into account the concentration of impurities, expressed as mass per unit volume (g/m3 or mg/l). Domestic wastewater is a uniform formula in terms of composition; the concentration of pollutants depends on the volume of water mass consumed, as well as consumption standards.

Degrees and types of pollution of domestic wastewater:

• insoluble, large suspensions are formed in them, one particle cannot be more than 0.1 mm in diameter;
• suspensions, emulsions, foams, the particle sizes of which can range from 0.1 microns to 0.1 mm;
• colloids – particle sizes in the range of 1 nm-0.1 microns;
• soluble with molecularly dispersed particles, the size of which is no more than 1 nm.

Pollutants are also divided into organic, mineral, and biological. Mineral - these are slags, clay, sand, salts, alkalis, acids, etc. Organic - plant or animal, namely the remains of plants, vegetables, fruits, vegetable oils, paper, feces, tissue particles, gluten. Biological impurities – microorganisms, fungi, bacteria, algae.

Approximate proportions of pollutants in household wastewater:

• mineral – 42%;
• organic – 58%;
• suspended matter – 20%;
• colloidal impurities – 10%;
• dissolved substances – 50%.

The composition of industrial wastewater and the level of its pollution are indicators that vary depending on the nature of a particular production and the conditions for using wastewater in the technological process.

Atmospheric runoff is affected by climate, terrain, the nature of buildings, and the type of road surface.

The operating principle of cleaning systems, rules for their installation and maintenance. Requirements for cleaning systems

Water treatment facilities must provide specified epidemic and radiation indicators and have a balanced chemical composition. After entering water treatment facilities, water undergoes complex biological and mechanical purification. To remove debris, wastewater is passed through a screen with rods. Cleaning is automatic, and operators also check the quality of contaminant removal every hour. There are new self-cleaning grilles, but they are more expensive.

For clarification, clarifiers, filters, and settling tanks are used. In settling tanks and clarifiers, water moves very slowly, as a result of which suspended particles begin to fall out to form sediment. From the sand traps, the liquid is directed to the primary settling tanks - mineral impurities also settle here, and light suspensions rise to the surface. The sediment is formed at the bottom; it is raked into pits using a truss with a scraper. The floating substances are sent to the grease trap, from there to the well and rolled away.

The clarified water masses are sent to patches, then to aeration tanks. At this point, the mechanical removal of impurities can be considered complete - the turn of the biological one comes. The aeration tanks include 4 corridors, into the first one silt is supplied through tubes, and the water acquires a brown tint, continuing to be actively saturated with oxygen. The sludge contains microorganisms that also purify the water. The water is then sent to a secondary settling tank where it is separated from the sludge. The sludge goes through pipes into wells, from where pumps pump it into aeration tanks. Water is poured into contact-type tanks, where it was previously chlorinated, but now in transit.

It turns out that during primary purification, water is simply poured into a vessel, infused and drained. But this is precisely what makes it possible to remove most of the organic impurities at minimal financial cost. After water leaves the primary settling tanks, it goes to other water treatment facilities. Secondary purification involves the removal of organic residues. This is a biological stage. The main types of systems are activated sludge and trickling biological filters.

Operating principle of the wastewater treatment complex (general characteristics of water treatment facilities)

Through three collectors from the city, dirty water is supplied to mechanical screens ( the optimal gap is 16 mm), passes through them, the largest contaminant particles are deposited on the grid. Cleaning is automatic. Mineral impurities, which have a significant mass compared to water, follow through the hydraulic elevators, after which the hydraulic elevators are rolled back to the launch pads.

After leaving the sand traps, the water enters the primary settling tank (there are 4 in total). The floating substances are fed into the grease trap, from the grease trap into the well and rolled away. All operating principles described in this section are valid for different types of treatment systems, but may have certain variations taking into account the characteristics of a particular complex.

Important: types of wastewater

To choose the right treatment system, be sure to consider the type of wastewater. Available options:

1. Household fecal or household waste - they are removed from toilets, bathrooms, kitchens, baths, canteens, hospitals.
2. Industrial, production, involved in the performance of various technological processes such as washing of raw materials, products, cooling of equipment, pumped out during mining.
3. Atmospheric wastewater, including rainwater, meltwater, and those remaining after watering streets and green plantings. The main pollutants are mineral.

The waste disposal system is an integral part of any city. It is this that ensures the residential area’s normal functioning and compliance with sanitary standards in urban environments. Wastewater that enters city treatment plants contains a wide variety of organic and mineral compounds that can cause enormous damage to the environment if not disposed of properly.

The treatment facility includes four special treatment units. To remove sand and large debris, the first mechanical cleaning unit is used (as a rule, large waste that is screened out at the first stage is much easier to dispose of). Then, in the next step, a complete biological treatment takes place in another unit, removing nitrogen compounds and as much organic compounds as possible. After this, in the third block, further waste treatment occurs - they are cleaned at a deeper level and disinfected. And in the fourth block, the process of processing the remaining sediments takes place. Next, in order to better understand the essence of the process, we will look in more detail at how exactly this happens.

Thanks to mechanical, physico-chemical and biological treatment, sediment is separated from polluted waters, which is then screened out in sedimentation tanks specially designed for this purpose, and then, when activated sludge is formed, it goes into secondary sedimentation tanks. Activated sludge is a very viscous substance that contains various protozoa, bacteria and flakes formed from a variety of chemical compounds. The sludge screened out by settling tanks has almost one hundred percent moisture, but it is incredibly difficult to remove excess moisture, since the substances are highly interconnected and have low moisture yield. With the help of special sludge compactors, the sludge is processed and compacted by two to three percent.

Unfortunately, the resulting substance cannot be used as a fertilizer, because, despite the fact that potassium, nitrogen and phosphorus are present in activated sludge, they are poorly absorbed by plants, and in addition to microorganisms dangerous to humans, it also contains helminth eggs. Next, we will consider in more detail the types and principles of operation of structures for treating urban wastewater. In sewage treatment plants, specialized meshes or strainers with cells no larger than two millimeters are used for mechanical water purification to remove sand and large debris. For finer sand, sand traps are used. This is a completely mechanized procedure. The structures for mechanical cleaning look like eleven meters high and up to twenty-two meters in diameter, tanks created on the basis of oil. They are closed with lids on top and equipped with a ventilation system. Such structures require minimal amounts of lighting and heating, since the largest volume in it is occupied by wastewater, which does not require raising the temperature (it should be within about twelve to sixteen degrees).

Biological treatment involves complex chemical processes that promote the oxidation and breakdown of liquids, using pumps that transport contaminated water from one area to another. In addition, the system is equipped with an anaerobic stabilizer, which contains a sludge thickener. Currently, various types of treatment facilities are used within the city, local ones, which are designed for private and country houses, and industrial ones, necessary to purify water from industrial waste.

Particularly strict compliance with environmental standards applies to enterprises that produce any type of product (especially those whose activities leave waste heavy metals and chemical compounds). Therefore, only after preliminary cleaning, waste from industrial enterprises associated with the production of chemical, light, oil refining and other industries can be discharged into the central sewerage system or reused. What processes must be carried out when treating water from an industrial enterprise is determined by the industry sector. The site that is used for the construction of large ones must be selected taking into account convenient access for vehicles, the presence of a reservoir into which it is planned to discharge already treated water and the features of the terrain (in particular, the composition of the soil and the groundwater level).

Since the treatment station is a structure that can have a direct impact on the environment, it must comply with strictly defined standards and norms. The perimeter of a wastewater treatment plant must always be fenced, and only city-made tanks are used within the station itself. In addition, treatment plants are subject to strict control by the Ministry of Ecology and Bioresources, which inspects all structures at the station.

And today I will tell you about sewerage and water disposal in a modern metropolis. Thanks to a recent trip to the South-Western wastewater treatment plant in St. Petersburg, I and several of my companions instantly turned from simple bloggers into world-class experts in water collection and purification technologies, and now we will be happy to show and tell you how it all works!

A pipe from which a powerful stream of rating social capital flows the contents of the sewer collector

Aeration tanks YuZOS

So, let's begin. Water diluted with soap and shampoo, street dirt, industrial waste, food leftovers, as well as the results of digestion of this food (all this ends up in the sewer system, and then in treatment plants) has a long and thorny path to go through before it returns to the water. Neva or Gulf of Finland. This path begins either in the drain grate, if this happens on the street, or in the “fan” pipe, if we are talking about apartments and offices. From not very big ones (15 cm in diameter, everyone has probably seen them at home in the bathroom or toilet) sewer pipes, water mixed with waste enters larger communal pipes. Several houses (as well as street drains in the surrounding area) are combined into a local catchment, which, in turn, are combined into sewer areas and then into sewer basins. At each stage, the diameter of the sewage pipe increases, and in tunnel collectors it already reaches 4.7 m. Through such a hefty pipe, dirty water slowly (by gravity, no pumps) reaches the aeration stations. In St. Petersburg there are three large ones that completely cover the city, and several smaller ones in remote areas such as Repino, Pushkin or Kronstadt.

Yes, about the treatment facilities themselves. Some may have a completely reasonable question - “Why purify wastewater at all? The Bay and Neva will endure everything!” In general, this is how it used to be; until 1978, the wastewater was practically not treated in any way and immediately ended up in the bay. The bay processed them at the very least, coping, however, with the increasing flow of sewage every year worse and worse. Naturally, this state of affairs could not but affect the environment. Our Scandinavian neighbors suffered the most, but the surrounding areas of St. Petersburg also experienced a negative impact. And the prospect of a dam across the Finnish made us think that the waste of a city with a population of one million, instead of happily floating in the Baltic Sea, will now hang out between Kronstadt and (then still) Leningrad. In general, the prospects of eventually choking on sewage did not make anyone happy, and the city, represented by Vodokanal, gradually began to solve the problem of wastewater treatment. It can be considered almost completely resolved only in the last year - in the fall of 2013, the main sewer collector of the northern part of the city was launched, after which the amount of treated water reached 98.4 percent.

Let's look at the example of the South-Western Treatment Plants to see how cleaning occurs. Having reached the very bottom of the collector (the bottom is located on the territory of the treatment plant), the water rises to a height of almost 20 meters using powerful pumps. This is necessary so that dirty water goes through the stages of purification under the influence of gravity, with minimal involvement of pumping equipment.

The first stage of cleaning is the grates, on which large and not so large debris remains - all sorts of rags, dirty socks, drowned kittens, lost mobile phones and other wallets with documents. Most of what is collected goes straight to the landfill, but the most interesting finds remain in a makeshift museum.

Swimming pool with sewage. Exterior view

Swimming pool with sewage. Inside view

This room has grates to catch large debris.

Behind the cloudy plastic you can see what has been assembled by the bars. Paper and labels stand out

Brought by water

And the water moves on, the next step is sand traps. The task of this stage is to collect coarse impurities and sand - everything that passed by the grates. Before release from sand traps, chemicals are added to the water to remove phosphorus. Next, the water is sent to primary settling tanks, in which suspended and floating substances are separated.

Primary settling tanks complete the first stage of purification - mechanical and partially chemical. Filtered and settled water does not contain debris and mechanical impurities, but it is still full of not the most useful organic matter, and is also home to many microorganisms. You also need to get rid of all this, and start with organics...

The structure in the foreground moves slowly along the pool

Primary settling tanks. The water in the sewer has a temperature of about 15-16 degrees, steam is actively coming from it, since the ambient temperature is lower

The biological treatment process takes place in aeration tanks - these are huge bathtubs into which water is poured, air is pumped in and “activated sludge” is launched - a cocktail of simple microorganisms designed to digest exactly those chemical compounds that need to be gotten rid of. The air pumped into the tanks is needed to increase the activity of microorganisms; under such conditions, they almost completely “digest” the contents of the bathroom in five hours. Next, the biologically purified water is sent to secondary settling tanks, where activated sludge is separated from it. The sludge is again sent to the aeration tanks (except for the excess, which is burned), and the water goes to the last stage of purification - ultraviolet treatment.

Aero tanks. "Boiling" effect due to active air injection

Control room. You can see the entire station from above

Secondary settling tank. For some reason, the water in it really attracts birds.

At the South-Western Treatment Plants, subjective control of the quality of treatment is also carried out at this stage. It looks like this: purified and disinfected water is poured into a small aquarium in which several crayfish sit. Crayfish are very fastidious creatures; they react immediately to dirt in the water. Since people have not yet learned to distinguish the emotions of crustaceans, a more objective assessment is used - a cardiogram. If suddenly several (protection against false positives) crayfish experience severe stress, then something is wrong with the water, and you urgently need to figure out which of the purification stages failed.

But this is an abnormal situation, and in the usual order of things, clean water is sent to the Gulf of Finland. Yes, about cleanliness. Although crayfish exist in such water, and microbes and viruses have all been removed from it, it is still not recommended to drink it . However, the water fully complies with the environmental standards of HELCOM (the Convention for the Protection of the Baltic Sea from Pollution), which in recent years has already had a positive impact on the state of the Gulf of Finland.

Ominous green light disinfects water

Cancer detector. Attached to the shell is not an ordinary rope, but a cable through which data on the animal’s condition is transmitted.

Click-clack

I’ll say a few more words about the disposal of everything that is filtered from the water. Solid waste is transported to landfill sites, but everything else is burned at a plant located on the territory of the wastewater treatment plant. Dewatered sludge from the primary settling tanks and excess activated sludge from the secondary ones are sent to the furnace. Combustion occurs at a relatively high temperature (800 degrees) to minimize harmful substances in the exhaust. It is surprising that out of the total volume of the plant premises, stoves occupy only a small part, about 10%. The remaining 90% is given to a huge system of various filters that filter out all possible and impossible harmful substances. By the way, the plant has implemented a similar subjective “quality control” system. Only the detectors are no longer crayfish, but snails. But the principle of operation is generally the same - if the content of harmful substances at the outlet of the pipe is higher than permissible, the mollusk’s body will immediately react.

Furnaces

P waste heat boiler blower valves. The purpose is not entirely clear, but how impressive they look!

Snail. There is a tube above her head from which water is dripping. And next to it is another one, with an exhaust

P.S. One of the most popular questions asked about the announcement was “What’s with the smell? It stinks, right?” I was somewhat disappointed with the smell :) The untreated contents of the sewer (in the very first photo) have practically no smell. There is, of course, a smell in the station area, but it is very mild. The strongest smell (and this is already noticeable!) is the dewatered sludge from the primary settling tanks and the activated sludge - what goes into the stove. That’s why, by the way, they began to burn them, the landfills to which sludge had previously been dumped gave off a very unpleasant smell for the surrounding area...

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