How do municipal wastewater treatment plants work? Types and principle of operation of urban treatment facilities. Operation and maintenance

For a comfortable life in a private house with a kitchen, several bathrooms and showers, a reliable system for collecting, filtering and processing waste resulting from human activity is needed, which would not require frequent pumping and time-consuming for frequent maintenance. If the house does not have the ability to connect to the central sewer, then local treatment facilities become the way out. This article will discuss the principle of operation of an autonomous sewage system of a private house and what advantages and disadvantages such a system has.

The sewer system for a private house can be divided into three types:

septic tank;
local treatment facilities.

Cesspool this is the easiest type of sewer to install and maintain. It involves the discharge of wastewater into a sealed container in which they are stored and from which they are periodically pumped out by a sewage machine. For the construction of a cesspool, as a rule, reinforced concrete rings buried in the ground are used, and access to the pit is organized by installing a hatch. The disadvantages of such a system are the need for regular cleaning of the container, as well as the appearance of an unpleasant odor, which cannot be eliminated even by disinfection.

It is a large container, consisting of several cameras communicating with each other. In the first chamber, the waste goes through the stage of primary mechanical cleaning - settling, in which the solid parts settle to the bottom, and the water purified from these parts passes by gravity into the second chamber. Biological purification takes place here - anaerobic bacteria process organic compounds that are in suspension into sludge without oxygen, further purifying the water.

Since the process of water purification without access to oxygen is not very effective, the output water has a degree of purification of approximately 80%. Even for technical needs, such water is unsuitable. For further cleaning, the septic tank involves the use of either aeration fields.

The advantages of such sewerage are autonomy and independence. There is no need to supply electricity to the septic tank, and human intervention is limited to cleaning the system, depending on the intensity of use. But when filtering waste in such systems, methane is released, for the removal of which ventilation is installed with an output not lower than the level of the roofs of houses.

The third type is local treatment plant (VOC or local treatment facilities). Such an installation purifies wastewater with the highest quality with a purification rate of up to 98%. Let's talk in more detail about how autonomous sewage works.

The principle of operation of autonomous sewage

Local treatment facilities are a complex of tanks where wastewater passes through several stages of treatment. A fundamentally autonomous sewage system contains the functions of a septic tank, in which mechanical wastewater treatment takes place, and the functions of aerobic treatment, where aerobic bacteria effectively process a fine suspension into sludge, clarifying the drains as much as possible. Let us consider in detail the principle of operation of LOS.

At the first stage, runoff from the house enter the first chamber of the autonomous sewer, called the reception. The average volume of such a container is 3 cubic meters. Here, as in a septic tank, large particles are settled, as well as the separation of fatty particles with the help of special grease traps.

At the next stage, water flows by gravity into the next chamber, with a volume equal to half of the first chamber. This tank is called an aeration tank, since oxygen is saturated with wastewater here. This happens with the help of an air compressor, which through the hoses pumps oxygen-saturated air into the chamber from below, while mixing due to the many bubbles rising up.

Colonies of bacteria settle in the same chamber, which gradually convert the finely dispersed suspension into activated sludge, eating it and turning it into large enough flakes, which, due to their weight, can settle to the bottom. The high activity of such bacteria is due to the constant supply of oxygen to the aerotank.

All this mixture of liquid and activated sludge mixed in it gradually moves by gravity into the next tank - the secondary sedimentation tank, in which the sludge settles on a special cone-shaped trap, and then is pumped back to the aeration tank. Purified water, separated from sludge, enters the next stage of purification.

When the maximum amount of waste sludge accumulates in the aeration tank, the system automatically pumps it into a special sump, from which it is removed and used for household needs.

After the secondary sump, already sufficiently purified water enters the next tank, coming into contact with a chlorine-containing preparation. Here the final disinfection of wastewater and their post-treatment takes place. At this stage, the water is purified up to 98%, starting to meet sanitary standards.

Removal of treated water from an autonomous sewer can occur in several ways:

Overflowing into a special storage well, from where the water will be pumped out by a pump or used for household needs. This method is used when there is a high level of groundwater or when technical water is needed for watering the garden.
Overflow to where the water will go into the ground. This method is possible if there is sandy or loamy soil on the site. The advantage here is that there is no need to pump out wastewater.
Organization. This method is also used at a low level of groundwater. The advantage of aeration fields is the additional fertilization of the soil at the place of discharge of treated water.

Due to the intensive processing process, autonomous sewage has the smallest dimensions compared to conventional septic tanks, which indicates the convenience of its installation on the site. Purified water can be used for irrigation on the site without fear of any harmful substances entering the soil, and recycled sludge is a useful fertilizer that is used in the garden and vegetable garden, it can be scooped out on its own with buckets.

VOC is a closed installation in which cleaning is carried out inside the chambers and does not require direct human intervention. The filter elements and the grease trap are cleaned approximately once every 6 months, and a preventive visual inspection of the chambers is carried out once a month. Pumps may need to be replaced after several years of operation.

The main disadvantage of the station is the need for uninterrupted power supply. With a prolonged power outage, some filter elements may become unusable.

How to choose an autonomous sewer for your home

For a rational choice of the type of local treatment facilities, a number of factors must be taken into account: the condition and composition of the soil in which the sewage system will be installed, groundwater, the shape and size of the site, the number of people living in the house, is the dwelling seasonal or permanent.

The choice between a septic tank and a VOC will be justified if we calculate the most common situations:

Budget. If it is limited, then a septic tank should be installed. It is cheaper and requires less money to maintain.
Ground water. If their level on the site is high, then the installation of a septic tank becomes impossible, since it will not be possible to install additional treatment facilities (equipment of filtration wells and pits in this case will be costly and require a large amount of work). The advantage of VOCs is obvious - the water at the outlet will not be dangerous to the environment.
Electricity supply. With frequent shutdowns and power outages, the installation of an autonomous sewage system is not recommended. When the system stops, filters can fail and bacteria can die. Refueling and repairing such a system is an expensive procedure. It is possible to install a backup power source, but it would be preferable in this case to use a septic tank-based sewer.
Seasonal accommodation. If the owners live in the house only part of the year, then the choice falls in favor of a septic tank. Long breaks in work can adversely affect the operation of local treatment facilities, and the operation of electrical systems of autonomous sewerage in vain will lead to unnecessary financial costs.

Thus, autonomous sewage is the most progressive way to treat wastewater in a private house. The only downside is the cost of the equipment. It is also worth remembering that VOCs require electricity to operate, and when it is turned off, the device will work like a septic tank. Therefore, the final choice, taking into account all the pros and cons, remains with the owner of the house.

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

Most people don't think about what happens to what they flush when they press the toilet button. Leaked and flowed away, that's business. In such a large city as Moscow, no less than four million cubic meters of sewage flows into the sewer system every day. This is about the same as the amount of water flowing in the Moskva River in a day in front of the Kremlin. All this huge volume of waste water needs to be cleaned and this task is very difficult.

There are two largest wastewater treatment plants in Moscow, approximately the same size. Each of them cleans up half of what Moscow "produces". I have already spoken in detail about the Kuryanovsky 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 at treatment stations they fight unpleasant odors with the help of low-temperature plasma and perfume industry waste and why this problem has become more relevant than ever .

To start, a little history. For the first time, sewerage "came" to the area of modern Lyubertsy at the beginning of the 20th century. Then the Lyubertsy irrigation fields were created, on which sewage, according to the 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 plant, the Lyuberetskaya, was built. A little later, another station was built - Novoluberetskaya, which actually borders on the first one and uses part of its infrastructure. In fact, now it is one large cleaning station, but consisting of two parts - the old and the 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 area of the station is huge, in a straight line from corner to corner about two kilometers.

As it is not difficult to 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, almost no one lived around it. There was a small village nearby, where the station workers themselves lived. Then this area was far, far from Moscow. Right now there is a lot of building going on. The station is actually surrounded by new buildings from all sides and there will be even more of them. New houses are being built even on the former sludge sites of the station (fields where the sludge left over from wastewater treatment was brought). As a result, residents of nearby houses are forced to periodically sniff "sewer" smells, and of course they constantly complain.

2) Sewer water has become more concentrated than before, in Soviet times. This happened due to the fact that the volume of water used has been greatly reduced in recent years, while people did not go to the toilet less, but on the contrary, the population has grown. There are quite a few reasons why the "diluting" water has become much less:
a) the use of meters - water has become more economical to use;
b) the use of more modern plumbing - it is less and less common to see a running faucet or toilet bowl;
c) the use of more economical household appliances - washing machines, dishwashers, etc.;
d) the closure of a huge number of industrial enterprises that consumed a lot of water - AZLK, ZIL, Hammer and Sickle (partially), etc.
As a result, if the station during construction was calculated 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 larger flow, leading to to bad odors. The station itself began to smell more.

To combat the smell, Mosvodokanal, which is in charge of 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, the flow of water. Waste water from Moscow enters the station through the Luberetsky sewer canal, which is a huge underground collector filled with sewage. The channel is gravity-flowing and runs at a very shallow depth for almost its entire length, and sometimes even above the ground. Its scale can be estimated from the roof of the administrative building of the treatment plant:

The width of the channel 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 receiver looks like this:

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

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

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

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

Under the ceiling, gases released from wastewater accumulate. This is mainly methane and hydrogen sulfide - both gases are explosive at high concentrations, so the space under the ceiling must be ventilated, but the next problem arises - if you just put a fan, then the whole point of the ceiling will simply disappear - the smell will get out. Therefore, to solve the problem, ICD "Horizon" has developed and manufactured a special unit for air purification. The installation is located in a separate booth and a ventilation pipe from the channel goes to it.

This installation is experimental, for testing the technology. In the near future, such installations will be mass-produced at treatment facilities and at sewage pumping stations, of which there are more than 150 units in Moscow and from which unpleasant odors also come. On the right in the photo - one of the developers and testers of the installation - Alexander Pozinovskiy.

The principle of operation of the installation is as follows:
polluted air is fed into four vertical stainless steel pipes from below. In the same pipes there are electrodes, to which a 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. Water circulates in a circle, the water tank is the blue container on the right, below in the photo. The purified air exits from the top of the stainless pipes and is simply released into the atmosphere.

For patriots - the installation is completely designed and created in Russia, with the exception of the power stabilizer (below in the closet in the photo). High voltage part of the installation:

Since the installation is experimental, it has 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 charge is clearly visible on the oscillogram.

Two tubes go to the gas analyzer - one takes air before installation, the other after. In addition, there is a tap that allows you to select the tube that is connected to the gas analyzer sensor. Alexander first shows us the "dirty" air. The content of hydrogen sulfide is 10.3 mg/m3. After switching the tap - the content drops to almost zero: 0.0-0.1.

Further, the supply channel rests against a special distribution chamber (also covered with metal), where the flow is divided into 12 parts and goes further to the so-called grate building, which is visible in the background. There, wastewater passes the very first stage of treatment - the removal of large debris. As it is not difficult to guess from the name - for this 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 - they stick out here and there

After cleaning from large debris, the water enters the sand traps, which, 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 - in fact, it is a long rectangular tank in which water moves at a certain speed, as a result, the sand simply has time to settle. Also, air is supplied there, which contributes to the process. From below, the sand is removed using special mechanisms.

As is often the case in technology, the idea is simple, but the execution is complex. So here - visually, this is the most "fancy" design on the way of water purification.

Sand traps were chosen by seagulls. In general, there were a lot of seagulls at the Lyubertsy station, but it was on the sand traps that they were the most.

I enlarged the photo already at home and laughed at their appearance - funny birds. They are called lake gulls. No, they don’t have a dark head because they constantly dip it where they don’t need it, it’s just such 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. In the photo - the bottom of the sand trap (not working at the moment). It is there that the sand settles and from there it is removed.

After sand traps, water again enters the common channel.

Here you can see what all the channels at the station looked like before they were covered. This channel is shutting down right now.

The frame is made of stainless steel, like most metal structures in the sewer. The matter is that in the sewerage very aggressive environment - water full of any substances, 100% humidity, gases promoting corrosion. Ordinary iron very quickly turns into dust in such conditions.

Work is being carried out directly above the existing 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 speed of the water. As a result - very active seething.

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

The classic sump looks like this:

And without water - like this:

Dirty water enters from the hole in the center of the sump and enters the general volume. In the sump itself, the suspension contained in the dirty water gradually settles to the bottom, along which the sludge rake is constantly moving, fixed on a truss rotating in a circle. The scraper rakes the sediment into a special annular 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 the channel laid around the sump and from there into the pipe.

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

At the same time, if you make a roof, then, firstly, it must withstand the snow load in winter, and secondly, it must have only one support in the center - it is impossible to make supports above the sump itself, because. there is a farm going on all the time. As a result, an elegant decision was made - to make the floor floating.

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

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

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

This sump was the first and experimental one where this technology was tested. The experiment was recognized as successful, and now other sedimentation tanks are being covered in a similar way at the Kuryanovskaya station. Over time, all primary clarifiers will be covered in this way.

However, the process of reconstruction 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. And yes, it takes a lot of money. Therefore, until all the sedimentation tanks are covered, the third method of dealing with odors is used - spraying neutralizing substances.

Special sprayers have been installed around the primary clarifiers, which create a cloud of odor neutralizing substances. The substances themselves smell not to say very pleasant or unpleasant, but rather specific, however, their task is not to mask the smell, but to neutralize it. Unfortunately, I did not remember the specific substances that are used, but as they said at the station, these are waste products from the perfume industry in France.

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, water enters the aerotanks - 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 recycles "waste" and multiplies rapidly. The process is similar to what happens in nature in water bodies, but proceeds many times faster due to warm water, a large amount of air and silt.

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

Aerotanks, oddly enough, do not particularly exude strong unpleasant odors, so it is not planned to cover them.

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

Some of the facilities are currently disabled and mothballed, for the reasons I wrote about at the beginning of the post - the decrease in water flow in recent years.

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

Mothballed secondary clarifiers.

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

The water collected in the annular trough of the sump flows into the pipe. Part of the water undergoes additional UV disinfection and merges into the Pekhorka River, while part of the water goes through an underground channel to the Moskva River.

The settled activated sludge is used to produce methane, which is then stored in semi-underground tanks - 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 additionally dehydrated and either buried or burned.

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

A pipe from which a powerful jet pours rating social capital the contents of a sewer

Aerotanks YuZOS

So, let's begin. Water, diluted with soap and shampoo, street dirt, industrial waste, leftover food, and the results of this digestion of food (all this ends up in the sewer, and then to the sewage treatment plant) has a long and thorny path to go before it again believes in Neva or the Gulf of Finland. This path begins either in the drain grate, if it happens on the street, or in the “fan” pipe, if we are talking about apartments and offices. From not so big (15 cm in diameter, everyone has probably seen them at home in the bathroom or toilet rooms) In the fan pipes, water mixed with waste enters larger common house pipes. Several houses (as well as street drains in the surrounding area) are combined into a local catchment area, which, in turn, are combined into sewerage areas and further into sewerage pools. At each stage, the diameter of the pipe with sewage 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 fully supply 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 perfectly reasonable question - “Why bother treating wastewater at all? The bay with the Neva will endure everything! In general, this was how it used to be, until 1978, the drains were practically not cleaned in any way and immediately fell into the bay. The bay processed them poorly, coping, however, with the increasing flow of sewage every year is getting worse. Naturally, this state of affairs could not but affect the environment. Our Scandinavian neighbors suffered most of all, but the environs of St. Petersburg also experienced a negative impact. And the prospect of a dam across the Finnish made me think that the waste of a million-plus city, instead of a happy voyage in the Baltic Sea, will now hang out between Kronstadt and (then still) Leningrad. In general, the prospects of choking with sewage over time did not please anyone, and the city, represented by Vodokanal, gradually began to solve the problem of wastewater treatment. It can be considered almost completely solved only 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.

Sewerage basins on the map of St. Petersburg

Let's look at the example of the South-West Treatment Plant, how the treatment takes place. Having reached the very bottom of the collector (the bottom is just on the territory of the treatment plant), the water rises to a height of almost 20 meters with 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 grates, on which large and not very large debris remains - all sorts of rags, dirty socks, drowned kittens, lost mobile phones and other wallets with documents. Most of the collected goes straight to the landfill, but the most curious finds remain in a makeshift museum.

Pumping station

Swimming pool with sewage. outside view

Swimming pool with sewage. Inside view

This room has grates that catch large debris.

Behind the muddy plastic, you can see the grate assembled. 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 gratings. Chemical reagents are added to the water to remove phosphorus before being released from the sand traps. Further, the water is sent to the primary settling tanks, in which suspended and floating substances are separated.

Primary settlers 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 many microorganisms also live. It is also necessary to get rid of all this, and start with organic ...

sand traps

The structure in the foreground slowly moves along the pool

Primary clarifiers. 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 hefty bathrooms into which water is poured, air is pumped in and "activated sludge" is launched - a cocktail of the simplest microorganisms, sharpened to digest precisely those chemical compounds that need to be eliminated. 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 bath in five hours. Further, 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 that is burned), and the water enters the last stage of purification - ultraviolet treatment.

Aerotanks. The effect of "boiling" due to active air injection

Control room. You can see the entire station from above.

Secondary sump. For some reason, the water in it is very attractive to birds.

At the South-Western Treatment Facilities, subjective quality control 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 between the emotions of crustaceans, a more objective assessment is used - a cardiogram. If suddenly several (protection against false positives) crayfish experienced severe stress, then something is wrong with the water, and you need to urgently figure out which of the cleaning stages failed.

But this situation is abnormal, and in the usual order of things, already clean water is sent to the Gulf of Finland. Yes, about cleanliness. Although crayfish exist in such water, and microbes-viruses are all removed from it, it is still not recommended to drink it . Nevertheless, the water fully complies with the environmental standards of HELCOM (the convention for the protection of the Baltic from pollution), which in recent years has already had a positive effect on the state of the Gulf of Finland.

Ominous green light disinfects water

Cancer detector. Not an ordinary rope is attached to the shell, but a cable through which data about the state of the animal is transmitted

clack clack

I will say a few more words about the disposal of everything that is filtered out of the water. Solid waste is transported to landfills, but everything else is burned at a plant located on the territory of the treatment plant. Dehydrated sludge from the primary settling tanks and excess activated sludge from the secondary ones are sent to the furnace. Combustion takes place at a relatively high temperature (800 degrees) to maximize the reduction of harmful substances in the exhaust. Surprisingly, only a small part, about 10%, of the total volume of the plant's premises, stoves occupy. The remaining 90% is given to a huge system of various filters that screen out all possible and impossible harmful substances. By the way, a similar subjective system of “quality control” has been introduced at the plant. 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 the permissible one, the mollusk's body will immediately react.

Furnaces

P blow-off valves of the waste heat boiler. The purpose is not completely clear, but how impressive they look!

Snail. Above her head is a tube from which water drips. And next to it is another one with an exhaust

P.S. One of the most popular questions that were asked for the announcement - "Well, what's with the smell? It stinks, right?". I turned out to be somewhat disappointed with the smell :) The uncleaned contents of the sewer (in the very first photo) practically do not smell. On the territory of the station, the smell, of course, is present, but very moderate. The strongest stink (and this is already noticeable!) is the dehydrated sludge from the primary settling tanks and activated sludge - that which is sent to the stove. Therefore, by the way, they began to burn them, the landfills to which silt was previously brought gave a very unpleasant smell to the surroundings ...

Other interesting posts on the topic of industry and production.

Multi-apartment and private houses, enterprises and institutions of the service sector use water, which, after passing through the sewer mains, must be brought to the required level of purity, then sent for reuse or poured into rivers. In order not to create a dangerous ecological situation, treatment facilities have been created.

Definition and purpose

Treatment facilities are complex equipment designed to solve the most important problems - ecology and human health. The amount of sewage is constantly increasing, new types of detergents appear that are difficult to remove from the water so that it is suitable for further use.

The system is designed to receive a certain amount of wastewater from a city or local sewage system, clean it from all kinds of impurities and organic substances, and then send it to natural reservoirs using pumping equipment or by gravity.

Principle of operation

During the operation of the purification station, water is released from the following types of pollution:

organic (feces, food leftovers);
mineral (sand, stones, glass);
biological;
bacteriological.

The greatest danger is bacteriological and biological sewage. When decomposed, they release dangerous toxins and unpleasant odors. With an insufficient level of purification, an epidemic of dysentery or typhoid fever can occur. To prevent such situations, water after a full purification cycle is checked for the presence of pathogenic flora, and only after the examination is carried out, it is drained into reservoirs.

The principle of operation of treatment facilities is the phased separation of debris, sand, organic components, fat. The semi-cleaned liquid is then sent to sedimentation tanks with bacteria that process the smallest particles. These colonies of microorganisms are called activated sludge. Bacteria also release their waste products into the water, so after they have utilized the organic matter, the water is cleared of bacteria and their waste.

In the most modern equipment, almost waste-free production takes place - the sand is caught and used for construction work, the bacteria are compressed and sent to the fields as fertilizer. Water goes back to consumers or to the river.

Types and arrangement of treatment facilities

There are several types of wastewater, so the equipment must match the quality of the incoming liquid. Allocate:

Household waste is used water from apartments, houses, schools, kindergartens, food establishments.
Industrial. In addition to organics, they contain chemicals, oil, salts. For such waste, appropriate cleaning methods are required, as bacteria cannot cope with chemicals.
Rain. The main thing here is to remove all the garbage that is washed down the drain. This water is less polluted with organic matter.

According to the volume that the treatment plant serves, the stations are:

urban - the entire volume of wastewater is directed to facilities with a huge throughput and area; located away from residential areas or made closed so that the smell does not spread;
VOC - a local treatment plant serving, for example, a holiday village or village;
a septic tank - a type of VOC - serves a private house or several houses;
mobile units that are used as needed.

In addition to complex structures, such as biological treatment stations, there are more primitive devices - grease traps, sand traps, gratings, sieves, settling tanks.

The device of the biological treatment station

Stages of water treatment at wastewater treatment plants:

mechanical;
primary sump;
aeration tank;
secondary sump;
post-treatment;
disinfection.

At industrial enterprises, containers with reagents and special filters for oils, fuel oil and various inclusions are additionally installed in the system.

In the process of receipt of waste, they are first cleaned of mechanical impurities - bottles, plastic bags and other debris. Further, the effluents are passed through a sand trap and a grease trap, then the liquid enters the primary settling tank, where large particles settle to the bottom and are removed by special scrapers into the bunker.

Next, the water is sent to the aeration tank, where organic particles absorb aerobic microorganisms. In order for bacteria to multiply, oxygen is additionally supplied to the aerotank. After clarification of effluents, it is necessary to dispose of the excess mass of microorganisms. This happens in the secondary sump, where bacterial colonies settle to the bottom. Some of them are returned to the aerotank, the excess is compressed and removed.

Post-treatment is an additional filtration. Not all facilities have filters - carbon or membrane, but they allow you to completely remove organic particles from the liquid.

The last stage is exposure to chlorine or ultraviolet to destroy pathogens.

Water purification methods

There are a large number of methods by which you can clean drains - both domestic and industrial:

Aeration - forced saturation of wastewater with oxygen for the speedy weathering of odors, as well as for the growth of bacteria that decompose organic matter.
Flotation is a method based on the ability of particles to be held between a gas and a liquid. Foam bubbles, oily substances raise them to the surface, from where they are removed. Some particles are able to form a film on the surface, which is easy to drain or collect.
Sorption is a method of absorption by some substances of others.
Centrifuge is a method that uses centrifugal force.
Chemical neutralization, in which an acid interacts with an alkali, after which the precipitate is disposed of.
Evaporation is a method in which heated steam is passed through dirty water. Volatile substances are removed along with it.

Most often, these methods are combined into complexes in order to carry out cleaning at a higher level, taking into account the requirements of sanitary and epidemiological stations.

Design of treatment systems

The layout of the treatment facilities is designed based on the following factors:

The level of occurrence of groundwater. The most important factor for autonomous cleaning systems. When arranging a septic tank with an open bottom, after settling and biological treatment, the effluents are removed into the ground, where they enter the groundwater. The distance to them should be sufficient so that the liquid is cleared when passing through the soil.
Chemical composition. From the very beginning, it is necessary to know exactly what waste will be treated, what equipment is needed for this.
The quality of the soil, its penetrating ability. For example, sandy soils absorb liquid faster, but clayey areas will not allow wastewater to be disposed of through an open bottom, which will lead to overflow.
Waste disposal - entrances for cars that will serve the station or septic tank.
The possibility of draining clean water into a natural reservoir.

All treatment facilities are designed by special firms that are licensed to carry out such work. A permit is not required for the construction of a private sewer.

Installation of installations

When installing water treatment facilities, many factors must be taken into account. First of all, it is the terrain and system performance. It is necessary to expect that the volume of effluents will constantly increase.

The stable operation of the station, the durability of the equipment will depend on the quality of the work performed, so public facilities must be well designed, taking into account all the features of the area and the configuration of the system.

Project creation.
Inspection of the site and preparatory work.
Installation of equipment and connection of nodes.
Station control setup.
Testing and commissioning.

The simplest types of autonomous sewage require the correct slope of the pipes so that the line does not become clogged.

Operation and maintenance

Water quality should be checked regularly

Planned maintenance prevents serious accidents, so large wastewater treatment plants have a schedule according to which units and the most significant components are regularly repaired, and parts that fail are replaced.

At biological treatment plants, the main points requiring attention are:

amount of activated sludge;
the level of oxygen in the water;
timely removal of garbage, sand and organic waste;
control of the final level of wastewater treatment.

Automation is the main link that is involved in the work, therefore, checking the electrical equipment and control units by a specialist is a guarantee of the uninterrupted operation of the station.

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 sewer

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 goes 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.