Treatment facilities for domestic wastewater.
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.
Sewage basins on the map of St. Petersburg
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.
Pumping station
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 the 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...
Sand traps
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 dehydrated 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...
Other interesting posts on the topic of industry and production.
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 conditions. 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.
Before designing treatment facilities for domestic wastewater or other types of wastewater, it is important to find out their volume (the amount of wastewater generated over a certain period of time), the presence of impurities (toxic, insoluble, abrasive, etc.) and other parameters.
Types of wastewater
Wastewater treatment plants are installed for various types of wastewater.
- Domestic wastewater– these are drains from plumbing fixtures (washbasins, sinks, toilets, etc.) of residential buildings, including private houses, as well as institutions, public buildings. Household wastewater is dangerous as a breeding ground for pathogenic bacteria.
- Industrial effluents are formed in enterprises. The category is characterized by the possible presence of various impurities, some of which significantly complicate the purification process. Industrial wastewater treatment plants are usually complex in design and have several stages of treatment. The completeness of such structures is selected in accordance with the composition of the wastewater. Industrial wastewater can be toxic, acidic, alkaline, containing mechanical impurities and even radioactive.
- Storm drains due to the method of formation they are also called superficial. They are also called rain or atmospheric. This type of drainage is a liquid formed on roofs, roads, terraces, and squares during precipitation. Stormwater treatment plants typically include multiple stages and are capable of removing different types of contaminants (organic and mineral, soluble and insoluble, liquid, solid and colloidal) from the liquid. Storm drains are the least dangerous and least polluted of all.
Types of treatment facilities
In order to understand what blocks a treatment complex may consist of, you should know the main types of wastewater treatment facilities.
These include:
- mechanical structures,
- biorefinery installations,
- oxygen saturation units that enrich already purified liquid,
- adsorption filters,
- ion exchange blocks,
- electrochemical installations,
- physical and chemical cleaning equipment,
- disinfection installations.
Effluent treatment equipment also includes structures and tanks for storage and storage, as well as for processing filtered sludge.
Operating principle of the wastewater treatment complex
The complex can implement a scheme of wastewater treatment facilities with above-ground or underground design.
Treatment facilities for domestic wastewater are installed in cottage villages, as well as in small settlements (150-30,000 people), at enterprises, in regional centers, etc.
If the complex is installed on the surface of the earth, it has a modular design. In order to minimize damage, reduce costs and labor costs for repairing underground structures, their bodies are made of materials whose strength allows them to withstand the pressure of soil and groundwater. Among other things, such materials are durable (up to 50 years of service).
To understand the operating principle of wastewater treatment plants, let’s consider how the individual stages of the complex function.
Mechanical cleaning
This stage includes the following types of structures:
- primary settling tanks,
- sand traps,
- debris-retaining grates, etc.
All these devices are designed to eliminate suspended matter, large and small insoluble impurities. The largest inclusions are retained by the grill and fall into a special removable container. The so-called sand traps have limited productivity, therefore, when the intensity of wastewater supply to treatment plants is more than 100 cubic meters. m per day, it is advisable to install two devices in parallel. In this case, their efficiency will be optimal; sand traps will be able to retain up to 60% of suspended matter. The retained sand with water (sand pulp) is discharged to sand pads or to a sand bunker.
Biological treatment
After removing the bulk of insoluble impurities (cleaning the wastewater), the liquid for further purification enters the aeration tank - a complex multifunctional device with extended aeration. The aeration tanks will be divided into sections of aerobic and anaerobic purification, due to which, simultaneously with the breakdown of biological (organic) impurities, phosphates and nitrates are removed from the liquid. This significantly increases the efficiency of the second stage of the treatment complex. The active biomass released from the wastewater is retained in special blocks loaded with polymer material. Such blocks are placed in the aeration zone.
After the aeration tank, the sludge mass passes into a secondary settling tank, where it is separated into activated sludge and treated wastewater.
Additional treatment
Post-treatment of wastewater is carried out using self-cleaning sand filters or using modern membrane filters. At this stage, the amount of suspended solids present in the water is reduced to 3 mg/l.
Disinfection
Disinfection of treated wastewater is carried out by treating the liquid with ultraviolet light. To increase the efficiency of this stage, biological wastewater treatment plants are equipped with additional blowing equipment.
Effluents that have passed all stages of the treatment complex are safe for the environment and can be discharged into a reservoir.
Design of treatment systems
Treatment facilities for industrial wastewater are designed taking into account the following factors:
- groundwater level,
- design, geometry, location of the supply manifold,
- completeness of the system (type and number of blocks determined in advance based on biochemical analysis of wastewater or its predicted composition),
- location of compressor units,
- availability of free access for vehicles that will remove waste trapped by grates, as well as for sewage disposal equipment,
- possible placement of the purified liquid outlet,
- the need to use additional equipment (determined by the presence of specific impurities and other individual characteristics of the object).
Important: Surface wastewater treatment facilities should be designed only by companies or organizations with an SRO certificate.
Installation of installations
The correct installation of treatment facilities and the absence of errors at this stage largely determine the durability of the complexes and their efficiency, as well as the uninterrupted operation - one of the most important indicators.
Installation work includes the following steps:
- development of installation diagrams,
- inspection of the site and determination of its readiness for installation,
- construction works,
- connecting installations to communications and connecting them to each other,
- commissioning, adjustment and adjustment of automation,
- delivery of the object.
The full range of installation work (list of necessary operations, volume of work, time required to complete them and other parameters) are determined based on the characteristics of the object: its productivity, completeness), as well as taking into account the characteristics of the installation site (type of relief, soil, location of groundwater and etc.).
Treatment plant maintenance
Timely and professional maintenance of wastewater treatment plants ensures the efficiency of the equipment. Therefore, such work must be performed by specialists.
The scope of work includes:
- removal of retained insoluble inclusions (large debris, sand),
- determining the amount of sludge formed,
- checking oxygen content,
- control of work according to chemical and microbiological indicators,
- checking the functioning of all elements.
The most important stage in the maintenance of local treatment facilities is monitoring the operation and prevention of electrical equipment. Typically, blowers and transfer pumps fall into this category. Ultraviolet disinfection installations also require similar maintenance.
Everything that residents of the capital pour into sinks and toilets ultimately turns into millions of cubic meters of wastewater. They have been dumped into the Moscow River for many years now. To clean them, two large aeration stations were built in the city: in Lyubertsy and in the Pechatnikov area. At the same time, the Kuryanovsky treatment facilities operating in the South-Eastern Autonomous Okrug (South-Eastern Autonomous Okrug) are the oldest and largest.
General description of the object
The area served by the station is home to a huge number of people—more than 6 million people. In addition, several manufacturing plants are located nearby. Therefore, every day the station receives a truly colossal amount of wastewater - about 1.8 million m3. Of this, 20% comes from the residential sector, and 80% from the industrial sector. The Kuryanovskaya station is located in the industrial zone of the Pechatniki district, in the left-bank floodplain of the Moscow River. To date, this important facility is one of the largest in Europe.
In total, this complex includes three blocks (NKTP), each of which can be used to treat 1 million m 3 of wastewater per day. Thus, in total, the Kuryanovsky treatment facilities are designed for a load of 3 million m 3 in 24 hours.
A little history
The first facilities at this station were erected in 1939. However, due to the outbreak of the Second World War, work was suspended for a long time. The Kuryanovsky treatment facilities were put into operation only in 1950. At that time, the station, like any other complex of a similar purpose, was located very far from the city - among the steppes and forests, next to several small factories. However, the area of Moscow gradually increased, and eventually the station found itself within its borders. Moreover, it was already surrounded not only by industrial enterprises that were still operating in this area, but also by residential areas.
Of course, the increase in load made the original design capacity of this facility insufficient. Therefore, in the 70s of the last century, Mosvodokanal decided to expand the treatment facilities in the Pechatniki area. In the immediate vicinity of the old complex, the Novokuryanovskaya station was built, consisting of two, more modern blocks. Simultaneously with their construction, a new outlet channel was laid.
Of course, over time, the designs of the new station became obsolete. Therefore, in 2011, their large-scale modernization began. By now, these works have already been completed.
Pechatniki District (Moscow)
The area of this part of the capital is 17.89 km 2 in total. The Pechatniki district consists of 30 streets. To date, about 75 thousand people live in the immediate vicinity of the Kuryanovsky treatment plant.
The Pechatniki area is currently considered very suitable for living. The infrastructure here is very well developed, for example, there are two metro stations and four in the Kursk direction of the Moscow Railway. Until recently, no one particularly wanted to buy apartments in the Pechatniki area. It was all about the disgusting smell spreading from the wastewater treatment plant. However, quite recently this problem has been completely resolved. We'll talk about how exactly below.
Station design
The Kuryanovsky complex, therefore, is the largest. The process of wastewater treatment at this facility begins with one of three receiving chambers directly connected to the city sewerage collectors. From here, the flow of sewage through underground pipelines is distributed to the sewage treatment plant of the station (through the screen building). Today, wastewater mainly flows into one of the two blocks of the new station. Each sewer line supplying wastewater to the sewage treatment plant can be blocked by its own. Before entering the treatment unit, the wastewater is supplied to the Screen Building for primary mechanical treatment. They are then pumped into sand traps. Next, the effluents are supplied sequentially:
to primary settling tanks;
aeration tanks;
to secondary settling tanks;
into the outlet chamber.
Air is supplied to the aeration tanks from a huge machine room equipped with high-power turbo blowers. Sludge from settling tanks enters a special digester, where its fermentation occurs. The gas released as a result of this process is used at a small thermal power plant built nearby. This interesting technical solution made it possible to provide the Kuryanovsky treatment facilities with 60% of its own electricity. At the final stage, completely purified water flows through a diversion canal into the Moscow River. Throughout the station, wastewater flows by gravity. To do this, each subsequent set of treatment equipment is located slightly lower than the previous one.
How does mechanical cleaning work?
Actually, the wastewater treatment technology itself was thought out to the smallest detail by the engineers of Vodokanal LLC (Moscow). The gratings undergo initial processing in the Grating Building. Here large mechanical impurities are removed from them. To do this, they are passed through special gratings. The latter are something like a large container fixed directly in the flow of water. Selected large waste - crumpled plastic, bottle caps, pieces of polyethylene, leaves, grass, etc. - are sent along a conveyor belt for recycling. Oddly enough, the workers in this workshop are most troubled by ordinary cotton swabs for their ears. Their dimensions in the transverse direction are very small, and therefore they easily pass through the grates of containers.
The primary mechanical treatment building is divided into two parts. Each of them serves its own block of the new station. After the screen building, wastewater enters special sand traps to remove small mechanical debris. The insoluble mineral suspension separated from the wastewater is subsequently washed and supplied to factories producing building mixtures, paving slabs, etc.
Biological treatment
Of course, for high-quality water purification, removing ordinary debris and various types of mechanical impurities from it is not enough. Kuryanovsky aeration stations are a modern complex, the wastewater from which is also subjected to biological treatment. After sand traps, they enter primary settling tanks. Here, suspended particles remaining in the water settle to the bottom under the influence of gravity. Each NKOS block is equipped with 8 such pools.
After settling tanks, water is supplied to aeration tanks. This is the name for special containers containing biologically active sludge. The bacteria living in it begin to actively process the dirt remaining in the water. In fact, the same process occurs in natural reservoirs. However, at the station the cleaning procedure is much faster. The technology of biological treatment at WWTP involves supplying a strong air flow to the aeration tanks. It is a natural stimulator of bacterial activity. The wastewater treatment complex at the station includes, as already mentioned, a machine room built for this purpose. It is from here that the air flow necessary for bacteria enters the aeration tanks.
The main difficulty of this cleaning stage is the need to ensure uninterrupted operation of the pipe blowers. The fact is that without air, bacteria living in the sludge of aeration tanks can die within just a few hours. It takes a very long time for their population to recover – over the course of several months.
After the aeration tanks, almost clean water flows into secondary settling tanks. At this stage, the remnants of the activated sludge are removed from it. At the bottom of each secondary settling tank there is a special mechanism - a sludge rake. This tool collects sediment into a large tray. Next, the sludge is transported to special landfills located 60 km from the capital.
Methane use
The sludge in aeration tanks constantly multiplies. The resulting surplus is partially preserved. They can be reused later. The main part of the “excess” sludge is sent for digestion into special semi-underground tanks - digesters. Here the sludge is heated to 54 o C, as a result of which a reaction begins to occur in it with the release of gas. The resulting methane is supplied to thermal power plants to generate electricity.
TPP
The thermal power plant of the Kuryanovskaya wastewater treatment plant (Pechatniki district, Moscow) is a truly unique structure. There are no analogues of such a structure anywhere in the world. It was decided to build this facility in 2005, after a major accident, as a result of which half of Moscow was cut off, including the WWTP turbine room. That day, the bacteria in the aeration tanks did not receive the air they needed for about three hours. The construction of the thermal power plant completely eliminated the possibility of a recurrence of such an unpleasant situation.
How wastewater is analyzed
Of course, the quality of water discharged into the Moscow River at the station is periodically checked. Mechanical studies are carried out in stages, according to the following parameters:
degree of transparency.
chromaticity;
temperature;
The first parameter is measured in degrees on the platinum-cobalt scale. Temperature, smell and transparency - by font. Chemical analysis of wastewater is performed on the pH reaction and the proportion of various impurities. Based on the last feature, wastewater can be divided into four categories:
municipal wastewater (dry residue - less than 500 mg/l);
The chemical and microbiological composition of wastewater discharged by the Kuryanovskaya station in the South-Eastern Administrative District (Moscow) fully complies with SanPiN 2.1.5.980-00 standards.
Where does the waste go?
From the secondary settling tank, completely purified water flows into the outlet chamber. Next, it is fed into an outlet channel connected to the Moscow River, the total length of which is 700 m. Until recently, this was the end of wastewater treatment. But a few years ago a new disinfection building was built on the canal. Here they are additionally disinfected using ultraviolet light. After such treatment, various pathogenic microorganisms die in the water. That is, the Kuryanovsky treatment plant now discharges water into the Moscow River not only well purified, but also completely disinfected. This contributes to a significant improvement in the environmental situation in the capital.
Fish in the canal
The quality of wastewater at the Kuryanovskaya station, whose activities are controlled by Vodokanal LLC (Moscow), is truly at the highest level. This is evidenced by the fact that simply a huge number of fish live in the outlet channel of the complex. Once upon a time, many local residents fished for it. However, not so long ago the entrance to the station was closed to outsiders. Security guards now keep order here, preventing not only fishing enthusiasts from entering the territory, but also local boys.
Smell
To date, Muscovites who have chosen the Pechatniki area to live do not experience any problems associated with wastewater treatment plants. But just recently, an extremely unpleasant, pungent odor spread from the territory of this facility throughout the entire area. In 2012, after repeated appeals from residents to the district and Moscow administrations, a decision was made to reconstruct the station. As a result, the receiving chambers located at the entrance were closed over almost the entire surface
They also decided to prevent the spread of odor from the primary settling tanks using a lid. But in this case, metal sheets were used. To date, these containers are closed with two lids at once - a floating pontoon and an upper console. Kuryanovsky aeration stations are the only complex in the world that uses such efficient and inexpensive designs. Some already partially collapsed settling tanks were eliminated during modernization.
Local sewage treatment plants (STPs) are of several types, depending on the principle used for treating domestic wastewater. Each cleaning method has its advantages and disadvantages, but always finds application in a given situation. Local sewage treatment plants operate in a comprehensive manner, that is, cleaning occurs in several stages, and the final step is to obtain clean industrial water suitable for domestic needs (except for washing and cooking).
Sewage treatment plants
There are different ways to dispose of harmful impurities from sewage:
- Mechanical cleaning.
- Biological treatment and filters.
- Physico-chemical wastewater treatment.
- Disinfection of sewage wastewater.
Mechanical cleaning
The first and crudest treatment option is local sewage treatment plants, in which mechanical filters are installed as the first barrier. Filtration prepares wastewater for biological treatment. Large solid fractions are retained here when wastewater passes through settling tanks, septic tanks, sand traps, metal mesh filters, membranes and gratings that retain insoluble fractions. The entire operating principle of sewerage treatment facilities during mechanical wastewater treatment consists of several sequential steps:
- Grids, meshes and metal sieve retain large debris and fractions of organic and mineral origin.
- Sand traps prevent small particles from passing further through the cleaning cycle.
- The membrane removes the remaining fine fractions - this is called deep cleaning.
- In the settling tank, the water is purified from remaining suspended particles.
After these four stages of purification, the water can be 60-70% purified. After several years of operation of the VOC, a partial reconstruction of the sewage treatment plant with replacement of filters is required.
Biological wastewater treatment
If further purification is required, a biological method is used. Tanks with mechanically purified wastewater are colonized by anaerobic microorganisms and bacteria that feed on the remains of organic substances. At this stage of treatment, activated sludge, biological filters, or the process of anaerobic fermentation can be started.
The physico-chemical stage involves the use of various chemicals and impurities to improve the quality of the purified water. These are complex processes such as ozonation, chlorination and other chemical reactions. Therefore, the construction of sewage treatment plants should be carried out only by professionals and according to a previously developed project.
If the treatment system provides for the discharge of wastewater into an artificial (natural) reservoir, then it is necessary to disinfect the water. This is done using UV filters or treating with chlorine for 30 minutes.
Cleaning with septic tanks
But such methods of sewage treatment are effective for the city. What should summer residents or owners of country cottages and houses do? The most relevant sewage treatment facilities for a village or country house are septic tanks. And if there is demand, then there will be supply. Industry and private enterprises offer many different options for such autonomous installations, operating in different ways. Therefore, the problem of wastewater disposal and treatment for detached buildings is solved by autonomous sewage treatment plants.
A septic tank is a large-capacity tank that is installed on a site at a certain depth. It is recommended to select the most efficient installation for each terrain, so the preliminary design of sewerage treatment plants is an integral part of the construction of the VOC. Wastewater is purified due to the precipitation of solid fractions. Additionally and finally, the water is purified in a filtration field. After this, it can be poured into the ground or used for technical purposes.
If you install additional filters, you can pump out water once every 4-5 years - the frequency depends on the volume of the septic tank chambers. Aerotanks are used as a post-treatment system.
An aeration tank is a device for biological wastewater treatment. It is a system of reservoirs populated by microorganisms. After this treatment, the water is suitable for disposal into the ground.
Proper operation of sewage treatment plants can improve quality by up to 98%. The disadvantage of this method is the mandatory presence of electricity or good natural supply and exhaust ventilation so that the bacteria do not die without oxygen and that the established volumes of wastewater cannot be exceeded, otherwise the bacteria will not cope with the purification. The tandem of biofilters and septic tank greatly improves water quality.
Ultraviolet disinfection helps protect water from contamination by viruses and pathogens. The ultraviolet installation is used in a comprehensive manner, as part of other treatment facilities, since its function is not to purify water, but only to disinfect it. The UV installation disinfects water by 99%, but the disadvantage of its use is the same - the presence of electricity, which increases the already considerable cost of the station.
How do sewage treatment plants using biological wastewater treatment work? Biological treatment of sewage wastewater is the most effective method. Biological wastewater treatment facilities can be installed near residential buildings and in any climate zone. The service life of such a system is 30-50 years.
The disadvantage of such cleaning is the presence of an unpleasant odor that occurs during fermentation of waste. Modern technologies can eliminate this drawback, but such devices are expensive.
Biological wastewater treatment is also used in conventional septic tanks - bacteria of a certain type are colonized in the septic tank chamber. But there are also storm sewer treatment facilities, which are designed to collect, deliver to a septic tank and purify rain and melt water and further deliver it to filtration fields. Standard septic tanks and sewage treatment plants may not be able to handle large amounts of rainwater, and storm drains were developed for this purpose.
Stormwater treatment plants
The main task of “storm drainage” is to protect the foundation of the house, road surface, lawns, etc. from flooding by rain and melt water. What are local storm sewer treatment facilities? This is a system of downpipes, storm inlets, gutters and drainage through which water is collected and delivered to the collector. The collector must be below the soil freezing level.
All storm sewer elements are equipped with sand traps. Standard urban sewage treatment plants are much more complex and form entire underground communications.
The storm water inlet has an additional filter for purifying melt and rain water. After passing through the filter, the purified water flows into the nearest body of water. You can also water your garden or flower beds with it. Storm drains also require routine cleaning. When choosing a particular storm drain, take into account the following:
- Type of instalation. Many sewerage systems operate in autonomous mode, some require an electrical connection, and there are also stormwater treatment plants that cannot be operated if groundwater comes very close to the surface.
- Cleaning method. Using multiple cleaning methods improves operational efficiency.
- Installation location. It is necessary to adhere to SNiP in this matter.
- Self-installation or professional installation of the system.