Septic tank and how it works. The principle of operation and self-installation of the septic tank "Topas. It consists of several phases

Septic tanks are one of the most effective options for organizing autonomous wastewater treatment. These devices are not too cheap, but they are convenient and reliable.

To understand why it is worth or not worth installing such a device on the site, you should study the principles of its operation. That is what we will talk about in this article. As a current example, we will use a septic tank for giving Topas.

And also we will consider in detail the device of such a system, highlight the main pros and cons, give recommendations for the operation and maintenance of the septic tank.

A septic tank is a type of sewer device specially designed for complete or almost complete processing, clarification and disinfection of sewage waste masses.

The operation of the device is based on the principle of biological treatment. Active oxygen and special bacteria are used as an active component, which decompose wastewater into water and neutral sludge.

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The principle of operation of septic tanks "Topas"

Through the sewer pipe, effluents enter the first receiving chamber. Here, sewage masses are fermented with the active participation of anaerobic bacteria.

When the level of effluents in the receiver reaches a predetermined level, the waste is pumped into the second chamber using an airlift.

When laying all types of sewer pipelines, including the drain system, the level of soil freezing in winter should be taken into account so that the sewage does not freeze and create plugs in the channel intended for their flow.

It is not recommended to pour substances that contain antibiotics, as well as chlorine or manganese compounds into the sewer, since this creates a hostile environment for bacterial cultures, they can simply die.

If the number of bacteria in the septic tank decreases markedly, waste processing will slow down, and an unpleasant smell will appear in the septic tank.

For the same reasons, it is not allowed to use a septic tank for the disposal of large quantities of alcohol-containing liquids, industrial oils, antifreeze, high concentration acids or alkalis, for example, household cleaners.

Do not flush wool down the drain. Although it is organic matter, it cannot be processed quickly enough in a septic tank, but it can clog the device.

Regular removal of neutral sludge accumulated at the bottom of the Topas septic tank is an important part of maintaining the device, ensuring its smooth operation.

Problems can also arise as a result of a power outage. If the septic tank does not work, and the waste continues to flow, this will lead to an overflow of the tank, as a result, the untreated mass will enter the soil.

It should be understood that this is not a heating system, the complete pumping of fluid from the septic tank will have a detrimental effect on the bacteria inhabited in the device. Before conservation, the device is cleaned and left partially filled with water.

Topas septic tanks are reliable and useful devices. They are quite diverse both in terms of functionality and price, which allows you to choose the right septic tank for any site.

It is very important not only to choose the right septic tank for your home or summer cottage, but also to carry out its competent installation and regular maintenance. In this case, the device will work properly for a long time.

Do you have a compact septic tank from the Topas family installed in your country house? Tell us, did you install it yourself or did you call the master? How often do you clean it and are you satisfied with the overall system? Leave your comments and add a photo of your septic tank in the block under this article - your feedback will be useful to many cottage owners.

A few decades ago, many owners of private houses and any land plots they would not even suspect what convenient options for cleaning sewage can be invented by engineers and inventors of modern sewer technologies in the future.

That is why earlier for most people who would like to build an autonomous sewage system at home with biological treatment, the presence and use of a septic tank of the latest generations.

Today, one of such wonderful sewer treatment facilities is the Topas septic tank, which has its own special characteristics.

There are generally two groups of bacteria that are often used in the production and subsequent operation of modern septic tanks - anaerobic and aerobic bacteria.

Aerobic microorganisms live and act under the influence of oxygen, while anaerobic microorganisms are effective only in the absence of active oxygen. In the case of the Topas design, which contains aeration units that let in small air bubbles.

Inside the tanks there is activated sludge exclusively with aerobic bacteria.

These microorganisms can die if aggressive chemicals are used frequently on the farm. chemical substances, which can often be released into offline sewer networks.

Important! Therefore, it is advisable not to use any solvents, alkaline cleaners, acid cleaners or detergents. It is also advisable not to discharge glass, ceramic, plastic, polyethylene and other solid, fibrous or any other insoluble substances into the sewer.

Indeed, in the septic tank, the pumping unit does not have cutting elements that could grind all these items, and therefore they can clog and disable all the mechanisms inside the septic tank.

Before choosing one or another model of Topas septic tanks, you need to properly familiarize yourself with its models, the principle of operation of the sewer installation, as well as with its device.

Important! It's important to know everything specifications and features of Topas septic tanks in order to prevent the formation of emergencies and avoid improper operation.

Video: how often to service

The arrangement of water supply and sewerage systems on the site is one of the most responsible and difficult questions faced by owners of private houses and summer cottages.

Many homeowners refuse traditional ways disposal and purification of sewage, preferring modern, more efficient and reliable methods of treatment. One of these methods is the use of the Topas septic tank installation. Consider the device, the principle of operation of the cleaning system, the installation procedure and the basic rules for operating the Topas septic tank.

Topas septic tank device

Topas septic tank is an autonomous sewage system that purifies wastewater by 98%. Recycled water - not suitable for drinking, but it is absolutely safe for environment and has no bad odor.

The device of a local treatment plant is quite simple, and the operation of a septic tank is based on biological processes that occur in several stages.

Due to the clear structure of the internal device of an autonomous sewage system, a well-functioning cyclic operation of the septic tank occurs

The following equipment components are involved in the cleaning process:

1. Station cover with air intake.
2. Receiving chamber - wastewater with the highest degree of pollution enters it. Primary water treatment is 45-50%.
3. Aerotank is a chamber in which water is purified by another 20-30%.
4. Airlift with pumping units- provides water transfer between chambers.
5. Air compressors pump air to support biological processes.
6. The third chamber (usually pyramidal) is for water purification and sludge settling.
7. Cleaning chamber.
8. Device for collecting non-recyclable particles.
9. Silt suction hose.
10. Purified water outlet.

Septic tank Topas: the principle of operation of the cleaning system

The Topas septic tank copes with any sewage of household origin. At the outlet, industrial water and sludge are formed, which can later be used as a fertilizer for a garden plot.

Such purification can be achieved through the use of activated sludge containing dozens of bacteria. The cleaning system involves aerobic (life activity occurs only in the presence of oxygen) and anaerobic (can do without oxygen) bacteria.

The entire cycle of operation of the Topas septic tank can be divided into the following stages:

1. Drains enter and accumulate in the receiving chamber.
2. When the level of effluents reaches the limit mark, the float is activated and the compressor is turned on.
3. Air enters the chamber - anaerobic bacteria enter the process.
4. Large fractions of wastewater break up into small particles.
5. Mixed effluents are fed into the aeration tank.
6. Effluent is recycled by aerobic bacteria.
7. Half of the purified water enters the secondary sump. There is a division into silt and water.
8. Effluent is processed by anaerobic bacteria.
9. The sludge enters the stabilization chamber, and the water exits.
10. In the stabilizer chamber, the sludge is divided into fractions. Light fractions are pumped back to the receiver and participate in biological cleaning, while heavy fractions settle to the bottom.

The filter sludge accumulated in the sump must be periodically removed to prevent overflow of the tank and failure of the entire sewer installation

Advantages and disadvantages of autonomous sewage septic tank Topas

Topas septic tank appeared on the market of treatment facilities 20 years ago, has proven itself well in Europe, and in last years won popularity among consumers of post-Soviet countries.

The demand for a treatment plant is explained by its advantages:

Septic Topas: reviews

Among the disadvantages of the Topas septic tank are:

• the high cost of the cleaning system (you can buy a Topas septic tank for no less than 80 thousand rubles);
• energy dependence of the station;
• neglecting the rules for the maintenance and operation of a septic tank can lead to serious damage and costly repairs to the device.

Choosing a septic tank Topas: types and their technical characteristics

The range of Topas septic tanks includes installations for country use, private houses, gas stations (Topas 5-20) and stations designed for wastewater treatment of a small cottage village (Topas 100-150).

The numerical designation in the product name indicates the number of conditional consumers - this is the main criterion for choosing a Topas septic tank

For giving the best option there will be the installation of a Topas-5 septic tank - a cleaning system of low productivity. Such an autonomous sewage system will fully satisfy the needs of a family of no more than 5 people.

Specifications Topas-5:

• the maximum allowable volley discharge of water - 220 l;
• performance of a septic tank per day - processing of 1000 liters of sewage;
• electricity consumption - 1.5 kW / day;
• all installations - 230 kg;
• overall dimensions - 2.5 * 1.1 * 1.2 meters.

If the connection depth of the septic tank is more than 0.8 meters, then it is necessary to install Topas-5 Long

On the site where the pool is located, you need to use a septic tank with a higher capacity - Topas-8 or Topas-10 (depending on the number of people living). Such models can process 1500-2000 liters of water per day.

The letter designations "Pr" and "Us" in the model range of septic tanks have the following decoding:

• Pr - forced water drainage (required at a high level of groundwater occurrence, removal occurs periodically using a pump);
• Us - enhanced water drainage (used if the septic tank is located at a depth of more than 140 cm from the level of the sewer pipe).

The cost of an autonomous sewage system is affected by the performance of the Topas septic tank (the price of a single-chamber septic tank serving 5 people will be significantly lower than the price of a two-chamber model with enhanced water drainage, designed for permanent residence 20 people).

Do-it-yourself installation and connection of a septic tank Topas

Pit preparation

The first step is to choose a place to install a septic tank. Building and sanitary standards prohibit placing the treatment plant too close (less than five meters) to a residential building. However, it is not worth removing too much, as this will increase the cost of building the pipeline.

The installation of the Topas septic tank begins with the preparation of the pit:

There must be free space between the wall of the pit and the body of the septic tank - at least 20 cm

Installation of a septic tank and arrangement of the sewer system

Septic tanks Topas 5 and 8 can be installed in the pit without the use of lifting equipment, that is, manually. There are special holes on the stiffening ribs through which you need to pass the ropes, and carefully lower the septic tank to the bottom of the pit. Align the location of the septic tank using the building level.

The next stage is the supply of the pipeline and the arrangement of the sewer system of the topas septic tank.

The instruction involves the following steps:

The slope of the sewer pipe depends on the diameter of the pipeline. With a diameter of 100-110 cm, the slope is 1-2 cm per meter, and with a diameter of 50 mm - 3 cm per linear meter

Connecting a septic tank Topas

The next step in installing a Topas septic tank is connecting the power supply. To do this, you can use a PVA cable with a cross section of 3 * 1.5.

1. The cable must be placed in a corrugated pipe and laid in a trench near the sewer pipeline.
2. Insert one end of the cable through a special hole into the cleaning station and connect to the terminals.
3. Connect the second end of the cable through a separate machine (6-16A) to the switchboard in the house.

The final stage is backfilling with a dry sand-cement mixture. Sprinkling of the septic tank occurs simultaneously with filling it with water.

The installation is filled up by a third, and filled to the same level with water. Thus, the pressure on the septic tank body is compensated. The process of sprinkling and filling with water continues until the body of the septic tank is completely underground.

Installation and connection of the septic tank Topas: video

Durable and uninterrupted operation of the Topas septic tank is possible subject to a number of rules for its operation and maintenance.

The instructions for the treatment plant contain a list of permissible and prohibited actions.

During the operation of the Topas septic tank, it is prohibited:

• throw construction waste, polymer films and other inorganic compounds into the system;
• pour water containing potassium permanganate into the septic tank;
• pour disinfectants containing antibiotics and chlorine into the sewer system;
• dump large amounts of pet hair into wastewater;
• drain automotive oils, alcohol, antifreeze, alkalis and acids into the sewer.

During the absence of electricity, it is desirable to reduce water consumption in order to prevent overflow of the septic tank chambers and the release of untreated effluents into the external environment.

Regular maintenance of a septic tank is the key to the stable operation of an autonomous sewer. Septic service includes:

Topas septic biological treatment station is a modern installation for arranging local sewage. Despite the high cost, the Topas septic tank has gained popularity among consumers in different countries, thanks to efficient wastewater treatment, ease of use and low operating costs.

Modern people are increasingly thinking about the state of the environment, perceiving it as part of their home. This is especially true for the owners of a suburban area, striving to live in comfort even far from centralized communications. And if local sources of underground drinking water have long become an attribute of the private sector, then house-side treatment facilities began to appear relatively recently. But their popularity is growing.

One of the representatives of such a wastewater treatment plant is the Topas septic tank, manufactured by the Topol-eco group of companies.

The Topas septic tank is a local biological wastewater treatment system with preliminary sedimentation of large suspensions. It is on this principle that centralized sewage treatment plants work, so the Topas septic tank can conditionally be called their miniature.

A step-by-step scheme for processing wastewater can be represented as follows.

Step 1. The entire cleaning process begins with sedimentation in the first chamber, where waste from domestic sanitary equipment flows through the central outer pipe. In addition to sedimentation, already at the first stage, the process of biological decomposition begins due to the fact that oxygen from the air is also supplied to this compartment. From the receiving tank, settled water, thanks to the operation of an airlift equipped with a filter for cleaning large particles, enters the second compartment.

Step 2. The next tank is an aeration tank. In this section, the main work of activated sludge takes place, which consists in the decomposition of pollutants due to the process of respiration of microorganisms. Therefore, air is supplied here by the compressor. In addition, some particles become silted, which will allow them to be removed during the sedimentation process in the next chamber.

Step 3. The third compartment is a pyrami do sump. In it, sludge from the water is deposited, and purified water is discharged. At the outlet of the secondary clarifier, the liquid also passes through an additional filter.

Step 4. Effluent treated to almost 100% of the level is discharged into a receiving tank, reservoir, ditch, etc. High level purification allows you to use water for watering the green spaces of the site.

Step 5. Light suspended sludge from the secondary clarifier is fed to the beginning of the cycle, and heavy sludge is pumped into the fourth chamber, called the sludge stabilizer.

Such a simple scheme allows, without much human intervention, to obtain high-quality wastewater treatment, which is based on the usual natural process of biological decomposition.

Pros and cons of the Topas septic tank

The only drawback of the Topas septic tank is the energy dependence associated with the operation of the compressor. But the lack of uninterrupted power supply on your site will make it impossible to install any biological treatment plant.

The advantages of the Topas septic tank are several:

• lack of noise and unpleasant smell;
• compact design;
• low level of electricity consumption;
• simple installation scheme and operation process;
• large range of models.

Model range of septic tanks "Topas"

The models of this cleaning station differ in capacity, which depends on how many people will operate the sanitary equipment of a residential building.

Note! For a house with a large amount of sanitary equipment, it is better to purchase a septic tank with an increased capacity.

The numerical indicator in the model name indicates the number of users for which the septic tank is designed. Also, each model provides two main modifications, differing from each other in the height of the input and output of drains, and hence the height of the septic tank itself:

• the Standard model is suitable for the case of introducing a supply pipe at a depth of 0.4 - 0.8 m;
• the Long model is applicable when it is necessary to deepen the sewer pipe by 0.9 - 1.4 m.

There is modifications with forced withdrawal of treated water. They are equipped with a pump.

For private houses, 5, 8 and 10 models of the Topas septic tank are most often used, so we will focus on a brief description of these particular varieties. In order not to repeat ourselves, we indicate that all these models have the same width, which is 1.2 m.

The Topas 5 septic tank is designed for a salvo discharge of 0.22 m 3, and a productivity of 1 m3. Weight, depending on the height of the tank and the presence of a pump for forced pumping of treated wastewater, ranges from 0.23 - 0.31 tons. The height of standard models is 2.6 and 2.5 m for gravity and forced evacuation of wastewater, respectively. The height of the elongated model is 3.1 m. The length of the septic tank is about 1 m. The estimated cost, depending on the height of the tank and the presence of a pump, ranges from 80 thousand rubles.

The Topas 8 septic tank copes with a salvo discharge of 0.44 m3 and has a capacity of 1.5 m3. The weight of the septic tank of this model, depending on the modification, ranges from 0.35 - 0.41 tons. The length is about 1.5 m, and the height for standard systems is approximately 2.5 m, and for elongated systems - 3.1 m. Price range is 85-105 thousand rubles.

Septic tanks "Topas 10" successfully operate with a capacity of 2 m3, and the volume of a volley ejection can be equal to 0.76 m3. The weight of the container with equipment varies for modifications in the range of 0.50 - 0.62 tons. The height of this septic tank is the same as that of the eighth model, and the length is 2.1 m.

In addition, the Topas 10 septic tank, in addition to standard models, has an elongated tank with a reinforced structure that can withstand strong ground pressure.

We also note that among the Topas treatment plants there are varieties capable of serving several houses and even small populated areas with up to one and a half hundred people. In this case, the installation must be left to professionals. Small structures can be installed independently.

Installation work

Topas 8 - autonomous system biological wastewater treatment

Before the preparatory and installation work themselves, it is necessary to correctly select the location of the septic tank in accordance with certain conditions:

• the distance to the treatment plant from residential buildings should be at least 5 m, but not exceed the threshold of 10-15 m;
• if the conditions of the area force you to install a septic tank further from the house, then it is recommended to install an inspection well on the external sewer pipeline;
• an inspection well will be required if the supply pipe has bends of more than 30 degrees, so it is better that the pipeline does not have turns.

Having decided on the place, you can proceed to the installation work.

Step 1. Dig a pit using equipment or manually. The width and length of the pit for the container should be approximately 50-60 cm larger than the corresponding dimensions of the septic tank. The depth of the pit is made equal to the height of the septic tank, even though a fifteen centimeter sand layer will be poured at the bottom. After all, it is 0.15 m that the septic tank should rise above the ground to facilitate its maintenance and prevent the station from flooding during the spring flood. If an additional concrete base is still installed at the bottom, then its height must be taken into account, determining the depth of the pit.

Step 2. To prevent shedding of the pit, its walls are reinforced with formwork.

Step 3. At the bottom of the pit for the Topas septic tank, a sandy backfill 15 cm thick is made, which must be leveled to the mounting level. If the septic tank is installed in places with water-saturated soil or with a seasonal rise in GWL, then it is important to additionally fill or install a ready-made concrete base at the bottom of the pit. The septic tank is further attached to it.

Step 4 Holes for pipelines are made in the wall of the tank.

Step 5. A septic tank is released into the prepared pit. If we are talking about 5 or 8 models, then no more than 4 people should be involved to carry out all the work. To do this, they thread slings through the eyes on the stiffening ribs of the container, holding them for letting the septic tank go into the pit.

It is important to check using building level whether the septic tank is level.

Step 6 Prepare a trench for laying a pipe from the house to the septic tank. The depth of the ditch must ensure that the pipeline passes below the zero ground temperature point typical for the winter period. If this fails, then the pipe will need to be insulated. A sand backfill is also made at the bottom of the trench, which is leveled in such a way that the laid pipe runs at a slope of 5-10 mm per linear meter.

Step 7 Lay the supply pipe and connect it to the septic tank through the pipe inserted into the prepared hole in the wall of the container. All connections are additionally sealed with a special plastic cord that comes with the station. To do this, use a building hair dryer. At the same stage, the septic tank is connected to the power cable and compressor equipment is installed.

Step 8. Prepare a ditch for a pipe that already drains waste after cleaning into a receiving tank, pond, filtration well and other discharge points. A pipe is laid at an angle in it, if the removal of water is planned to be carried out by gravity. For forced evacuation of the liquid in the slope is not necessary. The outlet pipeline is connected to the septic tank, all connections must be tight.

Step 9. Fill the septic tank with sand or a mixture of cement and sand. At the same time, the tank itself is poured clean water, its level should be 15-20 cm higher than the backfill level. Every 20-30 cm, the backfill is carefully rammed manually. The space between the top 30 cm of the septic tank and the foundation pit is filled with fertile soil and the turf is laid back around to restore the landscape.

Note! The sand in the backfill must be unsifted so that during the freezing of the soil, large particles do not damage the walls of the septic tank.

Step 10. Ditches are filled up with inlet and outlet pipes laid in them.

Rules for operation and maintenance

After installing all the constituent elements of the Topas cleaning system, start-up work is carried out. For the first time, it is better to leave this procedure to professionals, watching their work.

Note! It takes about three weeks to form the required biomass of activated sludge. To speed up this process, you can add ready-made river silt to the septic tank.

Ongoing maintenance includes the following activities.

Note! Stabilizer sludge is a good fertilizer for your green spaces.

The complex service also includes cleaning the coarse fraction filter and checking the float mechanism of the first chamber, which is responsible for turning the compressor on and off. For revision, you just need to forcefully raise and release the float and see how the compressor works.

It is also important to clean the pumping equipment compartment, after removing the compressors from there, rinse all hoses and pipes.

Note! Before reinstalling the compressors, thoroughly dry the compartment.

After completing all the cleaning procedures and installing the equipment in place, it is necessary to fill the septic tank with clean water by two-thirds. You can proceed to further operation.

Otherwise, the Topas septic tank works effectively offline.

Video - The principle of operation of the septic tank "Topas"

The Topas treatment septic tank, according to the principle of operation and device, is fundamentally different from its counterparts from other Russian manufacturers in terms of maximum productivity, safety and a high degree of domestic wastewater treatment. Each model is designed for a specific number of people living, which is especially convenient when choosing equipment.

The aeration station "Topas" is an autonomous treatment system used for private houses and properties in a suburban area where there is no centralized sewage system. Small modifications are designed to serve families consisting of several people. Large models can be installed for hotel complexes, offices, small businesses.

Based on the number of people, the number of plumbing fixtures involved in the water supply is calculated, and then the appropriate treatment equipment is selected.

The principle of operation is based on the biological cleaning of waste pipes from pollution. It uses oxygen and biomass of special aerobic bacteria. Thanks to the vital activity of these microorganisms, waste is decomposed into clean water and useful sludge. Both can be used in home gardens for various needs.

The main advantages of the building are:

• High cleaning ability - up to 98%;
• Economical electricity consumption;
• Lack of noise and unpleasant odors in the area;
• The compactness of the equipment;
• Sealed polymer housing, not subject to temperature changes, corrosion and mechanical deformation;
• Easy operation management due to automation;
• Long service life - up to 50 years;
• Easy installation of the cleaning system.

The structure can be placed anywhere and does not violate general view territory, since the body is placed in the ground, and only the hatch necessary for maintenance remains on the surface.

Technical device of the septic tank "Topas": scheme

In order to more clearly imagine the work of aeration equipment, one should take a closer look at its device.

The septic tank has a body in the form of a cube, equipped with a square hatch. Inside it are sections, each of which has a specific function. The compression device ensures the delivery of air into the body for oxygenation of wastewater.

Inside the case are the parts necessary for the operation of the system:

• Receiving chamber where waste water resides;
• Jet pump to move water to other departments;
• Water purification tank containing water and activated sludge;
• Secondary cleaning chamber;
• Container for purified liquid;
• Pneumatic or mechanical aerator;
• Hose designed to remove silt particles;
• Discharge device for water purified from impurities.

All these elements ensure the continuous operation of the structure.

Purified water can be discharged by gravity or with the help of an additional hose in some models.

How the system works: the structure of the septic tank

The autonomous system operates year-round, including winter time. The housing maintains an optimal temperature that supports the life of aerobic bacteria.

The workflow is very simple.

It consists of several phases:

• Wastewater enters the receiving chamber, settles, and primary treatment begins here, due to the oxygen supplied with the help of aerators.
• After filtration, the water passes into the aeration tank, where the contaminants decompose due to the action of aerobic bacteria;
• Then the water goes to the pyramidal sump, where the silt particles settle, the water purified from sewage is removed, passing through the filter;
• After that, it can merge into a specially made well and be used for technical needs or irrigation;
• The sludge enters the stabilizer.

Despite the simple structure of the septic tank, autonomous sewage is very efficient in operation and, moreover, safe for humans, animals and the environment.

Aeration septic tank "Topas": do-it-yourself installation

To place the equipment on your territory, it is not necessary to call a team of professionals. Installation of a septic tank can be done by hand.

To do this, you will need to perform the following steps:

• Dig a pit a little larger than the body of the model - a distance of 200 mm should be left between the septic tank and the soil;
• Then sand and gravel are poured onto the bottom, the surface is leveled using a level;
• Next, you should bring a sewer pipe to the sewage equipment and weld it;
• The electric cable is brought to the septic tank - it must be insulated, it is advisable to place it in a flexible plastic pipe and lay it next to the sewer pipe;
• Then, any post-treatment facility with a septic tank should be connected using a pipe segment;
• Lastly, aerators and a pump are mounted in the housing;
• The pit is covered with soil, to balance the position of the structure, the pit is also filled with water, which is gradually displaced as Topaz is used.

In addition, it will be necessary to install the ventilation necessary to neutralize the methane. Risers can be located next to the septic tank and the house in the place where the sewer pipe exits.

Self-cleaning and maintenance of the Topas septic tank (video)

The choice of a septic tank is always associated with a certain set of plumbing, so it is not difficult. High-quality equipment and its price are quite commensurate, because it will last for several decades without the need for complex maintenance and management. A high degree of purified water and fertile sludge can be used for a vegetable garden and a garden, while the structure does not interfere at all on the site, remaining practically invisible. All these positive traits made the technique in demand in the suburbs.