Such soil belongs to the category of problematic soil and is considered “heavy”, not only directly, but also in figuratively. Excavation work carried out in areas with clay soil is characterized by its specifics. How is it expressed in relation to the installation of a biorefinery station?
Local structures of this category can be installed on any soil. And this is one of the advantages of such septic tanks for autonomous sewerage. However, there is a point that is not taken into account by all land owners who, in an effort to save money, try to carry out the entire cycle of activities on their own. Installation of a biorefinery station is carried out on clay soils only after a series of engineering calculations. Therefore, invite a specialist (at least for professional consultation) - more than rational decision. Otherwise, during operation of the septic tank deep cleaning Problems may arise that you cannot cope with on your own.
So what are the features clay soil? The main difficulty is the minimal absorption of liquid due to the increased density of the earth. What does this mean in practice?
- The removal of clarified liquid must be carried out forcibly. On clay soils it is not advisable to organize a natural discharge. Or rather, it’s impossible. Therefore, when choosing a biorefinery station model, you need to take this nuance into account.
- Groundwater is located quite high. Since it is necessary to prepare a pit for the installation of the station, there may be a problem with its constant flooding. Even with forced drainage, it is unlikely to be completely resolved.
- On clay soil, any septic tank, including a station, cannot be placed at a significant depth. This means that you will need additional insulation housings. For most regions of the Russian Federation, this topic is more than relevant, considering how low the thermometer drops in winter. In relation to a biorefinery station, another difficulty lies in the fact that for bacteria to function normally, they need to be provided with maximum favorable conditions. Consequently, on this point, it is necessary to correctly calculate everything - the type of heat insulator, the thickness of the layer, the method of laying it.
Many owners country houses I'm wondering if it's possible to make a septic tank on clay. The main problem with the device treatment plant on this type of soil is that pre-purified wastewater, after passing through the septic tank, is discharged into the ground, and clay does not pass and filter water well. However, even on clay soil, an autonomous treatment plant can work effectively and for a long time if it is properly designed. In our article we will look at different types septic tanks that can be made on clay soil, as well as the features of their design and selection.
To make it easier for you to understand what kind of septic tank is needed for clay soils, you need to study the characteristics of this soil. To arrange effective system sewerage, wastewater after treatment in a septic tank is discharged into the ground. The main feature of clay soils is poor absorption capacity. The earth does not absorb liquid well. This results in wastewater remaining in the treatment plant longer.
It is important to know: sandy soil absorbs 90 liters of water per day, the absorption capacity of clay soils is 25 l/day. And pure clay absorbs more less water– 20 l.
That is why, when installing a septic tank made of concrete rings, plastic or metal containers, it is necessary to organize effective drainage. This can be a drainage well made of concrete rings without a bottom with a filter layer or a filtration field.
What septic tanks can be used in clay?
If your dacha or Vacation home are located on an area with clay soil, then to process the wastewater coming from the house through the sewer, you can use the following types treatment facilities:
- Storage tanks. For these purposes, you can use sealed plastic containers or Eurocubes. However, stainless steel metal tanks are also suitable for clay soils. You can also make a sealed well from concrete rings if the groundwater level on the site is high. For a small private house, you can make a brick drainage well, provided you use the right technology.
- Wastewater treatment plants with soil treatment. This is a fairly effective, budget and simple option for a small country house, built on clay soil. The well of such a treatment facility can be made of concrete rings, brick or metal, that is, any material can be used for such soil.
- Units with biological treatment - this is the most reliable and effective option for clay soils, suitable for a private house of any size. However, such a septic tank on clay will have the most complex design, so its choice should be made if you have the money and time to complete it.
Important: sewerage from a country house to clay soil can be discharged into a septic tank of any design. It is important to properly design and install a treatment plant on such soil. In this case, the choice should be made taking into account the productivity of the structure, the required degree of wastewater treatment and groundwater treatment.
Storage containers
If you decide to equip the sewer system of a private house using a storage tank, then you need to make a sealed structure. For these purposes, you can use plastic containers, Eurocubes, steel barrels or welded cubes, structures made of concrete rings or bricks.
It is quite easy to carry out such a cleaning installation. It is enough to dig a pit, concrete the bottom and install containers or concrete rings. However, if your area has a high groundwater level or there is a well near the storage tank, then using such a design is not recommended.
Structures with soil post-treatment
These simple treatment facilities are very similar to storage tanks, but without a bottom. The structure of the well itself can be made of concrete rings, bricks or bottomless water. A drainage layer is installed at the bottom of the structure.
To make a drainage filter, you need to use geotextiles, sand and crushed stone. The thickness of the filter layer is 30-40 cm. When passing through this filter, the wastewater is cleared of large fractions and enters the soil.
If there is a well nearby on your site, then this design of the treatment plant is also not suitable. When installing this septic tank, you need to know the groundwater level, because the bottom of the filter layer cannot approach the aquifer closer than 1 m.
Units with biological purification
These are the most reliable and efficient treatment facilities that can be installed regardless of the water supply system on the site. These autonomous biological treatment stations purify wastewater so effectively that the water can then be used to water the garden, drained into open reservoirs, or taken for technical needs.
Usually these are multi-chamber products, where the wastewater directly from the sewer system is divided into heavy and light fractions. Then the clarified water undergoes a process of biological purification using bacteria (anaerobic or aerobic).
Design features
Since any septic tank design can be used on clay soil to sewer a country house, the construction scheme will be standard. However main feature Clay soils are that they are mobile soil. Therefore, it is worth considering some design features of the septic tank.
The thing is that when the soil begins to thaw after the winter cold, the characteristics of such soils change somewhat and they can push the septic tank to the surface. This is especially true for soils with high groundwater levels and septic tanks made of light materials. That is why, when installing a septic tank in clay, it is necessary to provide additional fasteners in the soil. If the well of the treatment plant is made of concrete rings, then it is enough to simply fill it in the pit without fixing it.
The choice of method for fixing the septic tank in the pit depends on the design of the housing. If there are no protrusions on the surface of the tank, then steel cables. If there are loops or protrusions on the body, then reinforcement outlets can be tied to them, which will be laid in a concrete pad at the bottom of the pit.
Also, the filtration system for a septic tank on clay soil has some features. When installing a septic tank in clay, it is better to arrange double drainage, that is, two filtration fields. In this case, the drainage should take the form of a two-stage trench, in the upper part of which pipes will be laid, and in the lower part there will be a drainage layer 300 mm high of gravel.
Installation features
To perform more efficient design For a septic tank, it is recommended to use two chambers and a filtration field. This way you can avoid excessive overfilling of the tank and at the exit from the treatment plant you will receive the most purified water possible. After you have decided on the material of the chambers, you can start digging a pit and further work, which are executed in this order:
- When choosing a location for a septic tank, you can observe the minimum recommended gaps from a residential building and sources drinking water(7 m), since clay does not allow water to pass through well. The size of the pit for the treatment facility should be 20 cm larger than the septic tank structure itself.
- When digging a pit, you need to know at what depth the clay layer ends. If he is more three meters, then the work will be complicated by the fact that the drainage layer will have to be carried out at a considerable depth. It is also worth considering that the septic tank containers are connected to each other by an overflow, so they should be located at a distance of 15-20 cm from each other.
- Together with the pit, they dig a trench for the gasket sewer pipe from home to treatment plant. At the same time, the slope of the bottom of the trench from the house to the septic tank is observed, taking into account that for every meter of length the decrease is 2 cm.
- Depending on the containers used, the bottom of the pit can be concreted before or after installation. If you use plastic sealed tanks, the bottom is concreted and reinforced before they are installed. And after installation, these tanks are attached with hummocks to the valve outlets. When using concrete rings, the bottom can be concreted after they are installed in the pit.
- To make a filter layer at the bottom of the second chamber, sand and crushed stone are used. First, sand is poured and compacted in a layer of 10-15 cm, then backfill is made of crushed stone 25-30 cm high. If you use a filtration field, the bottom of the second chamber is also concreted, and the wastewater is discharged to the filtration fields.
- Next, install an overflow pipe connecting the two containers. It should exit the first chamber 40-50 cm below the entry point of the sewer pipe. Thanks to this, heavy components of the wastewater will settle at the bottom of the first chamber, and pre-purified and clarified water will flow into the second tank.
- Mounted ventilation pipes from the cameras.
- After this, the plastic containers are insulated with foam. Concrete rings do not require insulation.
- The containers are covered with lids with hatches for cleaning.
- Now backfill the pit manually. The soil must be compacted every 15-20 cm. The manhole cover must remain above the surface of the ground.
The filtration field is made depending on the groundwater level in the area:
- at low groundwater levels, semi-buried filter cassettes or filters are used;
- at high groundwater levels, surface filtration on sand and gravel beds is used.
Important: the size of the filtration field is directly related to the daily volume of wastewater from the house.
One square meter The filtration field is capable of serving 0.5 cubic meters of wastewater. You can purchase ready-made filter wells based on geotextiles or make the field yourself:
- After digging up soil from the field, a pipeline is laid from the last chamber of the septic tank to the filtration field. The laying depth is 70-120 cm from the ground surface, but not less than 1 m to the groundwater level.
- A drainage mesh is laid at the bottom of the field. Then a layer of sand and crushed stone is made. The height of the layer should be such that it rises above the inlet pipe by no more than 50 mm. All pipes with holes are laid with a slope of 1 cm per meter of length.
- The drainage pipeline is insulated using foam plastic or a wooden box.
Choosing a septic tank for clay soil and installing it is complex tasks, requiring compliance with a number of rules. Incorrect installation of such structures on loam can cause deformation of the septic tank and disruption of its operation.
It is difficult to install a septic tank on clay, because... the characteristics of this soil do not predispose to rapid drainage and cleansing Wastewater. Clay does not absorb water well. Wastewater is retained in the tank. Sandy soil can absorb up to 90 liters of water per day, while loam soil can absorb only 25 liters. Pure clay is characterized by lower water absorption rates. In addition, clay soils differ high density and heavy weight. When arranging an autonomous sewer system, these features must be taken into account.
Why do septic tanks installed in clay become deformed, and how to avoid this?
Most often used when installing septic tanks plastic containers large volume. They are good option for many types of soils, but they are not entirely suitable for clay. Possessing high density and weight, clay often deforms even thick plastic containers during seasonal temperature fluctuations. In some cases, deformation of even metal containers is possible. In addition, septic tanks in clay soil often deformed due to soil movements. This happens especially often if groundwater lies too close to the surface.
When planning to install a septic tank in clay soil, you need to take into account the danger of possible deformation of the container. To prevent the occurrence of such a problem, it is advisable to use rigid materials for the construction of the structure, including concrete rings, plates, etc.
If desired, you can also use plastic containers. But to protect them from soil movements, it is necessary to make a special structure made of concrete or strong wooden sheathing. This will avoid damage to the integrity of the container due to soil pressure. If the level groundwater low, you can use metal reinforcement or corners to make the sheathing.
What septic tanks can be used in clay?
When installing a septic tank on clay soil, it should be taken into account that it is almost impossible to create high-quality filtration fields, therefore, from classic multi-level systems should be refused. There are several options for autonomous sewers that can be used effectively.
Storage containers
The simplest and cheapest option for a septic tank, suitable for installation in clay soil, is a storage system. In clay soil conditions and to save money on pumping water in the future, you can use a complex storage system, consisting of several containers connected to each other. Such cleaning systems can be created based on:
- concrete rings;
- wells lined with brick;
- large metal barrels;
- plastic containers, etc.
Such a septic tank for clay soil is an analogue cesspool and requires systematic pumping out of accumulated wastewater using a sewage disposal machine.
With soil purification
Septic tanks, consisting of several storage tanks and an artificially created filtration field, can reduce the cost of pumping wastewater. In this case, some part of the already settled wastewater will enter the filtration field and go into the soil. The design in this situation will be simple. Several containers are connected in series so that heavily contaminated wastewater remains in the first one, and the already settled water penetrates into the next container.
There doesn't have to be only 2 containers. Some owners of personal plots connect 3-4 containers together at once. This makes it possible to ensure that almost clean water enters the last cavities of the septic tank. Difficult moments Arranging such a system involves preparing the site and installing a filtration field system.
Due to the presence of clay in the place where the filtration field will be located, it is necessary to dig a pit 1 m deeper than the bottom of the hole intended for installing the system. Gravel or crushed stone, as well as a layer of sand, are poured into the bottom of the pit. Perforated pipes are laid inside such a cushion so that purified water from the last container can be discharged to the filtration field. It must be taken into account that there must be at least 50 cm of crushed stone and sand on top of the pipes.
During the shrinkage process, the filtration field can become heavily clogged with clay and cease to perform its function. To delay such an unfavorable outcome, the finished filtration field should be covered with geotextiles. Clay can be poured on top of this material. This will prevent the clay from swelling and clogging the cavities between the crushed stone.
For biological treatment
Closed septic tanks with biological treatment are very popular among owners of sites with clay soils. Such systems are autonomous sewerage stations. They provide a high degree of purification, so in the future the resulting water can be used for technical needs and for irrigation of the site.
Such autonomous sewers are multi-chamber products, where the wastewater is immediately subjected to fractional division and settled. Clarified wastewater is further purified by special bacteria that process all organic compounds present.
Design features of a septic tank for clay
The physical properties of clay soils change slightly during periods of freezing and thawing. This often causes the septic tank to gradually push to the surface. This problem especially often arises when installing septic tanks that were made of lightweight materials, including plastic and metal.
To prevent this effect from occurring, it is necessary to fix the structure in the pit. For additional fixation, they are often used metal fittings And concrete mortar. If the surface of the container is equipped with special holes, you can use metal cables to fix it to the bottom of the pit.
In addition, to prevent the container from moving, it is recommended to install a thick substrate of gravel and sand. It is also possible to manufacture concrete slab, which will serve as a base. When pouring it, you can make “ears”. With their help, you can later more securely attach the septic tank to the base.
By doing earthworks When installing an autonomous sewer system, all safety measures must be observed, since clay can quickly collapse. It is best to dig a hole for the septic tank at least 1.5 m wider and longer than required. This will avoid surprises due to clay collapse.
Features of installation on clay soil
When planning to install a septic tank on clay soils, you must comply with the sanitary requirements for the location of autonomous treatment facilities. The distance to the house and other permanent buildings must be at least 20 m.
In addition, if a septic tank for clay soil has a filtration well and will purify the water not only through the operation of a sewage disposal machine, you need to take into account that the distance to the well or other water source must be at least 50 m. This will prevent contamination of drinking water by wastewater.
It is best to begin installation when the weather has been dry for a long time. This will ensure a reduction in groundwater. When digging a pit, all precautions should be taken. The height of the pit must be at least 70 cm greater than the height of the selected septic tank. A 10 cm layer of sand is placed at the bottom of the pit. After this, a 30 cm layer of gravel is poured. Laying geotextiles on top of this is recommended.
After this, a tied reinforcement mesh required for pouring the concrete base. If necessary, a wooden or metal sheathing is formed to protect the septic tank from compression. After the bottom of the pit has been prepared, you can proceed to installing the septic tank structure. Be sure to secure the container with ropes or metal rods. After this, you need to install all the communication pipes, fill the cavities around the septic tank and compact the soil.
Installation of local treatment systems for sewage (septic tanks) is often complicated by mining and geological conditions (soil composition) and high level groundwater.
These reasons create problems with the discharge of treated wastewater into the ground. The most difficult thing is to install a septic tank on clay, which has a minimum coefficient of filtration of liquids.
The main problem at this stage is related to the fact that almost all clays (90%) belong to soils prone to frost heaving. It is because of this reason that the installation can be squeezed onto the surface, so it is necessary to resort to additional fastening of the local treatment plant during the installation process. Most often, a so-called bandage made of steel strips or cables is used for this, which encircles the septic tank and is attached to concrete base in the pit.
Considering that on clay soils drainage systems(filter fields) in many cases only work in upper layers soil, you have to resort to shallow placement of a septic tank.
In this case, it is necessary to provide measures for insulating the structure:
Insulating a septic tank with glass wool
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- In the simplest case, they resort to pouring an additional layer of soil above the topography (forming a mound above the installation site of the septic tank).
- It is more effective to insulate the treatment plant with special heat-insulating materials, the choice of which is quite wide. The most affordable (cost) method is filling the container with expanded clay. The use of polystyrene foam (preferably extruded) or polyurethane foam is considered more effective. In addition, active protection systems against exposure are increasingly being used. negative temperatures. To do this, use a heating electrical cable, thermal power which will reliably protect the septic tank from freezing even in harsh climatic conditions.
Discharge of treated wastewater
The main problem for those who decide to install an autonomous sewage system and install a septic tank in clay soil is the difficulty of draining treated wastewater. Such soil has minimal filtering capacity, which creates a number of sometimes intractable problems.
There are several main ways to remove treated wastewater from a septic tank in such conditions.
It is used if the soil on the site does not accept water at all. In this case, the entire volume of treated wastewater enters a sealed container or well, from which it is then pumped out using sewage disposal equipment or drainage pumps.
The disadvantages of this method include the need to construct a large-volume container, otherwise pumping will have to be performed very often. But if there is no other way out, this technology has to be used.
Increasing the drainage area
There are several varieties of this technology, but they all boil down to the need to increase the filtration area in order to ensure the removal of the required volume of treated wastewater even with minimal drainage capacity of the soil.
- The device of a number of serial drainage wells, in this case it is necessary to use rings of the largest possible diameter.
In practice, systems of two or three overflow drainage wells are used, which can fully meet the needs of a family of 3-4 people.
To increase the filtering capacity of wells, they resort to drilling additional drainage wells. This method allows, in some cases, to reach filtering soil horizons, which will help to significantly increase the productivity of the structure. Drilled wells must be protected with casing pipes, and at their mouth install the simplest strainer, which will prevent silting of additional drainage.
- Install a septic tank in clay with your own hands It is also possible with the construction of filtration fields of a large area. This method is used at high GWL (groundwater level).
The most productive is a drainage system using corrugated plastic pipes and geotextiles. Pipes of this type They are characterized by increased strength, they are able to provide effective removal of treated wastewater. And geotextiles prevent siltation of the system.
To increase the efficiency of the filtration field, laying two-level drainage is often used. In this case, a number of lines (drains) are laid close to the surface, and the main part is buried as deep as the groundwater level allows.
The filter line is laid in pre-prepared trenches, which are covered with geotextile fabric. For filling from crushed granite(it is not recommended to use another one due to the tendency to erode) with a thickness of at least 20 cm are laid drainage pipes. They are also covered with a layer of crushed stone on top, which can significantly increase the volume of discharged wastewater. The entire resulting system is covered with geotextiles, which will ensure the durability of the line.
To ensure filtration of wastewater in clay soil conditions, it is necessary to lay out filtration fields of significant area.
Of course, installing septic tanks in clay involves a significant increase in the volume of work performed during installation. But to provide effective work installations of local wastewater treatment even in such conditions is quite possible.