Filtration well. Filter well: purpose and device. Step by step instructions for building

Inadequately treated domestic wastewater is one of the main pollutants environment. From a relatively large mechanical suspension, purification is quite simple - you just need to pass the drains through a layer of sand or other microporous material.

Not so easy, however, the situation is with the removal of contaminants. biological nature, which require the use of complex (and expensive) filter blocks, whimsical, implying regular replacement of the reagents used, etc. Similar methods have proven themselves relatively well in industry, but for personal needs, when installing sewage in a private house or in the country, it is desirable to have something simpler and cheaper. And there is such an option!

Need to apply for biological treatment only natural materials. After such treatment, clarified domestic wastewater can be used for irrigation at the same country or personal plot. Of the several options for this solution, filtering wells for a septic tank have proved to be more accessible and simpler than others in practice.

Filter well device and installation features

Despite the general simplicity of the device, they are able to absorb up to 80% of harmful organic impurities (which is quite acceptable as the second stage of wastewater treatment following mechanical filtration). The specific performance of the filter well is determined by how porous the filter filler is (gravel, crushed stone, metallurgical slag, stones, expanded clay and other similar materials).

First of all, think over the strategy of the entire cycle of work on creating a biological treatment well, carefully prepare for construction - this is the only way to avoid surprises and unpleasant surprises. The technology allows the use of such a solution only on sandy (sandy loamy) soils, and if the groundwater passes no higher than a line of two and a half meters below the surface.

The treatment plant in our case is represented by a deep shaft, into which a well is, as it were, “inserted”. The structure is made up of walls top floor, as well as the bottom, which includes a filter layer.

Since we are talking about an object of increased biological hazard, strict requirements are imposed on the placement of filter wells for sewage.

1. So, the foundation of the nearest residential building cannot be less than ten meters.
2. If there is a drinking well on the site, then according to SNiP 2.04.03-85, the distance to it should be at least twenty-five meters.

How to calculate the filtering area of ​​a well

When all sanitary requirements taken into account, it is time to calculate the required filtering area of ​​the well. Adding the area of ​​the bottom with the areas of all the walls, and multiplying by the height of the filter material layer, we obtain the total filtering surface area of ​​the well. In no case should it be more than four square meters! And we limit the depth to two and a half - three meters, taking into account the fact that groundwater should be at least 1 meter below the bottom of the well.

For example, if a well is made of rings with a diameter of 1m, then the bottom area will be 0.76m2. At maximum allowable height bottom filter of 1 m, the area of ​​the well walls with which the filter material comes into contact will be 2 * 3.14 * ring radius * height 1 m = 3.14 m2. The total filtering surface of the well will be 0.76 + 3.14 = 2.39 m2.

The assessment takes into account not only the GWL groundwater level determined at a particular moment, but also seasonal fluctuations (after all, groundwater reaches its highest point when the snow cover melts in spring). If there is no data on the location of groundwater, it should be determined by digging holes.

The optimal place is considered to be where the manifestations of moisture in the pit are noticed one and a half to two meters below the surface level. If suddenly water is shown when not even a meter has been passed, then such a place is categorically unsuitable and the filtration well will have to be abandoned.

The required site has been dug up. It's time to take up the delivery of slag or gravel, crushed stone or broken brick, expanded clay. The size of the fractions for the filter layer (bottom filter) should be no more than three centimeters. If this condition is met, sludge is deposited on the filter particles from household wastewater, which becomes a medium for the development of colonies of microorganisms. Biobacteria, providing themselves with substances taken from wastewater, produce by-effect decomposition of organic matter accumulating at the bottom (precipitating).

The filtered drains go through the bottom filter and the perforated walls of the well into sandy soil or sandy loam to groundwater. From above there are layers (in order) - fine-grained rubble, broken bricks and slag from dumps. The same materials close the gap from the wall of the well to the wall of the mine.

The ground layers that separate the bottom of the well from groundwater complete the release of wastewater from harmful impurities of biological origin.

By the way, the area is needed to calculate not only the amount of filter materials used, but also the ability of the filter layers to transfer the load. So, sandy loam can “process” forty liters of wastewater per day into square meter, the sand will pull twice as much (and this is already the limit, you simply cannot find anything better). The dimensions of the well at various wastewater flow rates are given in the table.

The shape of the well does not play a special role; you can select it at your discretion. But the materials for the walls have already been tested by many years of practice: this is monolithic concrete, prefabricated perforated reinforced concrete, reinforced firing bricks (burnt bricks), rubble stone.

The design of the filter device must be selected depending on the type of soil and on the level of groundwater (see table 6).

On sandy soils and sandy loams, a filtering well is arranged (when groundwater occurs at a depth of at least 3 m) or underground filtration fields (at a water level of 1.5-2 m). After passing through such a filter, wastewater seeps through the ground, where it undergoes additional treatment, to underground groundwater.

Filter well

So, if the conditions allow, that is, the soil has filtering properties (sandy or sandy loamy soils) and the groundwater is low, it makes sense to arrange a clarified wastewater filtration well next to the septic tank (settlement chamber).

On poorly permeable and water-resistant soils, sand and gravel filters of complete cleaning are arranged, after which harmless water is discharged into a reservoir or onto a relief.

When too high level groundwater filtering devices have to be raised higher and a pump used to lift wastewater from the septic tank.

The general scheme of local sewerage in this case looks like that shown in Fig. 61.

Rice. 61. : 1 - residential building with internal sewerage; 2 - septic well; 3 - filter well; 4 - exhaust riser; 5 - sewer pipe.

Rice. 62. Filter well, mounted from reinforced concrete rings(dimensions in mm): 1 - water-breaking board; 2 - a manhole made of a reinforced concrete ring with a diameter of 700 mm; 3 - cast-iron hatch type "L"; 4 bottom wooden cover; 5 - support ring under the hatch; 6 - ventilation riser; 7 - floor slab; 8 - upper reinforced concrete ring; 9 - lower reinforced concrete ring; 10 - backfill; 11 - holes.

Rice. 63. (dimensions in mm): 1 - mine; 2 - well wall; 3 - holes with a diameter of 50 - 60 mm; 4 - concrete screed; 5 - open bottom of the well.

As can be seen from the above diagram, the sewer pipe discharges wastewater from the house by gravity into the settling chamber (septic tank), from where they also enter the filter well by gravity. The filtered water seeps down to the groundwater. It should be noted that the brownie fan pipe, and both cleaning chambers are equipped with an exhaust hood to remove formed in sewer system gases.

The filter well, like the septic well, is a shaft about three meters deep, inside which a well is made of rubble stone, brick-iron ore or reinforced concrete rings.

The device of a filter well made of reinforced concrete rings with a diameter of 1500 mm is shown in fig. 62.

The shaft is dug out completely to a given depth. Its diameter should be 800-1000 mm larger than the diameter of the rings (see Fig. 63). At the bottom they arrange concrete screed along a compacted contour in the form of a ring around the perimeter of the shaft, leaving open ground in the center, along the inner diameter of the concrete ring. Thus, the lower edge of the ring rests on concrete base, and the bottom of the chamber remains unconcreted and does not prevent sewage seepage.

In the lower reinforced concrete ring, 80 holes with a diameter of 50-60 mm are drilled with a puncher with a horizontal and vertical step of 100-120 mm. If the ring is cast on its own, then easily removable plugs or nozzles for the holes are laid in the formwork in advance. If the wall of the well is made of stones, gaps are left on the layer, and if it is made of brick, the masonry is made in half a brick (on the layer) in a checkerboard pattern, leaving gaps between adjacent bricks of 35-45 mm in each row.

At a height of 1 meter, the well is covered with filter material (gravel, crushed stone, sintered slag, broken brick with a fragment size of 10-70 mm). Outside, between the walls of the shaft and the concrete rings, the same backfill is made.

The inlet pipe enters the well through a hole in the concrete ring at a height of 1500 mm from the bottom of the well, that is, 500 mm above the level of the backfill, on which a water-breaking board is laid at the point where the jet falls (to prevent soil erosion). The board must be fixed, for example, with two pins going into the backfill.

The branch pipe should not be cut flush with the wall, it is better to leave the outlet inside the well 50-80 mm - otherwise the water will flow down the wall and erode the backfill.

The working volume of the well is covered from above with a flat reinforced concrete ring with holes for the cover (500 mm in diameter) and for an exhaust riser with a diameter of 100 mm.

A reinforced concrete ring is installed on the ceiling - a manhole with a diameter of 700 mm, and its top is closed with a hatch or wooden lid. A standard reinforced concrete ring is placed under the cast-iron hatch.

The exhaust riser with a wind vane must rise above ground level by at least 700 mm.

At severe frosts(from minus 25°C) the bottom cover is insulated.

Now you should deal with the diameter of the working chamber of the filter well. The volume of the filter, and hence its performance, depends on this diameter.

Wastewater leaves both through the bottom and through the perforated side wall well. Sand passes water better than sandy loam. "Gray" household water seeps through more easily than water from a water closet. The dimensions of the well at various wastewater flow rates, taking into account the factors we have listed, are given below (table 7).

When constructing a well square section you can take the side of the square, equal to the diameter indicated in the table.

Wastewater treatment in filter wells takes place in a biofilm - thin layer formed by microorganisms on the surface of the filter granules. For these microorganisms organic matter in sewage are a nutrient medium.

The final treatment of wastewater occurs in the soil layer through which it infiltrates before reaching the groundwater.

Underground filtration fields are used, like filter wells, in sandy and sandy loamy soils. The device of a filtering well is possible, as was said, in the case when they lie at a depth of at least 3 m. If this depth is 2 or, in extreme cases, 1.5 m, it is necessary to build a filter of a different design - in the form of an extensive network of filtering trenches. This system is cheaper and easier to build, besides, it provides irrigation of the site. The only difficulty is that the underground filtration fields must be laid in advance, before the site is built.

The device of the underground filtering network is shown in fig. 64.

Rice. 64.: 1 - septic tank; 2 - dosing chamber; 3 - distribution pipeline; 4 - distribution wells; 5 - irrigation pipes; 6- ventilation risers with a wind vane

The dosing chamber, arranged at the outlet of the septic tank, provides the underground filtration fields with a uniform influx of wastewater. It is a container with a diameter of 1000 mm (or an area of ​​1000 x 1000 mm) with a siphon located inside, which periodically self-charges and self-discharges with clarified wastewater coming from the septic tank. Siphon diameter - 100 mm, elbow height - 200 mm.

The distribution pipeline is a pipe with a diameter of 100-125 mm (plastic, asbestos-cement or ceramic). It is laid in a trench at the outlet depth of the dosing chamber with a slope of 0.02 (2 cm per meter of length), which ensures the gravity flow of wastewater. In any case, the distance from the pipe to the ground must be at least 500 mm (Fig. 65).

Rice. 65.: 1 - pipe O 100 - 125 mm; 2 - lining (brick must be laid every 0.5 m); 3 - trench

A distribution well is arranged at the branching points - where filtration trenches with irrigation pipes laid in them depart from the distribution pipeline.

A well with a diameter of 500-700 mm is laid out of red iron brick or a reinforced concrete ring is used. At the base of the well arrange cement screed on compacted gravel, trays are placed above the screed at a level corresponding to the trays of the distribution and irrigation pipes (see Fig. 66).

Rice. 66.: 1 - concrete base; 2 - distribution pipeline; 3 - concrete ring; 4 - wooden cover; 5 - input of an irrigation pipe

This level is different for each well, since the distribution pipeline is laid with a slope.

From above, the well is covered with a wooden lid (shield) and covered with gravel, crushed stone or slag (granule size 15-25 mm).

By installing plugs in the well, it is possible to cut off certain branches from the network and thereby regulate the irrigation of the areas of the personal plot.

Filtration trenches with irrigation pipes are laid in parallel rows at a distance of at least 1.5 m in sandy soils and 2.5 m in sandy loam. The total length of trenches required for wastewater disposal is given below.

Each trench branching from the distribution pipeline must be no longer than 20 m. The depth of the trench is selected depending on the calculated value of the minimum winter temperature.

At the bottom of the trench, a groove 300 mm wide and 200 mm deep is torn off, into which a filter layer of gravel, crushed stone or slag (granule size 15-25 mm) is laid, on which an irrigation pipe is laid. The irrigation pipe should have a slope of 0.02 away from the well for gravity flow of sewage and holes through which water irrigates the filter layer.

Rice. 67. Irrigation pipe made of asbestos cement (a), plastic (b) and in the form of a brick tray (c, d): 1 - pipe; 2 - cuts or holes (when laying in a trench, they face down); 3 - brick side of the tray; 4 - brick bottom of the tray; 5 - gap 15-20 mm; 6 - filter layer.

You can use asbestos-cement, plastic or ceramic drainage pipe with a diameter of 75-100 mm. If used asbestos cement pipe, in it, the holes for the spout are arranged in the form of cuts a third of the diameter 10 mm wide in increments of 150 mm and laid with the cuts down.

AT plastic pipe drill two rows of holes with a diameter of 10 mm in a checkerboard pattern at a distance of 50 mm from each other (Fig. 67 b). Pottery drainage pipes they are not laid end-to-end, but leaving a gap of 15 mm, which is covered from above with roofing felt overlays. Instead of irrigation pipes, it is possible to lay a brick tray with a section of 120 x 120 mm along the filtering layer, leaving gaps of 15-20 mm at the bottom of the tray (see Fig. 67 c).

As shown in fig. 64, at the ends of the filter trenches, or rather, irrigation pipes, exhaust risers should be provided. They are made from a pipe with a diameter of 100 mm, a height of 0.5-0.7 m, and are covered with a wind vane from above.

Underground filtration fields can be built without collector wells. In this case, the sections of the distribution pipe with a diameter of 150 mm are connected by means of tees facing downwards, to which the irrigation pipes are connected through a square in a checkerboard pattern. For elbows and tees, cast iron sewer fittings are suitable (see Fig. 68).

Rice. 68.: 1 - septic tank; 2 - dosing chamber; 3 - collector pipe (with one distribution well); 4 - tee; 5 - irrigation pipe; 6 - hood; 7 - square.

The treatment of "gray" wastewater is much less of a hassle than the treatment of wastewater generated when using a water closet. No wonder received in last years distribution of dry closets, that is, toilet bowl structures that do not need flushing water, are often used (in Scandinavian countries) even in multi-storey city buildings. There is something to think about!

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Filtration well - a device used for wastewater treatment and subsequent drainage. It is used for sewerage in a private house. The task is the final cleaning sewage water.

Filtration wells are also used for storm sewers.

The principle of operation is as follows:

• waste water sewer pipe by gravity fall into a chamber with a septic tank;
• water is settled in the chamber;
• then water, also by gravity (for soils with low level groundwater), penetrates into the filtration well;
• through perforations in the walls and bottom, it already enters the ground.

Such systems are made of reinforced concrete rings, brick or plastic. The total surface area of ​​the well (walls and bottom) depends on the type of soil in which it is settled. Sandy soil absorbs the same amount of water twice as fast as sandy soil.

The depth of the shaft is usually 2.5 - 3 meters, however, if the receiver cannot cope with the amount of water entering it, it is not necessary to increase the area by deepening the shaft. If you can't make one well larger area- Set up a few.

A filtration well in a high level of groundwater (above 1.5 meters from the surface) with soils with good water permeability is not satisfied, but at an average level (below 1.5 meters from the surface) underground filtration fields are arranged with a communication length of 20 to 30 m - for sands, and from 30 to 50 m - for sandy loam. The data are given for filtering half a cubic meter of water.

A filtration well is not installed in clay (they are only suitable for soils with high water permeability). For filtration, a filtering semi-buried mound is used, made of a mixture of sand and gravel.

The area of ​​​​such an embankment should be 5 m 2 (this is enough to filter water with a volume of about half a cubic meter per day. If groundwater is close to the surface of the earth, the area of ​​\u200b\u200bsuch an embankment should be increased to 8 m 2 and made completely ground.

Tapered options

Conical wells

A conical filtration well is used for the disposal of wastewater that has been treated in treatment plants, biological treatment plants, septic tanks.

Such a well is made of a drainage corrugated pipe with a diameter of 63 mm in two versions: with and without perforation.

Due to their shape, they can be mounted in any soil, including even heaving clays. The upper diameter is 0.6 m, the lower one is 1 m, and their heights are different: a meter, one and a half, two and two and a half meters.

Such a drainage filtration well is used after the Unilos treatment plant. From above it is covered with a hatch. Polymer sand hatches are popular due to their low cost with a long service life.

Cylindrical options

Well made of plastic cylindrical shape

A plastic filtration well can also be made in a cylindrical shape. It is made from the same polypropylene pipe.

The only difference from conical ones is that they are not suitable for all types of soils (it is suitable for loamy soils, but it is still better to use conical soils for clay soils).

The cylinder diameter is 1 meter, and the standard sizes are one more in height than in the case of conical wells - cylindrical ones are also available with a height of 3 m.

Not only is it much easier to buy a ready-made filtration well and install it than to carry out underground filtration fields - a conical perforated filtration well has other advantages:

• and ceases to function “in full force”, that is, the above data on the utilization of half a cubic meter of water are valid only for an unsilted field. Cleaning such fields is impossible - the design has to be completely changed from time to time.
• The filtration conical (or cylindrical) well does not require a preliminary rigid layout of the site.
• The purchase and installation of such a device will cost less than the organization of an underground filtration field.

Septic tanks

Diagram of a simple septic tank

Septic tanks today are not just cesspools, and a local treatment plant.

It cleans up to 250 liters per hour. The septic tank removes nitrates, nitrites, phosphorus, ammonium from the water entering it. Ammonium is removed in the receiving chamber, in the process of aeration.

After that, biochemical treatment is carried out, as a result of which the water is purified from some organic contaminants and enters the secondary sump. Filtration well for a septic tank at low groundwater is the place where water is discharged from the sump. With high groundwater, the discharge is made into a special ditch, and with the help of a pump.

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A filtering (filtration) well is a structure for soil treatment of sewage after a septic tank, they are used in conjunction with septic tanks. In the filter well, the biological treatment of wastewater takes place before it enters the soil. Biological treatment occurs with the help of a biofilm, which is created by microorganisms on an artificial filter load, the substances contained in wastewater serve as food for them.

Filter well device

Filter wells are made of reinforced concrete rings or bricks, the dimensions of the wells should be no more than: 2 x 2 meters in length and width, and no more than 2.5 meters in depth. There are several nuances, a filter well can only be installed if the inflow of sewage is not more than 1 cubic meter per day, and they can only be placed on sandy and sandy soils, they will not work on clay and loam.

If the well is made of concrete rings, then the lower ring must be perforated (with holes), for the entire volume of the lower ring, as well as at a distance of 30 cm from the outer walls of the ring, the filter load is poured - crushed stone, gravel, sand - this is called a bottom filter. The supply sewage pipes are located at a height of 10 cm from the bottom filter.

Calculation of the area of ​​the filter well

When calculating the area of ​​the filtration well, not only its bottom should be taken into account, but also the area of ​​the walls of the ring with holes, the load on the well should be as follows:

• In sandy soils - 100 liters per day per 1 square meter
• In sandy loam - 50 liters per day per 1 square meter

So, for example, the area of ​​a filtering well made of rings with a diameter of 1.5 m (cs 15.9) will be:

• Bottom area - 1.75 m2
• Wall area - 4.24 m2
• Total: 6 m2

Other features of the installation of the filter well

The ground level should be 1 meter below the base of the filter well. Top part well (mine), covered reinforced concrete slab overlap, it should have an inspection hole and a hatch in order to be able to check the condition of the well, and have access to it if necessary. For air inflow into the well, it is necessary to make a ventilation pipe with a diameter of 100 mm.

The sanitary protection zone from the filtration well is 8 meters. Well distance from drinking well or the well should be as large as possible, at least 15 meters, and it should be located down the slope from the well.

Cleaning up content sewer runoff – milestone drainage in the country or in a private house. Biological materials with high filtration properties are able to purify the liquid that has entered the storage tank from suspensions by 70-80%, which makes it possible to use the resulting recycled water for household needs. For example, for watering or irrigating beds.

The device of the filtration well is quite simple in execution, but thanks to natural filters- sand, crushed stone, gravel, peat and other materials, quite effective in terms of final filtration results. Water becomes cleaner - loses harmful impurities if they have been present up to that point.

At its core, filtration wells are the simplest treatment facilities, supplementing septic tanks (storage tanks for sewage water). Accordingly, they are built near the storage wells and are connected to the latter by a short pipeline placed at a slope and providing a natural outflow of liquid into the filtration chamber.