The principle of operation of septic tanks
To understand the principle of operation of a septic tank, it is necessary to have a clear idea of the purpose of this device used for the accumulation (accumulation) of wastewater for the purpose of subsequent treatment. In this case, the basis for the operation of devices of this class is the need for recycling sewage.
The principle of operation of septic tanks laid structurally. A classic septic tank is a plastic container divided by a partition into two compartments, one of which plays the role of a septic tank, and the second serves as a drainage system.
Cleaning circuit
The scheme representing the principle of operation of the filtering drainage device is quite simple. Waste (sewage) through one of the sewer pipes is discharged into the settling part of the septic tank, where they are gradually divided into two fractions. During the separation process, heavy particles sink to the very bottom, while light suspensions (oils, a mixture of fat and water) enter the 2nd compartment. In the mass of heavy suspensions that fell to the bottom, fermentation begins after some time, followed by decomposition, initiated by the bacteria, which are always present in the waste.
Note that the average duration of this process is no more than 3 days. As a result of this decomposition, all the sewage entering the septic tank falls into three fractions:
- a thick mass of wastes settled to the bottom;
- carbon dioxide;
- plain water
Tip! Since the complete destruction of sedimentary mass with the help of bacteria is impossible - at the bottom of the compartment a certain amount of sludge accumulates, which must be periodically removed.
Water purification efficiency in this compartment is, as a rule, not more than 60%. Its tertiary treatment is carried out in the second compartment, where the entire process described earlier is repeated again, with the only difference that dirty water is evenly distributed over the filter field. Bacteria are also present here, with which the remaining impurities are completely decomposed. As a result of double filtration, you get well-purified water, which is quite suitable for watering the suburban area.
Of course, the principle of operation described above is purely schematic, transmitting only the general features of the processes occurring in them, which in reality look much more complicated. This is explained by the fact that the septic tank most often represents a whole complex of containers (or a large-capacity tank, divided into several compartments).
Tip! The more compartments in your filter device, the cleaner the water entering it.
Execution options
The performance of septic tanks in one way or another is practically independent of the number and size of their compartments; however, various designs of the device provide a high degree of purification of water. Separate models of devices from the words of their manufacturer are quite capable of providing even 98% cleaning!
But to obtain such a high filtration rate, the process of cleaning sewage and sewage must consist of a large number of cycles with a total duration of about 10 days. Water with a high degree of purification (if you do not use it for watering a plot) is allowed to be discharged into any water body without worrying about contamination of the latter.
But multisection filter installations are quite expensive, so it is not economically feasible to purchase them to service one or two country houses. Usually, septic tanks with a high degree of purification are used to service small garden cooperatives or holiday villages.
One of the varieties of the classic waste filtering device used to work on the scale of one house is a simple two (three chamber) septic tank called “Tank”.
Devices of this type consist of two (sometimes three) tanks, one of which (the first is considered to be from the sewage inlet) accumulates the waste and is simultaneously cleaned, and the second is the filtration and disposal of the treated water (by seeping it into the ground).
Tip! It is prohibited to drain filtered water from a two-chamber septic tank “Tank” into natural water bodies.
Tip! A mandatory requirement for such septic tanks is the presence of a special inspection hatch through which it is cleaned from sludge. In addition, in its design should be provided with a separate vent pipe, necessary for the removal of gases resulting from fermentation.
You can watch a video explaining how a septic tank works.