Modern man uses a large amount of water for his own needs. In the process of its application, the liquid is exposed to serious pollution, becomes a threat to the environment and people. Therefore, before its introduction into natural conditions, thorough processing is necessary. One of the stages of this process is biological treatment.
The concept of biological treatment
This is a set of work that is aimed at removing contaminants (mainly organic) from water with the help of bacteria. Sewer drains coming from houses are filled with organic matter in the form of fats, sulfates, tissues of various kinds, carbohydrates and others.
Once in the sewer system, the effluents are exposed to the process of erosion by bacteria. The final product is carbon dioxide and activated sludge, which settles to the bottom of the sewer well. It can subsequently be used as an organic additive in the soil, making it rich in substances useful to plants. The sludge accumulates at the bottom of the tanks for several years, therefore, filling the tanks with itself, it reduces the volume of the sewer well. Therefore, silt deposits of the walls of structures must be cleaned.
Biological treatment scheme
There are two options for using bacteria: an independent process and with the use of measures that are based on mechanical, physico-chemical and disinfecting operations.
The first option is to backfill dry bacteria inside the sewer wells, which come to life in the water, begin to multiply and eat organic matter. Such drugs are sold in the form of tablets, powders and granules.
The second option is a complex of biological treatment facilities, which includes various types of equipment.
- Mechanical cleaning precedes the process of biological exposure. At this stage, sewage is subjected to mechanical separation of contaminated water into liquid and impurities of different fractions. For this, nets, screens, filters, sedimentation tanks, sand traps and other devices are used. Usually they are installed in series. At this stage, water is purified to 40%.
- Physico-chemical cleaning is used to remove dissolved impurities from water. At this stage, technologies such as flotation, electrolysis, sorption, neutralization and others are used. Many of them use chemicals.
- Disinfection of sewage is the final stage. More often, ultraviolet radiation is used for this, with the help of which harmful bacteria, viruses and other microorganisms are killed. Previously, chlorine was used for this, which today is not used in modern treatment plants.
In sewer systems of private houses, ultraviolet disinfection is rarely used. Although modern septic tanks of an expensive class carry such compartments in themselves. Standard septic sewer networks are three options for biological treatment:
- aeration tanks that use activated sludge, rich in bacteria that devour organic matter;
- biofilters;
- anaerobic fermentation, which is called a digester.
The former are considered the most effective. The principle of operation of such biological wastewater treatment plants is based on the design of the equipment. Purely structurally, these are several containers combined into one device. In one, precipitation of undissolved particles occurs - water is clarified. In the second, effluents are exposed to activated sludge. Biological treatment takes place here.In the third, the effluents along with the sludge are fed by means of a pump, where sedimentation of sludge masses takes place. They subsequently by gravity fall back into the second compartment.
In some septic tanks there is a fourth compartment where water is purified with oxygen, because some kind of bacteria can only live if it is present. Such equipment is equipped with compressors.
Biofilters are popular among summer residents, because they are designed to treat a small amount of sewage. In essence, this is the container into which bacteria are loaded. Manufacturers offer two types of biofilters:
- drip;
- two-stage.
The former differ from the latter only in a reduced cleaning rate. In quality, the two technologies are the same.
The digesters are a reinforced concrete container with a floating lid, which can be raised under the pressure of the released methane gas. The latter is a waste product of bacteria. Sewer drains inside the tank are heated using water or steam radiators. Inside is a stirrer that rotates all the time, mixing the contents of the digester.
There is no oxygen inside the tank. It is these conditions that make it possible to isolate fatty acids from the organic mash that float to the surface of the water mass. Here they are converted with the help of bacteria into methane, carbon dioxide and sludge. The latter settles to the bottom of the tenka. Gases through special pipes in the equipment cover are discharged beyond it.
Biological ponds
This type of biological treatment of sewage is used if there is a need to combine a whole village or several large houses into one system. There are three types of circuits:
- A small river is brought into the pond, the water of which is mixed with sewage. Heavy undissolved particles are precipitated. Cleaning time - at least 15 days. Usually fish are raised in such ponds that increase the degree of biological treatment.
- Several ponds into which the effluents fall undiluted. The tanks are arranged in series. Water moves from one pond to another. Thus, the degree of water pollution is reduced. Carps are often bred in such reservoirs.
- Post-treatment ponds. This is the final stage of multi-stage cleaning, not related to ponds and other tanks of this type.
In private housing construction, complex technological processes are practically not used. The most difficult of them is a septic tank, working on the principle of aeration tank. These are compact, volatile devices that are mounted next to the foundation of the house. There are simple modifications without using electricity. In them, biological cleaning processes occur with the help of bacteria, which are poured directly into the septic tank. The former are many times more expensive than the latter, but their degree of purification is very high - up to 99%.
Water from such treatment facilities can be used to irrigate the garden and vegetable garden. If you install additional filter elements, clarified liquid can be used for domestic purposes.
