Wastewater treatment in a private house: septic tank or VOC? Sewage treatment facilities OS, KOS, BOS Purification of wastewater sewerage.

Human activity, like any other living being, is without fail accompanied by the release of a considerable amount of waste products. In modern conditions, almost all of them are carried away by the waters of sewer rivers. Finally, our civilization is almost impossible to imagine without a huge number of factories and other enterprises that also produce wastewater in abundance.

About the process of waste disposal

Wastewater treatment is a process, after which the effluent is suitable for use for technical purposes or return to the environment without harm to the latter. In a word, the method depends on the further use of the liquid. For example, wastewater from sinks is not the same as the contents of the drain holes where the contents of the toilet go down.

Why is it so important?

In April 1993, more than 400,000 people in Milwaukee ended up in a hospital bed after getting Cryptosporidium in their drinking water. After this case, which received a powerful response in the WHO, the world community has become much more cautious about the liquid that flows from the taps under the guise of "drinking water". This view has only been strengthened by the publication of some cases of epidemics in India, in which hundreds of people died. But it was an ordinary Escherichia coli that got into the water supply from poorly treated drains! So wastewater treatment is an extremely important process that saves people's lives and health.

Any contaminants radically change the taste, color and smell of the liquid, not to mention its suitability for use in food or technical purposes. The most dangerous are industrial effluents, since they often contain such concentrations of heavy metals and other substances that are tens and hundreds of times higher than the most “optimistic” MPCs. Of course, in this case, everything depends on the specific production that discharges wastewater. The sewers of an average city may seem like a “spring” by comparison, since they at least do not contain radioactive isotopes or huge amounts of heavy metals.

Effluent classification

Dangerous pollution that makes water unsuitable for drinking and domestic use can be classified as physical, chemical, biological factors. The emission of radioactive isotopes stands apart. Accordingly, the classification of pollution will be identical to the reasons that cause them:

• mechanical factors. They are characterized by a sharp increase in the smallest mechanical suspension in a liquid.
• Chemical. The content of any chemical compounds is increased in water. It does not matter whether these substances can have a negative impact on the health of the human body.
• Biological and bacteriological (domestic wastewater). A very dangerous type of pollution, since in this case the content of microorganisms in the water is exceeded. At the very beginning of the article, we already said what this is fraught with.
• Thermal pollution. This is the name of the discharge into rivers and other bodies of water from cooling ponds at thermal power plants and nuclear power plants. This variety should not be taken lightly, since such phenomena lead to the mass death of endemics adapted to low water temperatures, which are characteristic of our area.
• Radioactive. Radioactive isotopes are found in water and bottom sediments. This happens when the wastewater system at some industrial enterprises or nuclear power plants is faulty.

Characteristics of the main types of waste

In our conditions, drains of three types are most common:

• Impurities of inorganic origin, including even non-toxic compounds.
• Substances of organic origin.
• Mixed drains.

Wastes from metallurgical industries are very dangerous, as they contain a huge amount of heavy metals and other toxic compounds. They change the physical properties of water. In those reservoirs where this poison enters, all living things die, including trees and other vegetation along the banks. Organics are dumped by oil refineries and similar industries. In the effluents there is not only relatively safe oil, but also extremely toxic phenols and similar substances. In addition, livestock-type enterprises should not be discounted.

They throw out a huge amount of organic matter. The latter causes a sharp deterioration in the organoleptic properties of water. In reservoirs where wastewater from enterprises enters, there is a sharp development of microscopic algae, flowering, and the oxygen content in the liquid drops to a minimum. Fish and other hydrobionts die. The production of electronics, including etching of printed circuit boards and the production of various types of radio engineering products, produces mixed-type effluents. They contain dyes, heavy metals, acetone, phenols and other compounds.

Danger of oil spills into the water

Currently, scientists around the world are sounding the alarm, as a huge amount of oil enters the oceans. It forms the thinnest film on the surface of the water, which can sometimes be seen only by iridescent stains. This not only leads to a significant deterioration in the organoleptic properties of the liquid, but also to a sharp decrease in the supply of oxygen, which enters the ocean by diffusion. Again, hydrobionts suffer, and the lack of this substance especially affects corals, the number of which in the seas and oceans is catastrophically falling every year. Only 10 mg of oil and oil products make water absolutely unsuitable for drinking and life of living beings.

Extremely dangerous phenols, which we have repeatedly mentioned above. They are present in the effluents of almost all industrial enterprises. This is especially true for those who are engaged in the production of coke. In the presence of these substances, the mass death of the inhabitants of ponds, rivers, seas and oceans occurs, and the water itself acquires an extremely unpleasant, putrid odor.

What substances do they contain?

Wastewater treatment plants receive effluents of the following composition:

• Proteins - 28%.
• Carbohydrates - 17.5%.
• Fatty acids - 10%.
• Oils, fats - 27%.
• Detergents - 7%.

As you can see, the main share of pollutants is organic. In industrial conditions, it is pointless to discuss any composition of wastewater, since in each case it is different. In particular, in some cases allegedly purified “water” is dumped directly into the river (!) which, in appearance and composition, resembles used motor oil.

Main sources of pollution

As a rule, industrial and social facilities, as well as livestock and poultry farms are to blame for environmental pollution. Very dangerous are solid wastes that are generated during the open mining of mineral deposits, as well as effluents generated during the wood processing process. Water and rail transport generate a lot of waste of biological origin. When they enter water sources, they cause their seeding with Escherichia coli or worm eggs. It is especially dangerous when there is some kind of medical facility upstream of the river.

General information about the cleaning process

Processing includes the following methods:

• Mechanical. This includes filtration, which is used by all wastewater treatment plants, as well as settling.
• Physical. These are electrolysis, aeration, treatment of wastewater with ultraviolet radiation.
• Chemical methods. Special compositions are used for the precipitation and disinfection of substances that may be contained in effluents.
• Biological wastewater treatment. In this case, plants that absorb organic matter are used, as well as some types of protozoa, snails and fish.

General processing

Before processing begins, preparatory work is carried out. More precisely, the analysis of wastewater. Specialists in chemical laboratories determine which contaminants they contain. This helps to choose the best strategy to neutralize them. The general wastewater treatment procedure includes screening out: solid particles, bacteria, algae, plants, inorganic impurities and organic matter. Removing solids is the easiest step. It includes filtration and settling by settling. It is much more difficult to clean wastewater from fine suspensions that are not retained by conventional filter materials.

One of the simplest and cheapest methods, which, nevertheless, provides a high degree of purification, is the use of activated carbon. Filters with this material are used in almost all enterprises, the management of which is serious about protecting the environment.

How does activated charcoal work?

The main advantage of coal is its high absorption capacity. Simply put, there are so many pores on the surface of the particles of this substance that they can retain such an amount of water-polluting compounds that is several times the volume of the coal itself. It is the process of capturing, binding polluting reagents that is called absorption. It should be noted that coal was used to purify drinking water even before our era. Active research and production of this material began during the two world wars. Factors affecting absorption are particle size, surface area, structure of the binder, acidity of the medium (pH factor), and the temperature that the wastewater has.

What kind of substances can bind activated charcoal?

Charcoal absorbs many substances, ranging from non-ferrous metals to complex organic compounds (for example, phenols). Of course, it will not protect against radioactive compounds, but it can be used to remove the main types of inorganic and organic impurities.

Coagulation of contaminants

In some cases, special liquids can be used for cleaning, which include particles of colloidal substances. What are they needed for? It's simple - microscopic particles, combining with pollutant molecules, cause them to precipitate. The phenomenon is known as coagulation. Some wastewater treatment plants also use the electrolysis method. The method is similar to the previous one, since the ions produced during this process also contribute to the precipitation of contaminants.

In contrast, modern researchers are increasingly proposing methods that use bulky molecules that can more effectively bind and precipitate contaminants. This process is called flocculation.

Used chemical compounds

More about the settling method

Whatever it was, but the associated organic matter falls out in the form of flakes or gel. These sewage sludge can be easily collected with a simple mechanical filter. This method works best with relatively dense particles (eg silt and other heavy organic impurities), while lighter particles (eg microscopic algae) are best removed by settling. The settling tank must be large enough to fill it as slowly as possible. This is due to the fact that for the normal course of the process it takes at least four hours. After organic and inorganic impurities settle to the bottom, the water can be considered conditionally purified, suitable for use for technical purposes. This method is more often used in the pre-treatment of wastewater.

Then comes the turn of aeration. Water enters giant vats, where compressed air enters under high pressure, which is discharged into the liquid by means of sprayers. Have you ever seen how a compressor works in an ordinary aquarium? In this case, almost the same thing happens. Aeration allows you to saturate the water with oxygen and precipitate the remaining organic impurities. After such treatment, the liquid is most often fed into special ponds planted with higher aquatic vegetation (biological wastewater treatment). And only then the water is considered suitable for industrial use. It can be used to water the planting of vegetables and fruits, as well as dump it into natural reservoirs.

According to environmental standards, a local sewer system must be installed in each suburban area, which cleans and recycles domestic wastewater. Domestic wastewater treatment can be carried out by small devices or a whole range of different devices. How to build a sewage treatment plant yourself, read on.

Existing methods of wastewater treatment

Currently, domestic wastewater treatment is carried out in the following ways:

• mechanical. This method consists in cleaning wastewater from large particles: sand, grease, and so on. For mechanical cleaning, structures such as a conventional grate or sieve, a sand trap, a sump are used;

• biological. This method is based on the work of microorganisms (from which it got its name), which feed on various types of pollution. As a result of biological treatment, impurities contained in wastewater decompose into water and gas, which is discharged through a special pipe.

Biological treatment can be carried out using:

• biofilter, which is installed in a septic tank, prefabricated or filtering well. Cleaning is done by anaerobic bacteria;

• air filter. In this cleaning element, cleaning is carried out with the help of aerobic bacteria, which require air access to work.

In industrial wastewater treatment plants, cleaning methods such as physical-chemical or chemical can be used, which are based on the interaction of contaminants with special substances.

How to make a sewage treatment plant yourself

Domestic wastewater treatment plants can be purchased at specialized stores or made independently. Each system must have:

• coarse mechanical filter, which is installed before the septic tank or sump;
• biological wastewater treatment plant;
• treated water receiver.

mechanical cleaning

Mechanical treatment plants allow you to remove large particles from wastewater: sand, grease, oil films, and so on. To properly build a mechanical cleaning system, you must:

1. install a rake grate at the exit from the sewer system of the house. This will remove the largest particles from the incoming water;

1. further, the water purified from large impurities must enter the sand trap for mechanical cleaning from smaller impurities.

If there is a large amount of fat deposits in the household drains, then the system is supplemented with a grease trap.

Biological treatment

After a rough cleaning of wastewater, you can proceed to biological cleaning. To do this, the following types of devices are installed in the local treatment plant system:

• septic tank with biofilter. Inside the septic tank, depending on the size and cost of the device, there are several cameras. The first and second chambers are used as settling tanks, in which particles that are not caught during mechanical cleaning settle. The third chamber is equipped with a biofilter. The biofilter itself may consist of slag, gravel, crushed stone and other similar materials. When water passes through a biofilter, wastewater is cleaned by approximately 90%;

• aeration tank or metatank. In completely sealed devices, the final treatment of wastewater is carried out. The aerotank can also consist of several compartments, for example, primary treatment and secondary treatment. Between the treatment compartments, there is a sump without fail.

If a single-chamber aerotank is installed in the system, then an additional sump must be installed for final cleaning.

How to properly install the treatment facilities provided for by the scheme, see the video.

Receiver

Where to organize the discharge of domestic wastewater after treatment? Purified water can be:

• reuse, but exclusively for household needs: washing paths, cars, windows, floors, and so on, as well as for watering plants. For this purpose, water from the treatment facilities must fall into a special receiver (prefabricated well, barrel, and so on);
• dump into sewers and natural reservoirs located near the summer cottage;
• let into the ground.

If it is not intended to reuse water, and there are no reservoirs nearby, then you can build:

• filter well;

The filter well is a small container without a bottom. For its arrangement you need:

• concrete rings, plastic frame or brick. From these materials, the well itself is constructed as a receiving container;
• gravel, crushed stone, sand. Materials are required so that the waters undergo additional purification, do not harm the plants on the site;
• pipes for connecting the device with;
• a cover to give the well an aesthetic appearance, as well as placed for safety purposes.

According to the rules of environmental safety, the filter well is installed at a distance of: 10 m from a residential building, 25 m from a drinking well and 5 m - 7 m from cultural plantations.

For faster filtration of treated effluents, a filtration field can be built. A significant disadvantage of such a structure is its large size, which allows it to be used in areas with a sufficient amount of free space.

To build a filtration field, you will need:

• sand or gravel, which are used as an additional element of the cleaning system;
• pipes with holes laid over the entire area of ​​\u200b\u200bthe site and constituting the drainage network;
• covering material, such as geotextiles.

Thus, the local cleaning system is developed by the user independently or with the help of specialists. Each system must have mechanical and biological cleaning agents selected by the user. When choosing devices for cleaning, it is necessary to be guided not only by the type of equipment and the functions performed, but also by the size based on the daily consumption of water by all those living in the house.

Most users of a modern system do not think about where the water flows from the sink or toilet. Some concern arises if a blockage has formed and the water does not want to drain. But usually this problem is quite easily solved - with the help of a plunger or household chemicals such as "Mole". But what happens to the drains after they have left the field of view?

Residents of cities and large settlements who have a connection to the main sewage system do not need to worry about this. Indigenous villagers often do not ask such a question at all, habitually pouring a bucket of water from under the washbasin under the nearest bush, using the village yard all their lives, washing clothes in the nearest pond and washing on Saturdays in their own, standing on the edge of the garden.

The question of sewerage in a country house appears when city dwellers, accustomed to its presence, end up in places where this blessing of civilization is not only not heard of, it’s just that it - this blessing - is not there. And it won't.

It is difficult for a city dweller who is accustomed to "city amenities" to refuse them - "both in the rain and in the snow" to go to the toilet on the street. So my husband and I, as former townspeople, had to face the need to build a local sewage system or solve the problem of domestic sewage in an alternative way. Well, in order to do something, you need to understand how it works.

Journey down the funnel

After the dirty water has flowed into the drain, it enters the sewer system. First, to the brownie: there, in the collectors, the drains of different apartments are connected. Then the flow of sewage is enlarged, passes through a whole bunch of sewers, combining flows from different houses, microdistricts.

Along the way, rivers of household wastewater flowing in main sewer pipes under sidewalks and roads are replenished with industrial wastewater, as well as rain and melt water flowing into storm sewers. In the end, everything ends up in the sewer pools, divided by districts. And then - to treatment facilities, depending on the size of the settlement - district or city. For example, the wastewater treatment system of St. Petersburg Vodokanal treats more than 2.1 billion m³ of wastewater daily at 3 treatment plants.

This is how the sewerage system of any settlement is arranged. The main element in it is the sewage treatment plant. because diverting waste is half the battle, it is important to purify polluted waters to the degree of safe return to natural water basins.

Anyone who drinks water has a vested interest that it be clean and safe - free of dangerous chemicals and pathogens. The owner of the cottage must be aware that the quality of the water that his child pours into a glass from the tap in the kitchen depends on how he cleans what has flowed into the toilet.

How is wastewater treated

The city sewer network differs from the local sewerage of a private house only in its size. Local sewerage of a country house too should be equipped with treatment facilities. Let's take a look at how wastewater is treated.

In most cases, the process is based on the classical scheme, consisting of two stages:

• mechanical cleaning;
• biological treatment.

In some cases (for example, if the effluent that has been treated must be discharged directly into), a physico-chemical method is also used, as well as water disinfection.

mechanical cleaning

The first stage of cleaning is mechanical. At this stage, with the help of conventional mechanical filters - gratings with different cells - garbage insoluble in water is caught: pebbles, broken glass, plastic parts from hairpins or toys, earrings - in general, everything that, through negligence, got into the drain of the sink or toilet.

Grease traps also belong to mechanical cleaning systems - fat traps, which, although organic, is very poorly processed by bacteria or not processed at all. If there are not too many effluents, then the mechanical treatment step is usually neglected.

Biological treatment

The biological method of wastewater treatment was developed in 1913 in England. It is based on the vital activity of a whole army of microorganisms - various amoebas, ciliates, rotifers, zoogles and others. All this company makes up the so-called activated sludge in the treatment plant.

What sewage is made of serves as food for these microorganisms. With the help of enzymes in their cells, they decompose organic substances, of which, in the main, household wastewater consists.

Biological processes of oxidation of organic matter in wastewater treatment plants can take place with the participation of aerobic forms of bacteria those who need oxygen to breathe, and anaerobic- do not need oxygen for their life. Aerobic bacteria decompose the organic matter of wastewater into carbon dioxide (CO2) and water, and ammonium nitrogen and sulfates into the simplest substances, nitrogen and phosphorus. If there is no access to oxygen, then a community of anaerobic microorganisms develops, and biochemical processes proceed with the release of methane (CH4). All this biochemistry leads to the release of energy, which is used by bacteria for their existence and reproduction.

Similar processes involving the same microorganism company in nature go on continuously- aerobic microorganisms live in the upper layers of the soil and in water bodies, anaerobic bacteria live in the lower soil layers. The vital activity of plants is inextricably linked with the life of microorganisms found in the soil and natural reservoirs; thanks to them, humus is formed and. Therefore, the purification method is called biological.

What is a septic tank and how does it differ from a metatank or aeration tank

In nature, the decomposition of organic matter proceeds independently. But when there are too many organic compounds (as in sewage), natural mechanisms cannot cope. In artificial wastewater treatment plants, the processes are more active due to specially created conditions. Both aerobic and anaerobic bacteria are used in the wastewater treatment process. But since, by definition, they cannot exist together - they have a different "worldview", - for different types of microorganisms, cleaning devices of different designs are used:

• anaerobic facilities;
• aeration treatment facilities.

Anaerobic treatment devices

Devices in which biochemical reactions occur with the participation of anaerobic bacteria include septic tank. This is an element of treatment facilities, which is a sealed container made of plastics, concrete or metal. In the septic tank, the primary treatment of wastewater takes place, their settling: what has a density greater than that of water precipitates at the bottom, lighter contaminants float on top, forming a crust.

Depending on the design, its internal volume can be divided by partitions into 3 sections. After the effluents pass their way through the vent pipe, they enter the first chamber, where the settling process begins. The chamber is gradually filled with sewage, activated sludge and insoluble debris accumulate at the bottom, a crust forms on top, and the liquid flows into the next section, where the processes continue. Thus, in the first part of the septic tank, the largest particles of pollution fall out, closer to the exit, the activated sludge layer decreases, and the drains become more and more clarified.

At the outlet of the septic tank, wastewater pollution is about 65% of original. Effluent with such a degree of pollution is sent to the soil aftertreatment - in the fields of filtration, irrigation, biological ponds, filter wells or cassettes - depending on the specific design of the treatment plant.

Thus, metatank - this is a septic tank: the processes in it go with the release of methane, which is discharged into the atmosphere through ventilation. In an artificial treatment plant of this type, natural conditions are simulated that occur at a depth underground or in swamps.

Aeration treatment facilities

If the activity of aerobic forms of microorganisms is used for wastewater treatment, then a constant supply of oxygen is required for their life.

Aeration treatment facilities. Photo from novostroi.spb.ru

Aerotanks- more sophisticated devices require a permanent connection to electricity for compressor operation. This means that they are more expensive and capricious in operation. Aeration treatment plants are used if the volume of wastewater is large or a higher degree of water purification is required, for example, to discharge clarified wastewater into a reservoir - sanitary requirements are more stringent in this case. In aerotanks for bacteria, conditions similar to natural reservoirs are created.

Filtration fields and other methods of wastewater treatment

After the polluted waste water has passed the septic tank, it enters the post-treatment. These processes may already take place in the conditions of soil or a reservoir, but this does not mean that clarified water from a septic tank can simply be drained into a gutter: such actions are prohibited by sanitary standards. If a violation is discovered (for example, neighbors complain or a planned inspection comes), the guilty person will be fined.

Clarified water from the septic tank is sent to specially organized areas- filtration fields, filtration wells, aeration fields, irrigation fields, biological ponds. All these types of soil treatment methods work according to a general principle, and the choice of one or another option depends on the amount of effluent and soil conditions.

The principle of treatment of wastewater that has undergone preliminary treatment is based on using the same microorganisms, only now they are in the soil. What is the difference between soil cleaning methods?

Filter fields

Filtration fields are plots of land onto which effluents from sewage treatment tanks are poured. The main requirement is a good moisture-absorbing capacity of the soil. The most suitable - sandy or sandy loam. The area of ​​the filtration field depends on the volume of runoff and soil properties. If possible, the filter fields do open- that is, effluents are poured directly onto the surface of the earth.

It is difficult to make open filtration fields in private properties, because there are not enough areas to comply with the sanitary zone - the filtration field, frankly, smells. That's why they do private filtering fields: they open the ground, arrange specially filled areas of gravel and sand. Drainage pipes are laid on a gravel-sand cushion. The supply pipes - coming from the septic tank - are located in the upper horizon of the field.

If the rate of soil absorption is insufficient, another system of drains is arranged (these are discharge drainage pipes), into which filtered water is collected. They are placed on the bottom layer. After that, the water becomes sufficiently purified and can be drained into a ditch or directly into a reservoir. The figure below shows a schematic diagram of the backfilling of the layers of the filtration field.

Important point- depth of occurrence. On the one hand, the entire structure of the drainage pipes must be placed below freezing depth if you plan to use the sewer in the winter season. And on the other hand - at least 250 mm above the highest water table.

Filter well

A filtering well is a type of filtering field. Below the freezing depth, but above the groundwater level, a well without a bottom is arranged with holes along the entire surface of the walls. Soil cleaning occurs over the entire surface of the walls of the well. A sufficient layer of gravel and sand is made around and under the bottom of the well. The number of wells depends on the filtering capacity of the soil and the amount of drains.

Another variant - filter trench. Instead of several vertically standing wells, one horizontal drainage pipe of large diameter is used.

Irrigation fields

Irrigation fields - almost the same as an open filtration field, but on a plot of land intended for draining wastewater clarified in the sewage treatment system, plants are grown. The method is good - in clarified wastewater there is a large amount of nutrients converted by bacteria in a septic tank into a form convenient for plants. Minus such a system - the inability to use in cold weather.

biological ponds

Biological ponds - reservoirs into which clarified waters are discharged from treatment facilities, water analogue of open filtration fields and irrigation fields. To prevent the ponds from blooming (a large amount of phosphorus and nitrogen in the drains provokes the active development of blue-green algae), special aquatic plants are cultivated in them that absorb excess nitrogen and phosphorus. That is why the standards for wastewater treatment for discharge into natural water bodies are much more stringent than for discharge onto the soil or into the soil. This cleaning system has the same problem as irrigation fields: the harsh climate in our country.

To prevent the ponds from blooming, special aquatic plants are cultivated in them that absorb excess nitrogen and phosphorus.

Filter cassettes

In order to prevent undertreated effluents from entering the water horizons of the soil, it is necessary to take into account the depth of treatment and the level of groundwater. If the groundwater level is high, and the soils are heavy, clayey, it is impossible to arrange a deep filtration field. The only way is to make a surface filtration field, and to avoid problems with odors and freezing in winter, build embankments above the drainage pipes. Filter cassettes can be prefabricated or assembled from drain pipes on site. The height of the embankment is determined in such a way as to exclude freezing in the winter.

Biological filters

If there is no place on the site for the device of the filtration field or you don’t want to dig half the garden for laying drains, you can install a biological filter after the septic tank - artificial filtration field, due to its device having a compact size.

Why we abandoned the local sewage system using a septic tank

, we refused a septic tank or another option for local sewerage. Why?

• financial question

To do everything right, taking into account sanitary standards, a decent amount of money is required. Even if you try to save money by using three concrete rings, eurocubes or other containers instead of a ready-made septic tank, the amount of earthwork for arranging filtration fields is enormous. Especially considering the peculiarities of the soil in our area - clay at the depth of a spade bayonet and the groundwater level half a meter from the surface.

Lyrical digression: why the option “just a septic tank and not bother with filtration fields” is not suitable? Feedback from users like: "They made a septic tank with a drain into a ditch, it has been working for 3 years, there is no smell, the neighbors do not complain, but the amenities in the house" - in my opinion, are untenable. Swamps in nature do not appear suddenly, it is a long process for which 3 years is not a period. You can, of course, argue according to the principle: enough for my life, and after me - even a flood. But the drains get into the soil of my site, and the well with drinking water is also located here.

• high groundwater level

This means that we are doomed to the construction of ground structures for soil filtration: we need to fill a hill with an area of ​​at least 30 meters and a height of almost 2 m. And the water itself will not flow up - the septic tank is in the ground, which means that we need a pumping station . And this is more money and a constant dependence on electricity.

• water supply

What do you think, what does most of the water in an ordinary apartment go to? Until I calculated it, I thought that most of the water is poured out in the shower. It turned out not: up to 45% of the total daily water consumption per person in a city apartment falls on the toilet.

Up to 45% of the total daily water consumption per person in a city apartment falls on the toilet

There is a lot of water in our area: a well can be dug almost without looking, anywhere. But the debit of such a well is small, and in summer it decreases even more. It turns out that if we want to install a flush toilet, we need to spend another N-th amount of money on the extraction of water, half of which is literally flushed down the toilet, so that later we can arrange complex and expensive structures for cleaning it.

• septic needs to be cleaned

Regularly - depending on the volume - remove the accumulated sludge in the sump. If not removed, it will eventually fill the septic tank. And if removed irregularly, the degree of wastewater treatment will decrease. Up to the point that the concentration of contaminants at the outlet will be greater than at the inlet: water flowing through a silted septic tank will wash away the settled substances and become dirtier than it was. Aeration treatment plants need to be cleaned less frequently. But they also cost more.

• filtration field life

The filter field also has an expiration date - 8-10 years old. Then the gravel-sand backfill of the drainage pipes silts up and stops cleaning the drains. The only way out is to make a new filtration field, this time excavating the second half of the site. Well, or in our case - to dig a hill, replace the filtering backfill and pour the hill back.

• adequacy of the event

And it’s not even the lack of extra money, although this fact is also important: after moving from St. Petersburg to the village, I had to change my occupation (it’s unlikely that the neighbors - grandfather Anatoly or Aunt Dusya - need the services of an interior designer), which means changing the level of income . The point is adequacy: our entire hectare and 3 acres, garden, house and outbuildings are worth well, if a fifth of the estimate for a local sewage system. Looking for additional sources of income, working hard just to be able to habitually press the flush button after using the toilet? Why, then, did we leave the city and quit a decent job - there were no problems with the sewerage, and the toilet worked properly.

Wastewater, which is formed in the process of human life, entering water bodies, becomes one of the most serious sources of pollution that negatively affects human health. To reduce the pollution of water bodies, a set of measures is applied to cleaningWastewater- removal of contaminants. Drains, depending on their origin, are divided into the following types:

1. Household or household-fecal, which include receipts from residential development and public buildings;
2. Production - formed in technological processes and removed from the territories of industrial enterprises;
3. Rain, collected during rainfall, snowmelt and washing of territories.

To reduce the pollution of water bodies, a set of measures is used to treat wastewater - to remove pollution from them

Households are contaminated with all sorts of organic impurities, including food debris, and carry a huge amount of bacteria, both neutral and pathogenic. The main task of processing such wastewater is the extraction of large and small inclusions, the oxidation of organic matter contained in them, in order to reduce the burden on the environment and disinfection.

Industrial effluents, also depending on the nature of their formation, may contain a variety of organic ingredients, such as dairy effluent, mineral inclusions and other compounds harmful to life. Liquid waste generated at metalworking enterprises contains metals, including heavy ones, which, if ingested, can have a negative impact on human health.

Rain runoffs wash away organic impurities, suspended particles (sand, clay, etc.) and oil products from the territories.

Effluent of various origins contains a variety of pollutants.

The discharge of rainwater into water bodies without treatment leads to serious pollution, adversely affects human health, can accumulate in the inhabitants (fish) and, accordingly, enter the body with food.

For cleaning, various methods are used, which depend on the nature of the formation of liquids, their composition and quantity. Let's consider the methods of treatment of household water, because. they make up the largest part of stocks.

Domestic wastewater treatment methods

Wastewater entering the treatment plant goes through several stages of processing:

• mechanical;
• biological;
• disinfection.

For the mechanical stage, the following equipment is used: gratings, sand traps, sedimentation tanks, filters. The first structure that drains fall on is gratings. They are a set of rods installed vertically or with an inclination on which large inclusions are retained. The recommended clearance between the bars is 16 mm. The retained debris is removed from the screens manually (for small stations) or with a mechanical rake. The collected garbage is collected in a special container, then taken to a landfill.

The following equipment is used for the mechanical stage: gratings, sand traps, sedimentation tanks, filters

The next stage is settling in sand traps, which are rectangular or round in terms of structures. When entering the sand trap, the speed of movement decreases, and heavy ingredients, mainly of mineral origin (sand), settle. These particles carry all pollutants. Sand settles to the bottom of the sand trap, is moved by scrapers or washed off into the lower part of the pit, then it is removed to the sand platform by pumps or water jets. After drying, the sand must be disinfected and can be used, including for planning work.

After preliminary treatment, water enters the primary settling tanks, which, depending on the direction of movement in them, are divided into horizontal, radial and vertical. The choice is determined by the performance of the structures. With low productivity, vertical ones can be used, with medium productivity - horizontal ones, for large stations radial ones are used. The principle of operation of settling tanks is the same - with a decrease in the speed of movement, impurities of various sizes are released. The speed of movement in settling facilities is determined by regulatory documents. Impurities settle to the bottom, then by scrapers, liquid jets or under the action of their own weight they move to the pits, then they are pumped for further processing. There are various methods of settling intensification, first of all, it is a reagent treatment, when chemicals are added that contribute to the coarsening of suspended particles. Larger particles settle faster. Another way is thin-layer settling, when a set of shelves is placed in the sump and the process goes faster by reducing the settling height.

Secondary clarifiers are related to mechanical cleaning designs, but are located after the biological treatment stage, which will be discussed in the next section. Secondary, as well as primary, are divided into horizontal, radial and vertical, but not suspended solids are released in them, but activated sludge, which is formed in aerotanks or biofilters.

The next stage is settling in sand traps, which are rectangular or round in terms of structures.

Filtration is used for deep purification from contaminants. This process completes the technological scheme and is used in cases of stringent requirements for the quality of runoff discharged into water bodies. Post-treatment is carried out on filters of different designs, the choice of which depends on the performance of facilities and pollution. Filtration is carried out through various media, mainly natural materials of various sizes, the most popular of which is quartz sand.

Biological treatment

Settled effluents enter aerotanks - biological oxidation plants. In aeration tanks, water is mixed with activated sludge - flaky compounds of bacteria, air is also supplied here in the form of small bubbles. Bacteria in the presence of air actively absorb organic ingredients, they are oxidized and the amount of activated sludge increases. The mixture flows into the secondary settling tank, where the sludge settles, then part of the sludge is taken away for processing, part is returned to the aeration tank. With low productivity, instead of aerotanks, biofilters are used - tower-type structures filled with a special load and ventilated from below. Bacteria settle on the load. The liquid, moving from top to bottom through the load, comes into contact with bacteria in the presence of air and is intensively cleaned.

Purified liquids contain a large number of bacteria, including pathogens, so they must be decontaminated before being discharged into a reservoir. For disinfection are used:

• sanitation with chlorine-containing reagents;
• ozonation;
• ultraviolet irradiation.

Each method has its own advantages and disadvantages. Chlorination involves the use of chlorine - a toxic substance, so working with it requires special care. The liquid after chlorination must be kept for at least half an hour to remove chlorine compounds. For this, contact tanks are used.

Purified liquids contain a large number of bacteria, including pathogens, so they must be decontaminated before being discharged into a reservoir.

Such tanks, with high productivity, occupy significant areas. Ozonation is an expensive energy-intensive procedure and is carried out in sealed structures. UV disinfection is limited in performance.

In the process of processing household wastewater, primary sludge is released in primary settling tanks, after aerotanks, activated sludge is released in secondary settling tanks.

Recycling and subsequent disposal of the resulting sludge is one of the most serious tasks of sewage. The complexity of the task is determined by their large volume and properties. As a rule, sediments are hard-to-filter suspensions of organic origin. Their volume, depending on the composition and technological scheme, is 0.5 - 10% of the flow rate supplied to the treatment facilities. Their humidity is 90 - 99%, most of the moisture is in a bound state. The bacteria and helminths contained in them require serious disinfection before further use.

Recycling and subsequent disposal of the resulting sludge is one of the most serious tasks of sewage.

The main tasks are the reduction of humidity, stabilization, disinfection.

To transfer the main part of organic matter into a mineral form, methane digestion and aerobic stabilization are used. Methane fermentation is carried out in digesters, where, under the action of high temperature, the sludge is mineralized, and gas is released - methane, which can also be used at treatment facilities for their own needs. The difficulty lies in the contamination of the gas with impurities. During fermentation, in addition to mineralization, the issue of disinfection is solved.

Aerobic stabilization is used to mineralize the active or. The process is an active aeration of sludge in structures similar to aeration tanks. The next step in the processing of sludge is their dehydration. For dehydration, natural methods are used (drying on sludge beds) and mechanical methods (on belt or chamber filter presses, centrifuges, vacuum filters). Before dehydration, to transfer moisture from a bound form to a free one, it is treated with reagents or flocculants. Dehydrated sludge with a moisture content of 70 - 80% (depending on the method of dehydration) is fed for further processing - disinfection - mainly by thermal methods.

After disinfection, the sediment is suitable for use as a valuable fertilizer.

Wastewater treatment plant

Sewerage in any private house is one of the most important elements that can provide a fairly comfortable life. If, until recently, our grandparents, who lived in villages and villages, managed with an ordinary cesspool, where all the sewage was merged, and which spread far from the most pleasant aroma throughout the district, now people are striving to install a complete wastewater treatment system. Currently, many different systems are used for wastewater treatment, from conventional storage tanks to complex biotechnical complexes for deep water treatment.

Options for solving the issue of arranging sewerage in a private house

Wastewater treatment systems for a private house can be confidently divided into several main groups:

1. storage containers.
2. Single chamber septic tanks.
3. Multichamber septic tanks.

Storage tanks

These are sealed tanks that are installed below ground level and are equipped with an accessible exit to the surface for pumping out sewage accumulated in them. For the arrangement of such tanks, quite a few options are used, the simplest of which are ready-made containers, from metal tanks or plastic eurocubes in a protective metal mesh.

Installation of a storage tank for the sewerage of a private house

In addition, a wastewater collection tank can be made of concrete rings by installing them on a concrete pad and sealing all joints and technological openings, or casting a concrete container directly in a dug pit. Despite the simplicity of design, such tanks are not popular enough due to the need for constant pumping of sewage with solid waste.

Only sewage trucks with powerful pumps and reservoirs for pumped-out mud can perform such work. Such a service in some regions is quite expensive, and given that it will have to be accessed regularly, the use of sewerage becomes unprofitable. Another significant disadvantage of storage tanks for sewage is the risk of destruction of the tank and seepage of sewage into the soil, and then into groundwater, which can be used for water intake. This is especially true for metal containers, which, although they are treated with special protective compounds, inside and out, are still subject to corrosion due to the constant negative impact of the environment and chemical elements contained in detergents and entering the tank along with wastewater. It is practically impossible to check the condition and integrity of a cistern or a metal tank buried underground, since for this it must be removed from the ground.

Such structures made of concrete, although more resistant to corrosion, are still destroyed from time to time.

The exceptions are plastic tanks, which are not afraid of corrosion. If, during installation, all protective measures were taken to protect the tank from external mechanical and physical impact, the storage tank made of plastic can last forever. The problem of plastic drives in limited sizes. Although modern technologies make it possible to melt quite voluminous plastic containers in terms of strength, they are practically not inferior to their iron counterparts.

Single chamber septic tanks

This type of treatment plant is made of two types. The cheapest option is a drainage well without a bottom. To filter wastewater, sand and gravel mixture are poured into the bottom of such a well. The volume of such a septic tank is limited by the volume of the tank, which is used as a drainage well. The most common way is to build a single-chamber septic tank from concrete rings, which are mounted on top of each other in a specially dug hole. To ensure that pollution from wastewater does not go into the upper layers of the soil, where the root system of most plants is located, the joints between the rings are carefully sealed. This type of septic tank is recommended to be installed only in areas with the lowest possible groundwater horizon, otherwise, partially filtered sewage and dirt can seep through a small thickness of soil and pollute underground water sources. In addition to concrete rings for single-chamber septic tanks, metal tanks can be used, in the bottom of which large enough holes are made to drain the sewer drain.

installation of a sewer septic tank for a private house

A more acceptable version of a single-chamber septic tank, which is able not only to provide a sufficiently high-quality sewer system, but also not to pollute the environment, is a sealed tank with access to filtration fields or an infiltrator. Septic tanks of such a plan are sold in a ready-made factory version or are made independently. The design of treatment facilities with a single-chamber system is quite simple, which makes it possible to build it yourself. A sealed tank into which sewage is connected from the house can be made from any suitable material. Often these are the same concrete rings, only installed on a concrete pad to prevent wastewater from escaping into the ground. This tank serves as a sump in which solid, insoluble dirt particles settle to the bottom, while lighter fat and chemical particles, on the contrary, float to the surface.

Partially settled water from the middle layer is discharged through the overflow pipe to the filtration fields or infiltrator, which is finally cleaned and drained into the ground. The infiltrator, as well as the filtration field, is essentially the same mechanical natural filter made of sand and gravel. To ensure better filtration, such a mixture is poured over a sufficiently large area, and wastewater is distributed evenly over it. Professional factory infiltrators can be equipped with a wastewater collection system to drain them not into the ground, but into a sewage system, if any are nearby. The main disadvantage of such septic tanks is the need for periodic pumping of solid waste and activated sludge from the sump, as well as the replacement of sand and gravel as they clog and silt. Another drawback is the rather harsh conditions that allow the installation of sewers with a drain into the soil.

Multi-chamber septic tanks

Devices with several connecting tanks are quite effective for treating wastewater in a private house. To create septic tanks of this type, 2-3 sealed containers made of metal, plastic or concrete are used, connected by overflow pipes. Often, additional mechanical filters and grease traps are installed in such pipes to improve the cleaning process.

installation of a multi-chamber septic tank with a fine cleaning system

Basically, the first two chambers of septic tanks serve to settling water, but unlike single-chamber septic tanks, settling is of better quality. A so-called biological filter is installed in one of the containers. To do this, a colony of aerobic bacteria is planted in it, which are actively involved in the decomposition of the organic remains of human life. Unlike the anaerobic bacteria used in pit latrines and single chamber septic tanks, aerobic bacteria cannot thrive without a constant supply of oxygen. For this reason, the arrangement of the ventilation system is mandatory. Depending on the size of the tank and, accordingly, on the volume of wastewater, ventilation can be made with a natural inflow or with a forced oxygen injection system. The advantage of forced ventilation in a constant supply of air for bacteria that decompose organic residues, but its energy dependence is also its disadvantage. In the event of a power outage, the flow of oxygen stops, and bacteria can die.

After passing through several sedimentation chambers and treatment with bacteria, wastewater is discharged into an infiltrator or aeration fields, which are also buried in the ground. When installing a system with aeration - filtration fields, it should be remembered that planting fruit-bearing plants is not recommended above them and within a radius of several meters around. Otherwise, there is a risk that the plants absorb dirt particles through the roots and transfer them as harmful substances to fruits that a person can eat. In an infiltrator with a plastic dome, this problem does not arise, since the discharge of purified water occurs deep underground. The only limitation in this case is the planting of large trees with a developed root system that can damage the plastic.

Sewer biotreatment stations in a private house allow you to get completely purified water that can be reused for domestic needs, for example, for irrigation. These are complex devices, reminiscent of multi-chamber septic tanks in their design, but with a much more complex device that ensures their efficiency and completely autonomous principle of operation.

installation of a biological treatment plant

In addition to settling the water and separating the fatty components, which takes place in the first tank, the further discharged and partially purified water is saturated with a large volume of oxygen. This process is called liquid aeration. As a result, clarified water enters the chamber with activated biological sludge, which is saturated with aerobic bacteria, which are actively involved in the decomposition of organic matter. The last step in purification is the treatment of water with chemicals that completely kill bacteria.

Considering that overflows, oxygen saturation and forced ventilation system are controlled automatically, the cleaning station needs a constant supply of electricity. In addition, plants of this type are one of the most expensive, albeit effective, methods of wastewater treatment. This causes their low popularity among ordinary consumers. Often, biological treatment plants are installed on several houses located nearby.

There are practically no restrictions for the installation of such structures, since deep cleaning and completely sealed tanks of the device exclude accidental contamination of the soil and groundwater.

Choosing a sewer system

The selection of treatment facilities depends on a number of specific factors that are individual in each individual case:

1. Financial opportunities of the consumer. More modern septic tanks that purify water up to 85-95% are quite expensive and not always affordable for the average consumer.
2. The volume of the septic tank is determined by the minimum daily level of wastewater discharged into the sewer. The calculation of the required volume is usually done by specialists who take into account all the individual characteristics of the sewer system, but you can also independently carry out this calculation using a simple formula.

On average, from 150 to 200 liters of liquid is discharged into the sewer per person per day. These figures are averaged and include not only the direct draining of water, but also the use of washing machines, dishwashers and other household appliances. The minimum volume of a septic tank must cover at least 3 daily volumes, that is, for one permanent resident using sewerage, a septic tank volume of 600 liters is required. For two people it will be 1200 liters for three - 1800 liters and so on.

1. The type of soil, the depth of groundwater, the location of a natural reservoir nearby and the possibility of draining into common sewers, in some cases determines the possibility of installing one or another type of septic tank.
2. Availability of calling a cesspool truck. Quite often, in remote regions, there is no service for calling vacuum trucks, or it turns out to be too unprofitable financially. In such cases, it is worth thinking about arranging a septic tank with the ability to clean the sedimentation tanks in which solid waste accumulates on its own.
3. Possibility of continuous supply of electricity. Especially important for septic tanks and biological treatment plants that use aerobic bacteria, forced ventilation systems and circulation pumps.

installation of a septic tank in the ground

In general, the rules for installing a septic tank or other type of treatment plant come from a number of individual characteristics, but there are also general recommendations in this matter.

The pit where the septic tank is installed must be insulated in order to eliminate the risk of freezing of the liquid in the tanks in winter, when the temperature drops low enough. In a number of regions, it is also recommended to insulate sewer pipes leading out of the house to sewage treatment plants. Considering that the sewer works on the basis of gravity, the installation of a septic tank must be carried out so that the sewer pipes are at an angle of at least 2-3 degrees with an inclination from the house to the septic tank.

When installing sufficiently large treatment facilities, a pit for them is dug no closer than 3-5 meters from capital buildings. Otherwise, there is a risk of subsidence of the foundation of the house. Also, sufficient removal will ensure that there is no smell in the residential area, even if the septic tank fails and begins to smell unpleasant.

And of course, you should ensure that wastewater from drainage wells or infiltrators does not pollute the environment. To do this, it is not recommended to install treatment plants closer than 30-50 meters from wells for drinking water intake.