Sewer wastewater treatment. Wastewater treatment plants for residential, commercial and industrial facilities. Existing methods of wastewater treatment
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:
- storage containers.
- Single chamber septic tanks.
- 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. To equip 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:
- 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.
- 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.
- 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.
- 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.
- 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.
The uncontrolled release of wastewater provokes irreparable environmental consequences.
Peculiarities
In its structure, the sewage disposal network of an industrial enterprise is much more complicated than a conventional sewerage system in a private or even an apartment building. The components of an industrial sewer system are as follows.
Network of communications for the disposal of household and fecal waters.
Wastewater network from production.
Removal of clean and conditionally clean wastewater (storm sewer).
Large enterprises have their own treatment facilities, taking into account the specifics of production. For example, runoff from tanneries must be settled for a long time so that the waste does not clog the city sewer. Wastewater from chemical plants is treated to avoid environmental pollution.
Cleaning sewers in an industrial enterprise is a difficult and lengthy process. Small enterprises do not have stationary treatment plants. Wastewater is discharged into settling tanks, then using the services of companies equipped with special equipment. This technique is very convenient and maneuverable, it can work on objects with inconvenient access roads, as well as pump out sewage from a considerable depth. The use of a vacuum loader is an environmentally friendly process, since the loader pumps out all wastewater, including those with hazardous impurities.
Thus, there is no standard, typical industrial sewerage scheme. When designing a sewer network, engineers need to consider the following factors.
Waste water volume.
The nature of stocks.
Chemical composition and temperature. . Possibility of reuse in production.
Possibilities to extract valuable chemicals.
Methods and degree of purification.
Most often, industrial sewage is connected to a centralized city system. This is one of the most profitable options. When industrial wastewater is diluted with domestic wastewater, subsequent treatment becomes much easier. However, the discharge of industrial effluents into the city sewer is strictly regulated. For this reason, the correct choice and installation of treatment facilities is so important. If the wastewater contains only inorganic impurities, it is advisable to collect them in special tanks. After settling, they are suitable for reuse in the production process. Installations have been installed at individual enterprises that allow the extraction of valuable substances (wool fat, non-ferrous metals, etc.) from wastewater. As a rule, membrane treatment is used, which makes it possible to simultaneously solve two problems: to purify wastewater with high quality and to obtain valuable raw materials that can be put back into production.
Storm sewer
The tasks of "storm drains" at industrial enterprises are as follows.
- . Removal of roof water.
- . Collection of water from washing complexes.
- . Accumulation of water coming from roads.
The storm sewer of an industrial enterprise can be connected to a citywide network if the waters do not contain insoluble inorganic impurities and similar chemical compounds. If the water contains insoluble impurities, it is subject to mechanical treatment. In case of poor throughput of the city sewer network, special reservoirs are equipped on the territory of the enterprise, from which a uniform discharge of wastewater into the general network is carried out.
Operating modes
There are 2 types of modes of industrial sewer systems.
Gravity - the use of natural terrain for the transportation of wastewater. The main advantage of this method of transportation is minimal energy consumption.
Pressure - transportation of effluents to treatment devices and further, to the discharge point, is carried out using pumps.
The specifics of the work of many enterprises does not allow choosing any particular mode. Most often, there is a combination of both methods of waste disposal.
Care Issues
Sewer cleaning is a topical issue for all industries, and there can be no exceptions here. Lack of careful care can lead to unpredictable consequences. The specifics of cleaning is as follows.
Effluent from most enterprises contains toxic and suspended organic matter. This means that one cannot do without specialized equipment, which professional companies are equipped with.
The work of cleaning an industrial sewer system is an individual, non-standard process. Wastewater has a different chemical composition, and in no case should they be mixed. In each case, it is necessary to develop an individual cleaning algorithm. Fundamentals of a professional approach to sewer cleaning In order for the enterprise to function stably and not stand idle, preventive sewer cleaning should be carried out at least once a year. If everything is done correctly, the risk of blockages is minimal. On the contrary, if preventive measures are neglected, the settling of dirt and industrial waste on pipes gradually leads to a complete loss of their patency. One-time blockage removal is only a half measure. A professional approach involves eliminating exactly the cause of the blockage.
All cleaning activities are divided into 2 large groups.
Urgent (clearing an already formed blockage).
Preventive (pipe patency is only partially broken so far).
Works differ from each other in speed and degree of efficiency. Prevention can take several days, while the time for emergency elimination of blockage is much shorter.
Cleaning methods
Chemical, thermochemical. It involves the use of synthetic compounds to dissolve blockages. The method is highly effective, but the wrong choice of chemicals can damage the pipes (thinning or even breaking the integrity).
Mechanical. It is used for too strong blockages or if the blockage provoked the entry of a foreign object into the pipe. For mechanical cleaning, a cable with a nozzle is used.
Hydrodynamic. The elimination of blockage is carried out with a water jet, which is supplied under strong pressure. The pressure value is 150-300 atmospheres.
Depending on the size of the blockage, the amount of pressure and the type of nozzle are selected. It is an efficient and at the same time gentle method that gives good results even at low temperatures. The risk of damage to pipes, regardless of the material of manufacture, is practically zero. . Pneumohydropulse.
Hydrodynamics
When cleaning drainage systems, special hydrodynamic machines are used. There are 2 types of hydrodynamic machines.
Powerful units for the movement of which trucks are used.
Small devices for internal sewage.
The complete set of equipment depends on the specific model, manufacturer and price segment. However, any model includes a water tank, a system of hoses and nozzles. The correct selection of one or another nozzle makes it possible to effectively clean the pipe from contamination.
There are such types of nozzles.
. "Chain carousel". With its help, it is possible to remove foreign objects that have fallen into the sewer. . Bottom nozzles - clear pipes of silt and sand.
Penetrating - used to eliminate running pollution.
Rotary - to remove layers of fat.
Complex - a universal option. It is applied at elimination of pollution of different types.
Chemical, thermochemical methods The thermal method (dissolving blockage with hot water) is especially effective for removing fatty “plugs”. It is also used when cleaning storm drains in the cold season. Cannot be used if the pipes are made of PP and PVC. The chemical method involves the use of certified chemicals, which, for greater efficiency, are pre-foamed using special equipment. In addition to cleaning agents, chemical compounds with a disinfecting effect are simultaneously used.
Pneumohydropulse method
This is an efficient and environmentally friendly way. It is carried out with the help of special equipment. Short multiple pulses are fed into the pipeline. When a sound wave passes through a liquid medium, cavitation bubbles are formed. When the bubbles collapse, a shock wave is formed, the power of which is sufficient to tear off the particles of pollution from the pipe. The power of the device is enough to eliminate any blockages and dirt. The machines are also equipped with special sludge pumps and tanks with a capacity of about 14,000 liters, which makes it possible to clean pipes on a large scale. Comprehensive work to eliminate blockages involves the use of at least two types of cleaning. One - to directly eliminate blockage, the other in order to eliminate the root cause.
When choosing one or another method, such factors are taken into account.
Blockage dimensions. . The material from which the pipes are made.
The degree of deterioration of communications.
Sewer cleaning is a job that requires special knowledge and skills. Therefore, the maintenance of industrial drainage systems should be entrusted to professionals.
Updated: 29 June 2017Most 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 washstand 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 arises when city dwellers, accustomed to its presence, end up in places where this blessing of civilization is not only not heard of, but 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.
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, ring 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 this degree of pollution is sent to soil aftertreatment - in filtration fields, irrigation, biological ponds, filter wells or cassettes - depending on the specific design of the treatment plant.
In this way, 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 soil or water conditions, 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
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
- water supply
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
- filtration field life
- adequacy of the event
Wastewater treatment is the removal of foreign impurities from them before being discharged into a reservoir or soil. Wastewater can be divided into several categories:
- household - sewerage;
- industrial - the result of the work of factories and factories;
- atmospheric - melt and rain water.
Not only effluents discharged by enterprises should be cleaned, but also domestic ones - from sewer systems. Poorly treated water, even from a small private house, can cause serious damage to the environment.
Previously, sewage was collected in ordinary, so-called cesspools, but due to non-compliance with sanitary standards, they have to be abandoned. Today, autonomous sewage treatment plants are used to collect and treat domestic wastewater, where they are cleaned by 90 - 99%. After that, they can be dumped into open water bodies or the ground.
Cleaning methods
Domestic wastewater may contain soluble or insoluble impurities. Depending on the size of the contained particles, they can be divided into:
- emulsions and suspensions - 0.1 microns;
- colloids - from 0.1 microns to 1 nm;
- dissolved particles.
Cleaning is carried out using various methods and means. Cleaning methods are divided into several groups:
- mechanical - filtration and hydrodynamic processes;
- physical and chemical - chemical and heat treatment;
- biological - processing by bacteria.
When choosing a cleaning method and process, it is necessary to take into account the degree of contamination, the content and size of impurities. Most often, for household (household) effluents, biological and mechanical methods are used.
Video: Methods and facilities for wastewater treatment
Biological wastewater treatment
In nature, water is purified by microorganisms that live in it or the soil. Bacteria decompose organic particles into water gas. This method, although effective, is quite time consuming.
Bacteria need an ideal environment for their life. For example, for aerobic microorganisms, which need oxygen for life, it is necessary to equip aeration systems.
But their brothers - anaerobic bacteria, do not need oxygen and do an excellent job with their duties in sealed containers. But as a result of their work, gas is released, therefore, for buildings in which these microorganisms are used, it is necessary to arrange a ventilation system.
On a note! Biological wastewater treatment is used only after mechanical.
Mechanical Methods
Any wastewater treatment begins with sedimentation or filtration, due to which large impurities are removed from the liquid. For this, coarse filters are used, such as: sieves, grates, sand traps, etc. In most treatment plants, the settling method is used, in which heavier particles settle to the bottom, and light ones move on to the next stage.
On a note! During mechanical treatment, up to 65 - 70% of impurities are removed from domestic wastewater.
Chemical cleaning
This method is based on the addition of chemicals to the drains. As a result of the reaction occurring during the interaction of chemicals with impurities contained in wastewater, a precipitate is formed, which in turn is removed mechanically.
This method allows you to remove up to 25% of soluble and 95% of insoluble impurities. Potassium permanganate, chlorine and other substances capable of disinfecting are used to disinfect water.
Physico-chemical method
For the purification and disinfection of domestic sewage, the physicochemical method is rarely used. It is mainly used in wastewater treatment plants intended for the treatment of industrial wastewater.
Physical and chemical methods include:
- coagulation;
- flocculation;
- flotation;
- adsorption;
- ion exchange method;
- reverse osmosis method.
Since this technique is practically not used in, we will not analyze each item in detail in this article.
Methods used in domestic sewage
The simplest cleaning devices for household sewer systems, which include cesspools, use two main methods in their work: mechanical and biological cleaning. Effluent in these devices is settled and treated by microorganisms.
Most conventional septic tanks use anaerobic bacteria in their work, that is, those that do not need air access. At the same time, cleaning is slow, and the liquid is not completely cleared, so it is necessary to arrange after-treatment at the outlet - filtration fields.
More advanced treatment plants, in addition to settling and anaerobic biotreatment, use inlet filtration and aerobic microorganisms. As a result, the output is 97-98% purified water.
Cleaning rates
There are no strict requirements for household wastewater. The regulations, in which the permissible concentrations in treated water of a particular substance are recorded, apply only to industrial treatment facilities. However, this does not mean that the crude liquid from can be drained into water bodies or directly onto the ground. For this, they can be held administratively liable.
For domestic wastewater, the law regulates the concentration of certain substances if they are discharged into open water bodies. The same applies to water that drains into the soil, since over time it will still fall into the reservoir.
On a note! For effective operation of the sewer, follow the rules for its operation. Do not dump garbage into it, as well as pour solvents, paints and varnishes, gasoline and other chemically hazardous substances. Only domestic sewage should enter the sewer system.
Conclusion
There are many methods for wastewater treatment, the choice depends on the nature of the pollution and the requirements for the quality of treated water. Domestic wastewater is treated mainly mechanically and biologically. And the physico-chemical and chemical method is used in large enterprises.
Video: Modern wastewater treatment technologies
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Sewerage and wastewater treatment in a private country house
Country houses located in country associations, rural areas and even in a number of cottage villages do not always have the ability to connect to a centralized sewer network. The optimal solution to the problem is the use of a local treatment plant - VOC
From the cesspool to the VOC
Modern technologies in the field of engineering equipment are advancing by leaps and bounds, and today many types of domestic wastewater treatment plants have been developed. Recall how the history of private sewerage developed.
First - a cesspool, then its modernized version - a septic tank, and finally installations in which a full cycle of wastewater treatment is carried out. The latter are called differently: stations (systems) for deep biological treatment, wastewater treatment plants (STPs), local treatment facilities (VOCs), etc.
In order not to get confused in these names, which essentially mean the same thing, we will use the abbreviation VOC.
But we will talk about VOCs a little later, and now we will discuss the question: are septic tanks already in the past or not yet?
Since a consumer who is inexperienced in the problems of private sewerage sometimes misinterprets the meaning of this term, it would not be out of place to recall that an industrial septic tank is a large container (most often made of plastic) located in the ground and connected by a supply pipe to the sewer outlet from the house.
The simplest septic tank is essentially a large barrel, more complex models are divided into two or three sections or consist of two or three separate containers. In a septic tank, wastewater does not just accumulate, it is their primary decomposition into heavy ones, gradually settling down, and light ones, floating to the surface. Thanks to this treatment method, which is called mechanical, the wastewater is cleaned by 60%, which is a very low degree of purification, and therefore it is forbidden to dump it on the terrain.
Ten-year-old technologies implied the installation of filtration fields in the area adjacent to the house - drain systems, through which soil post-treatment of wastewater from the septic tank took place. Today, this is an outdated method. However, the septic tank itself cannot be discounted. Sometimes it helps to solve certain problems. For example, if we are not talking about a year-round country house, but about a summer house where the family visits seasonally or periodically. Since the septic tank is suitable for processing a relatively small volume (1 -3 m 3 / s.) of domestic wastewater and fecal matter, it will be necessary to call in a sewage truck from time to time. To reduce the rate of filling the tank, drains can be divided into "gray" (water after washing dishes, bathing, washing) and "black" (receipts from the toilet) and send only "black" to the septic tank.
In any case, for a house of periodic stay, a septic tank will be the most economical solution. Sometimes it has to be set for other reasons. For example, in water protection zones, where it is forbidden to use even VOCs that clean wastewater by 94-98%. Actually, this is all the information that a private developer needs to know about a septic tank in order to make a choice in favor of a septic tank or VOC.
Wastewater disposal options
a) Discharge of purified water by gravity into the existing drainage network
b) Discharge of wastewater to an intermediate well in which a drainage pump is installed
c) Pressure discharge of wastewater into a road ditch
d) Gravity discharge of sewage into a filtering (drainage) well
Principles of operation of aeration VOCs
There are a great many individual sewer installations on the Russian market. Some of them, called differently, are actually almost "twins". And therefore it makes no sense to describe each model separately and compare them. It is much more important for the future user to understand the fundamental constructive difference between systems from each other.
Conventionally, all installations can be divided into two types: aeration and complex. In the first, wastewater treatment occurs due to the work of aerobic bacteria, which use the oxygen contained in the air for their life activity. How does it enter the VOC tank? Aeration (saturation of water with air oxygen) is forced: for this, compressors (pneumatic aeration) or pumps (ejector aeration) connected to the installation are used.
The wastewater treatment method used in such equipment is biological, therefore this type of VOC is also called biological treatment systems (less commonly, bioseptics). Structurally, the device is a container (usually made of polypropylene) with technological hatches, divided by partitions into several sections: septic tank, anaerobic bioreactor, stage I aerotank - biofilter, sedimentation tank, stage II aerotank, secondary sedimentation tank - contact tank, pump compartment. The number of camera compartments for different models may be different.
Their common purpose is to sequentially purify domestic wastewater to the parameters specified in the technical data sheet. This is done in the following way. Wastewater is sent to a septic tank, where it is fermented, suspended solids are separated, sand and other insoluble impurities are settled. After that, partially clarified effluents enter the anaerobic bioreactor, where they are treated with anaerobic sludge (community of microorganisms). The process takes place without access to oxygen. Anaerobic bacteria convert organic compounds that are difficult to oxidize into easily oxidizable ones. Then comes the turn of cleaning in the aerotank of the 1st stage with the effect of oxygen (using forced aeration). Here, wastewater is mixed with activated sludge, which absorbs and oxidizes pollution. After that, the wastewater enters the second stage aerotank, where it is further purified (by oxidation and adsorption) with a biofilm of microorganisms formed on a load of artificial "algae" with continuous fine-bubble aeration. Further, in the secondary clarifier, the activated sludge is deposited and returned to the septic tank using an airlift, and the wastewater, purified up to 98%, is discharged to a lower relief place. This is how VOCs of the first type work - aeration ones.
Integrated wastewater treatment plants in a private house
VOCs of the second type are complex installations in which wastewater treatment occurs in three ways: mechanical, biological and chemical-physical (coagulation). Structurally, they differ significantly from aeration plants. Integrated VOCs consist of a vertical sedimentation tank with baffles (septic tank) and a bioreactor located above it. Sediment settling and anaerobic treatment take place in the septic tank. In the bioreactor - aerobic (with oxygen) treatment of already clarified wastewater. Bacteria attach to the biofeed of the reactor, forming an active biofilm. The set of installations includes a precipitating chemical (coagulant) in the form of tablets. It binds phosphorus, significantly reduces its concentration in wastewater and accelerates the process of precipitation. The coagulant is in a plastic container, which is hung on the toilet bowl. With each flush, particles of the substance enter the system along with drains.
What does the consumer need to know?
Aeration VOCs do not allow volley discharge of wastewater (more than 100 l / h). For example, if there are frequent guests in the house, the consumption of wastewater (taking a bath, shower, etc.) increases dramatically, due to which the colony of bacteria that is used for cleaning is partially (or completely) washed out. And consequently, for some time after a volley discharge, the installation will not be able to treat wastewater to the indicators indicated in the passport. A prolonged power outage also negatively affects the operation of systems of the first type, namely, it leads to the partial or complete death of a bacterial colony. True, some manufacturers "forget" to notify the buyer about this. Others argue that this is not a significant drawback of the devices, because you just need to put the bacteria bought in the store for septic tanks into the container, and the installation will begin to function as before. This is true, but reaching the degree of wastewater treatment declared by the manufacturer will occur in this case no earlier than in two to three weeks.
But for complex VOCs, neither a salvo dump nor a power outage threatens negative consequences. The reason for this is in the design differences between the installations of the first and second types. The fact is that in aeration VOCs, aerobic and anaerobic processes occur in one volume, where, due to aeration, there is a constant mixing of activated sludge. In complex VOCs, sludge is deposited in a separate chamber, where it is in a state of relative rest, and since bacteria in such systems live not only in water, but also in a bioreactor, they are not threatened by washing out with abnormal effluents, as well as death due to shutdown electricity. Even with a long break in the power supply, the bacteria on the biofilter are alive for three months. The output to the operating mode declared by the manufacturer occurs 4-10 days after the start of the installation.
Household waste (toilet paper, hygiene items) should not enter the aeration installations, as this can lead to blockage of the pumps that ensure the operation of the station. In addition, it is not desirable to drain chemical household detergents there, which worsen the conditions necessary for the vital activity of bacteria. But complex installations are more “loyal” to these factors, mainly due to their design features. Household debris (toilet paper, napkins, food debris, pet hair, polymer films) that has fallen into them remains in the settling chamber and cannot enter the section where the pumps are located. A small amount of chlorine-containing preparations (washing powder, bleaches), which, together with water, entered the VOC of the second type, will also not lead to a loss of system performance.
Both types of devices are volatile - the compressor (pump) must operate in continuous mode. However, complex VOCs have somewhat lower electricity consumption due to the fact that they do not use a compressor, but a timed pump (15 min./on - 15 min./off).
On the Russian market there are systems of varying complexity from both domestic and foreign manufacturers. In some of them, the cleaning process is controlled by a programmable controller that changes the operating mode of the installation based on the amount of incoming wastewater. If there are not many of them, the controller switches the system to an economical mode, with volley discharges - to a forced one. Although automation simplifies the operation of the system, it significantly increases the cost of VOC and its further maintenance.
Where to take drains in a country house
When installing equipment, one of the main questions is where the water treated in the installation goes. The easiest option is to divert it by gravity. After treatment in VOCs, wastewater is discharged directly onto the terrain or into a drainage network (trench, roadside ditch) at least 80-90 cm deep, protected from flooding. The second option is a filter well, used in cases where gravity drainage is not possible.
From the VOC, at a distance determined by the project, a reinforced concrete well is made about 3 m deep at the bottom of which crushed stone is poured (in order to increase the system performance). The capacity of the well depends on the type of soil.
In sandy soils, it is 80 l / day. per 1 mg of the area of the outer surface of the filter cylinder of the well, in sandy loam - 40 l / day. In clay soils or at high groundwater levels, this scheme does not work. In these cases, drainage pumps are used. For pumping purified water from VOCs, submersible devices with a conditional passage (maximum size of impurities) of 10-12 mm are used. The pump can be installed directly in the last chamber of the VOC or in an additional intermediate well, it must be sealed. This is necessary so that the pump does not also pump groundwater.
When installing a wastewater treatment system, it is important to consider that it should be located at a distance of 3-5 m from the cottage, so that in winter the effluents coming from the house do not freeze on the way to the VOC
Prices
Manufacturers indicate the cost of installations in different ways. Some call the price only for the equipment itself, others - for the turnkey system, that is, taking into account installation.
When choosing devices for wastewater treatment, it is better to focus on a full range of services. On average, VOC + delivery to the customer's site + installation will cost from 80,000 rubles. (installation volume is designed for four users) up to 140,000 rubles. (for ten users).
For some systems, monthly service activities may be required, the cost of which per year sometimes reaches 20% of the equipment price.
The general rule for all installations is to clean the settling chamber on average once a year from the accumulated excess sludge using a sewage truck. The cost of sewer services is 750-800 rubles / m 3.
What volume of wastewater installation to choose
The choice of a household treatment plant for specific building conditions is a complex multi-factorial task. First of all, it is necessary to calculate the performance of the equipment, since the size of the tank depends on this.
The specific rate of water disposal (according to SNiP 2.04.01-85) is from 200 to 300 liters per person per day and includes the use of a toilet, bath, shower, kitchen sink and washing machine. A family of three to four people spends an average of 200 liters of water per day on washing, washing dishes and washing, another 200 liters on the toilet, and 400 liters on a shower and bath.
In total, 800 liters are obtained. The size of the container is chosen taking into account that its working volume exceeds the daily rate of water consumption by three to five times. Therefore, in our example, a 4 m 3 tank is needed.
Do-it-yourself installation of an aeration station (VOS) - photo
a) Preparation of the subsystem pit b, c) The installation body is placed in the pit, d, e) Insertion of underwater and drainage lines into the body of the treatment plant f, g) Installation of electrical equipment, filling the installation with water and sprinkling with sand, h) The outer part of the aeration station
SEPTIC, BIOSEPTIC OR BIOLOGICAL TREATMENT STATION - TO CHOOSE FOR A PRIVATE HOUSE?
Previously, it was more difficult to organize “life support” according to urban standards in rural areas than in space. Fortunately, times have changed, the issue is also being resolved where the connection to the centralized water supply and sewerage is a matter of an unrealistically distant future. It is simply solved locally for one or several households - by drilling an artesian well and choosing an autonomous sewerage system.
What to prefer - a septic tank, a bioseptic tank or a biological treatment plant?
All options for local treatment systems (VOCs) have both “pluses” and minuses. Let's figure it out!
Local principles
Let's start with some science. It must be understood that any modern device that solves the “toilet” problem (by the way, including the dry closet) works thanks to microorganisms. As a result of the vital activity of these creatures invisible to the eye, biological oxidation processes take place in the effluents. The solid waste fraction decomposes, other organic compounds are formed, and the water settles. Everything is simple, but there is a nuance. Biological oxidation is of two types: aerobic (when the process goes with oxygen access) and anaerobic (without access).
And the bacteria involved in these processes are different. When aerobic are taken into account, the degree of purification complies with current hygiene standards; when anaerobic are working - it does not correspond, and additional cleaning is required.
What is a septic tank
In fact, a septic tank is a sedimentation tank for sewage waste with anaerobic bacteria. Structurally, they are a tank - sealed or without a bottom. There are models consisting of non-
how many containers connected to each other with nozzles and overflows. Heavy particles sink to the bottom, the most liquid fraction sequentially flows from chamber to chamber. Defending in this way, the plums are gradually cleaned.
Theoretically, the more chambers (tanks) a septic tank has, the better and more reliable it is. But in practice, in complex systems, the risk of breakdown is higher, their operation is more expensive, since many components require periodic maintenance. In addition, as a rule, the largest amount of sediment remains in the first section. So it’s not worth unnecessarily complicating the septic tank, three containers are the optimum.
part of a larger whole
A septic tank is not a self-sufficient device. Thanks to anaerobic processes, plums will leave about 65% of pollution in it. Where to put the foul-smelling moisture, which is still far from ideal? It is poured into a drainage well or taken away through the so-called "filtration field" (a piece of land, arranged away from the house in a special way to purify water by filtering it through the soil). Therefore, it is necessary to have this drainage well or a place sufficient for organizing a “filtration field” on your land plot. What to do with the sediment accumulating at the bottom of the chambers? It is periodically raked out. Alas, one cannot do without a vacuum cleaner. This means that it is necessary to ensure the free access of the sewer truck to the septic tank. These points will have to be taken into account when choosing an autonomous sewage system.
"Pros" and "cons" of septic tanks
Maintaining performance after long breaks in use.
Some models do not require an electrical connection.
Low degree of wastewater treatment - up to 65%.
Unpleasant odors are possible in the vicinity of the unit.
Installation requires a significant amount of space on the site.
Access roads are required for maintenance.
Difficult installation of volumetric and heavy equipment.
A septic tank is not the best solution if the groundwater level is high and if the area is clayey.
What is a bioseptic
This is a type of septic tank in which the cleaning process is enhanced by regular loading of bacterial preparations.
Its design provides for a biofilter - a small reservoir with a chemically inert, decay-resistant backfill. It can be, for example, foam balls, shungizite, expanded clay or shell rock. Backfill is an excellent medium for the growth of bacterial colonies and at the same time plays the role of a mechanical filter - it retains solid fragments of sewer drains. The degree of purification in a bioseptic tank is somewhat higher than in a conventional one, and less sediment is formed at the bottom of the chambers. That is, ceteris paribus, the sewer will have to be called less often.
What is an aerotank
In fact, initially the aerotank was called a reservoir in which the treated effluents are mixed with activated sludge - a biocenosis of microorganisms capable of absorbing organic matter. Today, the installation of deep biological treatment, including this tank, is often called an aerotank. What kind of bioseptic? You could probably say that. But, definitely, the difference between an aeration tank and a septic tank with a biofilter is fundamental: other bacteria, aerobic, are used here.
The operation of the system is based on biological oxidation with the access of air, which is pumped by the compressor. Due to aeration, the oxidation process occurs evenly throughout the volume. The "final product" - odorless sludge - is fed into a special compartment. Filtered water does not need additional purification!
ON A NOTE
Any LOS is designed for a certain number of users. To calculate the volume of the treatment plant, it is recommended to start from 200 l/day per person. The volume of simultaneous discharge of effluents (“volley discharge”) is also important. This indicator can greatly affect the quality of cleaning. The greater the throughput of the VOC per day, the more it should have a margin for the simultaneous reception of discharges from various plumbing units within an hour.
"Pros" and "cons" of the aeration tank
A high degree of wastewater treatment - the product is odorless at the outlet.
Possibility of installation in a ventilated basement. The aeration tank does not have to be buried in the ground, like a septic tank (a fan riser is required!).
Space is saved on the site - the "filtering field" is not needed.
In winter, an aerotank is more efficient than a septic tank (aerobic processes occur with heat release, anaerobic processes with absorption).
