Norms and methods of sewer water treatment. Wastewater treatment: methods and modern techniques Norms for cleaning
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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 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 Today, this is an outdated method.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: a septic tank, an anaerobic bioreactor, a stage I aeration tank - a biofilter, a sump, a stage II aeration tank, a secondary clarifier - a contact tank, a 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 interruption 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 few 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 body of the installation 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 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 “pros” and cons. 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 drained 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, the aerotank is more efficient than a septic tank (aerobic processes occur with heat release, anaerobic processes with absorption).
Human life is inextricably linked with water. Therefore, in the construction of housing, one of the first concerns is the construction of a water pipe. But if water is supplied to the house, then you need to take care of the disposal of wastewater. Wastewater treatment systems must be used to recycle used water and keep soil and water clean. Let's consider what installations can be used for sewerage equipment in a private house.
Today, few people are satisfied with the prospect of living in a house devoid of amenities, even if it is just a dacha. Most owners strive to make their home as comfortable as possible: organize heating, conduct water into the house.
But if there is a water supply system, then a sewerage system is also needed - a system for diverting and processing wastewater. Since far from all suburban settlements have a centralized system for collecting and processing domestic wastewater, a local wastewater treatment system is being built.
Wastewater treatment methods
To clean domestic sewage, as a rule, the following cleaning methods are used:
- Mechanical - settling, filtering.
- Biological - processing of wastewater by microorganisms.
In nature, there are two types of bacteria that can effectively clean drains:
- Anaerobes are microorganisms that carry out their vital activity without oxygen.
- Aerobes are bacteria that do not "work" in an oxygen-free environment.
As practice shows, it is possible to achieve the greatest effect in wastewater treatment if a combination of several treatment methods is used. The modern treatment system provides for the initial settling of wastewater, and then their biological treatment using anaerobes and aerobes.
Anaerobic septic tanks
A septic tank is an installation in which drains go through several phased stages of treatment. The principle of operation of a septic tank is to settle wastewater and process organic matter by anaerobic bacteria. To achieve the best quality of cleaning, septic tanks are made multi-chamber. The main part of the solid waste settles in the first chamber, and pre-purified water flows into the subsequent chambers.
Organic inclusions, which make up most of the pollution of domestic sewage, decompose under the action of anaerobic bacteria. Organics decompose into simple components - methane and water, and insoluble residues settle to the bottom of the chambers.
Treatment of wastewater with aerobic bacteria begins after it leaves the septic tank and enters the aeration fields - devices necessary for post-treatment of wastewater. On aeration fields, wastewater is additionally filtered, passing through a filter made of sand and gravel. Thus, after going through all the stages, the water is purified by almost 100% and does not harm the environment.
Cleaning steps in an anaerobic septic tank
- Stage one. It is carried out in the primary sump. There is a process that is commonly called clarification of drains. In the first chamber, the contaminated water is separated by specific gravity. Particles that have a heavy weight settle to the bottom, inclusions that are lighter than water rise to the top. In the center of the primary clarifier, where the overflow pipe to the second chamber is located, clarified effluents are collected. Settling continues in the second chamber, only here the sedimentation of smaller inclusions, which are in the liquid in suspension, is already taking place.
Advice! Septic tanks are built in such a way that drains from chamber to chamber flow slowly. Only at a low speed of movement is it possible to ensure high-quality sedimentation.
- The second stage is biological. Organic matter that has settled to the bottom undergoes biological processing by anaerobic bacteria. During the fermentation of the sediment, heat is released, so the temperature in the septic tank is always elevated. This circumstance allows the use of septic tanks not only in summer, but also in winter.
- The last stage of cleaning takes place on the filtration fields. The effluents clarified in the septic tank are supplied here through pipes. Holes are made in the pipes through which water seeps into the soil filter. Passing through a layer of sand and gravel, the water is filtered. In addition, it is additionally cleansed with the help of aerobes that live in the soil.
Aerobic type septic tank
In addition to traditional septic tanks, modern systems of biological wastewater treatment - VOCs, additionally equipped with aerators, are widely used today. In such stations, wastewater is alternately processed by anaerobic and aerobic bacteria, as a result, at the outlet of the treatment plant, the water is 98% purified, so there is no need to build filtration fields.
Water purified in VOCs can be discharged onto the ground or into the nearest body of water without harm to the environment. If necessary, water can be directed to a storage well for domestic use, such as lawn or garden irrigation.
Stages of wastewater treatment in aerobic septic tanks
- The first stage is upholding. Just like in conventional septic tanks, VOC uses such a simple but reliable mechanical cleaning method.
- The second stage is the processing of the sludge by anaerobic bacteria. Organic matter that has fallen in the form of a precipitate is processed by anaerobic bacteria. That is, up to this point, there are no differences in the operation of a simple septic tank and VOCs.
- The third stage is processing with the help of aerobic bacteria. When the aerator is turned on in the chamber, the stage of aerobic cleaning begins. In an environment saturated with oxygen, bacteria efficiently and quickly process most of the organic inclusions.
- Stage four - again upholding. After aerobic treatment of wastewater, water enters the secondary clarifier, where the insoluble sediment - sludge - settles. Purified water enters the outlet, and activated sludge is reused in the purification process. As excess sludge accumulates, it will need to be removed from the sump.
Simple septic tank or VOC?
What kind of wastewater treatment system should be preferred when building a local sewerage system? There is no single answer to this question. When choosing an installation, local conditions will need to be taken into account. Let's conduct a small comparative analysis of septic tanks and VOCs:
- Space required for installation. To install a modern VOC, as a rule, one or two square meters of area is sufficient. If you need to install a septic tank, you will need a large area. The septic tank itself is somewhat larger than the VOC, but the main area will be required for the construction of filtration fields necessary for the post-treatment of wastewater.
- Geological characteristics of the site. If it is decided to install a VOC, then the geological characteristics of the site can only affect the choice of VOC modification. But the arrangement of filtration fields on clay soils is an intractable task.
Advice! If soil water is high on the site, then you should purchase a VOC with forced drainage, that is, equipped with an additional pump.
- Autonomy. If the septic tank is a completely autonomous installation, then the VOC requires power to work.
Advice! If the local sewerage system is equipped with a volatile wastewater treatment plant, then during a power outage it is necessary to reduce the use of water to a minimum. Otherwise, overflow of the chambers may occur, since the pumps pumping wastewater do not work.
- Service. Both a conventional septic tank and VOCs need regular maintenance. The septic tank will have to be cleaned of accumulated sediment about 1-2 times a year using sewage equipment. The cleaning of the sludge collector in the VOC should be carried out more often - about once a quarter, but this work can be easily done on your own.
Advice! When choosing a place to install a septic tank, you need to take into account the need to clean it and leave free passage for the sewer truck.
- Price. A conventional septic tank is cheaper than VOCs. However, it is necessary to take into account the cost of building filtration fields, as well as the fact that filtration fields last no more than 10-12 years, after which they need to be changed.
Design
Having decided on the type of treatment plant, you can begin designing drainage systems for a country house. Most often, the project is made simultaneously with the project of the house. But if a building that has already been put into operation is being improved, then a sewerage project for a private house is drawn up separately.
When designing a wastewater disposal system, local conditions must be taken into account. Therefore, prior to the start of design work, it is recommended to carry out geological exploration, during which the following points will be clarified:
- features of the relief of the site;
- characteristics of the soil, to select the method of water drainage, it is necessary to assess the absorbency of the soil;
- the level of location and seasonal rises of groundwater.
Before the development of a project for a drainage system for a home is started, the following points need to be clarified:
- average daily water consumption in the house;
- frequency of use - year-round or periodically.
After collecting information, you can begin to draw up a project.
Tilt angle
An important point is the angle of inclination of the pipeline. This point is important in the construction of gravity systems. If it is impossible to comply with the required angle of inclination, it is necessary to plan the construction of a pressure system in which wastewater is pumped using a fecal pump.
Many home masters who undertake self-assembly underestimate this point, and meanwhile, errors in both directions reduce the efficiency of the system.
If the angle is not large enough, then the flow will move through the pipeline at a low speed. At the same time, some of the large inclusions will have time to precipitate in the pipes, and this is fraught with the formation of blockages. An angle that is too large will also disrupt the normal movement of the conveyed medium. Water will drain too fast, not having time to carry away heavy inclusions that will linger in the pipes, forming blockages.
The optimal angle of inclination depends on the diameter of the pipe that is used to create the pipeline. The smaller the diameter, the larger the slope angle should be. So, if pipes with a diameter of 50 mm are selected, then a slope of 3 cm per meter should be observed. When using 100 mm pipes, the slope should be 2 cm.
System elements
When creating a project, a diagram of internal and external networks is created. The internal networks include all the elements that are located in the house, these are:
- a riser connected to a fan pipe led to the roof;
- elements of plumbing (sinks, bathtubs, toilets, etc.);
- pipes connecting plumbing elements with a riser.
The boundary separating the internal and external networks is the pipe outlet through the foundation. External networks include:
- a pipeline connecting the output with a treatment plant;
- revision wells for network maintenance;
- cleaning plant.
When constructing a local sewage system, one cannot do without a local treatment plant. Depending on local conditions and the capabilities of the owners, this can be a simple anaerobic type septic tank or a modern local bio-treatment station.
Plumbing is an integral part of modern comfort, and where there is water supply, there must also be drainage. But what to do with the accumulated waste? Now there are many options for solving this problem, ranging from primitive recycling to complete purification of the contaminated fraction from process water. This article discusses the most common methods of wastewater treatment, the principle of their operation, the main pros and cons of such systems.
Wastewater treatment methods
First you need to understand what is wastewater? This category includes any drains that contain any impurities and contaminants. These include:
- Household sewerage of the residential sector. It contains mainly waste products, biological waste of animal origin, such as fat and food particles. Wastewater treatment technology can be done locally or globally;
- Industrial effluents contain production waste, chemical elements, polymers or petroleum products. The processing of such contaminants differs from cleaning domestic sewers, this process is more complex and includes a set of activities with several levels. Such installations are able not only to process wastewater, but also to provide the enterprise with water for production needs.
Thus, based on the type of sewage, it is possible to determine the type of treatment plant that will be most appropriate to achieve the desired result and level of treatment.
Wastewater treatment methods can be classified into three types:
- Mechanical methods of wastewater treatment. As a rule, this stage is considered preparatory, since this is the most primitive method in which there is no other than physical impact on pollution from large fragments. Mechanical wastewater treatment is carried out in several ways:
- Straining. At this stage, the drains are passed through a steel or plastic grate that holds large elements and fibers. Most often, such a mechanism is equipped with an electric drive, it rotates the grid during the water supply, and at the top point all contaminants are removed for disposal;
- Settling. The settling mechanism is based on the physical property of the material to settle on the bottom of the tank. Since water is lighter than the main types of pollution, all elements sink down and accumulate in the water column. After precipitation, contaminants are removed from the sump by emptying it or draining through the bottom of the channel;
- Filtration is carried out using a catching grid with a fine mesh. This method is justified in cases where there are no large contaminants in the effluents or as an intermediate stage of treatment;
- Separation or centrifugation. One of the most modern types of separation of water from dirty drains. The principle of operation of this device is based on the movement of water in a spiral in a special drum, in the process of such rotation, large and suspended particles are separated from industrial water.
This method is one of the main methods of wastewater treatment.
- Chemical methods of wastewater treatment. This method is designed to separate substances dissolved in wastewater from the bulk by adding special reagents, which, when released into a polluted environment, react with the liquid and contribute to the precipitation of harmful substances. Chemical wastewater treatment, depending on the additives used, is divided into two subsections:
- Neutralization with acids and alkalis. At this stage, chemicals are added to the drains, which bring the liquid to the required value and weight of hydrogen. Most often this method is used in the textile and other industries;
- Oxidation using chemical reagents, which can be liquefied chlorine and its other derivatives. The main direction in the processing of such an installation is the treatment of wastewater with a high content of heavy metals.
- Physico-chemical methods of wastewater treatment. This is one of the most advanced methods of disposal of contaminated liquid, which includes several stages of separation and removal of finely dispersed and hardly soluble organic and non-organic elements. As well as the previous methods of processing wastewater, this process can be of several types:
- Coagulation is an action based on coarsening by sticking together small particles when reacting with added reagents. The most commonly used salts are ammonium, copper and iron. In domestic conditions, it is rarely used due to the high cost and large dimensions of the equipment;
- Flotation. In this case, a special installation is needed, into which sewage flows, and natural or chemically created flotation agents, such as oil or petroleum by-products, are added. In order for the cleaning process to be continuous, compressed air is supplied to the separated chamber under high pressure, which, passing through the drains, forms a foamy emulsion. Flotation forms oxygen bubbles that capture molecules from the total composition and lift it to the upper layers. The result is an aggregation of elements in a dense foam. This method is used in metal mining to separate useful ore from other minerals. Also, flotation is used in modern urban wastewater treatment plants;
- Sorption cleaning of household drains. The most advanced cleaning method, it uses large sorbents of natural or chemical origin. Contaminated effluents are mixed with porous material, and after settling into a sediment, the filter is removed from the tank, and the technical fluid can be reused. The level of purification with this method reaches a degree of 95%. The main disadvantage of sorption is the high cost of components and equipment;
- Simple and reverse osmosis. In such a device, domestic wastewater treatment occurs as a result of squeezing water through contaminated drains and a membrane, or the reverse process with the passage of dirty water through a filter element and separation of waste molecules. The principle of operation in both directions is the same, it is based on the mechanical retention of particles that are larger than water molecules in a special grid. After the filter is filled, it must be removed and changed or cleaned.
All physical and chemical methods of wastewater treatment are mainly used on an industrial scale for large enterprises and factories. The production and household methods differ in the equipment used and the number of processes. But some units are also used in the private sector, for example, flotation or osmus.
- Biological method of sewage treatment. Most often, this method is used in the construction of treatment facilities for an individual dwelling with an autonomous communication system. Its principle of operation is based on the processing of contaminants by creating a nutrient medium for special bacteria intended for wastewater treatment. There are two types of microorganisms suitable for wastewater treatment:
- Anaerobic bacteria - live in a polluted airless sewer environment and feed on biological waste. Anaerobic wastewater treatment has a methane gas by-product, so the tank must be equipped with a gas vent. Another colony of bacteria is called useful sludge, as they live on sand particles contained in the aquatic environment;
- Aerobic bacteria, unlike the previous ones, need a constant supply of air, since they need oxygen for normal life. The waste tank must be equipped with a compressor unit and a supply of pipes for effluent enrichment.
Often, both options are used sequentially to achieve the desired result, then the level of sewage treatment can reach 98%. Such water cannot be used for food, but it is suitable for domestic needs, for example, for watering plants or cleaning. Often the aerobic scheme is used in conjunction with another oxygen method called flotation.
Note! Regardless of the chosen method of domestic wastewater treatment, its design and installation should be carried out by qualified workers, since it will be possible to independently calculate the required power only with a detailed study of all communication parameters.
Stages of wastewater treatment, stages and installation of an autonomous septic tank
Treatment of domestic wastewater in the enterprise and in the private sector are very different from each other. In individual housing, a combined treatment system is often used, which includes several stages of liquid treatment to the state of process water. The construction of such a structure begins with the calculation of power and location. As a rule, the septic tank is located at some distance from the residential building closer to the exit from the site. This is done so that during operation there are no problems with the removal of waste material and waste.
The next step will be digging a pit for the tanks. Many manufacturers make rigid plastic tanks with built-in baffles and compartments for overflow, filtration and recycling. Such a product is much more expensive than reinforced concrete rings, since its production is expensive, but has the advantage of ease of installation and maintenance, as well as space saving. Warranty for plastic containers for more than fifty years.
It is important to observe the dimensions of the pit so that it is 20-30 cm larger around the perimeter, this will facilitate installation and prevent the destruction of the walls of the pit.
Geotextiles are laid on the sand and gravel cushion, which will prevent the container from sagging under the influence of heavy weight. After ramming the base, the septic tank itself is mounted, it can be factory-made or made independently from reinforced concrete rings. If a plastic tank is used, then weighting must be placed on the bottom so that when precipitation occurs, the container does not float out.
The sewer pipe is connected along the top cover in such a way that there is an air gap between the accumulated drains and the incoming liquid. To prevent the entry of an unpleasant odor from the septic tank into the room, it is recommended to install a check valve that works only in one direction, regulating the flows.
Most often, the first stage of sewage water treatment is natural filtration from large fragments of non-biological origin. For this purpose, an overflow threshold with a sand trap is provided in the tank, which screens out elements unsuitable for processing from the bulk.
Anaerobic bacteria are located in the next compartment, which purify the liquid from large inclusions that are contained in the thickness of the drains. After processing the main pollution and turning them into carbon dioxide and methane, the bacteria partially die; in order to maintain the required number, it is necessary to periodically renew their population.
After overflow, the recycled water enters the aeration fields. Bacteria live here, feeding on biological waste when enriched with oxygen. Therefore, to ensure the process, it is necessary to continuously supply oxygen to the chamber; without it, all microorganisms will die.
Wastewater treatment is an indispensable process, as it makes sewage waste safe for people and the environment. Today, technological progress negatively affects the water resources of our planet, so every drop counts. For this reason, treatment methods have been developed that help the effluent to be reused for irrigation of land or simply replenishing the soil. In today's article, we will discuss with you the main ways to filter sewer fluid.
To begin with, let's find out what refers to the concept of wastewater? For this understanding, it is customary to take all the liquid with and without impurities, which is drained into the sewer system. Its important characteristic is the presence of pollution obtained in a certain field of application. It is worth considering that the liquid of atmospheric precipitation is also read here.
Types of pollution
Wastewater treatment involves a process that takes place with the right selection of equipment. It is worth considering that its important component is compliance with a certain type of pollution. It is for this reason that let's find out their species that may be in wastewater:
- Mineral pollution. This type includes all inorganic components, such as: salt, earth, etc.
- organic matter. This is a sewage liquid containing in its composition the remains of the world of flora and fauna. Their composition usually consists of chemical organics and polymers.
- Biological components. They are bacteria and other various microorganisms.
Attention! In most cases, a sewer drain incorporates all three components. If these are household drains, then organics will relate to minerals as 3 to 2. As for bioorganisms, their number depends on the environment.
Norms for cleaning
Any water treatment plant is required to perform a certain level of processing. It should be noted that regulated strict standards are prescribed only for the industrial sector. In addition, the ratio of each type of impurity is fixed by law. For example, iron after treatment should be present in an amount of not more than 0.1 mg per liter.
In relation to domestic plums, the requirements are more lenient. But this is no reason to relax. One of the most important rules for managing wastewater on a private property is that untreated wastewater cannot be released into the environment. For violation of this regulation, the owner of the house will be held administratively liable.
Important! To date, the state regulates only the maximum possible amount of impurities in water. At the moment, this only applies to draining into a reservoir. But remember that the test can also make these claims in relation to the withdrawal of runoff into the soil.
Wastewater Treatment Methods
Based on the variety of methods for filtering and treating wastewater, today they can be divided into types. Namely, there are two types of wastewater treatment methods:
- destructive species;
- recovery methods.
For the former, a characteristic feature is the process of dividing effluents into simple components, which can later be easily removed, for example, in the form of gas. The second types select all valuable substances from the sewage liquid in order to process them in the future.
The cleaning process - how to do it
Technological progress does not stand still, and therefore every day there are new ideas and ways to purify wastewater. After all, do not forget that this is an additional water resource. In this section, we will get acquainted with each of the types separately, but first, let's list them:
- Mechanical;
- biological;
- Physical and chemical;
- Method of disinfection;
- Thermal recycling.
Consider in detail the methods of wastewater treatment.
mechanical way
This is one of the simplest options. The process itself includes the removal from the drains of all components that do not dissolve. What are these components? First of all, these include solid particles and fat. Sewer water is passed through a sieve and a sump, which then only passes liquid with small particles.
The best option for mechanical treatment of sewage water is the membrane method. Its main feature is nothing less than the best purification process. The main thing is not to forget that this type of filtration gives a result of 70% and is the start for the biological method.
Biological cleaning process
Wastewater treatment with biological substances is carried out using the functioning of bacteria and microorganisms in the system. Their main feature is the ability to oxidize solid particles. The basis for the creation of this method was the microflora of natural water sources. Studies have proven that drains get rid of nitrogen and phosphorus, which are dangerous for the environment. Bacteria are of the following types:
- Anaerobic microorganisms that can function without air;
- Aerobic types cannot work without oxygen.
If cleaning is carried out with the help of air, that is, aerobic bacteria, then it is possible to install a biofilter or aeration tank. These designs have a high cleaning efficiency and can deal with activated sludge. With anaerobic microorganisms, a fermentation process occurs that converts organic matter into methane and carbon dioxide.
Biofilters and aerotanks with activated sludge are used for such cleaning. They are highly purified and more efficient than biofilters for wastewater treatment. In aerotanks, water is aerated and its deep biological treatment is carried out. In addition, the result is activated sludge, which is a good fertilizer. Anaerobic wastewater treatment is carried out without access to oxygen. Under the influence of anaerobic bacteria, the process of fermentation and the conversion of organic matter into methane and carbon dioxide occurs. It is worth noting that the second method is slightly cheaper.
Attention! In modern devices, two types of microorganisms are used, which can be easily used even in industrial sewers.
Physical and chemical method
These wastewater treatment methods are very effective and are based on the teachings of the sciences of chemistry and physics. These types include:
- Electrolysis is a very popular method in industrial plants. The basis of the treatment process involves breaking down the organic constituents of the water to produce inorganics.
- Coagulation is the purification of water, which is carried out when the components stick together under the action of forces. The result of the process is the formation of an aggregate.
- Precipitation of metal hydroxide flakes- this action is the result of the influence of coagulants, which cause precipitation. Educated flakes are engaged in wastewater treatment.
The physico-chemical process has a large number of advantages, for example, the removal of toxins and impurities that are not able to oxidize. It is also worth adding that this method provides a very high percentage of cleaning. This method can easily automate the dimensions of structures for filtering, which will reduce the sensitivity of the action.
Disinfection
This method is reproduced by exposure to ultraviolet rays, chlorine or ozone. Typically, the method is used to disinfect water before being discharged into a reservoir. The most effective process is considered to be with the use of rays, as it is safe. It is worth considering that their impact can have a detrimental effect on bacteria and various viral microbes.
The type of cleaning based on chlorination implies the disinfection of all microorganisms with chlorine. The main disadvantage of this mechanism is the creation of toxins and carcinogenic compounds. For this reason, you should be very careful when using this method.
Ozonation is the treatment with ozone. Everyone knows that this is a type of gas that contains three oxygen molecules, thereby forming a powerful oxidizing agent that kills microbes. It is important to say that this method is very expensive, so it is used very rarely in everyday life. The main scope of its use is manifested in the production of industrial sectors.
Thermal disposal
Thermal treatment of sewage effluents is carried out in situations where other methods fail. The principle of operation is to spray the liquid in the combustion fuel torch. This is a very effective method, but due to its price and volume, it is found mainly in production.
Attention! Modern treatment plants perform a process in several steps, so they are often programmed to use several methods.
So, the process of purification of sewage water is a prerequisite for the operation of the wastewater disposal system. It should not be overlooked that these requirements are regulated by sanitary and legislative norms.
