Sewage treatment facilities OS, WWTP, BOS. Wastewater treatment: methods and modern techniques Filtration fields and other methods of wastewater tertiary treatment
Considering the fact that wastewater can pose a threat to life, and in addition to this, the environment suffers from them environment, GOST was adopted, which imposes special requirements on them. Control was entrusted to the environmental service.
An accounting system has been adopted, where indicators and data are entered after several samples of waste water are taken for analysis. Sanitary standards began to prescribe permissible standards and concentration conditions (MPC SanPin 4630-88 “Permissible standards for polluting wastewater”), and the same rules regulate COD and BOD.
Modern technologies make it possible to bring the composition of such wastewater to an acceptable standard. In most cases, certain technologies are used for these purposes, developed for processing substances of a certain type contained in liquid waste.
The classification of waters, which are commonly called wastewater, is carried out in accordance with the standards adopted in the relevant GOSTs, dividing them into:
- domestic, that is, wastewater from apartments and houses. These types of waste pose a serious danger because they contain organic matter, which is a breeding ground for various pathogenic bacteria. Therefore, household wastewater containing organic waste, are subject to mandatory disinfection;
- production, they are dumped by factories or other facilities where industrial technology require the use of water;
- natural (rain), atmospheric precipitation is related to their formation. This type of water also belongs to the waste type; sediment disposal is carried out through storm sewers. In this case, their direct discharge into water bodies is allowed.
Cleaning methods
There are many methods used to remove foreign substances from wastewater, we will look at the most functional of them:
- mechanical wastewater treatment, with its help suspended substances are removed; settling tanks, filters and oil traps operate on this principle. We’ll look at how the recycling process occurs in each type of device a little later, when we move on to wastewater treatment plants. Note that mechanical processing can be combined with other types;
- removal of contaminants chemically. Substances that have a beneficial effect on the creation of wastewater are added to untreated water. suitable conditions For chemical reactions, removing pollution. For example, this reduces the content of heavy metals and removes phenol. Chemical methods are designed for certain types of water, classified as wastewater;
- mechanochemical treatment. The only difference with processing, where mechanical technologies are used, appears in the form of the addition of coagulants, which cause the contaminants to precipitate;
- physico-chemical. When purifying waters considered waste, this technology widely uses galvanic processes, as well as flotation, ion exchange, etc.
- biochemical. The most environmentally friendly way to treat wastewater is this method; it is used to improve the results of mechanical purification technology. To do this, bacteria are added to the liquid, due to which the organic matter that is part of it begins to mineralize.
To speed up the processing process, aeration tanks have become widely used to construct biological wastewater treatment systems.
Treatment plants
For the treatment of wastewater related to household type, complex structures are used, the elements of which include:
- settling tanks, in which stratification of suspended particles occurs. Those with a high specific gravity fall out as sediment. Foreign elements that are lighter than liquid go into the surface layers;
- sand traps, they act as a filter in which impurities that cannot be dissolved, for example, sand, are collected. broken glass, slags, etc.;
- grates, their purpose is to catch large-sized debris contained in drains, for example, rags, plastic bags or branches.
Septic tanks are widely used in everyday life; in fact, they are mini settling tanks. To improve their effectiveness, special biological products called antiseptics are used. They contain different kinds microorganisms that contribute to the decomposition of precipitated organic matter.
To clean the sump when it is filled with sludge, a pump is used; this procedure only needs to be performed once every few years.
Video: How wastewater is cleaned.
The operating principle of the aeration tank is somewhat different from the settling tank; its operation diagram is shown in the picture.
Symbols used:
- A – aeration tank;
- B – settling tank for an oxygen-enriched mixture of sludge and sewage;
- c – pipe for supplying household waste (sewage is connected);
- d – influx of a mixture of wastewater and sludge;
- e – removal of purified liquid;
- f – pipe for pumping out excess sludge;
- g – sludge return.
Operating principle
- incoming wastewater “c” is combined with activated sludge in the aeration tank “A”;
- the mixture is abundantly aerated, which promotes the process of biological oxidation, which results in the rapid decomposition of organic matter;
- the oxygenated mixture of water and sludge “d” is supplied to tank “B”;
- the purified liquid “e” is pumped out as it is filled;
- the required amount of sludge is returned through the outlets back to the mixture with wastewater “g”, while its excess is discharged through the pipe “f”.
This method is quite effective if the correct calculation is made and compliance is observed. technological process, the water recycling rate is close to 98%.
Aero tanks purify water from organic matter, while removing nitrogen and fluorine, as well as their compounds, from it. The only drawback of this method is the sensitivity to the content of toxic and harmful compounds for bacteria in wastewater.
Note that dried sludge from an aeration tank, like sediment from a septic tank or settling tank, for domestic water, belonging to the waste type, are an excellent fertilizer.
For processing industrial waste from a factory or manufacturing enterprise structures are used whose principle of operation of water purification is similar to settling tanks, for example, oil traps installed at refineries. The only difference between these devices is related to the method of removing contaminants.
Flotators, these structures, allow us to speed up the process of separating light fractions from waste water. For this purpose, the settling tank is aerated.
Suspended solids contained in wastewater can also be removed using hydrocyclones. The principle of their operation is based on the use of centrifugal forces that arise during the rapid movement of water inside the cylindrical-conical body of the apparatus.
To remove finely dispersed suspended substances from a liquid, purification filter units are used; coarse sand, as well as mesh or fabric material can be used as a filter.
Disinfection
Separately, it is necessary to talk about disinfection; this is the treatment that wastewater undergoes before it is discharged, which is carried out to destroy pathogenic microorganisms. This procedure is carried out in tanks identical to settling tanks. Chlorine or bleach is used to treat domestic wastewater.
Sewage treatment is an indispensable process as it makes sewage waste safe for people and the environment. Today, technological progress has a negative impact on the water resources of our planet, so every drop counts. For this reason, treatment methods have been developed that help reuse wastewater to irrigate land or simply replenish the soil. In today's article we will discuss with you the main methods of filtering sewer fluid.
First, let's find out what the concept of wastewater refers to? For this understanding, it is customary to take all the liquid, with and without impurities, that is discharged into the sewer system. Its important characteristic is the presence of contamination obtained in a certain field of application. It is worth considering that precipitation liquid is also taken into account here.
Types of pollution
Wastewater treatment involves a process that takes place during correct selection equipment. It is worth considering that its important component is compliance a certain type pollution. It is for this reason that let’s find out their types that may be found in wastewater:
- Mineral contamination. 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 organic chemicals and polymers.
- Biological components. They are represented by bacteria and various other microorganisms.
Attention! In most cases, a sewer drain contains all three components. If this is household waste, then organic matter will be related to mineral substances as 3 to 2. As for bioorganisms, their quantity depends on the environment.
Standards for cleaning
Any water treatment plant is required to perform a certain level of processing. It is worth noting that the 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 processing should be present in an amount of no more than 0.1 mg per liter.
The requirements for household waste 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 enter the environment. For violation of this regulation, the owner of the house will be held administratively liable.
Important! Today, 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 inspection can also make these claims regarding the discharge of runoff into the soil.
Wastewater treatment methods
Based on the variety of methods for filtering and purifying wastewater, today they can be divided into types. Namely, there are two types of wastewater treatment methods:
- Destructive species;
- Recovery methods.
For the first characteristic feature there is a process of dividing wastewater 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 sewer 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 new ideas and methods appear to purify wastewater. After all, do not forget that this is an additional water resource. In this section we will look at each of the types separately, but first let’s list them:
- Mechanical;
- Biological;
- Physico-chemical;
- Disinfection method;
- Thermal recycling.
Let us consider in detail the methods of wastewater treatment.
Mechanical method
This is one of the simplest options. The process itself involves removing from the wastewater all components that do not dissolve. What are these components? These primarily include solid particles and fat. Sewage water is passed through a sieve and sedimentation tank, which then only allows liquid with small particles to pass through.
The most the best option mechanical cleaning sewage water is considered to be a membrane method. Its main feature is nothing less than the best purification process. The main thing is not to forget that this type filtration gives a result of 70% and is the start for the biological method.
Biological purification process
Wastewater treatment with biological substances is carried out through 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 wastewater gets rid of nitrogen and phosphorus, which are dangerous to 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 using air, that is, aerobic bacteria, then it is possible to install a biofilter or aeration tank. These designs have high purification efficiency and can combat activated sludge. With anaerobic microorganisms, a fermentation process occurs, which converts organic matter for methane and carbon dioxide.
For such cleaning, biofilters and aeration tanks with activated sludge are used. They have a high degree of purification and are more effective than biofilters for wastewater treatment. In aeration tanks, water is aerated and undergoes deep biological purification. In addition, the result is activated sludge, which is good fertilizer. Anaerobic wastewater treatment is carried out without oxygen. When exposed to anaerobic bacteria, the fermentation process occurs and organic matter is converted into methane and carbon dioxide. It is worth noting that the second method is slightly cheaper.
Attention! IN modern devices two types of microorganisms are used, which can easily be used even in industrial sewers.
Physico-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 for industrial enterprises. The basis of the treatment process involves the destruction of the organic components of water to obtain inorganics.
- Coagulation is the purification of water, which is carried out when components stick together under the influence 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 sediment to form. The formed flocs are engaged in wastewater treatment.
The physicochemical 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 very high percent cleaning. This method can easily automate the dimensions of filtering structures, which will reduce the sensitivity of the action.
Disinfection
This method is reproduced using exposure to ultraviolet rays, chlorine or ozone. Typically, the method is used to disinfect water before discharging it into a reservoir. The most effective process is considered to be using rays, as it is safe. It is worth considering that their effect can have a detrimental effect on bacteria and various viral microbes.
A type of cleaning based on chlorination involves disinfection of all microorganisms with chlorine. The main disadvantage of this mechanism is the creation of toxins and carcinogenic compounds. It is for this reason that you should be very careful when using this method.
Ozonation is treatment with ozone. Everyone knows that this is a type of gas that contains three molecules of oxygen, 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 area of its use is in industrial production.
Thermal recycling
Thermal treatment of sewage waste is carried out in situations where other methods do not produce results. The principle of operation is to spray liquid into a combustion fuel torch. This is very effective method, but due to its price and volume it is found mainly in production.
Attention! Modern treatment facilities carry out the process in several steps, so they are often programmed to use several methods.
So, the purification process sewer water- This required condition operation of the wastewater disposal system. It is worth not losing sight of the fact that these requirements are regulated by sanitary and legislative standards.
Sewage wastewater treatment This is a set of mandatory activities. Its implementation is regulated by current legislation and is necessary both to protect the environment and to renew water resources. Modern purification technologies using various methods make it possible to ensure maximum purity of the liquid returned to nature.
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What is meant by sewerage wastewater?
Sewage wastewater is usually called:
- all liquid waste from human life and activity, the so-called household waste;
- industrial wastewater, water used directly in production, as well as for cooling systems;
- atmospheric precipitation that enters the sewer system through the storm sewer system.
By type of pollution, waste is classified as follows:
- Mineral containing:
- salt;
- sand;
- clay, etc.
- chemical organics;
- polymers.
Generally, sewage is a combination of all types of contaminants, making necessary their multi-stage purification.
Cost of sewerage wastewater treatment
| Name of service | Price |
| Maintenance of heating points (independent scheme) | from 6,000 rub/month |
| Maintenance of heating points (dependent circuit) | from 10,000 rub/month |
| Maintenance of UUTE | from 3,000 rub/month |
| Installation of UUTE | from 250,000 rub. |
| Hydraulic tests (pressure testing) | from 7,000 rub. |
| Chemical flushing of the heat exchanger | from 8,000 rub. |
What methods are used to clean sewage?
The variety of contaminants makes it necessary to purify sewage wastewater using a combined scheme using the following methods.
- Mechanical.
Used to remove large particles and insoluble residues and serves preparatory stage for subsequent biological cleaning.
Sorting of this group of waste can be done in the following ways:
- straining;
- filtration;
- settling;
- centrifugal filtration.
The combination of these methods used in practice can significantly increase the efficiency of mechanical cleaning.
This method is used, as a rule, for the purification of industrial wastewater and consists of adding chemical reagents that help convert soluble components into insoluble ones for their subsequent removal mechanically.
The action of reagents can also be aimed at reactions such as:
- neutralization;
- oxidation;
- recovery.
In practice, due to its high cost, chemical method V pure form used extremely rarely.
Being a combination of the use of physical and chemical properties liquids and microelements, this group of methods is considered the most effective for treating a wide range of wastewater, including industrial waste.
The following cleaning methods are distinguished:
- electrochemical;
- coagulation;
- sorption;
- ion exchange;
- extraction, etc.
It should be noted that the integrated use of the physicochemical method allows not only to obtain an almost pure liquid at the output, but also to completely automate the entire process.
These cleaning methods are based on special bacteria that are capable of processing human waste products with a purity level of the liquid at the outlet of up to 95%.
By type, bacteria can be:
- aerobic, which require air to live;
- anaerobic, living without oxygen.
The use of bacteria is considered the most promising direction in matters of purification of contaminated wastewater, however, this method is not acceptable for processing wastewater from industrial enterprises.
However, in the residential sector and in urban areas this method is used quite widely.
It is used in cases where liquid purification is impossible, as well as for liquid waste directly after the relevant processes have been carried out. The essence of the method is to spray contaminated liquid over a burning fuel torch.
Calculate the cost of sewerage wastewater treatment for you
To select the optimal treatment method, sewage effluents in a specific area are subject to careful analysis to determine their composition, on the basis of which the most effective combination of methods is developed.
The purification processes themselves take place at specialized stations, which are complex system from tanks, settling tanks, filtration modules, etc. The composition of the equipment is also determined by the composition of the specific waste.
Thus, sewerage wastewater treatment is a process that involves the use of a variety of methods and technologies. The general reduction in water resources increases the importance of this area, and government regulation is an additional incentive to improve technology in this area.
The state of the environment today, unfortunately, leaves much to be desired. This is the result of careless use natural resources. Human consumption of water is constantly growing, and reserves clean water in nature decrease every year. Usage detergents and various household chemicals very pollutes wastewater modern cities, which significantly complicates wastewater treatment. Wastewater contains a variety of pollutants, from mechanical components to complex chemical compounds Therefore, wastewater treatment is a complex and multi-level process.
All wastewater treatment methods can be divided into destructive and recuperative. The result of destructive cleaning methods will be the decomposition of complex polluting compounds into simple ones; they will be removed from the water in the form of gases, either precipitate, or remain dissolved in the water, but neutralized. The result of recuperative treatment methods will be the extraction of all valuable substances from wastewater for further processing.
Wastewater treatment methods
- Mechanical
- Biological
- Physico-chemical
- Wastewater disinfection
- Thermal recycling
1. Mechanical method simplest. Mechanical treatment removes insoluble components that pollute water, both solid and surface fatty contaminants, from wastewater. Wastewater first passes through screens, then through sieves and settling tanks. Smaller components are precipitated by sand traps. Wastewater purification from petroleum products is carried out using grease traps and gasoline oil traps. An improved mechanical cleaning method - membrane - is used in conjunction with traditional methods and allows for more thorough cleaning. Mechanical wastewater treatment is a preparation for biological treatment and allows you to remove up to 70% of impurities from domestic wastewater, and up to 95% from industrial wastewater.
2. Biological wastewater treatment occurs due to the vital activity of microorganisms capable of oxidizing organic substances. The basis for the development of this method is natural cleaning rivers and reservoirs with the microflora inhabiting them. Thus, the wastewater is freed from organic nitrogen and phosphorus. Biological treatment can be aerobic or anaerobic.
Construction for aerobic wastewater treatment due to the activity of bacteria
- Aerobic wastewater treatment is carried out using aerobic bacteria, which require oxygen to function. For such cleaning, biofilters and aeration tanks with activated sludge are used. Aerotanks have a high degree of purification and are more effective than biofilters for wastewater treatment. In aeration tanks, water is aerated and undergoes deep biological purification. In addition, the result is activated sludge, which is a good fertilizer.
- Anaerobic wastewater treatment is carried out without oxygen. When exposed to anaerobic bacteria, the fermentation process occurs and organic matter is converted into methane and carbon dioxide. Metatenks are used for this method. Anaerobic treatment requires less expense than aerobic treatment, since it does not require aeration.
3. The physicochemical method includes electrolysis, coagulation and precipitation of phosphorus with iron and aluminum salts.
4. Disinfection of wastewater occurs by ultraviolet irradiation, chlorine treatment or ozonation. Used for disinfection before discharge into water bodies.
- Disinfection with ultraviolet irradiation is more effective and safe method compared to chlorination, since this does not produce harmful toxic substances. Ultraviolet radiation has a destructive effect on almost all microorganisms and effectively destroys the causative agents of cholera, dysentery, typhoid, viral hepatitis, polio and other diseases.
- Chlorination is based on the ability of active chlorine to have a detrimental effect on microorganisms. A significant disadvantage of this method is the formation of chlorine-containing toxins and carcinogens.
- Ozonation - disinfection of wastewater with ozone. Ozone is a gas consisting of triatomic oxygen molecules, a strong oxidizing agent that kills bacteria. This is a rather expensive disinfection method in which the harmful substances: aldehydes and ketones.
5. Thermal recovery is used for process wastewater when other methods are ineffective. Its essence is that sprayed wastewater is disinfected in a combustion torch.
At modern treatment plants, wastewater undergoes stage-by-stage treatment, while the methods described above are consistently applied.
Thermal wastewater recycling consists of disinfecting wastewater in the flame of burning fuel
Stages of wastewater treatment at wastewater treatment plants
- preliminary mechanical cleaning;
- biological treatment;
- post-treatment;
- disinfection.
Mechanical cleaning equipment
- gratings - rods rectangular shape with gaps up to 16mm;
- sand traps (installed when cleaning more than 100 m3 per day);
- averagers (installed if averaging of the composition is necessary);
- settling tanks (there are horizontal, vertical, radial, two-tier);
- septic tanks (used to treat wastewater going into filter trenches, wells and underground filtration fields);
- hydrocyclones (needed to clean wastewater from suspended solids);
- centrifuges (they release finely dispersed substances when reagents cannot be used);
- flotation units (used to separate oils, fats, petroleum products);
- degassers (remove gases dissolved in water).
Sludge pump - a facility for treating wastewater with activated sludge
Biological treatment facilities
- pre-aerators and biocoagulators (reduce the concentration of heavy metal ions and other pollutants);
- biological filters;
- aeration tanks, suction pumps, metatanks (structures for purification by aerobic and anaerobic methods);
- secondary settling tanks, desilting tanks and filtration fields (designed for complete biological treatment drains);
- biological ponds (intended for deep cleaning wastewater containing a lot of organic matter).
When treating wastewater, neutralization and filtration are used. Disinfection or disinfection is carried out with chlorine (chlorine management is required) or electrolysis (the construction of electrolysis plants is required).
Those wishing to familiarize themselves in detail with the structure and operating principle of the biological treatment station will be helped by watching the video.
As you can see, wastewater treatment is a multi-stage process that requires a scientific approach and compliance with all rules and sanitary standards. The considered methods of wastewater treatment are used in combination. The choice of method depends on the nature of the wastewater, its quantity, type, as well as the concentration of pollutants.
