Water recycling. Wastewater treatment plant: what is wastewater treatment? Phosphate removal

In the process of urban wastewater treatment at Moscow treatment facilities, about 9 million cubic meters of liquid sludge is generated, requiring processing and neutralization.

Industrial methods are used for processing and disposal of sludge. Sludge neutralization is carried out in specialized facilities - digesters under thermophilic mode of fermentation (at a temperature of 50-53 0 С). In order to minimize the amount of waste to be disposed of, decontaminated sludge, pre-conditioned with a flocculant solution, is fed to decanters for dehydration, bypassing the washing and compaction stages in digested sludge thickeners. In the process of mechanical dehydration, the sludge volume is reduced by more than 9 times.

An analysis of best practices has shown that in modern conditions the use of centrifugal apparatus - decanters for the processing of sewage sludge is the most preferable.

In 2013-2014, the departments of the mechanical sludge dewatering shop of the Kuryanovsky treatment facilities in the Leninsky and Ramensky districts of the Moscow Region were reconstructed, during which 12 obsolete and obsolete chamber filter presses were replaced with modern dewatering equipment - eight decanters.

In 2017, the reconstruction of the mechanical dewatering shop at the Lyuberetsky wastewater treatment plant was completed with the creation of a single sludge dewatering center on the territory of the Novolyuberetsky wastewater treatment plant, as a result of which nine decanters were put into operation.

Modernization of dehydration shops allowed to solve key problems:

a reserve margin for equipment performance is provided, i.e. increased its reliability
decommissioned 34 digester sludge thickeners, which are sources of bad odors,
reduced downtime due to blockages by installing screens on the digested sludge,
the recycling of suspended solids with drain water has been reduced, thereby reducing the pollution load on the main facilities,
the number of service personnel has been reduced.

Problems of sludge disposal

The use of industrial methods of dehydration makes it possible to reduce the volume of sludge by more than 9 times.

Currently, the dehydrated sludge is taken out by third parties outside the territory of the treatment facilities in order to neutralize it or possibly use it for the production of finished products. On the basis of precipitation, technical/biological reclamation agents, biosoil, etc. are produced, which are used for the reclamation of disturbed lands, worked-out quarries, solid ground household waste, carrying out planning work. In the current environmental situation in the Moscow region, it becomes more and more difficult to carry out such work every year, and the costs of sludge disposal are steadily increasing.

The options for sludge disposal offered on the world market can be reduced to the following methods:

use of sludge for biosoil production;
sludge disposal based on modern thermal technologies and, as a result, obtaining secondary products from waste suitable for sale in the construction industry for the production of building materials or cement.

Benefits of biosoil production

One of the ways to solve the problem of polluted and degraded urban soils is the use of soils in the green construction of the city using dehydrated and neutralized sewage sludge.

Soil production technology solves several important environmental problems at once:

disposal of waste treatment facilities;
creation of a sufficient amount of conditioned soils in the city.

Advantages of the thermal method of sludge disposal

Given the complex ecological situation in the city, it was decided to use the dewatered sludge drying scheme at the first stage. At the same time, the volume of the sludge will decrease by more than 3 times, and the calorific value of the dried sludge will make it possible to use it as a fuel component in the production of finished products.

Since 2018, Mosvodokanal JSC has been working on the production of solid biological fuel (TBT) from mechanically dehydrated VOC sludge in accordance with Specifications"Solid biofuel" TU 38.32.39.-001-03324418-2017. TBT production is carried out on the equipment of EFN Eco Service LLC in the sludge drying department at a mini-CHP using biogas generated at treatment facilities.

At present, the obtained solid biofuel is transferred for use as an alternative fuel to the cement plants Holsim (Rus) SM LLC, BaselCement LLC and Heidelberg-Cement LLC.

The need of the population industrial enterprises and agriculture in fresh water is growing year by year. All countries of the world are concerned about its deficit, and the problem of the rational use of water reserves is becoming one of the priorities in solving state problems. The sources of the greatest water consumption are petrochemical, energy and pulp and paper enterprises, metallurgical plants, livestock industries. Water used in any way goes into the category of wastewater and the question of its further consumption creates a need to search for new types of its purification and reuse.

Existing waste treatment methods

The concept itself means the processing of water that has already been used in various ways so that it becomes again suitable for use. The cleaning process, regardless of the method, is a rather complex undertaking, and implies the strictest observance of technology. It can be compared with the work of an ordinary enterprise, since there is a raw material with which a number of actions have to be carried out - waste water, and a finished product, which is the ultimate goal of these actions - purified water.

Of all the existing processing methods, the appropriate method is determined individually for each type of wastewater, and depends on the nature of the pollution and the degree of harmfulness of impurities. There are the following methods:

mechanical;
biological;
physical and chemical;
chemical;
combined.

Technology mechanical way processing lies in the fact that by settling the raw material and subsequent filtration, up to 75% of coarse particles that cannot be decomposed are removed from it. These indicators are typical for domestic water treatment. Effluent, as a product of industrial consumption, after application mechanical way cleaning, loses up to 95% of all harmful impurities that got into it during use. After settling, the water passes through devices that trap insoluble impurities, such as sieves, gratings, sand traps, manure traps, septic tanks. These devices are able to retain coarse particles that are directly in the body of water. Those that linger on the surface due to their properties are removed by oil traps, settling tanks, gasoline and oil traps.

Application chemical method is the use of reagents. They react with pollutants, and in the form of insoluble grains they are removed to the residue. Thanks to the application chemical method the amount of insoluble particles is reduced by 95%, and soluble particles during processing - by 25%.

Physico-mechanical process Purification of polluted water according to the types of application of a particular method is carried out using several technologies. More often than others, for the dissolution of inorganic impurities, the destruction of organic and poorly oxidized substances, they resort to the use of oxidation, extraction, coagulation, and sorption. The use of electrolysis and ultrasound is also widely used.

Electrolysis destroys almost all harmful organic substances, and removes acids, metals and a number of other destructive substances from inorganic substances. This method is most effective for industrial water treatment at enterprises using lead and ore, as well as producing paint and varnish products. The use of ultrasound, ion exchange resins, ozone give excellent results.

biological method is based on the application of the laws of the natural process of biochemical and physiological self-purification of water bodies, and consists in the use of a number of biological devices, such as biofilters, volumetric aerotanks, biological ponds. The latter are nothing more than specific reservoirs in which wastewater is purified thanks to the organisms that inhabit the reservoir. And biofilters are coarse-grained material covered with the thinnest bacterial film, which creates a biological oxidation reaction, which leads to the destruction of contaminants.

Aerotanks - specialized tanks huge size from reinforced concrete, the cleansing basis of which is activated sludge, consisting of microscopic living beings and bacteria. All kinds of organic substances contained in wastewater, under the influence of the air flow entering the reinforced concrete structure, create for these living beings an optimal environment for vigorous activity, the result of which is the gluing of a number of bacteria into flakes and the release of unique enzymes that mineralize organic pollution. The flakes, increasing in volume, settle, separating from the purified water, which then enters other tanks. The smallest living organisms remaining in the sludge layer of sewage, such as rotifers, amoeba, ciliates and some others, devour non-coagulating bacteria, thereby rejuvenating the bacterial composition of the sludge layer.

Before biological treatment in aerotanks, wastewater undergoes mechanical treatment, and after the receipt of treated water biologically, into clean tanks, it undergoes a process of removing disease-causing bacteria by chlorination.

Biological wastewater treatment has excellent results for the removal of hazardous waste generated during the production of oil refineries, pulp and paper and other chemical enterprises, as well as for the treatment of municipal water waste.

The choice of technology for processing

Depending on the quantitative and qualitative level of pollution, the choice of technology for its purification and further application is determined. The degree of pollution depends on the industry and the technological processes that are the basis of their production. The most dangerous are those that burden the water with inorganic toxic impurities and poisons.

Today, the task of cleaning and processing wastewater obtained in the course of production activities falls on the shoulders of the heads of enterprises, and the state environmental services monitor the quality of this task. Undoubtedly, choose the best technological scheme pretty hard.

Sanitary standards are distinguished by high requirements for the quality of purified water and vary depending on how it will be used in the future: discharged into water bodies or re-participated in the production process of an enterprise. In any case, it is mandatory to comply with the established standards for the admissibility of the concentration of impurities in treated waters.

The video clearly shows the processing scheme:

Reset to environment household and industrial wastewater without pre-treatment would entail a real environmental disaster.

Insofar as chemical composition Waste with the development of technology is becoming more diverse and aggressive, wastewater treatment methods are constantly being improved.

Because of great variety soluble and insoluble pollutants in wastewater, it is not possible to create a universal method for their neutralization and removal.

Therefore, a whole set of methods is used at treatment facilities, each of which is focused on working with one or another group of substances.

All these techniques can be divided into several categories:

Mechanical.
Chemical.
Biological and biochemical.
Physical and chemical.

Each of the listed cleaning technologies includes several stages that require the use of certain technical devices, chemicals and biologically active preparations.

Wastewater treatment methods

Let us consider in more detail how exactly the disposal of waste masses is carried out. See below for physical-chemical and other wastewater treatment methods.

Chemical methods of wastewater treatment

Based on the use of chemicals, resulting in one of three processes:

Neutralization: this method is designed to neutralize acids and alkalis by converting them into safe substances. Such pollutants have to be dealt with in the treatment of wastewater from industrial enterprises. If both acidic and alkaline effluents are available, they can be neutralized by simple mixing. To neutralize acidic waters, alkaline waste, caustic soda, soda, chalk and limestone are used. To implement this method, enterprises install filters and various devices.
Oxidation: oxidation is carried out on those types of pollution that cannot be neutralized in other ways. Oxygen, potassium dichromate and permanganate, sodium and calcium hypochlorite, bleach and other reagents are used as oxidizing agents.
Recovery: using this method, it is possible to neutralize compounds of chromium, mercury, arsenic and some other elements that are easily recoverable. The reagents are sulfur dioxide, sodium hydrosulfite, hydrogen and iron sulfate.

Industrial water treatment

Disinfection of purified water is carried out using gaseous chlorine or bleach.

Biochemical

Within the framework of this technique, in addition to chemical reagents, various microorganisms are used that consume organic contaminants as food. Treatment plants based on this principle can be divided into two groups:

Working in natural conditions: they can be reservoirs (biopards), or “land” structures (irrigation field and filtration field), in which soil post-treatment of wastewater takes place. Such stations have low efficiency, require large areas and are highly dependent on climatic factors.
Working in artificial conditions: by artificially creating more comfortable conditions for microorganisms, the effectiveness of cleaning can be significantly increased.

Structures included in the latter category are divided into three types:

aeration tanks;
biofilters;
air filters.

Anaerobic treatment system followed by MBR treatment

Biofilter- is a plant in which there is a filter bed of expanded clay, slag, gravel or similar material. Colonies of microorganisms form a film on it.

air filter It is arranged in a similar way, but it provides for forced air supply to the filter layer. This allows you to increase its capacity up to 4 m and make the oxidation processes much more intense.

in aeration tanks Useful biomass exists in the form of activated sludge, which is mixed with incoming effluents into a homogeneous mass using various mechanical devices.

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Biological

For the treatment of wastewater containing only organic contaminants, a biological method is used. It differs from biochemical only in the absence of chemicals.

The most productive are aerobic microorganisms, for the vital activity of which oxygen is needed.

If they work in a building with artificial conditions, or in a biopond, air must be pumped into the drains using a compressor. Less costly, but also less productive are anaerobic bacteria that do not use oxygen.

To raise the degree of biological filtration, the processed effluents are subjected to post-treatment. In most cases, multilayer sand filters or so-called contact clarifiers are used for this. In rare cases, microfilters are used.

If the effluent contains substances that are difficult to oxidize, they can be filtered using activated carbon or another sorbent, or chemical oxidation can be resorted to, for example, using ozone.

During biological purification, water gets rid of toxic substances, but is saturated with phosphorus and ammonium nitrogen.

If such water is dumped into a natural reservoir, these elements will provoke a “population explosion” among algae (phosphorus in an amount of 1 mg provides the appearance of 115 mg of biomass), which is undesirable for the reservoir ecosystem.

Biological water treatment at the enterprise

Two methods are used to remove nitrogen:

Physical and chemical: water is subjected to liming, due to which its pH increases to 10 - 11 units. The resulting ammonia is removed in cooling towers by means of air stripping.
Biological.

The biological method is carried out in stages:

First, with the help of special bacteria in the aeration tank, nitrification of purified water occurs.
Next, the liquid enters a hermetically sealed container - a denitrifier, where bacteria that are without access to air destroy the molecules of nitrites and nitrates (molecular nitrogen is released) by splitting off the oxygen necessary for life.

To remove phosphorus, lime, as well as aluminum or iron salts, are added to the water. Phosphorus reacts to form precipitated compounds.

Physical and chemical cleaning methods

Coagulation: special reagents are added to the effluents - the so-called coagulants and flocculants. Their action is accompanied by various effects: soluble pollutants can turn into insoluble flakes, which are removed by straining; dangerous components break down into safe ones; the reaction of the waste mass changes, for example, from acidic to neutral.
Ion exchange method: most often used to soften water. The essence of the method is to replace "undesirable" ions (in the case of softening - magnesium and calcium) "harmless", for example, sodium.
Flotation: wastewater treatment method is aimed at separating oil products. Air is supplied to the waste mass, forming many bubbles. Particles of petroleum products tend to stick to such bubbles, as a result of which they appear on the surface in the form of foam. It can be removed by means of special scrapers or by raising the water level - while the foam itself will drain into the receiving tray.

The process of physical and chemical water treatment

If the pollutants do not have sufficient "stickiness", it is stimulated by the introduction of special reagents.

There are several types of flotation: pressure, mechanical, biological, foam, pneumatic.

In addition to these methods, reverse osmosis, evaporation, extraction, and much more are used as part of physical and chemical purification.

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Mechanical and physical methods

Mechanically get rid of insoluble inclusions. In most cases, this stage is preliminary and is used in combination with other types of treatment. This methodology includes three stages.

settling

Also often referred to as gravity cleaning. During settling, impurities with a density greater than that of water collect at the bottom, and light ones float. The latter include many impurities that are typical for industrial wastewater: oils (a sump is called an oil trap), fats (grease traps), oil (oil traps) and resins (resin traps). Previously, separate grease traps were also used to treat domestic wastewater, but today their function is assigned to special devices that are equipped with sedimentation tanks.

To remove sand and other suspensions of a mineral nature, a special type of settling tanks is used - sand traps. They can be tubular, static and dynamic.

Gravity settler

Due to the peculiarities of the technology, only 80% of the impurities amenable to such treatment can be isolated by the gravitational cleaning method. On average, this amount is only 60% of the total volume of undissolved impurities. To make settling more efficient, methods such as clarification with a weighted filter, biocoagulation and preareration (sometimes with or without excess sludge) are used.

containing a large number of eggs of helminths and pathogenic bacteria, the sediment is subjected to post-treatment with the help of anaerobic microorganisms in septic tanks and digesters.

Straining

To screen out large suspended particles (the density is almost equal to the density of water), the effluents are filtered through gratings and sieves installed in their path.

Filtration

The method is similar to straining, but is aimed at removing impurities of smaller fractions.

Instead of sieves, fabric, porous or fine-grained filters are used.

There are special devices - micro-strainers, which are a drum equipped with a mesh. Screened impurities are washed off into the catch hopper with a stream of water spouting from special nozzles.

What is included in the complex of works for the disposal of wastewater

Wastewater disposal includes the following areas:

collection of industrial and domestic wastewater, as well as rainwater;
cleaning of cesspools and septic tanks;
maintenance of toilets with chemical sterilization;
maintenance of sewerage networks;
collection of sludge from sewage treatment plants.

The complex of works also includes transportation and neutralization of wastewater.

The purpose of domestic wastewater treatment should be to use it in agriculture, reuse of detergents, production of methane from organic components. In the agro-industrial complex, prepared effluents can be used for watering plants, creating mixtures for hydroponics, and in fish farming.

Who benefits from our services

Wastewater disposal services are necessary for both legal entities and individuals. The processing of the sludge that remains after the treatment of discharges is needed by the treatment facilities of heavy and light industries, car washes. We are also needed by the city utilities and the private housing sector, which does not have a central sewerage system.

How is the processing of sewage treatment plant sludge

Wastewater treatment of large enterprises is organized at the place of production. The scope of our services includes the transportation and disposal of sludge that accumulates during the treatment of wastewater. It consists of heavy metals, surfactants and petroleum products that are harmful to the environment. Therefore, much attention is paid to the processing of the settled layer.

Waste disposal is carried out according to the following technologies:

deposition (evaporation) on sludge sites;
composting for later use as fertilizer;
burning;
pyrolysis.

The most efficient and environmentally friendly processing technology is pyrolysis. It consists in the thermal decomposition of organic substances without access to oxygen. From the inorganic component, pure slag (metal oxides) is obtained, which is used as a mineral filler for cement, filling dumps in road construction, and landscape planning. It is also used in the production of vibropressed paving slabs.

The question of which technology will be used for the disposal of sewage sludge is decided for each enterprise individually. It depends on local conditions and composition of the mass.

To receive the sludge, sewage silt-sucking machines are used. Pumping out and transportation of the contents of the drain pits is carried out by sewer-flushing and combined equipment equipped with vacuum pumps.

Our advantages

"EcoPromtech-South" is a specialized company licensed to carry out work on the disposal of wastewater. We employ highly qualified specialists who have valuable knowledge and skills in the field of technological processes of processing. Thanks to a large fleet of special equipment, we can cope with tasks of any complexity. Our customers receive all the documents necessary for reporting to the supervisory authorities. We work on a contractual basis, we guarantee compliance with the terms of waste removal, environmental friendliness of the process.

Call the company "EcoPromtech-South", and wastewater disposal of your organization will be carried out using the most economical and efficient technology.

- This is a complex of special facilities designed to treat wastewater from the contaminants contained in them. Purified water is either used in the future, or discharged into natural reservoirs (Great Soviet Encyclopedia).

Each settlement needs effective treatment facilities. The operation of these complexes determines what water will enter the environment and how it will affect the ecosystem in the future. If liquid waste is not treated at all, then not only plants and animals will die, but the soil will also be poisoned, and harmful bacteria can enter the human body and cause serious consequences.

Each enterprise that has toxic liquid waste is obliged to deal with a system of treatment facilities. Thus, it will affect the state of nature, and improve the conditions of human life. If the treatment complexes work effectively, then the wastewater will become harmless when it enters the ground and water bodies. The size of treatment facilities (hereinafter referred to as O.S.) and the complexity of treatment are highly dependent on the contamination of wastewater and their volumes. In more detail about the stages of wastewater treatment and types of O.S. read on.

Stages of wastewater treatment

The most indicative in terms of the presence of stages of water purification are urban or local OS, designed for large settlements. It is domestic wastewater that is the most difficult to clean, as it contains heterogeneous pollutants.

For facilities for the purification of water from sewerage, it is characteristic that they line up in a certain sequence. Such a complex is called a line of treatment facilities. The scheme begins with mechanical cleaning. Here gratings and sand traps are most often used. This is the initial stage of the entire water treatment process.

It can be the remains of paper, rags, cotton wool, bags and other debris. After gratings, sand traps come into operation. They are necessary in order to retain sand, including large sizes.

Mechanical Stage Wastewater Treatment

Initially, all water from the sewer goes to the main pumping station in a special tank. This tank is designed to compensate for the increased load during peak hours. A powerful pump evenly pumps the appropriate volume of water to pass through all stages of cleaning.

catch large debris over 16 mm - cans, bottles, rags, bags, food, plastic, etc. In the future, this garbage is either processed on site, or taken out to the places of processing of solid household and industrial waste. Lattices are a type of transverse metal beams, the distance between which is equal to several centimeters.

In fact, they catch not only sand, but also small pebbles, glass fragments, slag, etc. Sand rather quickly settles to the bottom under the influence of gravity. Then the settled particles are raked by a special device into a recess at the bottom, from where it is pumped out by a pump. The sand is washed and disposed of.

. Here all impurities that float to the surface of the water (fats, oils, oil products, etc.) are removed, etc. By analogy with a sand trap, they are also removed with a special scraper, only from the surface of the water.

4. Sumps- an important element of any line of treatment facilities. They release water from suspended solids, including helminth eggs. They can be vertical and horizontal, single-tier and two-tier. The latter are the most optimal, since at the same time the water from the sewer in the first tier is cleaned, and the sediment (silt) that has formed there is discharged through a special hole into the lower tier. How does the process of releasing water from the sewer from suspended solids take place in such structures? The mechanism is quite simple. Sedimentation tanks are large round or rectangular tanks where substances settle under the action of gravity.

To speed up this process, you can use special additives - coagulants or flocculants. They contribute to the adhesion of small particles due to a change in charge, larger substances are deposited faster. Thus, sedimentation tanks are indispensable facilities for purifying water from sewers. It is important to consider that with simple water treatment they are also actively used. The principle of operation is based on the fact that water enters from one end of the device, while the diameter of the pipe at the exit becomes larger and the fluid flow slows down. All this contributes to the deposition of particles.

mechanical wastewater treatment can be used depending on the degree of water pollution and the design of a particular treatment plant. These include: membranes, filters, septic tanks, etc.

If we compare this stage with conventional water treatment for drinking purposes, then in the latter version such facilities are not used, they are not necessary. Instead, the processes of clarification and discoloration of water occur. Mechanical cleaning is very important, as in the future it will allow more efficient biological cleaning.

Biological wastewater treatment plants

Biological treatment can be both an independent treatment facility and an important stage in a multi-stage system of large urban treatment facilities.

The essence of biological treatment is to remove various pollutants (organics, nitrogen, phosphorus, etc.) from water with the help of special microorganisms (bacteria and protozoa). These microorganisms feed on harmful contaminants contained in the water, thereby purifying it.

From a technical point of view, biological treatment is carried out in several stages:

- a rectangular tank where water after mechanical cleaning is mixed with activated sludge (special microorganisms), which cleans it. Microorganisms are of 2 types:

Aerobic using oxygen to purify water. When using these microorganisms, the water must be enriched with oxygen before it enters the aerotank.
Anaerobic– NOT using oxygen for water treatment.

It is necessary to remove unpleasantly smelling air with its subsequent purification. This workshop is necessary when the volume of wastewater is large enough and / or treatment facilities are located near settlements.

Here, water is purified from activated sludge by settling it. Microorganisms settle to the bottom, where they are transported to the pit with the help of a bottom scraper. To remove floating sludge, a surface scraper mechanism is provided.

The treatment scheme also includes sludge digestion. Of the treatment facilities, the methane tank is important. It is a tank for the digestion of sediment, which is formed during settling in two-tiered primary clarifiers. During the digestion process, methane is produced, which can be used in other technological operations. The resulting sludge is collected and transported to special sites for thorough drying. Sludge beds and vacuum filters are widely used for sludge dehydration. After that, it can be disposed of or used for other needs. Fermentation occurs under the influence of active bacteria, algae, oxygen. Biofilters may also be included in the sewerage water treatment scheme.

It is best to place them before the secondary settling tanks, so that substances that have been carried away with the flow of water from the filters can be deposited in the settling tanks. It is advisable to use so-called pre-aerators to speed up cleaning. These are devices that contribute to the saturation of water with oxygen to accelerate the aerobic processes of oxidation of substances and biological treatment. It should be noted that the purification of water from the sewerage is conditionally divided into 2 stages: preliminary and final.

The system of treatment facilities may include biofilters instead of filtration and irrigation fields.

- These are devices where wastewater is purified by passing through a filter containing active bacteria. It consists of solid substances, which can be used as granite chips, polyurethane foam, polystyrene and other substances. A biological film consisting of microorganisms forms on the surface of these particles. They decompose organic matter. Biofilters need to be cleaned periodically as they get dirty.

Wastewater is fed into the filter in a dosed manner, otherwise a large pressure can kill beneficial bacteria. After biofilters, secondary clarifiers are used. The sludge formed in them enters partly into the aerotank, and the rest of it goes to the sludge thickeners. The choice of one or another method of biological treatment and the type of treatment facilities largely depends on the required degree of wastewater treatment, topography, soil type and economic indicators.

Post-treatment of wastewater

After passing the main stages of treatment, 90-95% of all contaminants are removed from wastewater. But the remaining pollutants, as well as residual microorganisms and their metabolic products, do not allow this water to be discharged into natural reservoirs. In this regard, various systems for post-treatment of wastewater were introduced at treatment facilities.

In bioreactors, the following pollutants are oxidized:

organic compounds that were "too tough" for microorganisms,
these microorganisms themselves
ammonium nitrogen.

This happens by creating conditions for the development of autotrophic microorganisms, i.e. converting inorganic compounds into organic ones. For this, special plastic charging disks with a high specific surface area are used. Simply put, these discs have a hole in the center. Intensive aeration is used to speed up the processes in the bioreactor.

Filters purify water with sand. The sand is continuously updated automatically. Filtration is carried out at several installations by supplying water to them from the bottom up. In order not to use pumps and not to waste electricity, these filters are installed at a level lower than other systems. Filter washing is designed in such a way that it does not require a large amount of water. Therefore, they do not occupy such a large area.

Disinfection of water with ultraviolet light

Disinfection or disinfection of water is an important component that ensures its safety for the reservoir into which it will be discharged. Disinfection, that is, the destruction of microorganisms, is the final step in the purification of sewage effluents. A wide variety of methods can be used for disinfection: ultraviolet irradiation, alternating current, ultrasound, gamma irradiation, chlorination.

UFO - very effective method, with the help of which approximately 99% of all microorganisms are destroyed, including bacteria, viruses, protozoa, helminth eggs. It is based on the ability to destroy the bacterial membrane. But this method is not widely used. In addition, its effectiveness depends on the turbidity of the water, the content of suspended solids in it. And UVI lamps are quickly covered with a coating of mineral and biological substances. To prevent this, special emitters of ultrasonic waves are provided.

The most commonly used method of chlorination after sewage treatment plants. Chlorination can be different: double, superchlorination, with preammonization. The latter is necessary to prevent an unpleasant odor. Superchlorination involves exposure to very large doses of chlorine. Dual action is that chlorination is carried out in 2 stages. This is more typical for water treatment. The method of chlorinating water from the sewer is very effective, in addition, chlorine has an aftereffect that other cleaning methods cannot boast of. After disinfection, the waste is discharged into a reservoir.

Phosphate removal

Phosphates are salts of phosphoric acids. They are widely used in synthetic detergents(washing powders, dishwashing detergents, etc.). Phosphates, getting into water bodies, lead to their eutrophication, i.e. turning into a swamp.

Wastewater treatment from phosphates is carried out by dosed addition of special coagulants to water in front of biological treatment facilities and in front of sand filters.

Auxiliary premises of treatment facilities

Aeration shop

- this is an active process of saturating water with air, in this case by passing air bubbles through the water. Aeration is used in many processes in wastewater treatment plants. Air is supplied by one or more blowers with frequency converters. Special oxygen sensors regulate the amount of air supplied so that its content in the water is optimal.

Disposal of excess activated sludge (microorganisms)

At the biological stage of wastewater treatment, excess sludge is formed, since microorganisms actively multiply in the aeration tanks. Excess sludge is dehydrated and disposed of.

The dehydration process takes place in several stages:

In excess sludge is added special reagents, which stop the activity of microorganisms and contribute to their thickening
V sludge thickener the sludge is compacted and partially dehydrated.
On the centrifuge the sludge is squeezed out and the remaining moisture is removed from it.
Inline dryers with the help of continuous circulation of warm air, the sludge is finally dried. The dried sludge has a residual moisture content of 20-30%.
Then ooze packed in sealed containers and disposed of
The water removed from the sludge is sent back to the beginning of the purification cycle.

Air cleaning

Unfortunately, the sewage treatment plant does not smell the best. Particularly smelly is the stage of biological wastewater treatment. Therefore, if the treatment plant is located near settlements or the volume of wastewater is so large that there is a lot of bad-smelling air, you need to think about cleaning not only water, but also air.

Air purification, as a rule, takes place in 2 stages:

Initially, polluted air is fed into bioreactors, where it comes into contact with specialized microflora adapted for the utilization of organic substances contained in the air. It is these organic substances that cause the bad smell.
The air goes through the stage of disinfection with ultraviolet light to prevent these microorganisms from entering the atmosphere.

Laboratory at the wastewater treatment plant

All water that leaves the treatment plant must be systematically monitored in the laboratory. The laboratory determines the presence of harmful impurities in the water and the compliance of their concentration with the established standards. In case of exceeding one or another indicator, the workers of the treatment plant conduct a thorough inspection of the corresponding stage of treatment. And if a problem is found, they fix it.

Administrative and amenity complex

The personnel serving the treatment plant can reach several tens of people. For their comfortable work, an administrative and amenity complex is being created, it includes:

Equipment repair shops
Laboratory
control room
Offices of administrative and managerial personnel (accounting, personnel service, engineering, etc.)
Head office.

Power supply O.S. performed according to the first category of reliability. Since the long stoppage of O.S. due to lack of electricity can cause the output of O.S. out of service.

To prevent emergency situations, the power supply of O.S. comes from several independent sources. In the department of the transformer substation, the input of a power cable from the city power supply system is provided. As well as the input of an independent source of electric current, for example, from a diesel generator, in case of an accident in the city power grid.

Conclusion

Based on the foregoing, it can be concluded that the scheme of treatment facilities is very complex and includes various stages of wastewater treatment from sewers. First of all, you need to know that this scheme applies only to domestic wastewater. If there are industrial effluents, then in this case they additionally include special methods that will be aimed at reducing the concentration of hazardous chemicals. In our case, the cleaning scheme includes the following main stages: mechanical, biological cleaning and disinfection (disinfection).

Mechanical cleaning begins with the use of gratings and sand traps, in which large debris (rags, paper, cotton wool) is retained. Sand traps are needed to settle excess sand, especially coarse sand. It has great importance for the next steps. After gratings and grit traps, the sewerage treatment plant scheme includes the use of primary clarifiers. Suspended matter settles in them under the force of gravity. Coagulants are often used to speed up this process.

After the settling tanks, the filtration process begins, which is carried out mainly in biofilters. The mechanism of action of the biofilter is based on the action of bacteria that destroy organic matter.

The next stage is secondary settling tanks. In them, the silt, which was carried away with the current of the liquid, settles. After them, it is advisable to use a digester, in which the sediment is fermented and transported to sludge sites.

The next stage is biological treatment with the help of an aeration tank, filtration fields or irrigation fields. The final step is disinfection.

Types of treatment facilities

A variety of facilities are used for water treatment. If it is planned to carry out these works in relation to surface waters immediately before they are supplied to the distribution network of the city, then the following facilities are used: sedimentation tanks, filters. For wastewater, a wider range of devices can be used: septic tanks, aeration tanks, digesters, biological ponds, irrigation fields, filtration fields, and so on. Wastewater treatment plant There are several types depending on their purpose. They differ not only in the volume of treated water, but also in the presence of stages of its purification.

City wastewater treatment plant

Data from O.S. are the largest of all, they are used in large metropolitan areas and cities. In such systems, especially effective methods liquid treatment, such as chemical treatment, methane tanks, flotation plants They are designed for the treatment of municipal wastewater. These waters are a mixture of domestic and industrial wastewater. Therefore, there are a lot of pollutants in them, and they are very diverse. The waters are purified to the standards for discharge into a fishery reservoir. The standards are regulated by the order of the Ministry of Agriculture of Russia dated December 13, 2016 No. 552 “On approval of water quality standards for fishery water bodies, including standards for maximum permissible concentrations of harmful substances in the waters of fishery water bodies”.

On O.S. data, as a rule, all stages of water purification described above are used. The most illustrative example is the Kuryanovsk treatment facilities.

Kuryanovskie O.S. are the largest in Europe. Its capacity is 2.2 million m3/day. They serve 60% of wastewater in the city of Moscow. The history of these objects goes back to the distant 1939.

Local treatment facilities

Local treatment facilities are facilities and devices designed to treat the subscriber's wastewater before they are discharged into the public sewerage system (the definition is given by Decree of the Government of the Russian Federation of February 12, 1999 No. 167).

There are several classifications of local O.S., for example, there are local O.S. connected to the central sewerage and autonomous. Local O.S. can be used on the following objects:

In small towns
In the settlements
In sanatoriums and boarding houses
At car washes
On household plots
At manufacturing plants
And on other objects.

Local O.S. can be very different from small units to permanent structures that are serviced daily by qualified personnel.

Treatment facilities for a private house.

Several solutions are used for the disposal of wastewater from a private house. All of them have their advantages and disadvantages. However, the choice always remains with the owner of the house.

1. Cesspool. In truth, this is not even a treatment plant, but simply a reservoir for temporary storage of wastewater. When the pit is filled, a sewage truck is called in, which pumps out the contents and transports them for further processing.

This archaic technology is still used today because of its cheapness and simplicity. However, it also has significant drawbacks, which, at times, nullify all its advantages. Wastewater can enter the environment and groundwater, thereby polluting them. For a sewage truck, it is necessary to provide for a normal entrance, since it will have to be called quite often.

2. Drive. It is a container made of plastic, fiberglass, metal or concrete, where wastewater is drained and stored. Then they are pumped out and disposed of by a sewage machine. The technology is similar to a cesspool, but the waters do not pollute the environment. The disadvantage of such a system is the fact that in the spring, with a large amount of water in the soil, the drive can be squeezed out to the surface of the earth.

3. Septic tank- is a large container, in which substances such as coarse dirt, organic compounds, stones and sand precipitate, and elements such as various oils, fats and petroleum products remain on the surface of the liquid. Bacteria that live inside the septic tank extract oxygen for life from the precipitated sludge, while reducing the level of nitrogen in the wastewater. When the liquid leaves the sump, it becomes clarified. Then it is cleaned with bacteria. However, it is important to understand that phosphorus remains in such water. For the final biological treatment, irrigation fields, filtration fields or filter wells can be used, the operation of which is also based on the action of bacteria and activated sludge. It will not be possible to grow plants with a deep root system in this area.

A septic tank is very expensive and can take up a large area. It should be borne in mind that this is a facility that is designed to treat a small amount of domestic wastewater from the sewer. However, the result is worth the money spent. The septic tank device is more clearly shown in the figure below.

4. Stations for deep biological treatment are already a more serious treatment plant, unlike a septic tank. This device requires electricity to operate. However, the quality of water purification is up to 98%. The design is quite compact and durable (up to 50 years of operation). To service the station at the top, above the ground, there is a special hatch.

Stormwater treatment plants

Despite the fact that rainwater is considered quite clean, however, it collects various harmful elements from asphalt, roofs and lawns. Garbage, sand and oil products. In order to prevent all this from falling into the nearest reservoirs, stormwater treatment facilities are being created.

In them, water undergoes mechanical purification in several stages:

Sump. Here, under the influence of the gravity of the Earth, large particles settle to the bottom - pebbles, glass fragments, metal parts, etc.
thin layer module. Here, oils and oil products are collected on the surface of the water, where they are collected on special hydrophobic plates.
Sorption fibrous filter. It captures everything that the thin layer filter missed.
coalescent module. It contributes to the separation of particles of oil products that float to the surface, the size of which is greater than 0.2 mm.
Coal filter aftertreatment. It finally rids the water of all oil products that remain in it after passing through the previous stages of purification.

Design of treatment facilities

Design O.S. determine their cost, choose the right treatment technology, ensure the reliability of the structure, bring wastewater to quality standards. Experienced specialists will help you find effective plants and reagents, draw up a wastewater treatment scheme and put the plant into operation. Another important point is the preparation of a budget that will allow you to plan and control costs, as well as make adjustments if necessary.

For the project O.S. The following factors are strongly influenced:

Waste water volumes. The design of facilities for a personal plot is one thing, but the design of facilities for wastewater treatment of a cottage village is another. Moreover, it must be taken into account that the possibilities of O.S. must be greater than the current amount of wastewater.
Locality. Wastewater treatment facilities require the access of special vehicles. It is also necessary to provide for the power supply of the facility, the disposal of purified water, the location of the sewerage system. O.S. can occupy a large area, but they should not interfere with neighboring buildings, structures, road sections and other structures.
Waste water pollution. Storm water treatment technology is very different from household water treatment.
Required level of cleaning. If the customer wants to save on the quality of treated water, then it is necessary to use simple technologies. However, if it is necessary to discharge water into natural reservoirs, then the quality of treatment must be appropriate.
Competence of the performer. If you order O.S. from inexperienced companies, then get ready for unpleasant surprises in the form of an increase in construction estimates or a septic tank that floated up in the spring. This happens because the project forgets to include enough critical points.
Technological features. The technologies used, the presence or absence of treatment stages, the need to build systems serving the treatment plant - all this should be reflected in the project.
Other. It is impossible to foresee everything in advance. As the treatment plant is being designed and installed, various changes may be made to the draft plan that could not have been foreseen at the initial stage.

Stages of designing a treatment plant:

Preliminary work. They include studying the object, clarifying the wishes of the customer, analyzing wastewater, etc.
Collection of permits. This item is usually relevant for the construction of large and complex structures. For their construction, it is necessary to obtain and agree on the relevant documentation from supervisory authorities: MOBVU, MOSRYBVOD, Rosprirodnadzor, SES, Hydromet, etc.
Choice of technology. Based on paragraphs 1 and 2, the necessary technologies used for water purification are selected.
Drawing up a budget. Construction costs O.S. must be transparent. The customer must know exactly how much the materials cost, what is the price of the installed equipment, what wage fund for workers, etc. You should also take into account the cost of subsequent maintenance of the system.
cleaning efficiency. Despite all calculations, the cleaning results may be far from desired. Therefore, already at the planning stage, O.S. it is necessary to conduct experiments and laboratory studies that will help to avoid unpleasant surprises after construction is completed.
Development and approval of project documentation. To start the construction of treatment facilities, it is necessary to develop and agree on the following documents: a project for a sanitary protection zone, a draft standard for permissible discharges, and a draft for maximum permissible emissions.

Installation of treatment facilities

After the project O.S. has been prepared and all the necessary permits have been obtained, the installation stage begins. Although the installation of a country septic tank is very different from the construction of a treatment plant in a cottage village, they still go through several stages.

First, the terrain is being prepared. A pit is being dug for the installation of a treatment plant. The floor of the pit is covered with sand and tamped or concreted. If the treatment plant is designed for a large amount of wastewater, then, as a rule, it is built on the surface of the earth. In this case, the foundation is poured and a building or structure is already installed on it.

Secondly, the installation of equipment is carried out. It is installed, connected to the sewerage and drainage system, to electrical network. This stage is very important because it requires the personnel to know the specifics of the operation of the configured equipment. It is improper installation that most often causes equipment failure.

Thirdly, checking and handing over the object. After installation, the finished treatment plant is tested for the quality of water treatment, as well as for the ability to work in conditions of increased load. After checking O.S. is handed over to the customer or his representative, and, if necessary, passes the procedure of state control.

Maintenance of treatment facilities

Like any equipment, a sewage treatment plant also needs maintenance. First of all from O.S. it is necessary to remove large debris, sand, as well as excess sludge that are formed during cleaning. On large O.S. the number and type of elements to be removed can be much larger. But in any case, they will have to be removed.

Secondly, the performance of the equipment is checked. Malfunctions in any element can be fraught not only with a decrease in the quality of water purification, but also with the failure of all equipment.

Thirdly, in case of detection of a breakdown, the equipment is subject to repair. And it's good if the equipment is under warranty. If the warranty period has expired, then the repair of O.S. will have to be done at your own expense.