Sewage treatment plants: what is wastewater treatment? Design of sludge beds Digested sludge onto sludge beds

is a complex of special structures designed for cleaning waste water from the contaminants they contain. Purified water is either used further or discharged into natural bodies of water(Great Soviet Encyclopedia).

Every settlement needs effective wastewater treatment facilities. The operation of these complexes determines what kind of water will enter the environment and how this will further affect the ecosystem. If liquid waste is not cleaned up at all, not only will plants and animals die, but the soil will also be poisoned, and harmful bacteria can enter the human body and cause serious consequences.

Every enterprise that has toxic liquid waste is required to operate a treatment plant system. Thus, this will affect the state of nature and improve human living conditions. If treatment systems work effectively, wastewater will become harmless when it enters the ground and water bodies. The size of treatment facilities (hereinafter - OS) and the complexity of treatment strongly depend on the contamination of wastewater and its volume. More details 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 water purification stages are urban or local OS, designed for large populated areas. It is household wastewater that is most difficult to treat, as it contains various pollutants.

It is typical for sewerage water treatment facilities that they are built in a certain sequence. Such a complex is called a treatment plant line. The diagram starts with mechanical cleaning. Grates and sand traps are most often used here. This initial stage the entire water treatment process.

This could be leftover paper, rags, cotton wool, bags and other debris. After the grates, sand traps come into operation. They are necessary in order to retain sand, including large sizes.

Mechanical stage of wastewater treatment

Initially, all water from the sewer goes to the main pumping station into a special tank. This reservoir 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 larger than 16 mm - cans, bottles, rags, bags, food, plastic, etc. Subsequently, this waste is either processed on site or transported to places for processing solid household and industrial waste. Grids are a type of transverse metal beams, the distance between which is several centimeters.

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

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

4. Settling tanks– an important element of any treatment plant line. In them, water is freed from suspended substances, including helminth eggs. They can be vertical and horizontal, single-tier and two-tier. The latter are the most optimal, since in this case the water from the sewer in the first tier is purified, and the sediment (silt) that has formed there is discharged through a special hole into the lower tier. How does the process of releasing suspended solids from sewer water take place in such structures? The mechanism is quite simple. Sedimentation tanks are reservoirs large sizes round or rectangular shape, where sedimentation of substances occurs under the influence of gravity.

To speed up this process, you can use special additives - coagulants or flocculants. They promote the sticking together of small particles due to a change in charge; larger substances settle faster. Thus, sedimentation tanks are indispensable structures for purifying water from sewers. It is important to take into account that they are also actively used in simple water treatment. 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 flow of liquid slows down. All this contributes to the sedimentation of particles.

Mechanical wastewater treatment can be used depending on the degree of water contamination and the design of a specific treatment facility. 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 structures are not used and there is no need for them. Instead, processes of water clarification and discoloration occur. Mechanical cleaning is very important, since in the future it will allow for more effective biological treatment.

Biological wastewater treatment plants

Biological treatment can be either an independent treatment facility or important stage in a multi-stage system of large urban treatment complexes.

The essence of biological treatment is to remove various pollutants (organics, nitrogen, phosphorus, etc.) from water using 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 purification, is mixed with activated sludge (special microorganisms), which purifies it. There are 2 types of microorganisms:

Aerobic– using oxygen to purify water. When using these microorganisms, the water must be enriched with oxygen before entering the aeration tank.
Anaerobic– DO NOT use oxygen to purify water.

Necessary for removing 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 nearby settlements.

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

The purification scheme also includes sludge digestion. Of the treatment facilities, the digester is important. It is a reservoir for the fermentation of sludge, which is formed during settling in two-tier primary settling tanks. The fermentation process produces methane, which can be used in other technological operations. The resulting sludge is collected and transported to special sites for thorough drying. Found for sludge dewatering wide application sludge beds and vacuum filters. After this, it can be disposed of or used for other needs. Fermentation occurs under the influence of active bacteria, algae, and oxygen. The sewer water purification scheme may also include biofilters.

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

The treatment plant system 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 solids, which can be granite chips, polyurethane foam, polystyrene foam and other substances. A biological film consisting of microorganisms forms on the surface of these particles. They decompose organic matter. As biofilters become dirty, they need to be cleaned periodically.

Wastewater is fed into the filter in doses, otherwise high pressure can destroy beneficial bacteria. After biofilters, secondary settling tanks are used. The sludge formed in them goes partly into the aeration tank, and the rest of it goes to the sludge compactors. The choice of one or another biological treatment method and type of treatment facility largely depends on the required degree of wastewater treatment, topography, soil type and economic indicators.

Wastewater tertiary treatment

After passing through 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, the treatment plants introduced various systems wastewater tertiary treatment.

In bioreactors the process of oxidation of the following pollutants occurs:

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 purpose, special plastic backfill disks with a high specific surface area are used. Simply put, these are disks with a hole in the center. To speed up processes in the bioreactor, intensive aeration is used.

Filters purify water using sand. The sand is continuously renewed in automatic mode. Filtration is carried out in several installations by supplying water to them from the bottom up. In order to avoid using pumps and not wasting 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. That's why they don't occupy the same amount large area.

Ultraviolet water disinfection

Disinfection or disinfection of water is an important component that ensures its safety for the body of water into which it will be discharged. Disinfection, that is, the destruction of microorganisms, is the final stage of sewerage wastewater treatment. For disinfection, the most various ways: ultraviolet irradiation, alternating current, ultrasound, gamma irradiation, chlorination.

UFO - very effective way, with the help of which approximately 99% of all microorganisms are destroyed, including bacteria, viruses, protozoa, and helminth eggs. It is based on the ability to destroy the membrane of bacteria. But this method is not used so widely. In addition, its effectiveness depends on the turbidity of the water and the content of suspended substances in it. And UV 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 after treatment facilities is chlorination. Chlorination can be different: double, superchlorination, with preammonization. The latter is necessary for warning unpleasant odor. Superchlorination involves exposure to very large doses of chlorine. Double action is that chlorination is carried out in 2 stages. This is more typical for water treatment. The method of chlorinating sewer water is very effective, in addition, chlorine has an aftereffect that other cleaning methods cannot boast of. After disinfection, the wastewater 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 entering water bodies lead to their eutrophication, i.e. turning into a swamp.

Purification of wastewater from phosphates is carried out by dosed addition of special coagulants to the water before biological treatment facilities and before sand filters.

Auxiliary premises of treatment facilities

Aeration shop

- this is an active process of saturation of water with air, in in this case by passing air bubbles through water. Aeration is used in many processes in wastewater treatment plants. Air supply is carried out 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, as microorganisms actively multiply in aeration tanks. Excess sludge is dewatered and disposed of.

The dehydration process takes place in several stages:

Added to excess sludge special reagents, which suspend the activity of microorganisms and promote their thickening
IN sludge compactor the sludge is compacted and partially dewatered.
On centrifuge the sludge is squeezed out and any remaining moisture is removed from it.
In-line dryers through continuous circulation warm air finally dry the sludge. The dried sludge has a residual moisture content of 20-30%.
Then packed into sealed containers and disposed of
The water removed from the sludge is sent back to the beginning of the cleaning cycle.

Air purification

Unfortunately, the wastewater treatment plants don't smell the best. in the best possible way. The biological wastewater treatment stage is especially smelly. Therefore, if the treatment plant is located near populated areas or the volume of wastewater is so large that a lot of bad-smelling air is generated, you need to think about cleaning not only the water, but also the air.

Air purification usually takes place in 2 stages:

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

Laboratory at wastewater treatment plants

All water that leaves treatment plants must be systematically monitored in the laboratory. The laboratory determines the presence in water harmful impurities and compliance with their concentration established standards. If one or another indicator is exceeded, workers at the treatment plant carry out thorough examination appropriate cleaning step. And if a malfunction is detected, it is eliminated.

Administrative and amenity complex

The personnel servicing the treatment plant can reach several dozen people. For their comfortable work, an administrative and amenity complex is being created, which includes:

Equipment repair workshops
Laboratory
Control room
Offices of administrative and management personnel (accounting, personnel service, engineering, etc.)
Manager's office.

Power supply O.S. performed according to the first reliability category. Since a long shutdown of O.S. due to lack of electricity may cause O.S. output. out of order.

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

Conclusion

Based on all of the above, we can conclude that the design of treatment facilities is very complex and includes various stages of treating wastewater from sewers. First of all, you need to know that this scheme Applicable only to domestic wastewater. If industrial effluents occur, then in this case special methods are additionally included 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 grates and sand traps, which trap large debris (rags, paper, cotton wool). Sand traps are needed to sediment excess sand, especially coarse sand. It has great value for subsequent stages. After screens and sand traps, the sewer water treatment plant scheme includes the use of primary settling tanks. Suspended substances settle in them under the force of gravity. To speed up this process, coagulants are often used.

After 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 substances.

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

The next stage is biological treatment using an aeration tank, filtration fields or irrigation fields. The final stage is disinfection.

Types of treatment facilities

A variety of structures are used for water treatment. If you plan to carry out this work in relation to surface waters immediately before they are supplied to the city distribution network, then apply the following structures: settling 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. There are several types of treatment plants depending on their purpose. They differ not only in the volume of water being purified, but also in the presence of stages of its purification.

City wastewater treatment plants

Data from O.S. are the largest of all, they are used in large cities and towns. In such systems they are especially used effective methods liquid purification, for example, chemical treatment, methane tanks, flotation plants They are designed for treating 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 water is purified to meet the standards for discharge into a fishery reservoir. The standards are regulated by Order of the Ministry of Agriculture of Russia dated December 13, 2016 No. 552 “On approval of water quality standards for water bodies of fishery importance, including standards for maximum permissible concentrations harmful substances in the waters of water bodies of fishery importance.”

In OS data, as a rule, all stages of water purification described above are used. The most illustrative example is the Kuryanovsky wastewater treatment plant.

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

Local treatment facilities

Local treatment facilities are structures and devices designed to treat the subscriber's wastewater before discharging it into the public sewerage system (defined by Decree of the Government of the Russian Federation of February 12, 1999 No. 167).

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

In small towns
In the villages
In sanatoriums and boarding houses
At car washes
On personal plots
At manufacturing plants
And at other facilities.

Local O.S. can vary greatly from small units to capital structures that are maintained daily by qualified personnel.

Treatment facilities for a private home.

Several solutions are used to dispose of wastewater from a private home. They all have their advantages and disadvantages. However, the choice always remains with the home owner.

1. Cesspool. In truth, this is not even a treatment facility, but simply a tank for temporary storage of wastewater. When the pit is filled, a sewage disposal truck is called, which pumps out the contents and takes it away for further processing.

This archaic technology is still used today due to its cheapness and simplicity. However, it also has significant disadvantages, which sometimes negate all its advantages. Wastewater may enter the environment and groundwater, thereby polluting them. A normal entrance must be provided for the sewer truck, since it will have to be called quite often.

2. Storage. It is a container made of plastic, fiberglass, metal or concrete into which wastewater is drained and stored. They are then pumped out and disposed of by a sewer truck. The technology is similar cesspool, but the waters do not pollute the environment. The disadvantage of such a system is the fact that in the spring, when there is a large amount of water in the ground, the storage tank can be squeezed out to the surface of the earth.

3. Septic tank- are large containers, in which substances such as coarse dirt, organic compounds, stones and sand settle, and elements such as various oils, fats and petroleum products remain on the surface of the liquid. The bacteria that live inside the septic tank extract oxygen for life from the fallen sediment, while reducing the level of nitrogen in the wastewater. When the liquid leaves the sump, it becomes clarified. It is then purified using bacteria. However, it is important to understand that phosphorus remains in such water. For 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. Plants with a deep root system cannot be grown 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 structure that is designed to treat small amounts of domestic wastewater from the sewer system. However, the result is worth the money spent. The structure of a septic tank is shown more clearly in the figure below.

4. Deep biological treatment stations are already a more serious treatment facility, 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, there is a special hatch at the top, above the ground surface.

Stormwater treatment plants

Even though rainwater It is considered quite clean, but it collects various harmful elements from asphalt, roofs and lawns. Garbage, sand and petroleum products. To ensure that all this does not end up in nearby water bodies, stormwater treatment facilities are being created.

In them, water undergoes mechanical purification in several stages:

Sump. Here, under the influence of the Earth's gravity, large particles settle to the bottom - pebbles, glass fragments, metal parts etc.
Thin layer module. Here, oils and petroleum products collect on the surface of the water, where they are collected on special hydrophobic plates.
Sorption fiber filter. It catches everything that the thin-layer filter missed.
Coalescent module. It helps to separate oil particles that float to the surface and are larger than 0.2 mm in size.
Carbon filter after purification. It finally rids the water of all petroleum products that remain in it after passing through the previous stages of purification.

Design of wastewater treatment plants

Design of O.S. determine their value, in the right way choose a treatment technology, ensure reliable operation of the structure, and bring wastewater to quality standards. Experienced specialists will help you find effective installations and reagents, draw up a wastewater treatment plan and put the installation into operation. Another important point– drawing up an estimate that will allow you to plan and control expenses, as well as make adjustments if necessary.

For the project O.S. The following factors greatly influence:

Wastewater volumes. Design of structures for personal plot this is one thing, but the design of wastewater treatment facilities cottage village– this is different. Moreover, it must be taken into account that the capabilities of O.S. must be greater than the current amount of wastewater.
Terrain. Wastewater treatment facilities require access to special vehicles. It is also necessary to provide for the power supply of the facility, the removal of purified water, and the location of the sewage system. O.S. may occupy a large area, but they should not interfere with neighboring buildings, structures, roads and other structures.
Wastewater pollution. The technology for treating storm water is very different from treating domestic water.
Required level of cleaning. If the customer wants to save on the quality of purified water, then it is necessary to use simple technologies. However, if you need 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 prepare for unpleasant surprises in the form of an increase in construction estimates or a septic tank floating in the spring. This happens because they forget to include quite critical points in the project.
Technological features. The technologies used, the presence or absence of treatment stages, the need to construct systems servicing the treatment facility - all this must be reflected in the project.
Other. It is impossible to foresee everything in advance. As the treatment plant is designed and installed, various changes may be made to the design plan that could not be foreseen at the initial stage.

Stages of designing a treatment plant:

Preliminary work. They include studying the site, clarifying the customer’s wishes, analyzing wastewater, etc.
Collection of permits. This point is usually relevant for the construction of large and complex structures. For their construction, it is necessary to obtain and approve the relevant documentation from the supervisory authorities: MOBVU, MOSRYBVOD, Rosprirodnadzor, SES, Hydromet, etc.
Choice of technology. Based on points 1 and 2. a choice is made necessary technologies used for water purification.
Drawing up an estimate. Construction costs O.S. must be transparent. The customer must know exactly how much the materials cost, what the price of the installed equipment is, what the workers' wage fund is, etc. You should also consider the costs of subsequent system maintenance.
Cleaning efficiency. Despite all the 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 avoid unpleasant surprises after construction is completed.
Development and approval of project documentation. To begin construction of treatment facilities, it is necessary to develop and agree on the following documents: a draft sanitary protection zone, a draft standards for permissible discharges, a draft maximum permissible emissions.

Installation of treatment facilities

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

First, the area is prepared. A pit is being dug to install a treatment plant. The floor of the pit is filled with sand and compacted or concreted. If the treatment facility is designed for large number 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 personnel to know the specifics of the operation of the equipment being configured. It is incorrect installation that most often causes equipment failure.

Thirdly, inspection and delivery of the object. After installation, the finished treatment facility is tested for the quality of water treatment, as well as for its ability to operate under high load conditions. After checking O.S. is handed over to the customer or his representative, and also, if necessary, undergoes a state control procedure.

Treatment plant maintenance

Like any equipment, the treatment plant also needs maintenance. Primarily from O.S. It is necessary to remove large debris, sand, and excess silt that are formed during cleaning. On large O.S. the number and type of elements removed can be significantly greater. But in any case, they will have to be deleted.

Secondly, the functionality of the equipment is checked. Malfunctions in any element can lead not only to a decrease in the quality of water purification, but also to the failure of all equipment.

Thirdly, if a breakdown is detected, the equipment must be repaired. And it’s good if the equipment is under warranty. If the warranty period has expired, then repair O.S. you will have to do it at your own expense.

The simplest and most common way of dewatering sludge is to dry it on sludge beds with a natural foundation (with or without drainage), with surface drainage water and on compaction platforms.

The first are planned plots of land (maps), surrounded on all sides by earthen ridges (Fig. 4.60). Raw sludge from sedimentation tanks or fermented from digesters, two-tier sedimentation tanks or other structures, having a humidity of 90% (from two-tier sedimentation tanks) to 99.5% (unfermented activated sludge), is periodically poured in a small layer onto areas and dried to a humidity of 75-80% .

Moisture from the sediment partially seeps into the soil, but most of it is removed through evaporation. The volume of sediment decreases. The dried sediment takes on the structure of wet soil. It can be picked up with a shovel and loaded into trolleys and dump trucks for transportation to the place of use.

Silt pads on a natural basis without drainage are used in cases where the soil has good filtering capacity (sand, sandy loam, light loam), level groundwater is located at a depth of at least 1.5 m from the surface of the map, and seeps - / - ditch of the boundary ditch, 2 - road, 3 - drainpatch; 4- Ibruski,SupportiveSludge tray; 5 - sludge diluting tray, 6 -drainage well; 7 - prefabricated drainage pipe,S- drainage layer, 9 - drainage pipes, 10 - exit to the hag, - drainage ditch, 12 - gates, 13 - wooden shield under the drain tray;K-1. K-2 ; K-3, K-4 and K-5 -- wells

Running drainage water can be released into the ground under sanitary conditions. At a shallower depth of groundwater, it is necessary to lower its level.

If the soil is dense and poorly permeable, the sites are equipped with tubular drainage laid in ditches filled with crushed stone and gravel. The distance between drainage ditches is recommended to be 6-8 m, the initial depth of the ditch is 0.6 m with a slope of 0.003.

At small treatment plants, for ease of operation, the width of individual cards is taken to be no more than 10 m. At medium and large stations, the width of cards can be increased to 35-40 m. The sizes of cards should be assigned taking into account the placement of sediment released at a time with a layer thickness in summer 0.25-0.3 m and in winter 0.5 m.

The cards are separated from each other by protective rollers, the height of which is 0.3 m above the working level.

The sediment is distributed over the cards using pipes or wooden trays, laid mostly in the body of the separating roller with a slope of 0.01-0.03 and equipped with outlets.

Sludge areas must be promptly cleared of dried sediment. At small treatment plants, sludge is manually loaded into machines and transported to nearby collective and state farms for use as fertilizer.

Sometimes narrow-gauge tracks for trolleys are laid on the dividing rollers, on which the sediment is transported outside the area and unloaded into cars there.

IN winter time The frozen sediment is split into separate blocks by special machines, which are then transported to the collective farm fields.

At medium and large stations, scrapers and bulldozers are used to remove sediment. The waste collected in dumps is loaded into vehicles using a peat or manure loader mounted on the base of a DT-54 tractor, or a multi-bucket loader. The latter is the most economical of the mechanisms used - its productivity is up to 40 m3/h.

In areas with an average annual air temperature of 3-6° C and an average annual amount atmospheric precipitation up to 500 mm for wastewater treatment plants throughput more than 10,000 m3/day, it is recommended to arrange sludge platforms with settling and surface drainage of sludge water. In Fig. Figure 4.61 shows sludge platforms of this type, built at the Kuryanovskaya aeration station. Sludge beds with surface drainage of sludge water are designed in the form of several (4-7) independently operating cascades. Each cascade consists of four to eight cards arranged in stages. The discharge of sediment from the supply pipelines is provided onto the upper cards. As you accumulate top layer silt water (or sediment) is discharged to the underlying map through reinforced concrete bypass-wells. Settled sludge water from the bottom of the cascade is pumped into primary settling tanks treatment plant, since the content of suspended solids in it can reach 1.5-2 g/l. The volume of settled sludge water is 30-50% of the volume of dewatered sludge, the humidity of which is reduced from 97 to 94-95%. Further dehydration of the sludge occurs due to the evaporation of moisture from the surface of the sludge.

The useful area of one map is taken to be 0.25-1 hectares with a width to length ratio of 1: 2-1: 2.5.

Sludge compaction platforms were developed by the Soyuzvodoka Institute - Nalproekt together with the Department of Sewerage LISI. The sites consist of rectangular tanks with waterproof bottoms and walls. The walls are constructed from prefabricated reinforced concrete unified panels 2.4 m high, the bottom is monolithic. Working depth of the site is 2 m.

If there is not enough space to set up open sludge areas, then sometimes covered sludge areas are built like greenhouses, covering them with glazed frames. Such sites were built in Kislovodsk. According to experimental data, the annual load on them is 9-10 m3/m2 when drying sediments from digesters.

The area of sludge sites depends on the volume of sediment, the nature of the soil on which the site is constructed, climatic conditions, as well as on the structure of the sediment.

The load of sediment on sludge beds in areas with an average annual air temperature of 3-6° C inclusive and an average annual precipitation of up to 500 mm should be taken according to table. 4.36: for areas with different average annual air temperatures, appropriate climate coefficients should be entered.

Table 4.36 Load on sludge beds with natural foundation

When designing sludge beds with surface drainage of sludge water, the load is assumed to be 1 m3/m2 per year.

Sludge compaction pads are calculated based on load q, which depends on the working depth of the site and the number of unloadings per year, taken depending on the properties of the sediment and climatic conditions from 1 to 5.

The daily volume of digested sludge Wc§ discharged from two-tier settling tanks is determined taking into account the reduction in its volume due to compaction and fermentation according to the formula

^sb = ~ . (4.117)

Where Cos is the flow rate of raw sludge, determined by formula (4.101);

A is the coefficient of sludge volume reduction due to its decomposition

During fermentation, equal to 2; b - the same, due to its compaction from 95 to 90% humidity, equal to 2.

Hence the useful area of sludge beds S , m2, for sludge from two-tier sedimentation tanks with an annual sediment load K, m3 per 1 m2 of surface will be:

S = ---------- . (4.118*

The daily volume of sludge from UMet digesters without separation of sludge water does not change compared to the initial volume of sludge from settling tanks and is:

Therefore, when determining the area of sludge beds for sludge from digesters, the reduction in volume due to compaction and digestion is not taken into account, and the area turns out to be approximately 2-3 times larger than for sludge from two-tier pits.

It is necessary to check the sufficiency of the area obtained in the calculation, taking into account the freezing of sediment in winter. The duration of the period during which freezing occurs is determined by the number of days with an average daily temperature below -10 ° C. Part of the moisture (25%) is filtered and evaporates in winter. 80% of the surface of the sludge pads is allocated for freezing, and 20% is left for use during the spring thaw.

Height of frost layer /g NAm depends on climatic conditions (for middle zone USSR it is equal to 0.5-1 m):

Wtk 2

Ynam=-G7-, (4.120)

Where W is the daily volume of sediment, m3;

5 -■ useful area of sludge beds, m2;

T - freezing period, days; - part of the area allocated for winter freezing, usually equal to 0.75;

K2-coefficient, which takes into account the decrease in sediment volume due to winter filtration and evaporation, usually equal to 0.75.

The calculations used determine the working (useful) area of the sludge beds. Additional area occupied by rollers, roads, ditches, etc., is taken into account by a coefficient whose values range from 1.2 (for large stations) to 1.4 (for small stations).

The simplest and most common way of dewatering sludge is to dry it on sludge beds with a natural base (with or without drainage), with surface water drainage and on compaction pads.

The first are planned plots of land (maps), surrounded on all sides by earthen ridges (4.60). Raw sludge from sedimentation tanks or fermented from digesters, two-tier sedimentation tanks or other structures, having a humidity of 90% (from two-tier sedimentation tanks) to 99.5% (unfermented activated sludge), is periodically poured in a small layer onto areas and dried to a humidity of 75-80% .

Moisture from sediment partially seeps into the soil, but most of it is removed through evaporation. The volume of sediment decreases. The dried sediment takes on the structure of wet soil. It can be picked up with a shovel and loaded into trolleys and dump trucks for transportation to the place of use.

Silt pads on a natural foundation without drainage are used in cases where the soil has good filtering capacity (sand, sandy loam, light loam), the groundwater level is at a depth of at least 1.5 m from the surface of the map, and seeping drainage water can be released into soil according to sanitary conditions. At a shallower depth of groundwater, it is necessary to lower its level.

The cards are separated from each other by protective rollers, the height of which is 0.3 m above the working level.

Additional information on sewerage:

INSPECTION WELLS AND CONNECTING CHAMBERS

DIFFERENCE WELLS

LLC DESIGN PRESTIGE

The sediment is distributed over the cards using pipes or wooden trays, laid mostly in the body of the separating roller with a slope of 0.01-0.03 and equipped with outlets.

Sludge areas must be promptly cleared of dried sediment. At small treatment plants, sludge is manually loaded into machines and transported to nearby collective and state farms for use as fertilizer.

Sometimes narrow-gauge tracks for trolleys are laid on the dividing rollers, on which the sediment is transported outside the area and unloaded into cars there.

In winter, frozen sediment is split into separate blocks by special machines, which are then transported to collective farm fields.

In areas with an average annual air temperature of 3-6° C and an average annual precipitation of up to 500 mm, for treatment facilities with a throughput capacity of more than 10,000 m3/day, it is recommended to construct sludge platforms with settling and surface drainage of sludge water. Figure 4.61 shows sludge platforms of this type built at the Kuryanovskaya aeration station. Sludge beds with surface drainage of sludge water are designed in the form of several (4-7) independently operating cascades. Each cascade consists of four to eight cards arranged in stages. The discharge of sediment from the supply pipelines is provided onto the upper cards. As it accumulates, the upper layer of silt water (or sediment) is discharged to the underlying map through reinforced concrete bypass-wells. The settled sludge water from the lower map of the cascade is pumped into the primary settling tanks of the treatment plant, since the content of suspended solids in it can reach 1.5-2 g/l. The volume of settled sludge water is 30-50% of the volume of dewatered sludge, the humidity of which is reduced from 97 to 94-95%. Further dehydration of the sludge occurs due to the evaporation of moisture from the surface of the sludge.

The useful area of one map is taken to be 0.25-1 hectares with a width to length ratio of 1: 2-1: 2.5.

Sludge compaction pads developed by the Soyuzvodoka-nalproekt Institute together with the Department of Sewerage LISI. The sites consist of rectangular tanks with waterproof bottoms and walls. The walls are constructed from prefabricated reinforced concrete unified panels 2.4 m high, the bottom is monolithic. Working depth of the site is 2 m.

The area of sludge sites depends on the volume of sediment, the nature of the soil on which the site is located, climatic conditions, as well as the structure of the sediment.

When designing sludge beds with surface drainage of sludge water, the load is assumed to be 1 m3/m2 per year.

Sludge compaction sites are calculated according to the load q, which depends on the working depth of the site and the number of unloadings per year, taken depending on the properties of the sediment and climatic conditions from 1 to 5.

It is necessary to check the sufficiency of the area obtained in the calculation, taking into account the freezing of sediment in winter. Long lasting! The period during which freezing occurs is determined by the number of days with an average daily temperature below -10° C. Part of the moisture (25%) is filtered and evaporates in winter. 80% of the surface of the sludge pads is allocated for freezing, and 20% is left for use during the spring thaw.

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Small sewerage includes networks and structures designed for drainage and......
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Sludge beds of wastewater treatment plants are necessary for dewatering sewage sludge.
The foundation of these sites can be either with a natural foundation (with or without drainage), as well as with surface water drainage. Silt pads are planned plots of land (maps) that are surrounded on all sides by earthen ridges.

Sludge from settling tanks or digesters, the humidity of which ranges from 90 to 99.5%, is poured onto areas at certain intervals and dried to 75-80%. A small portion of the sediment seeps into the ground, but a larger percentage evaporates. For sludge beds with a natural base, no drainage is created if they are installed on soil with good filtration capacity. And for dense, low-permeability soil, tubular drainage is created, laid in ditches with crushed stone and gravel.

Treatment plants small sizes The cards have a width of 10 m, and on larger ones it increases to 35-40 m. The cards are separated from each other by protective rollers, with a height of 0.3 m above the working level. The sediment is distributed over the cards using pipes. Sludge beds are promptly cleared of sediment. At large wastewater treatment plants, sludge is removed using bulldozers and scrapers. For treatment facilities with a throughput capacity of more than 10,000 m3/day, sludge platforms are installed with settling and surface drainage of sludge water. As the upper layer of sludge water accumulates, it is pumped into primary settling tanks. Subsequent dehydration of the sludge occurs due to the evaporation of moisture from the surface.

The area of sludge beds depends on the volume of sediment, the type of soil on which they will be organized, climatic conditions and sediment consistency. Natural drying can be accelerated by turning the sludge. During this process it is removed vegetation layer and the surface crust is destroyed, which accelerates the drying of the sediment in the warm, dry season and promotes deeper freezing in the winter. Natural cycle sites depend on climatic conditions, which is important when creating a project and subsequent operation of such sites.

GC "Poleka" is engaged in the design, installation and subsequent maintenance of treatment facilities, including the maintenance of sludge beds. We offer our clients turnkey services and provide equipment quality guarantees with a service life of up to 50 years. The use of modern and time-tested technologies allows us to create reliable and easy-to-use treatment facilities.

Lyubertsy wastewater treatment plant (WTP) power 3 million m 3 /day, which are the largest in Europe, provide the reception and treatment of household and industrial wastewater from the North-Western, North-Eastern and Eastern regions of Moscow, as well as cities in the forest park zone: Khimki, Dolgoprudny, Mytishchi, Balashikha, Reutovo, Zheleznodorozhny, Lyubertsy.

Lyubertsy treatment facilities operate according to the traditional technological scheme of complete biological treatment: the first stage is mechanical treatment, including filtering water on screens, trapping mineral impurities in sand traps and settling water in primary settling tanks; the second stage is biological water purification in aeration tanks and secondary settling tanks. The processes occurring here are akin to self-purification processes in natural bodies of water - rivers and lakes, but the speed of the processes is increased many times thanks to specially developed technologies.

Technological diagram wastewater treatment at the Lyubertsy wastewater treatment plant

Complex VOC includes 3 independently functioning wastewater treatment units: Old Station (LOSst.) with a design capacity of 1.50 million m 3 per day, Unit I of the Novolubertsy wastewater treatment plant (NLOS-1) - 1 million m 3 per day and the second block of the Novolubertsy wastewater treatment plant (NVOS-2) - 500 thousand m 3 per day.

A special feature of the VOC is that it was introduced in 2006. nutrient removal unit where it happens deep removal nitrogen and phosphorus. In addition, in 2007, facilities were put into operation ultraviolet disinfection, with a capacity of 1 million m 3 /day of treated wastewater.

Large quantities of VOCs are supplied with wastewater various types garbage: household items of citizens, garbage food production, plastic container and plastic bags, as well as construction and other waste. To remove them from VOCs, two types of mechanized gratings with gaps of 5 and 6 mm are used.

The second stage of mechanical wastewater treatment is sand traps - structures used to remove mineral impurities contained in the incoming water. Mineral contaminants found in wastewater include: sand, clay particles, solutions of mineral salts, mineral oils.

After passing through the first two stages of mechanical treatment, wastewater enters primary settling tanks designed to precipitate undissolved impurities from wastewater. Structurally, all primary settling tanks at VOC are open type and have a radial shape, with different diameters - 40 and 54 m.

Clarified wastewater after primary settling tanks undergoes complete biological treatment in aeration tanks. Aero tanks – open reinforced concrete structures of rectangular shape, 2, 4 corridor type. Biological wastewater treatment is carried out using activated sludge with forced air supply.

The sludge mixture from the aeration tanks enters the secondary settling tanks, where the process of separating activated sludge from purified water occurs. Secondary settling tanks are structurally similar to primary settling tanks. Precipitation formed on various stages wastewater treatment, enter a single complex for sludge treatment.

Sludge generated at various stages of wastewater treatment enters a single sludge treatment complex, which includes
- belt thickeners to reduce sludge moisture,
- digesters for digestion and sludge stabilization in thermophilic mode (50-53 0 C),
- decanter centrifuges for sludge dewatering using flocculants.
Dewatered sludge is transported by third parties outside the territory of the treatment plant for the purpose of neutralization/disposal and/or use for the production of finished products.