→ Solutions for wastewater treatment plants
Examples of wastewater treatment plants in major cities
Before considering concrete examples treatment facilities, it is necessary to determine what the concepts of the largest, large, medium and small city mean.
With a certain degree of conventionality, it is possible to classify cities by the number of inhabitants or, taking into account professional specialization, by the amount of wastewater entering the treatment facilities. So for the largest cities with a population of more than 1 million people, the amount of wastewater exceeds 0.4 million m3 / day, for major cities with a population of 100 thousand to 1 million people, the amount of wastewater is 25-400 thousand m3 / day. In medium-sized cities, 50-100 thousand people live, and the amount of wastewater is 10-25 thousand m3 / day. In small towns and urban-type settlements, the number of inhabitants is from 3-50 thousand people (with a possible gradation of 3-10 thousand people; 10-20 thousand people; 25-50 thousand people). At the same time, the estimated amount of wastewater varies in a fairly wide range: from 0.5 to 10-15 thousand m3 / day.
Share of small towns in Russian Federation accounts for 90% of the total number of cities. It should also be taken into account that the water disposal system in cities can be decentralized and have several treatment facilities.
Consider the most illustrative examples large treatment facilities in the cities of the Russian Federation: Moscow, St. Petersburg and Nizhny Novgorod.
Kuryanovskaya aeration station (KSA), Moscow. Kuryanovskaya aeration station is the oldest and largest aeration station in Russia; using its example, one can quite clearly study the history of the development of equipment and technology for wastewater treatment in our country.
The area occupied by the station is 380 ha; design capacity - 3.125 million m3 per day; of which almost 2/3 are domestic and 1/3 industrial wastewater. The station has four independent block structures.
The development of the Kuryanovskaya aeration station began in 1950 after the commissioning of a complex of facilities with a capacity of 250 thousand m3 per day. An industrial-experimental technological and constructive base was laid on this block, which was the basis for the development of almost all aeration stations in the country, and was also used in the expansion of the Kuryanovskaya station itself.
On fig. 19.3 and 19.4 are technological schemes for wastewater treatment and sludge treatment of the Kuryanovskaya aeration station.
Wastewater treatment technology includes the following main facilities: gratings, sand traps, primary settling tanks, aeration tanks, secondary settling tanks, wastewater disinfection facilities. Part of the biologically treated wastewater undergoes post-treatment on granular filters.
Rice. 19.3. Technological scheme of wastewater treatment of the Kuryanovskaya aeration station:
1 - lattice; 2 - sand trap; 3 - primary sump; 4 - aerotank; 5 - secondary sump; 6 - flat slotted sieve; 7 - quick filter; 8 - regenerator; 9 - the main machine building of the CBO; 10 – sludge thickener; 11 – gravity belt thickener; 12 – flocculant solution preparation unit; 13 - industrial water pipeline structures; 14 – sand processing shop; 75 - incoming waste water; 16 - wash water from quick filters; 17 - sand pulp; 18 - water from the sand shop; 19 - floating substances; 20 - air; 21 – sludge from primary settling tanks at sludge treatment facilities; 22 - circulating activated sludge; 23 - filtrate; 24 - disinfected industrial water; 25 - technical water; 26 - air; 27 - thickened activated sludge for sludge treatment facilities; 28 - disinfected industrial water to the city; 29 - purified water in the river. Moscow; 30 - additionally treated wastewater in the river. Moscow
The KSA is equipped with mechanized gratings with 6 mm gaps with continuously moving scraper mechanisms.
Three types of sand traps are operated at KSA - vertical, horizontal and aerated. After dehydration and processing in a special workshop, sand can be used in road construction and for other purposes.
Radial type settlers with diameters of 33, 40 and 54 m are used as primary settling tanks at KSA. The design duration of sedimentation is 2 hours. Primary settling tanks in the central part have built-in preaerators.
Biological wastewater treatment is carried out in four-corridor displacer aerotanks, the percentage of regeneration is from 25 to 50%.
Air for aeration is supplied to the aeration tanks through filter plates. Currently for selection optimal system aeration in a number of sections of aerotanks, tubular polyethylene aerators of the Ecopolymer company, plate aerators of the Greenfrog and Patfil companies are being tested.
Rice. 19.4. Technological scheme for processing sediments of the Kuryanovskaya aeration station:
1 – loading chamber digester; 2 – digester; 3 – unloading chamber of digesters; 4 - gas holder; 5 - heat exchanger; 6 - mixing chamber; 7 - washing tank; 8 – digested sludge compactor; 9 - filter press; 10 – flocculant solution preparation unit; 11 - silt platform; 12 – sludge from primary settling tanks; 13 - excess activated sludge; 14 - gas per candle; 15 - fermentation gas to the boiler room of the aeration station; 16 - technical water; 17 - sand on sand platforms; 18 - air; 19 - filtrate; twenty - drain water; 21 - sludge water to the city sewer
One of the sections of the aeration tanks was reconstructed to operate on a single-sludge nitride-denitrification system, which also includes a phosphate removal system.
Secondary settling tanks, as well as primary ones, are of the radial type, with diameters of 33, 40 and 54 m.
About 30% of biologically treated wastewater undergoes post-treatment, which is first treated on flat slotted sieves and then on granular filters.
For sludge digestion at KSA, buried methane tanks with a diameter of 24 m from monolithic reinforced concrete with earth sprinkling, ground with a diameter of 18 m with thermal insulation of the walls. All digesters operate according to the flow scheme, in thermophilic mode. The escaping gas is diverted to the local boiler house. After the digesters, the fermented mixture of raw sludge and excess activated sludge is subjected to compaction. Of the total amount of the mixture, 40-45% is sent to sludge sites, and 55-60% is sent to the mechanical dehydration shop. The total area of silt pads is 380 ha.
Mechanical dehydration of sludge is carried out on eight filter presses.
Luberetskaya aeration station (LbSA), Moscow. More than 40% of wastewater in Moscow and large cities of the Moscow region is treated at the Luberetskaya aeration station (LbSA), located in the village of Nekrasovka, Moscow region (Fig. 19.5).
LbSA was built in pre-war years. The technological process of cleaning consisted in the mechanical treatment of wastewater and subsequent treatment in the fields of irrigation. In 1959, by decision of the government, construction of an aeration station began on the site of the Lyubertsy irrigation fields.
Rice. 19.5. The plan of the treatment facilities of the Luberetskaya and Novoluberetskaya aeration stations:
1 – wastewater supply to LbSA; 2 – wastewater supply to NLbSA; 3 - LbSA; 4 - NLbSA; 5 – facilities for sludge treatment; b - releases of treated wastewater
The technological scheme of wastewater treatment at the LbSA practically does not differ from the adopted scheme at the KSA and includes the following facilities: grids; sand traps; primary settling tanks with preaerators; aeration tanks-displacers; secondary clarifiers; sludge treatment and wastewater disinfection facilities (Fig. 19.6).
In contrast to the structures of the KSA, most of which were built of monolithic reinforced concrete, prefabricated reinforced concrete structures were widely used at the LbSA.
After the construction and commissioning in 1984 of the first block, and subsequently the second block of the treatment facilities of the Novoluberetsk aeration station (NLbSA), throughput LbSA is 3.125 million m/day. The technological scheme of wastewater treatment and sludge treatment at LbSA practically does not differ from classical scheme adopted by the KSA.
However, in last years at the Lyubertsy station, a lot of work is being done to modernize and reconstruct wastewater treatment facilities.
New foreign and domestic small-gauge mechanized gratings (4-6 mm) were installed at the station, as well as the modernization of existing mechanized gratings was carried out according to the technology developed at the Moscow State Enterprise "Mosvodokanal" with a decrease in the size of the ditches to 4-5 mm.
Rice. 19.6. Technological scheme of wastewater treatment of the Luberetskaya aeration station:
1 - waste water; 2 - gratings; 3 - sand traps; 4 - preaerators; 5 - primary settling tanks; 6 - air; 7 - aeration tanks; 8 - secondary settling tanks; 9 – sludge thickeners; 10 - filter presses; 11 – dehydrated sludge storage areas; 12 - reagent facilities; 13 – digested sludge compactors before filter presses; 14 - sludge preparation unit; 15 – digesters; 16 - sand bunker; 17 - sand classifier; 18 - hydrocyclone; 19 - gas holder; 20 - boiler room; 21 - hydraulic presses for waste dewatering; 22 - emergency release
Most Interest causes the technological scheme of the II block of NLbSa, which is a modern single-silt scheme of nit-ri-denitrification with two stages of nitrification. Along with the deep oxidation of carbon-containing organic substances, a deeper process of nitrogen oxidation of ammonium salts occurs with the formation of nitrates and a decrease in phosphates. The introduction of this technology allows in the near future to receive purified wastewater at the Lyubertsy aeration station, which would meet modern regulatory requirements for discharge into reservoirs for fishery purposes (Fig. 19.7). For the first time, about 1 million m3/day of wastewater at LbSA is subjected to deep biological treatment with the removal of nutrients from treated wastewater.
Almost all raw sludge from primary settling tanks, before fermentation in digesters, passes pre-processing on the bars. The main technological processes for the treatment of sewage sludge at LbSA are: gravity compaction of excess activated sludge and raw sludge; thermophilic fermentation; washing and compaction of digested sludge; polymer conditioning; mechanical neutralization; deposit; natural drying (emergency silt pads).
Rice. 19.7. Technological scheme of wastewater treatment at LbSA according to the single-silt scheme of nitrification-denitrification:
1 - initial waste water; 2 – primary settler; 3 - clarified waste water; 4 - aerotank-denitrifier; 5 - air; 6 - secondary sump; 7 - treated waste water; 8 - recirculating activated sludge; 9 - raw sediment
For sludge dehydration, new frame filter-presses were installed, which make it possible to obtain a cake with a moisture content of 70-75%.
Central aeration station, St. Petersburg. Wastewater treatment plant central station aeration of St. Petersburg are located at the mouth of the river. Neva on the artificially reclaimed Bely Island. The station was put into operation in 1978; the design capacity of 1.5 million m3 per day was reached in 1985. The built-up area is 57 hectares.
The central aeration station of St. Petersburg receives and processes about 60% of domestic and 40% of industrial wastewater in the city. Saint Petersburg is the most Big city in the Baltic Sea basin, this imposes a special responsibility for ensuring its environmental safety.
The technological scheme of wastewater treatment and sludge treatment of the Central aeration station in St. Petersburg is shown in fig. 19.8.
Max Flow waste water pumped by the pumping station in dry weather is 20 m3/s and in rainy weather - 30 m/s. Wastewater coming from the inlet collector of the city drainage network is pumped into the mechanical treatment inlet chamber.
The structure of mechanical treatment facilities includes: a receiving chamber, a grate building, primary settling tanks with grease collectors. Initially, wastewater is treated on 14 mechanized rake and stepped screens. After the screens, the wastewater enters the sand traps (12 pcs.) and then through the distribution channel is discharged to three groups of primary sedimentation tanks. Primary settling tanks of radial type, in the amount of 12 pieces. The diameter of each sump is 54 m at a depth of 5 m.
Rice. 19.8. Technological scheme of wastewater treatment and sludge treatment of the Central Station of St. Petersburg:
1 - sewage from the city; 2 - main pumping station; 3 - supply channel; 4 - mechanized gratings; 5 - sand traps; 6 - garbage; 7 - sand; 8 - sand; sites; 9 - primary settling tanks; 10 – wet sludge tank; 11 - aeration tanks; 12 - air; 13 - superchargers; 14 - return activated sludge; 15 - sludge pumping station; 16 - secondary settling tanks; 17 - release chamber; 18 - Neva river; 19 - activated sludge; 20 - sludge thickeners; 21 - receiving tank;
22 - centrifuges; 23 – cake for combustion; 24 - sludge incineration; 25 - oven; 26 - ash; 27 - flocculant; 28 - drain water of sludge thickeners; 29 - water; 30 - solution
flocculant; 31 - centrifuge
The structure of biological treatment facilities includes aerotanks, radial settling tanks and the main machine building, which includes a block of blowers and sludge pumps. Aerotanks consist of two groups, each of which is six parallel three-corridor aerotanks 192 m long with a common upper and lower channels, the width and depth of the corridors are 8 and 5.5 m, respectively. Air is supplied to the aerotanks through fine-bubble aerators. The regeneration of activated sludge is 33%, while the return activated sludge from the secondary settling tanks is fed into one of the aeration tank corridors, which serves as a regenerator.
From the aerotanks, purified water is sent to 12 secondary settling tanks to separate activated sludge from biologically treated wastewater. Secondary settling tanks, as well as primary ones, are of a radial type with a diameter of 54 m and a settling zone depth of 5 m. From the secondary settling tanks, activated sludge enters the sludge pumping station under hydrostatic pressure. After the secondary settling tanks, the purified water is discharged into the river through the outlet chamber. Neva.
In the shop for mechanical sludge dewatering, raw sludge from primary settling tanks and compacted activated sludge from secondary settling tanks are processed. The main equipment of this workshop is ten centrifuges equipped with systems for preheating a mixture of raw sludge and activated sludge. To increase the degree of moisture transfer of the mixture, a flocculant solution is fed into the centrifuges. After processing in centrifuges, the moisture content of the cake reaches 76.5%.
In the sludge incineration shop, 4 fluidized bed furnaces (French company OTV) are installed.
Distinctive feature of these treatment plants is that there is no pre-digestion in digesters in the sludge treatment cycle. Dehydration of the mixture of sediments and excess activated sludge occurs directly in the centrifuges. The combination of centrifuges and incineration of compacted sludge dramatically reduces the volume final product-ash. Compared to conventional mechanical sludge treatment, the resulting ash is 10 times less than dehydrated cake. Using the method of burning a mixture of sludge and excess activated sludge in fluidized bed furnaces guarantees sanitary safety.
Aeration station, Nizhny Novgorod. The Nizhny Novgorod aeration station is a complex of facilities designed for complete biological treatment of domestic and industrial wastewater in Nizhny Novgorod and the city of Bor. The following structures are included in the technological scheme: mechanical treatment unit - gratings, sand traps, primary settling tanks; biological treatment unit - aerotanks and secondary settling tanks; post-treatment; sludge treatment facilities (Figure 19.9).
Rice. 19.9. Technological scheme of wastewater treatment at the Nizhny Novgorod aeration station:
1 - wastewater receiving chamber; 2 - gratings; 3 - sand traps; 4 - sand platforms; 5 - primary settling tanks; 6 - aeration tanks; 7 - secondary settling tanks; 8 - pumping station for excess activated sludge; 9 - airlift chamber; 10 - biological ponds; 11 - contact reservoirs; 12 - release in the river. Volga; 13 – sludge thickeners; 14 – raw sludge pumping station (from primary settling tanks); 75 – digesters; 16 - sludge pumping station; 17 - flocculant; 18 - filter press; 19 - silt pads
The design capacity of the facilities is 1.2 million m3/day. The building has 4 mechanized gratings with a capacity of 400 thousand m3/day each. Waste from the grates is moved by means of conveyors, dumped into bunkers, chlorinated and taken to the landfill for composting.
Sand traps include two blocks: the first consists of 7 horizontal aerated sand traps with a capacity of 600 m3/h each, the second - of 2 horizontal slotted sand traps with a capacity of 600 m3/h each.
8 primary radial settling tanks with a diameter of 54 m were built at the station. To remove floating impurities, the settling tanks are equipped with grease collectors.
4-corridor aeration tanks-mixers are used as biological treatment facilities. The dispersed inlet of wastewater into the aerotanks allows changing the volume of regenerators from 25 to 50%, ensuring good mixing of incoming water with activated sludge and uniform oxygen consumption along the entire length of the corridors. The length of each aeration tank is 120 m, the total width is 36 m, and the depth is 5.2 m.
The design of the secondary settling tanks and their dimensions are similar to the primary ones; in total, 10 secondary settling tanks were built at the station.
After the secondary settling tanks, the water is sent for post-treatment to two biological ponds with natural aeration. Biological ponds are built on a natural foundation and lined with earthen dams; the water surface area of each pond is 20 ha. The residence time in biological ponds is 18-20 hours.
After bioponds, treated wastewater is disinfected in contact tanks using chlorine.
Purified and disinfected water through the Parshall trays enters the drainage canals and, after saturation with oxygen in the spillway overflow device, enters the river. Volga.
A mixture of raw sludge from primary settling tanks and compacted excess activated sludge is sent to digesters. Thermophilic mode is maintained in the digesters.
The digested sludge is partly fed to sludge beds and partly to a belt filter press.
And today I will tell you about sewerage and water recycling in a modern metropolis. Thanks to a recent trip to the South-Western sewage treatment plant in St. Petersburg, I and several of my companions turned from simple bloggers into world-class experts in water collection and purification technologies at once, and now we will be happy to show and tell you how it all works!
A pipe from which a powerful jet pours rating social capital the contents of a sewer
Aerotanks YuZOS
So, let's begin. Water diluted with soap and shampoo, street dirt, industrial waste, food leftovers, as well as the results of this digestion food (all this goes into the sewer, and then to the sewage treatment plant) has a long and thorny path before she again believes in the Neva or the Gulf of Finland. This path begins either in the drain grate, if it happens on the street, or in the “fan” pipe, if we are talking about apartments and offices. From not so big (15 cm in diameter, everyone has probably seen them at home in the bathroom or toilet rooms) fan pipes water mixed with waste enters larger common house pipes. Several houses (as well as street drains in the surrounding area) are combined into a local catchment area, which, in turn, are combined into sewerage areas and further into sewerage pools. At each stage, the diameter of the pipe with sewage increases, and in tunnel collectors it already reaches 4.7 m. Through such a hefty pipe, dirty water slowly (by gravity, no pumps) reaches the aeration stations. In St. Petersburg there are three large ones that fully supply the city, and several smaller ones in remote areas such as Repino, Pushkin or Kronstadt.
Yes, about the treatment facilities themselves. Some may have a perfectly reasonable question - “Why bother treating wastewater at all? The bay with the Neva will endure everything! In general, this was how it used to be, until 1978, the drains were practically not cleaned in any way and immediately fell into the bay. The bay processed them poorly, coping, however, with the increasing flow of sewage every year is getting worse. Naturally, this state of affairs could not but affect the environment. Our Scandinavian neighbors suffered the most, but the neighborhoods of St. Petersburg also experienced Negative influence. And the prospect of a dam across the Finnish made me think that the waste of a million-plus city, instead of a happy swim in the Baltic Sea, will now hang out between Kronstadt and (then still) Leningrad. In general, the prospects of choking with sewage over time did not please anyone, and the city, represented by Vodokanal, gradually began to solve the problem of wastewater treatment. It can be considered almost completely solved only last year - in the fall of 2013, the main sewer collector of the Northern part of the city was launched, after which the amount of treated water reached 98.4 percent.
Sewerage basins on the map of St. Petersburg
Let's look at the example of the South-West Treatment Plant, how the treatment takes place. Having reached the very bottom of the collector (the bottom is just on the territory of the treatment plant), the water rises to a height of almost 20 meters with powerful pumps. This is necessary in order to dirty water passed the stages of cleaning under the action of gravity, with minimal involvement of pumping equipment.
The first stage of cleaning - grates, on which large and not very large debris remains - all sorts of rags, dirty socks, drowned kittens, lost Cell phones and other wallets with documents. Most of the collected goes straight to the landfill, but the most curious finds remain in a makeshift museum.
Pumping station
Swimming pool with sewage. outside view
Swimming pool with sewage. Inside view
This room has grates that catch large debris.
Behind the muddy plastic, you can see the grate assembled. Paper and labels stand out
Brought by water
And the water moves on, the next step is sand traps. The task of this stage is to collect coarse impurities and sand - everything that passed by the gratings. Chemical reagents are added to the water to remove phosphorus before being released from the sand traps. Further, the water is sent to the primary settling tanks, in which suspended and floating substances are separated.
Primary settlers complete the first stage of purification - mechanical and partially chemical. Filtered and settled water does not contain debris and mechanical impurities, but it is still full of not the most useful organic matter, and many microorganisms also live. It is also necessary to get rid of all this, and start with organic ...
sand traps
The structure in the foreground slowly moves along the pool
Primary clarifiers. The water in the sewer has a temperature of about 15-16 degrees, steam is actively coming from it, since the ambient temperature is lower
The biological treatment process takes place in aerotanks - these are hefty bathrooms into which water is poured, air is pumped in and "activated sludge" is launched - a cocktail of the simplest microorganisms, sharpened to digest precisely those chemical compounds that you need to get rid of. The air pumped into the tanks is needed to increase the activity of microorganisms, under such conditions they almost completely "digest" the contents of the bath in five hours. Further, biologically purified water is sent to secondary settling tanks, where activated sludge is separated from it. The sludge is again sent to the aeration tanks (except for the excess that is burned), and the water enters the last stage of purification - ultraviolet treatment.
Aerotanks. The effect of "boiling" due to active air injection
Control room. You can see the entire station from above.
Secondary sump. For some reason, the water in it is very attractive to birds.
At the South-Western Treatment Facilities, subjective quality control of treatment is also carried out at this stage. It looks like this - purified and disinfected water is poured into a small aquarium in which several crayfish sit. Crayfish are very fastidious creatures, they react immediately to dirt in the water. Since people have not yet learned to distinguish between the emotions of crustaceans, a more objective assessment is used - a cardiogram. If suddenly several (protection against false positives) crayfish experienced severe stress, then something is wrong with the water, and you need to urgently figure out which of the cleaning stages failed.
But this is an emergency situation, and in the usual order of things already pure water goes to the Gulf of Finland. Yes, about cleanliness. Although crayfish exist in such water, and microbes-viruses are all removed from it, it is still not recommended to drink it . Nevertheless, the water fully complies with the environmental standards of HELCOM (the convention for the protection of the Baltic from pollution), which in recent years has already had a positive effect on the state of the Gulf of Finland.
Ominous green light disinfects water
Cancer detector. Not an ordinary rope is attached to the shell, but a cable through which data about the state of the animal is transmitted
clack clack
I will say a few more words about the disposal of everything that is filtered out of the water. solid waste they are transported to landfills, but everything else is burned at a plant located on the territory of a treatment plant. The dehydrated sludge from the primary settling tanks and excess activated sludge from the secondary ones are sent to the furnace. Burning takes place at a relatively high temperature (800 degrees) for maximum reduction harmful substances in the exhaust. Surprisingly, only a small part, about 10%, of the total volume of the plant's premises, stoves occupy. The remaining 90% is given to a huge system of various filters that screen out all possible and impossible harmful substances. By the way, a similar subjective system of “quality control” has been introduced at the plant. Only the detectors are no longer crayfish, but snails. But the principle of operation is generally the same - if the content of harmful substances at the outlet of the pipe is higher than the permissible one, the mollusk's body will immediately react.
Furnaces
P blow-off valves of the waste heat boiler. The purpose is not completely clear, but how impressive they look!
Snail. Above her head is a tube from which water drips. And next to it is another one with an exhaust
P.S. One of the most popular questions that were asked for the announcement - "Well, what's with the smell? It stinks, right?". I turned out to be somewhat disappointed with the smell :) The uncleaned contents of the sewer (in the very first photo) practically do not smell. On the territory of the station, the smell, of course, is present, but very moderate. The strongest stink (and this is already noticeable!) is the dehydrated sludge from the primary settling tanks and activated sludge - that which is sent to the stove. Therefore, by the way, they began to burn them, the landfills to which silt was previously brought gave very much bad smell for the neighborhood...
Other interesting posts on the topic of industry and production.
Kuryanovsk treatment facilities (KOS) design capacity 2.2 million m 3 / day, which are the largest in Europe, provide reception and treatment of domestic and industrial wastewater from the northwestern, western, southern, southeastern regions of Moscow (60% of the city) and, in addition, a number of cities and settlements Moscow suburbs.The composition of the WWTP includes three independently functioning wastewater treatment units: the old station (KTPst.) with a design capacity of 1.0 million m 3 per day and the II block of the Novokurianovsk treatment facilities (NKOS-II) - 600 thousand m 3 per day.
WWTPs operate according to the technological scheme of complete biological treatment, including at the reconstructed facilities of NKOS-I and NKOS-II with the removal of biogenic elements: the first stage is mechanical treatment, including filtering water on grates, trapping mineral impurities in sand traps and settling water in primary sedimentation tanks ; the second stage is the biological treatment of water in aerotanks and secondary settling tanks. Part of the biologically treated wastewater is subjected to post-treatment on fast filters and is used for the needs of industrial enterprises instead of tap water.
With sewage, a large amount of various kinds waste: household items of citizens, waste from food production, plastic container and plastic bags as well as construction and other debris. To remove them at the WWTP, mechanized gratings with 10 mm gaps are used.
The second stage of mechanical wastewater treatment is sand traps - structures that serve to remove mineral impurities contained in incoming water. Mineral contaminants in wastewater include: sand, clay particles, solutions of mineral salts, mineral oils. The WWTP operates different types sand traps - vertical, horizontal and aerated.
After passing the first two stages of mechanical treatment, wastewater enters the primary settling tanks, designed to precipitate undissolved impurities from wastewater. Structurally, all primary clarifiers at WWTP open type and have a radial shape, with different diameters - 33, 40 and 54 m.
The clarified wastewater after the primary settling tanks is subjected to complete biological treatment in aeration tanks. Aerotanks – open reinforced concrete structures rectangular shape, 4-way type. The working depth of the aerotanks of the old block is 4 m, the aerotanks of the NKOS - 6 m. 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 activated sludge is separated from the purified water. Secondary clarifiers are structurally similar to primary clarifiers.
The entire volume of wastewater treated at the WWTP is delivered to the post-treatment facilities. The productivity of the straining section is 3 million m 3 /day, which allows the entire volume of biologically purified water to be passed through flat slotted sieves. Part of the water after filtering is filtered on fast filters and used for technical needs as a circulating water supply.
Since 2012, all wastewater that has passed full cycle treatment at the Kuryanovsk treatment facilities, are subjected to ultraviolet disinfection before being discharged into the Moskva River (capacity 3 million m 3 / day). Thanks to this, the indicators of bacterial contamination of the biologically purified water of the WWTP reached the standard values, which had a beneficial effect on the quality of the water of the Moscow River and the sanitary and epidemiological state of the water area as a whole.
Precipitation formed on various stages wastewater treatment, are fed to a single sludge treatment complex, which includes:
- belt thickeners to reduce sludge moisture,
- digesters for digestion and stabilization of sludge in thermophilic mode (50-53 0 C),
- decanter centrifuges for sludge dewatering using flocculants.
The dehydrated sludge is taken out by third parties outside the territory of the treatment facilities for the purpose of neutralization/utilization and/or use for the production of finished products.
Different conditions for dealing with plums and the difference in the tasks solved in this case led to the creation different types treatment facilities. For example, stormwater treatment facilities, in terms of their configuration and capabilities, are designed to treat surface runoff; local, depending on the equipment, are used for preliminary treatment of polluted waters of certain workshops, industries.
The urban type of treatment facilities, unlike others, is more versatile and can treat any type of liquid waste, but under one condition (which distinguishes it from others) - all of them must be brought to certain characteristics, established standards. Among them: the concentration of impurities; effluent acidity (pH), which should be between 8.5 and 6.5.
City drains
This type of effluent is distinguished by the content of a wide variety of organic compounds and particles as pollutants. inorganic substances. Some of them are quite harmless (for example, sand, particles of dust, dirt), others (oil, oil products, toxins, heavy metals) are dangerous and, when released into nature, cause irreparable harm to it, cause deterioration in human health, and lead to epidemics.
According to experts, urban wastewater to be treated contains on average (in mg/l):
- PVA ………………………………………..…………....10;
- dry residue ………………………….…………… 800;
- suspended solids ……………………….……....259;
- nitrogen of ammonium salts …………………………...30;
- total nitrogen ……………………..……..……………..45;
- phosphates ……………………..…………………..…….15;
- chlorides ………………………….………………..…...35;
- BODfull ……………………………………..……….. 280;
- BOD5 …………………………………………..………..200.
Description of treatment facilities for the city
Most often, urban treatment facilities include four units of treatment equipment: mechanical (or preliminary), biological, deep treatment, final treatment of wastewater.
In the first, mechanical, sand and large debris are removed from the drains. To do this, when treating urban wastewater, sieves, screens of various designs (mechanical drum, screw, rake, etc.), sand traps, and sand separators are used.
The preliminarily treated effluents received at the second unit are freed from nitrogen compounds and most organic impurities. This is done using special bioreactors, the operation of which is based on the ability of microorganisms to process pollution included in the effluent during their life. At the same time, hazardous impurities "pass" into the category of non-hazardous and in suspension, which are removed in the following stages.
The third unit at the municipal wastewater treatment plant is engaged in the treatment of wastewater from suspended solids that appeared during previous operations and those that cannot be removed by biomethods. Various equipment helps to make this: flotation plants, settling tanks, separators, filters. At the final stage, the purified water is disinfected, and finally brought to the standards that comply with the requirements established by the sanitary and epidemiological rules.
In addition to the above, there are sections at the city sewage treatment plants that are engaged in the processing and disposal of sludge formed during the treatment of urban wastewater. They are equipped with installations where sludge is freed from excess moisture (belt and chamber filter presses, decanters). There are filtration fields and bioponds.
All facilities related to urban wastewater treatment facilities are always fenced and closed from unauthorized access by outsiders. They constantly monitor the indicators of wastewater treatment, the state of atmospheric air.
Improving urban wastewater treatment facilities
This type of treatment system is capital intensive. It requires high construction costs, constant cash costs during operation. Therefore, any measures that allow to reduce costs, and even more so to bring the process to a level of self-sufficiency, self-sufficiency, and even better - to profit, are considered by specialists very carefully and with interest.
Among these is a recently published report on studies that have been carried out with effluents from different cities US specialists from the University of Arizona. They once again confirmed the possibility of making money on the treatment of urban wastewater, extracting them and sludge, metals and substances valuable for industry.
The increased interest in the results of their research is caused by the fact confirming the presence of precious metals in the effluents. Moreover, their presence is quite large and amounts to a ton of silt: for gold ¾ g, for silver 16.7 g. According to their estimates, only the extraction of these metals will allow the treatment facilities of a million-plus city to earn up to 2.6 million US dollars a year.
No less interesting are reports about the possibility of obtaining electricity during the treatment of urban wastewater. Realization of this is possible along the path of creating microbiological fuel cells, which is what many scientists in the industry are doing. Until recently, the effectiveness of the direction was low, but everything changed radically after the discovery of engineers working at the University of Oregon in the USA.
Thanks to the use of a reduced cathode-anode arrangement, a developed bacterial environment and new separating materials, they managed to obtain an amount of electricity in the process of processing wastewater that exceeds previous achievements by 100 times. Such a result, according to the estimates of the same engineers, allows us to assert the effectiveness of the technology and the possibility of transferring experiments to real treatment facilities.
Hopes to turn the process of treating municipal wastewater into a self-sufficiency in the production of their own electricity may be too optimistic. But even with their partial implementation, the effect of this event is expected to be stunning, and therefore deserves attention and prompt implementation.