The Rublevskaya water treatment station is located near Moscow, a couple of kilometers from the Moscow Ring Road, in the northwest. It is located right on the banks of the Moscow River, from where it takes water for purification.
A little further up the Moscow River is the Rublevskaya Dam.
The dam was built in the early 30s. Currently, it is used to regulate the level of the Moscow River so that the water intake of the Western Water Treatment Station, which is located several kilometers upstream, can function.
Let's go upstairs:
The dam uses a roller design - the gate moves along inclined guides in niches using chains. The mechanism drives are located on top of the booth.
Upstream there are water intake canals, the water from which, as I understand it, goes to the Cherepkovsky treatment plant, located not far from the station itself and being part of it.
Sometimes, Mosvodokanal uses a hovercraft to take water samples from the river. Samples are taken several times daily at several points. They are needed to determine the composition of water and select the parameters of technological processes for its purification. Depending on the weather, time of year and other factors, the composition of the water changes greatly and is constantly monitored.
In addition, water samples from the water supply system are taken at the exit from the station and at many points throughout the city, both by the Mosvodokanal workers themselves and by independent organizations.
There is also a small hydroelectric power station, which includes three units.
It is currently shut down and taken out of service. Replacing equipment with new ones is not economically feasible.
It's time to move to the water treatment station itself! The first place we'll go is the first lift pumping station. It pumps water from the Moscow River and lifts it up to the level of the station itself, which is located on the right, high bank of the river. We enter the building, at first the atmosphere is quite ordinary - bright corridors, information stands. Suddenly there is a square opening in the floor, under which there is a huge empty space!
However, we will return to it later, but for now let’s move on. A huge hall with square pools, as far as I understand, these are something like receiving chambers into which water flows from the river. The river itself is on the right, outside the windows. And the pumps pumping water are on the lower left behind the wall.
From the outside the building looks like this:
Photo from the Mosvodokanal website.
There is equipment installed here, it looks like an automatic station for analyzing water parameters.
All the structures at the station have a very bizarre configuration - many levels, all kinds of stairs, slopes, tanks, and pipes-pipes-pipes.
Some kind of pump.
We go down about 16 meters and find ourselves in the machine room. There are 11 (three spare) high-voltage motors installed here that drive centrifugal pumps at a lower level.
One of the spare motors:
For nameplate lovers :)
Water is pumped from below into huge pipes that run vertically through the hall.
All electrical equipment at the station looks very neat and modern.
Handsome guys:)
Let's look down and see a snail! Each such pump has a capacity of 10,000 m 3 per hour. For example, he could completely fill an ordinary three-room apartment with water from floor to ceiling in just a minute.
Let's go down one level. It's much cooler here. This level is below the level of the Moscow River.
Untreated water from the river flows through pipes into the treatment plant block:
There are several such blocks at the station. But before we go there, let's first visit another building called the Ozone Production Workshop. Ozone, also known as O3, is used to disinfect water and remove harmful impurities from it using the ozone sorption method. This technology has been introduced by Mosvodokanal in recent years.
To produce ozone, the following technical process is used: air is pumped under pressure using compressors (on the right in the photo) and enters the coolers (on the left in the photo).
In a cooler, the air is cooled in two stages using water.
Then it is fed to dryers.
A dehumidifier consists of two containers containing a mixture that absorbs moisture. While one container is in use, the second one restores its properties.
On the back side:
The equipment is controlled using graphic touch screens.
Next, the prepared cold and dry air enters the ozone generators. An ozone generator is a large barrel, inside of which there are many electrode tubes, to which high voltage is applied.
This is what one tube looks like (in each generator out of ten):
Brush inside the tube :)
Through the glass window you can look at the very beautiful process of producing ozone:
It's time to inspect the wastewater treatment plant. We go inside and climb the stairs for a long time, as a result we find ourselves on the bridge in a huge hall.
Now is the time to talk about water purification technology. I’ll say right away that I’m not an expert and I only understood the process in general terms without much detail.
After the water rises from the river, it enters the mixer - a structure of several successive basins. There, different substances are added to it one by one. First of all, powdered activated carbon (PAC). Then a coagulant (polyoxychloride of aluminum) is added to the water - which causes small particles to collect into larger lumps. Then a special substance called a flocculant is introduced - as a result of which the impurities turn into flakes. The water then enters settling tanks, where all impurities are precipitated, and then passes through sand and carbon filters. Recently, another stage has been added - ozone sorption, but more on that below.
All main reagents used at the station (except liquid chlorine) in one row:
In the photo, as far as I understand, there is a mixer room, find the people in the frame :)
All kinds of pipes, tanks and bridges. Unlike sewer treatment plants, everything here is much more confusing and not so intuitive, in addition, if most of the processes there take place outside, then water preparation takes place entirely indoors.
This hall is only a small part of a huge building. Part of the continuation can be seen in the openings below, we will go there later.
There are some pumps on the left, huge tanks with coal on the right.
There is also another stand with equipment measuring some characteristics of water.
Ozone is an extremely dangerous gas (first, highest hazard category). A strong oxidizing agent, inhalation of which can be fatal. Therefore, the ozonation process takes place in special indoor pools.
All kinds of measuring equipment and pipelines. On the sides there are portholes through which you can look at the process, on top there are spotlights that also shine through the glass.
The water inside is bubbling very actively.
The spent ozone goes to an ozone destructor, which consists of a heater and catalysts, where the ozone is completely decomposed.
Let's move on to filters. The display shows the speed of washing (blowing?) the filters. Filters become dirty over time and need to be cleaned.
Filters are long tanks filled with granular activated carbon (GAC) and fine sand according to a special pattern.
The filters are located in a separate space, isolated from the outside world, behind glass.
You can estimate the scale of the block. The photo was taken in the middle, if you look back you can see the same thing.
As a result of all stages of purification, the water becomes suitable for drinking and meets all standards. However, such water cannot be released into the city. The fact is that the length of Moscow's water supply networks is thousands of kilometers. There are areas with poor circulation, closed branches, etc. As a result, microorganisms can begin to multiply in the water. To avoid this, the water is chlorinated. Previously, this was done by adding liquid chlorine. However, it is an extremely dangerous reagent (primarily from the point of view of production, transportation and storage), so now Mosvodokanal is actively switching to sodium hypochlorite, which is much less dangerous. A special warehouse was built a couple of years ago for its storage (hello HALF-LIFE).
Again, everything is automated.
And computerized.
Eventually, the water ends up in huge underground reservoirs on the station grounds. These tanks fill and empty within 24 hours. The fact is that the station operates with more or less constant performance, while consumption varies greatly during the day - in the morning and evening it is extremely high, at night it is very low. The reservoirs serve as a kind of water accumulator - at night they are filled with clean water, and during the day it is taken from them.
The entire station is controlled from a central control room. Two people are on duty 24 hours a day. Everyone has a workstation with three monitors. If I remember correctly, one dispatcher monitors the water purification process, the second monitors everything else.
The screens display a huge number of various parameters and graphs. Surely this data is taken, among other things, from those devices that were above in the photographs.
Extremely important and responsible work! By the way, practically no workers were seen at the station. The whole process is highly automated.
In conclusion - a little surreal in the control room building.
Decorative design.
Bonus! One of the old buildings left over from the time of the very first station. Once upon a time it was all brick and all the buildings looked something like this, but now everything has been completely rebuilt, only a few buildings have survived. By the way, in those days water was supplied to the city using steam engines! You can read a little more detail (and look at old photos) in my
Modern ecology, alas, leaves much to be desired - all pollution of biological, chemical, mechanical, organic origin sooner or later penetrates the soil and water bodies. The supply of “healthy” clean water is becoming smaller every year, in which the constant use of household chemicals and the active development of production play a certain role. The wastewater contains a huge amount of toxic impurities, the removal of which must be complex and multi-level.
Different methods are used for water purification - the optimal choice is made taking into account the type of contaminants, desired results, and available capabilities.
The simplest option is . It is aimed at removing insoluble components that pollute water - these are fats and solid inclusions. First, the wastewater passes through grates, then sieves and ends up in settling tanks. Small components are deposited in sand traps, petroleum products are deposited in gasoline and oil traps, and in grease traps.
A more advanced cleaning method is membrane. It guarantees the most precise removal of contaminants. involves the use of appropriate organisms that oxidize organic inclusions. The basis of the technique is the natural purification of reservoirs and rivers at the expense of their population with beneficial microflora that removes phosphorus, nitrogen and other unnecessary impurities. The biological cleaning method can be anaerobic or aerobic. Aerobic requires bacteria, the life of which is impossible without oxygen - biofilters and aeration tanks filled with activated sludge are installed. The degree of purification and efficiency is higher than for a biofilter for wastewater treatment. Anaerobic purification does not require access to oxygen.
It involves the use of electrolysis, coagulation, as well as the precipitation of phosphorus with metal salts. Disinfection is carried out by ultraviolet irradiation, chlorine treatment, and ozonation. Disinfection with ultraviolet irradiation is a much safer and more effective method than chlorination, since it is carried out without the formation of toxic substances. UV radiation is harmful to all organisms, therefore it destroys all dangerous pathogens. Chlorination is based on the ability of active chlorine to act on microorganisms and destroy them. A significant drawback of the method is the formation of chlorine-containing toxins, carcinogenic substances.
Ozonation involves the disinfection of wastewater with ozone. Ozone is a gas with a triatomic molecular structure, a strong oxidizing agent that kills bacteria. The technique is expensive and is used to release ketones and aldehydes.
Thermal recovery is optimal for treating process wastewater when other methods are not effective. At modern treatment complexes, wastewater undergoes multi-component step-by-step treatment.
Primary mechanical treatment is always recommended, followed by biological treatment, additional treatment and disinfection of wastewater. 
Wastewater is water masses contaminated with industrial waste, for the removal of which from the areas of settlements and industrial enterprises appropriate sewer systems are used. Runoff also includes water formed as a result of precipitation. Organic inclusions begin to rot en masse, which causes deterioration in the condition of water bodies and air, and leads to the massive spread of bacterial flora. For this reason, important tasks of water treatment are the organization of drainage, wastewater treatment, and the prevention of active harm to the environment and human health.
The level of wastewater pollution must be calculated taking into account the concentration of impurities, expressed as mass per unit volume (g/m3 or mg/l). Domestic wastewater is a uniform formula in terms of composition; the concentration of pollutants depends on the volume of water mass consumed, as well as consumption standards.
Degrees and types of pollution of domestic wastewater:
Pollutants are also divided into organic, mineral, and biological. Mineral - these are slags, clay, sand, salts, alkalis, acids, etc. Organic - plant or animal, namely the remains of plants, vegetables, fruits, vegetable oils, paper, feces, tissue particles, gluten. Biological impurities – microorganisms, fungi, bacteria, algae.
Approximate proportions of pollutants in household wastewater:
The composition of industrial wastewater and the level of its pollution are indicators that vary depending on the nature of a particular production and the conditions for using wastewater in the technological process.
Atmospheric runoff is affected by climate, terrain, the nature of buildings, and the type of road surface.
Water treatment facilities must provide specified epidemic and radiation indicators and have a balanced chemical composition. After entering water treatment facilities, water undergoes complex biological and mechanical purification. To remove debris, wastewater is passed through a screen with rods. Cleaning is automatic, and operators also check the quality of contaminant removal every hour. There are new self-cleaning grilles, but they are more expensive.
For clarification, clarifiers, filters, and settling tanks are used. In settling tanks and clarifiers, water moves very slowly, as a result of which suspended particles begin to fall out to form sediment. From the sand traps, the liquid is directed to the primary settling tanks - mineral impurities also settle here, and light suspensions rise to the surface. The sediment is formed at the bottom; it is raked into pits using a truss with a scraper. The floating substances are sent to the grease trap, from there to the well and rolled away. 
The clarified water masses are sent to patches, then to aeration tanks. At this point, the mechanical removal of impurities can be considered complete - the turn of the biological one comes. The aeration tanks include 4 corridors, into the first one silt is supplied through tubes, and the water acquires a brown tint, continuing to be actively saturated with oxygen. The sludge contains microorganisms that also purify the water. The water is then sent to a secondary settling tank where it is separated from the sludge. The sludge goes through pipes into wells, from where pumps pump it into aeration tanks. Water is poured into contact-type tanks, where it was previously chlorinated, but now in transit.
It turns out that during primary purification, water is simply poured into a vessel, infused and drained. But this is precisely what makes it possible to remove most of the organic impurities at minimal financial cost. After water leaves the primary settling tanks, it goes to other water treatment facilities. Secondary purification involves the removal of organic residues. This is a biological stage. The main types of systems are activated sludge and trickling biological filters.
Through three collectors from the city, dirty water is supplied to mechanical screens ( the optimal gap is 16 mm), passes through them, the largest contaminant particles are deposited on the grid. Cleaning is automatic. Mineral impurities, which have a significant mass compared to water, follow through the hydraulic elevators, after which the hydraulic elevators are rolled back to the launch pads.
After leaving the sand traps, the water enters the primary settling tank (there are 4 in total). The floating substances are fed into the grease trap, from the grease trap into the well and rolled away. All operating principles described in this section are valid for different types of treatment systems, but may have certain variations taking into account the characteristics of a particular complex.
To choose the right treatment system, be sure to consider the type of wastewater. Available options:
Water quality indicators.
The main source of centralized household and drinking water supply in most regions of the Russian Federation is surface water of rivers, reservoirs and lakes. The amount of pollutants entering surface water supplies is varied and depends on the profile and volume of industrial and agricultural enterprises located in the catchment area.
In a one-stage water purification scheme, its clarification is carried out using filters or contact clarifiers. When purifying low-turbidity colored waters, a single-stage scheme is used.
Let us consider in more detail the essence of the main water treatment processes. Coagulation of impurities is the process of enlargement of tiny colloidal particles that occurs as a result of their mutual adhesion under the influence of molecular attraction.
Colloidal particles contained in water have negative charges and are in mutual repulsion, so they do not settle. The added coagulant forms positively charged ions, which promotes the mutual attraction of oppositely charged colloids and leads to the formation of enlarged particles (flakes) in the flocculation chambers.
Aluminum sulfate, ferrous sulfate, and aluminum polyoxychloride are used as coagulants.
The coagulation process is described by the following chemical reactions
Al 2 (SO 4) 3 →2Al 3+ +3SO 4 2-.
After introducing a coagulant into water, aluminum cations interact with it
Al 3+ +3H 2 O=Al(OH) 3 ↓+3H + .
Hydrogen cations are bound by bicarbonates present in water:
H + +HCO 3 - →CO 2 +H 2 O.
2H + +CO 3 -2 →H 2 O+CO 2.
The clarification process can be intensified using high-molecular flocculants (praestol, VPK - 402), which are introduced into the water after the mixer.
Thorough mixing of purified water with reagents is carried out in mixers of various designs. Mixing of reagents with water should be quick and carried out within 1 - 2 minutes. The following types of mixers are used: perforated (Fig. 1.8.2), baffle (Fig. 1.8.3) and vertical (vortex) mixers.
The perforated type mixer is used at water treatment stations with a capacity of up to 1000 m 3 /h. It is made in the form of a reinforced concrete tray with vertical partitions installed perpendicular to the movement of water and equipped with holes arranged in several rows.
Rice. 1.8.2. Hole mixer
The baffle mixer is used at water treatment plants with a capacity of no more than 500 - 600 m3/h. The mixer consists of a tray with three transverse vertical partitions. In the first and third partitions, passages for water are arranged, located in the central part of the partitions. The middle partition has two side passages for water adjacent to the walls of the tray. Thanks to this design of the mixer, turbulence occurs in the moving water flow, ensuring complete mixing of the reagent with water.
Rice. 1.8.3. Cloisonné mixer
At stations where water is treated with lime milk, the use of perforated and baffle mixers is not recommended, since the speed of water movement in these mixers does not ensure the maintenance of lime particles in suspension, which leads to their deposition in front of the partitions.
At water treatment plants, vertical mixers are most widely used (Fig. 1.8.4). This type of mixer can be square or round in plan, with a pyramidal or conical bottom.
Rice. 1.8.4. Vertical (vortex) mixer:
1 – supply of source water; 2 – drainage of water from the mixer
In partitioned flocculation chambers, a series of partitions are arranged that force the water to change the direction of its movement either in the vertical or horizontal plane, which ensures the necessary mixing of the water.
To mix the water and ensure a more complete agglomeration of small coagulant flakes into large ones, flocculation chambers are used. Their installation is necessary in front of horizontal and vertical settling tanks. For horizontal settling tanks, the following types of flocculation chambers should be installed: baffled, vortex, built-in with a layer of suspended sediment and bladed; for vertical settling tanks - whirlpool ones.
Removal of suspended substances from water (clarification) is carried out by settling it in settling tanks. Depending on the direction of water movement, sedimentation tanks are horizontal, radial and vertical.
A horizontal settling tank (Fig. 1.8.5) is a rectangular reinforced concrete tank. In its lower part there is a volume for the accumulation of sediment, which is removed through the channel. For more efficient removal of sediment, the bottom of the settling tank is made with a slope. The treated water enters through a distribution tray (or submerged weir). After passing through the sump, the water is collected by a tray or perforated (holey) pipe. Recently, settling tanks have been used with dispersed collection of clarified water, arranging special gutters or perforated pipes in their upper part, which allows increasing the productivity of settling tanks. Horizontal settling tanks are used at treatment plants with a capacity of more than 30,000 m 3 /day.
Fig.1.8.5. Horizontal settling tank:
1 – supply of source water; 2 – removal of purified water; 3 – sediment removal; 4 – distribution pockets; 5 – distribution grids; 6 – sediment accumulation zone; 7 – settling zone
A type of horizontal sedimentation tanks are radial sedimentation tanks, which have a mechanism for raking sediment into a pit located in the center of the structure. The sediment is pumped out from the pit. The design of radial settling tanks is more complex than horizontal ones. They are used to clarify waters with a high content of suspended solids (more than 2 g/l) and in recycling water supply systems.
Vertical sedimentation tanks (Fig. 1.8.6) are round or square in plan and have a conical or pyramidal bottom for sediment accumulation. These settling tanks are used subject to preliminary coagulation of water. The flocculation chamber, mainly a whirlpool, is located in the center of the structure. Water clarification occurs during its upward movement. Clarified water is collected in ring and radial trays. Sludge from vertical settling tanks is discharged under hydrostatic water pressure without shutting down the structure. Vertical settling tanks are mainly used at flow rates of 3000 m 3 /day.
Rice. 1.8.6. Vertical settling tank:
1 – flocculation chamber; 2 − Segner wheel with attachments; 3 – damper; 4 – supply of source water (from the mixer); 5 – collection trough of a vertical settling tank; 6 – pipe for removing sediment from a vertical settling tank; 7 - drainage of water from the sump
Clarifiers with a suspended layer of sediment are intended for preliminary clarification of water before filtration and only under the condition of preliminary coagulation.
Suspended sediment clarifiers can be of different types. One of the most common is a corridor-type clarifier (Fig. 1.8.7), which is a rectangular tank divided into three sections. The two outer sections are working clarifier chambers, and the middle section serves as a sediment compactor. The clarified water is supplied at the bottom of the clarifier through perforated pipes and is evenly distributed over the area of the clarifier. Then it passes through the suspended layer of sediment, is clarified and is discharged to filters through a perforated tray or pipe located at some distance above the surface of the suspended layer.
Fig.1.8.7. Corridor clarifier with suspended sediment with vertical sediment compactor:
1 – brightening corridors; 2 – sediment compactor; 3 −− supply of source water; 4 – collection pockets for drainage of clarified water; 5 – removal of sediment from the sediment compactor; 6 – removal of clarified water from the sediment compactor; 7 − precipitation windows with canopies
To deeply clarify water, filters are used that are capable of capturing almost all suspended matter from it. There are also filters for partial water purification. Depending on the nature and type of filter material, the following types of filters are distinguished: granular (filter layer - quartz sand, anthracite, expanded clay, burnt rock, granodiarite, expanded polystyrene, etc.); mesh (filter layer - mesh with cell size 20 - 60 microns); fabric (filter layer - cotton, linen, cloth, glass or nylon fabrics); alluvial (filter layer - wood flour, diatomaceous earth, asbestos chips and other materials, washed in the form of a thin layer on a frame made of porous ceramics, metal mesh or synthetic fabric).
Granular filters are used to purify household, drinking and industrial water from finely dispersed suspended matter and colloids; mesh - to retain coarse suspended and floating particles; fabric - for purifying low-turbidity waters at low-capacity stations.
Granular filters are used to purify water in public water supplies. The most important characteristic of filter operation is the filtration speed, depending on which filters are divided into slow (0.1 - 0.2), fast (5.5 - 12) and ultra-high-speed (25 - 100 m/h). Slow filters are used for low water flows without preliminary coagulation; ultra-high-speed - when preparing water for industrial purposes, for partial clarification of water.
The most widely used are rapid filters, in which pre-coagulated water is clarified (Fig. 1.8.8).
The water entering the rapid filters after the settling tank or clarifier should not contain suspended solids more than 12 - 25 mg/l, and after filtering the turbidity of the water should not exceed 1.5 mg/l
Rice. 1.8.8. Fast filter circuit:
1 – body; 2 – filter media; 3 – filtrate removal; 4 – supply of source water; 5 – removal of source water; 6 – lower drainage system; 7 – supporting layer; 8 – trough for collecting rinsing water; 9 − water supply for flushing
Contact clarifiers are similar in design to fast filters and are a type of them. Water clarification, based on the phenomenon of contact coagulation, occurs when it moves from bottom to top. The coagulant is introduced into the treated water immediately before it is filtered through a sand bed. In a short time before the start of filtration, only the smallest flakes of suspended matter are formed. The further coagulation process occurs on the loading grains, to which the previously formed tiny flakes stick. This process, called contact coagulation, occurs faster than conventional bulk coagulation and requires less coagulant. Contact clarifiers are washed by supplying water from below through a distribution system (as in conventional rapid filters).
Water disinfection. In modern treatment facilities, water is disinfected in all cases where the source of water supply is unreliable from a sanitary point of view. Disinfection can be carried out
Chlorination of water.
The chlorination method is the most common method of water disinfection. Typically, liquid or gaseous chlorine is used for chlorination. Chlorine has a high disinfecting ability, is relatively stable and remains active for a long time. It is easy to dose and control. Chlorine acts on organic substances, oxidizing them, and on bacteria, which die as a result of oxidation of substances that make up the protoplasm of cells. The disadvantage of water disinfection with chlorine is the formation of toxic volatile organohalogen compounds.
One of the promising ways to chlorinate water is to use sodium hypochlorite(NaClO), obtained by electrolysis of 2 - 4% sodium chloride solution.
Chlorine dioxide(ClO 2) reduces the possibility of the formation of side organochlorine compounds. The bactericidal power of chlorine dioxide is higher than that of chlorine. Chlorine dioxide is especially effective in disinfecting water with a high content of organic substances and ammonium salts.
The residual concentration of chlorine in drinking water should not exceed 0.3 - 0.5 mg/l
The interaction of chlorine with water is carried out in contact tanks. The duration of contact of chlorine with water before it reaches consumers must be at least 0.5 hours.
Germicidal irradiation.
The bactericidal property of ultraviolet rays (UV) is due to the effect on cellular metabolism and especially on the enzyme systems of the bacterial cell; in addition, under the influence of UV radiation, photochemical reactions occur in the structure of DNA and RNA molecules, leading to their irreversible damage. UV rays destroy not only vegetative but also spore bacteria, while chlorine affects only vegetative bacteria. The advantages of UV radiation include the absence of any effect on the chemical composition of water.
To disinfect water in this way, it is passed through an installation consisting of a number of special chambers, inside of which mercury-quartz lamps are placed, enclosed in quartz casings. Mercury-quartz lamps emit ultraviolet radiation. The productivity of such an installation, depending on the number of chambers, is 30…150 m 3 /h.
Operating costs for water disinfection by irradiation and chlorination are approximately the same.
However, it should be noted that with bactericidal irradiation of water it is difficult to control the disinfection effect, while with chlorination this control is carried out quite simply by the presence of residual chlorine in the water. In addition, this method cannot be used to disinfect water with increased turbidity and color.
Ozonation of water.
Ozone is used for the purpose of deep water purification and oxidation of specific organic pollutants of anthropogenic origin (phenols, petroleum products, surfactants, amines, etc.). Ozone makes it possible to improve the course of coagulation processes, reduce the dose of chlorine and coagulant, reduce the concentration of LHS, and improve the quality of drinking water in terms of microbiological and organic indicators.
It is most advisable to use ozone in conjunction with sorption purification using active carbons. Without ozone, in many cases it is impossible to obtain water that complies with SanPiN. The main products of the reaction of ozone with organic substances are compounds such as formaldehyde and acetaldehyde, the content of which is normalized in drinking water at the level of 0.05 and 0.25 mg/l, respectively.
Ozonation is based on the property of ozone to decompose in water with the formation of atomic oxygen, which destroys the enzyme systems of microbial cells and oxidizes some compounds. The amount of ozone required to disinfect drinking water depends on the degree of water contamination and is no more than 0.3 - 0.5 mg/l. Ozone is toxic. The maximum permissible content of this gas in the air of industrial premises is 0.1 g/m 3 .
Water disinfection by ozonation according to sanitary and technical standards is the best, but relatively expensive. A water ozonation installation is a complex and expensive set of mechanisms and equipment. A significant disadvantage of the ozonation unit is the significant consumption of electricity to obtain purified ozone from the air and supply it to the treated water.
Ozone, being a powerful oxidizing agent, can be used not only to disinfect water, but also to decolorize it, as well as to eliminate tastes and odors.
The dose of ozone required for disinfection of clean water does not exceed 1 mg/l, for the oxidation of organic substances during water discoloration - 4 mg/l.
The duration of contact of disinfected water with ozone is approximately 5 minutes.
Water at modern water supply stations undergoes multi-stage purification to remove solid impurities, fibers, colloidal suspensions, microorganisms, and to improve organoleptic properties. The highest quality result is achieved by a combination of two technologies: mechanical filtration and chemical treatment.
Mechanical filtration. The first stage of water treatment allows you to remove visible solid and fibrous inclusions from the medium: sand, rust, etc. During mechanical treatment, water is successively passed through a series of filters with decreasing cell sizes.
Chemical treatment. The technology is used to bring the chemical composition and quality indicators of water to normal. Depending on the initial characteristics of the medium, treatment may include several stages: settling, disinfection, coagulation, softening, clarification, aeration, demineralization, filtration.
Advocacy
At water supply stations, special tanks with an overflow mechanism are installed or reinforced concrete settling tanks are installed at a depth of 4–5 m. The speed of water movement inside the tank is maintained at a minimum level, and the upper layers flow faster than the lower ones. Under such conditions, heavy particles settle to the bottom of the tank and are removed from the system through drainage channels. On average, it takes 5–8 hours for water to settle. During this time, up to 70% of heavy impurities settle.
Disinfection
Purification technology is aimed at removing dangerous microorganisms from water. Disinfection installations are present in all water supply systems without exception. Disinfection of water can be done by irradiation or the addition of chemicals. Despite the advent of modern technologies, the use of chlorine-based disinfectants is preferable. The reason for the popularity of the reagents is the good solubility of chlorine-containing compounds in water, the ability to remain active in a moving environment, and to have a disinfecting effect on the internal walls of the pipeline.
Coagulation
The technology allows you to remove dissolved impurities that are not captured by filter meshes. Polyoxychloride or aluminum sulfate and potassium-aluminum alum are used as coagulants for water. The reagents cause coagulation, that is, the sticking together of organic impurities, large protein molecules, and suspended plankton. Large heavy flakes form in the water, which precipitate, carrying with them organic suspensions and some microorganisms. To speed up the reaction, flocculants are used at treatment stations. Soft water is alkalized with soda or lime to quickly form flakes.
Softening
The content of calcium and magnesium compounds (hardness salts) in water is strictly regulated. To remove impurities, filters with cationic or anionic ion exchange resins are used. When water passes through the load, hardness ions are replaced by hydrogen or sodium, which is safe for human health and the plumbing system. The resin's absorption capacity is restored by backwashing, but the capacity decreases each time. Due to the high cost of materials, this water softening technology is used mainly in local treatment plants.
Lightening
The technique is used to purify surface waters contaminated with fulvic acids, humic acids, and organic impurities. Liquid from such sources often has a characteristic color, taste, and greenish-brown tint. At the first stage, water is sent to the mixing chamber with the addition of a chemical coagulant and a chlorine-containing reagent. Chlorine destroys organic inclusions, and coagulants remove them into sediment.
Aeration
The technology is used to remove ferrous iron, manganese, and other oxidizing impurities from water. With pressure aeration, the liquid is bubbled with an air mixture. Oxygen dissolves in water, oxidizes gases and metal salts, removing them from the environment in the form of sediment or insoluble volatile substances. The aeration column is not completely filled with liquid. An air cushion above the surface of the water softens water hammer and increases the area of contact with air.
Non-pressure aeration requires simpler equipment and is carried out in special shower installations. Inside the chamber, water is sprayed through ejectors to increase the area of contact with air. If the iron content is high, aeration complexes can be supplemented with ozonizing equipment or filter cassettes.
Demineralization
The technology is used to prepare water in industrial water supply systems. Demineralization removes excess iron, calcium, sodium, copper, manganese and other cations and anions from the environment, increasing the service life of process pipelines and equipment. To purify water, reverse osmosis, electrodialysis, distillation or deionization technology is used.
Filtration
Water is filtered by passing through carbon filters, or charcoalization. The sorbent absorbs up to 95% of impurities, both chemical and biological. Until recently, pressed cartridges were used to filter water at waterworks, but their regeneration is a rather expensive process. Modern complexes include a powdered or granular coal charge, which is simply poured into a container. When mixed with water, coal actively removes impurities without changing its state of aggregation. The technology is cheaper but just as effective as block filters. Coal loading removes heavy metals, organics, and surfactants from the water. The technology can be used at treatment plants of any type.
Water becomes potable only after undergoing a full range of treatment measures. Then it goes to city communications for delivery to the consumer.
It is necessary to take into account that even if the water parameters at treatment plants fully comply with sanitary and hygienic standards at the water collection points, its quality may be significantly lower. The reason is old, rusty communications. Water becomes contaminated as it passes through the pipeline. Therefore, the installation of additional filters in apartments, private houses and enterprises remains a pressing issue. Properly selected equipment ensures that water meets regulatory requirements and even makes it healthy.
The third zone covers the area surrounding the source, which influences the formation of water quality in it. The boundaries of the territory of the third zone are determined based on the possibility of contamination of the source with chemicals.
Water quality indicators. The main source of prices is
The tralized domestic and drinking water supply in most regions of the Russian Federation is the surface water of rivers, reservoirs and lakes. The amount of pollutants entering surface water supplies is varied and depends on the profile and volume of industrial and agricultural enterprises located in the catchment area.
The quality of groundwater is quite diverse and depends on the conditions of groundwater recharge, the depth of the aquifer, the composition of the water-bearing rocks, etc.
Water quality indicators are divided into physical, chemical, biological and bacterial. To determine the quality of natural waters, appropriate analyzes are carried out during the most characteristic periods of the year for a given source.
To physical indicators include temperature, transparency (or turbidity), color, smell, taste.
The water temperature of underground sources is characterized by constancy and ranges from 8...12 o C. The water temperature of surface sources varies with the seasons of the year and depends on the influx of groundwater and wastewater into them, fluctuating within 0.1...30 o C. The temperature of drinking water should be within t = 7…10 o C, at t< 7 о C вода плохо очищается, при t >10 o C bacteria multiply in it.
Transparency (or turbidity) is characterized by the presence of suspended substances (particles of sand, clay, silt) in water. The concentration of suspended substances is determined by gravitation.
The maximum permissible content of suspended solids in drinking water should be no more than 1.5 mg/l.
The color of the water is due to the presence of humic substances in the water. The color of water is measured in degrees on the platinum-cobalt scale. For drinking water, the color allowed is no more than 20o.
Tastes and odors of natural waters can be of natural or artificial origin. There are three main tastes of natural water: salty, bitter, sour. Shades of taste sensations made up of the main ones are called tastes.
TO odors of natural origin include earthy, fishy, putrid, marshy, etc. Odors of artificial origin include chlorine, phenolic, the smell of petroleum products, etc.
The intensity and character of the odors and tastes of natural water are determined organoleptically, using the human senses on a five-point scale. Drinking water may have an odor and taste of intensity no higher than 2 points.
TO chemical indicators include: ionic composition, hardness, alkalinity, oxidability, active concentration of hydrogen ions (pH), dry residue (total salt content), as well as the content of dissolved oxygen, sulfates and chlorides, nitrogen-containing compounds, fluorine and iron in water.
Ionic composition, (mg-equiv/l) – natural waters contain various dissolved salts, represented by cations Ca+2, Mg+2, Na+, K+ and anions HCO3 –, SO4 –2, Cl–. Analysis of the ionic composition allows us to identify other chemical indicators.
Water hardness, (mg-equiv/l) is due to the presence of calcium and magnesium salts in it. There are carbonate and non-carbonate hardness.
bone, their sum determines the total hardness of water, Jo = Zhk + Zhk. Carbonate hardness is determined by the carbonate content in water.
sodium and bicarbonate salts of calcium and magnesium. Non-carbonate hardness is caused by calcium and magnesium salts of sulfuric, hydrochloric, silicic and nitric acids.
Water for domestic and drinking purposes must have a total hardness of no more than 7 mEq/l.
Water alkalinity, (mg-equiv/l) – is due to the presence of bicarbonates and salts of weak organic acids in natural water.
The total alkalinity of water is determined by the total content of anions in it: HCO3 –, CO3 –2, OH–.
For drinking water, alkalinity is not limited. The oxidability of water (mg/l) is due to the presence of or-
ganic substances. Oxidability is determined by the amount of oxygen required to oxidize organic substances contained in 1 liter of water. A sharp increase in water oxidation (more than 40 mg/l) indicates its contamination with domestic wastewater.
The active concentration of hydrogen ions in water is an indicator characterizing the degree of its acidity or alkalinity. It is quantitatively characterized by the concentration of hydrogen ions. In practice, the active reaction of water is expressed by the pH value, which is the negative decimal logarithm of the concentration of hydrogen ions: pH = – log [H + ]. The pH value of water is 1…14.
Natural waters are classified according to pH value: into acidic pH< 7; нейтральные рН = 7; щелочные рН > 7.
For drinking purposes, water is considered suitable at pH = 6.5...8.5. The salt content of water is estimated by dry residue (mg/l): pre-
sny100…1000; salted3000…10000; highly salted 10000…50000.
In water from domestic drinking water supply sources, the dry residue should not exceed 1000 mg/l. With greater mineralization of water in the human body, salt deposition is observed.
Dissolved oxygen - enters water when it comes into contact with air. The oxygen content in water depends on temperature and pressure.
IN Artesian waters do not contain dissolved oxygen,
A in surface waters its concentration is significant.
IN In surface waters, the content of dissolved oxygen decreases when there are processes of fermentation or decay of organic residues in the water. A sharp decrease in the content of dissolved oxygen in water indicates its organic pollution. In natural water, the content of dissolved oxygen should not be
less than 4 mg O2 /l.
Sulfates and chlorides - due to their high solubility, are found in all natural waters, usually in the form of sodium, calcium,
zinc and magnesium salts: CaSO4, MgSO4, CaCI2, MgCl2, NaCl.
IN In drinking water, the content of sulfates is recommended not to exceed 500 mg/l, chlorides - up to 350 mg/l.
Nitrogen-containing compounds are present in water in the form of ammonium ions NH4 +, nitrites NO2 – and nitrates NO3 –. Nitrogen-containing pollution indicates contamination of natural waters with domestic wastewater and effluents from chemical plants. The absence of ammonia in the water and at the same time the presence of nitrites and especially nitrates indicate that the pollution of the reservoir occurred a long time ago, and the water
underwent self-purification. At high concentrations of dissolved oxygen in water, all nitrogen compounds are oxidized into NO3 – ions.
The presence of nitrates NO3 - in natural water up to 45 mg/l, ammonium nitrogen NH4 + is considered acceptable.
Fluoride – natural water contains up to 18 ml/l or more. However, the vast majority of surface sources are characterized by a fluoride ion content of up to 0.5 mg/l in water.
Fluorine is a biologically active microelement, the amount of which in drinking water in order to avoid caries and fluorosis should be in the range of 0.7...1.5 mg/l.
Iron - quite often found in water from underground sources, mainly in the form of dissolved ferrous bicarbonate Fe(HCO3)2. In surface waters, iron is found less frequently and is usually in the form of complex compounds, colloids or fine suspended matter. The presence of iron in natural water makes it unsuitable for drinking and industrial purposes.
hydrogen sulfide H2 S.
Bacteriological indicators – it is customary to count the total number of bacteria and the number of E. coli contained in 1 ml of water.
Of particular importance for the sanitary assessment of water is the determination of coliform bacteria. The presence of E. coli indicates water contamination with fecal waste and the possibility of pathogenic bacteria, in particular typhoid bacteria, entering the water.
Bacteriological contaminants are pathogenic (disease-causing) bacteria and viruses that live and develop in water, which can cause typhoid fever,
paratyphoid, dysentery, brucellosis, infectious hepatitis, anthrax, cholera, polio.
There are two indicators of bacteriological water pollution: coli titer and coli index.
Coli titer is the amount of water in ml per one Escherichia coli.
Coli index is the number of E. coli found in 1 liter of water. For drinking water, the coli-titer should be at least 300 ml, and the coli-index should not be more than 3 Escherichia coli. Total bacteria count
No more than 100 is allowed in 1 ml of water.
Schematic diagram of water treatment facilities
ny. Treatment facilities are one of the components of water supply systems and are closely related to its other elements. The location of the treatment plant is determined when choosing a water supply scheme for the facility. Often, treatment plants are located near the water supply source and at a slight distance from the first lift pumping station.
Traditional water treatment technologies provide for water treatment according to classical two-stage or single-stage schemes, based on the use of microfiltration (in cases of the presence of algae in the water in quantities of more than 1000 cells/ml), coagulation followed by settling or clarification in a layer of suspended sediment, rapid filtration or contact clarification and disinfection. The most widespread in water treatment practice are schemes with gravity movement of water.
A two-stage scheme for preparing water for domestic and drinking purposes is shown in Fig. 1.8.1.
The water supplied by the first lift pumping station enters the mixer, where the coagulant solution is introduced and where it is mixed with water. From the mixer, water enters the flocculation chamber and successively passes through a horizontal settling tank and a rapid filter. The clarified water flows into the clean water tank. Chlorine from the chlorination plant is introduced into the pipe supplying water to the tank. The contact with chlorine necessary for disinfection is ensured in a clean water tank. In some cases, chlorine is added to the water twice: before the mixer (primary chlorination) and after the filters (secondary chlorination). If the source water is insufficiently alkaline, enter the mixer simultaneously with the coagulant
lime solution is supplied. To intensify the coagulation processes, a flocculant is introduced in front of the flocculation chamber or filters.
If the source water has a taste and odor, activated carbon is introduced through a dispenser in front of the settling tanks or filters.
Reagents are prepared in special apparatus located in the reagent facilities.
From the pumps of the first |
To the pumps |
||||||||||||||
Rice. 1.8.1. Scheme of treatment facilities for water purification for domestic and drinking purposes: 1 – mixer; 2 – reagent facilities; 3 – flocculation chamber; 4 – settling tank; 5 – filters; 6 – clean water tank; 7 - chlorination
In a one-stage water purification scheme, its clarification is carried out using filters or contact clarifiers. When purifying low-turbidity colored waters, a single-stage scheme is used.
Let us consider in more detail the essence of the main water treatment processes. Coagulation of impurities is the process of enlargement of tiny colloidal particles that occurs as a result of their mutual adhesion under the influence of molecular attraction.
Colloidal particles contained in water have negative charges and are in mutual repulsion, so they do not settle. The added coagulant forms positively charged ions, which promotes the mutual attraction of oppositely charged colloids and leads to the formation of enlarged particles (flakes) in the flocculation chambers.
Aluminum sulfate, ferrous sulfate, and aluminum polyoxychloride are used as coagulants.
The coagulation process is described by the following chemical reactions
Al2 (SO4 )3 → 2Al3+ + 3SO4 2– .
After introducing a coagulant into water, aluminum cations interact with it
Al3+ + 3H2 O =Al(OH)3 ↓+ 3H+ .
Hydrogen cations are bound by bicarbonates present in water:
H+ + HCO3 – → CO2 + H2 O.
add soda to water:
2H+ + CO3 –2 → H2 O + CO2.
The clarification process can be intensified using high-molecular flocculants (praestol, VPK - 402), which are introduced into the water after the mixer.
Thorough mixing of purified water with reagents is carried out in mixers of various designs. Mixing the reagents with water should be quick and carried out within 1–2 minutes. The following types of mixers are used: perforated (Fig. 1.8.2), baffle (Fig. 1.8.3) and vertical (vortex) mixers.
+β h1 |
|||||||||||||||||
2bl |
|||||||||||||||||
Rice. 1.8.2. Hole mixer |
Rice. 1.8.3. Cloisonné mixer |
||||||||||||||||
The perforated type mixer is used at water treatment stations with a capacity of up to 1000 m3/h. It is made in the form of a reinforced concrete tray with vertical partitions installed perpendicular to the movement of water and equipped with holes arranged in several rows.
The baffle mixer is used at water treatment plants with a capacity of no more than 500–600 m3/h. The mixer consists of a tray with three transverse vertical partitions. In the first and third partitions, passages for water are arranged, located in the central part of the partitions. The middle partition has two side passages for water adjacent to
the walls of the tray. Thanks to this design of the mixer, turbulence occurs in the moving water flow, ensuring complete mixing of the reagent with water.
At stations where water is treated with lime milk, the use of perforated and baffle mixers is not recommended, since the speed of water movement in these mixers does not ensure the maintenance of lime particles in suspension, which leads to
leads to their deposition in front of the partitions. |
||||||||||
At water treatment plants the most |
||||||||||
verticals have found greater use |
||||||||||
nal mixers (Fig. 1.8.4). Mixer |
||||||||||
this type can be square or |
||||||||||
circular in plan, with pyramids- |
||||||||||
distant or conical bottom. |
||||||||||
In the baffle chambers the flakes |
||||||||||
education arrange a series of partitions |
||||||||||
docks that force the water to change |
Reagents |
|||||||||
the direction of its movement either in |
||||||||||
vertical or horizontal |
||||||||||
plane, which provides the necessary |
||||||||||
stirring the water gently. |
Rice. 1.8.4. Vertical (vortex) |
|||||||||
For mixing water and providing |
||||||||||
roar) mixer: 1 – feed |
||||||||||
more complete agglomeration |
source water; 2 – water drainage |
|||||||||
small flakes of coagulant into large ones |
from the mixer |
|||||||||
serve as flocculation chambers. Their |
||||||||||
installation is necessary before horizontal and vertical settling tanks. For horizontal settling tanks, the following types of flocculation chambers should be installed: baffled, vortex, built-in with a layer of suspended sediment and bladed; for vertical settling tanks - whirlpool ones.
Removal of suspended substances from water (clarification) is carried out by settling it in settling tanks. Depending on the direction of water movement, sedimentation tanks are horizontal, radial and vertical.
A horizontal settling tank (Fig. 1.8.5) is a rectangular reinforced concrete tank. In its lower part there is a volume for the accumulation of sediment, which is removed through the channel. For more efficient removal of sediment, the bottom of the settling tank is made with a slope. The treated water enters through the distribution
flume (or flooded weir). After passing through the sump, the water is collected by a tray or perforated (holey) pipe. Recently, settling tanks have been used with dispersed collection of clarified water, arranging special gutters or perforated pipes in their upper part, which allows increasing the productivity of settling tanks. Horizontal settling tanks are used at treatment plants with a capacity of more than 30,000 m3/day.
A type of horizontal sedimentation tanks are radial sedimentation tanks, which have a mechanism for raking sediment into a pit located in the center of the structure. The sediment is pumped out from the pit. The design of radial settling tanks is more complex than horizontal ones. They are used to clarify waters with a high content of suspended solids (more than 2 g/l) and in recycling water supply systems.
Vertical sedimentation tanks (Fig. 1.8.6) are round or square in plan and have a conical or pyramidal bottom for sediment accumulation. These settling tanks are used subject to preliminary coagulation of water. The flocculation chamber, mainly a whirlpool, is located in the center of the structure. Water clarification occurs during its upward movement. Clarified water is collected in ring and radial trays. Sludge from vertical settling tanks is discharged under hydrostatic water pressure without shutting down the structure. Vertical settling tanks are mainly used at flow rates of 3000 m3/day.
Clarifiers with a suspended layer of sediment are intended for preliminary clarification of water before filtration and only under the condition of preliminary coagulation.
Suspended sediment clarifiers can be of different types. One of the most common is a corridor-type clarifier (Fig. 1.8.7), which is a rectangular tank divided into three sections. The two outer sections are working clarifier chambers, and the middle section serves as a sediment compactor. The clarified water is supplied at the bottom of the clarifier through perforated pipes and is evenly distributed over the area of the clarifier. Then it passes through the suspended layer of sediment, is clarified and is discharged to filters through a perforated tray or pipe located at some distance above the surface of the suspended layer.
To deeply clarify water, filters are used that are capable of capturing almost all suspended matter from it. Exist like this
the same filters for partial water purification. Depending on the nature and type of filter material, the following types of filters are distinguished: granular (filter layer - quartz sand, anthracite, expanded clay, burnt rock, granodiarite, expanded polystyrene, etc.); mesh (filter layer - mesh with a cell size of 20–60 microns); fabric (filter layer - cotton, linen, cloth, glass or nylon fabrics); alluvial (filter layer - wood flour, diatomaceous earth, asbestos chips and other materials, washed in the form of a thin layer on a frame made of porous ceramics, metal mesh or synthetic fabric).
Rice. 1.8.5. Horizontal settling tank: 1 – source water supply; 2 – removal of purified water; 3 – sediment removal; 4 – distribution pockets; 5 – distribution grids; 6 – sediment accumulation zone;
7 – settling zone
Rice. 1.8.6. Vertical settling tank: 1 – flocculation chamber; 2 – Rochelle wheel with attachments; 3 – damper; 4 – supply of source water (from the mixer); 5 – collection chute of a vertical settling tank; 6 – pipe for removing sediment from a vertical settling tank; 7 – bend
water from the sump
Granular filters are used to purify drinking water and industrial water from fine suspended matter and colloids; mesh - for retaining coarse suspended and floating particles; fabric - for the purification of low-turbidity waters at low-capacity stations.
Granular filters are used to purify water in public water supplies. The most important characteristic of filter operation is the filtration speed, depending on which filters are divided into slow (0.1–0.2), fast (5.5–12) and ultra-fast.
Rice. 1.8.7. Corridor clarifier with suspended sediment with a vertical sediment compactor: 1 – clarifier corridors; 2 – sediment compactor; 3 – supply of source water; 4 – collection pockets for drainage of clarified water; 5 – removal of sediment from the sediment compactor; 6 – removal of clarified water from the sediment compactor; 7 – sediment receiving
windows with visors
The most widely used are rapid filters, in which pre-coagulated water is clarified (Fig. 1.8.8).
Water entering rapid filters after a settling tank or clarifier should not contain suspended solids of more than 12–25 mg/l, and after filtration, the turbidity of the water should not exceed 1.5 mg/l
Contact clarifiers are similar in design to fast filters and are a type of them. Water clarification, based on the phenomenon of contact coagulation, occurs when it moves from bottom to top. The coagulant is introduced into the treated water immediately before it is filtered through a sand bed. In a short time before the start of filtration, only the smallest flakes of suspended matter are formed. The further coagulation process occurs on the loading grains, to which the previously formed tiny flakes stick. This process, called contact coagulation, occurs faster than conventional bulk coagulation and requires less coagulant. Contact brighteners are washed by
Water disinfection. In modern treatment facilities, water is disinfected in all cases where the source of water supply is unreliable from a sanitary point of view. Disinfection can be carried out by chlorination, ozonation and bactericidal irradiation.
Chlorination of water. The chlorination method is the most common method of water disinfection. Typically, liquid or gaseous chlorine is used for chlorination. Chlorine has a high disinfecting ability, is relatively stable and remains active for a long time. It is easy to dose and control. Chlorine acts on organic substances, oxidizing them, and on bacteria, which die as a result of oxidation of substances that make up the protoplasm of cells. The disadvantage of water disinfection with chlorine is the formation of toxic volatile organohalogen compounds.
One of the promising ways to chlorinate water is to use sodium hypochlorite(NaClO), obtained by electrolysis of a 2–4% solution of table salt.
Chlorine dioxide (ClO2) reduces the possibility of formation of by-product organochlorine compounds. The bactericidal power of chlorine dioxide is higher than that of chlorine. Chlorine dioxide is especially effective in disinfecting water with a high content of organic substances and ammonium salts.
The residual concentration of chlorine in drinking water should not exceed 0.3–0.5 mg/l
The interaction of chlorine with water is carried out in contact tanks. The duration of contact of chlorine with water before it reaches consumers must be at least 0.5 hours.
Germicidal irradiation. The bactericidal property of ultraviolet rays (UV) is due to the effect on cellular metabolism and especially on the enzyme systems of the bacterial cell; in addition, under the influence of UV radiation, photochemical reactions occur in the structure of DNA and RNA molecules, leading to their irreversible damage. UV rays destroy not only vegetative but also spore bacteria, while chlorine affects only vegetative bacteria. The advantages of UV radiation include the absence of any effect on the chemical composition of water.
To disinfect water in this way, it is passed through an installation consisting of a number of special chambers, inside of which mercury-quartz lamps are placed, enclosed in quartz casings. Mercury-quartz lamps emit ultraviolet radiation. The productivity of such an installation, depending on the number of chambers, is 30…150 m3/h.
Operating costs for water disinfection by irradiation and chlorination are approximately the same.
However, it should be noted that with bactericidal irradiation of water it is difficult to control the disinfection effect, while with chlorination this control is carried out quite simply by the presence of residual chlorine in the water. In addition, this method cannot be used to disinfect water with increased turbidity and color.
Ozonation of water. Ozone is used for the purpose of deep water purification and oxidation of specific organic pollutants of anthropogenic origin (phenols, petroleum products, surfactants, amines, etc.). Ozone allows you to improve the course of coagulation processes, reduce the dose of chlorine and coagulant, reduce the concentration
tion of LHS, improve the quality of drinking water in terms of microbiological and organic indicators.
It is most advisable to use ozone in conjunction with sorption purification using active carbons. Without ozone, in many cases it is impossible to obtain water that complies with SanPiN. The main products of the reaction of ozone with organic substances are compounds such as formaldehyde and acetaldehyde, the content of which is normalized in drinking water at the level of 0.05 and 0.25 mg/l, respectively.
Ozonation is based on the property of ozone to decompose in water with the formation of atomic oxygen, which destroys the enzyme systems of microbial cells and oxidizes some compounds. The amount of ozone required to disinfect drinking water depends on the degree of water contamination and is no more than 0.3–0.5 mg/l. Ozone is toxic. The maximum permissible content of this gas in the air of industrial premises is 0.1 g/m3.
Water disinfection by ozonation according to sanitary and technical standards is the best, but relatively expensive. A water ozonation installation is a complex and expensive set of mechanisms and equipment. A significant disadvantage of the ozonation unit is the significant consumption of electricity to obtain purified ozone from the air and supply it to the treated water.
Ozone, being a powerful oxidizing agent, can be used not only to disinfect water, but also to decolorize it, as well as to eliminate tastes and odors.
The dose of ozone required for disinfection of clean water does not exceed 1 mg/l, for the oxidation of organic substances during water discoloration - 4 mg/l.
The duration of contact of disinfected water with ozone is approximately 5 minutes.
