When we turn on a tap with cold or hot water in the morning, none of us thinks that a hundred years ago, for the vast majority of the population of our planet, this level of comfort was absolutely inaccessible.
Only wealthy owners of comfortable apartments in big cities could afford to use water supply and sewerage.
The vast majority of the population, like thousands of years ago, was forced to carry water in buckets from the nearest well, stream, or, at best, from a standpipe.
The twentieth century radically changed the way people live. This was a century of revolutionary changes in many spheres of life, including the public sector.
Water supply and sewerage came to literally every home and from a luxury item became an essential necessity of both urban and rural life. However, not all residents of city apartments understand how the water supply system of their home works, where water comes from into the house and where it goes from the sink, bathtub or toilet.
Water purification
We all know that today drinking water collected from a river or lake without first filtering and boiling it is dangerous to health. But the water that fills our water pipes is usually drawn from the nearest large body of water. Of course, it first goes through a complex purification system at a water intake station. 
Water purification is carried out in several stages. First, river water is pumped from the river into the station's storage tank using powerful pumps. There it passes through several filter pipes with grates, cleaning itself from large debris - wood fragments, algae and other contaminants.
Then small particles of sand, silt, and pieces of algae should be caught and deposited. To do this, water is passed through several filters filled first with coarse gravel, then with finer ones. The water is purified from the smallest particles of dirt by passing through a filter made of washed river sand.
The next stage is disinfection, which is performed either by adding a disinfectant to the water or by ultraviolet irradiation. The second method is more modern and completely harmless to human health. However, in some regions, water is still disinfected by chlorination.
City water supply
The water supply system of a modern large city is a complex engineering structure consisting of several main lines and numerous branches suitable for individual houses and apartments.
In the past, a water tower with a reservoir located at a high altitude was used to keep water flowing through pipes. Water was pumped into a reservoir, and from there it flowed through pipes into houses and apartments.
In a modern city, this system would not be able to meet the needs of even one microdistrict. And how tall would the tower be required to create enough pressure to supply water to the 25th floor? Therefore, the necessary pressure in the pipes is created by powerful electric pumps located in the most important nodes of the water supply network. 
True, in the event of a major power failure, an urban area may be left not only without electricity, but also without water. To avoid this, pumping stations are equipped with independent or backup power sources.
In order to reach your home, water from the river must overcome a filter system, pass through several powerful pumps and through a labyrinth of pipes. And if it is hot water, then through the boiler of the boiler station that provides heat to your area.
Sewer system
Bringing water to every house and apartment is only half the problem. When you turn on the tap to wash your face or wash dishes, the used water flows into the sink hole. But where does it go afterwards?
Wastewater from the kitchen sink, bathtub, shower and toilet drains enters the sewer pipe, and from there goes into the central sewer main sewer. Wastewater from many apartments and houses is collected there.
With the help of special sewage pumps designed for pumping dirty, clogged water, wastewater is removed from residential neighborhoods and industrial enterprises.
Unfortunately, under no circumstances should you simply dump wastewater into the river. They contain many harmful and toxic contaminants, which, once in the river, will quickly poison all living things in it, turning it into the same sewer system, only on a larger scale. Therefore, wastewater must be treated.
Each city has a special treatment station (and in large cities there are usually several of them), where the water is completely freed from dirt and becomes suitable for discharge into the river or for reuse.
Cleaning is carried out, as in the case of tap water, in several stages. But even purified water is not suitable for drinking - it is discharged into the irrigation systems of nearby agricultural enterprises. 
In order for us to be able to use the things we have become familiar with since childhood – a water tap and a toilet – public utilities do a great job every day. Don’t forget about this and don’t waste water, because it is our wealth!
Natalia Ipatova
For St. Petersburg, the Neva is the only source of drinking water. The river originates in Lake Ladoga and is a natural drainage route to the city. Therefore, the condition of the water in Ladoga is extremely important.
98% of the drinking water supplied to the city comes from the Neva. Another 2% is groundwater, which is used to supply water to suburbs, mainly in the southeast.
The Neva comes to the city already polluted. On the way from Ladoga to St. Petersburg, it receives untreated wastewater from other populated areas, runoff from agricultural fields and discharges from enterprises.
The Neva comes to the city already polluted. On the way from Ladoga to St. Petersburg, it receives untreated wastewater from other populated areas, runoff from agricultural fields and discharges from enterprises. Moreover, the Neva is the final link of the entire unified water system of the North-West (it includes Lake Onega, Lake Ilmen, Lake Ladoga with their drainage basins). Therefore, the water utility always says that it is impossible to restore order only in “its” area. Pollution has no boundaries, and the issue of wastewater treatment in the Leningrad region, Karelia and other regions of the North-West must be urgently resolved. That's what we do.
Is tap water really “drinkable”?
This may surprise some, but drinking water is first and foremost water from centralized drinking water supply systems, water at the outlet of water supply stations, from street pumps and reservoirs. And only then – bottled
non-mineral water. In other words, the water that comes from the tap is officially
Suitable for drinking without prior filtration and boiling.
Corrosion products may appear in drinking water. However, in such quantities they are not dangerous to the health of citizens
Natalia Ipatova
Director of the Department of Information and Public Relations
State Unitary Enterprise "Vodokanal of St. Petersburg"
Drinking water in St. Petersburg is guaranteed to be safe and harmless. This means that drinking water from the tap will not cause any harm to your health.
Those rare cases when deviations from standard values are recorded in tap water are associated exclusively with the iron content in it. The fact is that Neva water is naturally soft. Therefore, it is suitable for preparing drinks and using at home. Thus, washing machines and dishwashers in the homes of St. Petersburg residents do not require special water softeners. But it is the natural softness of our water that makes it corrosive. During the period of active development of Leningrad (1970s-1980s – Author’s note) water pipes were made of steel, which, unfortunately, is very susceptible to corrosion processes. Because of this, corrosion products can sometimes appear in drinking water. However, in such quantities they are not dangerous to the health of city residents and only affect the taste properties of the water.
On this issue, the opinions of Vodokanal and environmental organizations differ somewhat:
Healthy people, of course, can drink tap water and nothing will happen to them. But asthmatics or allergy sufferers may already have problems
Yuri Shevchuk
Chairman of the North-West interregional public environmental organization "Green Cross"
It is important to understand that Vodokanal works with standards, and, therefore, focuses on healthy people. They, of course, can drink tap water and nothing will happen to them. But asthmatics or allergy sufferers may already have problems. These are the people who most often complain about contaminated water.
In general, water quality is assessed by three indicators: bacteriological composition, chemical and mineral. There are almost no bacteria in drinking water in St. Petersburg (which is why, by the way, people rarely get hepatitis here). In terms of chemical indicators, the situation is already twofold: Vodokonal works well, the water is completely purified from harmful chemical elements. However, passing through urban, often outdated networks, it becomes polluted again. If we take an old pipe and cut it, we will find a greenish coating inside (these are microorganisms), as well as rust. You can get rid of them only with the help of local filters: either in the apartment or throughout the house. But this is a subjective reason for poor water quality.
The water in Lake Ladoga is ultra-fresh, it contains few mineral compounds that are so necessary for humans
And the objective reason and the saddest characteristic of St. Petersburg drinking water is its mineral composition. The water in Lake Ladoga is ultra-fresh, it contains few mineral compounds that are so necessary for humans. Therefore, city residents are often prescribed to take magnesium and calcium - bones become very fragile due to such water.
How does Vodokanal combat pollution?
Natalia Ipatova
Director of the Department of Information and Public Relations
State Unitary Enterprise "Vodokanal of St. Petersburg"
The Neva is a navigable river, and Vodokanal is certainly obliged to take this into account. Therefore, several years ago, all water stations in St. Petersburg installed dosing units for powdered activated carbon. They purify water from petroleum products. The same installations are used during seasonal deteriorations in water quality in the Neva, for example, during floods.
In addition, Vodokanal has a system for early detection of pollution in the river. It includes a biomonitoring system using crayfish. The crayfish's workplace is an aquarium, into which Neva water is supplied from the water intake, which has not undergone treatment. Special sensors are attached to the cancer's shell, which record the cancer's heart rate and stress index online. The system is based on the fact that, if hazardous substances enter the Neva water, the crayfish reacts instantly: its heart begins to beat much faster, and the corresponding signal is immediately sent to dispatchers.
There is also an early detection system for oil products in the Neva. Before the Neva enters the city, in front of the first water intake of Vodokanal, special equipment is installed on the bridge - the so-called “crabs”. These are devices that measure the thickness of the oil film on the surface of the water and the concentration of oil products in it. All received data is transmitted to the control room - and then they decide whether to turn on the dosing units for activated powdered carbon or not.
Foreign experience
Piterstory selected several cities where the purity of tap water is almost a source of pride, and buying it in plastic bottles is considered bad taste.
Stockholm
Sweden has many natural lakes, the largest of which are Vänern, Vättern and Mälaren. Stockholm is located on the east coast of the latter. Firstly, the water in the lake itself is perfectly clean, a sure indicator of which is the salmon and trout that live there.
Secondly, in Sweden, quite tasty drinking water is obtained by treating wastewater.
Helsinki
Water comes to the capital of Finland from Lake Päijänne through a 120-kilometer-long tunnel. At the initial stage, it passes through a water intake, then enters through a tunnel to water treatment complexes, is ozonized, undergoes normalization of the acid-base balance, is filtered again and, finally, purified by an ultraviolet disinfection system.
Vein
Every day Vienna receives 400,000 cubic meters of water through two pipelines from mountain springs in the areas of Schneeberg, Rax, Schneealpe and Hochschwab. Therefore, you can safely drink tap water, especially since it is served with coffee in any establishment.
And the water tower in the style of “industrial historicism” remained in Vienna solely as a monument.
Zurich
Not only in Zurich, but also in any other Swiss city, the water is crystal clear for a very obvious reason - it comes from the mountains. In addition, the country has abandoned the use of pesticides in agriculture. Well, the Romandian Consumer Federation claims that tap water in Switzerland is 1000 times more environmentally friendly and 500 times cheaper than bottled water.
Photo: s-pb.in
Topics of the day
Where does the water in our taps come from, is it possible to drink it without boiling, who controls the quality of the water - St. Petersburg.ru found out.
We drink Neva
Just like 300 years ago, residents of St. Petersburg now drink water from the Neva. Only earlier water was drawn from the river directly or bought from water carriers, but now we open the water tap at home. The city's permanent water supply system is already 155 years old. At the time of its creation, it was private, supplied only a small part of the left bank of the Neva in the area of the beginning of the current Chernyshevsky Avenue, and the water taken directly from the river was not purified at all. Today, the city's water supply network stretches for almost 7 thousand km, operates without interruption 24 hours a day, 365 days a year, and this water can be drunk directly from the tap without fear of contracting typhoid or cholera. By the way, over a period of 155 years, the central water supply system of St. Petersburg did not work for only two days - January 25 and 26, 1942, when the electricity was completely turned off in besieged Leningrad.
Sustainable system
Today's water supply system of St. Petersburg is a complex of interconnected engineering structures that ensure an uninterrupted supply of drinking water to consumers. The complex includes 9 water supply stations, 198 booster pumping stations, and a pipeline network with a length of 6938 km.
About 98% of the water is taken from the Neva, which is processed at the 5 largest waterworks: the Main Waterworks Station (GVS), the Northern Waterworks Station (SWS), the South Waterworks Station (SWS), the Volkovskaya Waterworks Station (VWS), Water Treatment Plants ( VOS) Kolpino.
The entire city is divided into three water supply zones: South, North and Central. The southern zone provides water supply to the Moskovsky, Frunzensky, Krasnoselsky, Kirovsky, Kolpinsky and Pushkinsky districts, as well as the left bank part of the Nevsky district and part of the Petrodvortsovy district. The central system provides water supply to the Central, Admiralteysky, Vasileostrovsky and Petrogradsky districts, parts of the Moscow and Kirovsky districts. The northern system is responsible for the Vyborg, Kalininsky, Krasnogvardeisky, Kurortny, Primorsky districts and the right bank part of the Nevsky district.
Bleach is a myth
Contrary to popular belief, the use of liquid chlorine to disinfect drinking water in St. Petersburg has been completely stopped since June 2009. The reason for the refusal was not the harmful effects of chlorine on the body, but the danger when transporting chlorine cylinders along city streets. Instead, sodium hypochlorite is now used; its disinfecting effect is based on the fact that when dissolved in water, just like chlorine, it forms hypochlorous acid, which has a direct oxidizing and disinfecting effect. At waterworks in St. Petersburg, after disinfecting drinking water with sodium hypochlorite, ultraviolet water treatment is also used. Our city became the very first metropolis in the world where a two-stage drinking water purification technology was used - chemical and physical. New York became the second such city in the world.
Drinking water quality
At all city water intakes, to monitor the state of water in the Neva River, along with instrument monitoring, a biomonitoring system developed by scientists from the St. Petersburg Research Center for Environmental Safety of the Russian Academy of Sciences is used. The condition of the water in the Neva is controlled by crayfish. Crayfish have been “working” at Vodokanal since December 2005. Their jobs are at all city water intakes. At the South-Western wastewater treatment plants, crayfish also help control the quality of wastewater treatment: in the winter, these are river crayfish, and in the summer, they are Australian crayfish (more heat-loving). And snails help monitor the composition of the flue gases coming out of the sludge incineration plant at the South-West Wastewater Treatment Plant. All animal bioindicators do not replace methods of instrumental and laboratory control, but complement them.
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Many people are probably familiar with the situation when, trying to answer a seemingly simple question, it becomes clear that it is quite difficult to formulate an exact answer and thoroughly explain some of the elementary nuances of the matter. The same rule applies to a simple question: where does the water in the tap come from? At first glance, the question is completely simple and even childish, but in reality it turns out that not many can describe in detail the entire technological process that precedes the moment when water, already purified and prepared, flows out of the tap.
Often, the water in the tap comes from a regular reservoir, having previously been purified.
Often, while relaxing on bodies of water, few people think about what might come from this particular source, where on holidays they manage to escape with their friends. Even knowing this, few people would think of quenching their thirst with this water, consumed daily from the tap, but, of course, purified.
To answer the question: where does water come from, it is worth following the entire process of its movement, starting from surface water, such as reservoirs and other bodies of water, and ending with the moment when, ready for consumption, the water is sent through pipelines to residential buildings.
So, first the water goes to a water treatment station, where it is purified to a potable state.
This process consists of several stages, during each of which the water is stripped of a specific type of harmful contaminant.
At a water treatment plant, water is purified to a potable state.
At the initial stage, the water undergoes mechanical purification and is cleared of coarse debris, such as large organic matter, sand, silt, etc. Then, by adding chemical reagents to the water that bind and precipitate microscopic impurities, the water is purified a second time. To purify water, sorption agents are also actively used, capable of absorbing a wide range of pollutants, which also include heavy metals and many bacteria. Ion exchange materials are used to soften water. Before reaching the consumer, tap water must undergo a deterministic disinfection process.
It is worth adding that the methods and level of cleaning procedures directly depend on the technological capabilities of the water treatment plant and on the degree of contamination of the incoming water. Probably, many are familiar with the situation when, tasting water in a new place, they feel a new taste and a completely different quality, different from those to which they are accustomed. The specific taste and smell of water are characteristic of each individual region, city, and even districts of one city. The main reason for this difference is the source of water supply, treatment methods at water treatment plants and the condition of the water distribution system pipes.
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Traditional and modern methods
Schematic diagram of water purification.
If we consider the water treatment technologies of domestic stations, then, of course, the situation here is not very optimistic, since, as always, there are not enough funds for the introduction of modern technologies, so the process of water disinfection is still carried out through chlorination. And everyone knows from school days how harmful the ingestion of this reagent is to health. The unpleasant smell and specific taste of water that has gone through chlorination are just “flowers”. Doctors have long been aware of all the insidious consequences of consuming chlorinated water, therefore, knowing where the water comes from and what unsafe path it takes, doctors recommend refusing to consume tap water as drinking water, and, as a last resort, using additional filters for purification.
Of course, in more developed countries, the process of water disinfection looks completely different. More effective and harmless methods are actively used there, such as ultraviolet treatment and ozonation. And in Belarus, water is additionally processed for iron removal by preliminary oxidation of iron-containing fragments and their further neutralization and filtering.
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Underground tanks
Scheme of water disinfection using a UV filter.
Recently, water from underground sources has become increasingly popular, which is where the tap water comes from in some regions. The main and undeniable advantage of groundwater, of course, is the absence of organic matter and microorganisms, which are found in abundance in surface waters. This advantage eliminates the need for chlorination of water and makes it several orders of magnitude safer due to the lack of chlorine content. The only drawback of groundwater is the increased content of hardness salts, minerals, heavy metals and inorganic impurities in its composition. Therefore, at water treatment plants, a procedure is carried out to purify water from these compounds to the existing standards of minimum permissible concentrations (MAC).
After completing the entire technological purification process in laboratory conditions, the water is tested for the content of harmful impurities, which must correspond to their maximum permissible concentrations (that is, the presence of pollutants is allowed, but in strictly defined concentrations).
Perhaps everyone knows that the huge boiler-cooling towers and striped chimneys emitting smoke, which are visible from anywhere in the city, belong to the thermal power plant. Moreover, many people know that these colossuses provide our homes with light, heating and hot water. But what exactly is the process of heat generation and how cooling tower columns are involved in it is a rather confusing question.
Consumables
The entire process of CHP operation begins with water preparation. Since it is used here as the main coolant, it requires preliminary cleaning before entering the steam boiler, where the main metamorphoses will occur with it. To prevent scale on the walls of boilers, the water is first softened - its hardness sometimes needs to be reduced by 4000 times, and it also needs to be removed from various impurities and suspended matter.
As a rule, gas, coal or peat are used as fuel for heating water boilers at various power plants. The combustion of these materials releases thermal energy, which is used at the station to operate the entire power unit. Coal is ground before use, and the incoming gas is purified from mechanical impurities, hydrogen sulfide and carbon dioxide.
Steam production
The huge steam boiler in the turbine hall - the height of a 9-story building is not the limit - can be called the heart of the thermal power plant. It is powered by prepared fuel, releasing a huge amount of energy. Under its force, the water in the boiler turns into steam with an outlet temperature of almost 600 degrees. Under the pressure of this steam, the generator blades rotate, resulting in the creation of electricity.
The thermal power plant also produces thermal energy intended for heating and hot water supply to the region and city. For this purpose, there are selections on the turbine that remove part of the heated steam before it reaches the condenser. The exhausted steam is transferred to a network heater, which acts as a heat exchanger.
Heating network
Once in the tubes of network heaters, the water is heated and transferred through underground pipelines further into the heating network due to pumps driving the water through the pipes. Heating networks, as a rule, carry water at 70-150 degrees - it all depends on the temperature outside: the lower the degree outside, the hotter the coolant.
The central heating point (CHS) becomes the transfer point for the coolant. It serves an entire system of buildings, an enterprise or a microdistrict at once. This is a kind of intermediary between the object that creates heat and the direct consumer. If water in a boiler room is heated due to fuel combustion, then the central heating station works with an already heated coolant.
Hot water recipe
The supply of coolant ends at the entrance to the central heating substation or ITP (individual heating substation) - thus, the coolant is transferred for further actions into the hands of the HOA or other management company. It is at the heating point that the hot water that we are used to dealing with is created - the water coming here from the thermal power plant heats clean cold water from the water intakes in the heat exchanger and turns it into the very hot water that flows in our taps.
After heating the building and room, this water gradually cools, its temperature drops to 40-70 degrees. Part of this water is mixed with the coolant and supplied to our hot water taps. The road to the other part is back to the station, here the cooled water will be warmed by network heat exchangers.
What are cooling towers for?
The majestic and massive towers, called cooling towers, are not the reactors and centers of action in a thermal power plant and actually play a supporting role. Surprisingly, they are used in heating plants to cool water. But why let water that is constantly heated cool?
Cooling towers use the second part of the “return”, which has gone through a heating-cooling cycle. But its temperature is still quite high: 50 degrees is too high for further use. The water that has been in cooling towers is used to cool the condensers of steam turbines. This is necessary so that the steam that has passed through the steam turbine can enter the condenser and condense on the cold pipes inside it. These pipes are precisely cooled by the water that has passed through the cooling tower, the temperature of which is now about 20 degrees. If they are not cooled, then there will be no steam flow through the turbine, and then it will not be able to work. The condenser will again turn the steam into water, which will be recirculated.