Advanced technologies: how drinking water is purified in Moscow
On 13 October, Sergei Sobyanin visited the Rublevskaya water treatment plant, which has been equipped with an additional water filtration unit using the latest water purifying technology based on ozone-sorption. The most advanced technologies have made water in Moscow flats purer, more transparent, and odourless.
Nearly 64 percent of Moscow water is being purified through ozone filtration, ozone-sorption, and membrane filtration. The quality of the drinking water in Moscow will continue to improve.
Moscow has four water treatment plants: Rublevskaya, Western, Northern, and Eastern. It takes eight to 12 hours to bring water from the intake to the tap in a flat. Chief Engineer of Mosvodokanal (municipal water and wastewater utility) Water Supply Department, Alexei Babayev, knows how to make water from a reservoir drinkable. He talked about this with mos.ru.
Eleven reservoirs and pumping stations
Question: What is the water treatment process like?
Alexei Babayev: There are four water treatment plants in Moscow that treat surface water and make it drinkable. The total length of the city system is about 13,000 kilometres of varied-diameter pipeline. In the city there are 11 regulatory nodes — reservoirs and pumping stations. Storage tanks are used to hold water from the treatment plants. Then pumps supply it to the city system and then to Moscow flats.
Question: How long does it take from the water intake to the time it enters a flat?
Alexei Babayev: The whole cycle is between eight and twelve hours.
Question: Where does Moscow get its water?
Alexei Babayev: Surface water sources account for 99 percent of Moscow’s water. These are the Volzhsky and Moskvoretsky water sources. The Moskvoretsky source consists of the Moskva River and a few reservoirs including the Istrinskoye, Mozhaiskoye, Ruzskoye, and Ozerninskoye. Also, there is a backup Vazuzskaya hydraulic system. It is used in dry years when there is not enough water in our reservoirs. Through a system of canals and pumping stations, we can pump water to the Moskvoretsky slope. Water is supplied from the Volga River and pumped in via the Moscow Canal — it is a cascade of pumping stations. Our intakes are located at Uchinskoye and Klyazminskoye reservoirs. The Northern and Eastern water treatment plants use water from the Volga River; the Western and Rublevskaya plants use water from the Moskva River.
Question: And the remaining one percent — what sources are these?
Alexei Babayev: The remaining one percent includes groundwater sources, these are areas outside the MKAD (Moscow Ring Road) and the TiNAO (Troitsky and Novomoskovsky administrative areas). One part of the TiNAO area, which is closer to the old Moscow borders, is supplied with water from the Western Water Treatment Plant, while the other part, located farther on, from groundwater sources, i.e., wells.
The Troitsky and Novomoskovsky administrative areas are new areas of development for us and they use groundwater sources. Each of them has its own issues and challenges. At some places deferrization or desalinization are required; at others we have to remove heavy metals salts with reverse osmosis.
Moscow water is of medium hardness
Question: How much does water differ from one district to another? Can we say that somewhere it is softer, somewhere it is harder, even maybe tastier?
Alexei Babayev: In principle, all of the city’s water is of medium hardness. It changes slightly depending on the season. In the spring, reservoirs and intake facilities are filled with soft melt water, so in this period the hardness indicator is lower. During the water treatment process the indicator is not changed, that is, it is so-called natural water hardness.
As for the taste, a lot depends on the person. Some people can distinguish hints of variation in the smell, or taste; some say that all water is the same, no matter where they tasted it.
Question: How do hardness values vary throughout the year?
Alexei Babayev: Of course, there is a range — from 3 to 5.5 degrees of water hardness. For example, in winter it is about 5.5 while 7 degrees is considered to be the norm. In the spring the indicator is about 3 degrees of hardness. But consumers can hardly taste any difference.
Question: What other effects can the season have on water?
Alexei Babayev: In the winter and spring, the snow that melts around the reservoirs can include various harmful substances that may result, for instance, in an unpleasant odour. Autumn rains and high water can also pollute water sources. However, Muscovites are securely protected at all times; pure drinking water comes from their taps. The water treatment plants adjust the treatment mode of the water: amount of chemicals, filtration speed, the facilities undergo more frequent cleaning.
Moreover, there is a plankton blooming period — mass growth of phytoplankton in the reservoirs. This usually happens in the summer when the water gets warm. Then we introduce special water treatment processes, and adjust the amount of chemicals. But all of this does not affect the quality of the drinking water which comes from the plant. Year-round, the water meets sanitary standards.
Pleasant taste and no odour
Question: In recent years, the water quality in Moscow has improved. What is the reason?
Alexei Babayev: Yes, this is true. Since 2002, modern facilities have been built in the city, in other words, our traditional settling and filtration of water are supplemented with tertiary treatment. This includes the ozone and an absorbent coal treatment phase. The first ozone-sorption unit was launched at the Rublevskaya Water Treatment Plant in 2002. Since then, two more units have been built at the Western plant, and another big unit, at the Rublevskaya Water Treatment Plant. And now, a third powerful water filtration unit will run at the Rublevskaya plant using the latest ozone-sorption purifying technology.
Ozone-sorption technology almost completely purifies water from organic contaminants. The water tastes good; it has no colour or odour. So, indeed, we can say that over the past 15 years, the water quality in Moscow has been improving. This is absolutely safe water, which is suitable for human consumption, for drinking and household purposes every day.
Question: How does ozone help purify water? How does this technology work?
Alexei Babayev: Ozone is a very strong oxidant. We are all familiar with the smell of ozone during thunderstorms: if it is close, we feel the smell of freshness. At a water treatment plant ozone is produced by special equipment, where the oxygen from the air we breathe is converted into ozone through an electric discharge. Once mixed with the water, ozone oxidizes all the suspended solids that need to be removed. Coal filtration filters suspended solids and sends them down to settle, a special scraper removes the sediment. Currently, this is the most efficient and economically feasible technology.
Question: Does this technology mean faster water purification?
Alexei Babayev: No, it does not mean faster purification, but an additional purification step. Water, purified with modern technologies, is somewhat different: it almost has no seasonal odours or taste.
At the level of Paris and London
Question: How often is the quality of drinking water tested in Moscow?
Alexei Babayev: It is a continuous process. Every day samples are collected at water sources, in the Moskva River, at water intake stations, at water treatment plants during the filtration process as well as in the municipal water distribution system. In total, there are 250 monitoring points.
Question: Is it possible to check at home whether water from the tap is clean or not?
Alexei Babayev: Most likely, only visually: you can pour a glass of water and see if it’s transparent or not, you can taste it, smell it for any odour, etc. A lab is necessary to test the chemical composition.
Question: Can you compare the quality of water in Moscow and other cities in the world?
Alexei Babayev: The World Health Organisation has set the primary standards for water safety: safe in epidemiological terms, harmless in terms of its chemical composition. The regulatory framework varies from country to country. In some cities more attention is paid to concentrations of iron, because a country has an iron issue. The quality of water in Moscow is comparable to European cities like London, or Paris.