Which water is safer to drink?

2024 Author: Seth Attwood | [email protected]. Last modified: 2023-12-16 15:55

There are problems with drinking water in all cities - both in Russia and abroad. We are afraid to drink tap water, we complain that it gives off sewers or iron, we resent the scale in the kettle and buy artesian water in bottles or blindly trust the advertisements of various filters.

In this article, we decided to figure out what pure water is, what substances and salts cannot be removed from it, since they are useful, and, in general, what to do with “bad” water in homes.

Chapter 1. Distilled water, and why drink it

Let's start with the fact that ideal water, defined by the chemical formula H2O, does not exist in nature at all. Many people believe that H2O is distilled water, but this is not so: even in distilled water obtained by distillation in special apparatuses, atmospheric gases are dissolved - oxygen, nitrogen and argon, plus a number of others, and therefore it is not ideally pure.

There is a well-known physical trick used during science shows - the experimenter plunges his hand into a filled aquarium with a hairdryer or toaster plugged in, and he is not electrocuted. Distilled water is simply poured into the aquarium, which does not conduct electricity. Although, in fact, the specific electrical conductivity of such water according to GOST is not zero, but 0.5 mS / m, that is, the current is flowing, just so insignificant that it is safe for health. Well … how safe. Do not do this at home under any circumstances, because such tricks require special training.

One way or another, distilled water is a technical liquid. It is used in areas where scale formation must not be allowed - for example, for flushing cooling systems in an internal combustion engine, when working with batteries and other elements of the electrical system. You can pour it into the iron - there will be no scale either. It is also widely used in pharmaceuticals (and not even it, but the so-called bidistilled water, which has passed two stages of distillation). You can drink it.

But, firstly, it is not very tasty (in fact, distilled water does not have a pronounced taste, and drinking it is like breathing ordinary air, a mechanical process that does not have a sensory component).

And secondly, not all salts removed during distillation are useless for the body - on the contrary, water should serve as their source. That is why various useful mineral water is sold. Many people mistakenly believe that distilled water is expensive and rare, but here we will disappoint you: it is sold at any gas station and costs 100 rubles per 5 liters, about the same as ordinary drinking water in stores. Everything, with distilled water sorted out. You can drink it, but to some extent it is pointless.

Chapter 2. Tap water, and why it is dangerous

Tap water begins its journey in river water intake systems and flows from there to a water treatment plant. In Moscow, for example, there are four such stations - in principle, one can roughly imagine the volume of work of each station, taking into account the size of the city. There are cities that do not have their own reservoirs - water comes there from distant rivers, lakes, reservoirs or "foreign" water intake systems, but one way or another it is purified at the stations.

Water is processed in particular with sodium hypochlorite (many city dwellers complain about "chlorine", well, this is its modern, safe and odorless version; 20 years ago, it was treated simply with chlorine, and then the water smelled like "chlorine" just inhuman). Ozonation, cleaning with carbon filters and a number of other methods are also used. In fact, technology is highly dependent on a specific country, city, geographic and social factors.

This is where one "but" arises. Water goes a very long way from the purification station to your tap. And the reservoirs and pipes of the water supply network in Russia do not always correspond to the norms of their operation in terms of terms. In other words, many houses built before the war, on the one hand, are remarkable monuments of the avant-garde, but on the other hand, they have hydraulic systems that are completely unusable due to their age.

A typical example is, for example, the constructivist communes of Yekaterinburg. In many houses of the 1930s series, initially there were no kitchens (it was assumed that the workers' food would be centralized in kitchen factories), they were "built" into the layout along with water supply systems in the 1950s, and since then the pipes have been lying. leaving rust in the water and more. Ideally, of course, tap water should satisfy SanPiN in terms of the maximum content of various substances (MPC), sometimes very unpleasant. These are iron, copper, lead, mercury, molybdenum, selenium, aluminum, magnesium, fluorine, hydrogen sulfides, calcium, magnesium, chlorine - not all at once and not always, but nevertheless.

The reasons for the appearance of certain compounds in water are different. For example, lead can enter the water supply system from wastewater, which is discharged into a river and then into a water intake for treatment. Iron, zinc and copper are most often the result of contact with pipes and tank walls. And aluminum is added to water at treatment plants as a coagulant. The norms for the content of these substances are generally quite small (say, for mercury, which is a poison, this figure is 0, 0005 mg per 1 liter), but at the same time they are non-zero.

Independent researchers unanimously say that water in large cities - Moscow, St. Petersburg, Kazan - meets all standards. But, first of all, it satisfies today, but not tomorrow. Secondly, there is the concept of individual intolerance - for example, the norms for pregnant women differ from the typical ones downwards. Thirdly, many substances have the ability to accumulate. So compliance with GOSTs is not a panacea.

Moreover, any norms are a compromise between the physiological needs of a person and his economic capabilities. You can make the water better - but it will cost significantly more. And since we use up to 95% of drinking water for domestic purposes, such a compromise is perfectly reasonable. The conclusion is simple: you can drink tap water (it is better to boil it at the same time), but additional processing will not interfere with it.

Chapter 3. Artesian waters: what to buy in the store

The simplest solution to the problem of "bad water" is to buy bottled water in the store. Moreover, it can be not only pure, but also mineral, that is, enriched with substances useful to humans. According to the degree of mineralization, such water is divided into three types - table water (total mineralization up to 1 g / l), medical table water (1 - 10 g / l) and medicinal (more than 10 g / l or high content of individual elements). It is not worth boiling mineral water - salts will precipitate, - but drinking it is pleasant and healthy.

The path of mineral water most often starts from an artesian well located on the territory of the manufacturing enterprise. The term "artesian" means that water is taken from an aquifer that lies deep enough between two water-resistant rock layers. The main value of such water is that it is not affected by anthropogenic polluting factors (although, of course, there are exceptions - for example, an artesian reservoir can be polluted by oil outflow as a result of improperly planned drilling).

It happens that melt water from mountain streams or other water sources are used that also do not have contact with man-made pollutants.

Actually, such water is mostly mineral in itself. For example, the legendary "Essentuki", depending on the well, have one or another natural mineralization. For example, "Essentuki" No. 17 is hydrocarbonate-chloride-sodium, that is, it contains hydrocarbonates with a volume of more than 600 mg / l, chlorides with a volume of more than 200 mg / l, as well as Na cations₊… Artificial mineralization is most often carried out in order to give the water a more pleasant, familiar taste. There are special additives for mineralization, as well as mineralizing devices. Do they make sense?

Certainly. For the most part, natural mineralization is sufficient, and the choice of waters containing a wide variety of substances is huge. But if the water is not bought in a bottle, but comes from the tap, it can and even sometimes needs to be artificially saturated with minerals. Let's put it this way: artificial mineralization exists in parallel with the sale of natural mineral water and does not pretend to be its “niche”. Summing up: you can buy bottled water in stores.

Usually it is artesian water, moreover, it is additionally purified. In any case, it will be better than tap water, and richer in useful composition than distilled one. There are two stopping factors: firstly, the cost - water is not very expensive, but you need a lot of it. And secondly, the need for constant supplies. Even 19-liter tanks run out quickly, and new ones need to be bought. Not to mention five-liter bottles.

Chapter 4. Home Cleaning: Filters and Reverse Osmosis

The fourth type of water that we can get in the city is tap water, which has passed through an additional filter. Desktop, in the form factor of a jug, or more complex, installed under the sink. Many people consider such filters to be a panacea (this is not so), while others, on the contrary, are sure that they are of no use (this is also not so). A filter is most often thought of as a kind of mesh through which large particles of contamination cannot pass.

This is a correct idea of the very first stage of filtration, which eliminates mechanical impurities - but the main cartridge in a good filter is a completely different device, the so-called reverse osmosis membrane. Osmosis was discovered a long time ago - in 1748 it was observed and described by the French physicist Jean-Antoine Nollet, and at the beginning of the 19th century, another Frenchman, Henri Dutrochet, studied this phenomenon in detail and published a number of works on it, which are still fundamental. The essence of the phenomenon is as follows.

Imagine that we have two solutions of different concentrations, separated by a partially permeable membrane that allows solvent molecules to pass through, but not a solute. As a result of osmosis, a solvent from a less concentrated solution will penetrate through the membrane into a more concentrated one - until the concentration is equal. In the case of water, salts are solutes and water is a solvent. Excessive hydrostatic pressure, which leads to equalization of concentration in both zones, is called osmotic.

But if a pressure greater than osmotic pressure is applied to a more concentrated solution, then osmosis will reverse - that is, the solvent will penetrate from a zone with a high pressure - into a zone with a lower one, from a more concentrated solution to a less concentrated one. Since osmosis separates the solvent and the solute at the molecular level, practically pure water accumulates on one side of the membrane of the reverse osmosis filter. “Practically”, because, as we wrote at the very beginning, it is impossible to purify water 100% under any circumstances, something will still penetrate and remain.

The higher the pressure on the solution, the more efficient the passage of the solvent (water) through the membrane. A reverse osmosis filter is somewhat similar to a juicer. We press the orange to the grater, the juice passes through it, but the peel, films, bones and everything else that we do not like so much does not pass. And when this happens at the molecular level, filtration approaches distillation in quality. The disadvantage of such a filter is the speed of work.

It works very slowly, and therefore must have a storage tank. The second disadvantage is that reverse osmosis is too high-quality cleaning method. As, imagine, an eternal light bulb. On the one hand, it is nice that it is always on, on the other hand, with such bulbs, all electric companies will go bankrupt, and there will be no bulbs. Therefore, after purification, reverse osmosis water is artificially mineralized (just what we wrote about earlier) with calcium and magnesium in optimal concentrations. Well, or other substances - mineralizers are different. This, among other things, gives the water a more familiar taste.

Filters with reverse osmosis membranes are relatively expensive (on average, from 6,000 to 15,000 rubles), but do not forget that this device is installed for many years, like, say, a refrigerator or a TV.

So a home filter is a good thing. Yes, for certain purposes, you still have to buy bottled water - for example, if you need some specific mineral water with specified mineralization parameters. Or, say, distilled to fill the battery. But since we still use tap water for most domestic - and culinary in particular - tasks, purification using reverse osmosis and subsequent artificial mineralization is the optimal solution for a large city. If you live in the "Shelter 11" area at an altitude of 4100 meters on Elbrus, then this article does not concern you - at such an altitude, exaggerating, you can even eat snow, and it will be many times cleaner and healthier than tap water.