Likbez on water treatment and explanations to the chemical analysis of water

For the last five years I have been doing chemical water analysis and have been in contact with water treatment engineers. All sorts of people come to us: for some, the water purification system is a very expensive, but vital purchase, others just read horror stories on the Internet and want “living water”. But for us, as for doctors, all our customers are the same. They have water - well, coming from the city or town water supply, well, river - and it must be cleaned to the established norms. That which pollutes the water, how it is cleaned, and why I calmly drink from a spring containing many nitrates, this story will go. But no company names, geo-references or other individualizing information will be indicated - I just want to share five years of my observations of the process, because many cottage owners might be less nervous if they were concerned about water treatment even at the stage of foundation filling.

But first, let's define the process structure and terminology in order to communicate in the same language. Strictly speaking, without analysis of water, no normal organization involved in water purification, even on the threshold will not let you. It all starts with water analysis.

How to select water for analysis?

The thoroughness with which you carry out a water sample can ultimately affect the installation price. Here are general guidelines.

  1. Take a clean 1.5 l plastic bottle. In no case do not use bottles that previously contained liquids containing organic matter (kvass, beer, kefir, white spirit) or highly mineralized water. Suitable bottles of drinking water. The ideal option is to buy a new bottle where they sell drinks for bottling.
  2. If you have a well - spill it to a permanent composition. Recommendations on how to do this should be provided by your skimmers. Some of our customers said that their well worked on the spout for two or three weeks.
  3. Open the faucet closest to the well to any existing filters, tanks and other devices that may affect the composition of the water, and pour a few minutes to refresh the water in the pipes.
  4. Rinse the bottle twice with selected water, then pour water under the very neck, screw on the cap, slightly squeeze the bottle sideways so that the water flows over the edge, and screw the cap to the end. Purpose: to collect water without an air bubble.
  5. Take the water to the lab the same day. If there is no such possibility - keep the water in the refrigerator for no more than two days.

Further, according to the analysis, the engineers select and calculate the water purification system, and if you are satisfied with the commercial proposal and you pay for it, installers with equipment will go to you. Installers will require you to enter, exit and drainage - where to get water, where to feed it and where to drain it. Particular attention should be paid to the sewer. If you have a pit and you are pumping it out - make sure that it can simultaneously take up 2-3 cubic meters of water without consequences. Why? Filters pass through the dirty water, dirt accumulates on the filter material. Over time, the capacity of the filter material is exhausted and it needs backwashing - with a stream of water from the bottom up, all the dirt from it is flushed down the drain. One washing can take from one hundred liters to one and a half cubic meters of water, depending on the type of filter and the level of contamination. And all this amount will be drained into the drainage in about 20 minutes for room filters, and somewhere in an hour for filling type columns.

Note. Hereinafter I will give the values ​​in the scale of a private household.

By the way, if biological cleaning is used in your septic tank, drainage water can kill it. Also, installers will require you to an electrical outlet nearby (the filters are equipped with controllers - electronic control brains, who themselves know when it is time to start flushing). And also note that any filters must be operated at a temperature not lower than +5 ° C, and, depending on the model, they take up space up to two square meters in area and up to two meters in height (although the smallest filter with all strapping can fit in cubic meter). Yes, do not forget about the water pressure at the inlet! If it is less than 2-3 atmospheres, it is not possible to do without a booster pump. For comparison, the systems of city vodokanals usually supply water to apartments at a pressure of about 4 atmospheres.

At the inlet in front of the filters, coarse cleaning is put - screen filters, mechanics up to 20 microns - in order to protect more expensive equipment from slippage of sand, rust and other large particles. At the exit after installation, it is recommended to install a finishing after-treatment (usually coal removes odors, chlorine and small particles). In the most expensive configuration there may still be an ultraviolet lamp for disinfection at the exit and protection against leakage on the floor, but these are all options. But if your water contains a lot of iron, the engineer can design a water treatment using tanks, which occupy considerable space.

And how much iron is that?

Now you can talk about things closer to my profession. And we start with the units of measurement. In Russia and abroad, paradoxically, completely different units of measurement are used, although the chemistry is the same. We have mg / l and mg-eq / l, and they have ppm.

mg / l (read: milligram per liter) is the mass of the studied particles contained in one liter of the solution (and not the solvent!). If we study the ionic composition of water, then the mass of particles will be understood as the mass of atoms of one type. For example, 10 mg / l of iron means that in 1 liter of solution you have 10 mg of atomic iron - the same one, which has a molar mass, according to the periodic table, 56 g / mol. And it does not matter in what form this iron is a bivalent ion or a trivalent ion. Just some kind of abstraction - iron, as it is in the periodic table. And if we measure the content of a salt, then the mass of particles will be the mass of the molecule of this salt. For example, 10 mg of sodium chloride NaCl in 1 liter of solution.

mg-eq / l (read: milligram-equivalent per liter) - from this moment begins a special black magic. Jeremiah Richter, a German chemist, discovered the law of equivalents (and, incidentally, the portal to hell) in 1792. The law says: substances react in quantities proportional to their equivalents, or m1E2 = m2E1. Try to find a chemist who is delighted, considering the equivalents! I have not yet met such maniacs, although I have been doing chemistry for 14 years. Let's start from afar. Take the usual reaction between chalk and hydrochloric acid:

CaCO 3 + 2HCl = CaCl 2 + H 2 O + CO 2

We will discard carbon dioxide and water, as irrelevant, and select the most important thing in this reaction:

Ca 2+ + 2Cl - = CaCl 2 (in ionic form)

Now we take each of the ions and force it to enter into a hypothetical hydrogenation reaction with a hydrogen cation, regardless of the charge sign (yes, we, chemists, love all sorts of perversions; but in reality, the mass of the hydrogen cation is taken as one, and now we need to find the number other ions equivalent to this unit).

1 / 2Ca 2+ + H + = CaH (equivalence factor = 0.5, and the equivalent of hydrogen is a particle 1 / 2Ca 2+ )

Cl - + H + = ClH (equivalence factor = 1, and the equivalent of hydrogen is a particle Cl - )

So, with one hydrogen cation, either one chlorine anion or half of the calcium cation can (conditionally) react. The numerical expression of the fraction of a substance equivalent to one hydrogen cation is called an equivalence factor. Now we can make a simple conclusion:

1 / 2Ca 2+ = Cl - (1 equivalent calcium = 1 equivalent chlorine)

Imagine that we titrate alkalinity with hydrochloric acid (about these terrible words - later). A variety of salts (hydrocarbonates, carbonates, hydroxides ...) of different ions (calcium, magnesium, sodium ...) can react with hydrochloric acid. How do we express all this in one unit? We have no right to use here the unit of measurement mg ​​/ l already familiar to us, because it is simply not clear - what is milligram? Calcium? Magnesium? Their mixes? What is the ratio? But with equivalents, this problem is removed by itself:

Cl - = 1 / 2Ca 2+ = 1 / 2Mg 2+ = Na + = 1 / 3Al 3+ , etc.

It does not matter to us which kind of cation or anion we titled, but we know that one equivalent of the spent hydrochloric acid will always correspond to one equivalent of an unknown thing that is able to react with this acid. Well, with the equivalent of more or less sorted out. And what is the milligram equivalent? This is the mass of one equivalent in milligrams. Roughly - is calculated according to the periodic table as the molar mass multiplied by the equivalence factor. For the above relationship, it will look like this:

35.45 mg Cl - = 20.04 mg Ca 2+ = 12.15 mg Mg 2+ = 22.99 mg Na + = 8.99 mg Al 3+

Note that the molar mass, for example, of calcium is 40.08 g / mol, but with 1 gram of hydrogen only half of the calcium can react - 20.04 grams. This figure - 20.04 - will be gram equivalent of calcium. Or milligram equivalent. Or microgram equivalent. This unit is convenient because if we ever find out what kind of compound has reacted in that reaction with hydrochloric acid, we can always multiply the number of milligram equivalents by the mass of one equivalent - and thus transfer milligram equivalents to regular milligrams for a particular compound. . So, mEq / l is the number of milligram equivalents of a substance in one liter of solution.

ppm (read: pi-pi, parts per million) is the number of particles per million. It shows how much of the investigated dissolved particles are in one million particles of a solution (not a solvent!). The unit of measurement is used in the West almost everywhere. Corresponds to our mg / l (because a milligram is, like, also a millionth of a liter, provided that the density of the solution is 1.00, but with this dilution, the change in density can still be neglected).

µS / cm (read: microsiemens per centimeter) is a unit of conductivity of water. Take two electrodes, immersed in water. One serves a known amount of current, the second measure how much it has reached. Since the charge carriers are ions in an aqueous solution, the number of transferred elektronchikov from one electrode to another can be concluded about the total proportion of ions in solution. Siemens is the unit inverse to resistance (1 Cm = 1 Ω -1 ). Measuring electrical conductivity can sometimes give a fairly accurate picture of the total salt content of water. If the water is relatively clean, then we can conditionally assume that 1 µS / cm ≈ 0.5 mg / l of salts. And here we are close to the essence of water analysis.

Here it is necessary to distract and clarify that the types of water analyzes - mass. Offhand, there is a chemical and microbiological. And also organoleptic, radiometric, they have no number. I am directly involved in the chemical analysis of water, and we'll talk about it. In Russia, the document regulating the quality of water for household needs is called “SanPiN”. And the controlled parameters there are darkness. It is relevant to note here that there is no such thing as “technical water” in any official document. Moreover, what usually in common people mean by technical water is just water that can be drunk, but cannot be used in the same technique. Sometimes, completely desalinated (deionized) water must be supplied to the production or to the steam boiler.

See in the laboratory all the parameters implied by SanPiN - madness. Firstly, it will take a week to analyze one sample (while the analysis of 12 indicators is done in 2 hours). And secondly, the existing filter materials still only purify water from a finite number of pollutants. And, of course, most of the pollutants mentioned in SanPiN practically do not occur in ordinary natural waters or are found in such quantities that they pass on the norms. Let's go in order with all the comments (in which order - I have not decided yet).

Iron. There are almost all groundwater, but in the surface - rivers, lakes - it can be detected infrequently. It happens in two forms: soluble or bivalent Fe 2+ and oxidized, or trivalent Fe 3+ . Salts of ferrous iron are perfectly soluble in water (iron sulphate FeSO 4 ∙ 7H 2 O will be found by many gardeners in specialized stores), but they oxidize very rapidly with air and turn into ferric compounds. But ferric compounds are not soluble in water - rust has been seen by everyone, and rust is a mixture of Fe 2 O 3 3 nH 2 O and Fe (OH) 3 .

UPD: A special comment about trivalent iron.
Indeed, FeCl 3 is perfectly soluble in water (as noted in the comments), after which it is hydrolyzed to oxychloride and precipitates. The same applies to other soluble compounds of ferric iron - they are subject to hydrolysis in aqueous solution with the formation of insoluble products.

Therefore, in the surface sources of iron is small: if it was originally, it quickly oxidized upon contact with the atmosphere and went into the mud. In addition to the atmosphere, iron bacteria are a natural enemy of ferrous iron, which live off of the energy released during the oxidation of ferrous iron by them. But he has a faithful ally in the form of hydrogen sulfide. Groundwater often contains large amounts of hydrogen sulphide, and it is a strong reducing agent and does not allow iron to oxidize even when in contact with the atmosphere. In general, the dependence of the form of iron in the solution on the redox potential and the hydrogen index is clearly displayed in the Purba diagrams . Iron is one of the trace elements and is needed by the human body (daily need is 10 mg [1] ), and is absorbed, including from water ( well, and the rapidly oxidizing iron in the cut apple is remembered by everyone. UPD: AllexIn pointed out that the color of apples changes because of the oxidation of polyphenols, I didn’t know, but I didn’t bother to check the popular myth. Live and learn! But iron in apples is still present: at a concentration of about 0.1 mg / 100 g), but it is normalized tough, for the most part to save the snow-white shade of toilet bowls (otherwise on the sanfaya ce formed yellow streaks). Of course, the iron content affects the organoleptic properties of water (if it is more than 1-2 mg / l), and its excess intake into the body can provoke various deviations in health. Well, this is always the case. Everything is medicine and everything is poison, the whole thing is in a dose, said Paracelsus.

Especially at the request of ra3vdx I will clarify that Paracelsus did not say that.

MPC of total iron in water for household purposes is 0.3 mg / l. About 0.10 ... 0.15 mg / l (where I live) flies from the pipes in the urban water supply system with rusting. Iron is simply removed: first, it is oxidized to make sure (remember, oxidized iron is insoluble in water), then the resulting particles are coagulated (coarsened), and the whole structure is caught mechanically - on the loading layer. There are different catalytic loads, on the surface of which all of these processes occur. They are sand covered with a layer of manganese oxide - the very catalyst for oxidation of iron - and require periodic reagent washing with potassium permanganate solution (no, manganese compounds are not washed off the feed and do not fall into purified water - well, of course, if you don’t want mix catalytic material with citric acid). There are also non-reagent loads, but before them the preliminary oxidation of iron is required, and the engineer will decide in what way - atmospheric air, ozone or chlorine. If iron in your water is up to 5 mg / l, consider yourself lucky: the installation will be cheaper. If iron 10 mg / l is already expensive. But 30 mg / l and above - you can say goodbye to the planned trip to warm countries. Such an installation can cost several hundred thousand rubles. In general, the main cost of most semi-industrial filtration systems depends on the concentration of iron. The more of it - the more expensive. That is why it is so important to thoroughly spill water before taking a sample - water stagnant in metal pipes may collect iron, and the engineer will offer you, according to the analysis, an installation for which Ilona Mask will not have enough money. But that's not all. We should also mention the so-called organic iron - complex organic compounds containing an iron atom in the molecule (as a rule, humates are complexes of humic acids). It is not easy to knock out iron from such complexes, and it does not oxidize in air. Removing organic iron from water can be difficult.

Manganese. Manganese appears on plumbing gray scurf, so it is rationed hard. This trace element is also necessary for the human body (daily need of 2 mg [1] ). From the water is easily digested. Also contained in beets and half of vegetables in general. Manganese has seven valences, it does not make sense to consider in detail. Bivalent manganese is highly soluble, tri- and tetravalent usually undergoes hydrolysis and precipitates as insoluble hydroxides. Unlike iron, manganese is more common in surface waters. Especially if it is wells, and in the underground water that feeds them, contains some divalent manganese ion. The fact is that manganese is not easily oxidized by atmospheric air. It can be captured by precipitated iron and removed with it. The downloads are all the same, for the principle is the same: oxidation, consolidation and mechanical filtration. MPC 0.1 mg / l.

Rigidity. Rigidity closes the top three parameters, which are aimed at almost all semi-industrial water treatment systems. Yes, there are filters-deferrizer (remove iron, manganese and some other heavy metals) and filter softeners (remove stiffness). Of course, there are other types of filters that work, for example, on oxidation, but ultimately for industrial needs you will be offered reverse osmosis with pretreatment, then the output water will be as per GOST for laboratories: 3 ... 5 µS / cm. But we digress. At school you were told that hardness is a combination of calcium and magnesium ions. They fall out as scum when boiling water. In fact, such a definition is not entirely correct. Yes, calcium and magnesium ions constitute a significant proportion of hardness, but in general, hardness is the sum of all alkaline earth ions, as well as some divalent ions of heavy metals. Zinc, barium, cadmium, even divalent iron - this is all hardness. Another thing is that a chemist in the laboratory will mask ferrous iron ions when measuring stiffness. But cadmium is quite a reflection on the magnitude of hardness. But I will hasten to reassure you: most of the calcium ions in the composition of hardness - as a rule, 80 percent, and another 15 percent of magnesium. Normalize the stiffness solely to reduce the amount of scale in the kettles, and especially zealously - in the industry standards for all boilers, where the stiffness in the water should not be at all. Sometimes you can hear that only soft water should be used on the farm, and hard water is supposedly harmful. Hard water increases the cost of soap, reduces the life of the washing machine ... You can begin to convince, arguing that calcium from the water is still not absorbed, and the body gets it from milk and cheese. It is not correct.

Let's digress and briefly talk about the process of souring milk. Milk contains calcium caseinate and milk sugar lactose. Microorganisms trapped in milk begin to ferment lactose, gradually turning it into lactic acid. Lactic acid knocks calcium from caseinate calcium and replaces it with a hydrogen ion. Calcium caseinate is converted into casein, the milk protein from which the cottage cheese consists. And calcium remains in serum in the form of calcium lactate. So, cottage cheese and calcium cheese are poor. And in natural fresh milk - yes, there is calcium. But, to digest, he must first be removed from caseinate with hydrochloric acid of the stomach. In water, calcium is already ready - immediately in the ionic form, and is absorbed instantly. Therefore, water is one of the most important sources of calcium in the body, and we need a lot of it - the daily need is at least 1000 mg [1] . MPC on hardness - 7 mg-eq / l. If this is translated into calcium, then water may contain (7 ∙ 20.04) 140 mg / l of calcium. So you need to drink 7-8 liters of water to get the daily rate. However, scale begins to form noticeably already when the hardness content is of the order of 4 mEq / l. Manual lump of soap - a mixture of sodium salts of higher fatty acids - on contact with hard water turns into a mixture of calcium salts of higher fatty acids, and calcium salts of soap dissolve poorly in water. But now manufacturers add softening agents to the soap - for example, Trilon B, which level this process.Synthetic detergents - powders, gels and other lauryl sulfates - are generally not afraid of hardness and are not precipitated by it at all. Conclusion?It is useful to drink hard water (7 mEq / l according to SanPiN), wash hands with soap in water with a hardness content of 2 ... 4 mEq / l, and supply soft water to a washing machine and a dishwasher (<0.1 mEq / l), and only in order not to overgrow the heating element. As for teapots, with a hardness of about 2 mEq / l, the formation of scale on the heating element is almost imperceptible. Please note that not all calcium and magnesium compounds fall as scale when boiled. Strictly speaking, this is characteristic only of bicarbonates, and all sorts of chlorides and sulphates both floated in water before boiling and will float after. Typically, in river water (and rivers provide most of our settlements with water), the magnitude of hardness, depending on the season, is 2..4 mg-eq / l (lower in winter).

To remove hardness salts from water, cation-exchange resins are used, which simultaneously bind most of the other cations, including manganese and divalent iron. Therefore, there are options for filters that remove both iron, manganese and hardness at the same load, but there are nuances - iron and manganese should be contained in water in a small amount, and the iron must be divalent (in ionic form). Such filters require regeneration with a saline solution, therefore the consumable material here is tableted salt (just as in iron removers, manganese may be a consumable material, see above). The cation exchange resin is charged with sodium ions. Hard water, passing through a layer of such a load, will exchange ions with the resin - to give calcium / magnesium, to take sodium. In the end, the charge of sodium ions on the resin is consumed, after which the controller will turn off consumers and pour a strong solution of sodium chloride into the filter. There will be a reverse replacement, all hardness ions deposited on the resin will go into the solution, which will then merge into the drainage. And the resin, recharged with sodium ions, can continue to clean the water.

Separately, I want to talk about the Chinese pocket pribchiki, which supposedly measure the stiffness. In fact, these devices are conventional conductometers, or TDS meters. They measure the specific conductivity of water in µS / cm, multiply the value obtained by about 0.5 (see the description of the unit of measurement µS / cm ) and get some value in ppm. And they report to you cheerfully that the hardness of your water is, say, 250 ppm. Firstly. In the West, hardness is actually measured in ppm, while they count by calcium carbonate.

The molar mass of calcium carbonate is 100 mg / mmol, the equivalence factor is 0.5, therefore, one milligram equivalent of calcium carbonate weighs 50 mg. Since mg / l and ppm are practically the same, then when converted to our native units, 50 ppm = 1 mEq / l of hardness. Secondly, by the conductometric method, as I have already said, they determine the total salt content, the sum of all anions and cations in solution. It is practically impossible to measure the hardness by this method separately (it is possible if you find out in the laboratory what percentage of calcium and magnesium ions are the sum of all ions specifically in this water, calculate the correction factor and then conductometric measurement of the same water). And all these alleged stiffness meters simply determine the total salt content in the assumptionthat, apart from calcium carbonate, nothing is dissolved in water.

Alkalinity. It is not standardized, it is everything that can react with 0.1 M hydrochloric acid solution. In our natural waters, these are mainly carbonates and hydrocarbonates. Alkalinity can roughly estimate the percentage of carbonate (temporary) hardness in your water. The rest of the hardness will be non-carbonate, that is, the one that does not precipitate when boiling (chlorides, sulfates ...). This parameter is more needed by engineers in their calculations (it is especially interesting to look at the buffer capacity of water). There are no specific methods for removing alkalinity, and it is not necessary to delete it.

Nitrogenous compounds: nitrates, nitrites, ammonium.As soon as watermelons appear on sale in early summer, nitrates begin to discuss everything around. Meanwhile, nitrates are completely safe. Their MPC is 45 mg / l. But nitrites ... Once in the blood, nitrites bind to hemoglobin, turning oxyhemoglobin into methemoglobin, unable to carry oxygen. MPC of nitrite in household water 3 mg / l. But why no one beats a panic, reading in the composition of the sausage line "nitrite-curing mixture"? After all, it is a mixture of sodium nitrite with sodium chloride. Due to its ability to bind to blood proteins, as well as to enter into asex coupling reactions, nitrite helps to dye meat red. Without the use of nitrites in the sausage, you would eat a completely gray and unsightly products. But you would be healthier, right? Let's take a closer look at this moment. Manufacturers claimthat in their curing mixture sodium nitrite is only 0.6%. Another person has the enzyme methemoglobin reductase, which is able to repair inactive hemoglobin, so it’s too early to cover with a sheet and with sausage in your teeth to crawl to the cemetery. The transformation of nitrates into nitrites in the human body (and it is precisely this that can intimidate you, appealing to the mysterious enzyme nitrate reductase), strictly speaking, is impossible with the body's own forces. It is believed that this enzyme is absent in animals and humans, and I have not yet seen articles proving the opposite. But we live in the oral cavity microorganisms that produce this enzyme. Indeed, they are able to convert nitrates to nitrites. We all die, right?so it's early to cover with a sheet and with sausage in your teeth to crawl to the graveyard. The transformation of nitrates into nitrites in the human body (and it is precisely this that can intimidate you, appealing to the mysterious enzyme nitrate reductase), strictly speaking, is impossible with the body's own forces. It is believed that this enzyme is absent in animals and humans, and I have not yet seen articles proving the opposite. But we live in the oral cavity microorganisms that produce this enzyme. Indeed, they are able to convert nitrates to nitrites. We all die, right?so it’s too early to cover with a sheet and with sausage in your teeth to crawl to the cemetery. The transformation of nitrates into nitrites in the human body (and it is precisely this that can intimidate you, appealing to the mysterious enzyme nitrate reductase), strictly speaking, is impossible with the body's own forces. It is believed that this enzyme is absent in animals and humans, and I have not yet seen articles proving the opposite. But we live in the oral cavity microorganisms that produce this enzyme. Indeed, they are able to convert nitrates to nitrites. We all die, right?that this enzyme is absent in animals and humans, and I have not yet seen articles proving the opposite. But we live in the oral cavity microorganisms that produce this enzyme. Indeed, they are able to convert nitrates to nitrites. We all die, right?that this enzyme is absent in animals and humans, and I have not yet seen articles proving the opposite. But we live in the oral cavity microorganisms that produce this enzyme. Indeed, they are able to convert nitrates to nitrites. We all die, right? Not.The process of reducing nitrates is not fast, the efficiency is not high. And the final products are consumed, in fact, by those microorganisms that the enzyme produces. They so absorb nitrogen.

In addition, this exogenous nitrate cycle plays a huge role in maintaining and improving our health, if only because it normalizes pressure, protects against caries and kills bacteria. Details in article [2](in English.). In addition to nitrate reductase, animals in our oral cavity also produce nitrite reductase, which converts nitrite further to ammonium ion. The ammonium ion affects the acid-base balance of body fluids. There is evidence that with an excess of it can alkalize blood. Our body itself emits ammonia during the breakdown of proteins and then binds it to urea (that is, neutralization methods exist). MPC of ammonium in water for household purposes 2.6 mg / l (in SanPiN: 2 mg / l for nitrogen). As a rule, in natural waters nitrates, nitrites and ammonium do not exceed the MPC, although there are infrequent exceptions. The removal of these compounds from the water is more or less guaranteed only by reverse osmosis. Of course, nitrates with nitrites will sit on an anion exchange resin, and ammonium will sit on a cation exchange,but due to their physicochemical properties, they can be quickly dislodged from the tar by other ions contained in the water.

Oxidation. Otherwise, chemical oxygen consumption. This is all that is capable of oxidizing with potassium permanganate in a sulfate environment: organic molecules, unicellular algae, divalent iron ... True, an analyst and chemist will deduct iron when measuring oxidability. In general, it is possible to indirectly judge the biological pollution of water by oxidation. The unit of measurement of oxidizability is mgO / l (the number of milligrams of atomic oxygen absorbed by a liter of the test solution). Organic iron and oxidability may be related. MPC of permanganate oxidizability 5 mgO / l. There are downloads that work on oxidation. But with its threshold content in your water, the engineer will most likely suggest a carbon filter.

Hydrogen sulfide and radon.Hydrogen sulphide is poisonous and smells faint, radon is radioactive. Should not be present in the water at all, for no benefit from them. Hydrogen sulfide can be oxidized to elemental sulfur at special loads, but only up to a certain concentration. The most reliable method for removing both of these dissolved gases from water is stripping. Atmospheric air is bubbled through the water, as a result of which both gases are blown out of the water and go along with the supplied air into the surrounding atmosphere, poisoning everything around. The room in which this process takes place must necessarily be technical (non-residential) with good ventilation.

Sulfates, chlorides. MAC of the first 500 mg / l, the second 350 mg / l. No toxicology. Normalized due to taste: sulphates are bitter, chlorides are salted. Removed by reverse osmosis.

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Hydrogen indicator. It's pH. On it and we will round out. It is a negative decimal logarithm of the concentration of hydrogen ions, indicating the acidity of the medium. Normalized in the range of 6-9 units. pH. A more acidic solution will dissolve your teeth, a more alkaline one will irritate the stomach lining. A very important parameter for the selection of equipment - many downloads work in a certain pH range. In natural waters it is almost always located near the mark of 7 units. pH, in some extraordinary cases, the engineer may suggest dosing alkaline or acid into the water to achieve the specified acidity value.

In the end I want to add a few words about the types of filters. I mentioned in the text cabinet systems and column type filters. In essence, they are one and the same. There is a kind of cylinder, inside of which are located the drainage-distribution system and filtering material. Only in the cabinet systems it is all clamped in a small volume and placed in a cabinet the size of a washing machine. Of the benefits - less water and reagents for washing, of the minuses - one filter material for all parameters. Column-type filters are more flexible in customization - for example, if the cabinets immediately remove iron, manganese and hardness to zero, and you don’t do anything about it, then by sequentially putting two columns - one for iron and one for hardness - you can adjust the output water hardness so that you feel comfortable taking a shower (so that there is no feelingas if soap is not washed off), while iron and manganese in purified water will not. Remember that the size of the cylinder depends on your water consumption, and you can not put the smallest can on the water consumption of two cubic meters per hour. Just begin the sweep of dirt, and in the end you kill the filter material. Filtering materials, by the way, usually serve 5-7 years, after which they must be replaced. But before I recommend to analyze the water at the outlet, because I personally felt the filter, which has been working properly for 11 years on a single load.Filtering materials, by the way, usually serve 5-7 years, after which they must be replaced. But before I recommend to analyze the water at the outlet, because I personally felt the filter, which has been working properly for 11 years on a single load.Filtering materials, by the way, usually serve 5-7 years, after which they must be replaced. But before I recommend to analyze the water at the outlet, because I personally felt the filter, which has been working properly for 11 years on a single load.

The material turned out great, you can read at night to fall asleep faster and sleep better. I tried to embrace the immensity, told the very essence and now I will add, perhaps, about bacteriological cleaning. There is only one method to kill animals in water - to oxidize it. To do this, in the simplest case, chlorine in the form of hypochlorite will be dosed into the water or an ultraviolet lamp will be placed at the outlet. Ultraviolet ionizes oxygen dissolved in water, and active oxygen will kill bacteria. The best option - ozonator. A UV lamp or ozonizer is placed at the exit after all cleaning, just before the water is supplied to the consumer, and chlorine is the other way round, at the beginning. Because chlorine is a slower oxidizing agent and it needs to be given time, and then to neutralize excess chlorine on a carbon filter.

There are many more nuances and pitfalls in the water treatment. But ... "This is indescribable!" Said Pug, looking at the baobab.

1. Recommended daily allowance
2. Article on the role of nitrates in the body


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