Chemical reagent methods of water softening. Water softener. Freezing - a simple and effective way

"and" Chemical reagent methods of water softening" section "Water" and subsection "" we touched on the topic of combating hardness salts and scale. In previous articles, we examined the actual definition of the word "water softening" and considered that there are several ways of softening - physical, chemical, psychic.And also touched upon such reagent methods of water softening as ion exchange and the dosage of antiscalants (antiscale formers).In this article we offer you two subsections - a little about psychic methods and a little more about physical methods of water softening.

Psychic and physical methods of water softening are not fully understood and studied. This is probably why very often the psychic way of dealing with hard water is confused with the physical way of dealing. And, accordingly, they lose money, time and faith in people. Both for the purchase of psychic gadgets, and for the repair of equipment that they did not protect from scale. By the way, for good understanding articles, we recommend that you first study the materials of the articles "Hard water" and "", where the main definitions used in this article are given (such as water softening, scale, hardness, hardness salts, etc.)

Psychic methods of water softening.

So, psychic methods are easily confused with physical ones. About the same as the ganzfeld effect with magic. For example, water treatment magnetic field. This and quality way dealing with scale, and a useless extrasensory way of cleaning and structuring water.

The difference between physical and extrasensory methods is very simple - if a thing costs a little money (up to 100 USD on average), and it is promised that it will fulfill a lot of tasks (such as: it will purify water from all substances, remove scale, heal and give youth, structures, accelerates the growth of plants and hair, removes spoilage, etc.), then this is a psychic method of water purification. We will not dwell on extrasensory methods in detail, they are described in various sources (for example, here), since the sense from them is only a hundredth of what was promised.

By the way, in recent times there was a tendency to increase the cost of such softening structurers. So you can run into a very expensive fake, which is declared as protection against scale. However, usually devices that can really physically help with scale do not have additional structuring functions.

So, if you want to do extrasensory structuring, then you need to purchase a special device. If you need to soften the water physically, you need to purchase a special device. But not complex. Although ... As anyone likes it 🙂 And we will move on to physical ways to deal with scale.

As mentioned earlier, there are several definitions of the term "water softening", depending on the stage at which the impact occurs -

  • at the stage of combating the causes of water hardness or
  • at the stage of dealing with the consequences of using hard water.

The previous methods - ion exchange - are aimed at combating the causes of water hardness. That is, either calcium and magnesium salts are removed from the water, which leads to the creation of soft water.

Physical methods of water softening are aimed at coping with the consequences of hard water - scale.

Accordingly, physical softening methods do not imply soft water in the first sense (water without hardness salts at all). The result of the work of physical water softening is water that has retained all its hardness salts, but does not harm pipes and boilers - that is, it does not form scale. However, hard water after physical treatment changes its properties - and, as a result, ceases to form scale. That is, it ceases to be rigid. And it becomes soft. Of course, if we were doing scientific research, we would introduce a difference in terms of "soft water", that is, water in which there are no hardness salts in principle, and "softened water", which does not form scale, but may contain hardness salts. However, these are terminological nuances that are not of interest to us. Us actually physical methods of water softening.

There are such basic physical ways to deal with scale:

  1. Treatment of water with a magnetic field.
  2. Treatment of water with an electric field.
  3. Ultrasonic water treatment.
  4. Water treatment using low-current current pulses.
  5. Thermal softening method (normal boiling water).

And we will begin to gradually characterize the physical ways to deal with hard water. We may not cover everything at once in one article, but a series of articles will definitely include the characteristics of each of the methods. Let's start with water treatment with a magnetic field, since this type of physical descaler is most often confused with psychic water softening.

Treatment of water with a magnetic field is a complex and controversial issue. Without going into details, we can say that effective physical softening of water using a magnetic field is possible only when a huge number of factors can be taken into account simultaneously. This is:

  1. magnetic field strength,
  2. water flow rate,
  3. water composition:
    • ionic (including the presence of iron and aluminum ions that impair the physical treatment of water),
    • molecular (including large organic molecules, especially those with the ability to form complexes),
    • mechanical impurities (including rust),
    • ratio of para- and diamagnetic components,
    • dissolved oxygen and other gases
    • the presence of non-equilibrium systems, etc.
  4. water temperature during and after treatment,
  5. processing time,
  6. Atmosphere pressure,
  7. water pressure,
  8. etc.

All these and many other factors affect the efficiency of magnetic water treatment. Thus, an insignificant change in the composition of water should be compensated by changes in the specified parameters (for example, water velocity and magnetic field intensity). All changes must be monitored and responded to immediately, since the effectiveness of the physical softening of water using a magnetic field will change in an unknown direction.

But it is possible, and magnetic water treatment is successfully used in many boiler houses. First of all, this happens because in boiler houses the constancy of most of the listed factors is observed - both the flow of water, and the composition of water, and the temperature of the water, and pressure, etc.

However, this is practically NOT possible to repeat at home. And when you have a desire to buy a magnet for a pipe in order to save your house from scale, then think a lot of times, and first of all, consider whether you can organize not only the constancy of the indicators described above, but also find their optimal combination through experiments.

If not, then treating water with a magnetic field in the form of magnets is not for you, and you will get nothing but wasted money on buying a magnet and repairing equipment and pipes. In another way, it can be said like this: the probability that a tube magnet will help you is less than 10%. That is, at home, a constant magnetic field approaches extrasensory water softening.

In order to compensate for the variability of water parameters during physical treatment, more modern methods physical softening - for example, using an electronic water softener.

Thus, do not confuse psychic water softening, limited area physical softening, and modern physical water softening.

Which will be discussed in the sequel.

To some, the phrase "hard water" will seem like a literary oxymoron, but there are many people who are familiar with this quality of water firsthand. How to determine the degree of hardness and why soften water - we will tell in this article.

Hard water is the reason for the formation of salt deposits, kidney stones, cardiovascular diseases. 80% of diseases a person drinks with water. 90% of failures of water heaters and other equipment working with water are caused by high severity.

What is the purpose of the water softening process?

Water hardness is a combination of its physical and chemical properties associated with the content of dissolved salts of alkaline earth metals. First of all, calcium and magnesium are hardness salts. AT natural environment they govern various chemical processes. The hardness of water is mainly influenced by its deposit. Rivers and lakes are replenished from underground sources flowing in limestone layers and enrich the water passing through them with hardness salts. AT surface waters contains significantly less calcium and magnesium than in the deep. The hardness of water in natural springs reaches its maximum in winter, and its minimum in spring, thanks to melting snow.

There are three types of water hardness:

  • General. This is the total concentration of magnesium and calcium ions.
  • Carbonate. Its second name is temporary, since the indicators depend on the content of calcium and magnesium carbonates and bicarbonates in water, which are almost completely eliminated by boiling.
  • Non-carbonate, on the contrary, is a constant value, because it is due to the presence of magnesium and calcium salts, which are not affected by temperature changes.

In the SI system, water hardness is measured in moles per cubic meter -mol/m³, but milligram equivalents per liter are also used in practice -mg-eq/l. According to the norms of SanPiN, the hardness of drinking water should be no more than 7 mg-eq / l. Required water hardness for beer production -up to 4 mg-eq/l, soft drinks -0.7 mg-eq/l.

Excessively hard water is one of the reasons for the formation of kidney stones, since calcium and magnesium bicarbonates make it difficult for the stomach and intestines to work. The so-called salt deposits in the joints can also be the result of drinking hard water. The hardness salts contained in it actively interact with soaps, shampoos, balms and other similar products, forming a precipitate and reducing their effectiveness. Due to the destruction of the natural fatty protection, the pores on the human skin are clogged with neoplasms, making it difficult to breathe. This can lead to dryness, acne, dandruff, as well as breakage and hair loss. Hard water also affects cooking in a bad way, destroying the ingredients contained in useful material.

Hard water significantly shortens the service life household appliances: dishwashers, boilers, kettles, etc. Due to the crystallization of salt, scale is formed, which subsequently leads to corrosion and breakage. As in the case of shampoos, when washing in hard water, part of the “forces” of the powder is directed to neutralize its effect, but here, in addition to the banal overspending detergents, the chances of getting stained or streaked laundry increase. They also arise due to scale formed on the "insides" of the washing machine.

In urban areas, hard water is now almost never found, but in private sectors and countryside the situation is different. Usually their inhabitants use water from a well or artesian well, which receive saturated with calcium and magnesium ground water. In addition, along with hardness salts, others can also get there. harmful substances. For this it is enough heavy rain and a nearby garbage dump.

How easy it is to understand water softening - this is a decrease in the concentration of hardness salts in it. The simplest version of this process is thermal (it is also simple boiling). As mentioned above, in this process, calcium bicarbonate decomposes into insoluble calcium carbonate, which precipitates, and carbon dioxide. The concentration of calcium sulfate also decreases slightly. This method considered the simplest, but its performance leaves much to be desired. Is there some more chemical method when reagents are added to water that turn soluble compounds into insoluble ones. The main disadvantage is that you still can’t drink such a liquid. Other methods require special equipment.

Water softening equipment

In addition to flying to heating elements household appliances and stains on washed linen, a sign of hard water are poorly foaming soaps and powders, meat that is hard even after long cooking, the absence of the usual aroma of tea and coffee, as well as the bitter taste of the water itself. In addition, water hardness can be determined using special test strips or a TDS meter measuring the electrical conductivity of a liquid. However, before purchasing a filter for softening water, it is recommended to send it to a laboratory for analysis, so that experts can make the most accurate “diagnosis”. For example, flow filter for water softening will be relevant only for liquids without a critical iron content, and in severe cases it is better to use the trunk.

What installations are used for water softening? Experts distinguish the following categories of filters:

  • Membrane. Eliminate up to 98% of impurities, making the water actually distilled. However, in order for the quality of their work not to decrease, it is necessary to maintain a pressure of at least 3–4 atmospheres in the water supply system. Such a device is quite expensive, but it also has a long service life.
  • Polyphosphate. They are a flask with crystals of polyphosphate salt. The water passing through them is saturated with sodium polyphosphate. Usually attached in front of household equipment. Polyphosphate filters are inexpensive, but they need to be changed every six months. It is not recommended to drink water softened with their help.
  • Magnetic. Thanks to them, a constant magnetic field acts on the water, which changes the structure of hardness salts. The molecules cease to combine when heated and do not form a precipitate, and also destroy the already existing scale. The salt concentration remains the same, so that such devices are mainly suitable for pipes and pumping equipment. Depending on the variety, magnetic filters can operate from 5 to 25 years without the need for maintenance.
  • Electromagnetic. They work on the basis of radiation of electromagnetic waves of the required frequency. They require a network connection, but do not consume a lot of energy. Compatible with any other water softening systems. Excess salts are then removed through the sump into the sewer. As well as magnetic ones, they additionally destroy scale, but they cost an order of magnitude more expensive.
  • Ion exchange filters for water softening. Their clear plus is the high performance and durability of the filter element. They are a column or cabinet type filter, inside of which there is an ion exchange resin. As with magnetic filters, they can only be used to clean cold water. The filtration process consists in replacing calcium and magnesium ions with sodium ions, which do not harm the human body and household appliances.

Despite the fact that after the ion-exchange method of softening water can be drunk, it is considered reagent, the rest are classified as non-reagent.

To de-iron does not mean to soften

The term "hard water" is not synonymous with "iron water". Fresh water also contains iron, which enters wells and boreholes from collapsing rocks, and into pipes from aging and corroded iron and steel water pipes. It is not difficult to determine water supersaturated with iron by eye - it has a characteristic metallic smell and a yellowish-turbid tint. With such indicators, white things also become yellowish after washing, and brown spots appear on plumbing.

In our country allowable amount iron in water should not exceed 0.3 mg-eq / l. The recommended total iron intake for an adult is 25 milligrams per day.

"Overdose" can lead to urolithiasis, intestinal disorders, gallbladder diseases and dental problems, as well as dermatitis and the development of allergies. Therefore, there is no point in purchasing water softening devices, while neglecting iron removal equipment. It is also different, both chemical, when iron is destroyed by reagents, and mechanical, when iron is decomposed using aeration, coagulation, and the ion-exchange method described above. Moreover, there are “two in one” installations that simultaneously work both for water softening and iron removal. They save space in the house, the owner's budget and his time in equal measure.


Technology is advancing rapidly, and maybe someday all the water on Earth will be exceptionally clean. But until this happens, the presence of a water filtration system is an urgent need, because human health directly depends on it. At the same time, you don’t want to spend a lot of money on inefficient equipment, so the choice of a filter for iron removal and water softening should be approached carefully.

Hard water is distinguished by a high content of minerals - most often magnesium and calcium. They form deposits that subsequently clog the sewer, leave plaque on the tile, and prevent the soap from foaming normally. It does not pose a threat to life and health, but it still causes certain inconveniences. In this article, we will reveal the essence of the concept of hard water and talk about ways to soften it.

Hard water is water that contains a large number of salts of calcium and magnesium. Additionally, it may contain silicates, phosphates, chlorides and other toxic compounds. Some of them completely decompose when boiled, while others are able to remain unchanged for a long time.

Why hard water is harmful to health and household appliances

Scale in the kettle, a characteristic deposit on the walls of washing machines and others household appliances clothes that have lost their original color brightness after washing - delivers modern man a lot of inconvenience, so he seeks to soften it. Do not like this liquid and skin, hair, internal organs The kidneys and liver are especially affected.

Increased water hardness reduces taste qualities and digestibility of food, can cause the development of urolithiasis, problems with the liver, even the heart. But it has nothing to do with the presence of worms in the body.

Optimal water hardness, how to determine the hardness of water at home

Before you begin to carry out activities aimed at softening too hard water yourself, determine the salt content and the level of hardness of the liquid. This can be done in special services, and then checked with current standards. Don't want to go anywhere? In this case, you should be alerted by scale on the internal parts of household appliances, a small amount of soap foam, dry skin and hair. Taste may vary, but this is not a prerequisite.

How to soften hard water at home: 8 sure ways

The main ways to soften hard water:

  1. Boiling followed by settling.
  2. Adding to washing machine soda or lime. A more modern alternative is a special powder.
  3. Softening with ammonia - just keep in mind that concentrated undiluted products are on sale (read the instructions!).
  4. The use of a filter jug ​​from Aquaphor.
  5. Installation of coal household filter to a faucet or plumbing.
  6. Installation of the Aquaphor purification system - it replaces magnesium and calcium ions with sodium ions.
  7. Installation of a special mechanical cleaning device at the inlet of the pipeline.
  8. The use of a magnetic softener.

Domestic water

Soda ash and baking soda effectively neutralizes salts - water purified in this way can be used for drinking purposes. Baking soda completely harmless, does not dry the skin, so it is added to the water for washing. The calcined variety is more aggressive and gives a pronounced whitening effect, so it can be used for washing clothes.

How to soften hard water at home from a well or well

To soften water from wells and wells, the same methods are used that are used to soften ordinary tap fluid:

  • thermal (boiling);
  • reagent - with the addition chemical substances different origin, which, when interacting with hardness salts, bind them;
  • using filters (magnetic, membrane, ion-exchange, electromagnetic);
  • folk ways.

Each option has its own characteristics, advantages and disadvantages. When choosing, be guided by the current hardness indicators, the available budget and the desired water treatment rate.

Ways to clean and soften water at home

If you want to not only soften, but also purify the water, use any of the following options:

  • filter jug;
  • ion exchange filter;
  • membrane filter;
  • magnetic filter softener;
  • electromagnetic method.

Also used folk methods– sedimentation, saturation with silicon, partial freezing, mixing, addition of decoction flax seeds, herbs or peat.

Filters and their varieties

On sale you can find the following types of filters:


Which is better: conventional softening or complete water filtration?

The softening filter does not always give the desired results - in some cases, complete filtration is required. The cleaning system removes elements of calcium and some salts (partially), while complete filtration allows you to get rid of all chemical impurities and change the metal composition, remove salts. At the same time, it can be accompanied by softening, mineralization. If everything is done right, tap water will have a good smell and pleasant taste.

Magnetic filter or special salts: choose an alternative

Special salts give a good effect, but do not forget about the dosage for each substance. Also, you will have to ensure their constant availability and appropriate storage conditions - and this extra space, additional costs and hassle. At the same time, it is not always possible to use water softened with the help of reagents for cooking and drinking.

What is a magnetic filter? A device of two powerful magnets that create strong field- it attracts metal particles. Water when passing through such an element becomes softer. Chemical preparations are not used, but the effect of water charged with a magnetic field on the human body has not yet been studied either.

How to soften hard water in an aquarium at home?

Mandatory softening requires water in the aquarium. At home, stiffness can be reduced in the following ways:

  1. Boil, cool and pour into the aquarium.
  2. Distill, but remember that a deficiency of useful trace elements is harmful not only to humans, but also to fish.
  3. - Pour water into a container and put in the freezer. When half of the liquid is frozen, pour out the part that is not frozen, and remove the ice from the refrigerator and melt. This liquid is ideal for fish.
  4. Purify water with a filter reverse osmosis- it is installed in the room and connected directly to the water supply.

The most efficient and costly way is reverse osmosis. It makes sense to use it for large aquariums.

Good to know

  • Water softening leads to noticeable savings detergents, because in soft they foam better. We are talking not only about soap, but also about washing powder, toothpaste, etc.
  • Electricity consumption can also be reduced, since you will be doing less laundry and cleaning.
  • The life of household appliances and water pipes soft water will also noticeably prolong.
  • At the same time, the use of any softening method requires certain investments, which do not always pay off.

How to soften hard water. Ways, tips, harm and benefit, different methods, features and acceptable indicators.

We have all heard about the dangers of hard water - not only for kitchen appliances and heating equipment but also for the human body. However, few people know that its rigidity is different in "origin", and besides, it is not an absolute evil. Therefore, today we will look at how you can make the most effective softening of water for drinking and domestic needs in order to get the most out of it.

Features of hard water

Water becomes hard from dissolved salts - calcium and / or magnesium compounds (the cations of the latter are much less common). There are other elements, the presence of which may affect the final indicators of rigidity, for example, manganese, strontium, barium. But their influence is so insignificant that it is simply not taken into account.

The general hardness index is usually divided in accordance with the composition of the salts:

  1. Carbonate or temporary hardness - determines the content of Ca and Mg bicarbonates in water at a pH level exceeding 8.3 units. It can be easily dealt with by prolonged boiling - after an hour, the salts will simply disintegrate under the action of high temperature and will fall out.
  2. Non-carbonate hardness is called constant, because it is not so easy to get rid of it. It is determined by the content of stable salts of various acids, which do not decompose and must be removed by other methods, such as reverse osmosis.

In sum, these two indicators just give the overall stiffness, although it is difficult and expensive to calculate them separately. Usually, special reagents or indicator strips are used to determine the actual salt content.

But you can find out that your system has hard water without laboratory research. In the process of use, it delivers a lot of problems that are simply impossible to ignore:

  • White marks on washed clothes;
  • Weak foaming of detergents, and as a result - their inefficiency;
  • Scale on the walls of the kettle (and imagine what happens to the heating elements of boilers, washing machines and dishwashers);
  • Constantly appearing plaque on the mixer and sink.


Hard water also causes considerable harm to the human body. The feeling of skin dryness after contact with such an environment is nothing more than washing off the protective lipid film from its surface. And the use of this water inside without preliminary softening can provoke urolithiasis.

But this does not mean that water softening should be total, even if it is used for drinking and cooking. A liquid completely devoid of salts leads to a deficiency of calcium and magnesium ions in the body, which negatively affects the functioning of the cardiovascular system. The harm and benefits of drinking water hardness is one of the medical paradoxes. But it is allowed simply - compliance with the measure.

From the point of view of doctors, the use of too hard, as well as too soft water, is unacceptable. Here you need to stick to the golden mean.

"Resoftened" water can harm and steel pipes plumbing and heating systems- because of it they are more exposed to corrosive wear and serve less than pipelines transporting rigid media.

Folk ways of softening

Our grandmothers also faced the problems of hard water, and they at least guessed about the dangers of using it. Therefore simple and available ways there is enough softening in the piggy bank of folk wisdom. We present the most popular of them.


Boiling (and not in an electric kettle, but on the stove, since to achieve desired effect decomposition of hardness salts is possible only with prolonged heating). After this, the liquid should be allowed to settle for a day, and only then it should be carefully drained without stirring up the sediment at the bottom.

Freezing is a more gentle way that will allow you to at least partially preserve useful substances in water and not spoil the taste. A transparent container with water must be sent to freezer and watch it freeze. As soon as 75-80% of the total volume turns into ice, the vessel is taken out and the liquid residue is drained - salts are concentrated in it, which give high rigidity.

Settling. You just need to pour water into any container and remove it away from sunlight for 3-6 days. After that, you need to carefully drain the upper layers without disturbing the sediment. Such water is not suitable for drinking, but it is quite suitable for domestic use.

The addition of silicon or shungite - minerals that literally absorb hardness salts. Our great-grandfathers lined wells with flint to soften the water stored in them. A simpler method is available to us: you just need to lower the sterile stones of silicon or shungite into a container with drinking water. Natural absorbents will absorb salts in 2-3 days, although many recommend increasing this period to a week.

Saponification is one of the ways to prepare water for washing. It will be necessary to grate 15-20 g of laundry or toilet soap and dilute it in 0.5 liters of water until completely dissolved and foam appears. This amount is enough for a bucket of liquid, after which you need to stand everything for at least a night - the soap will react with the salts and send them to sediment. In the morning, the solution is carefully poured into another container and added to it. boric acid(2-3 tablespoons).


Modern methods

For us modern people, there are more simple ways how to soften hard water. To do this, it is enough to buy and insert softening filters with ion-exchange resins into the supply system. They are dual tanks and work according to the following principle:

  1. Hard water enters the compartment with resin, which “extracts” calcium, magnesium and other alkaline earth elements from it.
  2. The depleted liquid flows into the second tank with ordinary table salt, where it is enriched with sodium ions - much more useful for the body.
  3. Residues with "harmful" elements are removed along with drains.

As a result, we get safe and tasty softened water of normalized hardness. It can be used both for household needs and for drinking or cooking.

AT different countries their own rules apply. Our maximum indicators for drinking water are set at 7 mg-eq/l, for technical water - no more than 9 mg-eq/l.


The softening effect is also obtained after running water through a reverse osmosis system. It works in a completely different way: it forces the liquid through a special membrane with very small pores (0.0001 micron in size) and traps impurities at the molecular level. Thus, water is freed not only from salts, but also from bacteria and other foreign elements, turning practically into a distillate.

Alas, the constant use of it in food does more harm than good. Therefore, after purification and softening, it is desirable to pass such water through a system of mineralizers, which will enrich it with safe substances and restore optimal hardness. However, it is quite suitable for household needs.

Also, to protect equipment from hard water, various additives are used:

  • Food, soda ash;
  • citric acid;
  • Vinegar;
  • Any water softener based on polyphosphates (Calgon, Eonite, Sodasan, etc.).

Federal State Educational Institution of Higher Professional Education

"SIBERIAN FEDERAL UNIVERSITY"

Polytechnical Institute

abstract

Methods for clarifying and softening water.

Use of an IOMS inhibitor.

Head ________________ Yakovenko A.A.

Student TE 06 - 03 ________________ Minaeva D.S

Krasnoyarsk 2009

Water clarification methods.

Water clarification is understood as the release of suspended solids from it during the continuous movement of water through special structures (settlers, clarifiers) at low speeds. At low speeds of water movement, the suspended solids contained in it, the specific gravity of which is greater specific gravity water, under the action of gravity, are deposited, forming a sediment in the sump.

Technological schemes for water treatment are determined in each case depending on the requirements and include the following stages of work:

    technological research and preliminary laboratory testing of the reagents used;

    selection and calculation of equipment for dosing and mixing reagents;

    selection of equipment for thin-layer clarification and suspension compaction;

    selection and calculation of fast filters with granular loading, both pressure and open type;

    selection of technology and equipment for sludge dehydration with subsequent disposal;

    selection of equipment for disinfection by dosing a solution of chlorine reagent (sodium hypochlorite) and quality control of treated water.

Depending on the direction of water movement, sedimentation tanks are divided into horizontal, vertical and radial.

The horizontal settling tank (Fig. 1) is a tank of rectangular section, the longitudinal (longer) axis of which is directed along the movement of water. The clarified water is directed through the pipe 1 to the distribution chute 2, which has a number of holes that serve to more evenly distribute the water flow over the cross section of the sump. The speed of water movement in these holes should not exceed 0.4 m/s. The clarified water enters another gutter 3 and is discharged from it through a pipe 4 to the filters. Settled particles (sludge) accumulate on the bottom, which should have a slope opposite to the movement of water.

The settling time for horizontal settling tanks is usually taken for a coagulated mixture no more than 4 hours. Horizontal settling tanks for clarification of large amounts of water can be divided in height into several compartments (floors) connected in parallel. The advantages of storey settling tanks (proposed by Prof. P.I. Piskunov) are a small building area and less concrete consumption. Such a sump was built at one of the largest treatment plants in the Soviet Union.

Rice. 1. Scheme of a horizontal sump: 1 - tray; 2 - receiving chamber; 3 - receiving chute; 4 - on the filter; 5 - to remove sediment

Rice. 2. Scheme of a vertical sump 1 - central pipe; 2-tray; 3- outlet pipe; 4 - pipeline for sediment removal

Vertical settling tanks (Fig. 2) are a round in plan, sometimes square, tank with a conical bottom and a central pipe, into which clarified water is supplied from the flocculation chamber.

Upon exiting the central pipe into the sump, the water moves upwards at a low speed and drains already clarified through the side of a concentrically located gutter, from where it is discharged to the filter. The sediment falling to the bottom of the sump is periodically removed.

The water flow rate in the central pipe is taken from 30 to 75 mm/sec. The settling time of water in the sump T = 2 hours. The speed of the upward movement of water is 0.5-0.6 mm/sec.

The diameter of the sump should not exceed 12 m, and the ratio of the diameter to the height of the sump is usually taken no more than 1.5.

Radial settling tanks are round tanks with a slightly conical bottom. Water enters the central pipe and from it is directed in the radial direction to the collection tray along the periphery of the sump. Settling tanks have a shallow depth, the sediment is removed mechanically without disturbing the operation of the settling tank. Radial settling tanks are constructed with a diameter of 10 l * or more at a depth of 1.5-2.5 m (at the wall of the settling tank) to 3-5 m (in the center).

The choice of the type of settling tank depends on the daily capacity of the station, its general layout, terrain, nature of the soil, etc. Vertical settling tanks are recommended for use with a daily capacity of up to 3000 m3. Horizontal settling tanks are used when the station capacity is more than 30,000 m3/day, both in the case of water coagulation and without it.

Radial settling tanks are expedient at high water flow rates (more than 40,000 m3/day). The advantage of these settling tanks in comparison with rectangular horizontal ones is the mechanized removal of sediment without stopping the operation of the settling tank. They are used for high turbidity of river water (with and without coagulation) mainly for clarification of industrial water.

Clarifiers with suspended sludge. The clarification process proceeds much more intensively if the water to be clarified after coagulation is passed through a mass of previously formed sediment, maintained in suspension by current

Rice. 3. Clarifiers: a - original design; b - corridor type: 1 - distribution pipes; 2 - gutters with flooded holes; 3 - working part of the clarifier; 4- protective zone; 5 - outlet tray; 6 - pipe for sediment suction; 7 - precipitation windows; 8-sludge thickener; 9 - pipes for sludge discharge) 10 - pipe for draining clarified water

Such clarifiers provide a higher effect of water clarification than in conventional settling tanks, which is explained by faster coarsening and retention of suspension when coagulated water passes through suspended sediment.

The use of a clarifier with a suspended residue makes it possible, in comparison with a conventional sedimentation tank, to reduce the consumption of coagulant, reduce the size of structures and obtain a higher effect of water clarification.

The clarifier of the original design is a cylindrical tank with a sludge thickener in its central part (Fig. 3, a). Here, the water with the reagent enters the air separator, then passes down into the perforated distribution pipes 1, and then into the holes of the perforated bottom 2.

Water, passing through the layer of suspended sediment 3, enters the clarification zone 4 and overflows into the discharge troughs. An excess of suspended sediment enters the sludge accumulator 5, from where it is periodically removed to the sewer.

The corridor-type clarifier (see Fig. 3, b) is a rectangular tank. The coagulated water enters the clarifier through pipe 1 and is distributed through perforated pipes 2 in the lower (working) part 3 of the clarifier. The speed of water movement in the working part should be such that the coagulant flakes are in suspension. This layer contributes to the retention of suspended particles. The degree of water clarification is much higher than in a conventional sump.

Above the working part there is a protective zone 4, where there is no suspended layer. Clarified water is discharged by tray 5 and pipes 10 for further processing. Excessive amount of sediment by suction into pipe 6 is discharged through windows 7 to sediment thickener 8, where the sediment is compacted and periodically discharged into the sewer through pipes 9.

The ascending flow rate in the working part of the clarifier is assumed to be 1-1.2 mm/sec.

Water softening methods.

The removal of hardness salts from water, i.e. its softening, must be carried out to feed boiler plants, and the hardness of water for medium and low pressure boilers should be no more than 0.3 mg.eq / l. Softening water is also required for such industries as textile, paper, chemical, where water should have a hardness of not more than 0.7-1.0 mg.eq / l. Softening of water for household and drinking purposes is also advisable, especially if it exceeds 7 mg.eq / l.

The following main methods of water softening are used:

1) reagent method. - by introducing reagents that contribute to the formation of poorly soluble calcium and magnesium compounds and their precipitation;

2) cationite method, in which softened water is filtered through substances that have the ability to exchange the cations (sodium or hydrogen) contained in them for calcium and magnesium cations, salts dissolved in water. As a result of the exchange, calcium and magnesium ions are retained and sodium salts are formed that do not give water hardness;

3) the thermal method, which consists in heating water to a temperature above 100 °, while carbonate hardness salts are almost completely removed.

Often, softening methods are used in combination. For example, some of the hardness salts are removed by the reagent method, and the rest by cation exchange.

Of the reagent methods, the soda-lime softening method is the most common. Its essence is reduced to obtaining instead of Ca Mg salts dissolved in water insoluble salts CaCO 3 and Mg(OH) 2 precipitating.

Both reagents - soda Na 2 C0 3 and lime Ca (OH) 2 - are introduced into the softened water simultaneously or alternately.

Salts of carbonate, temporary hardness are removed with lime, non-carbonate, constant hardness - soda. chemical reactions when removing carbonate hardness proceed as follows:

Ca (HC0 3) 2 + Ca (OH) 2 \u003d 2 CaCO 3 + 2H 2 0.

In this case, calcium carbonate CaCO3 precipitates. When magnesium bicarbonate Mg (HC0 3) 2 is removed, the reaction proceeds as follows:

Mg (HCOa) 2 + 2Ca (OH) 2 \u003d Mg (OH) 2 + 2CaCO 3 + 2H 2 0.

Magnesium oxide hydrate Mg(OH) 2 coagulates and precipitates. To eliminate non-carbonate hardness, Na 2 C0 3 is introduced into the softened water. The chemical reactions when removing non-carbonate hardness are as follows:

Na 2 C0 8 + CaS0 4 \u003d CaCO 8 + Na 2 S0 4;

Na 2 CO 3 + CaCl 2 \u003d CaC0 3 + 2NaCl.

As a result of the reaction, calcium carbonate is obtained, which precipitates.

For deep softening, auxiliary measures are used, such as heating the treated water to about 90, while the residual hardness can be increased to 0.2-0.4 mg.eq / l.

Without heating, water treatment is carried out with large excess doses of lime, followed by removal of these excesses by purging the water with carbon dioxide. The last process is called recarbonization.

On fig. 4 shows a diagram of a reagent water softening plant, which includes a device for preparing and dosing reagent solutions, mixers, reaction chambers, clarifiers, and filters.

To soften uniformly supplied water that flows continuously, the same soda and lime solution dispensers are used as in coagulation. If the flow of softened water fluctuates, so-called proportional dispensers are used.

Rice. 4. Scheme of reagent water softening: 1 - reaction chamber (vortex reactor); 2 - clarifier; 3 - quartz filter; 4 - mixer; 5, 6 and 7 - dispensers of reagent solutions; 8, 9 and 10 - tanks for dissolving coagulants and soda for making milk of lime; 11 - tank; 12 - pump; 13 - air separator.

The soda-lime method is suitable for softening water with any ratio of carbonate and non-carbonate hardness.

The disadvantages of the soda-lime softening method are as follows: 1) the water is not softened completely; 2) installations for softening bulky; 3) a careful dosage of soda and lime is necessary, which is difficult to achieve due to the inconstancy of the composition of the softened water and reagents.

The cationic softening method is based on the ability of substances called cationites to exchange the sodium cations Na + or hydrogen H + contained in them for calcium or magnesium cations dissolved in water. In accordance with this, sodium-cationite and hydrogen-sodium are distinguished: cationite methods of water softening.

With the help of cation exchangers, water is softened in an installation consisting of several metal pressure tanks loaded with cation exchange resin (Fig. 5).

Raw water enters the filter through pipes A, B and C; softened water is released through pipe G. When the filter is operating, valves 2 and 5 are open, and the rest (1, 3, 4 and 6) are closed. Wash the filter before regeneration.

To wash the filter, water from tank D is supplied through pipe E and passes through drains from bottom to top. The duration of washing is 20-30 minutes, the intensity is 4-6 l / s per 1 m2. Rinse water from the filters is discharged through pipes C, B, G, with valves 4 and 3 open, and the rest closed.

The regenerating solution of the cation exchanger during regeneration is supplied through pipe B, passes the filter from top to bottom and is discharged through the pipe. In this case valves 1 and 6 are open, the rest (2-5) are closed; the duration of regeneration is about 30-60 minutes, and washing from the regenerating solution is 40-60 minutes.

Rice. 5. Diagram of a cationic water softener

The advantages of the cationite method are as follows: 1) the water softens almost completely; 2) only the solution needs to be dosed table salt or sulfuric acid; 3) filters are manufactured in a factory way. The disadvantages of this method include the need for preliminary clarification of water, since colloidal and organic substances envelop grains of cation exchangers and reduce their exchange capacity.

Reagents used in water treatment are introduced into the water in the following places:

a) chlorine (with preliminary chlorination) - into the suction pipelines of the pumping station of the first lift or into the conduits supplying water to the treatment station;

b) coagulant - into the pipeline before the mixer or into the mixer;

c) lime for alkalization during coagulation - simultaneously with the coagulant;

d) activated carbon to remove odors and tastes in water up to 5 mg/l - before filters. At high doses, coal should be introduced to the pumping station of the first lift or simultaneously with the coagulant into the mixer of the water treatment plant, but not earlier than 10 minutes after the introduction of chlorine;

e) chlorine and ammonia for water disinfection are introduced before treatment facilities and filtered water. In the presence of phenols in the water, ammonia should be introduced both during preliminary and final chlorination.

The coagulant solution is prepared in solution tanks; from where it should be released or pumped into service tanks. To supply a given amount of coagulant solution to the water, it is necessary to provide for the installation of dispensers.

When using automatic dispensers based on the principle of changing the electrical conductivity of water depending on impurities, lime for alkalization should be introduced after the selection of coagulated water going to the dispenser.

Special types of water purification and treatment include: desalination, desalination, iron removal, removal of dissolved gases from water and stabilization.

Mechanism of action of IOMS inhibitors.

When water is heated during the operation of the heating system, the thermal decomposition of the bicarbonate ions present in it occurs with the formation of carbonate ions. Carbonate ions, interacting with calcium ions present in excess, form the embryos of calcium carbonate crystals. More and more carbonate ions and calcium ions are deposited on the surface of the nuclei, as a result of which crystals of calcium carbonate are formed, in which magnesium carbonate is often present in the form of a substitutional solid solution. Settling on the walls of heat engineering equipment, these crystals coalesce, forming scale (Fig. 6, a).

The main component providing the antiscale activity of all the considered inhibitors are organophosphonates - salts of organic phosphonic acids. When organophosphonates are introduced into water containing calcium, magnesium and other metal ions, they form very strong chemical compounds - complexes. (Many modern inhibitors contain organophosphonates already in the form of complexes with transition metals, mainly with zinc.) Since one liter of natural or industrial water contains 1020–1021 calcium and magnesium ions, and organophosphonates are introduced in an amount of only 1018–1019 molecules per liter of water, all molecules of organophosphonates form complexes with metal ions, and complexons as such are not present in water. Complexes of organophosphonates are adsorbed (precipitated) on the surface of calcium carbonate crystal nuclei, preventing further crystallization of calcium carbonate. Therefore, when 1–10 g/m3 of organophosphonates are introduced into water, scale does not form even when very hard water is heated (Fig. 6b).

Complexes of organophosphonates can be adsorbed not only on the surface of crystal nuclei, but also on metal surfaces. The resulting thin film hinders the access of oxygen to the metal surface, as a result of which the metal corrosion rate decreases. However, the most effective metal protection against corrosion is provided by inhibitors based on complexes of organic phosphonic acids with zinc and some other metals, which were developed and put into practice by Professor Yu.I. Kuznetsov. In the surface layer of the metal, these compounds can decompose with the formation of insoluble compounds of zinc hydroxide, as well as complexes of a complex structure, in which many zinc and iron atoms participate. As a result of this, a thin, dense film is formed that is firmly adhered to the metal and protects the metal from corrosion. The degree of metal protection against corrosion when using such inhibitors can reach 98%.

Modern preparations based on organophosphonates not only inhibit scale and corrosion, but also gradually destroy old deposits of scale and corrosion products. This is explained by the formation of surface adsorption layers of organophosphonates in the scale pores, the structure and properties (for example, thermal expansion coefficient) of which differ from the structure of scale crystals. The fluctuations and temperature gradients arising during the operation of the heating system lead to wedging of crystalline scale aggregates. As a result, the scale is destroyed, turning into a fine suspension, which is easily removed from the system. Therefore, when introducing preparations containing organophosphonates into heating systems with a large amount of old deposits of scale and corrosion products, it is necessary to regularly drain sediment from filters and sumps installed at the lowest points of the system. The sludge should be drained, depending on the amount of deposits, 1–2 times a day, at the rate of feeding the system with clean, inhibitor-treated water in the amount of 0.25–1% of the water volume of the system per hour. It should be noted that with an increase in the concentration of the inhibitor above 10–20 g/m3, the scale is destroyed with the formation of very coarse suspensions that can clog the bottlenecks of the heating system. Therefore, an overdose of the inhibitor in this case threatens to clog the system. The most effective and safe cleaning of heating systems from old deposits of scale and corrosion products is achieved by using preparations containing surfactants, for example, the KKF composition.

a) b)

Rice. 6. Section of the intra-quarter 89 mm hot water pipeline:

a - after two years of operation on water with a hardness of 8–12 meq/dm3;

b - six months after the start of water treatment with an IOMS-1 inhibitor.

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