Coagulation methods are quite well developed and are widely used at many water treatment plants. At the same time, the use of coagulants gives rise to additional water problems that must be eliminated by other purification methods:
- increased turbidity;
- low efficiency of removal of dissolved organic matter;
- high residual aluminum concentration.
To eliminate many of the shortcomings of the coagulation method, the reagent aluminum oxychloride ( OXA), which is used in water purification instead of the more traditional aluminum sulfate ( SA) ‒ Al₂(SO₄)₃. The formula of aluminum oxychloride in general looks like this:
Al n (OH) m Cl 3n-m
Applications of aluminum oxychloride as a coagulant allowed not only to reduce the amount of the reagent, but also to significantly improve the quality of purified water. The maximum effectiveness of OXA is observed when discoloring turbid waters, with indicators on the color scale of 30-50 degrees; as well as during the cold period of the year, when the rate of coagulation slows down.
Applications of aluminum sulfate more beneficial for purifying water with low turbidity and low salt content. It is not advisable to use aluminum oxychloride to prepare water of this type.
The reason for the different effectiveness in purifying water with different turbidity and color indicators is that the extraction of pollutants occurs in different ways.
The efficiency and speed of the process of water decolorization by coagulation depends on the following properties:
- temperature,
- pH and ionic composition,
- suspended solids content,
- concentrations of colloidal particles and truly dissolved organic matter.
Despite the fact that the reaction of the environment pH value, plays a significant role in the course of physical and chemical processes of water purification; in the conditions of water treatment plants, this indicator is almost never monitored. The pH indicator is controlled only within the framework of SanPiN standards for water. Changing and monitoring the reaction of the environment to monitor optimal conditions for the occurrence of coagulation processes at existing stations is not carried out.
An indicator of the progress of a reaction can be degree of dissociation aluminum hydroxide, which is minimal in an environment close to neutral (pH 6.5–7.5). Colloidal particles of aluminum hydroxide in such an environment are neutral (do not carry a charge).
When carrying out decolorization and clarification processes with aluminum sulfate, the optimal pH at which aluminum hydroxide will form and precipitate is 6.7–7.0. Such a medium is characterized by sorption and aggregation processes. Aggregation of colloidal particles of organic origin and mineral suspensions into flakes occurs with the participation of hydroxide, which plays the role of a binder.
Intensity of floc formation also depends on the pH value - after all, the content of hydrogen ions and hydroskid ions in the solution affects the structure of substances - hydrolysis products.
In an environment with pH, aluminum polycations:
These substances have a large positive charge, due to which they will be adsorbed on the surface of colloidal particles with a negative charge. This property becomes important for reducing the color of water. If coagulation processes go in this direction, then at pH>7 the quality of water decolorization will deteriorate. The optimal pH values of the medium while maintaining the quality of cleaning are 5-6.
The mechanisms of coagulation of organic humus have common features with the processes of purification from mineral substances, but with some differences.
Natural water with a pH of 5–8 when treated with a coagulant (aluminum sulfate) demonstrates the following processes:
- The mechanism of neutralization-adsorption coagulation: in this case, dissolved aluminum hydroxo complexes, which have a positive charge, combine with negatively charged contaminant particles. Humus particles coagulate as their negatively charged functional group (phenolic, ketone, carboxyl) interacts with positive particles - aluminum hydrocomplexes. Polymer complexation occurs.
- Mechanism of entrapment coagulation. According to this mechanism, turbidity decreases due to the adsorption of coagulant hydrolysis products on the surface of mineral particles. The ion charges are neutralized, the repulsive forces are reduced, and the double layer is compressed.
The mechanism of entrapment coagulation occurs at a pH above 7 due to the adsorption of humic substances on Al(OH)₃ particles.
The turbidity of water is reduced due to the enveloping of mineral particles with a newly formed mass of aluminum hydroxide. To make entrainment coagulation possible, it is necessary to add a large amount of coagulant to form a significant volume of aluminum hydroxide precipitate.
The first mechanism described (neutralization-adsorption coagulation) is also possible with small doses of the coagulant, but the dose must increase in proportion to the increase in the content of colloidal polluting particles.
If the water is very cloudy, then it makes sense to carry out coagulation at elevated pH values. In this case, the reactions of hydroxide formation will prevail over the mechanisms of adsorption of positive ions of the coagulant.
The presence of mineral particles accelerates the precipitation of aluminum hydroxide and intensifies the formation of coagulation nuclei. Humic substances are quite stable and convey this stability when interacting with hydroxides. In this case, the coagulation process may stop and not reach completion.
The stability of humic colloids increases with the pH value of the treated water. With a decrease in pH and an increase in the acidity of the environment, the stability of humic substances decreases. The adsorption of coagulant cations also makes its contribution, and the coagulation process improves.
It follows that it is advisable to purify colored waters at low pH values. The adsorption of aluminum cations gives humic colloids the property of active flocculation even without the presence of aluminum hydroxide in water. This is how humates fundamentally differ from suspended substances, and this fact should be taken into account when choosing a coagulant for purifying water from color.
Purification of water with high color and low turbidity balances between these two mechanisms. Which of the coagulation processes in the solution will prevail is determined by the qualitative composition of the source water.
As the color of water increases, the optimal pH value decreases with increasing concentration of hydrogen ions. It is especially important to meet the conditions for coagulation if water needs to be purified from fulvic acids, which are usually more difficult to remove from water than humic acids.
For the purification of colored waters with low salt content, the optimal reaction range of the medium is quite narrow. To do this, it is necessary to achieve a pH at which humic substances are removed from the solution with the smallest added dose of coagulant.
The intensity of coagulation processes during the purification of colored waters is also influenced by the presence of certain ions included in the coagulant. The greatest coagulating bleaching effect is inherent in sulfate anions.
These ions influence the course of many chemical processes:
- influence the formation of poorly soluble complex compounds;
- increase zones of optimal pH values (in the direction of increasing the acidity of the environment);
- reduce the dose of coagulant.
The improvement in water bleaching processes can theoretically be explained by the fact that sulfate anions serve as counterions for positively charged particles - products of the hydrolysis reaction in an acidic environment (at pH
If aluminum sulfate is used as a coagulant, then the effect of anions stimulating the coagulation process is as follows:
PO₄³⁻ > SO₄²⁻ > Cl⁻ > HCO⁻
As the pH value increases (the acidity of the medium decreases), Cl⁻ ions also tend to form insoluble aluminum hydroxide compounds. But if the water has low pH values (low alkalinity), then an increase in the chloride content leads to stabilization of the coagulation process and the cessation of the formation of aluminum hydroxide flakes. If bicarbonate ions HCO³⁻ are present in water, then the hydrolysis of the coagulant (aluminum sulfate) occurs more intensely and over a wider range of pH values than in the presence of alkaline hydroxide ions OH⁻.
If the salt content of the purified water is soft, and the content of bicarbonates in it is low, then in this case the reaction of hydroxide formation does not proceed completely, the coagulation-discoloration processes worsen, flocculation decreases, and the concentration of residual aluminum increases. For these reasons, water is made alkaline to improve discoloration.
The transition of colloidal hydroxide to hydroxide can be difficult because there are substances in water called protective colloids. Another reason is the increased alkalinity of the water, since aluminum hydroxide is converted into dissolved substances in an alkaline environment.
In turbid water with a high content of humic acids, the latter interact with aluminum hydroxo complexes. Due to this, the calculated increase in acidity from the addition of a coagulant exceeds the actual values. The residual alkalinity of water is 0.1–0.2 mg-eq/l.
Due to the stabilization of colloidal particles, coagulation may not proceed uniformly. This is important to consider when choosing a coagulant reagent - aluminum sulfate or aluminum oxychloride. If aluminum sulfate is used to clarify and discolor water, the optimum pH and minimum excess alkalinity are achieved with less coagulant than when using oxychloride.
If the purified water is pre-alkalinized (by adding soda), the residual alkalinity increases from 0.1 to 0.45 mEq/l (with aluminum sulfate) and from 0.5 to 0.8 (with aluminum oxychloride). At the same time, the values of water color and content change. residual aluminum: with aluminum sulfate the values decrease, with oxychloride they increase.
To implement the neutralization-adsorption coagulation mechanism for maximum removal of humic substances, it is necessary to strictly maintain the optimal pH range - both for sulfate and aluminum oxychloride as coagulants.
If pH>7.5, the rate of aluminum hydroxide formation increases, which can theoretically be explained based on the mechanism of entrapment coagulation. At the same time, the doses for both coagulants increase, but the cleaning efficiency of OXA is higher than with SA.
As theoretical studies of coagulation and practical experience in water decolorization show, at low values of pH, alkalinity and salt content (water softness), aluminum sulfate is more suitable for purification. It is used to purify water with high color and low turbidity. In other cases, the use of aluminum oxychloride as a coagulant is justified.
In practice, it turned out that water from some natural sources can vary significantly in quality throughout the year. Therefore, depending on the parameters of the source water, both coagulants - SA and OXA - can be used to decolorize and clarify it. Sometimes the best results are obtained by joint treatment of water with both coagulants - SA and OXA.
The content of residual aluminum cannot be reduced only through the use of aluminum oxychloride, because water differs in its composition and quality. When using OXA to decolorize turbid water, the content of residual aluminum is less than when treating with CA. But when treating colored water, the result is greatly influenced by the pH of the treated water. Since the optimal pH and alkalinity ranges for both coagulants differ little, slight fluctuations in conditions can significantly change the effectiveness of one or the other coagulant.
The choice of a coagulant for a specific water source should be made taking into account water parameters in all seasons of the year:
- chromaticity,
- permanganate oxidation,
- residual aluminum.
For aluminum oxychloride, the decisive factor is basicity index, calculated by the formula:
/ 3 100%
Practical studies have shown that the quality of bleached water, as well as the added dose of the coagulant reagent, directly depend on the brand and basicity of aluminum oxychloride.
Highly basic OXA used to purify turbid water with medium color and low concentration of organic matter. As the water temperature decreases, the basicity of the coagulant should also increase.
A decrease in the basicity of aluminum oxychloride should occur following an increase in water color and an increase in permanganate oxidation.
Low basic OXA or aluminum sulfate as a coagulant are used to purify water that requires compliance with special pH conditions - this applies to water with high color and low salt content.
Clarification by settling to reduce turbidity is more effective with the highly basic coagulant OXA, and when using aluminum sulfate, the turbidity of the filtrate is reduced. The indicator of residual aluminum changes according to the same pattern. More effective removal of organic matter - in terms of permanganate oxidation - occurs when using aluminum sulfate.
Application mixed coagulants complex nature for the decolorization of colored waters provides expanded capabilities. Mixed coagulants include:
- n- aluminum polyoxysulfate;
- n- aluminum polyoxychlorosulfate;
- n- aluminum polyoxychloride;
- aluminum-silicon coagulants-flocculants.
Conclusions on the article
- The selection of a coagulant is carried out experimentally, depending on water quality indicators in each of the four periods of the year.
- Discoloration and clarification of colored low-turbidity water with low alkalinity and low salt content is carried out at a pH not higher than 7.5. For such water, aluminum sulfate is more preferable as a coagulant. At low temperatures, it is possible to use aluminum oxychloride and aluminum sulfate together. Aluminum sulfate removes organic contaminants better, which is confirmed by changes in color and permanganate oxidation values. The use of OXA during bleaching reduces the concentration of residual aluminum.
- The rate of floc formation is affected by changes in the concentration of sulfate ions in water.
- With the correct pH range, the quality of water purification increases even when using OXA.
- The use of highly basic OXA must be justified. At high concentrations of organics in water, it is more effective to use aluminum sulfate or CA and OXA together. To reduce the color of water, it is promising to use mixed coagulants - aluminum polyoxysulfate or polyoxychlorosulfate.
- Changing the concentration of working solutions of coagulants makes it possible to indirectly regulate the process of water bleaching. The formation of aluminum hydrocomplexes affects the intensity of purification from colloidal pollutants and, ultimately, improves the quality of water treatment. As the water temperature decreases, the concentration of the coagulant working solution should also decrease.
Argel
In addition to ordinary water, there is also waste water. They appear as a result of rinsing; these are waters that are used several times. The same waste, after the restoration of ion exchange cartridges, can also be safely called wastewater. Such liquids have a high amount of harmful impurities in their composition. And it won’t be possible to just dump them into the atmosphere. You can poison an entire city. That’s why there is a whole section among water purifiers that deal specifically with wastewater. And this is where we found ourselves coagulants for water.
Types of water for coagulants
In general, coagulants for water purification are used not only for water, but also for ordinary water, when it is required to purify it in a special way to obtain certain characteristics. But since there is more use in wastewater, it won’t hurt to understand the types of such water.
The classification of dirty water can be divided into groups:
- · By source;
- · By type of pollution;
- · By stage of contamination
All types of wastewater, when divided into groups, can be presented in the form of a table.
That is, there are many options for wastewater alone.
Water generated by household waste is water in toilets, sinks, in general, everything that the consumer then flushes away. Washing or washing dishes is all waste water. This type of water is also available in factories. Everything that is used for cooling, to stimulate any reactions, is all harmful industrial water.
What then refers to atmospheric pollution? This is any water formed by rain, snow, flowing from roofs, even water from sprinklers will already be waste. Because she was clearing garbage from the pavements.
Biological impurities include worms, worm eggs, viruses, and even tremors. Effluents can be heavily polluted or conditionally polluted. In general, you can’t just release such water into the atmosphere. They can easily poison the entire atmosphere, lead to the development of bacteriological epidemics, etc. This is why it is so important to use water coagulants before the water is released into the production system or disposed of in the nearest lake.
The use of special substances - coagulants in water purification
With so much pollution in wastewater, it is clear that the issue of cleaning it is not just a question, it is a problem that requires an immediate solution. Water coagulants are such a powerful purifying agent that they can sometimes help bring water to a state where it can be reused, for example, in closed production cycles.
Depending on what cleaning reagents are needed for, they are divided into groups for industry and for domestic needs.
So, coagulants for water purification. There are some nuances here, because... water for swimming pools must be both clean and neutralized at the same time. A large number of people bathe in this water, everyone has sweat, pieces of skin, etc. Therefore, it is necessary to neutralize all these feces, but not to poison people.
The pump in the pool works for circulation, not filtration, so that the water does not stagnate. All impurities, under the influence of coagulants, settle at the bottom and are sucked out by a pump or eliminated through a filter. Before mixing water with the reagent, its acidity must be determined. If the threshold is high, then together with coagulants such water can form toxic substances.
Coagulants do what they do to speed up or create a reaction. As a result, its small particles of impurities combine and settle to the bottom. By filtering the water in the pool, a secondary purified liquid is obtained, which can be discharged into the atmosphere or used in a closed circulation process.
Aluminum chloride
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Examples of such substances include aluminum sulfate, aluminum chloride. This is not all; chloride compounds are more likely to be used for swimming pools. Very often, such substances are used in pulp production, where equipment constantly needs to be cleaned, and the water after these processes becomes harmful.
Aluminum chlorides are the most used coagulants for water resources today. They are not such old substances; their industrial production began relatively recently, at the end of the twentieth century.
Aluminum hydroxychloride
Another progressive reagent - aluminum hydroxyl chloride. This is a more productive form. Easily and efficiently removes turbidity in water. With such a substance, the level of acid-base balance does not need to be adjusted. The flakes form well without such adjustments.
Also, hydroxide chloride will help remove the color of the water; the rate of formation of flakes is much higher than that of ordinary hydroxide. Another plus is the elimination of heavy metal ions. That is, the reagent works on several fronts at once. The output is water with fewer impurities of aluminum salts and chloride compounds.
By the way, some coagulant aluminum hydroxyl chloride is also used if the primary water is too contaminated.
Thus, harmful substances in the form of coagulants can be very useful if they are used correctly and in the right quantities. Then the water will be both purified and disinfected at the same time and thanks to one stage of purification, instead of several.
The most popular segment in the coagulant market is occupied by aluminum salts – sulfate and oxychloride. Aluminum sulfate is much more common on the territory of the Russian Federation - in the 20th century it was the only substance used for water purification. Since then, the situation on the coagulant market has changed slowly - now the share of “innovative” aluminum oxychloride does not exceed 20%. In Western European countries this figure exceeds 90%.
Aluminum oxychloride has significant advantages:
- high coagulation rate, especially at low temperatures (which, you see, is very important for our climate);
- lower dosage of coagulant;
- low content of residual aluminum in water after purification.
To this we can add an unlimited shelf life and the ability to “adjust” the coagulant to any type of water - by varying the basicity.
Factors of distribution of aluminum sulfate
Despite the advantages of aluminum oxychloride, aluminum sulfate still remains the most common substance for water purification in Russia. Among the factors of its spread are the following:
1. Stable performance indicators. Water utilities, especially in smaller cities, have a long and successful history of using aluminum sulfate, without feeling the need to change many years of experience.
2. Aluminum oxychloride is more expensive. The advantages of its use will be visible after a few years - this includes a reduction in dosage, improved water quality, a significant reduction in equipment wear, and no need to use flocculants (additives that increase the efficiency of coagulation).
3. Presence of counterfeit products. Low-quality products distributed by unscrupulous suppliers can lead to a decrease in interest in the use of aluminum oxychloride in general. The raw material for the production of aluminum oxychloride can be aluminum hydroxide, as well as primary and secondary aluminum. If the quality of primary aluminum cannot be an issue, then secondary aluminum may contain additional impurities, including impurities of heavy metal ions, as well as any of the elements of the periodic table.
This area of our work is devoted not only to popularizing the use of aluminum oxychloride for water purification, but also to the development of regulatory documentation to combat low-quality products.
The Aluminum Association is interested in ensuring that end users of water can use and drink clean, quality water and intends to make every effort to contribute to this goal.
Drinking clean water improves human health and immunity, and the body itself recovers using its own reserves. From time immemorial, people have settled near rivers and lakes, using the sources that nature provided for life. The most ancient civilizations already knew how to purify water for the needs of citizens by passing it through layers of clay and sand. In those days, people did not use coagulants (these are substances with which the primary purification of life-giving moisture is carried out today).
Such different clean water
In the modern world, it is believed that ideally a person should use three types of water in their homes:
- tap water, which has undergone standard repeated rough cleaning and filtration in special settling tanks;
- household, pre-softened to prevent the formation of scale in heating devices, used for washing and washing;
- drinking, used exclusively for oral consumption and cooking.
The apartment is provided with regular water by the city water supply system. For independent home purification, various filters, structuring systems and some minerals recognized as useful (for example, shungite) are used. In addition, there are coagulants that disinfect water for home use.
What happens to water before it enters the pipes?
Before settling and filtration, preliminary coarse purification of water intended for supply to city water supply networks is carried out. First, water and coagulants (these are special chemical reagents) are quickly mixed in special containers. During coagulation, the electrostatic repulsion of particles dissolved in water decreases and they stick together. This makes cleaning easier and faster during settling and filtration.
The process in one tank should last about one minute. With a shorter time interval, the required uniformity of mixing of the substance with water is not ensured. With longer interaction, the formed flocs (sediment, stuck together foreign particles) may be destroyed. After passing through several tanks, where water coagulants are mixed with it at a gradually decreasing speed, the liquid undergoes settling.
What does the beautiful word “flocculation” mean?
Coagulants are chemical reagents. Not all substances harmful to humans can be removed by conventional filtration in a short time. Some of them are in a dissolved state. If there are impurities or hydrosols in the water, then coagulants for water purification at the moment of interaction form an insoluble precipitate in the form of a suspension with them. The process of formation of sticky, larger “heaps” from fine particles is called flocculation. These new particles can reach several millimeters in size.
Of course, it is possible to purify water from various impurities by conventional filtration, but this will take several years, but water is needed every day in huge quantities. In order for the cleaning process to proceed quickly enough, coagulants are added to the mixers. This reduces the time it takes to free water from unnecessary harmful substances to just 30-45 minutes. Thanks to this acceleration, residents of large and small cities have the opportunity to uninterruptedly use water without leaving their homes.
What happens at wastewater treatment plants
Water, even if it is clear at first glance, usually contains a huge amount of impurities. These may include the following substances:
- gypsum and chalk;
- sand and clayey rocks;
- silt and plankton;
- sparingly soluble metal hydroxides;
- bacteria;
- dissolved chemicals;
- various suspensions.
Heavy and large particles with a high specific gravity sink quite quickly to the bottom of the settling tank, in 1-2 minutes. By accelerating the process of sedimentation (sediment formation) of small particles, which can last up to two years, coagulants are added to the water. These are alumina sulfate, iron sulfate, aluminum hydroxosulfates and hydroxochlorides, mixtures of iron and aluminum salts, clay opacifiers, various flocculants and suspension clarifiers.
To purify and clarify water in a system of vertical sedimentation tanks, 50 to 100 ml of reagents are consumed per 1 liter. Enlarged and glued together under the influence of chemicals precipitate, which is easily separated by further settling and filtration.
For those who just want to get clean water, without diving into the essence of the process, let’s say one thing: purchase a high-quality coagulant from a well-known brand and strictly follow the instructions. This is all. For those who are interested in knowing how coagulation occurs, what its chemical and physical characteristics are, this article is useful. In simple language and in an accessible form, we will tell you how various coagulants work. And at the same time, we will recommend you the most effective and efficient means that have received the most positive consumer reviews.
What kind of chemistry is this - the reader will ask, the answer is simple: coagulants. This substance is used to purify water from suspended particles. There are different ways to purify wastewater from impurities: filtration, sedimentation, chemical treatment, electrical treatment, heat treatment.
These methods have found application in various industries, but the most common and effective of them can be considered filtering And chemical treatment.
The particle size of suspended matter in water can be so small that filtration becomes either impossible or too expensive. In some cases, it is necessary to increase costs, but most often this measure turns out to be unprofitable. For example, the owner is unlikely to want to spend money on a special treatment facility, but a regular filter does not cope with the task as successfully as required, so the owner will have to “help” a little with the help of modern chemistry.
“What kind of chemistry is this?” - the reader will ask. The answer is simple: a coagulant. This substance is used to purify water from suspended particles.
Coagulation is a special process that can be described by the word consolidation. That is, when a certain substance is added to the composition of turbid dirty water, all the particles that float in it and create turbidity will begin to unite into larger agglomerations, and, in the end, will become large enough to settle in the form of flakes and be filtered.
Different types of coagulants are used in different areas of the economy and everyday life. They can be divided into two large groups: mineral And organic.
Important! Organic coagulants are more expensive and are most often used to purify drinking water. They demonstrate slightly better performance than inorganic compounds, however, their use is often less cost-effective.
In the case of cleaning industrial wastewater, various coolants and circulating media, swimming pools and reservoirs, inorganic coagulants are used:
- Ferric chloride. Strong corrodant and toxin, used in industry.
- Ferrous sulfate. It is used in industry for wastewater treatment, in public utilities for water treatment, and also in medicine to stop bleeding.
- Aluminum sulfate. Suitable for purifying drinking, household and technical water for various purposes.
- Aluminum oxychloride. This salt - hydroxochloride - is good for treating wastewater, tanks, swimming pools, and ponds.
- Aluminum hydroxychlorosulfate. This is a mixture based on aluminum sulfate. It is an excellent preparation for treating dirty flood waters at temperatures below +12˚ C.
These substances are distinguished by their relatively low price, availability, safety and ease of use.
The work of a coagulant: the essence of the process
The chemistry of the coagulation process covers a wide field of scientific knowledge, the understanding of which will require a certain level of special training. We will skip the pseudo-scientific details and try to convey the essence.
How coagulants work 1 
How coagulants work 2 
How coagulants work 3 So, we have a certain volume of water contaminated with colloidal particles. These particles are so small that a sand filter passes them through. Moreover, their sizes are so small that they cannot settle to the bottom: the Brownian motion of molecules makes these particles constantly remain in suspension.
Attention! Once again: tiny specks float in the water and look like mud. They pass through the filter and do not settle to the bottom, since water molecules continuously “push” them from different sides, setting them in motion. As a result, it is impossible to filter the water or settle dirt to the bottom.
Not only do these particles not settle or be filtered, they also refuse to clump together into larger formations. This is due to the fact that they have the same charge and repel each other as a result of electrostatic interaction forces.
Here we come to the essence of the coagulation process: after introducing a special reagent, the properties of the particles change, they lose their charge, and the suspension begins to stick together into larger lumps. As a result of eliminating the effect of electrostatic repulsion, the particles come close enough for the attractive force to begin to act.
The approach is also hampered by the spatial volume of molecules or atomic groups, which, being in close proximity to the reacting atoms in the molecule, may prevent these atoms from coming together and reacting. This effect is neutralized by the addition of salts and changes in the acidity of the medium.
As a result, coagulants do not change the chemical composition of impurities or water. The main characteristic they target is particle size. After adding, say, ferric chloride, the individual corpuscles lose their charge and begin to clump together into flakes, which can then be collected or filtered.
Important! The essence of the coagulation process is to make the smallest particles large enough for them to settle to the bottom or be retained by a filter. This is the shortest and simplest explanation.
Who makes the best coagulants: production and distribution
Manufacturers of coagulants make up a solid list, their number has grown recently and amounts to more than 15 throughout the country. For comparison: there were only 12 production facilities throughout the entire territory of the former Soviet Union. Modern Russia meets 95% of its needs for coagulants through domestic production.
Inorganic drugs are produced in the Russian Federation. This happened due to the economic realities of the time the plants were built and a certain configuration of the raw material base characteristic of our country. Historically, the first place is occupied by the preparation of aluminum-based coagulants, namely aluminum oxychloride and sulfate, as well as sodium aluminate.
Let's look at their differences:
As follows from the table, sodium aluminate gives the highest concentration of aluminum oxide, which means that this solution will show the highest activity in the process of purifying water from suspended matter. At the same time, the density of impurities is also the highest, which means that after treatment, excess components may remain in the water. Following similar logic, we will come to the conclusion that the most acceptable option would be aluminum oxychloride (other names: aluminum chlorohydroxide, OXA, polyaluminum hydrochloride), which demonstrates the optimal ratio of aluminum content and impurities.
Important! The selection of a specific substance is made based on the purpose of the water, the degree of its contamination, temperature and method of purification. OXA is used to purify cold water with a high content of organic impurities of natural origin.
One of the most common is aluminum oxychloride. This substance works especially well at low water temperatures, within +10 ˚С, and removes organic impurities well. It is OXA that is contained in most modern pool coagulants.
The procedure for using coagulating agents to clarify pool water
First, we will tell you what to do if you have modern equipment:
- We calculate the dose based on the volume and degree of contamination of the tank.
- We pour the required volume of liquid into the skimmer and wait until it disperses the product throughout the pool.
- Turn off the pump and give the drug time to react within 15 - 30 minutes.
- We collect the sediment that has fallen to the bottom using a water vacuum cleaner or a submersible pump.
- We turn on the pump again and perform final filtration.
The calculation of the coagulant is a separate topic; it is believed that this is something from the category of higher mathematics. Indeed, if we want to purify drinking water on a conveyor basis, we will have to very accurately calculate the consumption of the chemical, otherwise it will accumulate and poison the water. In the case of a swimming pool, everything is much simpler.
Important! Usually the manufacturer indicates on the label how to use the drug. If this is not the case, then you can use the average values for each specific substance. For OXA, these values range from 20 to 50 ml of the drug per ton of water.
For those who have a homemade pool installed or a pool without special additional equipment
- We determine the required amount of agent, for this we calculate the volume of the pool in cubic meters, and for each cube we add from 20 to 50 ml of OXA (GOODHIM "").
- We first dilute the coagulant in a watering can with water in a ratio of 1:5 – 1:100, that is, we take about two liters.
- Turn off the pump with filter.
- We go down into the pool and begin to walk in circles until the water forms a small whirlpool.
- We leave the pool and add the prepared solution to the whirlpool.
- We wait, then we collect the sediment and finally filter the remaining water.
Timely care and cleaning make using the pool not only enjoyable, but safe and even healthy. Now you can invite your friends to join the water procedures without fear of being embarrassed by the state of the water in the tank.
Attention! Most modern manufacturers have websites where you can find contacts or delivery information. Most often, it is possible to order a product online and receive it by mail within a few days.
Conclusion
Water is a critical element for sustaining life. This applies to drinking, personal hygiene, watering plants, economic activities and production. Coagulation solved the issue of water purification and brought this process to a completely different qualitative level, and today coagulants are used almost everywhere.
Coagulants - Definition and Frequently Asked Questions
- What does coagulant mean? The word comes from the Latin “coagulatio” and is translated as “thickening”. Coagulant substances are capable of combining particles suspended in water into larger lumps.
- Are coagulants and flocculants the same thing? No, not at all. These are drugs with similar effects that can be used together.
