Coagulation is a process used in wastewater and drinking water treatment. The process is based on the laws of particle interaction - Brownian motion, van der Waals forces and intermolecular forces. The fact is that fine particles of contaminants do not settle during the process of gravitational settling, since they have a small mass.
To increase the intensity of sedimentation of these particles, special chemicals are added to the water - coagulants, which promote the unification (sticking together) of finely dispersed particles as a result of their collisions and the action of intermolecular attractive forces. To speed up coagulation and increase the effect, stirring is used (particles collide more often). In general, the effect depends on the time of contact of the liquid with the coagulant, the intensity of mixing, the dose of the coagulant and its type and quality.
The most common coagulants for water purification are salts of polyvalent metals: iron, aluminum.
1. Aluminum sulfate Al2(SO4)3∙18H2O. it comes in two types:
1.1 Unrefined is a grayish-green technical product. Represents pieces of solid matter. It is obtained by treating bauxite, clay, and nepheline with sulfuric acid. This product contains at least 9% Al2O3.
1.2 Cleaned - consists of slabs of grayish-pearl color. It is obtained by dissolving crude aluminum sulfate or alumina in sulfuric acid. This coagulant for water purification contains at least 13.5% Al2O3.
Advantages of purified coagulant:
There is no need for special equipment to dissolve the product;
Reducing the cost and simplification of loading, transportation and unloading of the product;
2. Sodium aluminate NaAlO2 is a white solid (with a pearlescent sheen at the fracture). It is obtained by dissolving aluminum in sodium hydroxide.
3. Aluminum hydroxide Al(OH)3. The use of this coagulant is associated with the following difficulties:
The substance is effective only at water pH values of 6.5 - 7.5. If the pH is lower, then partially soluble salts are formed, and if it is higher, then aluminates.
The coagulant is also sensitive to water temperature: when it reaches 40 ℃, the coagulation process slows down and further cleaning becomes more difficult (filters become clogged).
4. Aluminum oxychloride (OXA). The general form of the compound is Al(OH)mCl3n-m. This coagulant is qualitatively different from other aluminum-containing coagulants for water purification due to its surface acidic shell. Advantages:
Possibility of use in the cold season;
Works with a wider pH range;
Reduces alkalinity less, as a result there is no need for stabilization treatment.
5. Aluminum chloride AlCl3 – crystalline white powder.
1. Ferric chloride FeCl3*6H2O – represents dark crystals (with a metallic luster). It is obtained from the chlorination of steel filings or as a by-product from the hot chlorination of ores. Very hygroscopic.
2. Iron (II) sulfate FeSO4*7H2O – iron sulfate – these are greenish-blue crystals. There are grades A and grade B. It is mainly used for lime or lime-soda softening. Disadvantage - it is necessary to add lime or chlorine before coagulation.
3. Iron (III) sulfate is a crystalline product. It is obtained by dissolving iron oxide in a solution of sulfuric acid. Advantages:
Has little effect on the pH value;
Works at low temperatures.
Minus – precise dosage is required.-
4. Chlorinated iron sulfate Fe2(SO4)3+FeCl3.
There are different ways to purify liquids. This applies to the purification of both drinking and domestic water, as well as...
The simplest cleaning method is to use filters. Filters filter out all harmful substances and make the water cleaner. In filtered form, it is suitable for consumption and safe for humans.
However, there is another method of water purification, which is called coagulation, and coagulants are used to work with it.
Coagulation is a special method for purifying drinking and waste water. Coagulants themselves are substances that have interesting features and are capable of chemical reactions.
If you look at their molecular shape, you can see that they all have a positive charge. While most contaminants in water have a negative charge.
The presence of two negative charges in the atoms of dirty particles prevents them from joining together. This is why dirty water, in most cases, simply becomes cloudy.
As we said above, the positive charge of coagulants contributes to their operating principle.
When it gets into a contaminated liquid, this substance begins to actively attract all harmful microorganisms and other similar substances. Each coagulant molecule is capable of attracting several molecules of other substances.
That is why it is important to accurately dose the amount. The main thing is that you do not use too little coagulant, since then the reaction will proceed sluggishly. The sediment will fall slowly and not in the quantities it should. And this will lead to the fact that the liquid is not properly cleansed of harmful impurities.
After attraction, the coagulant molecules react and turn into a special compound.
After the reaction they become like white flakes. These flakes precipitate at the bottom of the liquid container.. The person is then only required to remove the sediment through any type of filtration.
In extreme cases, they even use the method that is used for homemade, when the top layers are simply drained from the container, leaving iron deposits at the bottom.
There are several types of coagulants. We will not list all these substances and their formulas now, since this can take a huge amount of time. However, several of the most popular groups are still worth mentioning.
Coagulants are:
Organic substances are specially derived polymers or other similar elements that help purify liquids by coagulation. Inorganic, as the name suggests, refers to synthetics and mineral elements.
If we talk about the compositions that are most often used in everyday life and industry, then they are not much different from each other.
In most cases, coagulants based on aluminum or iron are used. Iron is used for rough treatment of wastewater and industrial waste. It's affordable, efficient, and gets the job done well.
The most popular iron compounds are:
The first sample is used to purify wastewater from sewers, and the second one is good at removing the smell of hydrogen sulfide and large particles of contaminants.
Of the aluminum coagulants it is worth noting:
The first variety is the most common and is used to purify drinking water. The second and third coagulants are more suitable for working with wastewater, natural sediments, etc.
You must choose a coagulant very carefully, since this substance, although safe for humans, is quite highly specialized.
As with any other filter media and installations, we recommend that you turn to modern science. Namely, submit the water for analysis. After thorough tests in the laboratory, you will know exactly what problems exist in your case and what exactly needs to be done.
Then choosing a suitable coagulant will be much easier.
It is worth understanding that coagulants are quite specific things. In some cases, they reject each other or certain elements in the water, while in others they enhance their effect or combine it according to certain principles.
Thus, the use of a simple coagulant made of iron and aluminum sulfate allows not only to quickly purify water, but also to significantly soften or deferrize it.
However, you should not overdo it here, since drinking water that is too diluted is also not very useful, if not harmful. After all, with it you will not receive all those necessary minerals and nutrients that exist in the unprocessed liquid.
As for the specific use of coagulants, there is no need to advise anything. In industry, this cleaning method is used almost everywhere. But there the coagulation processes can be established and put on stream without any problems.
In everyday life, you will have to buy special installations, which are not so cheap. An alternative to them can be individual household-type coagulants, which are sold in small containers.
They simply need to be added to the water and then filtered out the precipitate. But, as you yourself understand, it will hardly be convenient for you to act this way all the time. After all, this cleaning method is too labor-intensive and time-consuming.
If you choose between inorganic and organic compounds, then it is better to give preference to the second option.
Organics have several interesting benefits that cannot be ignored.
First of all, it is much more effective. Organic coagulants act faster and require less to obtain optimal results. Organics also fight chlorine well and remove unpleasant odors from water. For example, from hydrogen sulfide, which often accompanies ferruginous liquid.
At the same time, it does not change the pH in the water and is able to interact with algae.
After application, organic coagulants are significantly reduced in size. This results in less sediment, which is much easier to filter out. But at the same time, the efficiency of water purification does not decrease. That is, a qualitative reduction in the amount of sediment does not in any way affect the quality of purification of the liquid itself.
Inorganic coagulants interact better with water. They soften it, get rid of excess salts, iron and coarse impurities. But here you need to take into account one serious nuance. Inorganic compounds require extremely precise measurement.
This is the only way to use them to their full potential. If you don’t guess the exact dosage (and this is very difficult to do at home), then the cleaning efficiency will significantly decrease.
This is why inorganic substances are so often used in industry, but are practically never found in everyday life.
However, modern manufacturers have already solved this problem by selling mineral coagulants in packages with dispensers and detailed instructions.
Mechanical filtration using filters cannot always cope with purifying water from contaminants. The smallest particles that are inaccessible to filters remain in the water, which leads to its turbidity.
Causes of cloudy water:
Swimming in muddy water is unpleasant and dangerous. Special products will help eliminate cloudiness in water, make it clear and safe.
Coagulation or flocculation is the process of combining small particles into larger ones under the influence of adhesion forces. Flocculation allows you to remove the smallest particles from the water column that the filter cannot capture. Under the influence of flocculants and coagulants, pollutants become heavier, stick together and precipitate, making them accessible to water vacuum cleaners and filters.
It is worth noting that coagulants not only help remove the smallest contaminants, but also enhance the work of disinfectants, which makes it possible to more effectively purify water from various types of contaminants.
AquaDoctor Superflock and FL are an excellent choice for eliminating water turbidity in pools of any size, design and load.
– a highly effective long-acting coagulant that effectively fights the smallest contaminants in the water mass. Under the influence of the drug, the particles combine, become heavier and precipitate, accessible to filters. With its help, the water in the pool will quickly acquire crystal purity and transparency. The active formula of the product includes aluminum sulfate. It not only fights turbidity, but also helps improve the quality of water disinfection. The product is available in cartouches.
– effectively fights even the smallest water contaminants
With this you can remove the smallest particles from water
– a quick-soluble product that is designed to remove the smallest particles from the water column that are inaccessible to the filtration system. The product will help make the water crystal clear and transparent. The basis of the product is aluminum sulfate. The product not only actively interacts with the smallest particles, forming sediment from them that is accessible to filtration systems, but also enhances the effect of disinfectants. Available in granular form.
AquaDoctor FL is immune to temperature changes and therefore works equally effectively in outdoor and indoor pools.
Flocculants and coagulants do the same job - they fight water turbidity by combining and precipitating the smallest contaminants. Despite the apparent similarity, they still have differences.
Coagulants precipitate particles using electroliptic action. As a result of this impact, the particles lose their charge and combine into heavier and larger compounds that are easy to remove from the water column.
Flocculants unite particles by forming polymer bridges, their electroliptic properties remain unchanged.
Coagulants form a stable sediment, which is easy to collect with a vacuum cleaner after settling, but still not all filters are able to capture it. Flocculants purify water more efficiently, forming large flakes that are easily removed mechanically by filters of any design.
The difference is in the duration of the coagulation processes. Coagulation can take just a few seconds, but flocculation can last tens of minutes.
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.
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:
All types of wastewater, when divided into groups, can be presented in the form of a table.
That is, there are many options for waste water 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.
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.
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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.
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.
There are many ways to purify wastewater. When installing autonomous sewer networks, in addition to installing the usual filters that can filter out harmful substances and at the same time make the water cleaner, a precipitation treatment method - coagulation - is increasingly being used.
We will tell you on what principle the coagulant works for water purification. The article offered for review describes in detail all the varieties used in practice. You will learn what to consider when choosing a product and how to use it correctly.
Coagulation is a method of water purification by adhesion of dispersed pollutants for subsequent removal by mechanical method, filtration. The combination of polluting particles occurs due to the introduction of coagulating reagents, creating conditions for the simplest elimination of bound pollutants from the purified water.
The term "coagulatio" translated from Latin means "thickening" or "coagulation". Coagulants themselves are substances that, through a chemical reaction, can create insoluble and slightly soluble compounds that are simpler and easier to remove from water than dispersed components.
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