Adding the right coagulants that have a positive charge neutralizes the negative charge and the particles are transformed into microparticles (coagulation). This is followed by the growth of the microparticles into larger aggregates that are visible and suspended (flocculation). Flocculation can be a continuation of coagulation, or it can be intensified by the addition of flocculants.
For successful coagulation and flocculation, appropriate mixing is important to accelerate the incorporation of the chemicals and the number of contacts between the particles. It is carried out statically (static mixers) or dynamically with motorized agitators.
The final separation of suspended particles from the water is carried out by sedimentation or direct filtration (if the suspended particles are not particularly high). Settling takes place in settling tanks of various designs. In terms of efficiency (capacity) and space required for settling, lamellar settling tanks are the most efficient.
What Is Coagulation In Water Treatment?
Coagulation is a chemical process, which is why scattered colloidal impurities become larger in the processed medium. They turn into flakes visible to the human eye, which are formed in the process of adhesion of small particles. Later flakes are precipitated and removed by mechanical filters.
The mechanism of the reagent is a special chemical process. All coagulating drugs at the molecular level have a positive charge, while all impurities in a liquid medium are negative. In this situation, all impurity molecules cannot combine in larger formations precisely because of the negativity of their molecules. To the human eye, impurities are not visible at all.
Coagulants find use in colored water, which has low turbidity and alkaline or low pH. When the pH percentage is at the right level, it helps to purify the water. A coagulant used for cleaning is able to produce a hydrolysis process to enable a pH that is suitable for coagulation.
Compounds that become flocculent are formed when metal hydroxide absorbs impurities. After a short time, these hairs can be filtered for the reason that they are solid substances and when they have a heavy weight, they are placed in the main base.
The action of the substances is based on the molecular form which has a positive charge, while most pollutants have a negative charge. When two negative charges are found in the atomic structure of the particles, it does not allow them to mix with each other. This shows the fact that dirty water is always cloudy.
When a small amount of coagulant is present in the liquid, the suspensions present in the liquid are removed from there. Therefore, when the amount of light that is scattered increases, for a short period of time the liquid becomes cloudy. A single coagulant molecule is enough to once absorb several molecules of impurities.
The Process of Coagulation
Coagulation is the process of coalescing the smallest particles into larger ones under the influence of cohesive forces. Flocculation allows the removal from the water column of the smallest particles that the filter cannot capture.
Under the influence of flocculants and coagulants, contaminants become heavy, clump, and coagulate, making them available for capture by water vacuums and filters.
At the same time, it should be noted that coagulants not only help to remove the smallest contaminants, but also improve the work of disinfectants, allowing water to be cleaned more effectively of different types of contaminants.
What Is Removed And Added During Coagulation?
During the coagulation process, chemicals such as sodium aluminate, iron sulfate, and aluminum sulfate are added during the process to purify the water as effectively as possible.
Aluminum sulfate is most often used to purify water. With the use of these chemicals or otherwise known as coagulants, water pollutants such as bacteria, iron, sand, protozoa, and gravel are removed.
Types of Coagulants Used In Water Treatment
In order to have the best possible success in water treatment with coagulants, you must know which are the best types and which have the most satisfactory result. There are two types of coagulants, organic and inorganic, and both differ from each other in terms of the way they are used and the result they give in the end, both types have their own advantages.
Organic Coagulants
Organic coagulants are monomers based on iron and aluminum that have applicability in the water treatment of black waters. There are many different types of organic coagulants, they have different charges and their polymer molecules have different connections.
This includes polymers that have a charge in their base or otherwise called ionic and polymers that do not contain a charge or non-ionic polymers. Polymers that have a negative charge are called anionic polymers and those with a positive charge are called cationic polymers.
Inorganic Coagulants
Iron and aluminum salts are the most commonly used inorganic coagulants for sewage treatment. This includes metals based on iron and aluminum. When these coagulants are used to treat sewage, they undergo several different reactions involving hydroxyl ions that produce polynuclear and monomeric species.
Wastewater Coagulation
Each of the stages used for the treatment of wastewater is necessary to achieve the appropriate results. However, tertiary and primary treatment is very important for the process in general.
Primary treatment reduces the number of solids. Without the primary treatment, the whole process would have a poorer result. The tertiary treatment removes the microbiological polluting material so that the affected organs do not get sick.
The methods of wastewater treatment are disinfection and coagulation. Both of these processes can be performed in different ways and with non-chemical or chemical methods. All these methods used for the treatment of wastewater have their own disadvantages and advantages, which make each of the methods stand out.
What Coagulants To Use For Water Treatment?
The most used coagulant to treat wastewater is aluminum sulfate, which has a better effect. But other coagulants are also used, such as iron sulfate, sodium aluminate, and ferric chloride.
Jar Test
Companies that have water treatment plants use coagulants to treat the water in a way that cleans it. Therefore, jar testing is needed to choose the right coagulant and the dose needed to destroy harmful pathogens.
Microscale Dewatering Test
Microscale dewatering test is a process during which a large number of flocculation tests can be performed at the same time. And flocculants with different solutions are tested.
Streaming Current Detector
The Streaming current detector is used in such a way that the coagulant control process becomes automated. This detector constantly receives information on the Internet about the samples. In this way, the work leader in the plant will know the right dose of coagulant at any time.