coagulation water treatment

What is Coagulation Water Treatment?

What is coagulation water treatment?

Coagulation is a crucial step in water treatment aimed at removing suspended particles from water. During this process, a coagulant, often a chemical like aluminium sulphate (alum) or ferric chloride, is added to untreated water. The coagulant destabilised the particles in the water, causing them to clump together or coagulate. As these particles aggregate, they form larger, heavier flocs that can settle more easily or be more effectively removed during subsequent treatment processes.

Coagulation helps in the removal of impurities such as dirt, silt, bacteria, and other suspended solids. The coagulated particles can be removed through sedimentation or filtration, leading to clearer and cleaner water. This method is commonly used in water treatment plants to enhance the efficiency of the overall purification process, contributing to the production of safe and potable water.

coagulation water treatment

How is this treatment applied today in India?

In India, coagulation is a fundamental step in water treatment, especially in municipal water treatment plants and larger-scale facilities. The process is typically applied as follows:

Chemical Addition:

 Coagulants, often aluminum sulfate (alum) or ferric chloride, are added to untreated water. The dosage is carefully controlled to achieve optimal coagulation without overdosing.


After adding coagulants, the water is gently mixed to ensure even distribution of the chemicals. This allows the coagulants to react with impurities in the water, initiating the coagulation process.


Following coagulation, flocculation is often employed. During this phase, gentle stirring encourages the small coagulated particles to form larger, more easily settled flocs. This prepares the water for the next stage in the treatment process.

Sedimentation or Filtration:

The water is then allowed to settle in sedimentation basins or passes through filters. The heavier flocs settle to the bottom, or they are removed by filtration, effectively separating impurities from the water.


After coagulation and clarification, the water typically undergoes disinfection, often through methods like chlorination or ultraviolet (UV) treatment, to eliminate any remaining microorganisms and ensure the water is safe for consumption.


Once treated, the water is distributed through a network of pipes to homes and industries, providing a clean and safe water supply.

What is flocculation in water treatment?

Flocculation in water treatment is a process where tiny particles in water, such as dirt or bacteria, clump together to form larger particles called flocs. This aggregation makes it easier to remove these particles from the water through filtration or settling.

Difference between flocculation and coagulation water treatment

  • Coagulation involves adding a chemical coagulant, like alum or ferric chloride, to the water. This coagulant neutralizes the charges on the particles, causing them to come together and form small clumps called “coagulant flocs.”
  • Flocculation follows coagulation and involves gently mixing the water to encourage the coagulant flocs to collide and aggregate into larger, visible flocs. This process helps in further settling or filtration of the suspended particles from the water.

Coagulation, as part of the comprehensive water treatment process, is crucial in addressing the diverse water quality challenges in India, helping to meet the demand for safe and potable water across various regions.

Also Read: Benefits of Having an Under Sink Water Purifier

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