Coagulation

Definition - What does Coagulation mean?

Coagulation is a chemical process in which the destabilization of non-settleable particles takes place. These particles form clumps with the help of a coagulant. Colloidal particles and very fine solid suspensions initially present in a wastewater are combined into larger agglomerates that can be separated via various separation methods.

Coagulation is often used to remove suspended solids in domestic and industrial wastewater treatment plants. For water treatment, coagulation is generally followed by flocculation.

Corrosionpedia explains Coagulation

Coagulation is a chemical process used to neutralize charges and form a gelatinous mass to trap (or bridge) particles, thus forming a mass large enough to settle or be trapped in a filter.

The words "coagulation" and "flocculation" are often used interchangeably, but they refer to two distinct processes. Coagulation is often used in combination with flocculation.

Coagulation is commonly achieved by adding different types of chemicals (coagulants) to wastewater to promote destabilization of the colloid dispersion and agglomeration of the resulting individual colloidal particles.

The most common coagulants used in wastewater treatment are:

  • Aluminum salts (alum)
  • Ferric and ferrous salts
  • Lime
  • Cationic polymers
  • Anionic and non-ionic polymers

Coagulation of colloids occurs when a stable colloid (because of the intrinsic stability of the colloid dispersion) or a stabilized colloid (because of the presence or a double layer) is destabilized. Destabilization of colloids occurs when the colloidal particles are brought close enough to each other for agglomeration to occur.

The ability of a chemical additive to produce coagulation is generally dependent on the:

  • Electric charge of the ion or molecule used as coagulant — The larger the charge, the more effective the coagulant
  • Size of the ion or molecule used as coagulant — The larger the size of the molecule, the more effective the coagulant

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