Flocculation or floculation is a significant process widely utilized in water treatment operations, including purification of drinking water, sewage water treatment, storm water treatment and treatment of various other industrial wastewater streams. Though often used interchangeably with coagulation, it is in fact a distinct process that similar to coagulation aids in sediment and contaminant transport. Usually, flocculation follows the coagulation process and helps in getting rid of of colloidal particles or flocs through rapid settlement in the solution. In certain cases, flocks also rise to the surface of the treated liquid, which can then be filtered out from the solution through the process of filtration.
How Flocculation Takes Place?
In the flocculation process, flocculants, or flocculating agents are generally added to the liquid so that flocculation is promoted and smaller particles (inorganic and organic), water-stable soil aggregates, or flocs/flakes agglomerate to form larger particles or lumps in the flowing medium. These visible lumps which were earlier in the form of untraceable primary particles in the solution are then easily removed from the water by purification processes such as filtration or sedimentation.
Thus, flocculation can be used to eliminate visible sediments and materials from impure water, or to treat water turbidity by removing colloids such as milk, glues or inks.
Substances Used in Flocculation
There are various chemical and natural substances that are used in removing unwanted particles through flocculation. Common chemicals/flocculants used for initiating flocculation process are:
A few natural products are also employed as flocculants. The most popular natural substances used as flocculants are:
- Aluminium chlorohydrate
- Aluminium sulfate
- Calcium oxide
- Calcium hydroxide
- Iron(II) sulfate
- Iron(III) chloride
- Sodium aluminate
- Sodium silicate.
Factors Affecting Flocculation
- Alginates (Brown seaweed extracts),
- Moringa oleifera seeds (Horseradish tree)
- Strychnos potatorum seeds (Nirmali nut tree)
- Guar gum, etc.
Formation of flocs or flakes during flocculation is a complex process that depends on several factors. A few important factors are as follows:
Uses of Flocculation
- Physical (e.g., Turbulence)
- Chemical (e.g., Ionic concentration)
- Biological (Bacterial populations and extracellular polymeric material).
- Predominant uses of flocculation is in water and wastewater treatment, such as drinking water treatment, sewage water treatment, storm water treatment and treatment of various other industrial wastewater streams.
- Flocculation is also used in brewing, especially to measure the progress of brewing yeast at the end of fermentation
- In the food industry, the process is also extensively employed in producing cheese.