What is Flocculation?

Mary McMahon
Mary McMahon

Flocculation refers to the separation of a solution and most commonly, this word is used to describe the removal of a sediment from a fluid. In addition to occurring naturally, it can also be forced through agitation or the addition of flocculating agents. Many manufacturing industries use it as part of their processing techniques, and it is also extensively employed in water treatment. The technique is also widely used in the medical world to analyze various fluids.

Flocculation is used in water treatment to separate and remove dangerous sediment from wastewater.
Flocculation is used in water treatment to separate and remove dangerous sediment from wastewater.

The term is derived from floc, another word for flakes of material. When a solution is flocculated, the sediment is formed into clumps of aggregate that are easier to see. When this is initiated intentionally, the floc is usually removed with filters or screens. When a solution was separated by accident, attempts may be made to turn it back into a solution so that it will be usable again.

Milk is a common colloid, a substance that is made up of many components but outwardly appears as one component until flocculation occurs.
Milk is a common colloid, a substance that is made up of many components but outwardly appears as one component until flocculation occurs.

The technique can be used to separate out visible sediments and materials, and to treat colloids. A colloid is a solution that looks uniform, but actually consists of one or more components blended together. Some common examples of solutions with visible sediment are swimming pools and wastewater, both of which are flocculated for purity. Frequently encountered colloids include seafoam, milk, glues, and inks. The separate elements within the colloid are thoroughly blended to create a new compound, and they can be separated again.

Depending on the circumstances, flocculation may be desired or undesired. It is often deliberately achieved in the treatment of wastewater, removing harmful substances so that they can be treated separately. Other examples of deliberate processing include grease traps in commercial kitchens, centrifuges for processing blood, and facilities for extracting salt from seawater. A classic case of undesired flocculation is soured milk, in which the milk colloid separates, forming a layer of flakes of material on the top. If this separation is not desired in a manufacturing environment, steps are taken to minimize it.

There are a number of ways to separate a solution. Agitation is a common technique, since it can encourage flakes of sediment to clump together and gather on the bottom or the top, depending on their weight. Flocculant chemicals are also used to encourage clumping in a solution. Typically, they have a different electrical charge than the substances being precipitated out of the solution, attracting the material in clumps of particles.

Centrifuges spin substances to achieve flocculation.
Centrifuges spin substances to achieve flocculation.
Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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Discussion Comments


I'm pretty sure that all countries treat their sewage to produce tap water.


"Flocculation refers to the separation of a solution." My understanding is that it refers to a process by which small particles - possibly microscopic ones - clump together to form bigger particles. (These larger particles may then precipitate out, or be captured by filters.) It does not - as I understand it - remove solutes from a solution.


@everetra - The reality is that some oil spills clean themselves up, for the very reasons you cite. The water itself acts as a flocculent, constantly scrubbing itself away in the ocean tides.

Also the ocean has its own plankton which eat the oil as well. That doesn’t mean companies shouldn’t act, of course; it just means we have to understand that they are cooperating with nature's own cleaning program.


I wonder if companies use a flocculating agent in treating ocean oil spills. I know that sometimes microorganisms are released into the ocean to consume the spilled oil.

The only problem that I see however is that this kind of treatment does not take place in a controlled environment, as would be the case with a water treatment plant to clean up sewage.

I think the constant tow of currents in the ocean might make it more difficult to perform a clean separation of the oil from the ocean water.


@SkyWhisperer - That’s an extreme example, but can you imagine that most people won’t even drink tap water, knowing where it came from-and despite the fact that it’s been subjected to its own chemical flocculation process.

It’s also been shown that a lot of so-called bottled water is nothing but tap water with a pretty label. Tap water, in my opinion, is not actually as bad as people think.

I think water treatments do the trick and spending money on bottled water is like paying for air.


I understand that flocculation is used to purify drinking water. It still gives me the chills however to think about what the water was like before it was treated, and now that it’s treated I can actually drink it. It’s more psychological revulsion than anything else, because at the chemical level the water is totally pure.

I’ve also heard that some countries like Singapore will use the flocculation process in their sewer treatment, with the result of producing drinking water out of what was once sewage!

Again, it’s more psychological repulsion than anything else, but I couldn’t imagine myself drinking that water knowing where it had come from.


Very interesting.



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