At the end of this module, you will be able to:
- Define and describe "coagulation"
- Define and describe "flocculation"
- Describe the functions of dissolved air, pH control chemicals, coagulants and flocculants in DAF systems
The following key questions are answered in this module:
What is the term for an aqueous suspension of particles that are too small to settle out under the influence of gravity?
An aqueous suspension of particles that are too small to settle under the influence of gravity is called a colloidal suspension.
How are tiny fiber fines removed from suspension in a dissolved air flotation system?
Tiny fibers attach to small air bubbles and are carried to the surface of the DAF separation vessel.
What do flocculants do in a colloid?
Flocculants combine microflocs formed by coagulation into larger aggregates of flocs.
What do coagulants do in a colloid?
Coagulants neutralize the electrical surface charge on colloidal particles which allows them to combine to form microflocs.
If both chemicals are used, in what order should coagulant and flocculant chemicals be added to a suspension?
When coagulants and flocculants are used together, coagulants should be added to the suspension first.
Below is a transcript of the video sample provided for this module:
Dissolved air flotation, or DAF, is a water treatment process that removes suspended solids from freshwater, processed water, or waste water. This separation is achieved by dissolving air into water under pressure and then releasing the air at atmospheric pressure in a floatation tank. The released air forms tiny bubbles which adhere to the suspended solids in the water causing the solids to float to the surface where they can be removed by a skimming mechanism. Coagulant and flocculant chemicals can be added to the feed water to aggregate and join together the small solid particles to form larger flocks or bundles and improve solids removal. This training module describes how these chemicals work in the DAF process.
Use the additional resources and links below to learn more about this topic: