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Coagulation- Flocculation - Coggle Diagram
Coagulation- Flocculation
How ?
2) after destabilization of surface charge, colloids are attracted to each other & form flocs through flocculation
3) flocs settle down by gravity or by flotation (DAF)
1) coagulant is added to water to reduce the surface charge of the colloids
Definition
Flocculation: a process of forming aggregate of flocs to form larger settleable particle.
Coagulation: a process of adding a coagulant to water for subsequent processing by flocculation
Objective:
to destabilize colloidal particles so that they can attach to each other
The need for Coagulation
small particles
not settle on their own
surface water
colloids
color
small particles
pathogens
The probability of particle collision and agglomeration
to get two particles to stick together
collision
relates to mixing (flocculation)
sticky surface
repulsive forces = neutralized (coagulation)
Coagulant Selection
check for pH effects on final turbidity
causes:
add alum to the sample water
find optimal coagulant concentration
purpose:
give clearer water at shorter time
utilize a jar test apparatus
coagulants
salts that suppress the negative charge of colloidal particles
reduce the repulsive force
increase the ability of particles to stick together
Nomenclature
Turbidity
interference with the passage of light
Coagulant
a chemical that neutralizes particle charge and make it
sticky
Floc
a group of agglomerated particles