Factors Affecting Coagulation & Flocculation
Temperature
Time
Coagulant types
Coagulant dosage
Characteristics of water
pH
Mixing & Turbulence
Coagulant is generally pH dependent
Alum: 5.5 – 7.5 (optimum pH ≈ 7.0)
Ferric: 5.0 – 8.5 (optimum pH ≈ 7.5)
The higher the temperature, the faster the reaction
Cold water near 0 o C is difficult to coagulate
Provide sufficient mixing and detention time
Control the mixing rate &the turbulence
Degree of mixing
Can be mechanical or static
Choose the right coagulant for optimum result
Aluminium sulphate (Alum), most widely used
Add the right amount of coagulant
Determined by jar test for optimum qualities of floc: (size, settling rate)
Types and Suspension Concentration
Nature of turbidity – Particles of different size are easier to coagulate than uniform size particles.
Highly turbid waters may require a lesser amount of coagulant than waters with slightly turbidity