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