Brief introduction of coagulation and flocculation filtration process

1. COAGULATION AND
FLOCCULATION
Anup Ghimire, Rock Face Limited

2. COAGULATION
 Colloidal
particles: suspended in drinking
water
 Colloids are minerals such as silt, clays,
silica, hydroxides and metallic salts and
organic particles such as humic and fluvic
acids, colour and surfactants.

3. …COAGULATION
 Hydrophilic:
Affinity for water
 soap, starch, proteins and detergents
 Hydrophobic

metal oxides and clay

4. …COAGULATION
 Coagulation
and flocculation remove colour
and particulate matter including protozoa,
viruses, bacteria and iron, manganese,
tastes and odours from water

5. …COAGULATION

Coagulation involves the neutralization of
suspended solids by adding coagulants in the water
which forms micro flocs after sticking together

6. …COAGULATION
 Coagulation
process is faster and involves
high-energy
mixing
which
neutralizes
electrical charges of the particles and
facilitates floc formation.

7. FLOCCULATION
 Flocculation
is a slow and gentle mixing
process.
 The destabilized particles are agglomerated
to form large visible flocs

8. …FLOCCULATION
 Pin
flocs and visible flocs are produced at
the flocculation stage when micro flocs are
allowed to mix slowly. Pin flocs are filtered
from water by sedimentation. Coagulants
can be mineral or organic.

9. …FLOCCULATION
 Iron
salts and aluminium salts are mineral
coagulants used in water treatment and
polyamines, polydadmac, dicyandiamide
resins, and melamine-formaldehyde resins
are organic coagulants.