2. INTRODUCTION
• Coagulation-flocculation is usually included, either as pre-treatment such as before rapid sand
filtration or as post-treatment step after sedimentation.
• Coagulation and flocculation occur in successive steps intended to overcome the forces
stabilizing the suspended particles that allowing particle collision and growth of flocculent.
Then can be settled and removed by sedimentation or filtered out of the water.
• Coagulation-Flocculation is also a common process to treat industrial and domestic
wastewater in order to remove suspended particles from the water
3. CONT…
• Coagulants neutralize the negative electrical charge on particles, which destabilizes the forces
that keep colloids apart.
• Water treatment coagulants are comprised of positively charged molecules that, when added
to the water and mixed, accomplish this charge neutralization.
• When an inorganic coagulant is added to water containing a colloidal suspension, the cationic
metal ion from the coagulant neutralizes the negatively charged electric double layer of the
colloid.
• same occurs with an organic coagulant, except that the positive charge most commonly
comes from an amine (NH4+) group attached to the coagulant molecule.
4. COAGULATION-FLOCCULATION PROCESS
• Firstly, Coagulation-flocculation is use of chemical reagents to destabilize and increase the size of
the particle and then mixing to increase of flogs size.
• Physical separation of the solids from the liquid phase. This separation is usually achieved by
sedimentation floatation or filtration.
• The common reagents are mineral and organic coagulants which typically iron and aluminum salt,
and organic polymers.
5. CONT..
• Flocculation additives such as activated silica, talcum, activated carbon, anionic or cationic
flocculants and pH control reagents such as acids or bases.
• Certain heavy metal chelating agents can also be added during the coagulation step.
6. CONT..
• Flocculation additives such as activated silica, talcum, activated carbon, anionic or cationic
flocculants and pH control reagents such as acids or bases.
• Certain heavy metal chelating agents can also be added during the coagulation step.
