Advantages of using Flocculant

• 1. Major Saving in cost.
• 2. Highly enhanced rate of settling of suspended particles in clarifiers, settlers, thickners, sedimentation operations etc.
• 3. Improved clarity of aqueous phase.
• 4. Higher filtration rate on filters, drying beds.
• 5. Higher production rates on sedimentation type centrifuges.
• 6. Generally higher through-put rates on production equipment.
• 7. Low size settling tanks, thickners, filters, centrifuges and hence lower cost of quipment.
• 8. Greatly facilitates primary effluent tratment plants. Simple and low cost plants and operations.
• 9. Extremely useful in treatment of waste waters containing dyes, pigments, pesticides, tannerirs and effluents with high suspended solids.
• 10. Possibility of separation of immisible liquids, water etc. and re-use.
• 11. Selective flocculation of minerals for physical benefication.
• 12. BOD, COD reduction possible.
• 13. Simple and quicker operations.
• 14. 4 to 15 times reduction on size of settling tanks, thickners, clarifiers, etc.

How Does Flocculant Work ?

Solid Liquid suspensions vary greatly in their proporties particularly with respect to the rate of settling of solid particles.

In many industrial processes separation of solid particles from the liquid is a critical step. In many cases solids settle at a very low or even negligible velocity and the clarity of supernatent liquid may also be poor.
When a very small quantity of dilute solution of flocculant is mixed with such suspensions, a large number of solid particles form a loosely adhering agglomorate of particles called flocs.
This floc behaves as a large size particle and settles at a very high velocity in the liquid.
Flocculants are very long linear molecules of polymers and act by neutralising repulsive electrical charge on suspended particles and further the solid particles get attached loosely to the polymer chain forming flocs. Thus the floc consisting of solid particles attached to polymer behave as a large sized mega particle and settle at a high velocity. Intrestingly extremely small size particles are also trapped in flocs and the resultant supernatent aqueous phase is relatively very clear.
In case of emulsion of water with oil or grease, etc. the later will separate at a faster rate and float at the surface. Similarly the flocculant can form large size flocs in air floatation technique for faster upward movement of flocs aided by small air bubbles.

Some of the factors that can affect floc fomation are as follows;

Major effects:

1. Type of flocculant.
2. Nature of solids.
3. pH of aqueous media
4. Weight ratio of solids to flocculant

Minor effects :

1 Manner of mixing the flocculant with solid-liquid suspension.
2 Agitation.
3 Strength of flocculant solution.

Prior treatment of solids with a conditioner in some cases can bring about major favorable change in behaviour of solids towards floc formation eg. Organic solids or highly stable suspenions of colloidal particles. It is extremely useful to know the influence of the above factors which play a role in floc formation and settling rate while selecting type of flocculant, designing the system on plant scale and in troubleshooting to get the best results.