1. Flocculation
Prepared by
Dr. Amal A. Aly

2. Water is not everything but every thing is nothing without water.
The preparation of drinking water, cleaning of difficult waste-water, and improvement of water quality in closed circuits are our specialties.

3. Clarification of water as an aid to sedimentation of particulate matter has been practiced from ancient times.
The Egyptians and Romans practiced a form of coagulation as early as 2000 BC.

4. Almost all natural surface waters contain particulate matter and/or colloidal substances that are not removed rapidly by sedimentation Consequently, it is necessary to catalyze this sedimentation by physical and/or chemical process which is coulled flocculation.

5. Flocculation is an important operation in solid-liquid separation.
Flocculation is a process of bringing together small particles to form larger particles.

6. How do particles come together when flocculating?
What shapes of they form?

7. Flocculation process
coagulation
floc formation, and
sedimentation.

8. Coagulation:
The process whereby chemical are added to a wastewater resulting in a reduction of the forces tending to keep suspended particles.
By adding a simple flocculant which reduce the electrostatic repulsion, the aggregation takes place.

9. (a) Coagulation

10. Floc Formation:
Where the flocculant molecules attach themselves to the surface of suspended particles at one or more adsorption sites, and that part of the chain extends out into the bulk of the solution. The free end of the flocculant is then able to adsorb onto another suspended particle. When contact is made, the bridges are achieved and the flocs are formed .

11. (b) Flocculation

12. Sedimentation:
The separation of suspended solids from wastewater by gravity.

13. Flocculation unite

14. Addition of flocculant

15. Coagulation and floc formation

16. Sedimentation

17. Flocculating Agents Flocculating agents
Inorganic flocculants Organic flocculants

18. 1- Inorganic Flocculants
The inorganic flocculants refer to the salts of multivalent metals, like aluminum, calcium and iron. Inorganic flocculants suffer from many distinct disadvantages the most serious of which is the tonnage of flocculants involved. One requires a large volume of inorganic salts to obtain the same result that can be obtained with a very small amount of polymeric flocculant.

19. Moreover, large tonnage use of inorganic materials produce a lot of sludge, which is hardly a problem in the case of polymeric flocculants. Since the inorganic salts are only effective over a particular pH, there is frequent need for pH adjustment.

20. Inorganic flocculants
Common Name
Formula
pH at 1%
Alum
Al2(SO4)3. 14H2O
3.4
Lime
Ca(OH)2 12
Ferric Chloride
FeCl3.6H2O
3-4
Ferric Sulfate
Fe2(SO4)3.3H2O
Copperas
FeSO4.7H2O
Sodium Aluminates
Na2Al2O4
11-12
Aluminum Chloride
AlCl3 -

21. 2- Organic Flocculants
The organic flocculants fall into three categories synthetic, natural and grafted polymer.
Advantages:
1- Small sludge producible,
2- Fast precipitation rate,
3- Easy dewatering,
4- Small ash after burning and
5- High stability.

22. A-Synthetic organic flocculants:
Synthetic flocculants are mostly water-soluble linear polymers. They are much effective than natural ones, which is due to
the tailor-ability of the man-made polymers.
It is easy to control the molecular weight, molecular weight distribution, and the nature and percentage of ionic groups on the polymeric backbone, as well as the very structure of the polymer itself.

23. Synthetic Flocculants
Cationic Anionic Non-ionic
Ammonium (primary,secondary,tertiary and quaternary ),
sulfonium and
phosphonium compounds.
polyacrylamide
acid or polyacrylic polystyrene sulfonated

24. B-Natural Organic Flocculants:
Although there are many advantages of synthetic polymers natural polymers have a great advantage over them which is their biodegradability and nontoxicity. At the same time, this advantage of natural polymers comes as a major drawback since it reduce their storage life and tells upon their efficiency due to the lowering of the molecular weight.
Natural polymers as chitosan, guar gum, been gum, polysaccharide and starch.

25. C- Grafted Polymers
It is thus evident that all the polymers, whether natural or synthetic, have one or another disadvantage. In past, many attempts have been made to combine the best properties of both by grafting of the synthetic polymers onto natural ones. One of the great advantages thus obtained is the consequent reduced biodegradability of the grafted products because of the drastic change in the original structure of the natural polymers as well as the synthetic polymeric content in the product that is not a food for the bacteria.

26. Thank you