1. SETTLING COLUMN ANALYSIS FOR FLOCCULATING PARTICLES (Type II settling)

2. Type II Settling Flocculent Settling
Flocculating but not concentrated suspension.
The diameter of particles changes.
This means that there is not a unique settling velocity
Increase in particle size caused by flocculation varies with time.
Size and settling velocity will vary with depth.
Take samples over the depth of the column at set time intervals.
Mustafa Nasser 2012

3. Type II Settling
Flocculent Settling

4. Type II Settling
Flocculent Settling

5. Type II Settling
Flocculent Settling

6. Type II Settling
Flocculent Settling

7. Type II Settling Flocculent Settling
xij is the mass fraction of particles remaining in suspension at depth i and time j, then the percentage of particles removed at that depth and time is

8. A further complication:
Type II Settling
Flocculent Settling
A further complication:
Concentration and settling velocity of particles are also a function of the total depth of settlement (i.e. the maximum depth through which they settle)
The settling analysis must be carried out using a column having the same depth as the proposed settling basin.
Mustafa Nasser 2012

9. Type II Settling Flocculent Settling
Ways of performing the calculation
(a) BY USING INTERPOLATED VALUES OF r
The following calculations are carried out in the table below:
(i) identify the residence time t0
(ii) interpolate for the concentration profile at this time;
(iii) convert the concentration profile to r-values
(iv) calculate the values of Δr;
(v) identify the average depth corresponding to each value of Δr;
(vi) form the product z Δr;
(vii) find the sum of all the values of z Δr;
(viii) divide this by the depth of the column.

10. Average concentration at t
(B) THE CONCENTRATION PROFILE IN THE SETTLING COLUMN
As there is information about the concentration profile throughout the column the average concentration in suspension at any time, t, is
Average concentration at t
Concentration at t as a function of z
The mass fraction remaining in suspension must be and the removal = (1  x0(t))
Mustafa Nasser 2012

11. By (a) using interpolated values of r
(b) By considering the concentration profile

12. Interpolate for the concentration profile at 105 minutes

14. The mass fraction remaining in suspension must be
(b) By considering the concentration profile
The mass fraction remaining in suspension must be
and so the removal is
Mustafa Nasser 2012

15. Depth Time of sampling /(min) Average
/(m) Concentration dz C(av)dz  
SUM = 278.5
Mustafa Nasser 2012

16. Recall the average concentration is
mg ℓ−1
So if the original concentration was 250 mg ℓ−1
That is the mass fraction left in suspension is 0.37
Thus 1 – 0.37 = 0.63 is the mass fraction removed
Mustafa Nasser 2012

17. Type III and Type IV Settling

18. Type III and Type IV Settling

19. Type III and Type IV Settling

20. Type III and Type IV Settling

21. Types of Sedimentation Tanks

22. Sedimentation Tanks

23. Types of Sedimentation Tanks Horizontal Flow Tanks – Rectangular Tanks

24. Types of Sedimentation Tanks Horizontal Flow Tanks – Rectangular Tanks

25. Types of Sedimentation Tanks Horizontal Flow Tanks – Rectangular Tanks

26. Types of Sedimentation Tanks
Horizontal Flow Tanks – Rectangular Tanks Inlet

27. Types of Sedimentation Tanks
Horizontal Flow Tanks – Rectangular Tanks Inlet

28. Types of Sedimentation Tanks Rectangular Tanks-Settling Zone

29. Types of Sedimentation Tanks Rectangular Tanks-Sludge Zone

30. Types of Sedimentation Tanks Rectangular Tanks-Outlet

31. Types of Sedimentation Tanks Rectangular Tanks-Outlet

32. Types of Sedimentation Tanks Rectangular Tanks-Outlet

33. Types of Sedimentation Tanks Rectangular Tanks-Outlet

34. Types of Sedimentation Tanks
Circular Tanks

35. Types of Sedimentation Tanks
Circular Tanks

36. Types of Sedimentation Tanks Circular Tanks –Inlet Design

37. Types of Sedimentation Tanks Circular Tanks –Outlet Design

41. END