This experiment aims to discover the effect of initial concentration and initial height on sedimentation characteristics of calcium carbonate particles suspended in water. Data was collected for calcium carbonate suspensions at different concentrations (2-10%) and initial heights, measuring the settling velocity over time. The results show an inverse relationship between concentration and settling velocity, with higher concentrations settling more slowly. Higher initial heights also resulted in higher settling velocities compared to the same concentration at a lower initial height. Graphs of settling velocity versus limiting concentration were similar for all cases tested.

1. SEDIMENTATION
ELECCION, NICELY JANE R.
Department of Chemical Engineering
College of Engineering and Architecture
Cebu Institute of Technology – University
N. Bacalso Ave., Cebu City 6000
This experiment wants to discover the effect of the initial concentration and the initial
height on sedimentation characteristics specifically to plot the initial mass settling rate
against concentration, the rate of sedimentation at final consolidation on semi – log paper,
the settling velocity against the limiting concentration and to deduce that the graphs of
settling velocity against limiting concentration are similar for all cases. Sedimentation is
the process of letting suspended particles or solids settle through gravity. A particle in a
fluid settles eventually due to its higher density compared to the fluid in which it is
suspended. In the first part, different concentrations of the slurry were allowed to settle in
different cylinders. Data showed an inverse relationship between the concentration and
settling velocity. As the concentration increases, the rate of settling decreases. In the
second part, a certain concentration of slurry was allowed to settle in the cylinders but
varied in the initial heights. Data showed a direct relationship between the change in initial
heights and the settling velocity compared in the first part which was inverse.

2. 1. Introduction
Sedimentation, or clarification, is the process of allowing particles in suspension in
water to settle out of the suspension through gravity. Suspended material may be
particles, such as clay or silts, originally present in the source water. More commonly,
suspended material or floc is created from material in the water and the chemical used in
coagulation or in other treatment processes, such as lime softening. It is timely to note
that development of the theory of sedimentation is based on the initial assumption that
the particles to be removed from suspension are spherical and solid, whereas in practice,
they are irregular in shape, exist as a wide range in size and can be permeable to flow of
water.
This process is accomplished by decreasing the velocity of the water being treated
to a point below which the particles will no longer remain in suspension. When the velocity
no longer supports the transport of the particles, gravity will remove them from the flow.
Several factors affect the separation of settle-able solids from water. Some of the more
common types of factors to consider are: particle size, water temperature, currents, and
sedimentation basin zones.
This experiment aims to discover the effect of the initial concentration and the
initial height on sedimentation characteristics specifically to plot the initial mass settling
rate against concentration, the rate of sedimentation at final consolidation on semi – log
paper, the settling velocity against the limiting concentration and to deduce that the
graphs of settling velocity against limiting concentration are similar for all cases

3. 2. Materials and Methods
2.1 Equipment and Materials
 sedimentation apparatus
 mesh
 beaker
 spatula
 stirring rod
 powder of calcium carbonate.
2.2 Methods
The calcium carbonate was first sieved in order to achieve a uniform particle size
using a mesh. The calcium carbonate is then mixed with water in 5 different
concentration levels in 2%, 4%, 6%, 8%, and 10% by weight. Each of the slurry is then
placed in the sedimentation tubes at the same height. The readings were noted at
different time intervals until all calcium carbonates are completely settled down. The
slurries were then left for 24 hours to record the final compaction readings.

4. 3. Results with Calculations
Part A. Results for 2% calcium carbonate
Time (min)
Interphase
height
(mm)
Interphase
Height Intercept
(mm)
Settling Velocity
(mm/min)
Slurry Conc.
(kg/L)
1 222 403 181 0.044
4 45 133 22 0.218
9 32 45 1.444 0.306
19 22 38 0.842 0.445
49 18 30 0.245 0.544
94 17 27 0.106 0.576
154 17 27 0.065 0.576
1594 17 27 0.00627 0.576
Table 3.1 Tabulated values for 2% calcium carbonate
Settling Velocity calc:
𝑣1 =
403−222
1
= 181 𝑣4 =
38−22
19
= 0.842 𝑣7 =
27−17
154
= 0.065
𝑣2 =
133−45
4
= 22 𝑣5 =
30−18
49
= 0.245 𝑣8 =
27−17
1594
= 0.00627
𝑣3 =
45−32
9
= 1.444 𝑣6 =
27−17
94
= 0.106
Slurry Concentration Calc:
𝐶1 =
490(0.02)
222
= 0.044 𝐶3 =
490(0.02)
32
= 0.306 𝐶5 =
490(0.02)
18
= 0.544
𝐶2 =
490(0.02)
45
= 0.218 𝐶4 =
490(0.02)
22
= 0.445 𝐶6−8 =
490(0.02)
17
= 0.576

5. Results for 4% calcium carbonate
Time (min)
Interphase
height
(mm)
Interphase
Height Intercept
(mm)
Settling Velocity
(mm/min)
Slurry Conc.
(kg/L)
1 407 509 102 0.048
4 360 445 21.25 0.054
9 172 335 18.111 0.114
19 60 127 3.526 0.323
49 37 60 0.469 0.530
94 32 48 0.170 0.613
154 29 40 0.071 0.676
1594 29 40 0.0069 0.676
Table 3.2 Tabulated values for 4% calcium carbonate
Settling Velocity calc:
𝑣1 =
509−407
1
= 102 𝑣4 =
127−60
19
= 3.526 𝑣7 =
40−29
154
= 0.071
𝑣2 =
445−360
4
= 21.25 𝑣5 =
60−37
49
= 0.469 𝑣8 =
40−29
1594
= 0.0069
𝑣3 =
335−172
9
= 18.111 𝑣6 =
48−32
94
= 0.170
Slurry Concentration Calc:
𝐶1 =
490(0.04)
407
= 0.048 𝐶3 =
490(0.04)
172
= 0.114 𝐶5 =
490(0.04)
37
= 0.530
𝐶2 =
490(0.04)
360
= 0.054 𝐶4 =
490(0.04)
60
= 0.323 𝐶6 =
490(0.04)
32
= 0.613
𝐶7−8 =
490(0.04)
29
= 0.676

6. Results for 6% calcium carbonate
Time (min)
Interphase
height
(mm)
Interphase
Height Intercept
(mm)
Settling Velocity
(mm/min)
Slurry Conc.
(kg/L)
1 447 482 35 0.066
4 299 350 12.75 0.098
9 149 192 4.778 0.197
19 112 132 1.053 0.263
49 59 85 0.531 0.498
94 49 58 0.096 0.600
154 45 51 0.058 0.653
1594 42 46 0.00251 0.700
Table 3.3 Tabulated values for 6% calcium carbonate
Settling Velocity calc:
𝑣1 =
482−447
1
= 35 𝑣4 =
132−112
19
= 1.053 𝑣7 =
51−45
154
= 0.058
𝑣2 =
350−299
4
= 12.75 𝑣5 =
85−59
49
= 0.531 𝑣8 =
46−42
1594
= 0.00251
𝑣3 =
192−149
9
= 4.778 𝑣6 =
58−49
94
= 0.096
Slurry Concentration Calc:
𝐶1 =
490(0.06)
447
= 0.066 𝐶3 =
490(0.06)
149
= 0.197 𝐶5 =
490(0.06)
59
= 0.498
𝐶2 =
490(0.06)
299
= 0.098 𝐶4 =
490(0.06)
112
= 0.263 𝐶6 =
490(0.06)
49
= 0.600
𝐶7 =
490(0.06)
45
= 0.653 𝐶8 =
490(0.06)
42
= 0.700

7. Results for 8% calcium carbonate
Time (min)
Interphase
height
(mm)
Interphase
Height Intercept
(mm)
Settling Velocity
(mm/min)
Slurry Conc.
(kg/L)
1 463 509 46 0.085
4 385 461 19 0.102
9 270 389 13.222 0.145
19 189 287 5.158 0.207
49 106 197 1.857 0.370
94 71 131 0.638 0.552
154 63 103 0.279 0.622
1594 56 91 0.022 0.700
Table 3.4 Tabulated values for 8% calcium carbonate
Settling Velocity calc:
𝑣1 =
509−463
1
= 46 𝑣4 =
287−189
19
= 5.158 𝑣7 =
103−60
154
= 0.279
𝑣2 =
461−385
4
= 19 𝑣5 =
197−106
49
= 1.857 𝑣8 =
91−56
1594
= 0.022
𝑣3 =
389−270
9
= 13.222 𝑣6 =
131−71
94
= 0.638
Slurry Concentration Calc:
𝐶1 =
490(0.08)
463
= 0.085 𝐶3 =
490(0.08)
270
= 0.145 𝐶5 =
490(0.08)
106
= 0.370
𝐶2 =
490(0.08)
385
= 0.102 𝐶4 =
490(0.08)
189
= 0.207 𝐶6 =
490(0.08)
71
= 0.552
𝐶7 =
490(0.08)
63
= 0.622 𝐶8 =
490(0.08)
56
= 0.700

8. Results for 10% calcium carbonate
Time (min)
Interphase
height
(mm)
Interphase
Height Intercept
(mm)
Settling Velocity
(mm/min)
Slurry Conc.
(kg/L)
1 485 513 28 0.101
4 430 480 12.5 0.114
9 357 432 8.333 0.137
19 269 370 5.316 0.182
49 167 287 2.449 0.293
94 93 189 1.021 0.527
154 80 125 0.292 0.613
1594 67 106 0.024 0.731
Table 3.5 Tabulated values for 10% calcium carbonate
Settling Velocity calc:
𝑣1 =
513−485
1
= 28 𝑣4 =
370−269
19
= 5.316 𝑣7 =
125−80
154
= 0.292
𝑣2 =
480−430
4
= 12.5 𝑣5 =
287−167
49
= 2.449 𝑣8 =
106−67
1594
= 0.024
𝑣3 =
432−357
9
= 8.333 𝑣6 =
189−93
94
= 1.021
Slurry Concentration Calc:
𝐶1 =
490(0.1)
485
= 0.101 𝐶3 =
490(0.1)
357
= 0.137 𝐶5 =
490(0.1)
167
= 0.293
𝐶2 =
490(0.1)
430
= 0.114 𝐶4 =
490(0.1)
269
= 0.182 𝐶6 =
490(0.1)
93
= 0.527
𝐶7 =
490(0.1)
80
= 0.613 𝐶8 =
490(0.1)
67
= 0.731

9. Part B: Results for 4% calcium carbonate R=146 mm
Time (min)
Interphase
height
(mm)
Interphase
Height Intercept
(mm)
Settling Velocity
(mm/min)
Slurry Conc.
(kg/L)
0 155 155 0 0.038
1 112 152 40 0.053
4 24 56 8 0.247
9 15 20 0.556 0.395
19 13 18 0.263 0.455
49 12 16 0.082 0.493
1594 12 16 0.00251 0.493
Table 3.6 Tabulated values for 4% calcium carbonate R= 148 mm
Settling Velocity calc:
𝑣1 =
155−155
0
= 0 𝑣4 =
20−15
9
= 0.556 𝑣7 =
16−12
1594
= 0.00251
𝑣2 =
152−112
1
= 40 𝑣5 =
18−13
19
= 0.263
𝑣3 =
56−24
4
= 8 𝑣6 =
16−12
49
= 0.082
Slurry Concentration Calc:
𝐶1 =
148(0.04)
155
= 0.038 𝐶3 =
148(0.04)
24
= 0.247 𝐶5 =
148(0.04)
13
= 0.455
𝐶2 =
148(0.04)
112
= 0.053 𝐶4 =
148(0.04)
15
= 0.395 𝐶6−7 =
148(0.04)
12
= 0.493

10. Results for 4% calcium carbonate R=243 mm
Time (min)
Interphase
height
(mm)
Interphase
Height Intercept
(mm)
Settling Velocity
(mm/min)
Slurry Conc.
(kg/L)
0 255 255 0 0.038
1 209 253 44 0.047
4 91 177 21.5 0.107
9 29 77 5.333 0.335
19 23 29 0.316 0.423
49 17 20 0.061 0.572
1594 16 19 0.002 0.608
Table 3.7 Tabulated values for 4% calcium carbonate R= 243 mm
Settling Velocity calc:
𝑣1 =
253−209
1
= 44 𝑣4 =
29−23
19
= 0.316
𝑣2 =
177−91
4
= 21.5 𝑣5 =
20−17
49
= 0.061
𝑣3 =
77−29
9
= 5.333 𝑣6 =
19−16
1594
= 0.002
Slurry Concentration Calc:
𝐶1 =
243(0.04)
209
= 0.047 𝐶3 =
243(0.04)
29
= 0.335 𝐶5 =
243(0.04)
17
=0.572
𝐶2 =
243(0.04)
91
= 0.107 𝐶4 =
243(0.04)
23
= 0.423 𝐶6 =
2430.04)
16
= 0.608

11. Results for 4% calcium carbonate R=340 mm
Time (min)
Interphase
height
(mm)
Interphase
Height Intercept
(mm)
Settling Velocity
(mm/min)
Slurry Conc.
(kg/L)
0 357 357 0 0.038
1 305 353 48 0.045
4 171 305 33.5 0.080
9 47 123 8.444 0.289
19 32 37 0.263 0.425
49 25 30 0.102 0.544
1594 22 26 0.003 0.618
Table 3.8 Tabulated values for 4% calcium carbonate R= 340 mm
Settling Velocity calc:
𝑣1 =
353−305
1
= 48 𝑣4 =
37−32
16
= 0.263
𝑣2 =
305−171
4
= 33.5 𝑣5 =
30−25
49
= 0.102
𝑣3 =
123−47
9
= 8.444 𝑣6 =
26−22
1594
= 0.003
Slurry Concentration Calc:
𝐶1 =
340(0.04)
305
= 0.045 𝐶3 =
340(0.04)
47
= 0.289 𝐶5 =
243(0.04)
25
= 0.544
𝐶2 =
340(0.04)
171
= 0.080 𝐶4 =
340(0.04)
32
= 0.425 𝐶6 =
2430.04)
22
= 0.618

12. Results for 4% calcium carbonate R=442 mm
Time (min)
Interphase
height
(mm)
Interphase
Height Intercept
(mm)
Settling Velocity
(mm/min)
Slurry Conc.
(kg/L)
0 464 464 0 0.038
1 372 441 69 0.048
4 240 359 29.750 0.074
9 71 137 7.333 0.249
19 45 57 0.632 0.393
49 35 51 0.327 0.505
1594 27 42 0.009 0.655
Table 3.9 Tabulated values for 4% calcium carbonate R= 442 mm
Settling Velocity calc:
𝑣1 =
441−372
1
= 69 𝑣4 =
57−45
19
= 0.632
𝑣2 =
359−240
4
= 29.75 𝑣5 =
51−35
49
= 0.327
𝑣3 =
137−71
9
= 7.333 𝑣6 =
42−27
1594
= 0.009
Slurry Concentration Calc:
𝐶1 =
442(0.04)
372
= 0.048 𝐶3 =
442(0.04)
71
= 0.249 𝐶5 =
442(0.04)
35
= 0.505
𝐶2 =
442(0.04)
240
= 0.074 𝐶4 =
442(0.04)
45
= 0.393 𝐶6 =
442.04)
27
= 0.655

13. Results for 4% calcium carbonate R=484 mm
Time (min)
Interphase
height
(mm)
Interphase
Height Intercept
(mm)
Settling Velocity
(mm/min)
Slurry Conc.
(kg/L)
0 508 508 0 0.038
1 406 494 88 0.048
4 235 407 43 0.082
9 108 214 11.778 0.179
19 70 103 1.737 0.277
49 43 89 0.939 0.450
1594 33 71 0.024 0.587
Table 3.10 Tabulated values for 4% calcium carbonate R= 484 mm
Settling Velocity calc:
𝑣1 =
494−406
1
= 88 𝑣4 =
103−70
19
= 1.737
𝑣2 =
407−235
4
= 43 𝑣5 =
89−43
49
= 0.939
𝑣3 =
214−108
9
= 11.778 𝑣6 =
71−33
1594
= 0.024
Slurry Concentration Calc:
𝐶1 =
484(0.04)
406
= 0.048 𝐶3 =
484(0.04)
108
= 0.179 𝐶5 =
484(0.04)
43
= 0.450
𝐶2 =
484(0.04)
235
= 0.082 𝐶4 =
484(0.04)
70
= 0.277 𝐶6 =
484.04)
33
= 0.587

14. 4. Sketch

15. 5. Discussion
Sedimentation, or clarification, is the process of letting suspended material settle
by gravity. Sedimentation is characterized through the following parameters, which relate
to how they have been transported and weathered and how far from their original source
they have been deposited: (a) porosity – volume of voids within a bed which can contain
liquid, (b) permeability - the ability of water or other liquids (e.g. oil) to pass freely through
a material, (c) roundness - measure of the roughness of the surface of the sedimentary
grain, (d) sorting - relates to the range of particle sizes in a sediment, and (e) matrix - fine-
grained material (usually clays or silt) that is deposited originally with the coarser-grained
material.
Based on the gathered data in Part A, the change in the concentration of the slurry
affects the value of the settling velocity. It is observed that the height of the sludge
decreases slowly as the concentration of the slurry increases. The settling velocities were
obtained by getting the difference of the initial height of the sludge (calcium carbonate)
and the interphase height over the time interval recorded. It is also observed that the final
concentration recorded is lesser than the original concentration and this is because some
of the calcium carbonate are dissolved in water. In part B, the different initial heights
affects the values of the settling velocity. It is observed in tables 6 – 10 that the settling
velocity values increases as the initial height increases in the different trials.

16. 6. Conclusion
One of the commonly used unit operation in the industry is sedimentation because
it’s cheap and is efficient in separating solid and liquid phases. The change in
concentration of the slurry has a great impact on the settling velocity due to a greater
velocity gradient in the fluid surrounding the particles whereby a closer proximity of the
particles is evident. The rise of the initial heights also affects the settling velocity due
again to velocity gradients in the fluid surrounding the particles, this time, lesser compared
to part A. The change in initial height explains that the particles in the slurry are even
more scattered and the amount of particles is constant compared to part A. This would
mean that free settling is more favorable. Stokes law can be applied for this experiment
because of the very low settling velocities gathered and would mean the settling of
particles is having a laminar behavior.
7. Recommendation
In this experiment, there are several precaution we must take to avoid and prevent
errors to occur. Ensure the clarity of the glass apparatus since the one present in the
laboratory is not that clear anymore and the markings are also not clear which may result
to erroneous reading of values. The cylinders also are needed to be replaced. The lights
are not that bright enough to see the tip of the height of the sludge so make sure there is
a good lighting in the area in order to visibly see the height of the sludge.

17. 8. References
[1] Geankoplis, C.J. (2009) Principles of Transport Processes and Separation
Processes. 1st edition. Pearson Education South Asia PTE. LTD.
9. Web References
[1] Graham, I. (2010, January 27). Characteristic of Sediments. Retrieved March 12,
2018, from https://australianmuseum.net.au/characteristics-of-sediments
[2] Britannica, T. E. (2017, December 05). Sedimentation. Retrieved March 12,
2018, from https://www.britannica.com/science/sedimentation-geology