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FACULTY OF ENGINEERING
DEPARTMENT OF CHEMICAL AND
METALLURGICAL ENGINEERING
CHEMICAL ENGINEERING LABORATORY
EXPERIMENT: _SEDIMENTATION
Name: MOFOKENG
L.S_____________________________________________________________
Student Number: _211131357___________________________________________________
Group: _5____________________________________________________________
Date Experiment Performed:8/032012__________________________________________
Date Experiment Submitted: _27/03/2012_________________________________________
Submitted to: _MR
Mosesane______________________________________________________
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TSHWANEUNIVERSITY OF TECHNOLOGY
DEPARTMENT OF CHEMICAL AND METTALURGICAL ENGINEERING
REPORT GRADING FORM
Name of Student: _MOFOKENG L.S
Student Number: 211131357
Title of Report: SEDIMENTATION
Term: _______________________________ DATE: __________________
Subject Max Mark Actual Mark
1. Title Page 1
2. Abstract 6
3. Introduction 2
4. Theoretical Background 3
5. Procedure 2
6. Results 6
7. Discussion of Results 10
8. Conclusion and Recommendations 4
9. Literature Cited 110. Nomenclature 1
11. Organization and Neatness 2
Appendix
A1 Raw Data 2
A2 Data analysis and SampleCalculations
10
TOTAL 50
Signed: ____________________________________
Comments:
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TABLE OF CONTENTS
ABSTRACTION..2 INTRODUCTION3 THEORY.4 EXPERIMENTAL..5-20 DISCUSSION..21 CONCLUSION AND RECOMMENDATION21 LITERATURE CITED.22
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ABSTRACT
The experiment is about supplementing particles that have poor settling
characteristics by increasing their size and mass through a process of coagulation
and flocculation. In this experiment coagulants used are aluminium and ferric
sulphate which are multivalent ions and are positively charged. For part A
different dosages of these salts are used (10g, 20g, 30g, 40g respectively) to
determine the optimum dosage, and it is found to be 20g. This shows that the
quantity of the coagulant does not have that much effect on coagulation itself.
Flocculation is the binding together of particles that are suspended in
wastewater. Flocculation aids coagulation which results in the formation of flocs.
In this experiment the 4 beakers are placed on a flocculator which then stirs the
solutions at different rotations per minute (rpm) to determine the pH and
turbidity at different time intervals for 20 minutes. Flocculation process acts as a
catalyst because it speeds up coagulation to fit the 20 minutes time slot.
The other factors that influenced the coagulation process is the addition of a base
and acid at part B. A very strong base (sodium hydroxide) and a strong acid
(sulphuric acid) are used to adjust the pH to determine the effect of alkalinity on
the coagulation process. This experiment shows that the higher the pH the clearer
the water which is shown by a small turbidity value. Thus the coagulation occurs
at a faster rate for basic solutions.
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INTRODUCTION
Coagulation and Flocculation removes particles that cannot be removed by
sedimentation and filtration alone. Coagulation is the addition of chemical
coagulants to supplement light particles while flocculation is the binding of very
fine particles in water by gentle mixing after the addition of a coagulant that aid
floc formation. These two processes go hand in hand. Most particles in
wastewater are negatively charged therefore the coagulants added are those of
the opposite charge (positively charged).
Chemicals that are commonly used as coagulants are aluminiumsulphate and iron
sulphate mainly because they possess positive ions (cations) that neutralize the
negatively charged particles to enable the particles to aggregate. The choice of
the coagulant depends on the following:
Suspended particles Wastewater conditions(temperature, pH e.t.c)
Treatment process Cost of coagulants necessary to yield the desired results
For particles to bind the flocculator must distribute a uniform energy throughout
the container in which this processes are taking place. Microflocs are brought
together by gentle mixing to form flocs that are heavier in mass and visible to the
naked eye. Once the flocs have reached the required size and mass a
sedimentation process immediately takes place.
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THEORY
A coagulation process is carried out on different jars with different dosagesof colaminate(10g, 20g, 30g and 40g each)
The rpm of the flocculator is set to decrease after certain time intervals indecreasing order for gentle mixing(250rpm, 60rpm, 25rpm)
Out of the 4 jars the jar with the optimum dosage is chosen and theexperiment is performed again, but with the same chosen dosage.
The pH of the sample is then adjusted by addition of sodium hydroxide orsulfuric acid depending on the initial value of pH to get required values of
pH(6, 7, 8, 9 respectively) on each jar.
Then the samples are calibrated to get the values of turbidity, after takingthe results graphs are constructed, they are as follows:
Turbidity v.s dosageInverse of turbidity v.s dosagepH v.s time log inverse of turbidity v.s time(Phv.s turbidity
After sketching all the graphs it is then when the rate of floc formation andthe influence on which the alkalinity or acidity has on floc formation.
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EXPERIMENTAL
1.APPARATUS Jar test apparatus and beaker Magnetic stirrer plus magnetic stirring bars Spectrophotometer or colour comparator Turbidity pH meter Assorted measurement syringes Stop watch Ringstands and rings
2.PROCEDUREPART A
Collect 20 to 40 litres of natural water or alternatively makeup synthetic water.
Pour 1litre of the water in each of the 4 beakers. Pour 0.228g of colominate on each of the 4 beakers. Set-up the flocculator for 250rpm before the addition of
coagulant.
Add aluminiumsulphateas a coagulant (10g, 20g, 30g and 40grespectively) on each beaker.
Measure the pH and turbidity of each beaker after 1min for250rpm, 9min for 60rpm, 4min for25rpm, 2min for 10rpm and
20min for 0rpm.
After the settling time of 20minutes, you add the indicatorphenolphthalein in all 4 beakers.
Mix 20g of NaOH in half a litre of water. Pour the mixture in each beaker until a change of colour is
observed.
Take the turbidity and dosage in all beakers.
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Measure the depth of the sludge that has settled.PART B
Choose the beaker with the optimum dosage.
Use the same chosen optimum dosage for all 4 beakers. Adjust the pH on each beaker to 6,7,8,9 respectively by
adding NaOH or H2SO4 depending on the initial pH.
Repeat the same procedure in part A. Measure the height of the sludge that has settled. Then measure the pH and turbidity.
3 .RESULT
TABLE :1
Temperature = 18.6
(constant)
Beaker 1 Beaker 2 Beaker 3 Beaker 4
pH 250
Rpm
8.61 8.54 8.47 8.47
Turbidity 335 257 271 271
1 min
pH 60
Rpm
8.33 5.32 8.30 8.28
Turbidity 355 428 502 453
9 min
pH 25
Rpm
8.21 7.96 8.01 7.96
Turbidity 873 888 68.1 135
4 min
pH 10
Rpm
8.07 8.62 8.27 8.20
Turbidity 663 97.3 103 220
2 min
pH 0
Rpm
7.20 7.22 7.22 7.75
Turbidity 565 39.5 22.5 26.2
20 min
Height (mm) 16 16 17 15
Colour
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TABLE :2
Temperature =21(constant) Beaker 1 Beaker 2 Beaker 3 Beaker 4
pH 250
Rpm
6.61 7.69 8.12 8.99
Turbidity 536 374 325 283
1 minpH 60
Rpm
6.60 7.73 8.16 8.97
Turbidity 625 479 854 417
9 min
pH 25
Rpm
6.70 7.73 5.16 8.98
Turbidity 603 105 244 196
4 min
pH 10
Rpm
7.73 7.75 8.18 8.98
Turbidity 240 88.6 32 85.2
2 min
pH 0Rpm
6.75 7.75 8.18 8.96Turbidity 52.4 39.5 14.6 33.3
20 min
Height (mm) 17 16 17 16
Colour Light Pink Medium Pink Pink Dark pink
0
0.001
0.002
0.003
0.004
0.005
0 10 20 30 40 50inve
rseofturbidity
dosage
Graph of inverse turbidity v.s
Dosage(1min)
Series1
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0
0.0005
0.001
0.0015
0.002
0.0025
0.003
0 10 20 30 40 50
inverse
turbidity
dosage
inverse of turbidity v.s dosage(9 min)
0
0.002
0.004
0.006
0.008
0.01
0.012
0.014
0.016
0 10 20 30 40 50
inv
erse
turbidity
dosage
inverse turbidity v.s dosage (4 min)
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0
0.02
0.04
0.06
0.08
0.1
0.12
0 10 20 30 40 50
inverse
turbidity
dosage
inverse of turbidity v.s dosage 2 min
0
0.01
0.02
0.03
0.04
0.05
0 10 20 30 40 50
inverse
tur
idity
dosage
inverse of turbidity v.s dosage (20
min)
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0
50
100
150
200
250
300
350
400
0 10 20 30 40 50
turbidity
dosage
turbidity v.s dosage (1 min)
0
100
200
300
400
500
600
0 10 20 30 40 50
tu
rbidity
dosage
turbidity v.s dosage 9 min
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0
100
200
300
400
500
600700
800
900
1000
0 10 20 30 40 50
turbidity
dosage
turbidity v.s dosage 4 min
0
100
200
300
400
500
600
700
0 10 20 30 40 50
t
u
r
b
i
d
i
t
y
dosage
turbidity v.s dosage 2 min
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-100
0
100
200
300
400
500
600
0 10 20 30 40 50
turbidity
dosage
turbidity v.s dosage 20 min
0
0.0005
0.001
0.0015
0.002
0.0025
0.003
0.0035
0 5 10 15 20 25
Inve
rse
ofturbidity
Time(min)
inverse turbidity Vs time B1
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-0.005
0
0.005
0.01
0.015
0.02
0.025
0.03
0 5 10 15 20 25
Inverse
ofturbidity
Time(min)
inverse turbidity Vs time B2
0
0.005
0.010.015
0.02
0.025
0.03
0.035
0.04
0.045
0.05
0 5 10 15 20 25
Inve
rse
ofturbidity
Time(min)
inv turb Vs time B3
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0
0.005
0.01
0.015
0.020.025
0.03
0.035
0.04
0.045
0 5 10 15 20 25
Inverse
oftu
rbidity
Time(min)
inverse turbidity Vs time B4
7
7.2
7.47.6
7.8
8
8.2
8.4
8.6
8.8
0 5 10 15 20 25
pH
Time
pH Vs time B1
pH
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0
1
2
3
4
5
6
7
8
9
10
0 5 10 15 20 25
pH
Time
pH Vs time B2
7.2
7.4
7.6
7.8
8
8.2
8.4
8.6
0 5 10 15 20 25
pH
Time
pH Vs time B3
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7.7
7.8
7.9
8
8.1
8.2
8.3
8.4
8.5
8.6
0 5 10 15 20 25
pH
Time
pH Vs timeB4
0
100
200
300
400
500
600
700
800
900
1000
0 5 10 15 20 25
Tuurbidity
Time
turbidity Vs time B1
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0
100
200
300
400
500
600
700
800
900
1000
0 5 10 15 20 25
Turbidity
Time
turbidity Vs time B2
0
100
200
300
400
500
600
0 5 10 15 20 25
Turbidity
Time
turbidity Vs time B3
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0
100
200
300
400
500
600
0 5 10 15 20 25
Turbidity
Time
turbidity Vs time b4
-3
-2.95
-2.9
-2.85
-2.8
-2.75-2.7
-2.65
-2.6
-2.55
-2.5
0 5 10 15 20 25
Loginverse
turbidity
Time
log inverse turbidity Vs time
(Beaker1)
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-3.5
-3
-2.5
-2
-1.5
-1
-0.5
0
0 5 10 15 20 25
Log
inverse
turbidity
Time
log inverse turbidity Vs time (beaker
2)
-3
-2.5
-2
-1.5
-1
-0.5
0
0 5 10 15 20 25
LogInverse
turbidity
Time
log inverse turbidity Vs time (beaker3)
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-3
-2.5
-2
-1.5
-1
-0.5
0
0 5 10 15 20 25
Loginverse
turbidity
Time
log inverse turbidity Vs time
(Beaker4)
0
10
20
30
40
50
60
0 2 4 6 8 10
Turb
idity
pH
turbidity v.s pH
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DISCUSSION
From the results it is observed that pH is inversely proportional to turbidity, this
means that basic solutions get clearer at a faster rate than acidic solutions. Beaker
1 showed to be less clearer than all the other beakers and it had a pH value of 6
which is acidic, the solution at beaker 4 was the most clear solution of them all
with the highest pH value of 9. The second beaker and third beaker did not differ
that much from each other as they were both close to neutrality and thus the
readings were roughly close.
The error which occurred was that of part A which resulted from the sample not
being calibrated properly, this resulted to a very complex structured table 1.1
which made it very hard to choose the optimum dosage. Thus turbidity in Part A
was misread. Beaker 2 was more reasonable and it complemented the theory
which explains the proportionality of pH and turbidity.
Part B came out as expected, pHwas adjusted with increasing order and the value
of turbidity is decreasing as pH increases. This shows that the more basic a
solution is the faster the settling time.
CONCLUSION AND RECOMMENDATIONS
pH is inversely proportional to turbidity, the particles settle faster for basic
solutions and slowly for acidic solutions. This experiment can be improved by
increasing the number of beakers and because it has to be done at certain timeintervals and fast more personnel is required. And also the sample calibrated has
got to be cleaned every time to ensure accurate results.
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LITERATURE CITED
1. Class Notes2. Hammer, Mark J., Water and Wastewater Technology, 2nd Ed., John Wiley
& Sons, New York, 1986
3. www.cityofsite.com