jet jar test
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UJIAN
BALANG
ISI KANDUNGAN
NO ISI KANDUNGAN MS
1 Objektif
2 Peralatan
3 Prosedur
4 Data
5 Perbincangan
6 Kesimpulan
OBJEKTIF
Pelajar seharusnya dapat :-
mengenal pasti kekeruhan sebagai respon dengan menggunakan prosedur Ujian Balang.
PERALATAN DAN BAHAN
Figure 1: ALATAN UJIAN BALANG
Figure 2: SAMPEL TANAH
PROSEDUR
The experiments (OFAT or RSM) were conducted according to the typical Jar Test procedure. It
consists of rapid stirring (60 – 80 rpm) of the samples after chemical addition for one minute,
followed by slow mixing (10 to 30 rpm) for about 15 minutes. After the stirring period is over, stop
the stirrer and allow the flocs to settle for about 30 minutes. Pipette 10 mL of cleared sample from
each beaker and measure its turbidity using the turbid meter.
One-Factor-At a-Time
One-Factor-At a-Time experiment consists of 18 experimental runs. The flow chart of the OFAT
experiment is shown in Figure 3.4, while the experimental conditions are given in Table 3.1. A
volume of 500 mL of distilled water was added in each of six beakers and mixed with 20 mg of soil
sample. Alum solutions at different dose (20 mg/L, 40 mg/L, 60 mg/L, etc.) were added into each
beaker. For the first set of six runs, the pH value was fixed to 7.0. The dose of alum was varied in
each beaker for 20 mg/L to 120 mg/L. The water was rapid mixed at approximated 80 rpm for one
minute followed by slow mixing at 30 rpm for approximates 15 minutes. At the end of mixing
period, the floc was let settled for about 30 minutes. The turbidity in each sample was immediately
analysed. The best dosage was determined based on the lowest final turbidity. Figure 3.3 shows the
raw water sample before and after experiment conducted. The second set of experiments was
conducted using the best dosage of the first at different pH following the procedures as detailed
before. The best pH was obtained based on the lowest turbidity value. The third set was runs at pH4.0
as a comparison to the first set of experiment.
Figure 3: Raw water sample before and after experiment
Flow chart for OFAT experiment
Three sets of OFAT experiment with a total of 18 runs.
Set 1
Set 2
Set 3
RUN pH Coagulant (mg/L)
OFAT 1 OFAT 2 OFAT 3 OFAT 4 OFAT 5 OFAT 6
7.0 7.0 7.0 7.0 7.0 7.0
20 40 60 80 100 120
OFAT 7 OFAT 8 OFAT 9 OFAT 10 OFAT 11 OFAT 12
5.0 5.5 6.0 6.5 7.0 7.5
100 100 100 100 100 100
OFAT 13 OFAT 14 OFAT 15 OFAT 16 OFAT 17
4.0 4.0 4.0 4.0 4.0
20 40 60 80 100
SET ONE The best dosage was determined based on the lowest final turbidity
SET TWO Using the best coagulant dosage of set one.
SET THREE As a comparison to set one with pH4
OFAT 18 4.0 120
Response Surface Design
The experimental work for response surface was statically designed using Central Composite
Rotatable Design with the aid of MINITAB TM software. The experiments were divided into 13 runs
as shown in Table 3.2. The ranges of pH and coagulant dosage follow those conducted in OFAT
approach. Run of RSM 9 to RSM 13 are repetition for the calculation of the residual error in the
analysis to avoid bias, the experiment were conducted in a random manner. The experiments
procedures are similar to those in previous OFAT experiment.
Experimental runs conducted using Response Surface Method
RUN pH Coagulant (mg/L) RSM 1 4.6 34 RSM 2 4.6 106 RSM 3 7.4 34 RSM 4 6.0 20 RSM 5 7.4 106 RSM 6 6.0 120 RSM 7 4.0 70 RSM 8 8.0 70 RSM 9 6.0 70
RSM 10 6.0 70 RSM 11 6.0 70 RSM 12 6.0 70 RSM 13 6.0 70
DATA DAN PENGIRAAN
ONE-FACTOR-AT A-TIME
The results of the experiments are shown in Table 4.1. The final turbidity ranges from 0.20 NTU to
1.30 NTU and the ranges of coagulant dosage between 20 mg/L to 120 mg/L. The lowest final achieved
turbidity in set one is 0.50 NTU with coagulant dosage of 100 mg/L of pH7.0. Using alum dosage of 100
mg/L, the lowest turbidity achieved in set two was 0.20 NTU when the pH equal to 6.5. However, the
lower final turbidity of 0.25 NTU was obtained when the coagulant dosage of 100 mg/L when the pH was
set to 4.0.
Figure 4.1 illustrate the final NTU at pH 4 and pH 7 as a function of coagulant dosage. The final
turbidity at pH 4.0 (0.25 NTU) is much lower than the final turbidity achieved at pH 7.0 (0.50 NTU)
although both coagulant dosage is equal. It shows that if only two sets of experiment were conducted as in
normal procedure, the final turbidity obtained was not the lowest one. There seem to be found that the
interaction affect in the process which is not disclosed by the OFAT approach.
Final Turbidity (NTU) versus Coagulant Dosage (mg/L)
Figure 4 :The final NTU at pH 4.0 and pH7.0.
The results of the OFAT experiments
SET RUN pH Coagulant (mg/L)
Final Turbidity (NTU)
1 OFAT1 OFAT2 OFAT3 OFAT4 OFAT5 OFAT6
7.0 7.0 7.0 7.0 7.0 7.0
20 40 60 80
100 120
1.20 1.03 0.86 0.70 0.50 0.54
2 OFAT7 OFAT8 OFAT9 OFAT10 OFAT11 OFAT12
5.0 5.5 6.0 6.5 7.0 7.5
100 100 100 100 100 100
0.85 0.53 0.32 0.20 0.22 0.24
3 OFAT13 OFAT14 OFAT15 OFAT16 OFAT17 OFAT18
4.0 4.0 4.0 4.0 4.0 4.0
20 40 60 80
100 120
1.30 1.26 0.90 0.56 0.25 0.26
RESPONSE SURFACE DESIGN
The result of response surface method is given in Table 4.2. The ranges of final turbidity
achieved in response surface experiments is 0.02 NTU to 3.21 NTU with coagulant dosage ranges
from 20 mg/L to 120 mg/L and pH from 4.0 to 8.0. The lowest final turbidity for response surface
experiments in Table 3 was 0.02 NTU in RSM 5, when the coagulant dosage was 106 mg/L and the
pH is 7.4. The final turbidity achieved in response surface experiment (0.02 NTU) is much lower
than OFAT experiment (0.20 NTU). The percentage differences between both lowest final turbidity
OFAT and response surface experiment are 90 %.
Table 4.3 summarizes the results of the analysis using MINITABTM software. It shows that the
dosage of the coagulant and pH were significant factors in the coagulation process at confidence
level of 95%. The two ways interaction, coagulant dosage * pH (p = 0.0020), and two main effects
coagulant dosage (p = 0.0000) and pH (p = 0.0000) is significant, and the square term (coagulant
dosage * coagulant dosage) and (pH * pH) also significant, p=0.0000. The square term indicate the
non-linear characteristic of the coagulation behavior
Turbidity results for RSM experiments
RUN pH Coagulant (mg/L) Final Turbidity (NTU)
RSM1 RSM2 RSM3 RSM4 RSM5 RSM6
4.6 4.6 7.4 6.0 7.4 6.0
34 106 34 20 106 120
3.21 1.10 1.15 2.14 0.02 0.087
RSM7 RSM8 RSM9 RSM10 RSM11 RSM12
4.0 8.0 6.0 6.0 6.0 6.0
70 70 70 70 70 70
2.60 0.10 0.50 0.50 0.50 0.50
RSM13 6.0 70 0.50 .
Result of the analysis for response surface using MINITABTM software
Term Coefficient Sum of Error Coefficient
T Test P
Constant 0.5000 0.04539 11.016 0.0000 Dosage of Coagulant -0.7692 0.03588 -21.436 0.0000
pH -0.8344 0.03588 -23.255 0.0000 Coagulant x Coagulant 0.3400 0.03848 8.836 0.0000
pH x pH 0.4600 0.03848 11.955 0.0000 Coagulant x pH 0.2450 0.05074 4.828 0.0020
Analysis of variance for turbidity
Source DF Seq. SS Adj. MS F P *Linear 2 10.3032 5.15160 500.16 0.000 *Square 2 2.0268 1.01342 98.39 0.000
*Interaction 1 0.2401 0.24010 23.31 0.002 Residual Error 7 0.0721 0.01030
Total 12 12.6422
*Linear: coagulant dose and pH,
*square: coagulant2 and pH2,
*Interaction: Coagulant dose x Ph
The analysis of variance in Table gives a summary of the main effect (linear and square) and
interaction. The total sum of squares is 12.6422 (linear=10.3032, square=2.0268, interaction=0.2401)
with total of 12 degree of freedom.
A relationship between the dose and pH and the final turbidity could be described as
Final Turbidity = 17.35 - 0.17 Coagulant - 3.75 pH + 0.001 Coagulant2 + 0.23 pH2 + 0.01 Coagulant x
pH
‘
PERBINCANGAN
KESIMPULAN
Response surface design is a more effective way to determine the impact of two or more factors on a
response than a One-Factor-At a-Time (OFAT) experiment, where only one factor is changed at one
time while the other factors are kept fixed. So, basically the conclusions that can be drawn from this
study are as follow:
1. In OFAT experiment, the lowest final turbidity achieved in set one is 0.50 NTU with
coagulant dosage of 100 mg/L at pH 7.0 and final turbidity achieved in set two was 0.30
NTU when the pH equal to 6.5 and the coagulant dosage of 100 mg/L. If only two sets of
experiment were conducted as in normal procedure, the final turbidity obtained was not the
lowest one.
2. In response surface method experiment, the lowest final turbidity achieved was 0.02 NTU in RSM 5 (Table 4.2), when the coagulant dosage was 106 mg/L and the pH is 7.4.
3. For response surface analysis, the coagulant dosage and pH were significant factors in the coagulation process at the confidence level of 95%.
4. The two ways interaction, coagulant dosage * pH (p = 0.0020), and two main effects coagulant dosage (p = 0.0000) and pH (p = 0.0000) is significant, and the square term (coagulant dosage * coagulant dosage) and (pH * pH) also significant, p=0.0000. The square term indicate the non-linear characteristic of the coagulation behavior.
5. A relationship between the coagulant dose and pH and the final turbidity could be described
as, 17.35 - 0.17 Coagulants - 3.75 pH + 0.001 Coagulant2 + 0.23 pH2 + 0.01 Coagulant x pH
6. The lowest turbidity, 0.01 NTU (Figure 4.1 and Figure 5.2) are found where pH and coagulant dosage both at their high setting. As the pH and coagulant dosage move backward
on their lower setting, the value of turbidity increased.
7. As overall conclusion, the better water quality could be achieved using response surface design rather than OFAT experiment. The interaction between the factors and response can be estimated for the response surface design, but it cannot be estimated for the OFAT experiment.
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