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.