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Journal of Sustainable Civil Engineering and Technology
e-ISSN: 2948-4294 | Volume 1 Issue 2 (September 2022), 8-16
https://joscetech.uitm.edu.my
8
The Efficiency Assessment of Poly-Aluminium Chloride (PAC) in Water
Treatment Plant Process: A Case Study at Sultan Iskandar Water
Treatment Plant, Johor
Aina Asyura Azhar1, Nuryazmeen Farhan Haron1*, Herda Balqis Ismail2
1School of Civil Engineering, College of Engineering, Universiti Teknologi MARA, 40450 Shah Alam,
Selangor, Malaysia.
2School of Civil Engineering, College of Engineering, Universiti Teknologi MARA Pasir Gudang, Johor,
Malaysia.
*Corresponding author E-mail address: nuryazmeen@uitm.edu.my
Received: 01 September 2022 / Accepted: 18 September 2022 / Published online: 30 September 2022
Abstract
The rate of population growth and river pollution are significant factors contributing to the increase in water
demand in Johor. Generally, this may affect the quality of water treated at one of the biggest water treatment
plants in Johor namely Sultan Iskandar Water Treatment Plant (SIWTP). The coverage of SIWTP water supply
is wide and comprise almost all area of Pasir Gudang and half of the Johor Bahru district. This situation
indirectly affects consumer demand when the treated water is insufficiently supplied by the potable water supply
provider due to the use of conventional coagulants in the water treatment plant process. Therefore, this is an
initial study as the Poly-Aluminium Chloride (PAC) coagulant is still in the early stages of implementation at
SIWTP. It is important to determine the performance of PAC coagulant in the coagulation-flocculation process
of the water treatment plant. The PAC performance is compared to Aluminium Sulphate which is a common
type of coagulant used in the treatment plant, in order to establish efficiency. A pH adjustment test, turbidity
test and the residual Aluminium test were conducted for both coagulants and six jar test readings were recorded
to plot the comparison graph between PAC and Alum coagulants. The results showed that PAC is more efficient
with 83.74% as compared with Alum which has an efficiency rate of 83.35%. Even though the difference is too
small, it is concluded that PAC has better performance and is more efficient compared to Alum due to its better
coagulation performance. In addition, PAC produces lesser residual Aluminium and required a lesser amount
of dosage. This may reduce cost and therefore save overall operating costs.
Keywords: PAC, Alum, coagulant, performance, efficiency, Sultan Iskandar WTP
1. Introduction
Water is an essential component for humans and other living things, including flora and fauna. The increasing
number of residents directly influences the demand for water supply. This is to fulfil the water consumption of
the community. However, the increase in demand is not offset by the availability of clean water due to the low
water quality of water produced by the water treatment plant. This is because, small, suspended particles, known
as colloids, cannot be naturally settled, or eliminated in water bodies due to their modest weight and stability.
Therefore, it is necessary to have an alternative water treatment so that the clean water demand can be sufficient.
In general, polluted water has a higher level of turbidity. The level of turbidity in raw water is important because
it is referred to as an indication of water quality. Higher turbidity can make water appear cloudy, opaque or
Journal of Sustainable Civil Engineering and Technology
e-ISSN: 2948-4294 | Volume 1 Issue 2 (September 2022), 8-16
https://joscetech.uitm.edu.my
9
murky. This is because the existing chemical used in Sultan Iskandar Water Treatment Plant (SIWTP) is
Aluminium Sulphate (Alum). Based on the previous study, the formation of floc produced by Alum is
particularly fragile (McCurdy et al., 2004; Aziz et al., 2017; Kumar et al., 2020; Liu et al., 2021; Nti et al.,
2021). This can make the process of flocculation insufficient. When this happens, the turbidity of the water can
be higher.
Recently, a chemical known as a coagulant, namely Poly-Aluminium Chloride (PAC), is becoming an option
or alternative to be used in the market. According to Kumar & Balasundaram (2017), Zhang et al. (2014, 2018),
and Kim et al. (2022), PAC coagulant has better performance due to its effectiveness in treating a wide range
of water as it can form flocs at a relatively low cost. This can assist the coagulation-flocculation process to
operate sufficiently. Coagulation and flocculation are vital processes in water treatment whereby the colloidal
matter is formed in a suspended solid to cause it to agglomerate. When the clump between suspended solid
becomes large and heavier, it will naturally settle via gravitational settling at the bottom of the basins to form a
floc. An effective turbidity removal is required in order to ensure the clarity of treated water and the removal of
health-related contaminants. In general, the effectiveness can be measured with the rapid formation of flocs.
Therefore, the aim of this study is to determine the effectiveness of PAC as an alternate coagulant using
theoretical and laboratory evidence. Besides, this study will also evaluate the performance of PAC at various
pH values and coagulant dosages. This is to find an optimal operational condition in the treatment process when
dealing with various turbidity levels in the water. The influence of hydrated lime, as a coagulant aid that helps
in the flocculation process, together with PAC, will also be determined.
2. Literature Review
The PAC performance can be measured on its base properties known as basicity. Basicity is one of the
parameters that can affect the result of performance in the coagulation-flocculation process and influence the
properties of PAC (McCurdy et al., 2004; Zand & Hoveidi, 2015; Aziz et al., 2017; Kumar & Balasundaram,
2017; Zhang et al., 2018). In general, basicity is a basic medium of PAC used to remove impurities or acidity
from water. The efficiency of turbidity removal is increased with increasing the PAC basicity. Hence, the result
indicates that higher basicity in PAC can benefit the turbidity removal process. This finding is supported by
Zhao et al. (2015), which found that higher basicity consumption can improve turbidity removal in raw water.
High basicity has been optimized for turbidity removal by controlling the formation of Aluminium ions in the
PAC coagulant. Therefore, higher basicity can reduce the consumption of alkalinity in the treatment process,
thus giving an impact on the pH of raw water. In practice, further in situ studies using this coagulant in water
treatment are needed in order to investigate the best properties and performance that may be beneficial to the
industry.
There are several previous studies have discovered the efficiency of PAC as a coagulant in treating wastewater.
For example, a study conducted by Aziz et al. (2017) using PAC and Alum in the wastewater treatment plant
of a hospital in Indonesia provides evidence that PAC is more effective than Alum. It also shows that PAC can
perform well with a high turbidity level and a wide pH range from 7 to 8, when compared to Alum (Kumar &
Balasundaram, 2017). Therefore, it is beneficial to explore the PAC performance in the water supply treatment
process.
In the future, by taking into consideration the high tendency of natural disasters to be occurred such as floods,
PAC can be one of the best options to be adopted. This is because many water treatment plants need to be closed
due to the high turbidity (NTU) due to the flooding event. During the monsoon season in December 2021, many
water treatment plants were closed. For example, the issue faced by the water treatment plant at Port Dickson
of the low water pressure in some parts due to the problem of high raw water turbidity (NTU) at the Sungai
Linggi Water Treatment Plant (Ahmed et al., 2014). The high-water turbidity rate (NTU) has forced production
to be reduced from normal in order to meet national drinking water quality standards. This influences the water
supply issue in the residential area. As a precaution, PAC is recommended for use at the SIWTP because it can
Journal of Sustainable Civil Engineering and Technology
e-ISSN: 2948-4294 | Volume 1 Issue 2 (September 2022), 8-16
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10
efficiently reduce turbidity levels and has been shown to be more effective than Alum. In addition, this may
reduce the potential of water shortages during disasters.
3. Study Area
This study was conducted at the Sultan Iskandar Water Treatment Plant (SIWTP). The SIWTP is located in
Pasir Gudang, Johor. In general, there are two main plants in SIWTP. The water from Sungai Johor, Sungai
Tiram, and Sungai Seluyut had been retained at the Upper Layang Dam as illustrated in Figure 1. The raw water
from this reservoir has become the main source of intake for SIWTP. Based on the observations made at the
Upper Layang Dam as shown in Figure 2, the development and agricultural activities have had an impact on
the quality of water retained in the reservoir. This is due to agricultural runoff water containing ammonia,
nitrates and phosphates entering the water catchment area. The water turned green colour, which caused algae
to breed. Furthermore, the level of water quality is dropping as a result of the high turbidity level. The pH of
water also becomes more acidic which is caused by various contaminants such as chemical fertilizer etc
(Dongre, 2018).
Figure 1. SIWTP as study area located at Pasir Gudang, Johor Malaysia (Source: Google Earth)
Journal of Sustainable Civil Engineering and Technology
e-ISSN: 2948-4294 | Volume 1 Issue 2 (September 2022), 8-16
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11
Figure 2. Location of the Sultan Iskandar Reservoir (Upper Layang Dam) where the development and
agricultural activities influence the reservoir water quality (Source: Google Earth)
4. Methods
In this study, PAC and Aluminum Sulphate were the two types of coagulants used. The jar test method was
used to simulate the mixing chamber tank at SIWTP. A pH adjustment test, turbidity test and residual
Aluminium test were conducted to determine the effectiveness of the coagulant dosage. Mainly, the raw water
sample was directly taken from the Upper Layang reservoir of the SIWTP.
In order to evaluate the effectiveness of coagulants, a comparison was made between two coagulants. The same
procedure was conducted using both coagulants whereby a constant value of hydrated lime (5 mg/L) was used
and added in the six-number of jar test for each type of coagulant mixture. The initial dosage used for PAC is
between 2 mg/L and 50 mg/L, and the chosen dosage is from 20 mg/L. It is because, from the trial experiment,
it has been observed that the floc only appears after 20 mg/L is added. Six readings were recorded to plot the
comparison graph between PAC and Alum coagulants. From the plotting graph, the effectiveness of PAC was
analysed by comparing the efficiency percentages of PAC and Alum. The efficiency percentage of PAC was
calculated by using the formula in Equation 1. The calculation is using the turbidity result obtained from the jar
test for both PAC and Alum. The complete data was then used to plot the graph.
Efficiency Percentage = (𝐼𝑛𝑖𝑡𝑖𝑎𝑙 𝑡𝑢𝑟𝑏𝑖𝑑𝑖𝑡𝑦−𝐹𝑖𝑛𝑎𝑙 𝑡𝑢𝑟𝑏𝑖𝑑𝑖𝑡𝑦 )
𝐼𝑛𝑖𝑡𝑖𝑎𝑙 𝑡𝑢𝑟𝑏𝑖𝑑𝑖𝑡𝑦 ×100% (1)
In general, the efficiency was calculated based on the turbidity measurement. When the value of turbidity is
low, it shows the effectiveness of the amount dosage used. The dosage used has the ability to form a high
volume of floc. In this study, the Ranhill SAJ Standard requirements as shown in Table 1 was referred to as the
basis. This is because the findings may provide insight into the SIWTP operation.
Journal of Sustainable Civil Engineering and Technology
e-ISSN: 2948-4294 | Volume 1 Issue 2 (September 2022), 8-16
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Table 1. Ranhill SAJ Standard Requirements (Source: Report of Ranhill SAJ Standard, unpublished)
No.
Parameters
Unit
Raw Water
Sedimentation
Water
Filtered
Water
Treated
Water
1
pH
5.5-9
5.5-6.7
-
6.5-7.8
2
Turbidity
NTU
1000
3-7
1
2
3
Color
TCU
300
-
-
13.5
4
Aluminium
mg/L
-
-
0.05
0.05
5
Iron
mg/L
1
-
-
0.2
6
Ammonia
mg/L
1.5
-
-
0.1
7
Manganese
mg/L
0.2
-
-
0.05
8
Fluoride
mg/L
-
-
-
0.40-0.06
9
Residual
Chlorine
mg/L
-
-
-
0.2-5
5. Results and Discussion
In this experiment, aluminium-based compounds, and polymers such as PAC and Alum are used for
coagulation-flocculation to treat most surface and infiltration water. This process is important in water treatment
to reduce turbidity, colour, organic matter, and microorganism levels by creating aggregates and flocs from
finely divided particles or dissolved substances (Mandal, 2014). Table 2 shows the comparison results between
PAC and Aluminium Sulphate coagulants used to treat the water sample from six jars. The addition of 5 mg/L
hydrated lime in the PAC mixture ranges from 20 mg/L to 26 mg/L, meanwhile for the Alum mixture, the
addition of lime ranges from 42 mg/L to 52 mg/L. The pH in the PAC mixtures of all jars shows a consistent
alkali value ranging from 6.47 to 6.54 except for the jar with 20 mg/L PAC, which shows 6.26. Besides, the pH
value of the Alum coagulants decreases from 6.37 to 5.90 for each additional 5 mg/L of hydrated lime at each
jar test. Overall, the pH of treated water using PAC coagulant lies within the range of 6.5 to 7.8, as shown in
Table 2. On the other hand, Alum sufficiently lowered the pH but requires additional chemicals to adjust the
pH to comply with the Ranhill SAJ standard.
In terms of turbidity, the lowest value is recorded at 1.26 NTU when the PAC is 23 mg/L. Meanwhile, the pH
value of Alum coagulant is decreased from the initial dosage (42 mg/L) to the highest Alum dosage used in this
study (52 mg/L). In addition, the lowest value of turbidity is 1.29 NTU, when 46 mg/L Alum is added to the
mixture. Generally, for both coagulants, it was found that when the dosage of the coagulant exceeded the
optimum value, charge reversal occurred, causing the turbidity and colour to reappear. Therefore, the lowest
turbidity value indicates the optimum dosage of coagulant required for the jar test.
Journal of Sustainable Civil Engineering and Technology
e-ISSN: 2948-4294 | Volume 1 Issue 2 (September 2022), 8-16
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Table 2. Comparison of optimum dosage between Aluminium Sulphate and PAC
Jar
Chemical Mixture
(mg/ L)
Sedimentation
Water
Efficiency of
Optimum
Coagulant
(%)
Lime
Dosage
pH
Turbidity
(NTU)
Aluminium
1
PAC
5
20
6.26
1.60
0.067
79.35
Alum
42
6.37
2.36
0.070
69.55
2
PAC
5
22
6.54
1.45
0.048
81.29
Alum
44
6.09
2.32
0.032
70.06
3
PAC
5
23
6.50
1.26
0.026
83.74
Alum
46
6.00
1.29
0.030
83.35
4
PAC
5
24
6.47
1.32
0.021
82.97
Alum
48
5.97
1.40
0.027
81.94
5
PAC
5
25
6.49
1.50
0.069
80.65
Alum
50
5.92
1.48
0.080
80.90
6
PAC
5
26
6.50
1.74
0.078
77.55
Alum
52
5.90
1.76
0.092
77.29
Besides, the results show that Alum which undergoes alkaline hydrolysis in water increases the residual
Aluminium by 0.030 at 46 mg/L. The residual Aluminium may increase with an increase in coagulant dosage.
Analysis of the relationship presented in Table 2 showed that both coagulants, PAC and Alum caused an
increase in the concentration of Aluminium in the water following the coagulation process. However, at the
optimum dosage, PAC indicates lower residual Aluminium with 0.026 at 23 mg/L compared to the Alum value.
This is because, Alum coagulants could combine with residual Natural Organic Matter (NOM) during the
coagulation process and significantly raise the residual level of Aluminium (Wang et al., 2010). Besides, it has
been reported that improper coagulations of hydrolysing Aluminium coagulants ensure low efficiency of
impurities removal and at the same time cause an excessive concentration of residual Aluminium in treated
water. The higher residual Aluminium after the process may reduce disinfection efficiency (Kang et al., 2003).
In addition, the capacity of the water distribution system may be reduced due to the clogging of residual
Aluminium in the pipe network.
Figure 3 shows a graph of turbidity (NTU) versus coagulant dosage (mg/L) in this study. The data that was
used to plot this graph is shown in Table 2. Based on the results, PAC achieves 1.26 NTU at a relatively lower
dosage of less than 23 mg/L, whereas Alum achieves 1.29 NTU at a dosage of 46 mg/L. The trends observed
in this study are consistent with the findings of Hoko & Makado (2011), which discovered that the general trend
of both coagulants is that residual turbidity is reduced by increasing dosage until the optimum dosage is reached.
The results also show that reducing the pH values for six jar samples with Alum coagulant is more effective
than PAC. This is consistent with the findings of Tzoupanos & Zouboulis (2008). Another study by Gebbie
(2006) reported that when Alum is dissolved in water, it may produce Aluminium hydroxide with the additional
product of sulphuric acid. Then, the formation of sulphuric acid reacts with alkalinity in raw water to produce
carbon dioxide, thus decreasing the pH value. However, PAC coagulants maintained the pH range (the range
from 6.5 to 7.8) while Alum reduced it. This needs a pH correction for Alum at later stages of treatment, which
may increase the requirement for hydrated lime. Therefore, this is beneficial in terms of cost because the
acquired cost can be reduced by adjusting or improving the pH when using PAC since the adjustment and
addition of hydrated lime have been decreased.
Journal of Sustainable Civil Engineering and Technology
e-ISSN: 2948-4294 | Volume 1 Issue 2 (September 2022), 8-16
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14
Figure 3. Graph of the comparison data of optimum dosage between PAC and Alum coagulant
Figure 3 shows the optimum dose of PAC and Alum coagulant. The point of minimum settled water turbidity
represents the potential value of coagulant treatment and indicates the optimum coagulant dosage for jar test
experiments. In addition, the graph shows that the optimum value of PAC is 23 mg/l. Meanwhile, the graph
also indicates that the optimum value of Alum is 46 mg/L.
Figure 4. Graph of the efficiency analysis of coagulant
Journal of Sustainable Civil Engineering and Technology
e-ISSN: 2948-4294 | Volume 1 Issue 2 (September 2022), 8-16
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From the analysis, turbidity removal for PAC coagulant achieved a higher efficiency of 83.74% compared to
Alum, which has the lowest efficiency of 83.35%, as shown in Figure 4. The efficiency was 83.74% at a dosage
of 23 mg/L of PAC and 83.35% at a dosage of 46 mg/L of Alum. Both coagulants were found to significantly
reduce water turbidity. However, in this study, PAC performs better in terms of reducing the turbidity of the
raw water. This finding was supported by Tzoupanos & Zouboulis (2008), which discovered that PAC
coagulants are highly effective in treating polluted water with higher turbidity. In addition, the advantage of
using PAC over Alum is that PAC works well in the formation of flocs at pH 6.47, whereas Alum works better
at pH 6.00. This is supported by previous findings, where the PAC pH range is wide (6 to 9) compared to the
Alum which has a pH range of 6.5 to 7.6. In addition, treated water also has good quality and has a quicker
reaction speed in clumping the suspended solid due to its liquid state (Kumar & Balasundaram, 2017).
Furthermore, PAC can operate at any raw water turbidity level and produce lower residual Aluminium content.
6. Conclusions
In general, the slight difference between PAC and Alum percentages of turbidity removal efficiency is crucial
to be observed in this experiment. This is because, based on the study, SIWTP faced an issue with higher
turbidity and pH of the water, which was caused by environmental pollution. The source of intake water is
channelled from the river which is located in the industrial hub area. Therefore, to cater for this problem, SIWTP
requires a higher percentage of coagulant effectiveness, even though the difference between two coagulants is
only 1%, which is considered significant.
In addition, PAC outperforms Alum in terms of turbidity removal. The turbidity removal efficiency of the initial
dosage of both coagulants, PAC and Alum, was sufficient to meet sedimentation water limits of 3 to 7 NTU
provided by the responsible water supply operator, Ranhill SAJ Sdn. Bhd. Therefore, when comparing the two
coagulants, PAC with an optimum dosage of 23 mg/L is chosen as the best coagulant to be used in the water
treatment process (flocculation-coagulation) over Aluminium Sulphate with a dosage of 46 mg/L. This is
because a lower dosage of 23 mg/L PAC is required to achieve lesser turbidity and residual Aluminium of 1.26
NTU and 0.012, respectively. It can be concluded that the effectiveness of PAC to form a floc is faster and
better than Alum. In addition, the usage of Alum in water treatment plants may increase operating costs and not
be economic. This is because the coagulant of Alum must be supplied regularly due to the higher consumption.
Therefore, the PAC alternative coagulants will be highly competitive in the treatment of industrial water at low
dose levels.
Acknowledgements
The authors would like to extend our gratitude to the School of Civil Engineering of Universiti Teknologi
MARA and also Sultan Iskandar Water Treatment Plant for providing the necessary facilities for this research.
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