low pressure reverse osmosis membrane for...
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LOW PRESSURE REVERSE OSMOSIS MEMBRANE FOR REJECTION OF
HEAVY METALS
MYZAIRAH BINTI HAMDZAH
UNIVERSITI TEKNOLOGI MALAYSIA
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This thesis is dedicated to my beloved husband, Mohd Amri Yahaya, mama, Hafizah Jaaffar, abah,
Hamdzah Md Daly, atuk, Hj Jaaffar Hj Asri, nenek, Hjh Hasnah Tohirang, my brother, Mohd
Eezan, my sister, Mazeeha Hamdzah and particularly to my little princess, Kayra Humaira Mohd
Amri.
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ACKNOWLEDGEMENT
In the Name of God, the Most Merciful
In preparing this thesis, I was in contact with many people, researchers, and
academicians. They have contributed towards my understanding and thought. The first
and foremost, I wish to express my sincere appreciation to my main thesis supervisor,
Professor Dr. Zaini Ujang, for encouragement and guidance critics. I am also very
thankful to my co-supervisor Professor Dr. Hiroaki Ozaki for his guidance, advices and
motivation. Without their continued support and interest, this thesis would not have been
the same as presented here. I also thank Dr. Azmi Aris for his help in the experimental
design and statistical analysis.
I am also indebted to Ministry of Science, Technology and Innovation (MOSTI)
for financial support. Furthermore, this study would have been impossible without
technical support from Environmental Laboratory, Faculty of Civil Engineering,
ATAMA Tech., and Chemistry Laboratory, Faculty of Science, UTM, special thanks for
their assistance.
My sincere appreciation also extends to all my colleagues and others who have
provided assistance throughout my MSc work. Their views and tips are useful indeed.
Unfortunately, it is not possible to list all of them in this limited space. And finally, my
deepest gratitude, as always, to my husband, Mohd Amri Yahaya and all my family
members for their support and encouragement.
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ABSTRACT
Low Pressure Reverse Osmosis Membrane (LPROM) has been introduced to water and wastewater industries in the past few years due to the high cost of operational and maintenance of conventional high-pressure RO membrane system. LPROM may remove more than 90% of heavy metals depending on the operating conditions of the system. LPROM with operating pressure less than 100 psi is commercially available to make treatment system more affordable and cost effective. Therefore, the aim of this study was to produce high-quality drinking water using LPROM system by removing heavy metals and other contaminants. The main objective of this study was to evaluate the effectiveness of LPROM for rejection of heavy metals, under different operating parameters (i.e. pressure, feed concentrations and pH). A commercially available LPROM (ES20) system manufactured by Nitto Denko Company was used in this study. The experimental design was carried out using Response Surface Methodology (RSM). Two types of wastewater containing heavy metals (i.e. synthetic polluted water containing copper and magnesium from copper chloride and magnesium sulphate solutions, and raw water from ex- mining pool from Tasik Biru, Sarawak) were studied. The experimental study for copper showed that higher operating pressure increased permeate flux and higher feed concentration and pH values increased the percentage of removal. However, the two-way interaction parameter (i.e. pressure vs. pH, pressure vs. feed concentration and pH vs. feed concentration) showed insignificant effects in determining permeate flux and copper removal. For magnesium, all parameters and all two-way interaction were significant in determining the percentage of magnesium removal. The higher the operating pressure resulted in a higher permeate flux and percentage of magnesium removal. A higher the value of pH has caused a lower permeate flux. However, it will increase the percentage of magnesium removal. Besides, the higher the feed concentration of magnesium was also resulted the higher percentage of magnesium removal. The optimum range of operating pressure for both copper and magnesium removal was between 90 to 120 psi and at pH between 5.5 and 7.5. The optimum statistical model for these processes based on the experimental conditions of this study indicates that operating pressure was the most significant parameter in determining the permeate flux. However, the statistical analysis of heavy metals removal was statistically insignificant and showed that the range of parameters in the study appears to be less significant to develop a sensitive and comprehensive model. This was due to the transport or separation mechanism between micropollutants and membrane surface, effect of chemical characteristics as well as effect of metal complexation. As a conclusion, operating conditions such as operating pressure and pH must be taken into account when designing the LPROM system for an optimum process in order to achieve a better heavy metals removal with higher permeate flux.
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ABSTRAK
Sistem membran osmosis balikan bertekanan rendah telah diperkenalkan dalam proses olahan air dan airsisa industri berikutan daripada kos operasi dan penyelenggaraan yang tinggi oleh sistem konvensional osmosis balikan bertekanan tinggi. Sistem ini dapat menyingkirkan lebih dari 90% bahan cemar bersaiz mikro bergantung kepada keadaan operasi sistem. Kini, ia telah dikomersialkan dengan tekanan kurang daripada 100 psi bagi menjadikan sistem ini lebih berkemampuan dan kos efektif. Matlamat utama kajian ini adalah untuk menghasilkan air minum berkualiti tinggi menggunakan osmosis balikan bertekanan rendah di samping menyingkirkan bahan cemar bersaiz mikro. Objektif kajian ini adalah untuk menilai keberkesanan membran osmosis balikan bertekanan rendah dalam menyingkirkan bahan cemar bersaiz mikro bergantung kepada parameter operasi yang berbeza seperti tekanan, pH dan kepekatan larutan. Membran komersial (ES20) diperbuat oleh Nitto Denko Company digunakan dalam kajian ini. Rekabentuk ujikaji dilaksanakan dengan menggunakan Response Surface Methodology (RSM). Dua jenis airsisa telah diuji, iaitu airsisa sintetik daripada larutan kuprum klorida dan magnesium sulfat dan air mentah dari kawasan bekas perlombongan, Tasik Biru, Sarawak. Keputusan bagi larutan kuprum menunjukkan bahawa lebih tinggi tekanan yang digunakan dapat meningkatkan hasil fluks dan lebih tinggi kepekatan masukan larutan dan nilai pH, meningkatkan hasil penyingkiran. Walau bagaimanapun, interaksi parameter dua hala (tekanan lwn. pH, tekanan lwn. kepekatan larutan masukan dan pH lwn. kepekatan masukan larutan) tidak mempengaruhi dalam penentuan hasil fluks dan juga peratus penyingkiran kuprum. Untuk magnesium, semua parameter dan interaksi dua hala parameter mempengaruhi dalam menentukan peratus penyingkiran magnesium dan juga hasil fluks. Lebih tinggi tekanan yang digunakan, dapat meningkatkan hasil fluks dan juga peratus penyingkiran magnesium. Nilai pH yang tinggi menyebabkan hasil fluks berkurang. Walau bagaimanapun, ia akan meningkatkan peratus penyingkiran. Di samping itu, kepekatan masukan yang lebih tinggi juga akan menghasilkan peratus penyingkiran yang tinggi. Julat optimum untuk operasi tekanan bagi proses ini adalah antara 90 hingga 120 psi dan pada pH antara 5.5 dan 7.5. Model statistik yang optimum bagi proses ini menunjukkan bahawa tekanan adalah parameter penting dalam menentukan hasil fluks. Namun, analisis statistik untuk penyingkiran bahan cemar bersaiz mikro menunjukkan bahawa julat parameter dalam kajian ini tidak begitu mempengaruhi dalam membentuk model yang peka dan merangkumi proses. Ini berikutan daripada mekanisma pergerakan atau pemisahan antara bahan cemar bersaiz mikro dan permukaan membran, kesan daripada sifat kimia serta kesan daripada kompleksasi logam. Kesimpulannya, parameter operasi seperti tekanan dan pH adalah penting dalam merekabentuk sistem membran osmosis balikan bertekanan rendah bagi menghasilkan proses yang optimum dalam mencapai penyingkiran bahan cemar dan hasil fluks yang tinggi.
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TABLE OF CONTENTS
CHAPTER TITLE PAGE
1
TITLE PAGE
DECLARATION PAGE
DEDICATION PAGE
ACKNOWLEDGEMENT
ABSTRACT
ABSTRAK
TABLE OF CONTENTS
LIST OF TABLES
LIST OF FIGURES
LIST OF SYMBOLS AND ABBREVIATION
LIST OF APPENDICES
INTRODUCTION
1.1 Background of the Study
1.2 Objectives of the Study
1.3 Scope of the Study
1.4 Importance of the Study
1.5 Organization of the Thesis
i
ii
iii
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xi
xiv
xviii
xxii
1
1
4
5
6
7
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2 LITERATURE REVIEW
2.1 The Emergence of Membranes in Water and
Wastewater Applications
2.1.1 Regulatory Pressure
2.1.2 Water Scarcity
2.1.3 Market Forces
2.2 Principles of Membrane Processes
2.2.1 Reverse Osmosis Membrane
2.2.2 Low Pressure Reverse Osmosis
Membrane
2.3 Theory of Membrane Transport
2.3.1 Nonporous or Homogenous Membrane
Models
2.3.1.1 Solution-diffusion Model
2.3.1.2 Solution-diffusion Imperfection
Model
2.3.2 Pore-Based Model
2.3.2.1 Preferential Sorption Capillary
Flow Model
2.3.2.2 Surface Force-pore Flow Model
2.3.2.3 Finely Porous Model
2.3.3 Irreversible Thermodynamics Model
2.3.4 Recent Development
2.3.4.1 Donnan Equilibrium Model
2.3.4.2 Extended Nernst-Planck Model
2.3.4.3 Donnan-Steric Pore Model
2.4 Application of LPROM
2.4.1 Industrial Water and Wastewater
Application
2.4.2 Water Reclamation and Reuse
2.5 Micropollutants Removal
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36
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3
4
2.6 Metal Complexation - Membrane Processes
2.6.1 Complexation with H2O or OH-
2.6.2 Complexes with Other Ligands
METHODOLOGY
3.1 Experimental Set-up
3.1.1 Aromatic Polyamide LPROM
3.1.2 Test Cell
3.2 Experimental Procedures
3.2.1 Feed Solutions
3.2.2 Sampling
3.3 Preliminary Phase
3.3.1 Experimental Procedures
3.4 Analytical Procedures
3.5 Experimental Design
3.5.1 Stage 1 (Statistical design using
response surface methodology (RSM))
3.5.2 Stage 2 (One-variable-at-time-method)
3.5.3 Stage 3 (Response surface
methodology)
3.6 Data Analysis
RESULTS AND DISCUSSION
4.1 Introduction
4.2 Preliminary Stages
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5
4.2.1 Sodium Chloride
4.3 Stage 1
4.3.1 Copper (Cu)
4.3.1.1 Factorial Analysis
4.3.1.2 Response Surface Analysis
4.3.2 Magnesium (Mg)
4.3.2.1 Factorial Analysis
4.3.2.2 Response Surface Analysis
4.4 Stage 2
4.4.1 Permeate Flux
4.4.1.1 Feed Concentration
4.4.1.2 pH
4.4.1.3 Operating Pressure
4.5 Stage 3
4.5.1 LPROM for ex-mining pool water
treatment
4.5.2 LPROM for total arsenic removal from
ex-mining pool water
CONCLUSIONS AND RECOMMENDATIONS
5.1 Conclusions
5.2 Recommendations
REFERENCES
Appendix A-J
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85
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105
112
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114
116
130 - 166
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LIST OF TABLES
TABLE NO. TITLE PAGE
2.1
3.1
3.2
3.3
3.4
3.5
4.1
4.2
Selected research done on micropollutants removal by
LPROM
Specification of test cell unit
Composition of actual raw water collected from Tasik
Biru, Sarawak.
Selected parameters for system monitoring
Coding system for design of experiment of LPROM
process
Experimental runs conducted in LPROM for rejection
of micropollutants (not in random order), generated
from Minitab version 13.32
Experimental results of LPROM conducted for copper
chloride
ANOVA for permeate flux and percentage of copper
removal
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51
55
56
57
65
66
xii
4.3
4.4
4.5
4.6
4.7
4.8
4.9
4.10
4.11
4.12
4.13
Summary of p-value for the response surface modeling
analysis for flux
Summary of p-value for the response surface modeling
analysis for copper removal
Experimental results of LPROM conducted for
magnesium sulfate
ANOVA for permeate flux and percentage of
magnesium removal
Summary of p-value for the response surface modeling
analysis for flux
Summary of p-value for the response surface modeling
analysis for magnesium removal
Composition of raw water collected from Tasik Biru,
Sarawak
Characteristic of treated water using LPROM
Summary of p-value for the response surface modeling
analysis for flux
Summary of p-value for the response surface modeling
analysis for copper removal from raw water
Summary of p-value for the response surface modeling
analysis for magnesium removal from raw water
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78
79
85
88
96
97
99
100
100
xiii
4.14
4.15
Summary of p-value for the response surface modeling
analysis for permeate flux of arsenic removal from raw
water.
Summary of p-value for the response surface modeling
analysis for arsenic removal from actual raw water
106
108
xiv
LIST OF FIGURES
FIGURE NO. TITLE PAGE
2.1
3.1
3.2
3.3
3.4
3.5
3.6
3.7
4.1
Schematic representation of a two phase system
separated by a membrane
Schematic diagram of LPROM system
Photo of LPROM system
The flow of the experimental study
Schematic diagram of C10-T module
Schematic diagram inside of C10-T module (From
explanation note of C10T module by Nitto Denko Co.,
1998)
Photo of Tasik Biru, Sarawak.
Sampling Map
Permeate flux pattern of distilled water in LPROM
system
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51
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xv
4.2
4.3
4.4
4.5
4.6
4.7
4.8
4.9
4.10
Rejection pattern of sodium chloride (500 mg/L)
permeate flux in LPROM system at operating pressure
at 552 kPa and pH 7
Pareto chart for (a) permeate flux (b) percentage of
copper removal
Main effect plot for copper (a) permeate flux; (b)
percentage of removal
Comparison of permeate flux (m3/m2.h) by using
Solution-diffusion model and statistical model
Response surface representing relationship between
operating pressure (psi), feed concentration of Copper
(mg/L) and permeate flux
Contour plot representing relationship between
operating pressure (psi), feed concentration of Copper
(mg/L) and permeate flux
Response surface representing relationship between
pH, feed concentration of copper (mg/L) and
percentage of copper removal
Contour plot representing relationship between pH,
feed concentration of copper (mg/L) and percentage of
copper removal
Pareto chart for (a) permeate flux (b) percentage of
magnesium removal
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72
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80
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4.11
4.12
4.13
4.14
4.15
4.16
4.17
4.18
4.19
4.20
Main effect plot for (a) permeate flux; (b) percentage
of magnesium removal
Interaction effect plot of permeate flux
Interaction effect plot between operating pressure and
feed concentration for magnesium removal
Interaction effect plot between pH and feed
concentration for magnesium removal
Interaction effect plot between operating pressure and
pH for magnesium removal
Comparison of permeate flux (m3/m2.h) by using
Solution-diffusion model and statistical model.
Response surface representing relationship between
pH, feed concentration of magnesium (mg/L) and
percentage of magnesium removal
Contour plot representing relationship between pH,
feed concentration of magnesium (mg/L) and
percentage of magnesium removal
Comparison of experimental permeate flux with
statistical model calculation for copper and
magnesium depending on the change of feed
concentration
Comparison of experimental permeate flux for copper
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90
92
xvii
4.21
4.22
4.23
4.24
4.25
4.26
4.27
4.28
4.29
and magnesium with statistical model calculation for
copper depending on the change of pH
Comparison of experimental permeate flux for copper
and magnesium with statistical model calculation for
copper depending on the change of pressure
Comparison of permeate flux from statistical model of
synthetic solutions (CuCl2 and Mg2SO4) with raw
water from Tasik Biru, Sarawak
Effect of pressure and pH on copper removal from
CuCl2 feed solutions
Effect of pressure and pH on copper removal from
actual raw water
Effect of pressure and pH on magnesium removal
from Mg2SO4 feed solutions
Effect of pressure and pH on magnesium removal
from actual raw water
Effect of pressure and pH on permeate flux
Effect of pressure and pH on total arsenic removal
from actual raw water
Contour plot for the effect of pressure and pH on total
arsenic removal from actual raw water
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95
102
103
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104
105
107
109
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xviii
LIST OF SYMBOLS AND ABBREVIATION
- dimensionless potential fraction of force exerted on a solute
molecule by pore wall
p - applied pressure difference
- membrane thickness
sX - osmotic pressure corresponding to a mole fraction of solute Xs
- dimensionless radial position in pore
- dimensionless solvent velocity in pore
D - Donnan electrical potential (V)
- effective thickness of membrane
- fractional pore area of membrane
- osmotic pressure
- reflection coefficient of solute
b - ratio of solute radius to the membrane pore radius
C - concentration gradient
P - pressure gradient
T - temperature gradient
x - linear distance through the membrane
A - pure water permeability constant
ANOVA - Analysis of variance
APHA - American Public Health Association
As - Arsenic
AWWA - American Water Works Association
c - concentration
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C - molar concentration of salt
C - molar density of solution
CCRD - Central Composite Rotatable Design
Ci - concentration of the ith solute in bulk solution (mol/l)
ci - concentration of the ith solute inside membrane (mol/l)
cj(m) - concentration of ion j in the membrane
Cr3+ - Chromate
Cu - copper
CuCl2 - Copper chloride
cw - concentration of water in the membrane
DAB - solute diffusivity in the free solution
Dj(m) - diffusivity of ion j
Dsm - diffusivity coefficient in the membrane
Dsm - diffusion coefficient of salt in the membrane
DSPM - Donnan Steric Pore Model
Dw - diffusivity of water
DWSS - Department of Water Supply and Sewerage
E - Donnan potential
EQA - Environmental Quality Act
EU - European Union
F - faraday constant (9.6487 x 104C/mol)
F - Faraday’s constant
H2O - Water
HCl - Hydrogen chloride
HNO3 - Nitrate acid
Js - solute flux
Jw - water flux
Jv - refers to solvent volume flux.
K - solute distribution coefficient or partition coefficient
K - solute partition coefficient
Ki - refers to solute partition coefficient at location I
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km - mass transfer coefficient on the upstream side of the membrane
ks - distribution coefficient
l - membrane thickness
LPROM - Low pressure reverse osmosis membrane
m2 - meter square
m3 - meter cube
Mg - magnesium
Mg/L - milligram per liter
Mg2SO4 - Magnesium sulfate
NaCl - Natrium chloride
NaOH - Natrium hydroxide
OFAT - One-factor-at-time
OH- - Hydroxide
P - permeability coefficient of solute through membrane
Ps - solute permeability coefficient
PSCF - Preferential sorption-capillary flow
psi - pounds per square inch
R - gas constant
R - gas constant (8.31 J/mol K)
RO - reverse osmosis
RSD - Response surface design
RSM - response surface methodology
T - absolute temperature
TDS - Total dissolved solid
UP - Ultra-pure
USEPA - United States Environmental Protection Agency
Vw - partial molar volume of water
WHO - World Health Organization
WRF - World Research Foundation
XAB - friction between the solute and the solvent
XAM - friction between the solute and the membrane material
xxi
Xs2, Xs3 - mole fractions of solute in the high and low pressure side
j(m) - activity coefficient of ion j in the membrane
- frictional parameter
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LIST OF APPENDICES
APPENDIX TITLE PAGE
A
B
C
D
E1
E2
E3
F
G1
Data of permeate flux of NaCl collected every 30
minutes for a period of 240 minutes
Experimental runs conducted in LPROM for rejection
of micropollutants
Data of permeate flux and percentage of copper
removal (%) for 20 runs of experiment
Data of permeate flux and percentage of magnesium
removal (%) for 20 runs of experiment
Factorial design for copper removal
Interaction effect plot for copper removal
Response surface design for copper removal
Experimental determination of membrane permeability
Factorial design for magnesium removal
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131
132
134
136
138
141
145
146
xxiii
G2
G3
H
I1
I2
I3
J
Interaction effect plot for magnesium removal
Response surface design for magnesium removal
Comparison of the experimental, theory and statistical
model results
Experimental results of LPROM conducted for actual
raw water
Experimental results of LPROM conducted for actual
raw water (Arsenic)
Response surface design for micropollutants removal
from actual raw water
Paper cutting of Tasik Biru report
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158
159
160
166
CHAPTER I
INTRODUCTION
This chapter presents an overview of the micropollutants contamination in ex-
mining pools and previous studies conducted on membrane technology, especially using
Low Pressure Reverse Osmosis Membrane (LPROM) to remove micropollutants for
drinking water production. The objectives and background of the study are also stated in
this chapter. The scope of work are defined and the importance of this study are
presented. Lastly, this chapter also presents the structure of the thesis.
1.1 Background of the Study
Direct contamination of surface waters with micropollutants from mining,
smelting and industrial manufacturing is a long-standing phenomenon. In Malaysia,
water samples from ex-mining pools have been reported containing various
micropollutants, especially heavy metals (Yusof et al., 1996; Morgensen et al., 2001).
2
Heavy metals are conservative pollutants and some of them are harmful to
health. Some of these compounds may suppress the immune system, leading to
increased susceptibility to disease while some may be carcinogenic. For example, some
heavy metals such as copper, mercury and arsenic, for which the proposed guideline
values for drinking water quality are quite low (in the range of µg/L to a few mg/L)
owing to their carcinogenic effects or other risk factors to public health (Crespo et al.,
2004).
Generally, these types of micropollutants contained in polluted raw water can
cause problems in water treatment plants. They can inhibit the biological treatment
processes and reduce the treatment efficiency of the treatment plants (Buckley et al.,
2001). Thus, various technologies have been applied to remove micropollutants in water
and wastewater, such as coagulation, filtration, lime softening, activated carbon and
membrane technology. Although many of them have proved to be technically feasible,
other factors such as cost, operational requirements and aesthetic considerations have
not been favourable in some cases.
Membrane technology is considered as one of the most effective processes for
water and wastewater treatment. It is a compact system, economically feasible and has
high rejection level of pollutants (Oh et al., 2000). Membrane technology has been given
special focus in water treatment processes because of its capability in removing physical
and chemical matters at a higher-degree of purification. It is commonly divided into
microfiltration, ultrafiltration and reverse osmosis (RO), which utilizes pressure
differentials (Oh, 2001). Nowadays, RO is one of the effective technologies to remove
almost all pollutants, especially those with low concentrations. RO technology is also
used today in large water treatment plants. It produces good quality of potable water
from brackish and seawater resources, reclaim contaminated water sources and reduce
water salinity for industrial applications. In addition, the application spectrum of RO
membrane elements covers household units to produce higher quality of drinking water
(Wilf, 1998).
3
However, the use of RO system has been limited due to high operational cost to
keep the pressure at high level and maintain its components. RO requires high pressure
system and need extensive pre-treatment. Over the history of wastewater treatment and
reclamation by RO, developments in membrane technology have resulted in a variety of
advancements. These advancements included enhancements in salt rejection capabilities,
chemical stability and perhaps most importantly, pressure requirements (Filteau and
Moss, 1997). Hence, in the past few years, low pressure reverse osmosis membrane
(LPROM) has been introduced to water and wastewater industries (Ujang and Anderson,
2000; Filteau and Moss, 1997; Hofman et al., 1997; Ozaki et al., 2001).
LPROM is not a new concept in membrane technology. Its inception could be
traced back to the 1960s (Ujang and Anderson, 2000). At that time, LPROM system was
not an attractive system because of low flux and non-reliable membrane materials. For
the past 15 years, many improvements were made to the membrane and different models
were introduced into the market. One of the goals of many studies carried out recently
was to reduce the operating costs of RO, by lowering the required operating pressure of
the system. In the mid-1990s, membrane manufacturers began marketing high-rejection-
high-flux LPROM (Nemeth, 1998). Recently, LPROM with operating pressure less than
100 psi is available commercially to make the system more affordable and cost effective.
Most studies carried out so far on LPROM have been focused on bench-scale
feasibility approach using various pollutants. The applications of LPROM for
micropollutants removal, particularly the investigation of operating parameters effect
(i.e. pressure, feed pH and feed concentration) on separation of metal chelates, study on
transport phenomena based on electrostatic, steric hindrance and filtration effect of
LPROM as well as the effect of metal complexation, have not been studied extensively
up to date.
4
1.2 Objectives of the Study
The aim of this study was to produce high-quality drinking water, using LPROM
system to remove micropollutants from feed water. This can be achieved by the
following specific objectives:-
i. To evaluate the effectiveness of LPROM for rejection of micropollutants,
using synthetic wastewater, i.e. magnesium and copper under different
operating parameters, such as pressure, feed concentrations and pH.
ii. To analyze and optimize the pressure range and other associated
operating parameters for rejection of micropollutants using response
surface methodology.
iii. To investigate the feasibility of micropollutant removal from an actual
ex-mining pool water, Tasik Biru, Sarawak and to study the effect of
metal complexation.
iv. To develop a statistical model for the removal efficiency using LPROM.
5
1.3 Scope of the Study
This study focused on the performance of LPROM, which was evaluated by
response parameters, i.e. permeate flux and the percentage of micropollutant removal.
This study was conducted on an experimental rig and the analytical studies include
physical and chemical procedures, particularly to evaluate the performance and
effectiveness of LPROM system.
The experimental design was carried out using response surface methodology
(RSM). RSM is a statistical and mathematical technique which is useful for developing,
improving and optimizing processes. All experiments were investigated under different
operating parameters, i.e. pressure, pH and feed concentration.
Two types of wastewater containing micropollutants were studied i.e. synthetic
polluted water containing micropollutants i.e. copper (Cu) and magnesium (Mg) from
copper chloride and magnesium sulphate solutions, and raw water from an ex-tin mining
pool from Tasik Biru, Sarawak.
6
1.4 Importance of the Study
Various technologies have been applied to remove pollutants in raw water, such
as ion exchange, activated carbon and membrane separation (Oh et al., 2000). Due to
high costs of operation and maintenance of conventional high-pressure RO membrane
system, LPROM has been introduced to the water and wastewater industries in the past
few years (Ujang and Anderson, 1996; Filteau and Moss, 1997; Hofman et al., 1997;
Ozaki et al., 2001). The importance of this study are as follows:-
i. Water and wastewater treatment using LPROM can remove more than
90% of micropollutants depending on the operating parameters of the
system. In order to achieve the optimum value of removal and flux
rate, this study will be useful to determine the best operating
conditions for LPROM system.
ii. This study will provide insight on the transport phenomenon of solutes
through the LPROM charged membrane, which can affect the overall
performance of LPROM systems.
iii. This study will provide a statistical model which acts as the basic
reference in identifying the effectiveness of LPROM system in treating
water and wastewater.
7
1.5 The Organization of the Thesis
This thesis consists of five chapters. Chapter I gives an overview of
micropollutants contamination in ex-mining pools and studies conducted on membrane
technology, especially LPROM. An overview of the theoretical background of studies
conducted on membrane technology, especially LPROM, and theory of membrane
transport are presented in Chapter II. Chapter III presents the methodology used in this
study including on the design of experiments. Factorial design analysis and response
surface methods (RSM) were described in this chapter.
Chapter IV presents the results of the experimental studies that have been
described in Chapter III. Findings are combined and discussed holistically in this
chapter. The last chapter, Chapter V, stated the conclusions of this study.
Recommendations for future studies are also outlined in this chapter.