low pressure reverse osmosis membrane for...

LOW PRESSURE REVERSE OSMOSIS MEMBRANE FOR REJECTION OF

HEAVY METALS

MYZAIRAH BINTI HAMDZAH

UNIVERSITI TEKNOLOGI MALAYSIA

iii

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.

iv

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.

v

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.

vi

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

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ii

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iv

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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

8

8

9

10

11

12

13

14

16

17

17

19

20

20

22

23

25

27

28

30

31

32

34

36

36

ix

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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41

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47

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52

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61

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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

91

91

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94

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96

105

112

112

114

116

130 - 166

xi

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

40

48

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


analysis for copper removal

Experimental results of LPROM conducted for

magnesium sulfate

ANOVA for permeate flux and percentage of

magnesium removal


analysis for flux


analysis for magnesium removal

Composition of raw water collected from Tasik Biru,

Sarawak

Characteristic of treated water using LPROM


analysis for flux


analysis for copper removal from raw water


analysis for magnesium removal from raw water

69

75

78

79

85

88

96

97

99

100

100

xiii

4.14

4.15


analysis for permeate flux of arsenic removal from raw

water.


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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46

49

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51

52

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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


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

63

67

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72

73

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76

77

80

xvi

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.


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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87

90

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


Contour plot for the effect of pressure and pH on total

arsenic removal from actual raw water

93

95

102

103

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104

105

107

109

110

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

xix

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

xx

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

xxii

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

130

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


Paper cutting of Tasik Biru report

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154

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.

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