Membrane Based Triethylene Glycol Separation and Recovery...

i

Membrane Based Triethylene Glycol Separation and Recovery

from Gas Separation Plant Wastewater

by

Pimchanok Khachonbun

A thesis submitted in partial fulfillment of the requirements for the

degree of Master of Engineering in

Environment Engineering and Management

Examination Committee: Prof. Chettiyappan Visvanathan (Chairperson)

Prof. Ajit P. Annachhatre

Dr. Romchat Rattanaoudom (External Expert)

Nationality: Thai

Previous Degree: Bachelor of Engineering in Environmental

Engineering

Suranaree University of Technology, Thailand

Scholarship Donor: Royal Thai Government – AIT Fellowship

Asian Institute of Technology

School of Environment, Resources and Development

Thailand

May 2013

ii

Acknowledgements

I would like to express my heartfelt thanks and profound gratitude to my advisor, Prof. C.

Visvanathan, who has supported me throughout my thesis with his excellent guidance,

encouragement and valuable suggestions. Without his supervision and constructive

assistance, this study would not have been in its present shape.

Special appreciation is also extended to Prof. Ajit P. Annachhatre and Dr. R.

Rattanaoudom as the thesis committee members, who provided valuable comments,

support, suggestions and assistances toward the usefulness of the study.

I would like to gratefully acknowledge to Royal Thai Government (RTG) for scholarships

for the Master study in AIT. Moreover, my deep gratitude goes to Petroleum Authority of

Thailand (PTT), for providing technical support for my research.

I am thankful to Prof. C. Visvanathan’s research group for their support. Especially my

thanks go to Mr. P. Jacob and Mr. T. Rathnayake for their technical support and

encouragement to complete the research successfully.

In addition, my deep great gratitude also is extended to all my dear teachers, faculty

members and all staffs and technicians of EEM for their help, technical and moral support

and cooperation, which assisted me to complete this thesis.

I would like to express my deep thanks to my colleagues, Ms. Phontida, Mr. Supawat, Mr.

Phanwatt, Mr. Kiattisak, Mr. Duc, Mr. Ahmad, Mr. Siripong, Mr. Lalith, Ms. Kamala and

Ms. Tasawan for their generous support in technically as well as humanly during the entire

period of my study.

Finally, my achievement would never be possible unless there is hearty support from my

family. The deepest and sincere gratitude goes to my beloved parents, my younger sister

for their endless love, encouragement and understanding throughout the entire period of

my study.

iii

Abstract

Triethylene glycol (TEG) is absorption, involves the use of a liquid desiccant to remove

water content from the gas. This study investigated membrane filtration, pervaporation

process and design pre-treatment process to treat real wastewater from gas separation

plants. In membrane filtration experiment, four types of membrane (NF-TS40, NF-TS80,

RO-ACM5 and RO-NTR759HR) were tested with synthetic wastewater. NF-TS80 is the

best of nanofiltration membrane to recover TEG, with a 70% TEG recovery. Moreover,

RO-ACM5 was the most effective membrane of reverses osmosis membrane, with a 90%

TEG recovery which presented at low concentration applied (0.1%, 5% and 10% of TEG).

In case of permeate flux, the low permeate flux (0.01-0.16 L/m2.h) presented at high

concentration applied (20% and 30% of TEG) that was resulted from the effect of

concentration polarization and membrane fouling.

Pervaporation process was conducted with 0.1, 5 and 10% of TEG concentrations in

synthetic wastewater with temperature variation of 30, 40 and 70°C of each concentration.

In case of permeate flux, the high permeate flux 6.81 kg/m2.h presented at low

concentration (0.1% of TEG) and used high temperature (70°C). While the permeate flux

at a concentration of 10% was found with 0.58 kg/m2.h at 40°C. Also, the separation factor

was 698 for 10% TEG at 40°C. The flux and the separation factors obtained indicate that

pervaporation process with NaA Zeolite membrane is not attractive and the system does

not performed well at lower concentration of solutes.

In pre-treatment experiment, testing with real wastewater using RO-ACM5 and NF-TS80

membranes was necessary. However, the wastewater first needs be pretreated to protect

membrane from fouling by suspended solids and oil/grease by used microfiltration (MF)

and ultrafiltration (UF) membrane, respectively. Pre-treatment process coupled with

nanofiltration membrane (TS80) showed higher TEG removal than synthetic wastewater

experiments at 0.1% TEG concentration by approximately 73%. While reverse osmosis

membrane (ACM5) showed slightly higher removal for TEG than synthetic wastewater

experiments with 0.5% TEG concentration also by approximately 95%. In case of 8.3%

TEG concentration, nanofiltration (TS80) and reverse osmosis (ACM5) membrane showed

relatively equal to the value of synthetic wastewater experiments by approximately 47.15%

and 77.56%, respectively. Therefore, the pre-treatment process should be applied before

using membrane filtration with NF and RO membrane which are proposed for industrial

applications due to its high removal efficiency, high permeate flux with low TEG

concentrations.

iv

Table of Contents

Chapter Title Page

Title Page

Acknowledgements

Abstract

i

ii

iii

Table of Contents iv

List of Tables vi

List of Figures vii

List of Abbreviations viii

1 Introduction 1

1.1 Background of the Study

1.2 Objectives of the study

1.3 Scope of the Study

1

2

3

2 Literature Review 4

2.1 Triethylene Glycol Characteristics

2.1.1 General properties

2.1.2 Uses of TEG (Triethylene glycol)

2.1.3 Distribution in environment

2.1.4 Toxic effects

2.2 Gas Separation Plants (GSPs)

2.2.1 Characteristics of TEG in wastewater from gas

separation plant

2.3 Treatment Process

4

4

5

5

6

9

9

11

3

2.4 Membrane Filtration

2.4.1 Membrane applications

2.4.2 Introduction to membrane process

2.4.3 Type of filtration

2.4.4 Operational parameters

2.4.5 Factors affecting membrane filtration

2.4.6 Potential membrane filtration (NF/RO)

2.4.7 Pervaporation technology

Methodology

12

12

13

15

16

17

18

19

27

4

3.1 Phase I: High Pressure Membrane Filtration

3.1.1 Materials

3.1.2 Membrane tests unit

3.2 Phase II: Membrane of Pervaporation

3.2.1 Materials


3.3 Phase III: Design Pre-Treatment Process to Treat

TEG wastewater

3.3.1 Materials

3.4 Indicative Methods for TEG

3.4.1 TEG analysis by gas chromatograph (GC)

Results and Discussions

28

28

28

31

31

32

34

34

35

35

38

v

5


4.1.1 Membrane properties

4.1.2 Permeate flux

4.1.3 Rejection

4.2 Phase II: Pervaporation Process

4.2.1 Permeate flux

4.2.2 Separation factor

4.2.3 Rejection

4.3 Phase III: Design Pre-Treatment Process for Treat

TEG Wastewater


4.3.2 Efficiency of TEG wastewater before and after

pre-treatment process

4.3.3 Permeate flux of TEG in real wastewater

4.3.4 Rejection of TEG in real wastewater

4.3.5 Real wastewater characteristics after

NF and RO membrane treatment

Conclusions and Recommendations

5.1 Conclusions

5.2 Recommendations for Further Study

References

Appendix A

Appendix B

Appendix C

Appendix D

Appendix E

Appendix F

38

38

39

42

43

43

44

45

46

46

47

49

51

54

56

56

57

60

63

66

70

72

75

77

vi

List of Table

Table Title Page

2.1 Physical and Chemical Properties of Triethylene Glycol 4

2.2 The Number of Facilities of Glycols was Used and The Number of

Employees Exposed

6

2.3

2.4

2.5

2.6

2.7

2.8

2.9

2.10

2.11

2.12

2.13

2.14

2.15

2.16

2.17

3.1

3.2

3.3

3.4

3.5

4.1

4.2

4.3

4.4

4.5

4.6

Surface Water Quality Guidelines for DEG and TEG

The Primary Method of Prevention and Medical Care of Human

The Composition of Natural Gas

Total Production Capacity of PTT’s Gas Separation Plant

Sources of TEG Wastewater Treatment Plant

Discharged Effluent Characteristics of Gas Separation Plants

Detail Explanation of Different Membrane Processes

Comparison of Rejection Efficiency of Constituents between NF

and RO

Summary of Pervaporation

Overview of Chosen Membrane Separation Processes

Types of Membrane for Pervaporation

Comparison of Pervaporation Modules

Selective and Transport Properties of Different Types of

Pervaporation Membranes

Permeate Flux and Separation Factor of Ethanol/Water Mixture

Comparison of Advantages and Disadvantages of Pervaporation

List of NF Membranes and Its Properties

List of RO Membranes and Its Properties

List of Pervaporation Membranes and Its Properties

List of MF Membranes and Its Properties

List of UF Membranes and Its Properties

Membrane Characteristics

Wastewater Characteristics of Real Wastewater from Gas

Separation Plants

Wastewater Characteristics of Real Wastewater After MF

Membranes Pre-treatment

Wastewater Characteristics of Real Wastewater After UF


Wastewater Characteristics of Real Wastewater After NF


Wastewater Characteristics of Real Wastewater After RO


6

8

9

10

11

12

16

19

20

21

22

24

25

26

26

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54

54

vii

List of Figure

Figure Title Page

2.1 Structures of Triethylene Glycol (TEG) 4

2.2 Major uses of TEG 5

2.3

2.4

2.5

2.6

2.7

2.8

2.9

2.10

2.11

3.1

3.2

3.3

3.4

3.5

4.1

Source of TEG wastewater in Gas Separation Plant of PTT

(Thailand)

Wastewater treatment plants

Demonstrates main characteristics of each membrane types

Membrane fouling

Schematic drawing of the pervaporation process with a downstream

vacuum or an inert carrier-gas

Hollow fiber modules

Plate-and-frame modules

Spiral wound module

Tubular modules

Experimental plans of study

Flow diagram of membrane experimental set up

Flowchart of membrane filtration experiment

Flowchart of pervaporation membrane experiment

Flow diagram of pervaporation experimental set up

Permeate fluxes of membrane filtrations

10

12

15

17

19

23

24

24

24

27

29

30

32

33

40

4.2

4.3

4.4

4.5

4.6

4.7

4.8

4.9

4.10

Normalized flux of direct filtration at different compound

concentrations

Membrane Fouling

Removal efficiency of synthetic wastewater thought membrane

filtration

Permeate fluxes of pervaporation process

Separation factor of pervaporation process

Removal efficiency of synthetic wastewater thought pervaporation

process

Design pre-treatment processes to treat TEG wastewater

Permeate fluxes of membrane filtrations with real TEG wastewater

Removal efficiency of real 0.5 and 8.3% of TEG wastewater

41

42

42

44

44

45

48

51

53

viii

List of Abbreviations

bw Brood War

CAS Chemical Abstracts Service

Da Dalton

DEG Diethylene glycol

EG Ethylene glycol

ESP Ethane Separation Plant

GC Gas Chromatography

GSPs Gas Separation Plants

KD Kilodalton

kPa Kilopascal

LD Lethal Dose

LD50 Median Lethal Dose

MBR Membrane bioreactor

MF Microfiltration

MMSCFD Million Standard Cubic Feet per Day

MSDS Material Safety Data Sheet

NF Nanofiltration

nm Nanometer

PC Personnel computer

ppm Parts per Million

PTT Petroleum Authority of Thailand

PV Pervaporation

R Compound Rejection

RO Reverse Osmosis

TEG Triethylene glycol

TREG Tetraethylene glycol

UF Ultrafiltration

U.S.EPA United States Environmental Protection Agency

wt Net Weight

μm Micrometer

1

Chapter 1

Introduction

1.1 Background of the Study

One of the best glycol frequently used in dehydration of natural gas is TEG (Triethylene

glycol). TEG is a colorless, odorless and viscous liquid with molecular formula C6H14O4.

Advantages of using TEG are ease of regeneration and operation, minimal losses of drying

agent during operation, high affinity for water, chemical stability, high hygroscopicity and

low vapor pressure at the contact temperature.

In term of toxicity and bioaccumulation, TEG is listed as slightly toxic in acute rating from

U.S.EPA. (2003) and low bioconcentration and biomagnification. For human, when

considering exposure route of TEG on experiment conditions and works with this material

by inhalation, ingestion, skin and eyes contact, it has been identified as hazardous and for

potential acute and chronic health effects. Robertson et al. (1947) exposed rats to TEG in

their drinking water at 3,000 mg/kg bw/day for 13 months. No effects on mortality, body

weight, blood and urine composition, and gross and microscopic appearance of the major

organs was reported. Furthermore, Bossert et al. (1992) exposed mice to drinking water

containing TEG for 14 weeks. No effects were seen at 3,300 mg/kg bw/day, but increased

liver weight was observed at 6,800 mg/kg bw/day.

Apart from environmental contamination, their harmful effects on animal and human have

also been revealed in many studies. Regarding to animal studies, the effect on rats exposed

to the test material via a whole-body inhalation protocol and also receiving the chemical

via the oral and dermal routes appears to be low, with reported oral LD50 has value 17,000

mg/kg (MSDS, 2010). Moreover, this study has been repeated using a nose-only exposure

for 6 hours a day for 9 consecutive days. In this inhalation toxicity study, mean exposure

concentrations of 102, 517, or 1,036 mg/m3 (approximately 0.1, 0.5, 1.0 mg/L/day)

triethylene glycol produced no treatment-related toxicities at any dose tested (McRae,

1998).

In the present, natural gas is one of the most important fuels in our life and one of the

principle sources of energy for day-to-day needs and activities. It is an important factor for

the development of countries that have strong economy because it is a source of energy for

household, industrial and commercial use, as well as to generate electricity. Most natural

gas producers use TEG to remove water in the dehydration process. When TEG is placed

into contact with natural gas it strips the water out of the gas. Thus, TEG is one of the

major components of the wastewater originates from a Gas Separation Plants (GSPs).

Therefore it is absolutely essential to recover and reuse TEG, back in the production

process and more reduces wastewater volume in GSPs.

Nowadays, membrane technologies are becoming more frequently used for separation of

wide varying mixtures in the petrochemical related industries and can complete

successfully with traditional. Membrane technology is widely used in wastewater treatment

processes recently, due to its high performance. Microfiltration (MF), ultrafiltration (UF),

nanofiltration (NF) and reverse osmosis (RO) are successfully used to produce high quality

water. Orecki et al. (2006) found that almost use membrane filtration for separation of EG

(ethylene glycol) from wastewater by nanofiltration. These studies were conducted using

2

the two membrane module configurations-spiral wound (equipped with membranes:

NF270-2540) and NF90-2540) and tubular (equipped with membranes AFC 30) for

separation of EG.

Wastewater in petrochemical industry is currently treated by activated sludge process with

pretreatment of oil/water separation (Ravanchi et al., 2009). Tightening effluent

regulations and increasing need for reuse of treated water have generated interest in the

treatment of petrochemical wastewater with the advanced membrane bio-reactor (MBR)

process.

Pervaporation (PV) is a membrane process used to separate liquid mixtures. In the

dehydration application, water is removed from its mixtures with organic components by

selective permeation through a dense hydrophilic membrane. The most relevant application

of PV is the separation of liquid azeotropes and close boiling point solvent-water mixtures.

Nik et al. (2005) found that inorganic membranes and particular zeolite membranes are

usually used for the dehydration of organic solvent by pervaporation (PV). In this study on

the pervaporation dehydration of EG/water mixtures using commercial nanoporous NaA

zeolite membranes.

A non-porous membrane separates the liquid feed from a downstream compartment to

which vacuum is applied. On the feed side, water is preferentially absorbed on the

membrane. On the permeate side, the water molecules are desorbed and removed, due to

the application of vacuum. The sorption of water on the hydrophilic membrane creates a

water concentration gradient, resulting in a diffusive flux across the membrane. Owing to

the vacuum applied at the permeate side of the membrane, permeate is in the vapors state,

so a phase change occurs from liquid on the feed side to vapor on the permeate side.

Therefore, when looking at membranes to enhance performance, there is often a trade-off

between separation factor and total flux.

1.2 Objectives of the Study

This study aims to develop alternative treatment method for separation and recovery of

concentrated TEG from wastewater in Gas Separation Plants before they are discharged.

The specific objectives of this study are:

1) To investigate efficiency of nanofiltration, reverse osmosis and pervaporation

for TEG separation and recovery;

2) To develop pre-treatment processes to treat real wastewater generated from

dehydration unit in Gas Separation Plant Wastewater (GSPs).

1.3 Scope of the Study

To accomplish the above objectives, scope of study was set as follows:

1) The study was comprised of 3 phases, and their scopes are:

Phase I: High pressure membrane filtration study was conducted in bench-

scale with various membrane types (NF/RO) and varying compound

concentration.

3

Phase II: membrane of pervaporation study was conducted in bench-scale

with various membrane types and varying compound concentration.

Phase III: Design the pre-treatment process to organics and inorganics

compound separation in real wastewater from GSPs before pass through

membrane filtration (NF/RO) process.

2) The wastewater applied in this study of phase I and II was synthesized from

MiliQ® water, TEG used in Gas Separation Plants (GSPs).

3) The wastewater applied in this study of phase III was real wastewater generated

from dehydration unit in Gas Separation Plant Wastewater (GSPs).

4

Chapter 2

Literature Review

2.1 Triethylene Glycol Characteristics

Triethylene Glycol (also known as TEG, triglycol and trigen) is employed as a liquid

desiccant for the dehydration of natural gas. Molecular structures of glycols are mono-, di-

and triethylene glycols which are the first three members of a homologous series of

dihydroxyalcohols. The three glycols have many similar chemical properties. Differences

in their applications are due mainly to variations in physical properties such as viscosity,

hygroscopicity and boiling point.

Figure 2.1 Structures of Triethylene Glycol (TEG)

2.1.1 General properties

Physical form of TEG is a colorless, odorless and stable liquid with high viscosity and a

high boiling point. It is also soluble in ethanol, acetone, acetic acid, glycerin, pyridine and

aldehydes; slightly soluble in diethyl ether; and insoluble in oil, fat and hydrocarbons. The

physical and chemical properties of triethylene glycol are shown in Table 2.1.

Table 2.1 Physical and Chemical Properties of Triethylene glycol (TEG)

Parameter Unit Properties

Common name - Triethylene Glycol

Chemical name - Triethylene Glycol

CAS registry number - 112-27-6

Empirical formula - C6H14O4

Molecular weight g/mol 150.17

Density g/cm3 1.10

Flash point (PMCC) °C (°F) 176 (350)

Ignition point, °C (˚F) °C (°F) 371 (700)

Distillation range at 760 mm Hg

Initial boiling point

Dry point

°C (°F)

278 (532)

300 (572)

Boiling point at 760 mm Hg °C (°F) 287.8 (550)

Freezing point °C (°F) -7.2 (19)

Coefficient of expansion per °C at 20°C - 0.00068

Surface tension at 20°C dyne/cm 45.2

Vapor pressure at 20°C mm Hg less than 0.01

Specific Gravity - 1.1274

Solubility - Highly miscible in water

Source: Material Safety Data Sheet (2012)

5

2.1.2 Uses of TEG (Triethylene glycol)

The main uses for triethylene glycol are based upon its hygroscopic quality. TEG used as

a dehydrating agent for natural gas pipelines where it removes the water from the gas

before being condensed and reused in the system. Moreover, TEG also has a

dehumidifying agent in air-conditioning units. TEGs used to make chemical intermediates

such as plasticizers and polyester resins. In addition, TEG is used in many products

including automotive antifreeze, brake fluids and industrial solvents (Leth and Gregersen,

2005), and TEG is also used as a solvent in many applications, including as a selective

solvent for aromatics, and a solvent in textile dyeing. Triethylene glycol also has mild

disinfectant qualities and, when volatized, is used as an air disinfectant for virus and

bacteria control.

Figure 2.2 Major uses of TEG (Alberta Environment, 2012)

However, the usage of TEG as adsorbent in gas dehydration may affect human, animal and

contaminate in the environment. TEG may transport into soil, release into the river, and

accumulate in sediment at the bottom of the river by rapid run off during the rainy season

and finally affect aquatic and human health.

2.1.3 Distribution in environment

No information was found that would indicate DEG (diethylene glycol), TEG, or TREG

(tetraethylene glycol) occur naturally in the environment. Accordingly, their distribution in

the environment is expected to be strongly biased towards facilities where these

compounds are produced or used. The number of facilities where the Glycols are used is

significant. In the U.S., national surveys of occupational hazards were carried out in 1974

and 1983. The 1983 survey indicated that the number of facilities where these glycols was

used and the number of employees exposed to each was:

Natural Gas

Dehydration,

45

Vinyl

Pkasticizer, 13

Solvent, 11

Manufacture of

Ester

Derivatives, 12

Miscellaneous,

19

6

Table 2.2 The Number of Facilities of Glycols was Used and The Number of

Employees Exposed

Glycol Number of Facilities Number of Employees Exposed

DEG 55,518 890,145

TEG 23,174 233,613

TREG 3,704 55,282

Source: Alberta Environment (2012)

The physical and chemical properties of these glycols (Table2.1) control the environmental

media in which they are likely to be found. All three glycols have very low vapor

pressures, and accordingly, their presence in the atmosphere will not be significant. All the

Glycols could potentially be present in soil, groundwater, and/or surface water (Table 2.3)

in the vicinity of facilities where they are used.

Glycol releases from oil and gas facilities can occur as a result of leaks from operating

equipment or through the improper disposal of wastes when glycol-using facilities are

maintained.

Spills and releases of DEG, TEG, and TREG at gas plants are remediated where possible.

In Alberta, frequency of spill reporting and concentrations of DEG are generally higher

than TEG and TREG, with TREG typically having concentrations less than 10 mg/kg or

non-detectable concentrations.

Table 2.3 Surface Water Quality Guidelines for DEG and TEG

Water Use DEG (mg/L) TEG (mg/L)

Human drinking water

(Source Guidance value for groundwater) 6 60

Freshwater aquatic life 150 350

Irrigation 1 n/c n/c

Livestock watering 2 n/c n/c

Wildlife watering 3 n/c n/c

Source: Alberta Environment (2010)

Notes: n/c = not calculated

1. Guideline protective of irrigation not calculated due to lack of toxicity data relevant to

irrigation.

2. Guideline not calculated due to the lack of toxicity information for livestock species.

3. Guideline not calculated due to the lack of toxicity information for wildlife species.

2.1.4 Toxic effects

TEG has been hazards Identification both of potential Acute Health Effects and Potential

Chronic Health Effects in human and animals are limited information from animal studies

reveals a range of acute toxic effects overlapping those for DEG (Alberta Environment,

2010). Smyth et al. (1941) found that rats and guinea pigs fed TEG at doses approaching

the LD50 appeared sluggish (possibly indicating depression of the central nervous system)

and gross examination revealed kidney damage. Oral LD50 values for laboratory animals

range from 8,800 to 22,000 mg/kg. Ocular and dermal studies found TEG to be non-irritant

7

or mildly irritating. Moreover, for chronic toxic Fitzhugh and Nelson (1946) exposed male

rats to 4% TEG in their diet (approximately 2,000 mg/kg bw/day) for 2 years. No effects

on mortality, body weight, blood and urine composition, and gross and microscopic

appearance of the major organs was reported.

In human are very hazardous in case of eye contact (irritant) of ingestion and slightly

hazardous in case of inhalation. Inflammation of the eye is characterized by redness,

watering, and itching, which there primary method of prevention and medical care is

showed in table 2.4. TEG has a very low order of acute toxicity by perioral, percutaneous

and inhalation (vapor and aerosol) routes of exposure. It does not produce primary skin

irritation. Acute eye contact with the liquid causes mild local transient irritation

(conjunctiva hyperemia and slight chemosis) but does not induce corneal injury. Robertson

et al (1947) exposed rats to TEG in their drinking water at 3,000 mg/kg bw/day for 13

months. No effects on mortality, body weight, blood and urine composition, and gross and

microscopic appearance of the major organs was reported. Bossert et al (1992) exposed

mice to drinking water containing TEG for 14 weeks. No effects were seen at 3,300 mg/kg

bw/day, but increased liver weight was observed at 6,800 mg/kg bw/day.

Animal maximization and human volunteer repeated insult patch tests studies have shown

that TEG does not cause skin sensitization (Ballantyne et al., 2007). The use patterns

suggest that exposure to TEG is mainly occupational, with limited exposures by

consumers. Exposure is normally by skin and eye contact. Local and systemic adverse

health effects by cutaneous exposure are likely not to occur, and eye contact will produce

transient irritation without corneal injury. The very low vapor pressure of TEG makes it

unlikely that significant vapor exposure will occur. Aerosol exposure is not a usual

exposure mode, and acute aerosol exposures are unlikely to be harmful, although a

peripheral sensory irritant effect may develop.

However, repeated exposures to a TEG aerosol may result in respiratory tract irritation,

with cough, shortness of breath and tightness of the chest. Recommended protective and

precautionary measures include protective gloves, goggles or safety glasses and

mechanical room ventilation. LC50 data to various fish, aquatic invertebrates and algae,

indicate that TEG is essentially nontoxic to aquatic organisms. Also, sustained exposure

studies have demonstrated that TEG is of a low order of chronic aquatic toxicity. The

bioconcentration potential, environmental hydrolysis and photolysis rates are low, and soil

mobility high. In the atmosphere TEG is degraded by reacting with photochemically

produced hydroxyl radicals. These considerations indicate that the potential for

ecotoxicological effects with TEG is low Carcinogenicity and Mutagenicity (Ballantyne et

al., 2007).

8

Table 2.4 The Primary Method of Prevention and Medical Care of Human

Identification of hazards Prevention

1. Potential Acute Health Effects:

Eye contact (irritant)

Inhalation (Slightly hazardous)

Skin contact

Ingestion

Check for and remove any contact lenses.

Immediately flush eyes with running water

for at least 15 minutes, keeping eyelids

open.

Cold water may be used.

Do not use an eye ointment.

Seek medical attention.

Allow the victim to rest in a well-ventilated

area.

Seek immediate medical attention

No known effect on skin contact, rinse with

water for a few minutes.

Do not induce vomiting.

Loosen tight clothing such as a collar, tie,

belt or waistband.

If the victim is not breathing, perform

mouth-to-mouth resuscitation.

Seek immediate medical attention.

2. Potential Chronic Health Effects:

Carcinogenic effects

Mutagenic effects

Affecting organs inside the body.

Not available

Not available

The substance is toxic to kidneys, the

nervous system.

Repeated or prolonged exposure to the

substance can produce target organs

damage.

Source: Material Safety Data Sheet (2012)

9

2.2 Gas Separation Plants (GSPs)

2.2.1 Characteristics of TEG in wastewater from gas separation plant

In the present, natural gas is one of the most important fuels in our life and one of the

principle sources of energy for many of our day-to-day needs and activities. It is an

important factor for the development of countries that have strong economy because it is a

source of energy for household, industrial and commercial use, as well as to generate

electricity. Most natural gas producers use TEG to remove water in the dehydration

process. When TEG is placed into contact with natural gas it strips the water out of the gas.

Thus, TEG is one of the major components of the wastewater originates from a Gas

Separation Plants (GSPs).

Moreover, the raw natural gas contains water vapor, hydrogen sulfide (H2S), carbon

dioxide, helium, nitrogen, and other compounds showed in table 2.5. In order to meet the

requirements for a clean, dry, wholly gaseous fuel suitable for transmission through

pipelines and distribution for burning by end users, the gas must go through several stages

of processing, including the removal of entrained liquids from the gas, followed by drying

to reduce water content.

Table 2.5 The Composition of Natural Gas

Components Symbol Percentage (%)

Methane CH4 70-90

Ethane C2H6

0-20 Propane C3H8

Butane C4H8

Carbon Dioxide CO2 0-8

Oxygen O2 0-0.2

Nitrogen N2 0-05

Hydrogen Sulphide H2S 0-5

Rare Gases He,Ne,Xe trace

Source: Composition of natural gas (2012)

In addition, the types of dehydration process used are absorption, adsorption, gas

permeation and refrigeration. The most widely dehydration processes used are which

usually involves one of two processes: either absorption, or adsorption. Absorption occurs

when the water vapor is taken out by a dehydrating agent. Adsorption occurs when the

water vapor is condensed and collected on the surface.

In part of TEG, The TEG adsorbs water from the wet gas and is passed to the glycol

regeneration unit where, very simply, adsorbed gases are flashed off and the water is

removed from the reboiler by heating the wet glycol to around 400ºF at atmospheric

conditions gas. The processes are continuous, that is glycol flow continuously through

dehydration unit where they come in contact and the glycol absorbs the water. The

regenerated TEG is then pumped back to the dehydration unit inlet. Thus, TEG is one of

the major components of the wastewater originates from a Gas Separation Plants (GSPs).

Therefore it is absolutely essential to recover and reuse TEG, back in the production

process.

10

Furthermore, in this study is case of PTT (Petroleum Authority of Thailand) which is the

largest operator of gas separation plants in Thailand. PTT’s gas separation plant unit 1 was

started operating on 1985, with unit 2 to 5 coming up later on. In addition, unit 1, 2, 3 and

5 are located in Rayong province and have production capacity of 390, 290, 390 and 530

MMSCFD (Million standard cubic feet per day respectively). Unit 4 is located in Kanhom,

Nakhon Srithammarat provinces and has current production capacity of 170.

PTT is having another two projects on construction in Rayong. The two new plants are the

ethane separation plant (ESP) and the gas separation plant unit 6. The ethane separation

plant’s purpose is to improve production of the gas separation plant unit 2 and 3. The gas

separation plant unit 6 has the production capacity of 800 MMSCFD. Both projects

encourage development of petrochemical industry and production of liquefied natural

(Cooking Gas) in response of the domestic demand. The total production capacity of

PTT’s gas separation plant will increase to 2,640 MMSCFD, which showed in table 2.6.

Table 2.6 Total Production Capacity of PTT’s Gas Separation Plant

Source: PTT Research & Technology Institute (2012)

Note: MMSCFD = Million standard cubic feet per day

Gas separation plants are located in Rayong of Thailand; there are 2 sources of TEG

wastewater as follow in table 2.7 and figure 2.3.

Figure 2.3 Source of TEG wastewater in GSPs of PTT (Thailand)

GSP Unit 1-5 ESP and GSPs Total

Gas separation Capacity

(MMSCFD) 1,770 870 2,640

Production Capacity (Million Tons per Year)

Ethane 1.1 1.3 2.4

Propane & LPG 2.5 1.1 2.6

NGL 0.5 0.2 0.7

Total 4.1 2.6 6.7

11

Table 2.7 Sources of TEG Wastewater Treatment Plant

Wastewater treatment plant Detail

Wastewater 1: (TEG low concentrations) - Volume 10-12 m3/day with concentration

of TEG 0.4%

- Half is send to the wastewater treatment

plant in industry which treatment with

AOP (Advanced Oxidation process)

system; another half is send external

disposal.

Wastewater 2: (TEG high concentrations) - Volume 1 m3/day with concentration of

TEG 5-70%

- Send to Better world green company for

disposal (2,700 bath/tons)


2.3 Treatment Process

TEG wastewater in PTT of Thailand uses conventional wastewater treatments. Moreover,

consisting process physical Treatment, minimizing Complex Structure of Organic

Compounds, biological treatment and MBR (Membrane Bio reaction) system, which have

effluent Characteristics are show in table 2.8.

Orecki et al., 2006 found that almost use membrane filtration for separation of EG

(ethylene glycol) from wastewater by nanofiltration. These studies was to use the two

membrane module configurations-spiral wound (equipped with membranes: NF270-2540)

and NF90-2540) and tubular (equipped with membranes AFC 30) for separation of EG.

Nik et al., 2005 found that inorganic membranes and particular zeolite membranes are

usually used for the dehydration of organic solvent by pervaporation (PV). In this study on

the pervaporation dehydration of EG/water mixtures using commercial nanoporous NaA

zeolite membranes.

Jehle et al., 1995 develop the evaporation (EV), for the concentration of the coolant liquid

from 25% up to 70% glycol. The ethylene glycol concentration in the overhead product

remains as low as 0.5% for this concentration range. Using two different pressures 13.3

and 133.3 mbar at 75°C. The tests of pervaporation (PV) were carried out with a mixture of

the original coolant liquid diluted with water at ethylene glycol concentrations in the range

of 70-95% at 75°C and using different pressure 20-30 mbar. The tests of reverse osmosis

(RO) were detailed with pressure between 15 and 70 bar and temperature between 15 and

40 °C which has the initial glycol feed concentration 0.5%-5%. Furthermore, reverse

osmosis and pervaporation to separation of glycol and water from coolant liquids which

have the pre-treatment process by gravity separation to free oil and settleable solids before

pass through membrane filtration.

12

Table 2.8 Discharged Effluent Characteristics of Gas Separation Plants

Parameter Unit Effluent Standard

pH - 7.9 5.5-9.0

TEG % < 2 ppm

(at influent of ozone tank) -

TDS mg/L 1254 3000

TSS mg/L 2.9 50

BOD mg/L 4 20

COD mg/L 42 120

Oil & Grease mg/L 0.5 5

Cl mg/L 417 -

TKN mg/L 2.7 100

Hg mg/L 0.0001 0.005

Zn µg/L 0.58 5

Total Coli form MPN 100 mL 220 <1,000


Figure 2.4 Wastewater treatment plants (PTT Research &

Technology Institute, 2012)

2.4 Membrane filtration

2.4.1 Membrane applications

Improvements and advances in membrane technology over the last four decades have seen

their applications expand into many industrial sectors, such as chemical, petrochemical,

13

mineral, pharmaceutical, electronics, beverages, beer/wine clarification, as well as

wastewater purification and water desalination. Membrane separation processes compete

with conventional processes such as carbon adsorption, solvent extraction, distillation,

centrifugation, flocculation followed by multimedia filtration, and ion-exchange.

Compared to conventional separation, membrane processes offers several advantages, such

as high quality products, the requirement for less chemical addition, and easier control of

operation and maintenance. However, membrane fouling is still hampering the growth of

industrial applications of membranes (Richard, 2012).

2.4.2 Introduction to membrane process

Membrane is receiving special recognition as alternatives to conventional water treatment

and as a means of polishing treated wastewater effluent especially in reuse applications. It

is defined as a thin film separation of two or more components from fluid flow and can be

classified differently on the basis of determined criteria like type of materials, fluid

movement, morphology, pore size etc. The need for more efficient treatment processes has

attracted the attention of environmental scientists and engineers towards pressure-driven

membrane techniques. The application of membrane filtration processes not only enables

high removal efficiencies, but also allows reuse of water and some of the valuable waste

constituents. In the last few years, technical and economic improvement has made the

treatment of industrial wastewater by membrane system even more advantageous.

Ultrafiltration has been successfully applied for recycling high molecular weight and

insoluble dyes, auxiliary chemicals and water. However, ultrafiltration does not remove

low molecular weight and soluble dyes (acid, direct, reactive and basic, etc.) but efficient

color removal has been achieved by nanofiltration. Its apparent benefits over other

advanced treatments are including continuous separation, low energy consumption, easy

combination with other existing technique, easy up-scaling, and no chemical cost.

Excepting water/wastewater treatment, membrane process can be found in all industrial

areas such as food and beverages, metallurgy, pulp and paper, textiles, pharmaceutical,

automotive, dairy, biotechnology and chemical industry. Membrane is widely used in

industrial process and used for chemical recovery.

As mentioned above, membrane can be manufactured by a wide variety of materials

included inorganic and organic membrane. The inorganic membranes may be distinguished

to 4 types such as ceramic, glass, metallic and zeolite membranes. Their advantages are

high chemical, mechanical and thermal stabilities but the disadvantages are very fragile

and expensive. The organic membranes are widely used in water and wastewater

applications they are more flexible and can be put in compact module. It can be made from

cellulose and synthetic polymer. The synthetic polymer can be manufactured for open

porous membranes, which are applied for microfiltration and ultrafiltration and dense

nonporous membrane, applied in gas separation and pervaporation. The summarized

details of each are explained as following.

Microfiltration (MF)

It is most similar to conventional coarse filtration, the pore size range from 100 - 1000 nm

and driving force pressure is less than 4 bars. It is mainly used to separate suspended and

colloidal particles by size sieving mechanism. It is applied for various purposes in industry

such as analytical application, sterilization in food and pharmaceuticals, ultrapure water

production in semiconductors, clarification, algae cell harvesting, water treatment and

14

membrane bioreactor in wastewater treatment. MF membranes are made from a number of

organic and inorganic materials, for example:

- Polymeric membranes: polyamide (PA), polysulphone (PS), polyethersulphone

(PES), polypropylene (PP), polycarbonate (PC).

- Ceramic membranes: alumina (Al2O3), zirconia.

MF is used primarily for separating macromolecules, large suspended particles, fungi and

bacteria. It is finding increased application as a pretreatment method to other membrane

processes, in pharmaceutical applications (Meltzer and Blakie, 1987) as a replacement for

conventional clarification and filtration technologies (Noble and Stern, 1995).

Ultrafiltration (UF)

The pore size is from 10–100 nm. Ultrafiltration (UF) is a variety of membrane filtration in

which hydrostatic pressure forces a liquid against a semipermeable membrane. Suspended

solids and solutes of high molecular weight are retained, while water and low molecular

weight solutes pass through the membrane. This separation process is used in industry and

research for purifying and concentrating macromolecular (103 -10

6 Da) solutions,

especially protein solutions. Ultrafiltration is not fundamentally different from

microfiltration and nanofiltration except in terms of size of molecules it retains. The

applications beyond microfiltration are including metallurgy (oil-water emulsion, electro

paint recovery), textile, etc.

UF has been accepted as an alternative to conventional pretreatment for brackish surface

water and sea water reverse osmosis (SWRO) systems (De et al., 2002). The use of UF

systems as RO pretreatment has some significant advantages over RO systems designed to

include conventional pretreatment:

- UF membrane systems take up less than 50% of the area of a conventional

pretreatment system, which results in reduced construction costs. This means that

a UF membrane system may be more favorable in cases where space is limited, or

where the costs of civil works are high.

- UF membranes system is easier to operate than some conventional filtration

processes.

- The operating costs of a UF membrane system may be lower than those for

conventional pretreatment systems.

- UF concentrated waste streams are easier to dispose of relative to those from

chemically enhanced conventional pretreatment processes.

- UF filtrate quality is usually better than that of conventional pretreatment process.

The colloidal fouling load to the RO is reduced, with a significantly lower Silt

Density Index (SDI) and turbidity in the feed water.

Nanofiltration (NF)

It is used for removal of low molecular weight solutes such as inorganic salts or small

organic molecules. Its pore size is in range of 1–10 nm and the operating pressure is 3-20

bars. The applications are including desalination of brackish water, removal of micro

pollutants, water softening, wastewater treatment, rejection of dyes, etc

15

Reverse osmosis (RO)

The pore size is almost similar with nanofiltration but percentages of salt rejection are

different. The driving pressure is in range of 10-100 bars. The applications are including

desalination of brackish and seawater, production of ultrapure water for electronic

industry, concentration of food juice, sugar and milk, etc.

Figure 2.5 Demonstrates main characteristics of each membrane types

2.4.3 Types of filtration

Typically, membrane filtration can be classified to 2 types including cross flow and dead-

end filtrations depending on application and module configuration. The prior provides

lower fouling rate and smaller flux decline than the later. Because of the cross-flow

operation can minimize fouling and cake layer formation on membrane with adjustment of

cross-flow velocity of feed. In case of dead-end filtration, even though it causes large

membrane fouling, its strength is high water recovery relative to cross flow type.

NF and RO are mostly applied with cross flow type because they tend to have fouling as

compared to other bigger pore of membranes. In case of MF, dead-end filtration is

frequently applied whereas both of cross flow and dead-end operations are applied in UF.

Microfiltration

100 – 1000 nm

Ultrafiltration

10 – 100 nm

Nanofiltration

1 – 10 nm

Reverse Osmosis

< 10 nm

ΔP = 0.1-4 bar ΔP = 0.2-10 bar ΔP = 3-20 bar ΔP = 10-100 bar

Colloids, Virus

Color Hardness Pesticides

Salt

Water

Color

Hardness

Pesticides

Salt

Water

Salt

Water Water

16

Table 2.9 Detail Explanation of Different Membrane Processes

Pressure driven membrane processes

Microfiltration Ultrafiltration Nanofiltration Reverse Osmosis Piezodialysis

Membrane

symmetric

porous

Asymmetric

porous

Composite

Asymmetric or

composite

Mosaic

membranes

Thickness ≈ 10-150 µm ≈ 150µm

Sub layer ≈ 150

µm

Top layer <1

µm

Sub layer ≈ 150

µm

Top layer <1 µm

≈ a few

hundred µm

Pore size ≈ 0.05-10 µm ≈1-100 µm ≈2nm ≈2nm Nonporous

Separation

principle

Sieving

mechanism

Sieving

mechanism

Sieving and

electrostatic

repulsion

Steric and

electrostatic

repulsion

Ion transport

Membrane

material

Polymeric,

ceramic

Polymer,

ceramic polyamide

Cellulose

triacetate,

aromatic

polyamide,

polyamide and

poly

(ether urea)

Cation/anion

-exchange

membrane

Source: Ravanchi et al., (2009)

2.4.4 Operational parameters

The transmembrane pressure (∆P) is the driving force behind the filtration process. The

equation below is to predict permeate flux that remains proportional to hydraulic resistance

for porous membrane system. The flux is volume of liquid passing through a unit area of

membrane per unit time. It can be determined by measurement of permeate volume or

calculation of both the driving force and resistances. Under the simplest operating

conditions, the resistance to flow is offered entirely by membrane.

. t

PJ

R

Equation.2.1

Where J = permeate flux (L/m2.h)

∆P = transmembrane pressure (kPa)

μ = viscosity of permeate (Pa.s)

= (479 × 10-3

)/(Temp: ˚C + 42.5)1.5

Rt = total resistance (1/m) ; Rt = Rm + Rc + Rf

Rm = intrinsic membrane resistance

Rc = cake resistance on membrane surface

Rf = fouling resistance caused by solute adsorption in to membrane pore

and irreversible fouling.

The description of different resistance types are demonstrated in figure 2.6

17

Clean Membrane Fouled Membrane

Figure 2.6 Membrane fouling

The selectivity of membrane toward diluted mixture is generally expressed by percentage

of rejection (R), demonstrated as follows;

% 1 100p

f

CR

C

Equation.2.2

Where Cp = solute concentration in permeate

Cf = solute concentration in feed

2.4.5 Factors affecting membrane filtration

2.4.5.1 Hydrophobicity/hydrophilicity of membrane

Hydrophobicity/hydrophilicity of membrane is described for its ability to allow water

passing through. It is investigated by measurement of contact angle of water droplet on

membrane surface. Greater than 90˚ of contact angel indicates that the membrane has low

affinity to water (hydrophobicity) leading to low permeate flux as compared to hydrophilic

one. Moreover, hydrophobicity of membrane also affects removal of organic compound.

2.4.5.2 pH

pH of solution relates to presenting charge of membrane and a compound beside it

involves proton dissociation of functional group, attached on membrane surface or

composed in compounds. Thus, it directly affects electrostatic forces between compound

and membrane surface. Zeta potential is defined as power of charges showing on

membrane surface. The negatively charged membrane has been reported to highly reject

negatively charged organic compound through electrostatic repulsion (Bellona et al.,

2004). However, the electrostatic repulsion was reported to decrease with feed containing

some contaminants such as salts (Na+, Mg

2+, etc.). It resulted because the positive ions

18

dissolved in solution might adsorb negative charge on membrane leading to decreasing

membrane rejection through electrostatic repulsion.

However, low rejection of negatively charged compound has also been observed with

negatively charged membrane. McCallum et al. (2008) demonstrated decreasing rejection

of estrogen processing negative charges by predominantly negative-charged polyamide

membrane.

2.4.5.3 Organic matter

From literature review, the presence of organic matter showed different effects on

membrane filtration as follows;

1. Decreasing rejection

A number of researches demonstrated adverse effect of organic matter on membrane

filtration of some organic pollutants. Yoon et al. (2006) found that natural organic matter

decreased rejection of nanofiltration. They explained that it might be resulted from

competition between natural organic matter and pollutants on sorption site of membrane.

Their explanation is similar with a number of researches that organic matter caused

pollutants (McCallum et al., 2008 and Zhang et al., 2006).

2. Increasing rejection

Comerton et al. (2008) found that rejection of pollutants prepared in filtered lake sample

was higher than in Milli-Q water with tight NF membrane. They concluded that in addition

to membrane pore size, water matrices play important role on rejection by improving

configuration or properties of membrane surface. Moreover, it is interesting to find that

feed prepared with secondary effluent from MBR showed significant membrane fouling

than natural water, even though it provided lower rejection (Comerton et al., 2008). Hence,

chemical properties of water matrices relates to fouling characteristics and membrane

rejection.

2.4.6 Potential membrane filtration (Nanofiltration and Reverse osmosis)

2.4.6.1 Reverse Osmosis/Nanofiltration (RO/NF)

There are only few researches that applied membranes (RO and NF) for TEG recovery in

wastewater. Due to in efficiency of conventional treatment systems, nanofiltration (NF)

frequently becomes the chosen treatment process. NF has been recognized having the

properties in between UF and reverse osmosis (RO) and thus offers significant advantages,

e.g. lower osmotic pressure difference, higher permeate flux, higher retention of

multivalent salt and molecular weight compounds (>300), relatively low investment and

low operation and maintenance costs. Koyuncu et al., 2004 utilized NF membrane to reuse

reactive dyehouse wastewater and the rejection of NaCl was about 12% while the 99.9% of

dye in the solution was removed. Comerton et al., 2008, Lee et al., 2008, Yoon et al., 2007,

Nghiem and Hawkes, 2007, Plakas et al., 2006 and Berg et al., 1997. These researches

investigated efficiency of reverse osmosis and nanofiltration on several kinds of those

compounds. In overviews, reverse osmosis showed greater than 90% of removal efficiency

whereas nanofiltration showed lower efficiencies.

19

Table 2.10 Comparison of Rejection Efficiency of Constituents Between NF and RO

Constitutes Unit NF RO

Total dissolved solids % 40-60 90-98

Total organic carbon % 90-98 90-98

Color % 90-96 90-96

Hardness % 80-85 90-98

Salts/chloride % 10-50 90-99

Salts/sulphate % 80-95 90-99

Nitrate % 10-30 84-96

Heavy Metalsa % 40->50 85-95

Protein log 3-5 4-7

Pathogens (ex:bacteria) log 3-6 4-7

EDCs/PhACs % >10 >90

a = except Cd, Ag and Hg

Source: Asano et al.(2007), Lee at al.(2008) and Comerton, et al.(2008)

2.4.7 Pervaporation technology

2.4.7.1 Definition of pervaporation process

Pervaporation is a membrane process in which a pure liquid or mixture is in contact with

the membrane on the feed or upstream side at atmospheric pressure and where permeate is

removed as a vapor because of a low vapor pressure existing on permeate or downstream

side. This low (partial) vapor pressure can be achieved by employing a carrier gas or using

a vacuum pump. The (partial) downstream pressure must be lower than the saturation

pressure at least. A schematic drawing of this process is show in figure 2.7

Figure 2.7 Schematic drawing of the pervaporation process with a downstream

vacuum or an inert carrier-gas

Essentially, the pervaporation process involves a sequence of the three steps:

Selective sorption into the membrane on feed side

Selective diffusion through the membrane

Desorption into a vapor phase on the permeate side

Vacuum pump

Condenser

Feed Retentate

Permeate

Carrier gas

Condenser

Permeate

Retentate Feed

20

The driving force for the mass transfer of permeates from the feed side to the permeate side

of the membrane is a gradient in chemical potential, which is established by applying a

difference in partial pressures of permeates across the membrane. The difference in partial

pressures can be created either by reducing the total pressure on the permeate side of the

membrane by using a vacuum pump system or by sweeping an inert gas on the permeate

side of the membrane.

Table 2.11 Summary of Pervaporation

Membranes:

Composite membranes with an elastomeric or glassy

polymeric top layer

Thickness: ≈ 0.1 to few μm (for top layer)

Pore size: Nonporous

Driving force: Partial vapors pressure or activity difference

Separation principle: Solution/Diffusion

Membrane material: Elastomeric and glassy polymer

Application: Dehydration of organic solvents

Removal of organic components from water

(alcohols, aromatics, chlorinated hydrocarbons)

Polar/Non-polar (e.g. alcohols/aliphatic or

alcohols/aromatics)

Saturated/Unsaturated (e.g. cyclohexane/

benzene)

Separation of isomers (e.g. C-8 isomers;

o-xylene, m-xylene, p-xylene, ethyl benzene, styrene)

Source: Reidel et al. (1996)

2.4.7.2 Definition of vapor permeation

Vapor permeation is similar in principle to pervaporation. The only difference concerns the

feed, which is a mixture of vapors or vapors and gases. As in pervaporation, the permeate

partial pressure is maintained by use of a vacuum or an inert sweep gas (table 2.11). There

is no change of phase involved in its operation. Thus, compared to pervaporation, the

addition of heat equivalent to the enthalpy of vaporization is not required in the membrane

unit and there is no temperature drop along the membrane (Kujawski, 2000). Operation in

the vapor phase also eliminates the effect of the concentration polarization prevalent in

liquid phase separations, such as pervaporation

21

Table 2.12 Overview of Chosen Membrane Separation Processes (Kujawski, 2000)

Membrane

process

Feed

phase/permeate

phase

Driving force Membrane Main

Applications

Pervaporation liquid/vapor

Chemical

potential

gradient

Dense,

Hydrophobic

Separation of

liquid mixtures

Vapor

permeation vapor/vapor

Chemical

potential

gradient

Dense,

Hydrophobic

Separation of

vapor mixtures or

vapor from gases

Pertraction liquid/liquid Concentration

gradient

Dense,

Hydrophobic

Separation of

organic solutions

Gas separation gas/gas

Hydrostatic

pressure

gradient

Porous or

Dense

Separation of

gaseous mixtures

Membrane

distillation liquid/vapor

Vapor pressure

gradient

Porous or

Dense

Ultrapure water,

concentration of

solution

Thus, in table 2.12 presents the main characteristics of chosen membrane processes which

resemble pervaporation or vapor permeation concerning either the membranes applied or

type of application. To avoid any misunderstandings it is quite important to know both the

differences and similarities of these processes. The performance of a given membrane in

pervaporation or vapor permeation is estimated in terms of its selectivity and the permeate

flux. The assessment is based on the mass transfer of the preferentially permeating species,

regardless of whether permeate or the retentate is the target product of the pervaporation

process (Kujawski, 2000).

2.4.7.3 Operational parameters

The selectivity of a given membrane can be estimated by using the following two

dimensionless parameters. The equation 2.3 is used to determine separation factor and

equation 2.1 for determine permeate flux as follows:

Separation Factor ()

/

/

/

water org permeate

water org

water org feed

C C

C C Equation 2.3

Where Corg = Denote the weight fraction of organic, gram (kg)

Cwater = Denote the weight fraction of water component, gram (kg)

22

2.4.7.4 Variables that affect the performance of pervaporation.

Feed concentration

Due to the concentration of the preferentially permeating (usually minor) solution

component, being depleted in the process. There are two aspects to be considered the

activity of the target component in the feed and the solubility of the target component in

the membrane.

Membrane thickness

Refers to dry thickness because flux is inversely proportional to membrane thickness, thin

a membrane favors the overall flux but decrease selectivity. Moreover, thin membranes are

used for low swelling glassy membranes and thick membranes are used for high swelling

elastomeric membranes to maintain the selectivity.

Permeate pressure

Permeate pressure provides the driving force in pervaporation which the permeation rate of

any feed component increases as its partial permeate pressure is lowered. The highest

conceivable permeate pressure is the vapor pressure of the penetrant in the liquid feed.

Moreover, the effect of this parameter on pervaporation performance is dictated by the

magnitude of the vapor pressures encountered, and by the difference in vapor pressures

between them.

Temperature

Feed temperature or any other representative between feed and retentate streams. The feed

liquid provided the heat of vaporization of permeate, and in consequence there is a

temperature loss between the feed and retentate stream where the membrane act as a heat

exchanger barrier. Furthermore, temperature affects solubility and diffusivity of all

permeates, as well as the extent of mutual interaction between them. Favoring the flux and

having minor effect on selectivity.

2.4.7.5 Type of membranes and membrane modules

The choice of the membrane strongly depends on the type of application. It is important

which of the component should be separated from the mixture and whether this component

is water or an organic liquid.

Table 2.13 Types of Membrane for Pervaporation (Reidel et al., 1996)

Hydrophilic Hydrophobic

Polyacrylonitrile (PAN) Polydimethylsiloxane (PDMS)

Polyvinyl alcohol (PVA) Polyoctylmethylsiloxane (POMS)

Polyacrylic acid (PAA) Polyether block amide (PEBA)

Chitosan (CS)

23

Hollow fiber module

This module is used with an inside–out configuration to avoid increase in permeate

pressure within the fibers, but the outside–in configuration can be used with short fibers.

Another advantage of the inside-out configuration is that the thin top layer is better

protected but higher membrane area can be achieved with the outside-in configuration.

Figure 2.8 Hollow fiber modules (Xu, 2001)

Plate and Frame module

Two adjacent membrane pairs and then the feed solution flows through the membrane

between each pair of modules are composed of a double membrane or a sequence of

stacked layers horizontally. Moreover, the other devices to determine which making the

flow of retentate and permeated.

Figure 2.9 Plate-and-frame modules

Spiral wound module

This module is very similar to the plate and frame system but has a greater packing

density. This type of module is used with organophilic membranes to achieved organic–

organic separations.

24

Figure 2.10 Spiral wound module (Xu, 2001)

Tubular modules

Inorganic (ceramic) membranes are produced mainly as tubes, and then the obvious

module is the tube bundle for applications that used this kind of membranes. On the other

hand, for sweep gas pervaporation, tubular membranes conducting the gas-permeate

mixture are the only option.

Figure 2.11 Tubular modules (Xu, 2001)

The difference and similarity between different pervaporation modules are summarized in

table 2.13

Table 2.14 Comparison of Pervaporation Modules (Xu, 2001)

Hollow

Fine

Fibers

Capillary

Fibers

Spiral-

Wound

Plate-and-

Frame Tubular

Manufacturing Cost

,($/m2

) 5-20 20-100 30-100 100-300 50-200

Packing Density High Moderate Moderate Low Low

Resistance to fouling Very poor Good Moderate Good Very good

Parasitic pressure

drops High Moderate Moderate Moderate Low

Suitable for high

pressure operation Yes No No Yes

Can be done

with

difficulty

Limited to specific

types of membrane Yes Yes No No No

25

2.4.7.6 Applications

Generally, the component with the smallest weight fraction in the mixture should

preferentially be transported across the membrane as follows the table 2.14.

Table 2.15 Selective and Transport Properties of Different Types of Pervaporation

Membranes (Kujawski, 2000).

Membrane

material

Binary

mixture A/B

Content of A

component in

feed (%wt)

Temperature

(˚C)

Selectivity

A,B

Permeate

Flux

(kg m-2

h-1

)

Hydrophilic polymeric membranes

Polyvinyl

alcohol

Polyamide-6

Polyamide-6

Polyamide-

6/PAA

PESS Li+

PESS K+

Water/Ethanol

Water/Ethanol

Water/Dioxide

Water/Acetic

acid

Water/Isoprop

anol

Water/Isoprop

anol

0.1-8

30

50

8.7

11

11

90-100

80

35

15

25

25

50-2000

2

45

82

40

60

0-2

1-1.5

0.04

0.005

0.087

0.026

Hydrophobic polymeric membranes

Polypropylene

Silicone

Rubber

Silicone

Rubber

PDMS

PDMS

PEBAX

Acetone/Water

Isopropanol/W

ater

Butanol/Water

Butyl

acetate/Water

MTBE/Water

Aniline/Water

45

9-100

0.8

0.7

2

5.5

116

25

30

50

50

80

3

9-22

45-65

370

280

198

0.1-1.2

0.03-0.11

<0.035

0.55

1.2

1.8

Membrane made of conducting polymers

Polypyrole

Polypyrole

Methanol/Tolu

ene

Methanol/Isopr

opanol

5

10

58

58

590

2

0.240

0.004

Inorganic membranes

Zeolite NaA

Zeolite NaY

PERVATECH

PERVATECH

Ethanol/Water

Methanol/MT

BE

Water/Acetic

acid

Water/Isoprop

anol

5

10

5

1

95

50

75

100

5100

7600

150

250

3.35

0.32

2.5

4.0

For a given mixture a large variety in membrane performance can be observed with various

polymers. Table 2.15 gives the selectivity and fluxes of various homogenous membranes

for ethanol-water mixtures. It is seen that both the selectivity and flux can range from

extremely high to very low.

26

Table 2.16 Permeate Flux and Separation Factor of Ethanol/Water Mixture through

Different Homogeneous Membranes. Feed: 90 wt. % Ethanol.

Temperature: 70ºC. Membrane Thickness: = 50 μm (Kujawski, 2000)

Polymer Permeate Flux (kg/m2.h) Separation Factor

Polyacrylonitrile 0.03 12500

Polyacrylamide 0.42 2200

Polyvinylalcohol 0.38 140

Polyethersulfone 0.72 52

Polyhydrazide 1.65 19

Table 2.17 Comparison of Advantages and Disadvantages of Pervaporation (Xu, 2001)

Advantages Disadvantages

Low energy consumption

Low investment cost

Better selectivity without thermodynamic

limitations

Clean and close operation

No process wastes

Compact and scalable units

Scarce membrane market

Lack of information

Low permeate flows

Better selectivity without

thermodynamic limitations

Limited applications:

Organic substances dehydration

Recovery of volatile compounds at

low concentrations

Separation of azeotropic mixtures

However, pervaporation must be regarded as a young membrane process compared to

other membrane processes like reverse osmosis, ultrafiltration, dialysis and even electro

dialysis. There are several practical advantages of pervaporation and vapor permeation

when compared with other conventional technologies: simple operation and control,

reliable performance, high flexibility, unproblematic part-load operation, high product

purity (no contamination by entrained), no environmental pollution, high product yield,

low energy consumption, compact design (low space requirements), short erection time

and uncomplicated capacity enlargement. In general, pervaporation and vapor permeation

will especially be used in those cases where a small quantity has to be removed from a

large quantity. In all the above applications, the most successful processes require

integration with existing conventional separation unit operations. Nevertheless,

pervaporation and vapor permeation have been identified as areas of vast potential for

future research and commercial development.

27

Chapter 3

Methodology

This study comprised of two main phases namely: (1) High pressure membrane filtration

(2) membrane of pervaporation and (3) Design a pre-treatment process to treat wastewater.

Figure 3.1 demonstrates overall experimental study.

Phase I Phase II

Phase III

Figure 3.1 Experimental plan of study

The detail experiment of each phase is presented in the subsequent sections

- Use synthetic TEG wastewater - Use real TEG wastewater from GSPs

High Pressure Membrane Filtration

Preliminary test: 4 Types of Membranes

Comparison of NF and RO membrane

treatment efficiency

Determination of Optimum Concentration

of TEG (Triethylene Glycol)

- Use synthetic TEG wastewater

Membrane of Pervaporation

Preliminary test: 1 Type of Membrane

Comparison of pervaporation membrane

treatment efficiency

Determination of Optimum Concentration

of TEG (Triethylene Glycol)

Criteria of wastewater characteristics for pre-treatment

selection:

- Pre-Treatment is applied for organics and inorganics

removal from real wastewater before entering NF and

RO membrane

Design a Pre-Treatment Process to treat TEG

wastewater

28


3.1.1 Materials

The characteristics of NF and RO membrane were reported in Table 3.1 and 3.2

Table 3.1 List of NF Membranes and Its Properties, (Qin et al., 2007 and Halle, 2009)

Note: LMH = (L/m2h)

Table 3.2 List of RO Membranes and Its Properties

Source: Jeżowska et al.(2006), Song and Kim (2000)

Note: LMH = (L/m2h)


5 liters of TEG (Triethylene Glycol) solution was poured inside double wall stainless steel

feed tank, in which 25±1°C of temperature was controlled using cooling tank. A Hydracell

piston pump (Model G-20, Wanner Engineering, INC., Minneapolis, MN), connected with

inverter (VS mini J7 Series, Yaskawa Electric Cooperation, Japan) for flow rate

adjustment, would deliver TEG solution from feed tank to membrane filtration unit at

approximately 2 L/min of flow rate. The stainless steel membrane unit has 32 cm2 of

effective surface area. Pressure gauges were installed at feed and concentrate sides to

determine pressure. Moreover, membrane system was operated in recycle mode that

concentrate is sent back to feed tank. Permeate flux was measured by an electronic

balance.

Properties TS-40 TS-80

Manufacturer TriSep TriSep

Salt rejection (%NaCl and %MgSO4) 40-60 and 99 80-90 and 97.0

MWCO (DA) 200 150

ZETA potential at pH 7 (mV) -14±3 -14±3

Hydrophobic, Hydrophilic Hydrophilic Hydrophilic

Contact angle (˚) 48±2 48±2

Pure water flux (LMH/bar) 4.48 7.84

Polymer Polypiperazine amide Polyamide

pH range at 25˚C 2-11 2-11

Typical Flux/psi (GFD@PSI) 20/110 20/110

Properties NTR-759 HR ACM5

Pure water flux (LMH/bar) 1.7 5.75

Salt rejection (%NaCl 1.5 kg/m3) 99.5 98.5

Hydrophobic, Hydrophilic Hydrophilic Hydrophilic

General Operating Pressure, bar 9.8-19.6 7.5

Maximum Operating Pressure, bar 29.4 41

Maximum Operating Temperature (˚C) 40 40

Feed pH range 2-10 2-10

Residual Chlorine (ppm) 0 0

29

Figure 3.2 Flow diagram of membrane experimental set up

30

Each experiment run was conducted about 1 day, which consist of 10 hours of

precompaction and 8 hours of membrane filtration run. The membrane experiment was

setup the pressure at 15 bar for NF and 20 bar for RO. The steps of experiment are

demonstrated in figure 3.3.

Before starting an experimental run, pre-compaction of membrane should be done.

A new membrane should be inserted in filtration unit.

To get constant permeate flux, system is operated with Mili-Q water for 10 hours.

The experimental run was conduct for 8 hours.

Permeate flux were collected every hours.

Permeate samples were collected at 8 hours.

TEG solution

TEG concentration

0.1 %vol, 5 %vol,

10 %vol, 20 %vol

Fixed feed temperature

(25oC)

ConcentrateFeed

NF ROPermeate

Run 8 hours

Measurement

Permeate flux

Permeate samples were collected at 8 hours

Analysis by Gas Chromatograph (GC)

Pressure at 15 bar for

NF and 20 bar for RO

Membrane filtration

Figure 3.3 Flowchart of membrane filtration experiment

Feed Concentrate

Permeate

Run 8 hours

31

The compound rejection (%) by membrane was calculated as follows:

% 1 100p

f

CR

C

Equation 3.1

Where Cp = solute concentration in permeate, mg/L

Cf = solute concentration in feed, mg/L

The permeate flux (m3/ m

2.d.bar))

of compound was calculate as follows

.

QJ

A P Equation 3.2

Where Q = flow rate of permeate, m3/d

A = Active surface area membrane of membrane, m2

P = Applied pressure, bar

Normalized flux (N) is ratio of permeate flux at time t to its initial value that is aimed to

study stability of permeate flux along the filtration cycle.

v

o

JN

J Equation 3.3

Where Jv = Permeate flux at time t (m3/m

2.d.bar)

Jo = Initial permeate flux (m3/m

2.d.bar)

3.2 Phase II: Membrane of Pervaporation

3.2.1 Materials

The characteristics of pervaporation membrane were reported in Table 3.3

Table 3.3 List of Pervaporation Membranes and Its Properties

Source: (Sato and Nakane, 2007)

Properties NaA zeolite membrane

Module type Tubular

Hydrophobic, Hydrophilic Hydrophilic

Pure water flux, (kg/m2h) 4.0

Separation factor >5,000

Maximum operating temperature, (°C) 150

Maximum operating pressure, (bar) 0.98

32


5 liters of TEG (Triethylene Glycol) solution was poured inside double wall stainless steel

feed tank, in which 30, 40, 50 and 70°C of temperature were controlled using heater. A

circulating pump connected with flow meter for flow rate adjustment, would deliver TEG

solution from feed tank to membrane module unit at approximately 1 L/min of flow rate.

The stainless steel membrane module unit has 0.03 m2 of effective surface area. Pressure

gauges were installed at feed and concentrate sides to determine pressure. Moreover,

membrane system was operated in recycle mode that concentrate is sent back to feed tank.

During experiments the downstream pressure will be keep below 5 mbar by using a

vacuum pump. Permeate will be collect into cold trap and cooled by gel ice pack at

temperature below -10˚C. Permeation fluxes are determined by weighing permeate

collected over a given period of time in the cold traps. Composition of both the feed and

permeate mixtures will be determine by using gas chromatography. The steps of

experiment are demonstrated in figure 3.4.

TEG solution

TEG concentration

0.1 vol%, 5 vol%, 10 vol%Feed temperature

30°C, 40°C, 70˚C

Pressure at permeate side

below 5 mbar

Concentrate

Feed

Zeolite Membrane

Permeate

Run 8 hours

Pervaporation

Vacuum Controller

Vacuum

Pump

Valve

Digital Balance

Measurement Permeate flux

Cold Trap

At cold trap use temp. below 0 ˚C

Permeate samples were collected at 8 hours

Analysis by Gas Chromatograph (GC)

Figure 3.4 Flowchart of pervaporation membrane experiment

Pervaporation

NaA zeolite

Membrane

Concentrate

Permeate

Run 8 hours

33

Figure 3.5 Flow diagram of pervaporation experimental set up

34

Performance properties of a given pervaporation membrane were defined by the separation

factor (Eq.3.3) and permeate fluxes J (Eq.3.2)

/

/

/

water org permeate

water org

water org feed

C C

C C Equation 3.3

Where Corg = Denote the weight fraction of organic, g

Cwater = Denote the weight fraction of water component, g

The membrane will be operating for at 8 hours with each concentration. Permeate samples

and permeate flux will be collected at 8 hours for TEG measurement, calculated by

equation 3.2.

3.3 Phase III: Design Pre-Treatment Process to Treat TEG Wastewater

3.3.1 Materials

The characteristics of microfiltration (MF) and ultrafiltration (UF) membrane were

reported in Table 3.4 and 3.5.

Table 3.4 List of MF Membranes and Its Properties

Membrane Properties

Model number Ceramic OBE Cartridge

Pore size (µm) 0.3

Area of membrane (m2) 5.7

Pure water flux (LMH/bar) 2,500

pH range 5.5-9.5

Module Diameter (mm) 610

Module Length (mm) 2,972

Temperature (°C) 5-38

Source: Mazuma Company (2013)

35

Table 3.5 List of UF Membranes and Its Properties

Membrane Properties

Model number UFH-PST-90

Standard 4040

MWCO (KD) 50-60

Pure water flux (LMH/bar) 17.2

Area of membrane (m2)

2.5

pH range 2-13

Module Diameter (mm) 90

Module Length (mm) 1,170

Temperature (°C) 5-45

Source: Shanghai Megavision Membrane Engineering and Technology (2013)

Permeate flux can be enhanced by pretreating the feed. This technique is commonly used

either to remove particles that may cause clogging in the module or to prevent particles or

macromolecules from reaching and depositing on the membrane surface, or to reduce the

total contaminant load in downstream membrane modules.

The main objective of this phase was oil and grease, organics and inorganics compound

separation in real wastewater from GSPs before pass through membrane filtration

(NF/RO) process.

A real TEG wastewater should be found the wastewater characteristics of each

TEG concentrations.

To get concept of pre-treatment process to oil and grease, organics and inorganics

compound separation.

The first pre-treatment process use suction pump wastewater up from under the

tank which sending to microfiltration (MF) membrane with 0.3 µm. To remove

organics and inorganics compound such as TSS parameter.

After that use ultrafiltration (UF) membrane with 0.01-0.02 µm that can be treated

oil and greases before pass through membrane filtration (NF/RO) process.

3.4 Indicative Methods for TEG

3.4.1 TEG analysis by gas chromatograph (GC)

Indicative method for TEG (Triethylene glycol) measurement is analytical by gas

chromatograph (GC). However, the measurement was applied with concentrated and

methanol 99.9%. The steps of analysis are demonstrated in below.

36

Process of preparation

1. Sample dilution in the solvent Methanol when received the sample need to assess

the probability that the concentration of TEG in the calibration curve or not (0.1-

2%). Used the concentration 10% of TEG and then have to sample dilution 10 times

before injection by pipette the volume of sample 100 µL into vial that has size 1.5

mL and then adding more methanol 900 µL. After that analytical by gas

chromatograph (GC).

2. TEG sample to be analyzed must be stored in the refrigerator at 4 °C before

analyzed and should be left at room temperature for about one hour.

3. Appropriate sample volume for analysis should have a minimum volume of 3 ml.

Process of preparing a standard solution to Calibration curve

1. Preparation of standard solution concentration 10% TEG stock solution.

2. Diluted standard solution from the number 1 of process of preparation by various

concentrations from 0.1, 0.25, 0.5, 1.0 and 2.0%, respectively.

3. Triethylene Glycol compounds analyzed with GC Agilent HP 6890.

State of a GC Agilent HP 6890 for analysis of compounds triethylene glycol.

1. Detector 250°C

- Air and adjusting the pressure to 400 psi.

- H2 gas and adjusting the pressure to 40 psi.

- N2 gas and adjusting the pressure to 20 psi.

2. Temperature program

Parameter Temperature

(°C)

Hold

(min)

Runtime

(h)

Initial 100 2 3

Ramp. 1, (25 °C/min) 250 10 18

3. Column : Restex Rxi 624 sil MS 30m x 0.25m x 1.4m

Mode: Constant Pressure

Flow: 1.2 ml/min

Outlet: Ambient

Average: 25 cm/sec time 18 min

4. Inlet

Inlet: Back

Mode: Splitless

Heater: 250 °C, 7.78 psi, flow 24.1 ml/min

Split vent: 19.9 ml/min at 0.1 ml

37

Analysis result

1. Preparation of Calibration Curve

Concentration (%) Peak area

0.1 1680.4

0.25 4181.3

0.5 9369.2

1 20126.4

2 40400.2

2. Determination the accuracy of the analysis by the TEG solution by injection 7 times.

3. The result from gas chromatograph will be displayed the value of rejection (%).

38

Chapter 4

Results and Discussions

The efficiency of membrane filtration, pervaporation process and pre-treatment process for

TEG (Triethylene The efficiency Glycol) separation and recovery as well as their

separation and recovery mechanism are presented in this chapter. In the high pressure

membrane filtration (Phase I), varying concentrations of TEG (Triethylene Glycol)

solution were tested with various membrane types. In pervaporation process (Phase II),

varying concentrations and temperatures of TEG (Triethylene Glycol) solution were tested

with zeolite membrane. Moreover, in the design pre-treatment process for treat TEG

wastewater (Phase III), using two types of membrane for pre-treatment wastewater before

entering NF and RO membrane. The suitable conditions derived from membrane filtration

and design a pre-treatment process was tested together. Finally, the details are presented in

the subsequent sections.



The properties of the membrane used in this study are presented in Table 4.1.

Table 4.1 Membrane Characteristics

Type Membrane MWCO

a

Pure water

flux

Surface

Material of

Membrane

Salt rejection b

(%)

(Da) (LMH/bar) NaCl MgSO4

NF TS40 200 4.48 Polypiperazine

amide 40-60 99

TS80 150 7.84 Polyamide 80-90 97

RO ACM5 - 5.75 - 98.5 -

NTR759HR - 1.70 - 99.5 -

a is from Manufacturer, b of 1,000 mg L-1

NaCl and 2,000 mg L-1

MgSO4

All there membranes are hydrophilic properties. The pure water fluxes of TS80 and TS40

are more as they have the biggest membrane pore in all the studied membranes. The main

difference in the two NF membranes was salt rejection rate. ACM5 and HTR759HR

completely removed salt, either monovalent or divalent ion, from the solution. Moreover,

TS40, TS80, ACM5 and NTR759HR were tested with different concentrations as: 0.1, 5,

10, 20 and 30 % of TEG concentrations. The membrane filtration operation was conducted

for 8 hours.

39

4.1.2 Permeate flux

The result of permeate flux of all tested membranes are presented in Figure 4.1.

(a) NF - TS40

(b) NF – TS80

0.02

0.7

1.38

2.06

0 1 2 3 4 5 6 7 8

Per

mea

te F

lux (

L/m

2.h

.ba

r)

Time (h)

0.1% TEG 5% TEG 10% TEG 20% TEG

0.04

2.04

4.04

6.04

8.04

0 1 2 3 4 5 6 7 8

Per

mea

te F

lux (

L/m

2.h

.bar)

Times (h)

0.1% TEG 5% TEG 10% TEG 20% TEG

40

(c) RO - ACM5

(d) RO – NTR 759 HR

Figure 4.1 Permeate fluxes of membrane filtrations

Flux reduction was observed with the filtration period. The detailed results of permeate

flux are mentioned in Appendix B (Table B-1, B-2. B-3 and B-4).At higher concentration,

lower permeate flux was observed that was corresponding with finding in the previous

0

1.2

2.4

3.6

4.8

6

0 1 2 3 4 5 6 7 8

Per

mea

te F

lux (

L/m

2.h

.bar)

Time (h)

0.1% TEG 5% TEG 10% TEG 20% TEG

0

0.32

0.64

0.96

1.28

1.6

0 1 2 3 4 5 6 7 8

Per

mea

te F

lux (

L/m

2.h

.bar)

Time (h)

0.1% TEG 5% TEG 10% TEG 20% TEG

41

study. Fast flux reduction resulted at initial period (around first 4 hours), and slowly

declined. The flux reduction might be resulted from progressive membrane fouling with

filtration period due to pore blocking and sorption of compound inside membrane pore or

on membrane surface. Moreover, the lower permeate flux also presented at higher

concentration applied. It might be resulted from more effect of concentration polarization

and membrane fouling at high concentration.

Figure 4.2 presents comparison of normalized flux at 8th

hours of filtration of all the

membranes.

Figure 4.2 Normalized flux of direct filtration at different compound concentrations

The detailed results of normalized flux are mentioned in Appendix B (Table B-6). As

presented in Figure 4.2, TS40 showed the lowest normalized flux at high concentration

applied (20 % TEG) as compared to other membrane used. It resulted because the pore of

TS40 membrane was very large (high MWCO) as compared to others. Therefore,

membrane fouling, which possibly blocked TS40 pore, might lead to permeate flux

reduction and consequently lowest normalized flux as compared to others. For RO

expected higher TEG (Triethylene Glycol) removal than NF. TS80 showed equally high

normalized flux in all experiments. At the low concentrations (5 and 10 %TEG), ACM5

showed lowest normalized flux as compare to other. Similarly, lower normalized flux of all

types of membranes at high concentrations might be resulted from membrane fouling.

Membrane fouling is illustrated in Figure 4.3.

TS40 TS80 ACM5 NTR759HR

0.1% TEG 0.91 0.70 0.78 0.53

5% TEG 0.64 0.72 0.30 0.76

10% TEG 0.86 0.79 0.33 0.50

20% TEG 0.38 0.80 0.62 0.56

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Norm

ali

zed

Flu

x

42

Figure 4.3 Membrane fouling

4.1.3 Rejection

The rejections of synthetics TEG (Triethylene Glycol) with direct membrane filtration are

shown in Figure 4.4.

Figure 4.4 Removal efficiency of synthetic wastewater thought membrane filtration The lowest removal was observed at the highest concentration applied (20% TEG) in all

experiments. The detailed results of removal are mentioned in Appendix B (Table B-8). As

the MWCO of ACM5 and NTR759HR is smallest comparing with other membranes, the

highest removal efficiency of TEG can be expected. As the lowest TEG concentration (0.1

and 5 %TEG) NF-TS40 showed around 71-81% removal for different concentrations of

TEG. NF-TS80 showed around 60-67% removal for different concentrations of TEG.

0

20

40

60

80

100

0.1% TEG 5% TEG 10% TEG 20% TEG

% R

emoval

Triethylene glycol Concentrations

NF-TS40 NF-TS80 RO-ACM5 RO-NTR 759 HR

Low concentration of TEG High concentration of TEG

43

Conversely, higher removal of TEG in RO-ACM5 and RO-NTR 759 HR were observed at

low concentration. The predominant removal mechanism of these membranes might be

adsorption of TEG on membrane. As the lowest TEG concentration (0.1 and 5 %TEG)

RO-ACM5 showed around 83-89% removal for different concentrations of TEG. RO-

NTR759HR showed around 87-96% removal for different concentrations of TEG. Hence,

lower membrane removal presented at high TEG concentration, which accelerated

membrane surface saturation at initial period. Higher removal of TEG was observed at

lowest concentration. It resulted because membrane fouling when increased

concentrations, developed at low concentration, reduced membrane pore size.

Consequently, higher removal of TEG was found at lowest concentration. Moreover, other

factors like surface charge and roughness of membrane might result higher TEG removal

in NF-TS40 and RO-NTR759HR.

Furthermore, lowest removal was observed at the highest concentration applied (20 %

TEG) in all experiments. It resulted because membrane fouling and pore absorption when

increased TEG concentrations and reduced membrane pore size. Moreover, the properties

of TEG will absorb water content in the natural gas. This means that, when in contact with

a stream of natural gas that contains water, TEG will serve to steal the water out of the gas

stream. This operation is called absorption (Asadollahi et al., 2010). As the TEG are a

highly viscous solvent in comparison to water and other solvent such as ethanol and

methanol. This may be relating to the Eq. (4.1), the viscosity of TEG to be high and hence

the result for permeate fluxes is slightly lower and in the pore of membrane had TEG

concentrations by pore absorption. Therefore, components of the permeated had amounts

of TEG concentrations which can pass through pore of membrane with water in permeate

side.

T

PJ

R

Equation 4.1

Where J = permeate flux, m3/ m

2.day

ΔP = Pressure difference

µ = Viscosity

RT = Resistance

4.2 Phase II: Pervaporation Process

Pervaporation process was only tested with synthetic wastewater concentrations of 0.1, 5

and 10 % TEG with temperature variation of 30, 40 and 700C. The permeate flux was

inadequate for definitive results since the beginning of the experiments. It was also

observed that at lower concentrations of TEG, membrane performance was inadequate and

thus further testing were not conducted using real wastewater as done with NF and RO

membranes. The results of permeate flux; separation factor and rejection are presented in

subsequent subsections 4.2.1, 4.2.2 and 4.2.3.

4.2.1 Permeate flux

As a general rule of thumb, in processes like pervaproration, vapor permeation and

membrane distillation, the permeate flux is measure in kg/m2.h. The permeate flux

measured for pervaporation is shown in figure 4.5. It can be observed that the flux is high

at 700C but at other temperatures the flux is nearly negligible.

44

Figure 4.5 Permeate fluxes of pervaporation process

4.2.2 Separation factor

Separation factor is actually a ratio of ratios, and small changes in composition can lead to

large changes in the ratio, especially at low feed concentrations and high permeate

concentrations. It is a measure of performance of a system to separate two solutes. The

results of separation factor of TEG from water for all tested parameters are presented in

figure 4.6. It can be observe from figure 4.6 that 0.1 TEG at 700C and 10 % TEG at 40

0C

present a higher separation factor but as observed in literature for other organic compound

they are still quit less.

Figure 4.6 Separation factor of pervaporation process

0.69

6.81

0.53 0.47 0.58

0

2

4

6

8

0.1%TEG at

30°C

0.1%TEG at

70°C

5% TEG at

30°C

10%TEG at

30°C

10% TEG at

40°C

Per

mea

te F

lux (

kg/m

2.h

)

55

487

97

228 246

0

200

400

600

0.1%TEG at

30°C

0.1%TEG at

70°C

5% TEG at

30°C

10%TEG at

30°C

10% TEG at

40°C

Sep

ara

tion

Fact

or

45

From Figure 4.5 and 4.6, it is obvious that as the TEG concentration increases, the

permeate flux decreases. The detailed results of permeate flux are presented in Appendix D

(Table D-1).

The separation factor observed, slightly increase with increasing TEG concentration. The

detailed results of separation factor are mentioned in Appendix D (Table D-3). This is due

to the fact that the separation factor is actually a ratio (Equation 3.3), and small changes in

composition can lead to large changes in the ratio, especially at low feed concentrations

and high permeate concentrations.

Furthermore, the effect of temperature on the permeation flux and separation factor was

also studied. As seen in Figure 4.5 and 4.6, both the permeate flux and separation factor

increases with increasing feed temperature of 70°C. This may be due to the fact that as the

temperature increases permeate also increases significantly as a result, the separation factor

increases. In addition, the feed viscosity has a major impact on the transport resistances in

the module.

In PV membrane at concentration of solute 10% or less, the membrane becomes hardly any

selectivity is obtained. Thus the results are not reliable for any interpretation, the

separation factor and flux cannot be co-related in terms of diffusion characteristics but

temperature plays an important role in flux due to its influence in vapors pressure gradient.

4.2.3 Rejection

The overall TEG separation efficiency of pervaporation process for treatment of 0.1%, 5%

and 10% TEG concentrations is presented Figure 4.7.

Figure 4.7 Removal efficiency of synthetic wastewater thought pervaporation process

All of experiments were conducted at lowest TEG concentration with different the applied

temperature (30°C, 40°C and 70°C). The detailed results of removal are presented in

Appendix D (Table D-2). The lowest removal was observed at the lowest temperatures and

TEG concentrations applied (0.1%, 5% and 10%TEG at 30°C) in all experiments. The

detailed results of removal are accessible in Appendix B (Table B-3). At 30°C with 0.1%

33.16

5.39

11.19

71.02

49.58

0

10

20

30

40

50

60

70

80

0.1% TEG 5%TEG 10%TEG 10%TEG 0.1% TEG

30°C 40°C 70°C

Rej

ecti

on

(%

)

Triethylene Glycol concentration and Temperature (°C)

46

and 5% of TEG concentration, removal varied in range of 5-33% for different TEG

concentrations.

Conversely, higher removal of TEG in pervaporation process was observed at higher

temperature (40°C and 70°C). At 40°C with 10% TEG concentration, removal was around

71% for 10% TEG concentration. Moreover, at 70°C with 0.1% TEG concentration around

50% removal for 0.1% concentrations of TEG was observed. Thus, the efficiency for

separation and recovery TEG wastewater by using pervaporation process depended on the

temperature values and the TEG concentrations.

In principle, permeation rate of a liquid depends on the interaction between polymeric

membrane and the penetrant. For a given liquid the flux will be influenced by the increased

interaction between the particular polymeric membrane and its affinity towards it. The

transport of liquid mixtures through a polymeric membrane is generally much more

complex. In binary liquids, the flux can be described in terms of solubility and diffusivity

but can be strongly influenced by both liquids in the binary solution.

4.3 Phase III: Design Pre-Treatment Process to Treat TEG wastewater

Membrane processes such as microfiltration (MF), ultrafiltration (UF) are increasingly

being applied for treating oily wastewater (Bhave and Fleming, 1988, Chen et al., 1991,

Daiminger et al., 1995). To treat real wastewater from the GSP, a pretreatment process was

deemed necessary to remove large suspended particles and oil/grease, especially when

membranes like NF and RO with thin-channel were employed to separate TEG from real

wastewater. NF and RO membrane are less tolerant to suspended solids, oil and grease.

Without a proper pretreatment membrane fouling will be the predominant force that

determines membrane performance.


The pre-treatment processes in this study was essential as the second part of the research

focused on treating real wastewater from the GSP which contained suspended solids,

oil/grease and some detectable volatile compounds. Thus it was necessary to focusing on

the selection of proper pretreatment. Membrane material used for MF and UF were

narrowed down to be ideal for pretreatment due to their MWCO, pore size and its

distribution.

Permeate flux is an important parameter to characterize membrane separation efficiency

(Wu et al., 1999). With the development of polymer material science and technology,

many kinds of polymer membranes have been invented or improved in order to increase

permeate flux (Zaidi et al., 1992). In this section the properties of the membrane used for

pretreatment are presented. Pure water flux was estimated using Mili-Q water for both MF

and UF membrane.

Two membranes were used for pretreatment in the following series respectively:

1. Cartridge microfiltration membrane to remove suspended solids

2. Hollow fiber ultrafiltration membrane to remove oil and grease.

In table 4.2 and 4.3 characteristics of the microfiltration and ultrafiltration membrane are

presented.

47

4.3.2 Efficiency of TEG wastewater before and after pre-treatment process

For comparative reasons the wastewater characteristics of real TEG wastewater from Gas

Separation Plants are showed in Table 4.4. Subsequently the wastewater characteristics and

efficiency removal of this wastewater after MF and UF membranes pre-treatment are

showed in Table 4.3, 4.4, 4.5 and 4.6.

Table 4.2 Wastewater Characteristics of Real Wastewater from Gas Separation

Plants

Parameter Testing Unit Test Results

0.5% TEG 8.3 %TEG

Mercury mg/L 0.001 0.002

Cadmium mg/L <0.02 <0.02

Chromium mg/L <0.10 <0.10

Copper mg/L <0.10 <0.10

Iron mg/L 0.79 0.12

Lead mg/L <0.10 <0.10

Zinc mg/L <0.10 <0.10

Arsenic mg/L <0.01 <0.01

BOD5 mg/L 1,843 974.51

COD mg/L 8,546 9.73×104

Oil & Grease mg/L 453.2 797.6

TDS mg/L 6,969 1.158×105

TSS mg/L 257 546

Table 4.3 Wastewater Characteristics of Real Wastewater After MF Membrane Pre-

Treatment

Parameter

Testing Unit

Test Results

MF membrane Removal (%)

0.5% TEG 8.3% TEG 0.5% TEG 8.3% TEG

BOD5 mg/L 1,556 963.41 15.57 1.14

COD mg/L 8,267 9.60×10

4 3.26 1.34

Oil and Grease mg/L 419.20 750.80 7.50 5.87

TDS mg/L 5,595 1.01×10

5 6.58 12.17

TSS mg/L 154 247 40.08 54.76

48

Figure 4.8 Design pre-treatment processes to treat TEG wastewater

49

Table 4.4 Wastewater Characteristics of Real Wastewater After UF Membrane Pre-

Treatment

Parameter

Testing Unit

Test Results

UF membrane Removal (%)

0.5% TEG 8.3% TEG 0.5% TEG 8.3% TEG

BOD5 mg/L 95 750 93.89 22.15

COD mg/L 5,667 6.60×104 31.45 31.25

Oil & Grease mg/L 57.8 78.9 86.2 89.49

TDS mg/L 3,467 7.88×104 38.03 21.98

TSS mg/L 36 14 76.62 97.22

4.3.3 Permeate flux of TEG in Real wastewater

To test with real wastewater using RO-ACM5 and NF-TS80 membranes, the wastewater

first needs be pretreated to protect membrane from fouling by suspended solids and

oil/grease. The pretreatment is done in two steps:

1. Suspended solids removal using cartridge microfiltration (MF) membrane.

2. Oil and grease removal employing a hollow fiber ultrafiltration (UF) membrane.

After pretreatment of real wastewater with 0.5 % and 8.3 % TEG infestation, the liquid is

sent to RO-ACM5 and NF-TS80 membranes separately. The resultant permeate flux for

RO-ACM5 and NF-TS80 membranes with 0.5 and 8.3 % TEG concentration are presented

in figure 4.9.

(a) NF – TS80 with Real 0.5% of real wastewater

0

1

2

3

4

5

6

7

8

0 1 2 3 4 5 6 7 8

Per

mea

te F

lux (

L/m

2.h

.bar)

Time (h)

0.1% of Synthetic wastewater 0.5% of Real wastewater

67%

50

(b) RO-ACM5 with Real 0.5% of real wastewater

Real wastewater showed low permeates flux as compared to synthetic wastewater. The

detailed results of permeate flux are presented in Appendix B (Table B-5). For NF-TS80

and RO-ACM5 with 0.5% of real TEG wastewater, there was a reduction of 67% and 56%

in permeate flux for real wastewater as compared with synthetic wastewater. The reduction

in flux is attributed to membrane fouling on membrane surfaces due to undetectable

volatile compounds present in the wastewater which could not be removed using

pretreatment.

(c) NF-TS80 with Real 8.3% of real wastewater

0

1

2

3

4

5

6

0 1 2 3 4 5 6 7 8

Per

mea

te F

lux (

L/m

2.h

.bar)

Time (h)

0.1% of Synthetic wastewater 0.5% of Real wastewater

0

0.4

0.8

1.2

1.6

0 1 2 3 4 5 6 7 8

Per

mea

te F

lux (

L/m

2.h

.bar)

Time (h)

10% of Synthetic wastewater 8.3% of Real wastewater

10.26%

56%

51

(d) RO-ACM5 with Real 8.3% of real wastewater

Figure 4.9 Permeate fluxes of membrane filtrations with real TEG wastewater

RO membrane showed similar reduced performance in permeate flux (10.26%) as NF-

TS80 (10.44%) at 8.3% TEG concentration than their permeate flux with synthetic

wastewater because the both of membranes had stronger sorption of suspended solid and

oil and grease on membrane surfaces.

4.3.4 Rejection of TEG in Real wastewater

The overall TEG removed efficiency are compared with synthetic wastewater and real

wastewater after pre-treatment processes for TS80, ACM5 with TEG concentration of 0.5

% and 8.3 % wastewater is presented in figure 4.10.

0

0.2

0.4

0.6

0.8

1

0 1 2 3 4 5 6 7 8

Per

mea

te F

lux (

L/m

2.h

.bar)

Time (h)

10% of Synthetic wastewater 8.3% of Reall wastewater

10.44%

52

(a) NF-TS80 with 0.5% of real wastewater

(b) NF-TS80 with 8.3% of real wastewater

The efficiency of pre-treatment process with NF-TS80 using real wastewater with 0.5% of

TEG concentrations was significantly higher than using the same membrane to treat

synthetic wastewater by approximately 73%. The detailed results of removal are described

in Appendix B (Table B-4).While using NF-TS80 with real wastewater containing 8.3%

TEG concentration, showed slightly lower efficiency than synthetic wastewater by

approximately 47.15%.

60.00

72.980

0

20

40

60

80

Synthetic wastewater Real wastewater

Rej

ecti

on

(%

) o

f T

EG

50.720

47.150

0

15

30

45

60


Rej

ecti

on

(%

) of

TE

G

53

(c) RO-ACM5 with 0.5% of real wastewater

(d) RO-ACM5 with 8.3% of real wastewater

Figure 4.10 Removal efficiency of real 0.5 and 8.3% of TEG wastewater

In case of RO membrane with wastewater containing 0.5 and 8.3% TEG concentrations,

showed significantly higher removal than membrane filtration by approximately 95% and

78%, respectively but had very less permeate flux than NF membrane. However, permeate

flux of RO membrane after pre-treatment process is slightly lower than only membrane

filtration by approximately 10.44% and 56%, respectively. Thus, it might need frequent

83.78

94.79

0

20

40

60

80

100


Rej

ecti

on

(%

) o

f T

EG

76.060 77.560

0

20

40

60

80


Rej

ecti

on

(%

) of

TE

G

54

membrane cleaning with pre-treatment membrane process when used real TEG

wastewater.

4.3.5 Real wastewater characteristics after NF and RO treatment

Parameters tested for real wastewater after pass through the pre-treatment process (MF and

UF membranes) and membrane filtration (NF and RO membranes) are presented in Table

4.5 and 4.6. The parameters included BOD, COD, Oil and Grease, TDS, TSS.

Table 4.5 Wastewater Characteristics of Real Wastewater After NF Membranes Pre-

Treatment

Parameter

Testing Unit

Test Results

NF membrane Removal

(%)

0.5% TEG 8.3% TEG 0.5% TEG 8.3% TEG

BOD5 mg/L 65 300 31.58 60.00

COD mg/L 1,533 1.23×10

4 72.95 81.36


TDS mg/L 5,163 1.02×10

4 84.54 87.06

TSS mg/L 6 4 83.33 71.43

Table 4.6 Wastewater Characteristics of Real Wastewater After RO Membranes Pre-

Treatment

Parameter

Testing Unit

Test Results

RO membrane Removal

(%)

0.5% TEG 8.3% TEG 0.5% TEG 8.3% TEG

BOD5 mg/L 40 100 57.89 86.67

COD mg/L 1,387 6,933 75.52 89.49


TDS mg/L 4,277 9,887 87.19 87.43

TSS mg/L 3.33 3.56 90.75 74.57

The wastewater characteristics after pre-treatment and membrane filtration using both NF-

TS80 and RO-ACM5 with 0.5% TEG and 8.3% TEG wastewater was significantly lower

than wastewater characteristics than original wastewater studied in the earlier section. The

detailed results of wastewater characteristics are tabulated in Table 4.2, 4.3, 4.4, 4.5 and

4.6. Thus, the pre-treatment process for treating TEG wastewater are particularly important

55

to protect membrane from fouling by suspended solids and oil/grease before tested with

real wastewater using RO-ACM5 and NF-TS80 membranes.

Therefore, the pre-treatment process should be applied before using membrane filtration

with NF and RO membrane which are proposed for industrial applications due to its high

recover efficiency, high permeate flux with low TEG concentrations. However, low

recover efficiency and low permeate flux was observed when experiments were done with

high TEG concentrations in range 20% TEG concentration in synthetic and real

wastewater. Hence, the pre-treatment process and membrane filtration are the interesting

option for application in terms of time used for operation (Triethylene glycol recovery) and

maintenance (membrane cleaning).

56

Chapter 5

Conclusions and Recommendations

The main objective of this study was to identify the effective technology for Triethylene

glycol (TEG) separation and recovery in wastewater from Gas Separation Plants. This

research comprised of three main phases, namely, Phase I: Membrane filtration, Phase II:

Pervaporation process and Phase III: Design pre-treatment process to treat TEG

wastewater. Moreover, the applicability of this research in the industrial sector was also

investigated.

5.1 Conclusions

In this research, it was found that the pre-treatment process for treat TEG wastewater

(Phase III) to protect membrane from fouling by suspended solids and oil/grease before

testing real wastewater using RO-ACM5 and NF-TS80 membranes. The studied

membranes had high efficiency to separate and recover TEG from real wastewater. Based

on the results obtained from testing synthetic wastewater with four membranes we could

optimize the treatment conditions like pressure application, membrane selection and select

the best two membranes to treat real wastewater. Moreover, a detailed study was

conducted in membrane filtration and pre-treatment processes to reveal their basic removal

mechanisms and efficiency.

Phase I: High Pressure Membrane Filtration

Nanofiltration membrane with high salt rejection (TS40) was the most effective membrane

for TEG recovery among membrane tested at low concentrations. It recovered more than

80% of TEG from the dilute stream. While NF membrane (TS80) with high salt rejection

also showed 60-67% TEG recovers. RO membrane (ACM5 and NTR759HR) removal

TEG in rang of 83-95%, in which the membrane having less MWCO showed higher

removal efficiency but compromising on flux. Moreover, NF membrane (TS80) showed

better performance in terms of permeate flux as compared to NF-TS40 membranes. While

in RO membrane (ACM5) performed better than RO-NTR759HR with synthetic

wastewater. It was uniformly observed that all the tested membrane performed well at

lower concentration but as the concentration increased to 20% TEG there was a sharp

reduction in flux with unstable rejection. The low permeate flux at high concentrations of

TEG can be attributed to concentration polarization and membrane fouling.

Phase II: Pervaporation Process

The pervaporation process was conducted with 0.1, 5 and 10% of TEG concentrations in

synthetic wastewater with temperature variation of 30, 40 and 70°C of each concentration.

The permeate flux of TEG/water mixture through a zeolite membrane was found to vary

from 0.47-0.69 kg/m2.h over a concentration range of 0.1-10% TEG at 30°C. Moreover,

the permeate flux at a concentration of 0.1% TEG at 70°C was found to be 6.81 kg/m2.h.

While the permeate flux at a concentration of 10% was found with 0.58 kg/m2.h at 40°C.

Also, the separation factor was 246 for 10% TEG at 40°C. The flux and the separation

factors obtained indicate that pervaporation process with NaA Zeolite membrane is not

attractive and the system does not performed well at lower concentration of solutes.

57

Phase III: Design Pre-Treatment Process to Treat TEG Wastewater

To accomplish objective 2, testing with real wastewater using RO-ACM5 and NF-TS80

membranes was necessary. But the wastewater first needs to be pretreated to protect

membrane from fouling by suspended solids and oil/grease. The pretreatment was carried

out in two steps; first step is suspended solids removal using cartridge microfiltration (MF)

membrane and second step is oil and grease removal employing a hollow fiber

ultrafiltration (UF) membrane. Desirable wastewater characteristics were achieved pre-

treatment process where suspended solids and oil/grease were removed to a greater extent.

Pre-treatment process coupled with nanofiltration membrane (TS80) showed higher TEG

removal than synthetic wastewater experiments at 0.5% TEG concentration by

approximately 73%. While reverse osmosis membrane (ACM5) showed slightly higher

removal for TEG than synthetic wastewater experiments with 0.5% TEG concentration

also by approximately 95%. In case of 8.3% TEG concentration, nanofiltration (TS80) and

reverse osmosis (ACM5) membrane showed relatively equal to the value of synthetic

wastewater experiments by approximately 47.15% and 77.56%, respectively.

Therefore, the pre-treatment process should be applied before using membrane filtration

with NF and RO membrane which are proposed for industrial applications due to its high

removal efficiency, high permeate flux with low TEG concentrations. However, low

removal efficiency and low permeate flux was observed when experiments were done with

high TEG concentrations in range 20% TEG concentration in synthetic and real

wastewater. Hence, the pre-treatment process and membrane filtration are the interesting

option for application in terms of time used for operation (Triethylene glycol recovery) and

maintenance (membrane cleaning).

In light of this study it can be concluded that out of the studied membranes TS80 and

ACM5 are suitable for separating TEG from wastewater only at lower concentrations as in

higher concentrations membrane fouling and reduced permeate flux causes the system to

be not suitable for industrial applications.

5.2 Recommendations for Further Study

Methodology of membrane cleaning with NF and RO membrane for industrial

application in actual experiments. The results should be useful for saving cost of

membrane that used for experiments.

The longer filtration period should be applied with real wastewater experiments

which its can found period that membrane fouling. In addition, membrane cleaning

to get back the initial permeate flux, should be tested for long experiment run. It is

more similar with the actual treatment.

In this study, low concentrations (0.1% TEG, 5% TEG and 10% TEG

concentrations) of Triethylene glycol were applied. TEG concentrations above 30

% should be tested using PV which can result in higher separation, rejection and

improve efficiency of pervaporation process.

Optimize the membrane cleaning in zeolite membrane of pervaporation process for

operation periods of several days, weeks or months.

58

Investigate the effect of the backpulse technique on the performance of MF and

UF membranes in membrane modules of pre-treatment process.

Due to oil and grease, color and suspended solids have effect on the treatment and

TEG measurement, hence application of pre-treatment such as dissolve air

floatation (DAF) and membrane technology is recommended in the next study for

pervaporation process.

59

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63

Appendix A

Experimental setup

64

Figure A-1 Membrane experimental setup

Cooling tank 25 ˚C

Dampener

Membrane Cell Module

Weight Balance

Inverter

65

Figure A-2 Details of membrane module

Figure A-2 Details of membrane module (Romchat, 2011)

180 mm

Knob A

A

Victoria Coupling

3/8 in

Concentrate Feed Water

86 mm

Area = 229 mm2

Flat Sheet Membrane

Victoria Coupling

61

.8 m

m

Plate

Permeate Tube

Body

O-ring

126 mm

66

Appendix B

Experimental data for Membrane Filtration

67

Table B-1 Permeate Flux with Synthetic TEG Wastewater using NF-TS40

Run times

(h)

Permeate Flux (L/m2.h.bar)

0.1% TEG 5% TEG 10% TEG 20% TEG

0 1.78 0.96 0.227 0.12

1 1.91 0.88 0.223 0.11

2 1.87 0.84 0.294 0.10

3 1.93 0.78 0.342 0.09

4 1.89 0.70 0.302 0.08

5 1.79 0.73 0.288 0.07

6 1.85 0.69 0.244 0.05

7 1.78 0.66 0.217 0.05

8 1.62 0.61 0.196 0.04

Table B-2 Permeate Flux with Synthetics TEG Wastewater using NF-TS80

Run times

(h)


0.1% TEG 5% TEG 10% TEG 20% TEG

0 7.58 2.61 0.690 0.15

1 7.00 2.46 0.604 0.13

2 6.54 2.35 0.656 0.16

3 6.25 2.19 0.625 0.18

4 6.12 2.16 0.575 0.15

5 5.87 2.06 0.552 0.14

6 5.70 1.97 0.544 0.13

7 5.45 1.92 0.547 0.13

8 5.33 1.87 0.546 0.12

Table B-3 Permeate Flux with Synthetics TEG Wastewater using RO-ACM5

Run times

(h)


0.1% TEG 5% TEG 10% TEG 20% TEG

0 4.86 2.57 0.203 0.000

1 4.32 2.19 0.198 0.000

2 4.38 1.86 0.194 0.000

3 4.41 1.54 0.184 0.045

4 4.25 1.48 0.123 0.031

5 3.96 0.96 0.095 0.034

6 3.88 0.95 0.073 0.045

7 3.80 0.80 0.070 0.033

8 3.79 0.78 0.067 0.028

68

Table B-4 Permeate Flux with Synthetics TEG Wastewater using RO-NTR759HR

Run times

(h)


0.1% TEG 5% TEG 10% TEG 20% TEG

0 1.33 0.89 0.078 0.000

1 1.25 0.87 0.075 0.000

2 1.17 0.88 0.072 0.041

3 1.08 0.85 0.070 0.038

4 1.00 0.83 0.061 0.045

5 0.96 0.82 0.053 0.041

6 0.83 0.73 0.048 0.033

7 0.75 0.70 0.045 0.031

8 0.71 0.68 0.039 0.023

Table B-5 Permeate Flux with Real Wastewater Infested TEG using NF-TS80 and

RO-ACM5

Run times

(h)


NF-TS80 RO-ACM5

0.5% TEG 8.3% TEG 0.5% TEG 8.3% TEG

0 3.23 1.29 2.71 0.94

1 2.66 0.60 2.40 0.46

2 2.36 0.62 1.64 0.21

3 2.22 0.59 1.52 0.19

4 1.81 0.58 1.56 0.17

5 1.80 0.55 1.44 0.14

6 1.87 0.54 1.40 0.08

7 1.79 0.50 1.69 0.07

8 1.78 0.49 1.68 0.06

Table B-6 Normalized Flux at The End of Experiment with Synthetics TEG

Concentrations of Membrane Filtration

Initial TEG

Concentration

(%)

Membrane Type

TS40 TS80 ACM5 NTR 759 HR

0.1 0.91 0.70 0.78 0.53

5 0.64 0.72 0.30 0.76

10 0.86 0.79 0.33 0.50

20 0.38 0.80 0.62 0.56

69

Table B-7 Normalized Flux at The End of Experiment with Real TEG Wastewater of

Membrane Filtration

Initial TEG

Concentration

(%)

Membrane Type

TS80 ACM5

0.1 0.260 0.308

10 0.071 0.030

Table B-8 Rejection Efficiency of Membrane Filtration with Synthetic TEG

Wastewater

Initial TEG

concentration

(%)

TEG Rejection (%)

TS40 TS80 ACM5 NTR 759 HR

0.1 80.08 60.00 83.78 87.15

5 71.06 67.32 89.12 95.74

10 35.83 50.72 76.06 59.92

20 12.12 11.52 14.96 19.38

Table B-9 Rejection Efficiency of Membrane Filtration with Real TEG Wastewater

Initial TEG

Concentration

(%)

TEG Rejection (%)

TS80 ACM5

0.1 72.98 94.79

10 47.15 77.56

70

Appendix C

Experimental setup for Pervaporation Process

71

Figure C-1 Pervaporation process setup

Zeolite membrane module Feed Tank

Cold Trap Temperature

adjustment

Vacuum pump Feed Pump Silica Gel

72

Appendix D

Experimental Data in Pervaporation process

73

Table D-1 Permeate Fluxes at The End of Experiment with Synthetics TEG

Wastewater of Pervaporation Process

Initial TEG

concentration

(%)

Temperatures (°C)

30 40 70

0.1 0.69 - 6.81

5 0.53 - -

10 0.47 0.58 -

Table D-2 Efficiency of Pervaporation Process with Synthetics TEG Wastewater for

TEG Rejection

Initial TEG

concentration

(%)

Temperatures (°C)

30 40 70

0.1 33.16 - 49.58

5 5.39 - -

10 11.19 71.02 -

Table D-3 Separation Factors at The End of Experiment with Synthetics TEG

Wastewater of Pervaporation Process

Initial TEG

concentration

(%)

Temperatures (°C)

30 40 70

0.1 55 - 487

5 97 - -

10 228 246 -

Methodology to calculation the Separation factor

Performance properties of a given pervaporation membrane were defined by the separation

factor ()

/

/

/

water org permeate

water org

water org feed

C C

C C

Where Corg = Denote the weight fraction of organic, g

Cwater = Denote the weight fraction of water component, g

For the example

1. Initial TEG concentration of 0.1% with the temperature at 70°C

Unit: %

Unit: kg/m2.h

74

Solve

From the formula:

/

/

/

water org permeate

water org

water org feed

C C

C C

At the permeate side:

Cwater = 13,135.851 kg

Corg = 0.027 kg

At the feed side:

Cwater = 4.995 kg

Corg = 0.005 kg

So, the value of separation factor of 10% of TEG with temperature at 40°C;

/

13,135.851 0.027

4.995 0.005water org

= 487

2. Initial TEG concentration of 10% with the temperature at 40°C

Solve

From the formula:

/

/

/

water org permeate

water org

water org feed

C C

C C

At the permeate side:

Cwater = 98.534 kg

Corg = 0.045 kg

At the feed side:

Cwater = 4.495 kg

Corg = 0.505 kg

So, the value of separation factor of 10% of TEG with temperature at 40°C;

/

98.534 0.045

4.495 0.505water org

= 246

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Appendix E

Experimental Details for Pre-Treatment Processes

76

Figure E-1 Pre-treatment Processes

Microfiltration (MF)

Membrane

Ultrafiltration (UF)

Membrane

77

Appendix F

Photos of the experiments with real wastewater

78

Figure F-1 0.1% and 10% TEG of real wastewater

Figure F-2 Pre-treatment process by use flat sheet membranes

0.1% TEG of real wastewater 10% TEG of real wastewater

Synthetic wastewater Directly filtration by use real wastewater

after MF membrane

Pre-treatment 0.1% real wastewater by use

UF flat sheet membrane

Pre-treatment 10% real wastewater by use

UF flat sheet membrane

79

Figure F-3 Results of experiments with real wastewater

NF-TS80 with 0.1% real wastewater after

MF and UF membrane pre-treatment

R0-ACM5 with 0.1% real wastewater

after MF and UF membrane pre-treatment

NF-TS80 with 10% real wastewater after

MF and UF membrane pre-treatment

RO-ACM5 with 10% real wastewater

after MF and UF membrane pre-treatment

Membrane Based Triethylene Glycol Separation and Recovery...

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