2012 Sequential and simultaneous application of activated

University of WollongongResearch Online

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2012

Sequential and simultaneous application ofactivated carbon with membrane bioreactor for anenhanced removal of trace organicsLuong NguyenUniversity of Wollongong

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Recommended CitationNguyen, Luong, Sequential and simultaneous application of activated carbon with membrane bioreactor for an enhanced removal oftrace organics, Master of Engineering thesis, School of Civil, Mining and Environmental Engineering, University of Wollongong, 2012.http://ro.uow.edu.au/theses/3586

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School of Civil, Mining and Environmental Engineering

Faculty of Engineering

University of Wollongong, Australia

Sequential and simultaneous application of activated carbon with

membrane bioreactor for an enhanced removal of trace organics

Luong Nguyen

A thesis submitted in partial fulfilment of the

requirements for the award of the degree of

Master of Engineering

March, 2012

i

CERTIFICATION

I, Luong Nguyen, hereby declare that this thesis, submitted in partial fulfilment of the

requirements for the award of Master of Engineering by Research Degree, to the school

of Civil, Mining and Environmental Engineering, Faculty of Engineering, University of

Wollongong is wholly my own work unless otherwise referred or acknowledged. The

document has not been submitted for qualification at any other academic institution.

Luong Nguyen

ii

ABSTRACT

The occurrence of trace organics such as pesticides, pharmaceutically active

compounds, natural and synthetic hormones as well as various industrial compounds in

the aquatic environment is of great concern due to their potential adverse effects on

human health and those of other biota. Therefore, the removal of these compounds from

wastewater is an important consideration to ensure safe drinking water and better

protect the environment. In the literature, several techniques have been explored for

trace organics removal, namely, conventional activated sludge (CAS), membrane

bioreactors (MBRs), nanofiltration/reverse osmosis membrane filtration (NF/RO) and

adsorption; however a universal end-of-pipe treatment process is yet to be established.

Evidence from the literature indicates that neither MBR nor activated carbon on its own

can adequately remove all trace organics of concern. This thesis investigates sequential

and simultaneous application of activated carbon adsorption with MBR treatment for an

enhanced removal of trace organic contaminants. A set of 22 compounds representing

four major groups of trace organics including 11 pharmaceutical and personal care

products, 2 pesticides, 4 industrial chemicals and their metabolites and 5 steroid

hormones was selected for this investigation. Various investigations were conducted

during the continuous operation of a laboratory-scale MBR system for a total of 306

days. This thesis focuses on 93 days of operation of a combined MBR with granular

activated carbon (MBR - GAC system) followed by 100 days of operation of the MBR

after direct addition of powdered activated carbon (PAC) into it.

The MBR showed stable and high performance with respect to all key basic water

quality parameters (e.g., TOC, TN and turbidity) and operating parameters (e.g., pH,

and MLVSS/MLSS ratio). It was confirmed that MBR treatment can effectively remove

hydrophobic (i.e., compounds having a distribution coefficient, Log D >3.2) and readily

biodegradable trace organic compounds. The reported data also highlighted the

limitation of MBR in removing hydrophilic and persistent compounds such as

metronidazole, ketoprofen, carbamazepine, diclofenac, and fenoprop.

GAC post-treatment was observed to complement MBR treatment to obtain initially

high overall removal of less hydrophobic and biologically persistent trace organic

iii

compounds. Through long-term observation, breakthrough of 6 hydrophilic and

biologically persistent compounds (metronidazole, carbamazepine, diclofenac,

fenoprop, naproxen, and ketoprofen) was observed. Of these trace organic

contaminants, the neutral compounds (carbamazepine and metronidazole) exhibited

slower breakthrough than the rest of these compounds which were negatively charged

(diclofenac, fenoprop, naproxen and ketoprofen). The difference between the behaviour

of the neutral and the charged compounds was predicted by the single solute isotherm

parameters. The saturation of the GAC column indicated that strict monitoring should

be applied over the lifetime of the GAC column to detect the breakthrough point of

hydrophilic and persistent compounds which have low removal by MBR treatment.

The removal of the 22 selected trace organic contaminants by MBR treatment was

enhanced after direct addition of PAC into it. The high degree removal (95%) of the

hydrophobic and readily biodegradable compounds continued to be achieved in PAC –

MBR system. An immediate increase in removal efficiency of biologically persistent

hydrophilic compounds (metronidazole, fenoprop, naproxen, ketoprofen, diclofenac,

and carbamazepine), which showed low removal by MBR- only treatment, was

observed in the PAC – MBR system. However, within approximately three weeks the

removal efficiency dropped down to the level achieved before the addition of PAC. The

removal efficiency of these compounds could be recovered by adding a second dose of

PAC, raising the PAC concentration in the MBR to 0.5 g/L. The removal of the above

mentioned six persistent compounds did not drop below 60 % even after one month

(metronidazole 73 %, fenoprop 59 %, naproxen 93 %, ketoprofen 91 %, diclofenac 71

%, and carbamazepine 87%). However, except for ketoprofen and carbamazepine, the

removal efficiency of the other four problematic compounds further diminished

gradually, indicating that withdrawal of spent PAC and replenishment of fresh PAC

would be required to achieve more stable performance.

Overall, both simultaneous application of PAC within MBR and sequential application

of GAC adsorption following MBR treatment process are potential treatment processes

to enhance removal of trace organic contaminants. Based on a simple cost-benefit

analysis from the performance stability and activated carbon usage points of view, of

iv

the two processes, simultaneous application of PAC within MBR appears to be a better

option than sequential application of GAC following MBR treatment.

Keywords: Membrane bioreactor; powdered activated carbon; granular activated carbon;

adsorption; trace organic compounds and breakthrough

v

ACKNOWLEDGEMENTS

My Masters by Research study at the University of Wollongong has been an amazing

journey full of challenges, opportunities, and excitement. Things were shaky at the

beginning and without the support from many wonderful people it could have been

harder or even impossible to complete the journey. It is time for me to express my

sincere gratitude to people from whom I have received tremendous support. I would

like to express my sincere gratitude to my supervisors Dr Faisal Hai and Associate

Professor Long Nghiem for their comments and suggestions. Associate Professor Long

Nghiem is thanked for his arrangement of a postgraduate scholarship between the

University of Wollongong and the Thanh hoa provincial government, Vietnam.

I would like to thank the Thanh hoa provincial government and the University of

Wollongong for providing me scholarship to pursue my Master degree at the University

of Wollongong.

Professor William E. Price is thanked for his insightful comments and advice on

different aspects of my study. Dr Jinguo Kang is thanked for his assistance in doing

GC-MS analysis.

I would like to extend my thanks to Abdulhakeem Ali Alturki and Karin Tessmer for

their assistance in some laboratory analyses and in the operation of the MBR. Thanks

are also due to other students in membrane research group for their friendship and

companionship during my study.

Thanks are also due to Rebecca, an undergraduate student for her assistance in some of

the laboratory work.

The Mitsubishi Rayon Engineering, Japan, Activated Carbon Technologies Pty Ltd,

Australia and Australian Nuclear Science and Technology Organisation (ANSTO) are

thanked for the provision to membrane module, GAC samples, and analysis of GAC

properties, respectively. We are indebted to Professor Kazuo Yamamoto of the

University of Tokyo, Japan for introducing us to Mitsubishi Rayon Engineering.

Dad and Mum, thanks for having me.

vi

TABLE OF CONTENTS

ABSTRACT ................................................................................................................ ii

ACKNOWLEDGEMENTS ........................................................................................ v

TABLE OF CONTENTS ........................................................................................... vi

LIST OF FIGURES .................................................................................................... x

LIST OF TABLES .................................................................................................... xv

LIST OF ABBREVIATIONS .................................................................................. xvi

LIST OF SYMBOLS ............................................................................................. xviii

CHAPTER 1: INTRODUCTION .............................................................................. 1

1.1 Background of the study ................................................................................ 1

1.1.1 Trace organics in wastewater: sources and problems ................................ 1

1.1.2 Trace organic removal by membrane bioreactors ...................................... 2

1.1.3 Adsorption of trace organic on activated carbon ....................................... 3

1.2 Statement of the problem ............................................................................... 4

1.3 Objectives of the research .............................................................................. 5

1.4 Expected outcomes ........................................................................................ 5

1.5 Thesis outline ................................................................................................ 6

CHAPTER 2: LITERATURE REVIEW ................................................................... 7

2.1 Introduction ................................................................................................... 7

2.2 Trace organic contaminants .......................................................................... 7

2.2.1 Groups of trace organic contaminants ....................................................... 7

2.2.2 Sources of trace organic contaminants .................................................... 10

2.2.3 The effects of trace organic contaminants on human health and

environment ........................................................................................................... 12

2.2.4 Fate and behaviour of trace organic contaminants .................................. 16

2.2.5 Analysis of trace organic contaminants.................................................... 16

vii

2.3 Membrane bioreactor technology ................................................................ 17

2.3.1 Definition of MBR .................................................................................... 17

2.3.2 MBR application for trace organics removal ........................................... 19

2.4 Activated carbon adsorption ........................................................................ 25

2.4.1 Activated carbon ...................................................................................... 25

2.4.2 Application of activated carbon ............................................................... 25

2.4.3 Application of activated carbon with membrane bioreactor ..................... 27

CHAPTER 3: METHODOLOGY ........................................................................... 33

3.1 Introduction ................................................................................................. 33

3.2 Materials ..................................................................................................... 34

3.2.1 Selected trace organic compounds ........................................................... 34

3.2.2 Synthetic wastewater ............................................................................... 40

3.2.3 Activated carbon ...................................................................................... 40

3.3 Experimental set-up and operation protocol ................................................ 41

3.3.1 Laboratory–scale MBR set-up and operation protocol ............................. 41

3.3.2 Laboratory–scale MBR-GAC set-up and operation protocol .................... 44

3.3.3 Laboratory scale PAC - MBR set-up and operation protocol ................... 46

3.3.4 Adsorption isotherm ................................................................................ 46

3.4 Analytical techniques ................................................................................... 48

3.4.1 Total organic carbon and total nitrogen .................................................. 48

3.4.2 DO concentration, pH, turbidity, and sludge volume index ...................... 51

3.4.3 Mixed liquor suspended solids and mixed liquor volatile suspended solids ..

................................................................................................................ 52

3.4.4 Specific oxygen uptake rate (SOUR) ........................................................ 53

3.4.5 Nitrate and Ammonium ............................................................................ 53

3.4.6 Extracellular polymeric substances and soluble microbial products ........ 56

3.4.7 Trace organics analysis ........................................................................... 60

CHAPTER 4: PERFORMANCE OF MBR SYSTEM ............................................ 67

4.1 Introduction ................................................................................................. 67

4.2 Experimental set up and operation protocol ................................................ 67

4.3 Results and discussion ................................................................................. 67

viii

4.3.1 Mixed liquor suspended solids and mixed liquor volatile suspended solids ..

................................................................................................................ 67

4.3.2 Turbidity and sludge volume index ........................................................... 68

4.3.3 Dissolved oxygen concentration, pH and specific oxygen up take rate ..... 70

4.3.4 Nitrate and ammonium ............................................................................ 71

4.3.5 Total organic carbon and total nitrogen removal ..................................... 73

4.3.6 Removal of trace organic contaminants ................................................... 75

4.4 Conclusions ................................................................................................. 79

CHAPTER 5: REMOVAL OF TRACE ORGANIC CONTAMINATNS BY A

MEMBRANE BIOREACTOR (MBR) - GRANULAR ACTIVATED CARBON

(GAC) SYSTEM ....................................................................................................... 80

5.1 Introduction ................................................................................................. 80



5.3.1 Performance stability and TOC/ TN removal by the MBR- GAC system ... 81

5.3.2 Complementary removal of trace organics by MBR – GAC system .......... 83

5.3.3 Adsorption of single compound on GAC .................................................. 85

5.3.4 Breakthrough of biologically persistent hydrophilic compounds .............. 86

5.4 Conclusions ................................................................................................. 94

CHAPTER 6: REMOVAL OF TRACE ORGANIC CONTAMINANTS BY PAC

- MBR HYBRID SYSTEM ....................................................................................... 95

6.1 Introduction ................................................................................................. 95



6.3.1 Evaluation of the performance of the PAC - MBR hybrid system .............. 96

6.3.2 Removal of trace organics by PAC - MBR hybrid system ....................... 110

6.4 Conclusions ............................................................................................... 119

CHAPTER 7: CONCLUSIONS AND RECOMMENDATIONS.......................... 120

7.1 Conclusions ............................................................................................... 120

ix

7.2 Recommendations for further research ...................................................... 121

REFERENCES ....................................................................................................... 123

APPENDIX A.......................................................................................................... 144

APPENDIX B .......................................................................................................... 174

x

LIST OF FIGURES

Figure 1: Schematic description of the thesis structure. ................................................ 6

Figure 2: Configuration of MBR systems ................................................................... 19

Figure 3: Schematic diagram of the hybrid process..................................................... 29

Figure 4: Schematic illustrating the effects (a), causes (b) and mechanism (c) occurring

in an MBR after PAC addition [166]. .................................................................. 30

Figure 5: Experimental road map ............................................................................... 33

Figure 6: Membrane bioreactor (MBR) set-up (1 Feed tank, 2 Feed pump, 3 MBR , 4

Pressure gauge, 5 Permeate pump, 6 Permeate tank, 7 Computer). Dimensions of

the reactor were 360 mm (H) x 320 mm (L) x 45 mm (W)................................... 42

Figure 7: A schematic diagram of the MBR set up ..................................................... 43

Figure 8: PVDF hollow fiber membrane module used in this study (dimensions 29 cm

(L) x 17 cm (H) x 1 cm (W), Fiber length and outer diameter of 22 cm and 0.2 cm,

respectively. Membrane nominal pore size = 0.4 µm and total membrane surface

area = 0.074 m2) .................................................................................................. 43

Figure 9: Fixed bed GAC column. A borosilicate glass column (1cm diameter x 22 cm

L) filled with 7.5 g GAC was used. ..................................................................... 45

Figure 10: Combined MBR – GAC system ................................................................ 45

Figure 11: Total organics carbon and total nitrogen analyzer system (1 Auto sampler

and sample tray, 2 TOC analyzer, 3 TN analyzer unit, 4. Computer). .................. 49

Figure 12: A typical TOC calibration curve to determine TOC concentration in samples

............................................................................................................................ 50

Figure 13: A typical TN calibration curve to determine TN concentration in samples . 51

Figure 14: A typical calibration curve to determine nitrate concentration in samples .. 54

Figure 15: A typical calibration curve to determine ammonium concentration in

samples ............................................................................................................... 55

Figure 16: An Ion-chromatography system (1 Pump part, 2 Auto sampler, 3 Column

chamber, 4 Conductivity detectors, 5 System controller, 6 Computer). ................ 55

Figure 17: Schematic of sample preparation for EPS and SMP determination ............ 57

Figure 18: A typical calibration curve to determine carbohydrate concentration in

samples ............................................................................................................... 58

Figure 19: A typical calibration curve to determine protein concentration in samples . 59

xi

Figure 20: An UV-visible spectrophotometer ............................................................. 59

Figure 21: Schematic of sample preparation for GC-MS measurement of trace organics

(Reagent water is MBR feed without trace organics. MeOH - methanol, DCM –

dichloromethane, SPE – solid phase extraction, HLB -Hydrophilic-lipophilic-

balanced) ............................................................................................................. 62

Figure 22: The solid phase extraction manifold holding cartridges through which the

sample drips into the perforated chamber below, where tubes collect the effluent. A

vacuum port with gauge is used to control the vacuum applied to the chamber (1

Sample containers, 2 HLB cartridges, 3 Chamber, 4 Vacuum port). .................... 63

Figure 23: Gas chromatography-mass spectrometry system (1 Sample tray, 2 Sample

injector, 3 GCMS-QP 5000, 4 Computer) ............................................................ 63

Figure 24: High performance liquid chromatography system (1 Column, 2 Eluent

containers. 3. Auto sampler, sample tray and degasser, 4 Pump, 5 UV-VIS

Detector, 6 Controller, 7 Computer) .................................................................... 65

Figure 25: Liquid chromatography-mass spectrometry system (1, Computer, 2 Pump

and degasser, 3 Sample injector, 4 Eluent container, 5 Controller, 6 UV-PDA

detector, 7 Column chamber, 8 LCMS -2020) ..................................................... 66

Figure 26: Variation of MLSS and MLVSS concentration throughout the operation

period before adding PAC into MBR. ―S‖ and ―T‖ indicate the start-up period and

the point of trace organic contaminants addition, respectively. ............................ 68

Figure 27: Variation of MBR supernatant and permeate turbidity throughout the

operation period. The MBR supernatant was collected after centrifuging the mixed

liquor for 10 min at 1073 x g. ―S‖ and ―T‖ indicate the start-up period and the

point of trace organic contaminants addition, respectively. .................................. 69

Figure 28: Variation in SVI and MLSS concentration of the MBR throughout the

operation period. ―S‖ and ―T‖ indicate the start-up period and the point of trace

organic contaminants addition, respectively......................................................... 70

Figure 29: Variation of SOUR throughout operation period. ―S‖ and ―T‖ indicate the

start-up period and the point of trace organic contaminants addition, respectively.

............................................................................................................................ 71

Figure 30: Variation of ammonium concentration in MBR feed, supernatant and

permeate throughout the operation period. ―S‖ and ―T‖ indicate the start-up period

and the point of trace organic contaminants addition, respectively. ...................... 72

xii

Figure 31: Variation of nitrate (NO3-) concentration in MBR feed, supernatant and

permeate throughout the operation period. ―S‖ and ―T‖ indicate the start-up period

and the point of trace organic contaminants addition, respectively. ...................... 73

Figure 32: TOC concentration in MBR influent, effluent and the removal efficiency of

TOC throughout the operation period. ―I‖, ―S‖ and ―T‖ indicate the period when

the concentration of constituents in synthetic wastewater was kept at elevated

levels (double) temporarily, the start-up period and the point of trace organic

contaminants addition, respectively. .................................................................... 74

Figure 33: TN concentration in MBR influent, effluent and the removal efficiency

throughout the operation period. ―I‖, ―S‖ and ―T‖ indicate the period when the

concentration of constituents in synthetic wastewater was kept at elevated levels

(double) temporarily, the start-up period and the point of trace organic

contaminants addition, respectively. .................................................................... 75

Figure 34: Concentration of the trace organic contaminants in feed and MBR permeate.

Samples in duplicate were taken once a week. Error bars represent standard

deviation of 26 measurements regularly conducted over 13 weeks....................... 77

Figure 35: Removal efficiency of the selected trace organic contaminants and their

corresponding hydrophobicity (log D) by MBR treatment. Samples in duplicate

were taken once a week. Error bars represent standard deviation of 26

measurements regularly conducted over 13 weeks. .............................................. 78

Figure 36: TOC (a) and TN (b) concentrations in GAC effluent, MBR permeate and

feed throughout the operation period ................................................................... 82

Figure 37: Overall removal of trace organic contaminants by MBR-GAC system at 406

BV (a), 4472 BV (b), 9148 BV (c), 18093 BV (d) ............................................... 84

Figure 38: Breakthrough profiles of six biologically persistent and hydrophilic trace

organic compounds as a function of bed volume (BV) ......................................... 89

Figure 39: Relationship between breakthrough (%) and adsorption isotherm constants

(qm, Langmuir maximum adsorption capacity (a) ; Kf, Freundlich partitioning

coefficient (b)).(1.Metronidazole, 2.Fenoprop, 3.Ketoprofen, 4.Naproxen,

5.Diclofenac, 6.Carbamazepine). The breakthrough values are defined as

percentage of the effluent concentration over the influent concentration of the same

sampling event. ................................................................................................... 92

xiii

Figure 40: Relationship of adsorption isotherm constants (qm, Langmuir maximum

adsorption capacity; Kf, Freundlich partitioning coefficient) with various individual

parameters (governing adsorption of organics onto activated carbon) for

biologically persistent six hydrophilic trace organics. 1. Metronidazole,

2.Fenoprop, 3.Ketoprofen, 4.Naproxen, 5.Diclofenac, 6.Carbamazepine. Dipole

moment was calculated by molecular modelling Pro software using ―Modified Del

Re‖ method. Aromaticity ratio denotes the ratio of number of aromatic bonds to

total number of bonds in a molecule. ................................................................... 93

Figure 41: Variation of MLSS and MLVSS concentration in the reactor throughout the

operation period. ―T‖ indicates the point of trace organic contaminants addition,

and ―R‖ indicates the point of sludge withdrawal, while ―P1‖ and ―P2‖ indicate

points of PAC addition to achieve final PAC concentrations of 0.1 g/L and 0.5 g/L,

respectively. ........................................................................................................ 97

Figure 42: Variation of SVI and reactor supernatant turbidity throughout the operation

period. ―T‖ indicates the point of trace organic contaminants addition, while ―P1‖

and ―P2‖ indicate points of PAC addition to achieve final PAC concentrations of

0.1 g/L and 0.5 g/L, respectively. The MBR supernatant was collected in two

different ways i.e., by centrifuging (10 min at 1073 x g), and by gravity settling (30

min), respectively. ............................................................................................. 100

Figure 43: Variation of SOUR and DO concentration throughout the operation period.

―T‖ indicates the point of trace organic contaminants addition, while ―P1‖ and ―P2‖

indicate points of PAC addition to achieve final PAC concentrations of 0.1 g/L and

0.5 g/L, respectively. ......................................................................................... 101

Figure 44: TOC (a) and TN (b) removal efficiency in MBR and PAC - MBR system.

Error bars represent standard deviation of 46, 10, and 15 samples in MBR, MBR –

0.1 g/L PAC and MBR – 0.5 g/L PAC, respectively. ......................................... 104

Figure 45: Variation of (a) ammonium and (b) nitrate concentration in feed, supernatant

and permeate throughout the operation period. ―T‖ indicates the point of trace

organic contaminants addition while, ―P1‖ and ―P2‖ indicate points of PAC addition

achieve final PAC concentrations of 0.1 g/L and 0.5 g/L, respectively. .............. 106

Figure 46: Variation of transmembrane pressure (TMP) as a function of operation time.

―T‖ indicates the point of trace organic contaminants addition while ―P1‖ and ―P2‖

xiv

indicate the point of PAC addition to achieve final PAC concentrations of 0.1 g/L

and 0.5 g/L, respectively. .................................................................................. 109

Figure 47: Fouled membrane in both (a) MBR and (b) PAC – MBR systems. Pictures

were taken on day 186 and 306, respectively. .................................................... 110

Figure 48: Overall removal efficiency of trace organic compounds in PAC - MBR

hybrid system after addition of PAC at a concentration of 0.1 g/L. .................... 112

Figure 49: Removal of six biologically persistent hydrophilic trace organic compounds

as a function of operation time at 0.1 g PAC/L and 0.5 g PAC/L concentrations.115

Figure 50: Breakthrough profile of six biologically persistent hydrophilic trace organic

compounds as a function of operation time. The breakthrough values are defined as


sampling event. ................................................................................................. 116

xv

LIST OF TABLES

Table 1: Sources of PhACs (adapted from [61, 62]) .................................................... 11

Table 2: Information on the adverse effects of trace organics from recent studies

(adapted from [61]). ............................................................................................ 14

Table 3: Typical concentrations in various aquatic environment and information on the

removal efficiency of selected trace organic contaminants by MBR from recent

studies ................................................................................................................. 21

Table 4: Experimental timetable ................................................................................. 34

Table 5: Physicochemical properties of trace organics used in this study .................... 35

Table 6: Characteristic properties of PAC 1000 and GAC 1200 .................................. 41

Table 7: Gradient eluent profiles used in HPLC-UV analyses ..................................... 64

Table 8: GAC adsorption isotherm constants for six biologically persistent hydrophilic

trace organic compounds ..................................................................................... 85

Table 9: Information on some parameters in MBR and PAC – MBR systems (average ±

standard deviation) ............................................................................................ 102

Table 10: Comparison of the effectiveness between MBR - GAC and PAC - MBR

systems ............................................................................................................. 117

Table 11: Cost analysis for GAC and PAC usage. .................................................... 118

Table 12: TOC and TN concentration in MBR feed and permeate before adding trace

organics into the MBR. ..................................................................................... 144

Table 13: TOC and TN concentration in MBR feed and permeate after adding trace

organics............................................................................................................. 145

Table 14: Trace organics concentration and removal efficiency by MBR - GAC

treatment. .......................................................................................................... 147

Table 15: Trace organics concentration and removal efficiency by PAC - MBR

treatment with 0.1 g PAC /L concentration. ....................................................... 160

Table 16: Trace organics concentration and removal efficiency by PAC - MBR

treatment with 0.5 g PAC /L concentration. ....................................................... 165

xvi

LIST OF ABBREVIATIONS

AC Activated carbon

BAC Biologically activated carbon

BV Bed volume

CAS Conventional activated sludge

COD Chemical oxygen demand

DO Dissolved oxygen

GAC Granular activated carbon

GC-MS Gas chromatography- mass spectrometry

EBCT Empty bed contact time

EDCs Endocrine disrupting chemicals

EDG Electron donating group

EPS Extracellular polymeric substances

EWG Electron withdrawing group

HPLC High performance liquid chromatography

HRT Hydraulic retention time

LC-MS Liquid chromatography- mass spectrometry

MBR Membrane bioreactor

MLNVSS Mixed liquor non-volatile suspended solids

MLSS Mixed liquor suspended solids

MLVSS Mixed liquor volatile suspended solids

MWCO Molecular weight cut off

NF Nanofiltration

NPOC Non purgeable organic carbon

OUR Oxygen uptake rate

PAC Powdered activated carbon

PACT Powdered activated carbon treatment

PhACs Pharmaceutically active compounds

RO Reverse osmosis

SMP Soluble microbial products

SPE Solid phase extraction

SOUR Specific oxygen uptake rate

xvii

SRT Sludge retention time

SVI Sludge volume index

TMP Transmembrane pressure

TN Total nitrogen

TOC Total organic compounds

WWTPs Wastewater treatment plants

xviii

LIST OF SYMBOLS

1/n Freundlich exponential coefficient

b Langmuir’s constant (L/mg)

Ce Equilibrium concentration of compound in liquid (mg/L)

Kf Freundlich partitioning coefficient (mg/g)/(mg/L)1/n

H Height

L Length

qe Equilibrium mass of compound adsorbed on unit mass of adsorbent (mg/g)

qm Amount of adsorbate adsorbed per gram of adsorbent (mg/g)

qmb Adsorbent adsorbate relative affinity (L/g)

V Volume

W Width

Chapter 1 Introduction

1

CHAPTER 1: INTRODUCTION

1.1 Background of the study

1.1.1 Trace organics in wastewater: sources and problems

With recent development in analytical chemistry, a number of organic contaminants

have been reported at trace levels (from a few ng/L to several µg/L) in the aquatic

environment. Depending on their usage and characteristics, they can be divided into

several different groups such as pesticides, pharmaceutically active compounds

(PhACs) and endocrine disrupting chemicals (EDCs). Trace organics can be of both

natural and anthropogenic origin. Estrogenic hormones (e.g., estrone and 17β-estradiol

[1]) and phytoestrogens (e.g., isoflavones and lignans) are examples of natural trace

organics, which are released into the environment by humans, vertebrate animals and

certain plant species [2]. Examples of anthropogenic trace organics are synthetic

hormones, industrial chemicals, pharmaceutical and pesticides.

Trace organic contaminants can enter the environment via several different pathways.

For example, they can originate from chemicals directly applied to control waterborne

diseases and pest control (such as pesticides and antibiotics used in husbandry,

aquaculture and other agricultural activities) [3]. A major source of these trace organic

contaminants is sewage treatment plant effluent. Some trace organics can be highly

persistent, and thus they are likely to accumulate in the aquatic environment. With

continuous introduction of new consumer products in our modern days, an alarming

increase in the number of anthropogenic trace organics detected in natural water bodies

has been observed [4].

There is no doubt that various chemicals have contributed many benefits to human life

by increasing both industrial and agricultural activities, treating and preventing many

diseases. For example, atrazine, a well-know pesticide is used to stop pre- and post-

emergence broadleaf and grassy weeds in major crops [5]. The compound is both

effective and inexpensive. Atrazine is the most widely used herbicide in conservation

tillage systems, which are designed to prevent soil erosion. Another example is

bisphenol A, which is used primarily to make plastics, and products containing

bisphenol A-based plastics have been in commercial use since 1957 [6]. At least

4 million tons of bisphenol A are used by manufacturers yearly [6]. However, they also


2

present significant adverse effects to human health and the environment. For example,

bisphenol A is an EDC, which can mimic the hormones of vertebrates (including human

beings) and can lead to adverse health effects. Recent studies have shown that

compounds like estrone, 17β-estradiol and 17α-ethinylestradiol have high specific

biological estrogenic activity even at very low concentrations (several ng/L or less) [7].

Some hormones (e.g., natural hormones (estrone and 17β-estradiol), synthetic hormones

(ethinylestradiol), and phytoestrogens (isoflavoniods) have been also found to possess

endocrine disrupting effects [1, 8, 9]. These chemicals can interfere with the normal

function of the hormone system, for example, they can cause reduction of fish fertility

[3]. Some of these compounds (e.g., estriol and estrone) have been linked to human

cancers [9-11]. Accordingly the removal of these compounds during wastewater

treatment is of great importance to protect the environment and provide safe drinking

water.

1.1.2 Trace organic removal by membrane bioreactors

Trace organics have been detected in water supplies and wastewater effluents around

the world [12-16]. Several studies conducted on selected groups of trace organics have

indicated that coagulation, sedimentation, and conventional filtration achieve negligible

removal efficiency of these compounds [17-19]. The CAS process that is used for

treating sewage can remove bulk organic matter and suspended solids; however their

capacity for removing trace organic contaminants is limited. The removal capacity of

CAS depends significantly on the biological treatment stage where trace organics are

removed by adsorption on suspended solids and biodegradation. Removal of some

hydrophobic compounds has been reported to be positively correlated to sludge

retention time (SRT). Wick et al. [20] confirmed that no significant removal of

pharmaceuticals (i.e. carbamazepine and diclofenac) was observed in the CAS with an

hydraulic retention time (HRT) and SRT of one day and 0.5 day, respectively.

Incomplete removal of pharmaceuticals such as naproxen, ketoprofen and diclofenac

during CAS has also been reported by Kimura et al. [21].

Technical innovations and significant cost reductions of membranes have led to the

establishment of the MBR technology as an alternative to the CAS treatment process.

MBR can potentially achieve higher removal efficiency of some trace organics in

comparison to CAS (e.g., nonylphenol and nonylphenol ethoxylates [22] and several


3

acidic pharmaceuticals (naproxen and ketoprofen) [23, 24]). The membrane in an MBR

replaces the sedimentation tank in a CAS allowing for the uncoupling between HRT and

SRT. MBR systems can be operated at a long sludge age. In an MBR hydrophobic trace

organic compounds can adsorb to mixed liquor suspended solids (MLSS), which can

subsequently facilitate biodegradation of slowly biodegradable compounds such as

some pharmaceuticals under long SRT. Indeed, evidence from some studies has

demonstrated that MBR technology can offer enhanced removal efficiency for

moderately biodegradable compounds [24, 25]. The effect of SRT has been revealed in

a few studies. An MBR operated under an SRT of 65 days was reported to demonstrate

better removal of ketoprofen and diclofenac than an MBR operated under an SRT of 15

days [21]. However, previous studies have reported incomplete and low removal of

some compounds (i.e. carbamazepine, diclofenac and fenoprop) by MBRs which were

operated at an SRT of 70 days or more [26-28].

1.1.3 Adsorption of trace organic on activated carbon

Adsorption using either powdered activated carbon (PAC) or granular activated carbon

(GAC) is a well-know process for removing natural or synthetic organic compounds

such as pesticides in drinking water treatment [29-31]. Recently, several studies have

evaluated the adsorption of other emerging trace organics on activated carbon using

both laboratory and full-scale drinking water treatment systems [19, 32]. In comparison

to the investigations involving drinking water treatment, only a handful of studies have

investigated GAC adsorption as an option for tertiary treatment of conventional

biologically treated wastewater [10, 33, 34]. However, the adsorption of trace organics

on activated carbon decreases due to competition with bulk organic matter for

adsorptive sites [29, 35]. In fact, competition with bulk organic matter for adsorptive

sites has important implications to the lifetime and serviceability of GAC columns. For

efficient adsorption of trace organics, it is usually recommended that the feed to GAC

column be substantially free from bulk organics. Because MBR can produce suspended

solids-free permeate with low total organic carbon content [36], under less competition

from the bulk organic matter, GAC may specifically target the residual trace organics.

Therefore, subsequent GAC treatment of the MBR permeate may result in a better final

effluent quality. PAC can be directly added into MBR to form a hybrid process.

Simultaneous application of PAC within MBR has been mainly studied in relation to


4

membrane fouling mitigation [37, 38], performance improvement of MBR system [38-

40] and removal of some recalcitrant pollutant such as dyes [41]. The adsorption of

trace organics on to sludge facilitates their removal in the biological processes [42];

therefore, a solution to increase the biodegradation of slowly biodegradable compounds

may be the addition of adsorbent into bioreactor. As such, direct addition of PAC into

MBR may lead to significant increase in retention of soluble trace organics. Due to the

complete retention of sludge by membrane and application of longer SRT within MBR,

it is hypothesized here that the retained trace organics could be efficiently removed by

the PAC amended MBR.

1.2 Statement of the problem

The growing pressures from a recent trend towards indirect potable water reuse and the

increasingly stringent water quality regulations have challenged the conventional

wastewater treatment processes. MBR technologies have widely demonstrated superior

performance over CAS in term of basic effluent quality parameters. However, for the

removal of trace organic contaminants, previous studies on MBR have indicated

significant variation ranging from near complete removal for some compounds (e.g.

ibuprofen) to almost no removal for several others (e.g. carbamazepine and diclofenac)

[26, 27, 43]. The elimination of trace organics by MBR is only partially successful and

hence, trace organic contaminants are discharged and accumulated in the environment.

Therefore, post-treatment of MBR permeate or application of hybrid MBR processes

appears to be a logical means to prevent trace organics dispersion in the environment

via incompletely treated wastewater.

Sequential application of GAC adsorption following MBR treatment may result in

complementary advantages. Because MBR can produce high quality effluent with

virtually no suspended solids and with very low total organic carbon content [36], GAC

adsorption is expected to specifically target the residual trace organics in MBR

permeate without any significant interference from the bulk organics. However, to date,

there has been no extensive study on the efficiency of the sequential combination of

MBR and GAC processes for the removal of trace organic contaminants.


5

Simultaneous application of PAC within MBR has been explored in a few studies for

the removal of trace organic contaminants [44-46]. Zhang et al. [44] reported an

improved removal efficiency of carbamazepine in an PAC - MBR hybrid system. Li et

al. [45] observed an enhanced removal of two trace organic compounds, namely,

sulfamethoxazole and carbamazepine. However, a comprehensive understanding of the

involved phenomena is yet to be developed.

1.3 Objectives of the research

This project aims to investigate and demonstrate the complementarities between MBR

treatment and activated carbon (GAC and PAC) adsorption process for an enhanced

removal of trace organic contaminants.

The specific objectives are to

1. Evaluate the removal efficiency of a set of 22 trace organics by MBR

2. Evaluate and compare the removal of trace organics by sequential and

simultaneous applications of activated carbon and MBR.

3. Determine the break through profile of trace organics in a GAC column used for

the post-treatment of MBR permeate over an extended operation.

4. Elucidate the effect of PAC addition within MBR on removal of trace organics

and permeate flux.

1.4 Expected outcomes

Development of a hybrid activated carbon – MBR process achieving enhanced removal

of trace organic contaminants is the main expected outcome of this study. The

assessment of adsorption capacity of the trace organics on activated carbon will allow

for the evaluation of the treatment capacity of the hybrid activated carbon - MBR

systems. Moreover, systematic analysis of the dynamics of breakthrough of trace

organics through a fixed bed GAC column can be used to assess adsorption mechanism

and determine the period of replacement/regeneration and withdrawal/replenishment of

GAC inside the column and PAC in MBR, respectively. A comprehensive comparison

between MBR - GAC and PAC - MBR processes also can be used to select the

treatment process for treating trace organic contaminants.


6

1.5 Thesis outline

This thesis contains seven chapters as schematically presented in Figure 1. Chapter 1

introduces the background of this study. Chapter 2 provides a comprehensive literature

review. Chapter 3 describes the methodology used to achieve the aims and objectives

stated in introduction. The results of the experiment along with their detailed discussion

will be reported in chapters 4, 5, and 6. Finally, the conclusions and recommendations

for future research are provided in chapter 7.

Figure 1: Schematic description of the thesis structure.

Chapter 1: Introduction

Chapter 2: Literature review

Chapter 3: Methodology

Results and discussion

Chapter 4:

Performance of the

MBR

Chapter 5:

MBR followed by

GAC post - treatment

Chapter 6:

Combined PAC -

MBR

Chapter 7: Conclusions and Recommendations

Chapter 2 Literature review

7

CHAPTER 2: LITERATURE REVIEW

2.1 Introduction

The occurrence of trace organics such as pesticides, PhACs, natural and synthetic

hormones and various industrial compounds in the aquatic environment is of great

concern due to their potential adverse effects on human and ecological health [16]. This

chapter provides an overview of the current scientific research on the groups, sources,

occurrences and fate of emerging trace organic contaminants. A comprehensive

literature review on the basic principles of MBR technology, the performance of MBRs

in trace organics removal and associated governing factors, and the application of

activated carbon in removing emerging trace organic contaminants will be provided in

this chapter.

2.2 Trace organic contaminants

2.2.1 Groups of trace organic contaminants

Trace organic contaminants in wastewater can be divided into several different groups

depending on their intended uses such as pesticides, PhACs, surfactants and other

industrial chemicals, and steroid hormones. Most of them are of anthropogenic origin.

These trace organics also contain natural compounds which are excreted by humans,

animals and certain plant species. It is noteworthy that the categorisation here is not

complete. Compounds can be categorised based on the mode in which they may affect

human and aquatic biota. For example, endocrine disrupting chemicals were defined by

the US Environmental Protection Agency as ―an exogenous agent that interferes with

synthesis, secretion, transport metabolism, binding action or elimination of natural

blood-borne hormones that are present in the body and are responsible for homeostasis

reproduction and developmental process‖ [47]. EDCs consist of a vast number of

synthetic hormones (e.g., estrone and 17β-estradiol) and natural organics (e.g., 17 α-

estradiol) as well as inorganic chemicals (e.g., arsenic, cadmium, lead and mercury).

These compounds have a wide range of chemical structures but all of them have the

capacity of disrupting normal hormonal actions. In some cases they bind to steroid

hormone receptors and can have weak estrogenic or androgenic effects while others

disrupt thyroid hormones or other physiological functions [9]. Consequently, they may


8

disrupt reproductive or immune functions and can be carcinogenic. Detailed information

regarding various groups of trace organics is presented below.

2.2.1.1 Pharmaceutically activate compounds

Pharmaceuticals have been detected in water supplies and wastewater treatment plant

effluents around the world [12, 48]. The occurrence of pharmaceuticals and personal

care products (PPCPs) in the aquatic environment is an emerging concern because toxic

effects of these compounds may be observed even at very low concentrations [49-51].

PhACs are produced and used in very large volumes and their use and diversity is

increasing every year as new products are introduced. There are various

pharmaceuticals in different therapeutic groups and diverse physicochemical properties.

They are developed with the intention of performing a biological effect. Thus they have

many of the necessary properties to bio accumulate and provoke effects in the aquatic or

terrestrial ecosystems [52]. After having an internal curing effect in the human body,

pharmaceuticals will be excreted through urine or faeces as a mixture of metabolites, as

unchanged substance or conjugated with an inactivating compound attached to the

molecule mixture of metabolites depending on the pharmacology of the compounds

[52]. In this study, varieties of compounds representing a large group of PhACs were

selected. The selected compounds included analgesics and anti-inflammatory drugs such

as ibuprofen, ketoprofen, naproxen and diclofenac, cholesterol-lowering drugs

(gemfibrozil), and antiepileptic drug (carbamazepine). The physicochemical properties

of the selected compounds are shown in Table 5.

2.2.1.2 Pesticides

Pesticides are substances or mixture of substances intended for preventing, destroying,

repelling or mitigating any pest. Pesticides are categorised into four groups: pesticides,

fungicides, herbicides, and insecticides. The increased use of agricultural pesticides has

led to many benefits, for example, improved productivity and reduced maintenance

costs [5]. However, uncontrolled use of pesticides causes environmental contamination.

Because they can potentially accumulate in the food chain, pesticides constitute the

major source of potential environmental hazards to human and animal [5, 53]. The

usage and production of persistent pesticides have decreased in last two decades

because of extreme environmental hazards [5]. The current pesticides are less persistent


9

and harmful than before. However, harmful pesticides are still abundantly present in

polluted sites due to widespread and indiscriminate use in the past. In this study, two

pesticides namely, fenoprop and pentachlorophenol were used. Fenoprop is an herbicide

and a plant growth regulator while pentachlorophenol is an organochlorine compound

used as a pesticide and a disinfectant. Pentachlorophenol is used in preservation of

agricultural seeds (for non-food uses), leather, and wood. Its use has significantly

declined due to the high toxicity and persistence.

2.2.1.3 Surfactants and industrial compounds

Compounds selected in this study under this category include the well-known

industrial chemical bisphenol A, which is a monomer used in the production of epoxy

resins and of most common form of polycarbonate plastics which are used to make a

variety of common products including water bottles, sport equipments, medical and

dental devices, dental fillings, sealants, eyeglass lenses, CDs, DVDs, and household

electronics. However, bisphenol A is toxic for aquatic and terrestrial organisms

probably as a result of its interaction with proteins [54]. Accordingly bisphenol A has

been classified as an EDC by several organizations [55]. Three other organic

compounds of the alkyl-phenol group, namely, 4-tert-butyphenol, 4-n-nonylphenol and

4-tert-octylphenol were also selected in this study. These compounds have been

widely used as industrial surfactants and have been frequently detected in wastewater

and in some fresh water bodies.

2.2.1.4 Natural and synthetic hormones

Recently, a variety of natural and synthetic hormones, have been detected in the aquatic

environment. Although the full extent of the impact of natural and synthetic hormones

on human health is still a subject of intense scientific debate [56, 57], some of these

compounds have been shown to cause adverse effects on a range of aquatic organisms

in the concentration range of 0.1 to 0.5 ng/L [58]. For example, 17β-estradiol and 17α-

ethynylestradiol have been identified to cause adverse developmental and reproduction

issues in fish exposed to municipal wastewater effluent [59, 60]. These compounds act

as endocrine disruptors. Therefore, their occurrence, fate and effects are of heightened

interest. In the view of their presence in aquatic environment, several natural hormones


10

(i.e., estrone, estriol, 17-β-estradiol and 17-β-estradiol-acetate) and a synthetic hormone

(i.e., 17-α-ethinylestradiol) were selected in this study.

2.2.2 Sources of trace organic contaminants

As mentioned in previous section, trace organic contaminants can be categorised into

different groups based on their intended uses. As such, the sources of trace organic

contaminants may correlate to where they are applied. Several routes of trace organic

contamination of natural water bodies can be identified. The current and future amounts

of the micropollutants may be estimated based on the amount of chemical used, for

example, in agricultural and industrial practices and for treatment and prevention of

diseases.

A huge amount of active pharmaceutical ingredients are produced each year and applied

in human and veterinary medicine. The worldwide annual per capita consumption of

pharmaceuticals is 15 g [61]. The annual pharmaceutical consumption by individuals in

developed countries is three to ten times higher than the world average. After being

administered into the host body the pharmaceuticals undergo a metabolic transformation

process. Significant fractions of the compounds are excreted into raw sewage and

wastewater treatment systems. Conventional wastewater treatment plants (WWTPs) are

not designed to treat these compounds. Effluents are discharged to the water bodies or

reused for irrigation and biosolids produced are used in agriculture. Due to partial

metabolisation and excretion from human body followed by incomplete removal in

WWTPs, WWTPs effluents are considered to be the main source of trace organics into

the environment. In addition, improper disposal of unused or expired drugs and

pharmaceuticals residues from spill accidents are significant sources of trace organic

contaminants [62]. Furthermore, direct release of veterinary pharmaceuticals in the

environment may occur via application in aquaculture (fish farming). Pharmaceuticals

may also be indirectly released by way of topical treatment and mostly via run off and

leaching from agricultural fields and livestock wastes [62].


11

Table 1: Sources of PhACs (adapted from [61, 62])

Source Mode of exposure to environment

Hospital Discharge of wastes and expired drugs

Animal husbandries Hormones and drugs injected to poultry

and cattle

Aquacultures Hormones fed to fish, antibiotics are also

added to feed and water

Household discharge Discharge of expired and consumed drugs

from leaky sewers and septic systems

Companies manufacturing drugs Industrial waste containing drugs, storm

runoff carrying powdered drugs

Wastewater and sewage treatment plant Residuals from wastes and sewage

containing drugs and hormones

The widespread use and indiscriminate disposal of pesticides by farmers, institutions

and the general public provide many possible sources of pesticides in the environment

[5]. Following release into the environment, pesticides may have many different fates.

Pesticides which are sprayed in agricultural activities may move away from the target

sites and may end up in the air or other parts of the environment, such as in soil or

water. Pesticides which are applied directly to the soil may be washed off the soil into

nearby bodies of surface water or may percolate through the soil to lower soil layers and

groundwater. The application of pesticides directly to bodies of water for weed control,

or indirectly as a result of leaching from boat paint, runoff from soil or other routes,

may lead not only to build up of pesticides in water, but also may contribute to air levels

through evaporation.

Surfactants and industrial chemicals enter into the aquatic environment due to their

presence in wash water, as waste or by products of production processes or simply as a


12

result of normal use and disposal. After their application, they are usually discharged

into municipal sewer systems and afterwards treated in WWTPs, where they are

completely or partially removed by a combination of sorption and biodegradation [63,

64] and release into the environment via WWTPs effluent.

The main sources of steroid estrogens are the human population and livestock. Estrogen

excretion by humans and animals varies as a function of their sex, physiological and

developmental state [65]. Humans excrete a large quantity of estrone (E1), 17-β-

estradiol (E2), and estriol (E3) daily in their glucuronide and sulfate-conjugated forms,

mainly via urine (95%) [66]. For therapeutic purposes, the daily synthetic hormone

intake, for example, 17-α-ethinylestradiol (EE2) is around 20–60 μg for contraception

and about 10 μg to control menopausal disorders; from such ingested dosage, around 30

– 90% is excreted in urine and feces [67]. Hence, the total amount of excreted estrogens

discharged by humans into the environment has been estimated at some 4.4

kg/year/million inhabitants [68].

2.2.3 The effects of trace organic contaminants on human health and environment

The potential effects of trace organic contaminants have been well documented in

various studies since the last decade [69-71]. These compounds can disrupt endocrine

system by mimicking, blocking or also hampering functions of hormones, thereby

affecting health of human and animal species [70]. Schqaiger et at. [69] studied the

possible effects in rainbow trout after prolonged exposure to diclofenac. They reported

histopathological changes of kidney and liver when fishes were exposed to 5 µg/L of

diclofenac for 28 days. EDCs cause a wide range of adverse effects on aquatic organisms

e.g., feminisation of male fishes [72], demasculinisation of alligators [73], growth

inhibition, immobilisation, mutagenicity, increased mortality and changes in population

density [74, 75]. For example, bisphenol A has been proven to have estrogenic effects in

rats [76]. BPA has been shown to mimic estradiol in causing direct damage to the DNA

of cultured human breast cancer cells [77]. Some steroid hormones such as estrone, 17β -

estradiol, and 17 α - ethinylestradiol have a high specific biological estrogenic activity

even at extremely low concentrations [70] and may cause feminisation in male fish.

Table 2 summarises information regarding the adverse effects of trace organics from

recent studies. In the environment trace organics are present as a mixture of various


13

parent compounds and their transformation products. Mixture of trace organic

compounds may impose a more complicated effect when compared to that of single

compound [78-80] for example, ecotoxicity tests with antibiotics showed that combined

toxicity of two antibiotics can lead to either synergistic antagonistic or additive effects

[81]. In general, knowledge about the toxicity of compound mixtures is limited. This is a

new field of ecotoxicity and much remains to be studied.


14

Table 2: Information on the adverse effects of trace organics from recent studies (adapted from [61]).

No of

compounds

studied

Compounds causing risks:

concentration of exposure (range of

dose at which the risk was observed)

Type of risks involved Reference and

country

1 Diclofenac: 0.5 -50 µg/ L Affect tissues of gills and kidney of freshwater fish

brown trout

[82]

Germany

27

Ibuprofen, diclofenac, 17-β - estradiol and

17-β estradiol – 17 acetate:

0.01 µg/ L

Risk to aquatic environment with chronic toxic effect

(such as inhibited polyp regeneration and reduced

reproduction in hydra)

[71]

Sweden

13

Mixture of atenolol, bezafibrate,

carbamazepine, cyclophosphamide,

ciprofloxacin, ibuprofen, lincomycin,

ofloxacin, ranitidine, salbutamol and

sulfamethoxazole: 10 -1000 ng/L

Inhibit the growth of human embryonic kidney cells

HEK293 with the highest effect observed as a 30%

decrease in cell proliferation compared to control [83]

Italy

10

Diltiazem, acetaminophen and

sulfamethoxazole: 8.2 – 271.3 µg/L

Hazard quotient >1, diltiazem: most toxic ( lethal conc.

8.2 mg/L for freshwater invertebrate Daphnia magna

[84]

South Korea


15

4

Ethinylestradiol, zearalonol, 17 β

trenbolone and melengestrol acetate < 1-

68 ng

Freshwater fish fathead minnows experience different

levels of hepatic gene expression [85]

USA

1

17 α-ethinylestradiol (EE2): 5- 50 ng/L Brain and inter-renal steroidogenic acute regulatory

protein and cytochrome P-450 mediated cholesterol

side chain cleavage expressions of juvenile salmon

were modulated with time and concentration

[86]

Norway

3

Chloramphenicol, florfenicol, and

thiamphenicol (veterinary and

aquaculture): 1.3 – 158 mg/L

Inhibit the growth of Chlorella pyrenoidosa

(freshwater) Isochrysis galbana and Tetraselmis chui

(marine)

[87]

Taiwan


16

2.2.4 Fate and behaviour of trace organic contaminants

The removal of trace organic contaminants depend on the treatment process applied

(CAS, MBR and nanofiltration/reverse osmosis membrane filtration (NF/RO)) [7, 88].

In biological processes, the operating parameters that have profound influence on

removal of trace organics include operating temperature [43, 89, 90], HRT and SRT

[91, 92], mixed liquor pH and dissolved oxygen concentration [93, 94]. Detailed

information regarding trace organics removal by MBR can be found in section 2.3.2.2.

This section will focus on the extent of removal by CAS.

Elimination of trace organics in CAS treatment processes is often incomplete, and the

reported overall removal of trace organics in CAS varies [95, 96]. As a consequence, a

significant fraction of the trace organics is discharged with the final effluent into the

aquatic environment. Two major mechanisms of removal of trace organics during CAS

processes are sorption and biodegradation [97]. Higher removal efficiency of some

trace organic compounds has been attributed to their adsorption to the activated sludge

[98]. Trace organics which are relatively hydrophilic show limited sorption to sludge

[88]. However, some very hydrophilic compounds such as fluoroquinolone antibiotics

may mainly be eliminated by sorption to sludge by electrostatic interactions with the

cell membranes of the microorganisms [99, 100]. Therefore, the physical and chemical

properties of these compounds can greatly influence their fate and behaviour as well as

the removal efficiency of trace organic contaminants during CAS treatment. Most of the

studies report the removal of trace organics compound from the aqueous phase by

comparing influent and effluent concentrations, without distinguishing between the

three major fates of a substance in CAS; (i) degradation to low molecular weight

compounds, (ii) physical adsorption onto activated sludge and (iii) hydrolysis of

conjugates yielding the parent compound [101].

2.2.5 Analysis of trace organic contaminants

Trace organic contaminants represent structurally diverse classes of compounds and

different analytical methods have been applied for the identification and quantification

of these chemicals in water. The measurement of trace organics in water most

commonly consists of extraction of the chemicals from water, concentration of the

resulting extract, chromatographic separation and detection [102]. Most of trace


17

organics have been found in environment at sub - or µg/L concentrations [12]. An

extraction step is required to concentrate the target compounds to a detectable level.

After extraction, the extract is dried by passing nitrogen through a solid phase extraction

cartridge. In some cases the extract is concentrated further by evaporation with a gentle

stream of nitrogen. [103, 104].

Analytical procedures for the determination of trace organics in aqueous samples can

utilise either gas or liquid chromatography after extraction and clean up procedures. Gas

chromatography (GC) has high resolution, and sensitivity. However, GC needs the use

of volatile derivatives, which is labour intensive and can reduce analyte recovery [105].

On the other hand, high performance liquid chromatography (HPLC) is capable of the

analysis of non-volatile compounds. In addition, this technique provides a shorter

analysis time and less yield loss than the GC technique. The combination of GC and

mass spectrometry (MS) forms a powerful combination for simultaneous separation and

identification of many organic contaminants in environmental samples [106]. Analytical

methods by using GC-MS for the determination of acidic herbicides and polar

pharmaceutical residues in aqueous solutions have been used widely [106-108]. Several

studies have measured concentrations of residues of organic compounds, including

PhACs and/or EDCs in influents and the treated effluents by using various analytical

methods, e.g., HPLC, LC – MS/MS, GC-MS.

2.3 Membrane bioreactor technology

2.3.1 Definition of MBR

MBRs can be defined as a combination of two basic treatment processes - biological

degradation and membrane separation into a single process where suspended solids and

microorganisms responsible for biodegradation are separated from treated water by a

membrane filtration unit [51]. Although, it has been applied for the treatment of

domestic or industrial wastewater since the late 80s [109]. MBR processes have gained

great popularity in the water industry in recent years. By the turn of the 21st century,

more than 500 full scale MBR plants had been in operation worldwide [23]. In Japan,

over 150 MBRs were installed to different types of industrial wastewater such as food

processing and breweries. In the US, there were about 24 municipal wastewater


18

treatment plants using MBR processes. In Canada, nine MBR installations were in

operation [23]. Similarly, approximately 300 MBR plants for industrial applications and

about 100 municipal MBR wastewater treatment plants were in operation or being

constructed in Europe in 2005 [28]. The global MBR market in 2005 reached a market

value of $217 million in 2005 with a projection for the year 2010 of $360 million. The

application of MBR is expected to increase more dramatically due to more stringent

environmental regulations, growing water reuse and the emergence of low-cost

membrane with lower pressure requirement and higher permeate flux [109].

In comparison to the CAS processes, MBRs have several major advantages including a

smaller footprint, more flexibility for future expansion, scale-up and better effluent

quality in terms of removal of pathogens, suspended solids and nutrients [110-112]. In

addition, sludge separation is not dependent on the influent characteristics or the

flocculation state of the biological suspension as the flocs size is much larger than the

membrane pores [113]. The biomass concentration can also be higher than in CAS (up

to 10 times), resulting in a much more intensive treatment process in comparison to

CAS [114].

MBR is typically categorised into recirculated MBR (external circulation or side-stream

configuration) and submerged MBR based on relative positions of the membrane

module and bioreactor (Figure 2). In a recirculated MBR, the membrane module and the

bioreactor are separated. The mixed liquor is transferred to the membrane module

through a recirculation pump. After the separation process, the concentrated liquid is

recirculated back to the bioreactor. In a submerged membrane bioreactor the membrane

module is submerged inside the bioreactor and filtrated effluent is drawn by vacuum or

siphon. The submerged MBR is a more common configuration for municipal

wastewater treatment since it can significantly reduce power consumption [113]. The

membranes applied in submerged MBRs can be either hollow fiber or flat membrane

module design and multi–tube modules are used for side –stream MBR configuration

[109].


19

Figure 2: Configuration of MBR systems

(a) side-stream MBR configuration, (b) submerged MBR

2.3.2 MBR application for trace organics removal

2.3.2.1 Removal of trace organic contaminants by MBR

MBRs can operate at a biomass concentration of as high as 20 g/L and at a prolonged

SRT. The high sludge concentration in MBR is not only beneficial for biodegradation of

trace organic contaminants but it can also have a beneficial effect on the removal

efficiency of trace organics that can absorb to the sludge. This may promote the

degradation of persistent substances because of the improved adaptation of bacteria for

trace organics.

Considerable research efforts have been devoted to the assessment of trace organics

removal by MBR treatment. The reported data ranges from near complete removal for

some compounds to almost no removal for several others. Excellent MBR removal of

ibuprofen (up to 98%) was confirmed along with naproxen (84%) and erythromycin

(91%) by Reif et al. [115] in their pilot-scale MBR. In addition, sulfamethoxaole and

musk fragrances (galaxolide, tonalide, and celestolide) were moderately removed

(>50%) probably due to partial adsorption on the biomass. On the other hand,

carbamazepine, diazepam, diclofenac, and trimethoprim were poorly removed (<10%)

due to poorer biodegradation. Nghiem et al. [116] also confirmed the possibility of

achieving good treatment of bisphenol A (90%) due to both biodegradation and

adsorption. On the contrary, sulfamethoxazole removal was solely attributed to

Air

Influent

Air

Influent

Recirculated

Activated

sludge Sludge

Effluent

Effluent

Sludge

Activated

sludge

Membrane

(a) (b)


20

biodegradation, which can explain the poorer removal (50%) as this compound is rather

hydrophilic (log D = - 0.22 at pH 7) [116].

MBRs have been widely reported to achieve superior performance over that of CAS in

terms of basic water quality parameters. However, there have been several conflicting

reports on whether MBRs can offer enhanced removal of trace organic contaminants

compared to that achieved by CAS treatment. Cirja et al. [7] noted that the removal

rates differed from one compound to the another, however, no discernible difference

between CAS and MBR could be detected. Oppenheimer et al. [96] reported no

significant difference in removal efficiencies of ibuprofen, triclosan and caffeine by

both CAS and MBR process. Bernhard et al. [117] reported that treatment by MBR

resulted in significantly better removals compared to CAS for poorly biodegradable

compounds such as diclofenac, mecoprop, and sulfophenyl carboxylates which was

attributed to the long sludge retention time in MBR. Radijenovic et al. [118] reported

that the removal of pharmaceuticals in MBRs was superior for several compounds (e.g.,

naproxen, ketoprofen) and at least similar for others (e.g., carbamazepine and

diazepam). Kimura et al. [21] found that compounds with a complex chemical

structure, for example, ketoprofen and naproxen were not eliminated at all in CAS

treatment, but could be eliminated partially by MBRs.


21

Table 3: Typical concentrations in various aquatic environment and information on the

removal efficiency of selected trace organic contaminants by MBR from recent studies

Category Compound Concentration in

environment

(ng/L) References

Removal (%)

(min –

max)

References

Ph

arm

ace

uti

cal

an

d p

erso

nal

care

pro

du

cts

Ibuprofen SE: 780 – 48240

SW: 1300

[14, 15, 119,

120] 70 - 99 [115, 121, 122]

Acetaminophen PE: 80.000 [121] 85- 99 [16, 121, 123]

Naproxen SE: 24

SW: 2600 [14, 30] < 50 [26, 46, 123]

Ketoprofen SW: 180

GW: 611 [14, 124] 50 - 65 [23, 125]

Diclofenac SE: 424

SW: 370 - 990 [14, 15, 126] 0 - 80

[122, 127] [46,

128]

Primidone SE: 2-95

PE: 100 [121, 129] 12.4 – 90 [26] [43, 123]

Carbamazepine

SE: 1594

PE: 230 – 1850

SW: 950

[14, 95, 121] 12 - 68 [94] [46, 128,

130]

Salicylic acid SE: 220

GW: 418 [124, 131] > 90 [43]

Metronidazole Not available < 40 [43]

Gemfibrozil SE: 82 [30] 0 – 95 [30, 43, 98]

Triclosan

SE: 32

PE: 470

GW: 509

[30, 121, 124] 88 - 91 [27, 30]

Pes

tici

des

Fenoprop SW: 4 [132] < 60 [43]

Pentachlorophenol SW: 13000 [133] < 95 [134]


22

Ind

ust

ria

l ch

emic

als

an

d

thei

r m

eta

bo

lite

s

4-tert-butyphenol SW: 50 [135]

80 – 99 [43, 123] 4-tert-octylphenol SW: 18.0– 20.2 [136]

4-n-nonyphenol GW: 23088

SW: 10 - 1400 [18, 124, 137]

Bisphenol A SE:

SW: 1000 [137] > 90 [116] [122]

Ste

roid

ho

rmo

nes

Estrone GW: 9

SW: 2000 [124, 137] > 92 [122]

17-β-estradiol SW: 12000

GW : 31 [124, 137] > 98 [26, 43, 122]

17-β-estradiol-

acetate Not available 80 - 99 [26, 122]

17-α

ethinylestradiol

SW: 2000

PE: 140 [121, 137] 65 – 94 [122] [138]

Estriol SW: 23 - 660 [65] 90 - 99 [122] [43]

SW, PE, GW and SE refer to surface water, primary effluent, ground water and secondary

effluent, respectively.

2.3.2.2 Factors affecting the removal of trace organic contaminants by MBR

Physicochemical properties of trace organics have been reported to significantly govern

their removal efficiency by MBR treatment. Adsorption of trace contaminants on sludge

particles, driven primarily by hydrophobic interaction, appears to be one of the key

mechanisms controlling removal efficiency during MBR treatment. Hydrophobic

compounds (log D > 3.2) adsorbed on sludge can be retained by membrane and further

biodegradation by biomass in the reactor can occur. For instance, the removal efficiency

of the significantly hydrophobic compounds steroid hormones and alkyl phenolic

compounds have been consistently reported to be 95 – 99% [27]. Tadkaew et al. [26]

investigated the removal of 40 trace organics with different molecular weight ranging

from 151 g/mol to 455 g/mol by the MBR treatment. The results showed that

compounds with molecular weight of more than 300 g/mol were relatively well

removed, while the removal of those with molecular weight below 300 g/mol varied

from almost no removal to more than 95% removal. However, it was noted that the


23

compounds with molecular weight above 300 g/mol also possessed higher

hydrophobicity.

For hydrophilic compounds (log D < 3.2) sorption is no longer a dominating removal

mechanism and the removal of these compounds is much more strongly influenced by

their intrinsic biodegradability [26]. In this context, the presence of specific functional

groups in trace organic compound structures have been reported to influence the

removal efficiency by the MBR treatment [24, 26, 139]. Tadkaew et al. [26]

systematically demonstrated that compounds with strong electron withdrawing group

(EWG) (e.g., halogen, amide and carboxyl) are more resistant to MBR treatment, while

the removal of compounds possessing both electron donating group (EDG) (e.g.,

hydroxyl, amine, and methyl) and EWG can substantially vary depending on the

number and type of the functional groups. Cirja et al. [7] also reported that the removal

rates of xenobiotics by MBR are related to the physicochemical characteristics of the

compounds. Kimura et al. [24] reported that removal efficiencies of the studied PhACs

(clofibric acid, diclofenac, ibuprofen, mefenamic acid and naproxen) were found to be

dependent on their molecular structure such as number of aromatic rings or inclusion of

chlorine (i.e., chlorine group compounds (clofibric acid and diclofenac) were not

effectively removed by MBR). The functional group and hydrophobicity of compounds

may also have a combined effect on their removal efficiency; for example, Hai et al.

[140] demonstrated that there was a combined effect of halogen content (weight ratio)

and hydrophobicity on the removal of halogenated trace organic compounds in MBR.

Compounds with high halogen content (>0.3) were well removed (>85%) when they

possessed high hydrophobicity (Log D > 3.2), while those with lower Log D values

were also well removed if they had low halogen content (<0.1).

In addition to the physicochemical properties of trace organics, their removal also

depends on operating conditions such as operating temperature [43, 89, 90], HRT

[141] , SRT [91, 92, 142], mixed liquor pH [122], and dissolved oxygen concentration

[94, 128]. Hai et al. [43] studied the removal of trace organics by MBR under variation

of temperature and reported that while the removal of hydrophobic compounds was

stable at a temperature between 10 oC to 35

oC the removal of hydrophilic compounds

was lower at 10 oC than that at 20

oC. However, at 45

oC the removal of most trace

organics was deteriorated. Concerning SRT, increased SRT values have shown to


24

improve removal for most PPCPs [92], although beyond 25 – 30 days this parameter

appears not significant anymore [92]. Tadkaew et al. [122] investigated the removal of

ionisable and non-ionisable trace organics by MBR treatment under different mixed

liquor pH ranging from 5 to 9. High removal efficiency of the ionisable compounds was

observed at mixed liquor pH 5 while removal efficiency of two non-ionisable (bisphenol

A and carbamazepine) compounds was independent of the mixed liquor pH. Likewise,

Urase et al. [143] found that the higher removal rate of some acidic pharmaceuticals

such as ketoprofen, ibuprofen, clofibric acid, gemfibrozil, fenoprofen, ketoprofen,

naproxen, diclofenac and indomethacin by MBR treatment was observed at lower pH

(pH = 4.3 – 5) operation. On the other hand, the removal of neutral compounds 17-α

ethinylestradiol, carbamazepine, propyphenazone, and benzophenone was not

significantly affected by bioreactor pH.

Only a few studies specifically investigated the effect of different DO concentrations in

the reactor on the removal of trace organics. The reported results revealed not much

difference effect between aerobic and anoxic MBRs in terms of trace organics removal.

For example, Clara et al., [95] and Abegglen et al. [127] reported negligible level of

removal of carbamazepine in different configurations of MBR (sequential anoxic–

aerobic MBR and aerobic MBR, respectively). However, there are some studies, which

have reported better removal under anoxic environment, either in MBR or in batch tests.

Hai et al. [94] reported carbamazepine (a persistent trace organic) to be degraded only

under anoxic environment in their batch tests. In the MBR treatment the removal of

carbamazepine was 68 % and less than 20% under anoxic and aerobic conditions,

respectively [94]. Joss et al. [128], on the other hand, reported that the degradation of

estrone takes place under both anoxic and aerobic conditions, but achieves higher

degradation rate in aerobic conditions (DO = 2 -3 mg/L). Stasinakis et al. [93] reported

better removal of diuron during batch tests under anoxic environment (>95%) in

comparison to that in aerobic condition (60%). Zwiener et al. [144] also showed that

diclofenac was not degraded in short-term biodegradation test under aerobic conditions,

whereas it was degraded under anoxic conditions.


25

2.4 Activated carbon adsorption

2.4.1 Activated carbon

Activated carbon is a form of carbon that has been processed to make it extremely

porous, and thus, to have a very high surface area available for adsorption or chemical

reaction. Owing to its surface properties such as surface area, porosity and surface

chemistry, activated carbon is one of the most effective and widely used adsorbent for

the removal of organics from aqueous solutions. One major advantage of activated

carbon is its ability to efficiently remove a wide variety of toxic organic compounds

[145].

Adsorption is one of the most frequently applied methods for organics removal from

aqueous solution because of its efficiency, capacity and applicability on a large scale

[146]. Both PAC and GAC are commonly used for water and wastewater treatment

applications. A typical activated carbon particle, whether in powdered or granular form,

has a porous structure consisting of network of interconnected macrospores, mesopores

and micropores that provide a good capacity for the adsorption of organic molecules

due to its high surface area. This high surface permits the accumulation of a large

number of contaminant molecules [147]. The recent change in water discharge

standards regarding organic pollutants has placed additional emphasis on using

activated carbon. Adsorption is particularly effective in treating low concentration waste

streams and in meeting stringent treatment levels. Therefore, in the water and

wastewater treatment, activated carbon is expected to become an important tool for

trace organics removal.

2.4.2 Application of activated carbon

It is well known that activated carbon is one of the most effective adsorbents for the

removal of taste, color, and odor causing organic pollutants from aqueous or gaseous

phases. AC is widely applied as a commercial adsorbent in the purification of water and

air [94]. It is also widely used for treatment of taste and odor. Treatment with AC has

proved to be efficient for removal of geosmin and 2-MIB [78]. Zhang et al. [148]

demonstrated that GAC is an excellent adsorbent for two algal odorants dimethyl

trisulfide and β- cyclocitral. AC has been widely studied for treating landfill leachate

wastewater. Foo et al. [128] summarized lists of research on the landfill leachate


26

treatment via activated carbon adsorption process during the last 15 years and reported

that in most cases, activated carbon adsorption has revealed the prominence in removal

of an essential amount of organic compounds from the leachate samples. AC has been

also investigated intensively for treatment of dye wastewater [149-151]. The results

indicated that AC could be employed for efficient removal of dyes from wastewater [41,

149, 152].

PAC and GAC are frequently applied in drinking water treatment for removal of natural

or synthetic organic compounds (SOCs) e.g., pesticides [153]. Recently several studies

have evaluated adsorption of other trace organics (PhACs, EDCs) on activated carbon

both under laboratory conditions and surveys at full- scale drinking water treatment

plants [19, 32]. For example, Hernández-Leal et al. [34] reported complete adsorption of

all studied trace organics (bisphenol-A, benzophenone-3, hexylcinnamic aldehyde, 4-

methylbenzylidene-camphor (4MBC), triclosan, galaxolide, and ethylhexyl

methoxycinnamate) onto PAC in batch tests with milli-Q water spiked with 100 - 1600

µg/ L of trace organics at a PAC dosage of 1.25 g/ L and contact time of 5 minutes.

GAC has a relatively larger particle size compared to PAC and, consequently, presents a

relatively smaller surface area. Nevertheless, GAC has long been used in the removal of

traditional organic contaminants such as pesticides [153]. GAC has, therefore, been

proposed as a potential treatment method to aid in the effective removal of emerging

contaminants, particularly EDCs in wastewater treatment [154]. A significant reduction

in the concentration of steroidal estrogens (43-64%), mebeverine (84-99%) has been

achieved in a full-scale granular activated carbon plant [10]. In a study by Hernández-

Leal et al. [34] , three GAC columns were operated to treat aerobically treated grey

water which was spiked with the above micropollutants in the range of 0.1 - 10 µg/ L at

a flow rate of 0.5 bed volumes (BV)/h. They observed more than 72% removal of all

compounds (bisphenol-A, hexylcinnamic aldehyde, 4-methylbenzylidene-camphor

(4MBC), benzophenone-3 (BP3), triclosan, galaxolide, and ethylhexyl

methoxycinnamate). Tanghe et al. [155] reported that at least 100 mg/ g of nonyphenol

adsorbed on GAC in an adsorption test. A few studies have investigated GAC

adsorption as an option for tertiary treatment of conventional biologically treated

wastewater [10, 156], for example, Grover et al., [10] reported that a full scale GAC

plant could reduce above 60% of steroidal estrogens in sewage effluent.


27

Even though GAC columns demonstrate high initial adsorption capacity, the GAC

media can gradually become exhausted with adsorbed organic pollutants. Choi et al.

[157] reported that the initial high removal efficiency of nonylphenol gradually

decreased with operation time. This is a typical pattern observed with adsorption

systems. Adsorption efficiency steadily decreases as adsorption sites are gradually filled

up over operation time. However, it has been reported that AC can provide support for

microbial growth [144, 158], thus offering the potential of achieving the so called

biologically activated carbon (BAC), where organic contaminants can be removed by

simultaneous adsorption and biosorption. The BAC process can enhance the adsorption

of AC for non- or slowly biodegradable compounds by eliminating these compounds

that would otherwise compete for adsorptive sites. This concept has been demonstrated

in the literature [157, 159, 160]. Choi et al. [157] reported that used GAC, which had

already been used to adsorb amitrol, showed better performance of amitrol removal

than that of virgin GAC. The results suggested that perhaps biological degradation was

involved in amitrol removal and the microbes accustomed to amitrol was present in the

used GAC, which led to enhanced removal of the compound during the subsequent

application of that GAC .

2.4.3 Application of activated carbon with membrane bioreactor

Over the last decade, the tightening of water quality regulations and the increased

attention given to trace organic contaminants has been favouring the emergence of

alternative treatment technologies in order to completely eliminate trace organic

contaminants. In this connection, the concept of combined processes such as coupling of

MBR with NF/RO, MBR with ozonation, MBR with UV irradiation and MBR with

PAC/GAC has been tested. The idea of application of activated carbon adsorption in

conjunction with an MBR has given rise to two modes of its application: i) direct

addition of activated carbon (mainly PAC) into MBR, and ii) post-treatment of MBR

permeate by passing it through a GAC column or by dosing of PAC.

2.4.3.1 PAC-MBR systems

PAC is generally added directly into other process units [161]. The application of PAC

into biological treatment systems is usually called powdered activated carbon treatment

(PACT) process [162]. PACT process is based on the concept of simultaneous


28

adsorption and biodegradation, and has been reported to be effective for treating organic

toxic pollutants such as dyes [163]. Orshasky et al. [164] compared the removal

efficiency of three processes for the removal of phenol and aniline: biological treatment,

adsorption on powdered activated carbon and simultaneous adsorption and

biodegradation. The results revealed that simultaneous adsorption and biodegradation

processes achieved the best removal. Shaul et al. [165] reported an enhanced removal of

organics and colour in CAS to which PAC had been added. However, due to short

sludge retention time in CAS, a portion of carbon is wasted frequently along with the

withdrawn sludge. As compared to that in CAS, the use of PAC in MBR may be more

effective.

A PAC- added MBR combines three individual processes, namely physical adsorption

on PAC, biological degradation and membrane filtration in a single unit where all of the

processes occur simultaneously. In the PAC-MBR, membranes provide a physical

barrier preventing the passage of PAC, thus ensuring retention of the organic

compounds adsorbed on the PAC that otherwise would not be rejected by the membrane

alone. High biological activity may also be achieved when PAC is added into MBR

because PAC helps microbial growth in surface [166]. The hybrid process is shown in

Figure 3. The PAC absorbs organic compounds on its surface and extends contact time

between the biomass and adsorbed organic compounds, increases oxygen concentration

at the PAC surface and absorbs compounds that are toxic to the biomass. Hybrid

sorption-membrane bioreactors equipped with either microfiltration or ultrafiltration

modules have been reported for the treatment of landfill leachate and refinery

wastewater as well as for the removal of refractory organic matter from secondary

sewage effluent [159]. Excellent stable decoloration of the waste water containing two

dyes (Poly S 119 and Orange II) was achieved with simultaneous PAC


29

Figure 3: Schematic diagram of the hybrid process

The use of PAC as a support material for organics accumulation and biological

degradation also has the advantage that the effects of shock loads or toxic

concentrations of pollutants can be buffered as a result of their adsorption onto and

diffusion into the activated particles. This results in physical separation of the toxic

materials from the biological catalyst and ensures that the bacteria are able to continue

their metabolic activities [32]. Munz et al. [167] reported the synergistic effect of PAC

addition in an MBR treating tannery wastewater. In their study, PAC was shown to

reduce the negative effects of natural and synthetic tannins that impose toxicity to

tannery wastewater. PAC dosage of 10 g/L improved significantly the leachate

treatment in a PAC – MBR hybrid system [168]. In one study on biodegradation of

trace compounds in an aerobic MBR, it was found that PAC dosage of 500 mg/L

reduced trihalomethane (THM) precursor by over 98% [169]. Addition of PAC in to

MBR also improved effluent quality and provided stability against shock loading [40,

166].

Figure 4 illustrates the effects of PAC addition in an MBR and the underlying reasons

for the associated benefits. Recently, PAC has been widely investigated to mitigate the

fouling problem in membrane hybrid system. The addition of PAC increased the

rejection of low molecular weight organics by adsorption and thus reduced membrane

fouling. Vigneswaran et al. [170] showed that the direct addition of PAC into the

submerged MBR minimized the bio-fouling of the membranes and no chemically

cleaning of the membrane was required for a long time.

Biodegradation

Membrane

separation

Adsorption

Pollutants


30

Figure 4: Schematic illustrating the effects (a), causes (b) and mechanism (c) occurring

in an MBR after PAC addition [166].

The removal of certain trace organics by MBR treatment is unstable (see Section 2.3.2).

As mentioned earlier, two main mechanisms may account for removal of trace organics

in MBRs namely, adsorption on sludge and biodegradation [116]. Obviously, adsorption

mechanisms play an important role in the total removal efficiency of hydrophobic trace

organics in MBRs [7]. For instance, Tadkaew et al. [26] investigated the removal of

two model compounds bisphenol A and sulfamethoxazole and reported that the removal

(c)

(b)

(a) Enhanced biodegradation

involving the breakdown of

refractory compounds

PAC addition in MBR

Capability to tolerate

shock loads of

inhibitory compounds

Slow flux

decline

Improved sludge

dewaterability

Simultaneous adsorption

and biodegradation

Change in particle size, floc

formation, incompressible cake

formation and scouring effect

Synergistic

effects

Additive

effects

Simple combination of

adsorption and

biodegradation

Biofilm formation of PAC, growth of specific

microbial population, increased enzymatic activity,

bio regeneration of PAC


31

efficiency was 90% and 50%, respectively. In contrast to sulfamethoxazole, which is

rather hydrophilic, bisphenol A is a hydrophobic compound, therefore, both

biodegradation and adsorption may be responsible for its removal. Compounds

containing complex structure and toxic groups (such as halogens, nitro groups)

however, can show higher resistance to biodegradation and tend to have very low

removal [26]. Because the adsorption of trace organics onto sludge facilitates their

removal in the biological process, it is envisaged that addition of adsorbents such as

PAC directly into the MBR reactor can lead to significant retention of soluble trace

organics. Due to the complete retention of sludge by the membrane and application of

long SRT, the retained trace organics may be efficiently removed in an MBR to which

PAC has been added.

In recent years, a few studies on the performance of trace organics removal by MBR

coupled with PAC have been published [45, 46]. Results have shown that PAC addition

has positive effects on MBR performance in removal of trace organic contaminants. For

example, Li et al.[45] demonstrated an improved removal of two different PhACs,

namely, sulfamethoxazole and carbamazepine in a PAC-amended MBR system. Serrano

et al.[46] investigated the removal of several recalcitrant PhACs, namely,

carbamazepine, diazepam, diclofenac and trimethoprim by adding PAC into the aeration

tank. The results demonstrated that this approach was a successful tool to improve the

removal of the more recalcitrant compounds (carbamazepine, diazepam, diclofenac and

trimethoprim) up to 85 %.

2.4.3.2 GAC system coupled with MBR systems

While PAC is added directly into the MBR reactor, GAC is used in a packed bed

reactor. In comparison to investigations involving drinking water treatment, only a

handful of studies have investigated GAC adsorption as an option for tertiary treatment

of conventional biologically treated wastewater [10, 34, 156]. It has been noted in those

studies that the adsorption of trace organics on activated carbon decreased due to

competition with bulk organic matter for adsorptive sites. In fact, competition with bulk

organic matter for adsorptive sites has important implications to the lifetime and

serviceability of GAC columns. For efficient adsorption of trace organics, it is

recommended that the feed to GAC column has a low bulk organic content. Because


32

MBR can produce suspended solids-free permeate with low total organic carbon

content, GAC may be a suitable post treatment option for MBR permeate. In such a

system, GAC can specifically target the residual trace organics in MBR permeate

without any significant interference from the bulk organics.

Chapter 3 Methodology

33

CHAPTER 3: METHODOLOGY

3.1 Introduction

This chapter describes the research methodology, experimental setups and analytical

techniques used in this study. The physicochemical properties of the selected trace

organics are also presented in this section. The operation of the lab-scale MBR was

initiated on 7 Feb, 2011. The start–up period continued for 51 days until 29 Mar, 2011

to ensure the stability of operating conditions in the MBR system and build up of

biomass in the reactor. A synthetic wastewater was continuously fed into the MBR. At

the end of the start-up period, mixed liquor suspended solids concentration was 5 g/L.

Following the start-up period, selected trace organic compounds were spiked

continuously into synthetic wastewater that was fed to the MBR. The experimental

scheme has been systematically presented in

Figure 5. Table 4 outlines the timeline of different steps of MBR operation. Further

details will be given throughout this chapter.

Figure 5: Experimental road map

MBR start – up period

MBR combined with activated carbon

Simultaneous PAC adsorption

in MBR (PAC - MBR)

Sequential application of

MBR and GAC adsorption

(MBR - GAC)


34

Table 4: Experimental timetable

Experiment Time (Day)

MBR start- up period (without trace organics in feed) 51

MBR 15

MBR – GAC experiment 93

MBR 38

MBR (after sludge withdrawal) 9

PAC – MBR (0.1 g/L PAC) 36

PAC – MBR (0.5 g/L PAC) 64

3.2 Materials

3.2.1 Selected trace organic compounds

A set of 22 compounds representing four major groups of trace organic contaminants,

namely, (1) pharmaceutically active compounds, (2) pesticides, (3) surfactants and

industrial chemicals, and (4) steroid hormones, were selected in this study. The

selection of these model compounds was also based on their widespread occurrence in

domestic sewage and their diverse physicochemical properties (e.g. hydrophobicity,

molecular weight, charge). The effective hydrophobicity of these compounds varies

significantly as reflected by their Log D at pH 7. A combined stock solution was

prepared in methanol, kept in a freezer and used within a month.

Their physicochemical properties are shown in Table 5.


35

Table 5: Physicochemical properties of trace organics used in this study

Category Compound CAS

number

Molecular

weight

(g/mol)

Log KOWa

Log D at

pH 7 a

Dissociation

constant

( pKa)a

Water

solubility

(mg/L)b

Charge Structure of compounds

Ph

arm

ace

uti

call

y a

cti

ve

com

po

un

ds

Ibuprofen

(C13H18O2)

15687-27-1 206.28 3.50 ± 0.23 0.94 4.41 ± 0.10 21 Negative

Acetaminophen

(C8H9NO2)

103-90-2 151.16 0.48 ± 0.21 0.47

9.86 ± 0.13

1.72 ± 0.50

14000 Neutral

Naproxen

(C14H14O3)

22204-53-1 230.26 2.88 ± 0.24 0.73 4.84 ± 0.30 16 Negative

Ketoprofen

(C16H14O3)

22071-15-4 254.28 2.91 ± 0.33 0.19 4.23 ± 0.10 16 Negative


36

Diclofenac

(C14H11Cl2NO2)

15307-86-5 296.15 4.55 ± 0.57 1.77

4.18 ± 0.10

-2.26 ± 0.50

2.4 Negative

Primidone

(C12H14N2O2)

125-33-7 218.25 0.83 ± 0.50 0.83

12.26 ± 0.40

-1.07 ± 0.40

500 Negative

Carbamazepine

(C15H12N2O)

298-46-4 236.27 1.89 ± 0.59 1.89

13.94 ± 0.20

-0.49 ± 0.20

18 Neutral

Salicylic acid

(C7H6O3)

69-72-7 138.12 2.01 ± 0.25 -1.13 3.01 ± 0.10 2240 Negative

Metronidazole

(C6H9N3O3) 443-48-1 171.15 -0.14 ± 0.30 -0.14

14.44 ± 0.10

2.58 ± 0.34

9500 Neutral


37

Gemifibrozil

(C15H22O3)

25812-30-0 250.33 4.30 ± 0.32 2.07 4.75 19 Negative

Triclosan

(C12H7Cl3O2)

3380-34-5 289.54 5.34 ± 0.79 5.28 7.80 ± 0.35 10 Neutral

Pest

icid

es

Fenoprop

(C9H7Cl3O3)

93-72-1 269.51 3.45 ± 0.37 - 0.13 2.93 71 Negative

Pentachlorophenol

(C6HCl5O)

87-86-5 266.34 5.12 ± 0.36 2.58 4.68 ± 0.33 14 Negative

4-tert-butyphenol

(C10H14O)

98-54-4 150.22 3.39 ± 0.21 3.40 10.13 ± 0.13 580 Neutral


38

Su

rfa

cta

nts

an

d i

nd

ust

ria

l ch

em

icals

4-tert-octylphenol

(C14H22O)

140-66-9 206.32 5.18 ± 0.20 5.18 10.15 ± 0.15 5 Neutral

4-n-nonylphenol

(C15H24O)

104-40-5 220.35 6.14 ± 0.19 6.14 10.15 6.35 Neutral

Bisphenol A

(C15H16O2)

80-05-7 228.29 3.64 ± 0.23 3.64 10.29 ± 0.10 120 Neutral

Ste

roid

horm

on

es

Estrone

(C18H22O2)

53-16-7 270.37 3.62 ± 0.37 3.62 10.25 ± 0.40 677 Neutral

17-β-estradiol

(C18H24O2)

50-28-2 272.38 4.15 ± 0.26 4.15 10.27 3.9 Neutral

HO

(CH2)8 CH3


39

17-β-estradiol –

acetate

(C20H26O3)

1743-60-8 314.42 5.11 ± 0.28 5.11 10.26 ± 0.60

Neutral

17-α

ethinylestradiol

(C20H24O2)

57-63-6 269.40 4.10 ± 0.31 4.11 10.24 ± 0.60 11.3 Neutral

Estriol (E3)

(C18H24O3)

50-27-1 288.38 2.53 ± 0.28 2.53 10.25 ± 0.70 441 Neutral

a Log Kow and pKa are obtained from Sci Finder (ACS) database

b water solubility are obtained from http://chem.sis.nlm.nih.gov/chemidplus/

http://chem.sis.nlm.nih.gov/chemidplus/


40

3.2.2 Synthetic wastewater

A synthetic wastewater that was utilized in a previous study [26] was modified as

mentioned below to simulate medium strength municipal wastewater. A concentrated

stock solution was prepared and stored in a refrigerator at 40C. Then it was diluted with

Milli-Q water on a daily basis to make up a feed solution containing glucose (100

mg/L), peptone (100 mg/L), KH2PO4 (17.5 mg/L), MgSO4 (17.5 mg/L), FeSO4 (10

mg/L), CH3COONa (225 mg/L) and (NH2)2CO (35 mg/L Because the wastewater was

made with Milli-Q water, its turbidity was very low (<1 NTU). The chemical oxygen

demand (COD), total organic carbon (TOC) and total nitrogen (TN) was 600, 180 and

25 mg/L, respectively.

3.2.3 Activated carbon

In this study, two types of activated carbon namely GAC 1200 and PAC 1000

(Activated Carbon, Technologies Pty Ltd, Victoria, Australia), were used. The

characteristics of each type of activated carbon are listed in the Table 6.


41

Table 6: Characteristic properties of PAC 1000 and GAC 1200

Parameters Values

PAC GAC

Apparent density (g/mL) a 0.35-0.45

0.42-0.50

Surface area (MultiPoint BET

m2/g)

b 1355

1121

Ash content (%) a 14

3

Iodine number (mg of I2/g) a > 1000

>1200

Particle size a 15-30 µm

6 x 12 mesh (1.6-2.0

mm)

Pore volume (cc/g) b 0.228

0.043

Pore diameter (nm) b 3.139

3.132

a Data from Activated Carbon Pty Ltd, Australia.

b Data obtained from a nitrogen adsorption/desorption measurement using an

Autosorb iQ. The measurement was conducted at the Australian Nuclear Science

and Technology Organisation. Pore volume and pore diameter were calculated

based on the Barret-Joyner-Halenda method.

3.3 Experimental set-up and operation protocol

3.3.1 Laboratory–scale MBR set-up and operation protocol

A laboratory scale MBR system was employed in this study. A schematic diagram of

the MBR is shown in Figure 7. The MBR system consisted of a glass reactor with an

active volume of 4.5 L, one air pump, a pressure sensor, feed and permeate tanks,

influent and effluent peristaltic pumps. A PVDF hollow fiber membrane module

supplied by Mitsubishi Rayon Engineering, Japan was submerged in the reactor (Figure

8). The membrane had a nominal pore size 0.4 µm and total surface area of 0.074 m2.

Transmembrane pressure (TMP) was continuously monitored using a high-resolution

pressure sensor (± 0.1 kPa) (SPER scientific 840064, Extech equipment Pty Ltd,

Victoria, Australia) to detect probable onset of fouling. During continuous operation

without any routine cleaning, ex-situ chemical cleaning had to be performed only twice

(on day 186 and 306) over the whole operation period (306 days). During ex-situ

chemical cleaning, the membrane was soaked into sodium hypochlorite solution (0.5 g

Cl/L) for 60 min and then backwashed with a freshly prepared sodium hypochlorite


42

solution ((0.5 g Cl/L) at a flux of 0.21 m/d for 30 min. The permeate pump (Masterflex

L/S, Cole-Parmer Instrument Company) was operated on a 14 min suction and 1 min

rest cycle to provide relaxation time to the membrane module. The membrane was

operated under an average flux of 2.6 L/m2h. The average flow rate of the influent pump

was adjusted to match with that of the effluent pump to maintain a constant reactor

volume.

Figure 6: Membrane bioreactor (MBR) set-up (1 Feed tank, 2 Feed pump, 3 MBR , 4

Pressure gauge, 5 Permeate pump, 6 Permeate tank, 7 Computer). Dimensions of the

reactor were 360 mm (H) x 320 mm (L) x 45 mm (W).

(6)

(7) (5)

(4)

(2)

(1)

(3)


43

Figure 7: A schematic diagram of the MBR set up

Figure 8: PVDF hollow fiber membrane module used in this study (dimensions 29 cm

(L) x 17 cm (H) x 1 cm (W), Fiber length and outer diameter of 22 cm and 0.2 cm,

respectively. Membrane nominal pore size = 0.4 µm and total membrane surface area =

0.074 m2)

Feed pump

Suction pump

PC

Permeate tank

Pressure gauge

Membrane reactor

Hollow fiber

membrane

Feed tank

Air pump

Diffuser


44

The reactor was seeded with activated sludge from another lab scale MBR system [26].

The hydraulic retention time was set at 24 hours. Air was supplied via a diffuser located

at the bottom of the aeration tank. Temperature and the dissolved oxygen concentration

of the mixed liquor were maintained at 20 ± 0.1 oC and 3 ± 1 mg/L, respectively. The

pH of the mixed liquor remained stable within the range of 7.2 – 7.5. After an initial

start up period of 51 days, stable operation of the MBR in terms of TOC and TN

removal had been achieved. At this point, the selected trace organic compounds were

added to the synthetic wastewater. The performance of the MBR system was

investigated in terms of trace organic contaminants removal efficiency, TOC/TN

removal and ammonium/ nitrate removal. Operating parameters, namely,

MLSS/MLVSS concentration, turbidity, EPS and SMP concentration, SVI and SOUR

were also monitored. Duplicate samples of both influent and effluent were taken once a

week for trace organic contaminants analysis throughout the operation period.

3.3.2 Laboratory–scale MBR-GAC set-up and operation protocol

A borosilicate glass column (Omnifit, Danbury, CT, USA) filled with 7.5 g of GAC was

used as a post-treatment unit for the MBR permeate. The column had an internal

diameter and an active length of 1 cm and 22 cm, respectively resulting in a bed volume

(BV) of 17 mL. GAC-1200, obtained from Activated Carbon, Technologies Pty Ltd,

Victoria, Australia, was utilized in this study. The characteristics of the utilized GAC

have been outlined in Table 6. The GAC set-up also contained a pump, and influent and

effluent tanks. The GAC set-up has been presented in

Figure 10.


45

Figure 9: Fixed bed GAC column. A borosilicate glass column (1cm diameter x 22 cm

L) filled with 7.5 g GAC was used.

Figure 10: Combined MBR – GAC system

GAC

effluent

tank

Feed pump

GAC fixed

bed column

Suction

pump

Permeate

tank

Pressure gauge

Membrane

Bioreactor

Feed tank

Air

pump

Diffuser

GAC post-treatment unit

Hollow fiber

membrane


46

The MBR permeate was pumped through the GAC column in an up-flow mode at a

flow rate 2.4 mL/min (8.5 BV/h), resulting in an empty bed contact time (EBCT) of 7

min. The GAC post treatment column was attached to the MBR setup at two weeks

after the start of spiking the synthetic wastewater with trace organics, and it was

operated for thirteen weeks (equivalent to 18093 BV).

The performance of the MBR – GAC system was investigated in terms of trace organic

contaminants removal efficiency, and TOC/TN removal. Independent batch tests were

conducted to explain the breakthrough profiles observed in the GAC column (see

Section 3.3.4).

3.3.3 Laboratory scale PAC - MBR set-up and operation protocol

During this part of experiment, the MBR set-up and operation were exactly the same as

before (see Section 3.3.2). In the course of 196 days of continuous operation, the MLSS

concentration in the MBR rose up to 11.5 g/L. MLSS concentrations were reduced to 5

g/L by withdrawing sludge on day 197. Nine days after the withdrawal of the sludge,

PAC (Table 6) was added into the reactor on day 206 and subsequently on day 243 of

continuous operation to obtain a PAC concentration of 0.1 and 0.5 g/L, respectively.

PAC (0.45 and 1.8 g, respectively) was mixed with 200 mL feed media which was then

poured into the MBR. Operating conditions (temperature, HRT, pH and DO

concentration) were kept the same as that during MBR operation without PAC.

All analyses including that of trace organics were performed in the same fashion as in

MBR only or MBR – GAC experiment.

3.3.4 Adsorption isotherm

Adsorption is a natural process by which molecules of a dissolved compound adhere to

the surface of an adsorbent. The process involves concentration changes in both phases

[171]. In case of the activated carbon application for the removal of trace organics from

wastewater, concentration of the trace organics in liquid phase decreases while

concentration in the activated carbon surface increases. The specific capacity of

activated carbon to adsorb organic compounds is related to: molecular surface

attraction, the total surface area available per unit weight of carbon, and the

concentration of contaminants in the wastewater [172]. Adsorption isotherms are widely

used as a tool to evaluate activated carbon adsorption capacity. The isotherm represents


47

an empirical relationship between the amount of contaminant adsorbed per unit weight

of carbon and its equilibrium water concentration.

3.3.4.1 Kinetic experiments

Kinetic experiments were designed to determine the time necessary for the adsorption

process to reach equilibrium. 30 mg of fresh GAC was added in each of 6 breakers

separately; then 100 mL of 20 mg/L trace organic solution was added. All the beakers

were covered with aluminium foil and placed in a shaker (BL 4500 Bioline incubator,

Edward Instrument Company, NSW, Australia) at a speed of 150 rpm and under a

temperature of 22°C. Then 2 mL sample was taken at 0, 6, 12, 18, 24, 36 and 48 hrs,

respectively. The concentration of trace organic in sample was measured by Shimadzu

HPLC systems (see Section 3.4.7.2).

3.3.4.2 Isotherm experiment

Fresh GAC was added in amounts ranging from 15 to 50 mg in glass beakers separately.

Then 100 mL of single trace organic solution with a concentration of 20 mg/L was

added into each beaker. All the beakers were covered with aluminium foil and incubated

for 24 h under 22 oC and 150 rpm in a temperature controlled rotary shaker (BL 4500,

Bioline, Edward Instrument Company, NSW, Australia). Samples were taken after 24 h

(previously established point of equilibrium adsorption). The concentration of trace

organic in sample was measured by Shimadzu HPLC systems (see Section 3.4.7.2).

The experimental data was evaluated by fitting to the Freundlich and Langmuir

isotherms. The equation that describes the Freundlich isotherm is given below.

nefe Ckq

1

(1)

The equation can be rewritten in a linear form as follows:

efe Logcn

LogkLogq1

(2)

The Langmuir isotherm can be expressed in the following form:


48

m

e

me

e

q

c

qq

c

b

1

(3)

Where:

qe equilibrium mass of compound adsorbed on unit mass of adsorbent (mg/g)

Ce equilibrium concentration of compound in liquid (mg/L)

Kf Freundlich partitioning coefficient (mg/g)/(mg/L)1/n

1/n Freundlich exponential coefficient

qm amount of adsorbate adsorbed per gram of adsorbent (mg/g)

b Langmuir’s constant (L/mg)

qmb adsorbent adsorbate relative affinity (L/g)

3.4 Analytical techniques

3.4.1 Total organic carbon and total nitrogen

All samples were kept at 4oC and analysed within two weeks. TOC and TN

concentrations were determined using Shimadzu TOC/TN-VCSH analyser (Figure 11).

The combination of the TOC-VCSH and the TNM-1 can simultaneously measure TOC

and TN. TOC analysis was conducted in non-purgeable organic carbon (NPOC) mode

in order to reduce a large error in TOC value due to high amount of inorganic carbon

(IC) in the samples. The sample was acidified and sparged with ultra purity (zero grade)

air to drive off the inorganic carbon in the form of CO2 gas. For total nitrogen

determination, the sample is combusted to nitrogen monoxide and nitrogen dioxide.

Calibrations were performed using reagent grade potassium hydrogen phthalate and

reagent grade potassium nitrate in the range from 0 to 1,000 mg/L for TOC and from 0

to 100 mg/L for TN, respectively. Calibrations were performed using reagent grade

potassium hydrogen phthalate and reagent grade potassium nitrate for TOC (0 to 100

mg/L) and TN (0 to 100 mg/L) measurement, respectively.


49

Figure 11: Total organics carbon and total nitrogen analyzer system (1 Auto sampler

and sample tray, 2 TOC analyzer, 3 TN analyzer unit, 4. Computer).

TC standard solutions were prepared by adding 2.125 g of pre-dried (105 oC, 1 h)

reagent grade potassium hydrogen phthalate into 1L of Milli Q water. This solution was

used as the standard stock solution with the concentration of 1,000 mg C/L. The

standard stock solution was diluted with Milli Q water to prepare standard solutions at

0, 5, 10, 25, 50 and 100 mg C/L (Figure 12).

(1) (2)

(3)

(4)


50

0 100 200 300 400 500

0

20

40

60

80

100 TOC concentration (mg/L) = 4.7 x average peak area

R2

= 0.99

TO

C c

once

ntr

atio

n (

mg C

/L)

Average peak area (mV)

Figure 12: A typical TOC calibration curve to determine TOC concentration in samples


51

TN standard solutions were prepared by adding 7.219 g of pre-dried (105 oC, 3 h)

reagent grade potassium nitrate into 1L with Milli-Q water. This solution was used as

the standard stock solution with the concentration of 1,000 mg N/L. The standard stock

solution was diluted with Milli-Q water to prepare standard solution at 0, 5, 10, 25, 50

and 100 mg N/L (Figure 13).

0 200 400 600 800 1000 1200 1400 1600 1800

0

20

40

60

80

100

Average peak area (mV)

TN

co

nce

ntr

atio

n (

mg

N/L

)

TN concentration (mg/L) = 16.59 x average peak area

R2 = 1

Figure 13: A typical TN calibration curve to determine TN concentration in samples

3.4.2 DO concentration, pH, turbidity, and sludge volume index

The pH and dissolved oxygen (DO) of mixed liquor in the MBR was measured by a

Metrohm Advanced pH/Ion Meter and DO meter (YSI model 59, USA), respectively.

Turbidity of influent, supernatant and effluent samples were measured by a turbidity

meter (HACH 2100A). It is an optical method, which measures the amount of scattering

when light passes through the sample. The turbidity meter was calibrated by using

standard solution each time before measuring.

The sludge volume index (SVI) is the volume in mL occupied by 1 g of sludge after 30

min settling. SVI typically is used to monitor settling characteristics of activated sludge

and other biological suspensions. Although SVI is not supported theoretically,

experience has shown it to be useful in routine process control. The SVI is calculated

by following equation:


52

)( 0 MLSSV

VSVI

(4)

Where:

SVI is the sludge volume index (mL/g).

V is the volume of the sludge that has been allowed to settle for half an hour (mL).

Vo is the initial volume of the sludge before being allowed to settle (L).

MLSS represents the mixed liquor suspended solids concentration (g/L).

3.4.3 Mixed liquor suspended solids and mixed liquor volatile suspended solids

Mixed liquor suspended solids (MLSS) represents the concentration of non- soluble

solids in the mixed liquor in the bioreactor. The solids are comprised of biomass (dead

and living bacteria as well as debris) and organic and inorganic compounds either

introduced from raw wastewater or produced during biomass growth and decay. MLSS

gives an estimation of the biomass concentration. A mixed liquor sample of 25 mL was

taken from the bioreactor once a week. The sample was centrifuged for 10 min with

1073 x g; the supernatant was discarded and the sludge was transferred to a pre-weighed

crucible. The sample was kept in a water bath for 1 h at 100 oC to dewater the sample

and then over night in an oven at 100 oC. The sample was weighed after the temperature

of the crucible cooled down to the room temperature. For mixed liquor volatile

suspended solids (MLVSS) measurement, the samples were put in the furnace at 550 oC

for 15 min, during which the organic fraction evaporated leaving behind the inorganic

portion. The MLSS and MLVSS are expressed by g/L.

Calculations:

MLSS = mdried sample – m empty crucible (5)

MLNVSS = m evaporated sample – m empty crucible (6)

MLVSS = MLSS – MLNVSS (7)

Where:

MLSS is mixed liquor suspended solids (g/L)

MLVSS is mixed liquor volatile suspended solids (g/L)

MLNVSS is mixed liquor non-volatile suspended solids (g/L)


53

3.4.4 Specific oxygen uptake rate (SOUR)

Microorganisms in sludge use oxygen as they consume available organic matter. The

level of microbial activity in sludge is indicated by the microorganism oxygen uptake

rate. Some conclusions about the situation in the reactor e.g. organic load, presence of

toxins in feed and changes in metabolism can be made by periodically monitoring

SOUR [173]. Lower oxygen uptake rates than usual may indicate a reduced microbial

activity due to any form of stress.

Spiked and un-spiked SOUR were measured throughout the study. For the un-spiked

SOUR, on the day of measurement, 400 mL sludge was taken out of the reactor and the

concentration of DO was increased by aeration for 30 min to reach air saturation. Then a

part of the sample was transferred to a 300 mL borosilicate bottle and kept well mixed

by a stirrer attached to the DO probe. DO was recorded for 15 min in 30-second

intervals using a DO meter (YSI model 59, USA). In the spiked SOUR, the MBR feed

was mixed with mixed liquor (1:1 V/V).

The oxygen consumption rate was calculated as following and represented in mg O2 /

L* hr.

)/(60 2 hrLmgOslopeOUR (8)

Where:

Slope = Slope of the linear portion of the DO profile versus time

The SOUR was obtained by dividing the oxygen uptake rate by the mixed liquor

volatile suspended solids (MLVSS) concentration.

)/( 2 gMLVSShmgOMLVSS

OURSOUR

(9)

3.4.5 Nitrate and Ammonium

Nitrate concentration was measured by an ion chromatography system (Figure 16)

(Shimadzu, Japan). MBR feed, supernatant, MBR permeate, and GAC effluent samples

were measured twice a week. The mixed liquor sample was centrifuged for 10 min at

1073 x g and the supernatant was used to measure nitrate. Standard solutions of

potassium nitrate (KNO3) having a concentration of 5, 10, 15, 20, 30, 40 and 50 mg/L of


54

NO3-.were prepared The concentration of nitrate in sample was calculated based on the

calibration curve established from the standard solutions.

0

500000

1000000

1500000

2000000

25000000

10

20

30

40

50

Nit

rate

co

nce

ntr

atio

n (

mg

/L)

Peak area (µS)

NO3

- = 0.0002 x peak area + 2.91

R2 = 0.99

Figure 14: A typical calibration curve to determine nitrate concentration in samples

Ammonium concentration was measured using phenate method [174]. The analytical

reagents were hypochlorous acid, manganous sulphate solution and phenate reagent.

The reaction of ammonia, hypochlorite and phenol catalyzed by a manganous salt

produces a bluish color corresponding to a wave length of 630 nm. The sample

preparation was same as that of nitrate samples. Ammonium chloride (NH4Cl) was used

to prepare standard solutions having a concentration of 0.1, 0.5, 1.0, 2.0, 2.5 and 5 mg/L

of NH4+. An UV- visible spectrophotometer (Shimadzu UV-1700, Japan, Figure 20)

was used to measure the absorbance at a wavelength of 630 nm. The concentration of

ammonium in samples was calculated based on the calibration curve established from

the standard solutions.


55

0.0 0.2 0.4 0.6 0.8 1.0 1.2

0

1

2

3

4

5

Co

nce

ntr

atio

n N

H3-N

(m

g/L

)

Absorption at 630 nm (1/cm)

NH3-N concentration = 4.22 x Abs - 0.25

R2 = 0.98

Figure 15: A typical calibration curve to determine ammonium concentration in

samples

Figure 16: An Ion-chromatography system (1 Pump part, 2 Auto sampler, 3 Column

chamber, 4 Conductivity detectors, 5 System controller, 6 Computer).

(1)

(2) (3)

(4)

(5)

(6)


56

3.4.6 Extracellular polymeric substances and soluble microbial products

Extracellular polymeric substances (EPS) are a complex mixture of polymers excreted

by microorganisms. They are mainly made up of humic and fulvic acids,

polysaccharides, proteins, amino acids and exocellular enzymes [175]. Many authors

have defined two types of EPS: soluble and bound EPS. The soluble part appears in the

supernatant, and it is also referred to as soluble microbial product (SMP). The bound

EPS exists as a capsule surrounding the bacteria cell wall [176]. SMP and EPS have

been found to influence various properties of activated sludge such as floc strength and

size distribution, dewaterability, settleability and compressibility, non-settleable solids

fraction and hydrophobicity. Although controversies exist, EPS and SMP have been

reported as important parameters governing membrane fouling [177].

The mixed liquor and permeate sample were collected in this experiment for EPS and

SMP measurements. The samples were stored in the fridge at below 4oC for 2 weeks

until measurement. The process of sample preparation has been illustrated in Figure 17.

The mixed liquor samples were centrifuged for 20 min at 3270 x g to separate the SMP

and EPS. After centrifugation, the supernatant, which contains SMP, was transferred to

20 mL amber bottles. The rest of the samples were subjected to EPS extraction. EPS

was extracted by adding 50 mL of sodium chloride (0.9%) into the samples and then

placing it in a water bath at 80 oC for one hour. After that the samples were centrifuged

for 20 min at 3270 x g. Finally, the supernatant was used to detect EPS.


57

Figure 17: Schematic of sample preparation for EPS and SMP determination

For determination of concentration of polysaccharides, a standard calibration curve was

established by using glucose solutions covering a concentration range of 0 to 100 mg/L.

The determination was based on reaction of glucose with phenol and sulphuric acid. An

UV-visible spectrophotometer (Shimadzu UV-1700, Japan, Figure 20) was used to

measure the absorbance at a wavelength of 490 nm. The concentration of samples was

calculated based on the calibration curve shown in Figure 18.

Heat in water bath at 80 0C

for 1 h and cool to room

temperature

25 mL of mixed liquor

sample

Soluble EPS (SMP)

Polysaccharides & Protein

determination on

supernatant

Add 50-100 mL

of NaCl 0.9 %

Bound EPS

Centrifuged at

3270 x g, 20 min

Centrifuged at

3270 x g, 20 min


58

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

0

20

40

60

80

100 Carbonhydrate concentration (mg/L) = 0.013 x Abs + 0.03

R2 = 0.99


Co

nce

ntr

atio

n o

f ca

rbo

nh

yd

rate

(m

g/L

)

Figure 18: A typical calibration curve to determine carbohydrate concentration in

samples

For protein determination, a BSA (Bovine Serum Albumin) solution was used to

develop a calibration curve. The calibration curve covered a range of 0 to 100 mg/L.

The analytical reagents were copper (II) sulphate, sodium carbonate, sodium hydroxide,

and Folin-Ciocalteu reagent. An UV- visible spectrophotometer (Figure 20) (Shimadzu

UV-1700, Japan) was used to measure the absorbance at a wavelength of 750 nm [178].

The concentration of samples was calculated based on the calibration curve shown in

(Figure 19).


59

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35

0

20

40

60

80

100


Co

nce

ntr

atio

n o

f p

rote

in (

mg

/L)

Protein concentration (mg/L) = 0.003 x Abs +0.03

R2 = 0.98

Figure 19: A typical calibration curve to determine protein concentration in samples

Figure 20: An UV-visible spectrophotometer


60

3.4.7 Trace organics analysis

In this study, trace organic analysis was conducted using different methods namely gas

chromatography – mass spectrometry (GC-MS), high - performance liquid

chromatography (HPLC) - UV and liquid chromatography – mass spectrometry (LC-

MS).

3.4.7.1 Gas chromatography – mass spectrometry

The trace organic compounds in feed and permeate samples were extracted using 6 mL

200 mg Oasis HLB cartridges (Waters, Milford, MA, USA). The cartridges were pre-

conditioned with 7 mL dichloromethane and methanol (1:1, v/v), 7 mL methanol, and 7

mL reagent water, respectively. The feed and permeate samples (500 mL each) were

adjusted with H2SO4 0.4 M to pH 2 – 3, then loaded onto the cartridges at a flow rate of

15 mL/min, after which the cartridges were rinsed with 20 mL Milli-Q water and dried

with a stream of nitrogen for 30 min (see Figure 21). The trace organic compounds were

eluted from the cartridges with 7 mL methanol followed by 7 mL dichloromethane and

methanol (1:1, v/v) at a flow rate of 1 – 5 mL/min, and the eluents were evaporated to

dryness under a gentle stream of nitrogen in a water bath at 40 °C. The extracted

residues were then dissolved with 200 µL methanol solution which contained 5 µg

bisphenol A-d16 and transferred into 1.5 mL vials, and further evaporated to dryness

under a gentle nitrogen stream. Finally, the dry residues in the vials were derivatized by

addition of 100 µL of BSTFA (1% TMCS) plus 100 µL of pyridine (dried with KOH

solid), which were then heated in a heating block at 60 – 70°C for 30min. The

derivatives were cooled to room temperature and subjected to GC-MS analysis [179].

Analyses of the trace organic compounds were conducted using a Shimadzu GCMS-

QP5000 system (Figure 23), equipped with a Shimadzu AOC 20i autosampler. A

Phenomenex Zebron ZB-5 (5% diphenyl – 95% dimethylpolysiloxane) capillary column

(30 m × 0.25 mm ID, df = 0.25 µm) was used. Helium carrier gas was maintained at a

constant flow rate of 1.3 mL/min. The GC column temperature was programmed from

100 °C (initial equilibrium time 1 min) to 175 °C via a ramp of 10 °C/min and

maintained 3 min, 175 – 210 °C via a ramp of 30 °C, 210 – 228 °C via a ramp of 2

°C/min, 228 – 260 °C via a ramp of 30 °C, 260 – 290 °C via a ramp of 3 °C/min and

maintained 3 min. The injector port and the interface temperature were maintained at

280 °C. Sample injection (1 µL) was in splitless mode.


61

For the qualitative analysis, the MS full-scan mode from m/z, 50 – 600 was used, apart

from the mass spectrum, the relative retention times of each compound was used for

confirmation of the compound. Quantitative analysis was carried out using selected ion

monitoring (SIM) mode. For each compound, the most abundant and characteristic ions

were selected for quantization. The selected ions of the analysed compounds after silyl

derivatization are in agreement with those reported elsewhere [180-182].

Standard solutions of the analytes were prepared at 1, 10, 50, 100, 500 and 1000 ng/mL,

and an internal instrument calibration was carried out with bisphenol A- d16 as internal

standard. The calibration curves for all the analytes had a correlation coefficient of 0.99

or better. Detection limits were defined as the concentration of an analyte giving a

signal to noise (s/n) ratio greater than 3. The limit of reporting was determined using an

s/n ratio of greater than 10.


62

Figure 21: Schematic of sample preparation for GC-MS measurement of trace organics

(Reagent water is MBR feed without trace organics. MeOH - methanol, DCM –

dichloromethane, SPE – solid phase extraction, HLB -Hydrophilic-lipophilic-balanced)

Sample preparation

600 mL beakers are

rinsed

Filter samples and

adjust pH to 2-3

Take 500 mL sample

SPE equipment requirement

Rinse the lines and valves

1. Methanol

2. Milli-Q water

Wash Oasis HLB cartridge with

1. 7 mL of MeOH-DCM (1:1)

2. 7 mL of Methanol

3. 7 mL of reagent water

Filter the sample through HLB cartridge

(Approximately one individual drop/sec)

Rinse cartridges with 6 x 7mL Milli-Q

water

Dry samples with gentle stream of Nitrogen

(30 min)

Keep the cartridges in freezer


63

Figure 22: The solid phase extraction manifold holding cartridges through which the

sample drips into the perforated chamber below, where tubes collect the effluent. A

vacuum port with gauge is used to control the vacuum applied to the chamber (1 Sample

containers, 2 HLB cartridges, 3 Chamber, 4 Vacuum port).

Figure 23: Gas chromatography-mass spectrometry system (1 Sample tray, 2 Sample

injector, 3 GCMS-QP 5000, 4 Computer)

(1)

(2)

(4) (3)

(1)

(2) (3)

(4)

(1)


64

3.4.7.2 High performance liquid chromatography

The concentration of trace organic in adsorption test samples was measured by a

Shimadzu HPLC system (Shimadzu, Kyoto, Japan, Figure 24) equipped with a Supelco

Drug Discovery C-18 column (with diameter, length and pore size of 4.6 mm, 150 mm,

and 5µm, respectively) and a UV-Vis detector. The detection wavelength was set at 280

nm for carbamazepine and diclofenac and 225 nm for ketoprofen, naproxen and

fenoprop, respectively. The column temperature was set at 20oC. A sample injection

volume of 50 μL was used. The mobile phase composed of acetonitrile and Milli-Q

grade deionized water buffered with 25 mM KH2PO4. Two eluents, namely, eluent A

(80 % acetonitrile + 20% buffer, v/v) and eluent B (20 % acetonitrile + 80 % buffer,

v/v) were delivered at 1.0 mL/min through the column in time-dependent gradient

proportions for 33 minutes. The proportion of eluent B remained at 85 % for the first

five minutes, then gradually dropped to 40 % within the subsequent eight minutes,

remained at 40 % for the next ten minutes, sharply returned to 85 % within the

following one minute, and remained constant for the rest of the period this method was

used to detect carbamazepine and diclofenac. In detection of ketoprofen, naproxen and

fenoprop, the proportion of eluent B remained at 50 % for the first seven minutes, then

gradually dropped to 20 % within the subsequent 12 minutes, and sharply returned to 50

% and remained for 15 minutes. Calibration always yielded standard curves with

coefficients of determination (R2) greater than 0.98 within the range of experimental

concentrations used. The quantification limit for the analytes under investigation using

these conditions was approximated at 10 μg/L.

Table 7: Gradient eluent profiles used in HPLC-UV analyses

For carbamazepine and diclofenac

Time (min) 0 5 13 23 24 33

Eluent B, % 85 85 40 40 85 85

For ketoprofen, naproxen and fenoprop

Time (min) 0 7 19 20 35

Eluent B, % 50 50 20 50 50


65

Figure 24: High performance liquid chromatography system (1 Column, 2 Eluent

containers. 3. Auto sampler, sample tray and degasser, 4 Pump, 5 UV-VIS Detector, 6

Controller, 7 Computer)

3.4.7.3 Liquid chromatography – mass spectrometry

A Shimadzu LC-MS 2020 system (Shimadzu, Kyoto, Japan, Figure 25) was used to

detect metronidazole in the adsorption test. The mobile phase (Milli-Q water with 0.1%

formic acid) – acetonitrile (98:2, V/V) was delivered at a flow rate of 0.5 mL/min. The

injection volume was 5 µL. The data acquisition time was set at 12.5 min. Ionization of

the analyte was obtained by electrospray in the positive ion mode (ESI+), Nitrogen was

used as nebulizer and drying gas, which was set at 1.5 L/ min and 5.0 L/ min,

respectively. Calibration standards were 10, 50, 250, 500, 750, 1000 ng/ mL, calibration

curve yielded with coefficient of determination (R2) greater than 0.98 within the range

of experimental concentrations used.

(1) (2)

(3)

(4) (5)

(6)

(7)


66

Figure 25: Liquid chromatography-mass spectrometry system (1, Computer, 2 Pump

and degasser, 3 Sample injector, 4 Eluent container, 5 Controller, 6 UV-PDA detector, 7

Column chamber, 8 LCMS -2020)

(2)

(3) (1)

(5)

(6) (4)

(7) (8)

Chapter 4 Performance of MBR system

67

CHAPTER 4: PERFORMANCE OF MBR SYSTEM

4.1 Introduction

This study aims to investigate and demonstrate the complementarities between MBR

treatment and application of activated carbon for an enhanced removal of trace organic

contaminants. This chapter provides an overview of the long term performance of the

MBR with respect to the basic water quality parameters such as total organic carbon

(TOC), total nitrogen (TN) removal, Transmembrane pressure (TMP), turbidity, SVI,

MLSS/MLVSS, SOUR, ammonium/nitrate, and the removal of trace organic

contaminants.

4.2 Experimental set up and operation protocol

Detailed descriptions of the MBR system, its operation protocol, and analytical

techniques have been provided in chapter 3. The obtained data is systematically

analysed to depict the overall performance of the MBR throughout the operation period.

4.3 Results and discussion

4.3.1 Mixed liquor suspended solids and mixed liquor volatile suspended solids

The MBR operation was initiated with a MLSS concentration of 3.2 g/L. The MBR was

fed daily with synthetic wastewater without trace organic contaminants during the start-

up period of 51 days. At the end of start-up period the MLSS concentration was 5 g/L.

The profiles of MLSS and MLVSS have been illustrated in Figure 26. Apart from the

samples for MLSS /MLVSS and EPS/ SMP measurement, no sludge was withdrawn

from the MBR during this operation period. As a result, the concentration of MLSS

increased from 5 g/L to 9.8 g/L over a period of 110 days (Figure 26). Nevertheless, the

ratio of MLVSS to MLSS was stable at around 0.9, which indicates that the

accumulation of inorganic compounds did not occur during the experiment. The

increase in MLSS concentration did not lead to any significant variation in TOC and TN

removal (see Section 4.3.5). The observation made in this study is in line with that of

Nghiem et al. [116] who reported that the MBR performance appeared to be

independent of the MLSS concentration. TMP across the membrane module increased

slowly and after 157 days of operation, the TMP was only 10.6 kPa. In absence of any

periodic in situ or ex situ cleaning, the membrane did eventually get fouled. Chemical


68

cleaning of the membrane was performed on day 186, when the TMP of 70.7 kPa was

recorded.

0 20 40 60 80 100 120 140 160

0

1

2

3

4

5

6

7

8

9

10

MLSS (g/L) = 0.04x Time (Day) + 3.29

R2= 0.94

MLSS (g/L) MLVSS (g/L)

ML

SS

/ML

VS

S c

on

cen

trati

on

(g

/L)

Time (day)

S T

Figure 26: Variation of MLSS and MLVSS concentration throughout the operation

period before adding PAC into MBR. ―S‖ and ―T‖ indicate the start-up period and the

point of trace organic contaminants addition, respectively.

4.3.2 Turbidity and sludge volume index

It is generally accepted that MBR provides excellent treated water turbidity [36, 183]. In

this study, the turbidity of MBR permeate was generally below 0.2 NTU and all

recorded data were below 0.4 NTU (Figure 27). Turbidity in water is caused by

suspended and colloidal matter such as organic and inorganic matter including

microorganisms. The MBR process involves a suspended growth-activated sludge

system that utilizes microporous membrane for solid/liquid separation instead of

secondary clarifiers in CAS. Only particles significantly smaller than the maximum

membrane nominal pore size (around 0.4 µm) can pass through the membrane. Thus, it

has been widely reported that MBR can produce suspended solids-free permeate [36,

183, 184].


69

0 20 40 60 80 100 120 140 160

0.0

0.5

1.0

1.5

2.0

2.5

10

15

20

25 Supernatant Permeate

Tu

rbid

ity

(N

TU

)

Time (Day)

TS

Figure 27: Variation of MBR supernatant and permeate turbidity throughout the

operation period. The MBR supernatant was collected after centrifuging the mixed

liquor for 10 min at 1073 x g. ―S‖ and ―T‖ indicate the start-up period and the point of

trace organic contaminants addition, respectively.

Besides the turbidity of MBR permeate, that of the supernatant (obtained by

centrifuging the mixed liquor for 10 min at 1073 x g) was also measured. As can be

seen in Figure 27, supernatant turbidity decreased gradually and remained below 5

NTU. The supernatant turbidity may indicate sludge settleability [140]. At the start-up

period, the supernatant turbidity was 11.2 ± 4.0 (n = 16) and the SVI was significantly

high (see Section 6.3.1.2).

Sludge volume index is widely used to characterize sludge settleability and floc

formation [185, 186]. Figure 28 shows the variation of SVI and MLSS in the MBR.

The SVI varied between 126 and 208 mL/g. The SVI decreased slightly, indicating an

improvement of sludge settleability, with the increase in MLSS concentration.

However, the SVI became stable after 100 days of operation. This indicates the

dependence of SVI on MLSS in the initial phase only. Pollice et al. [187] reported

limited dependence of SVI on the biomass concentration in complete sludge retention

MBR.


70

0 20 40 60 80 100 120 140 1602

3

4

5

6

7

8

9

10

11 MLSS SVI

Time (Day)

ML

SS

(g

/L)

S T

MLSS (g/L) = 0.04x Time (Day) + 3.29

R2= 0.94

0

50

100

150

200

250

SV

I (m

L/g

)

SVI= - 0.62x Time (Day) + 211

R2 = 0.88

Figure 28: Variation in SVI and MLSS concentration of the MBR throughout the

operation period. ―S‖ and ―T‖ indicate the start-up period and the point of trace organic

contaminants addition, respectively.

4.3.3 Dissolved oxygen concentration, pH and specific oxygen up take rate

The MBR was operated under aerobic conditions. Oxygen was supplied via a diffuser

located at the bottom of the aeration tank. DO concentration and sludge pH was

measured on a daily basis throughout the operation period and the values fluctuated in a

range of 6 - 8 mg/L and 7.2 – 7.5, respectively. The optimum pH for biological

performance of MBR appears to be near neutral pH [122]. Therefore, in this study, the

MBR was operated within the recommended range of pH.

The oxygen consumption rate can be used as an indicator of metabolic activity of sludge

in the MBR at different periods of operation [188]. In this study both spiked and un-

spiked SOUR were measured for comparison purpose. The recorded data has been


71

presented in Figure 29. As can be seen in Figure 29, the un-spiked SOUR values were

low and fluctuated in a range of 0.76 to 1.42 (mg O2/h*g MLVSS) only during the

continuous operation. As expected, the spiked SOUR appeared more sensitive towards

biological changes in the MBR. However, the values varied within a range of only 14 ±

3 (n=9), and it apparently did not impose any impact on the removal performance (see

Section 4.3.5).

0 20 40 60 80 100 120 140 1600

2

4

6

8

10

12

14

16

18

20

unspiked SOUR spiked SOUR

SO

UR

(m

g O

2/h

*g

ML

VS

S)

Time (Day)

ML

VS

S (

g/L

)

0

1

2

3

4

5

6

7

8

9

10

MLVSS

S T

Figure 29: Variation of SOUR throughout operation period. ―S‖ and ―T‖ indicate the

start-up period and the point of trace organic contaminants addition, respectively.

4.3.4 Nitrate and ammonium

Biological treatment processes use nitrifiers and denitrifiers to achieve the removal of

nitrogenous compounds from wastewater. Normally, nitrate and nitrite produced by

nitrifiers under aerobic condition would be cycled to an anoxic condition to achieve

denitrification [189]. Nitrogen removal requires both aerobic and anoxic stages. In an

aerobic MBR, nitrification occurs because of a high SRT that can create a suitable

condition for the growth of nitrifying microorganisms [190]. A strategy to increase the

removal of nitrogenous compounds may be to configure the system so that aerobic and

anoxic regimes occur sequentially (e.g., intermittent aeration) [191]. Alternately anoxic

zones, separated by baffles from the aerobic part, can be established within the same

tank [189]. In this study, the MBR was operated under aerobic conditions (DO

concentration > 3 mg/L). As such, significant denitrification was not expected to occur


72

in the MBR. This is evident by the low removal of total nitrogen (see Section 4.3.5) and

detection of nitrate in MBR permeate (Figure 31). The nitrate and ammonium

concentration in MBR feed, supernatant and permeate has been illustrated in Figure 30

and Figure 31. The detection of ammonium in MBR permeate (Figure 30) suggests that

complete nitrification did not occur within the reactor. In full scale wastewater

treatment plants, the nitrogenous organics are converted to ammonia during their

transport from the source to the treatment plants in the sewer. In this study, synthetic

wastewater was prepared by adding nitrogen as bound in organics (e.g., urea and

peptone) and was directly fed to the MBR. Accordingly, partial nitrification occurred

following the hydrolysis of the organic-bound nitrogen to ammonia.

0 20 40 60 80 100 120 140 1600

2

4

6

8

10

12

14

16

18

20

22 Feed Supernantant Permeate

Am

mo

niu

m c

on

cen

trat

ion

(m

g/L

)

Time (Day)

S T

Figure 30: Variation of ammonium concentration in MBR feed, supernatant and

permeate throughout the operation period. ―S‖ and ―T‖ indicate the start-up period and

the point of trace organic contaminants addition, respectively.


73

0 20 40 60 80 100 120 140 160

0

1

2

3

4

5

6

7

8

9

10

11 Supernantant Permeate

Nit

rate

co

ncen

trati

on

(m

g/L

)

Time (Day)

TS

Figure 31: Variation of nitrate (NO3-) concentration in MBR feed, supernatant and

permeate throughout the operation period. ―S‖ and ―T‖ indicate the start-up period and

the point of trace organic contaminants addition, respectively.

4.3.5 Total organic carbon and total nitrogen removal

In this study, a synthetic wastewater was used to ensure a consistent influent

composition and to simulate medium strength municipal wastewater in term of TOC

and TN concentration. TOC and TN concentration in both influent and effluent were

measured on a regular basis to assess the basic biological performance of the MBR.

Despite considerable variation in the MLSS concentration in the reactor as shown in

Figure 26, the removal efficiencies of both TOC and TN remained relatively constant

(Figure 32, Figure 33). As such, the performance of the MBR in term of TOC and TN

removal appears to be independent with the MLSS concentration in the reactor [116].

The removal of TOC varied between 90% and 99% with an average of above 95%, and

the TOC concentration in permeate was typically less than 7 mg/L. The MBR achieved

above 98 % removal of TOC even though the TOC concentration in influent was kept at

elevated levels (double) from day 18 to day 27 in order to accelerate sludge growth.

The high removal of TOC was in good agreement with previous literature [122]. It is

also worth noting that the removal of TOC did not change after the start of adding trace

organic contaminants (dissolved in methanol) in the synthetic wastewater although the

concentration of TOC in the feed increased from 135 mg/L to 180 mg/L. A similar


74

observation was made by Li et al. [45]. They noticed that the continuous high dosing

(750 µg/L) of micropollutants (carbamazepine and sulfamethoxazole) to the feed for

extended period did not exert any discernible adverse effect on TOC and TN removal.

0 20 40 60 80 100 120 140 1600

2

4

6

8

100

150

200

250

T Influent Effulent

TO

C (

mg

/L)

Time (Day)

Rem

ov

al (

%)

IS

0

20

40

60

80

100

Removal

Figure 32: TOC concentration in MBR influent, effluent and the removal efficiency of

TOC throughout the operation period. ―I‖, ―S‖ and ―T‖ indicate the period when the


(double) temporarily, the start-up period and the point of trace organic contaminants

addition, respectively.

As noted earlier, the MBR system was operated under aerobic conditions (DO > 3

mg/L) and, therefore, was not expected to have high nitrogen removal via

denitrification. Accordingly, the TN removal in our study ranged from 31 to 68%

(Figure 33). Notably, nitrogen in the synthetic feed solution was supplied mostly in

organic-bound form (from peptone and urea). The ratio of influent COD, total nitrogen

and total phosphorous (CODin:TN:TP) in the synthetic feed solution was 150:6.5:1, and


75

residual ammonia at a concentration of 6 mg/L was detected in the MBR permeate. This

suggests that partial nitrification occurred following the hydrolysis of the organic-bound

nitrogen to ammonia.

0 20 40 60 80 100 120 140 160

10

20

30

40

50

Infulent Effulent

TN

(m

g/L

)

Time (Day)

Rem

ov

al

(%)

0

20

40

60

80

100

Removal STI

Figure 33: TN concentration in MBR influent, effluent and the removal efficiency

throughout the operation period. ―I‖, ―S‖ and ―T‖ indicate the period when the


(double) temporarily, the start-up period and the point of trace organic contaminants

addition, respectively.

4.3.6 Removal of trace organic contaminants

Given the diverse physicochemical properties of the 22 compounds selected in this

study, it is not surprising that their removal efficiency by MBR varied quite

significantly.


76

Figure 35 illustrates the removal efficiency of trace organics by MBR. Little or no

removal was observed for carbamazepine, diclofenac and fenoprop, while 80 – 99%

removal of all five steroid hormones and four alkyl phenolic trace organics could be

observed. The significant removal of hydrophobic compounds (Log D > 3.2) such as

the hormones and alkyl phenolic compounds used in this study is probably dominated

by sorption to the activated sludge facilitating enhanced biological degradation in some

cases [26, 192]. On the other hand Tadkaew et al., [26], proposed that functional groups

play an important role in determining the extent of biodegradation of compounds

possessing lower hydrophobicity (Log D < 3.2). They systematically demonstrated that

compounds with strong electron withdrawing groups (EWG) are more resistant to MBR

treatment, while the removal of compounds possessing both electron donating group

(EDG) and EWG can substantially vary depending on the number and type of the

functional groups. The low to moderate removal of six significantly hydrophilic

compounds (i.e., carbamazepine, diclofenac, fenoprop, naproxen, ketoprofen and

metronidazole) in this study, therefore, can be attributed to the presence of one or more

strong EWG (such as chlorine atom, amide group and nitro group) or absence of strong

EDG in their structures (see Table 5). Our results regarding the removal efficiency of

these biologically persistent compounds are in line with previous reports [26, 95, 98,

193, 194]. One anomalous result obtained was the high removal of primidone, despite

containing a strong EWG (amide) [26]. A possible explanation may be that the presence

of methyl groups (weak EDG) led to conversion of the methyl group to alcohol [195],

bypassing the problematic amide conversion. On the other hand, in good agreement

with the literature reports [134], among the less hydrophobic compounds (Log D < 3.2)

those containing the strong EDG hydroxyl group (i.e., acetaminophen, salicylic acid,

pentachlorophenol) were consistently removed to a high degree in our study. It is

noteworthy that in line with the observations reported by Hai et al. [140], the removal of

the halogenated organics correlated better with the ratio of halogen content to Log D

rather than Log D only. This substantiates that the former is a better indicator for the

prediction of halogenated trace organics removal by MBR treatment.

In addition to adsorption and biodegradation, volatilization may also contribute toward

the removal of highly volatile trace organics from an aqueous solution. The removal of

a trace organic due to aeration during wastewater treatment depends on its vapour


77

pressure (Henry’s constant) and hydrophobicity [7]. However, given the very low

Henry’s constant (H) and low H/Log D ratio of all compounds selected in this study,

their removal by volatilization is expected to be negligible. Except for MLSS sampling,

no sludge was withdrawn from MBR in this study. The removal via sludge wastage,

therefore, can also be considered to be insignificant.

One may wonder whether the gradual increase in MLSS concentration (Section 3.4.3)

influenced the removal of the significantly hydrophobic compounds (Log D >3.2), for

which biosorption may precede biodegradation. However, the removal of those

compounds in this study was highly stable right from the beginning, nullifying any

apparent effect of MLSS concentration under the tested range.

-2

-1

0

1

2

3

4

5

6

7

Salic

ylic

aci

d

Met

roni

dazo

le

Fenop

rop

Ket

opro

fen

Ace

tam

inop

hen

Nap

roxe

n

Primid

one

Ibup

rofe

n

Dic

lofe

nac

Car

bam

azep

ine

Gem

fibro

zil

Estrio

l

Penta

chlo

roph

enol

4-te

rt-bu

tylp

heno

l

Estro

ne

Bisph

enol

A

17-a

-eth

ynyl

estra

diol

17-b

-estra

diol

17-b

-estro

diol

-17-

acet

ate

4-te

rt-oc

tylp

heno

l

Triclo

san

4-n-

nony

lphe

nol

0

1000

2000

3000

4000

5000

6000

7000

8000

Co

ncen

trati

on

(n

g/L

)

Feed MBR permeate

Log D > 3.2Log D < 3.2

Log D at pH 7

Lo

g D

at

pH

7

Figure 34: Concentration of the trace organic contaminants in feed and MBR permeate.

Samples in duplicate were taken once a week. Error bars represent standard deviation of

26 measurements regularly conducted over 13 weeks.


78

Salicylic acid

Metro

nida

zole

Feno

prop

Ketop

rofe

n

Ace

tam

inop

hen

Nap

roxe

n

Primid

one

Ibup

rofe

n

Diclo

fena

c

Car

bam

azep

ine

Gem

fibro

zil

Estrio

l

Pentach

loro

phen

ol

4-tert-

butylp

heno

l

Estro

ne

Bisph

enol

A

17-a

-eth

ynyles

tradi

ol

17-b

-estra

diol

17-b

-estro

diol

-17-

acetate

4-tert-

octylp

heno

l

Triclo

san

4-n-

nony

lphe

nol

0

10

20

30

40

50

60

70

80

90

100

MBR Log D at pH 7

Rem

ov

al

eff

icie

ncy

(%

)Log D < 3.2 Log D > 3.2

-2

-1

0

1

2

3

4

5

6

7

Lo

g D

at

pH

7

Figure 35: Removal efficiency of the selected trace organic contaminants and their

corresponding hydrophobicity (log D) by MBR treatment. Samples in duplicate were

taken once a week. Error bars represent standard deviation of 26 measurements

regularly conducted over 13 weeks.


79

4.4 Conclusions

This chapter reported the basic biological performance of the submerged MBR system

during continuous operation over a period of over 160 days. The overall biological

performance of the MBR system was quite stable as reflected by the considerably stable

values of the basic water quality parameters.

The reported results in this chapter also confirm that MBR treatment can effectively

remove hydrophobic (Log D > 3.2) and readily biodegradable trace organic compounds,

but is less effective for the removal of hydrophilic (log D < 3.2) and biologically

persistent compounds. The limitation of the MBR treatment in removing hydrophilic

trace organic contaminants requires a complementary post-treatment processes to polish

the MBR permeate prior to water reuse.

Chapter 5 Removal of trace organic contaminants by MBR –GAC system

80

CHAPTER 5: REMOVAL OF TRACE ORGANIC CONTAMINATNS BY A

MEMBRANE BIOREACTOR (MBR) - GRANULAR ACTIVATED CARBON

(GAC) SYSTEM

5.1 Introduction

GAC adsorption has routinely been used as a tertiary treatment process in the water

industry. The potential of activated carbon for the removal of pesticides and other

emerging trace organics in drinking water treatment has been widely demonstrated [19,

30-32]. However, much of the available literature focused on the removal of trace

organics by activated carbon from surface water [34] and only a few have investigated

the use of GAC adsorption for the removal of trace organics from biologically treated

effluent [10, 33, 34]. An aggravated competition with bulk organics for adsorptive sites

is usually a common phenomenon associated with such applications, and this has

important implications to the life and serviceability of GAC columns. Because MBR

can produce high quality effluent with virtually no suspended solids and with very low

total organic carbon content [36], GAC adsorption is expected to specifically target the

residual trace organics in MBR permeate without any significant interference from the

bulk organics.

Adsorption on GAC may lead to high initial removal of trace organics; however, over

time, the adsorption capacity of the GAC column will eventually become exhausted

[34]. A system, therefore, needs to be in place to appropriately design a specific GAC

system and determine the point of regeneration of the spent carbon. Quantitative

structure activity relationship (QSAR) models have been developed to predict activated

carbon adsorption capacity for herbicides, pesticides, and other low-molecular-weight,

neutral compounds on the basis of molar volumes and hydrogen bonding affinity as the

key predictive parameters [4, 33, 202]. However, several specific trace organic classes

could not be accurately predicted using such models [4]. Furthermore, QSAR models

require parameters (e.g., hydrogen bonding affinity) that are difficult to obtain for many

deprotonated/protonated acid and base compounds [202]. To date, experimental studies

of the equilibrium and breakthrough dynamics of trace organics in activated carbon

systems remain very limited [32, 34].

In this chapter, the removal of trace organics via sequential applications of GAC

adsorption following MBR treatment was presented. The extent of overall removal of a


81

set of selected compounds possessing varieties of chemical structures was assessed. The

breakthrough behavior of biologically persistent and hydrophilic compounds was

systematically investigated through long-term operation of the GAC column and a

series of batch tests. Discussion was furnished on the use of log D (hydrophobicity),

charge, and adsorption isotherm parameters to generally identify the set of compounds

likely to experience rapid breakthrough and about possible indicators of the initiation of

trace organic breakthrough (e.g., saturation of the GAC column with total nitrogen).


Detailed descriptions of the MBR-GAC system, its operation protocol, and analytical

techniques have been provided in chapter 3. The obtained data is systematically

analysed to depict the overall performance of the MBR - GAC over more than three

months of continuous operation. Based on the long-term overall removal performance

of the MBR - GAC systems, six problematic trace organics (carbamazepine, diclofenac,

ketoprofen, naproxen, fenoprop and metronidazole) were selected for single solute batch

adsorption isotherm tests (see Section 3.3.4).


5.3.1 Performance stability and TOC/ TN removal by the MBR- GAC system

The same operating condition of the MBR was maintained throughout this operation

period. Sludge withdrawal was not conducted except for the MLSS and EPS/SMP

sampling, thus allowing for a gradual build up of the MLSS concentration in the reactor

from 5 to 9.8 g/L. Performance of the MBR with respect to the removal of TOC and TN

was stable during the entire study. Turbidity of the MBR permeate was always below

0.2 NTU. The addition of trace organic contaminants to the influent did not result in any

discernible disturbance on the MBR performance regarding the basic water parameters

described above.

The background carbonaceous organic content of the MBR permeate was low. The

TOC concentration in the MBR permeate was mostly between 1 and 3 mg/L and was

always below 5 mg/L (Figure 36). GAC post-treatment only resulted in a marginal

reduction in the concentration of TOC. In the absence of a denitrification zone, the TN

removal by the MBR was approximately 50% and up to 15 mg/L of TN could be

detected in the permeate (Figure 36). GAC post-treatment did not result in any


82

discernible reduction in the concentration of TN (Figure 36). GAC was reported to

show negligible removal of ammoniacal compounds through physical adsorption, which

was attributed to their high polarity and solubility in water [203]. Results reported here

(Figure 36) suggest that adsorption of background organic matter in the MBR permeate

to the GAC was negligible and the background organic matter did not compete

significantly for the adsorptive sites of the GAC.

0 2000 4000 6000 8000 10000 12000 14000 160000

1

2

3

4

5

6

7

8

0

50

100

150

200

0 2000 4000 6000 8000 10000 12000 14000 160000

5

10

15

20

25

30

0

5

10

15

20

25

30

Number of bed volume

TO

C c

on

cen

trati

on

(m

g/L

)

(F

eed

)

MBR permeate GAC effluent

TO

C c

on

cen

trati

on

(m

g/L

)

(MB

R p

erm

eate

, G

AC

eff

luen

t)

100 % saturation(a)

Feed

TN

co

ncen

trati

on

(m

g/L

)

(

Feed

)

Feed MBR permeate GAC effluent 100 % saturation

TN

co

ncen

trati

on

(m

g/L

)

(MB

R p

erm

eate

, G

AC

eff

luen

t)

(b)


Figure 36: TOC (a) and TN (b) concentrations in GAC effluent, MBR permeate and

feed throughout the operation period


83

5.3.2 Complementary removal of trace organics by MBR – GAC system

The low removal of hydrophilic and biologically persistent trace organic compounds by

MBR treatment (see Section 4.3.6) may necessitate a post-treatment process. Several

previous studies have proposed the use of GAC filtration for the removal of trace

organics from surface water or biologically treated wastewater [10, 19, 32-34]. Our

results (Figure 37) confirm that initially GAC post-treatment could significantly

improve the removal of the compounds which demonstrated low to moderate removal

by MBR treatment (i.e., metronidazole, carbamazepine, diclofenac, ketoprofen,

fenoprop, and naproxen). In this study, because all significantly hydrophobic

compounds had already been well removed by MBR treatment (see Section 4.3.6) and

competition of the background organic matter for the adsorptive sites was low, the GAC

post treatment process was particularly effective for the removal of hydrophilic trace

organic compounds from the MBR permeate. However, results presented in Figure 38

also show that the performance of the GAC column gradually deteriorated, and at

approximately 18,000 BV no additional removal of fenoprop and diclofenac by the

GAC column could be observed. Results reported here suggest that strict monitoring

should be applied over the life of the GAC column to detect the breakthrough point of

hydrophilic and persistent compounds which have low removal by MBR treatment.

Whether there was any biological activity in the GAC column was not specifically

monitored in this study. However, based on the gradual breakthrough of TOC (The

TOC concentration in GAC effluent was higher than that in MBR permeate (Figure 36))

as well as the trace organic contaminants, it can be stated that biodegradation within

GAC media may not have occurred.


84

0

20

40

60

80

100R

emo

val

eff

icie

ncy

(%

)

MBR GAC 406 BV

0

20

40

60

80

100

Rem

ov

al e

ffic

ien

cy (

%)

MBR GAC 4472 BV

0

20

40

60

80

100

Rem

ov

al e

ffic

ien

cy (

%)

MBR GAC 9148 BV

Salic

ylic

aci

d

Met

roni

dazo

le

Fenop

rop

Ket

opro

fen

Ace

tam

inop

hen

Nap

roxe

n

Primid

one

Ibup

rofe

n

Dic

lofe

nac

Car

bam

azep

ine

Gem

fibro

zil

Estrio

l

Penta

chlo

roph

enol

4-te

rt-bu

tylp

heno

l

Estro

ne

Bisph

enol

A

17-a

-eth

ynyl

estra

diol

17-b

-estra

diol

17-b

-estro

diol

-17-

acet

ate

4-te

rt-oc

tylp

heno

l

Triclo

san

4-n-

nony

lphe

nol

0

20

40

60

80

100

Rem

ov

al e

ffic

ien

cy (

%)

MBR GAC 18093 BV

(a)

(b)

(c)

(d)

Log D < 3.2 Log D > 3.2

Figure 37: Overall removal of trace organic contaminants by MBR-GAC system at 406

BV (a), 4472 BV (b), 9148 BV (c), 18093 BV (d)


85

5.3.3 Adsorption of single compound on GAC

The adsorption isotherms give useful information on the adsorption capacity of a given

adsorbate on a given adsorbent for a particular range of concentration. Therefore, they

play a crucial role in the choice and in the utilization of adsorbents. In this study, the

parameters of Freundlich (F) and Langmuir (L) models were evaluated by fitting the

theoretical isotherm to experimental data. Six problematic trace organics

(carbamazepine, diclofenac, ketoprofen, naproxen, fenoprop and metronidazole) were

selected based on the long-term overall removal performance of the MBR-GAC systems

for conducting the adsorption isotherm. Table 8 summaries the results obtained for

Freundlich and Langmuir isotherm parameters of selected trace organic compounds.

The adsorption data for GAC fitted the Langmuir isotherm relatively better.

The results showed that GAC has a good adsorption capacity for all selected trace

organic compounds, with the calculated qm (Langmuir maximum adsorption capacity)

ranging from 41.2 to 250.0 mg/g. Therefore, it can be expected that a full scale GAC

filter unit will efficiently remove these compounds.

Table 8: GAC adsorption isotherm constants for six biologically persistent hydrophilic

trace organic compounds

Compound

Freundlich isotherm constants Langmuir isotherm constants

Kf

(mg/g)/(mg/L)1/n

1/n R

2 qm

(mg/g)

b

(L/mg) R

2

Metronidazole 29.3 0.36 0.92 84.3 1.3 0.99

Fenoprop 53.2 0.23 0.96 49.3 1.80 0.99

Ketoprofen 48.3 0.33 0.99 62.11 1.35 0.97

Naproxen 19.6 0.60 0.86 41.2 1.16 0.98

Diclofenac 29.2 0.42 0.93 94.3 0.76 0.96

Carbamazepine 54.2 0.56 0.95 250.0 0.76 0.99

Freundlich isotherm: qe = Kf Ce1/n

Langmuir isotherm:

qe, equilibrium mass of compound sorbed on unit mass of adsorbent; Ce, equilibrium

concentration of compound in liquid; qm, Langmuir maximum adsorption capacity; Kf,

Freundlich partitioning coefficient; 1/n, Freundlich exponential coefficient; b,

Langmuir’s constant; qmb, adsorbent-adsorbate relative affinity

m

e

me

e

q

C

bqq

C 1


86

5.3.4 Breakthrough of biologically persistent hydrophilic compounds

5.3.4.1 Analysis of breakthrough profiles

The breakthrough profiles of six hydrophilic trace organics (metronidazole,

carbamazepine, diclofenac, fenoprop, naproxen, and ketoprofen) exhibiting low removal

efficiency by MBR treatment were examined to provide further insight to their

adsorption to GAC. Percentage of the ratio of GAC effluent concentration and influent

concentration (MBR permeate) during the same sampling event has been presented as

breakthrough values in Figure 38. Significant differences in the breakthrough profiles

amongst these hydrophilic trace organic compounds are evident in Figure 38. While a

20 % breakthrough of diclofenac, ketoprofen, fenoprop, and naproxen occurred within

1000-3000 BV, the same did not happen in case of metronidazole and carbamazepine

before 11000 BV. Breakthrough profiles are influenced by the characteristics of the

target trace organics, properties of the activated carbon, the influent water quality, and

operational conditions [204]. In the current study, apart from the experimental variation

of the influent loading, all other parameters remained unchanged. Therefore discussion

regarding the removal efficiency or breakthrough can be focused on the characteristics

of the target trace organics. In the literature, several solute properties that influence the

adsorption of organic compounds onto activated carbon have been identified. These

properties include, among others, solute hydrophobicity, aromaticity, charge, size, and

presence of specific functional groups [4, 19, 33, 34, 202, 204, 205]. The adsorption

mechanisms related to these properties occur simultaneously, and their respective

dominance can vary from compound to compound [4, 33].

It has been reported that hydrophobic partitioning is more relevant at higher log D

values, while non-hydrophobic interactions govern in case of compounds with low log

D [4, 31, 33]. All six compounds (metronidazole, carbamazepine, diclofenac, fenoprop,

naproxen, and ketoprofen) presented in Figure 38 were of low hydrophobicity and, as

expected, no particular correlation between their log D and extent of breakthrough could

be ascertained (Figure 38). Notably, although the two neutral compounds

(metronidazole and carbamazepine) possess significantly different log D values (-0.14

and 1.89, respectively), they demonstrated similar removal efficiency. In addition, their

removal efficiency was higher than that of all four negatively charged compounds of

concern in Figure 38. This observation is in line with that of Vieno et al., [204] who


87

reported higher affinity of the neutral pharmaceutical carbamazepine when compared to

an ionic compound — naproxen. Yu et al. [31] also observed severer reduction in

adsorption capacity for the acidic compound naproxen, compared to the neutral

compound carbamazepine.

In addition to hydrophobic partitioning, various other mechanisms such as hydrogen

bonding, - -interaction between aromatic rings, and van der Waals forces (e.g., dipole-

dipole interaction, London dispersion force) can contribute towards the adsorption of a

compound onto a specific adsorbent [4, 19, 33, 34, 202, 204, 205]. However, as noted

earlier, their relative dominance will depend on the specific compound. For instance, it

has been reported that larger number of hydrogen bond donor groups implies stronger

hydrogen bonding between the solute and adsorbent than between the solute and water

[33]. For solutes possessing no hydrogen-bond donor/acceptor groups, however, the

main bonding mechanisms are van der Waals dispersion forces and/or - -interaction.

On the other hand, an aliphatic solute without any hydrogen bond donor/acceptor

groups can form neither - bonds nor hydrogen-bonds, and the weaker van der Waals

forces may then become more dominant for its removal [4]. Furthermore, the presence

of specific functional groups in the structure of compounds can also influence their

adsorption onto adsorbent. For instance, Radovic et al. [206] reported that the presence

of electron-withdrawing functional groups will influence the -electron distribution by

removing electrons and creating positive holes in the conduction band of the -electron

system, thus decreasing the adsorption potential on the carbon surface.

All six compounds under consideration in Figure 38 are aromatic and possess one or

more strong electron withdrawing groups, and except for carbamazepine and

metronidazole, all are negatively charged. Therefore, - -interaction and/or other

specific polar interactions can be considered relevant mechanisms, although their

relative importance may be different for each compound. For instance, dispersion

interactions of -electrons of their aromatic rings with -electrons of the carbon

graphene planes was reported to govern the adsorption of metronidazole [207], while

hydrogen bonding with adsorbent was reported to be the predominant mechanism in

case of diclofenac and naproxen, which are strong hydrogen bond donor solutes [33]. A

detailed quantitative assessment of structure-activity relationship [4, 33, 202], and

confirmation of the specific dominating mechanism for each compound fall beyond the


88

scope of this study. In the context of this study, it is more important to note that the

neutral compounds (carbamazepine and metronidazole) showed slower breakthrough

than the negatively charged compounds (Figure 38).


89

02000

40006000

800010000

1200014000

1600018000

0

1000

2000

3000

4000

5000

6000

7000

0

20

40

60

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02000

40006000

800010000

1200014000

1600018000

0

1000

2000

3000

4000

5000

6000

7000

0

20

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02000

40006000

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1600018000

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02000

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4000

5000

6000

7000

0

20

40

60

80

100B

reak

thro

ug

h (

%)

Co

ncen

trati

on

(n

g/L

)

MBR effluent GAC effluentC

on

cen

trati

on

(n

g/L

)

Metronidazole (Log D = -0.14)

Neutral

Bre

ak

thro

ug

h (

%)

Breakthrough

Ketoprofen (Log D = 0.19)

Negatively charged


Bre

ak

thro

ug

h (

%)

Co

ncen

trati

on

(n

g/L

)


Diclofenac (Log D = 1.77)

Negatively charged

0

20

40

60

80

100

Bre

ak

thro

ug

h (

%)

Co

ncen

trati

on

(n

g/L

)

0

20

40

60

80

100Carbamazepine (Log D = 1.89)

Neutral

Bre

ak

thro

ug

h (

%)

Co

ncen

trati

on

(n

g/L

)

Fenoprop (Log D = -0.13)

Negatively charged

Bre

ak

thro

ug

h (

%)

Co

ncen

trati

on

(n

g/L

)Naproxen (Log D = 0.73)

Negatively charged

Figure 38: Breakthrough profiles of six biologically persistent and hydrophilic trace

organic compounds as a function of bed volume (BV)


90

5.3.4.2 Prediction of breakthrough

For a full scale installation, monitoring the breakthrough of a large set of compounds

may not be always feasible. Adsorption isotherms give useful information on the

adsorption capacity of a given adsorbate on a given adsorbent for a particular range of

concentration. In order to generally assess the applicability of isotherms in predicting

the order of breakthrough of the compounds, the breakthrough data were contrasted

with the adsorption isotherm parameters obtained from a series of batch tests. Table 8

shows the Langmuir and Freundlich isotherm parameters (qm and Kf, respectively) for

the compounds that demonstrated relatively rapid breakthrough from the GAC column.

Our isotherm data conform to the general trends found in the literature, such as

relatively higher adsorption capacity of the neutral compounds carbamazepine [19, 205,

208] and metronidazole [207] in comparison to that of the ionized compounds, namely,

diclofenac [19, 205, 208] and naproxen [19, 205, 208]. However, as shown in Figure 40,

the isotherm parameters did not demonstrate any discernible correlation individually

with any of the governing parameters such as log D, number of hydrogen-bond

donor/acceptor groups, dipole moment or aromaticity ratio of the compounds. This

observation is also in line with that of De Ridder et al. [4] and reaffirms the point

discussed earlier (Section 5.3.4.1) regarding the simultaneous roles of various governing

mechanisms on net adsorption.

Because reasonably linear breakthrough profiles for the compounds (except

metronidazole) were obtained (Figure 38), percentage breakthrough (BT) at the end of

operation (18093 BV) was plotted against the Langmuir (qm) and Freundlich (Kf)

isotherm parameters (Figure 39). qm was observed to fit BT data relatively better. The

inverse relationship between qm and BT was evident from the plot; however, the

coefficient of determination (R2) of the fitting line was only 0.38. Such deviation is not

surprising, given the fact that the single-solute isotherms were obtained in ultrapure

water (Milli-Q), and for analytical reasons the isotherms were obtained at equilibrium

concentrations higher than that applied to the GAC column. In fact, inaccuracies arising

from mismatch between equilibrium concentration and actual loading [31] and due to

the effect of competition with bulk organics [19, 148] have been previously

documented. The fact that the MBR permeate concentration (i.e., feed to the GAC

column) was not completely stable for individual compounds, and varied within a few


91

thousands of ng/L between the compounds (Figure 38), may have been also responsible

for such deviation. Nevertheless, the isotherm data can be useful to predict a general

trend regarding the set of compounds likely to experience rapid breakthrough. It is also

worth noting that the difference between the behaviour of the neutral (carbamazepine

and metronidazole) and the ionized compounds was predicted by the isotherm

parameters.

It is noteworthy that the GAC column became completely saturated with TN and TOC

within 1000 and 11000 BV, respectively (Figure 36), while the complete breakthrough

of diclofenac occurred after 18000 BV. Hernández-Leal et al. [34] also observed

significant removal of micropollutants following the saturation of a GAC column by

background TOC. However, from the practical point of view, the detection of a defined

level of breakthrough, not complete breakthrough, is important. In this context, it is

interesting to note that the point of TN saturation (1000 BV) coincides with the

initiation of appreciable level (e.g., 20%) of trace organic breakthrough. Under the

tested level of TN concentration (10-15 mg/L) in the influent to the GAC column, it

appears that TN saturation can be a useful indicator of the initiation of trace organics

breakthrough.


92

0 20 40 60 80 1000

50

100

150

200

250

0 20 40 60 80 1000

10

20

30

40

50

60

50 % breakthrough

Charged compoundsNeutral compounds

qm

q m(m

g/g)

Breakthrough (%) at 18903 BV

(a)

1

6

3

4

5

2

Breakthrough (%) at 18903 BV

Charged compoundsNeutral compounds

Kf

Kf(m

g/g)

/(m

g/L

)1/n

1

6

4

3

5

2

(b)

50 % breakthrough

Figure 39: Relationship between breakthrough (%) and adsorption isotherm constants

(qm, Langmuir maximum adsorption capacity (a) ; Kf, Freundlich partitioning coefficient

(b)).(1.Metronidazole, 2.Fenoprop, 3.Ketoprofen, 4.Naproxen, 5.Diclofenac,

6.Carbamazepine). The breakthrough values are defined as percentage of the effluent

concentration over the influent concentration of the same sampling event.


93

-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.00

50

100

150

200

250

q m(m

g/g)

Log D at pH 7

1

23

4

5

6

1

23

4

5

6

0

10

20

30

40

50

60

Kf(m

g/g)

/(m

g/L

)1/n

4.0 4.5 5.0 5.5 6.0 6.5 7.00

50

100

150

200

250

Hydrogen bonding affinity

Kf(m

g/g)

/(m

g/L

)1/n

q m(m

g/g)

623

4

42

3

1

1

5

5

0

10

20

30

40

50

60

0.12 0.14 0.16 0.18 0.20 0.22 0.240

50

100

150

200

250

qm K

f

Kf(m

g/g)

/(m

g/L

)1/n

q m(m

g/g)

Aromaticity ratio

1

1

2

2

4

4

3

3

5

5

6

0

10

20

30

40

50

60

0.0 0.5 1.0 1.5 2.0 2.5 3.00

50

100

150

200

250

Dipole moment (debyes)

0

10

20

30

40

50

60

Kf(m

g/g)

/(m

g/L

)1/n

q m(m

g/g)

1

1

5

5

4

4

2

23

3

6

Figure 40: Relationship of adsorption isotherm constants (qm, Langmuir maximum

adsorption capacity; Kf, Freundlich partitioning coefficient) with various individual

parameters (governing adsorption of organics onto activated carbon) for biologically

persistent six hydrophilic trace organics. 1. Metronidazole, 2.Fenoprop, 3.Ketoprofen,

4.Naproxen, 5.Diclofenac, 6.Carbamazepine. Dipole moment was calculated by


94

molecular modelling Pro software using ―Modified Del Re‖ method. Aromaticity ratio

denotes the ratio of number of aromatic bonds to total number of bonds in a molecule.

5.4 Conclusions

High ( 98%) removal of trace organics by a GAC column following the MBR

treatment was demonstrated. However, through long-term observation, significant

breakthrough of six hydrophilic and biologically persistent compounds (carbamazepine,

diclofenac, fenoprop, naproxen, ketoprofen and metronidazole) was detected. Of the six

problematic compounds, the neutral compounds (carbamazepine and metronidazole)

demonstrated slower breakthrough than the rest of the compounds which were

negatively charged. The difference between the behaviour of the neutral and the charged

compounds was accurately predicted by the single solute isotherm parameters. Under

the tested level of TN concentration (10-15 mg/L) in the influent to the GAC column, it

appears that TN saturation can be a useful indicator of the initiation of trace organics

breakthrough.

Chapter 6 Removal of trace organic contaminants by PAC - MBR hybrid system

95

CHAPTER 6: REMOVAL OF TRACE ORGANIC CONTAMINANTS BY

PAC - MBR HYBRID SYSTEM

6.1 Introduction

The incomplete removal of biologically persistent trace organic contaminants by MBR

treatment has been reported in the literature. The results presented in chapter 4 reaffirm

the problem. Therefore, it is necessary to formulate modified treatment processes to

adequately address this problem. Chapter 5 describes GAC adsorption post-treatment

process for MBR permeate. The reported data demonstrate that GAC adsorption can

effectively serve the purpose of post-treatment of MBR permeate. The application of

PAC within MBR has been studied in relation to membrane fouling mitigation [37, 40].

Despite the conceptual expectation of enhanced biodegradation of biologically

persistent organic compounds in a PAC - enhanced MBR, a few studies have in fact

assessed this aspect in relation to different types of wastewater, namely, textile

wastewater [41], distillery wastewater [166], tannery wastewater [167], oily wastewater

[38], and leachate [209]. To date, only a few studies have specifically explored PAC -

MBR for the removal of trace organics [44-46]. Previously reported data confirmed the

improved removal efficiency of some trace organics by PAC - MBR; however, a

comprehensive understanding of the involved phenomena has not been developed.

The aim of this chapter was to assess the removal efficiency of the selected trace

organic contaminants in synthetic municipal wastewater by simultaneous application of

PAC in MBR. The addition of PAC into the MBR was assessed as a tool to provide an

additional removal of persistent trace organic compounds. The data pertaining to the

overall removal efficiency of trace organics by the PAC - MBR system was compared

with that relating to the performance of sequential application of GAC adsorption

following MBR treatment. The performance of the PAC – MBR system in regards to

basic water quality parameters is also systematically discussed.


Detailed descriptions of the PAC - MBR set-up, operation protocol, and analytical

techniques have been provided in chapter 3. Before the addition of PAC into the MBR

on day 206, chemical cleaning of the membrane and sludge withdrawal were conducted

on day 186 and 197, respectively. 9 days after the sludge withdrawal, the MLSS


96

concentration in the MBR was at 6 g/L. PAC was added into MBR at this point to

obtain a concentration of 0.1 g PAC /L. Following this, the MBR was operated for 36

days, and on day 243 PAC was added again to obtain a concentration of 0.5 g PAC/L.

In this chapter, the obtained data is systematically analysed to assess the overall

performance of the hybrid PAC - MBR system.


6.3.1 Evaluation of the performance of the PAC - MBR hybrid system

To confirm that the trace organics removal efficiency was obtained under stable

biological activity in the PAC – MBR system, the basic water quality parameters (TOC,

TN, and turbidity removal) and the key operating parameters (pH, temperature, DO

concentration, and MLSS concentration) were periodically monitored. The performance

of the MBR with and without addition of PAC was compared in terms of the basic

water quality parameters and trace organics removal.

6.3.1.1 Mixed liquor suspended solids and mixed liquor volatile suspended solids

The MLSS/MLVSS profile over the entire operation period has been illustrated in

Figure 41. Before PAC addition the MLSS concentration in the MBR increased

gradually; however, no significant change in MLSS concentration was seen after PAC

addition. In fact, the MLSS concentration decreased slightly. Contradictory reports on

the effect of PAC addition on sludge growth have been reported. Lesage et al. [38]

reported that PAC addition may reduce the MLSS concentration increase while

Satyawali et al. [210] mentioned that the MLSS build up was faster as compared to

operation without PAC supplementation. In their study, it took almost 140 days to reach

a MLSS concentration of 8 g/L without PAC supplementation [210] while the same

MLSS concentration was achieved in 65 days with PAC supplementation.[166].

However, the authors [166] did not clarify the underlying reasons of their respective

observations. The slight decrease in the MLSS concentration toward the end in this

study may be attributed to the withdrawal of sludge for MLSS/MLVSS and EPS/SMP

sampling events. During the period of PAC – MBR experiment, approximately 5 g

MLSS was withdrawn for sampling. This is equivalent to an MLSS concentration drop

of 1.1 g/L in the MBR. Assuming that net sludge growth was zero, the amount of sludge

withdrawal can explain the observed drop in MLSS concentration.


97

0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 3200

1

2

3

4

5

6

7

8

9

10

11P

2

MLSS (g/L) MLVSS (g/L)

ML

SS

/ML

VS

S (

g/L

)

Time (Day)

P1R

T

Figure 41: Variation of MLSS and MLVSS concentration in the reactor throughout the

operation period. ―T‖ indicates the point of trace organic contaminants addition, and

―R‖ indicates the point of sludge withdrawal, while ―P1‖ and ―P2‖ indicate points of

PAC addition to achieve final PAC concentrations of 0.1 g/L and 0.5 g/L, respectively.


98

6.3.1.2 Turbidity, Sludge volume index, and SOUR

Turbidity of both MBR and PAC – MBR permeate was consistently observed to be

below 0.2 NTU (Table 9). As discussed earlier in section 4.3.2, owing to complete

removal of suspended solids by membrane filtration, usually MBR permeate is

characterized with very low turbidity [27, 183, 184]. Turbidity in water is caused by

suspended and colloidal matter such as organic and inorganic matter including

microorganism. The MBR process involves a suspended growth-activated sludge

system that utilizes microporous membrane for solid/liquid separation instead of

secondary clarifiers in CAS. Only particles significantly smaller size than the maximum

membrane nominal pore size (around 0.4 µm) can pass through the membrane. Thus, it

is usually reported that MBR can produce suspended solids-free permeate [36, 183,

184].

In a CAS process, to predict the outcome of effluent turbidity, operators usually test the

supernatant turbidity from sludge settling tests as a useful indication of what will

happen in secondary clarifier. The supernatant turbidity results are used to evaluate the

state of biomass dispersion and how well sludge flocculates [211, 212]. High turbidity is

associated with a relatively small fraction of the MLSS, which tends to remain in

supernatant and/or detach easily from sludge flocs [213]. In an MBR, an increase in

supernatant turbidity may be associated with the occurrence of sludge deflocculation

and increase in concentration of soluble matter in the sludge supernatant [213]. A study

by Rosenberger et al. [214] showed that the non-settleable sludge fraction was found to

impact membrane fouling. Other study also found that the solutes in sludge supernatant

played significant role in membrane fouling [215]. The properties of sludge supernatant

may have impacts on membrane performance. Therefore, supernatant turbidity data can

be used to assess the properties of sludge supernatant and as an indicator for evaluating

membrane fouling. In this study, the turbidity of supernatant obtained by centrifuging

and gravity settling, respectively was measured throughout the operation period. The

data has been presented in Figure 42. Except for the initial period, the supernatant

turbidity was already very low even before the addition of PAC, and no significant

change in the supernatant turbidity, irrespective of the method used to obtain the

supernatant, was observed.


99

The sludge volume index (SVI) values decreased significantly after 100 days of

operation and remained stable through to the end of the operation period (Figure 42).

The SVI profile correlated well with that of supernatant turbidity (Figure 42). A

decrease in supernatant turbidity was accompanied by a decrease in SVI value. Previous

studies have reported that the addition of PAC into MBR can enhance floc formation.

For example, a significant enhancement in the biomass settling after an addition of 1

g/L PAC into MBR was observed in a study by Serrano et al.[46]. This was revealed by

an SVI value less than 100 mL/g as compared to the value of 580 mL/g before addition

of PAC. A few other studies have reported that activated sludge shows better settling

properties after PAC addition, due to lower compressibility of sludge flocs [38, 216,

217]. Nevertheless in this study no significant change in SVI value was observed after

PAC addition, suggesting that the sludge originally had good settleability. On the other

hand, the SVI was in fact notably high at the initial period. The results are consistent

with several previous studies where the poor settling properties of sludge were observed

at the beginning of an MBR [46]. This may be attributed to the highly dispersed nature

of the flocs at the beginning of MBR operation. Poor sludge settling and high SVI

values at the start-up period of MBR have been reported in other studies [46]. However,

as the membrane acts as a barrier between liquid/solid phases, poor sludge settling and

high SVI did not affect effluent quality such as turbidity and TOC/TN removal (see

Section 6.3.1.3).


100

0 20 40 60 80100

120140

160180

200220

240260

280300

320

0

10

20

30

40

50

60

Supernatant (centrifuge) Supernatant (gravity settling)

Tu

rbid

ity

(N

TU

)

Time (Day)

SV

I (m

L/g

)

P1

P2T

0

20

40

60

80

100

120

140

160

180

200

220

SVI

Figure 42: Variation of SVI and reactor supernatant turbidity throughout the operation

period. ―T‖ indicates the point of trace organic contaminants addition, while ―P1‖ and

―P2‖ indicate points of PAC addition to achieve final PAC concentrations of 0.1 g/L and

0.5 g/L, respectively. The MBR supernatant was collected in two different ways i.e., by

centrifuging (10 min at 1073 x g), and by gravity settling (30 min), respectively.

In this study both spiked and unspiked SOUR were measured for comparison purpose.

SOUR is often useful to assess microbial activities at different periods of operation of a

biological reactor [188]. The dynamic variation of spiked and unspiked SOUR of both

MBR and PAC - MBR sludge has been illustrated in Figure 43. As can be seen in

Figure 43 virtually no change in unspiked SOUR in both MBR and PAC - MBR was

observed.

The spiked SOUR value gradually improved as the experiment progressed (Figure 43).

Due to the lack of data points during the initial period of this experimental component

(day 132 to day 198), it is difficult to identify the point when the improvement occurred,

but it appears to have happened before addition of PAC probably simply due to gradual

acclimatization. Interestingly, the spiked SOUR value dropped significantly towards the

end of operation period. It has been previously reported that SOUR decreases with

operation time [218, 219]. Under a long sludge age, the accumulation of inert matter in


101

MBR occurs. The reduction of SOUR during prolonged operation of PAC – MBR has

been reported in other studies [38, 216]. Nevertheless, in this study, even after the drop

in SOUR toward the end of operation, the SOUR values were comparable to the values

at the initiation of operation, and such drop apparently did not affect the TOC and TN

removal performance (see Section 6.3.1.4)

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8

10

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14

16

18

20

22

24

26

28

30

0

1

2

3

4

5

6

7

8

9

10

Spiked (1:1) Unspiked

SO

UR

(m

g O

2/h

*g

ML

VS

S)

Time (Day)

P1

P2

Dis

solv

ed o

xy

gen

(m

g/L

)

T DO

Figure 43: Variation of SOUR and DO concentration throughout the operation period.

―T‖ indicates the point of trace organic contaminants addition, while ―P1‖ and ―P2‖

indicate points of PAC addition to achieve final PAC concentrations of 0.1 g/L and 0.5

g/L, respectively.


102

Table 9: Information on some parameters in MBR and PAC – MBR systems (average ± standard deviation) 1

2

Parameters TOC feed

(mg/L)

TN feed

(mg/L)

TOC

permeate

(mg/L)

TN

permeate

(mg/L)

Turbidity

permeate

(NTU)

EPS (mg/g VSS) in

supernatant

SMP (mg/L) in

supernatant

Protein Polysaccharide Protein Polysaccharide

MBR 179 ± 8

(n = 46)

24 ± 2

(n = 46)

3.5 ± 3.2

(n = 46)

12.6 ± 3.3

(n = 46)

< 0.2 67 ± 20

(n = 4)

9.5 ± 2.0

(n = 4)

1.5 ± 1

(n = 4)

2.5 ± 0.4

(n = 4)

MBR + 0.1

g/L PAC

171 ± 10

(n = 10)

23 ± 1

(n = 10)

2.5 ± 1.1

(n = 10)

15.8 ± 2.1

(n = 10) < 0.2

51.0 ± 4

(n = 3)

91.5 ± 12

(n = 3)

11 ± 9.7

(n = 3)

13 ± 11

(n = 3)

MBR + 0.5

g/L PAC

178 ± 6

(n = 15)

26 ± 2

(n = 15)

3.3 ± 2.8

(n = 15)

11.9 ± 3.8

(n = 15)

< 0.2 113 ± 57

(n = 12)

34 ± 24

(n = 12)

18 ± 11

(n = 12)

16 ± 13

(n = 12)

Chapter 6 Removal of trace organic contaminants by PAC- MBR hybrid system

103

6.3.1.3 Comparison of TOC/TN removal by MBR and PAC – MBR systems 3

The average percentage removal of TOC and TN by the MBR and PAC – MBR at two 4

different concentration of PAC addition has been illustrated in Figure 44. It can be seen 5

that the TOC removal was already 98 ± 2 % before the addition of PAC, and an 6

insignificant change in TOC removal was observed in the PAC - MBR system. The high 7

TOC removal efficiency observed in this study can possibly be contributed to the 8

conversion of soluble organics into insoluble biomass rather than their complete 9

mineralisation into carbon dioxide. As expected, a high degree of removal of TOC 10

continued to be achieved in the PAC – MBR system. A similar observation was made 11

by Li et al. [45]. They noticed that TOC removal remained around 97 % even after 12

adding PAC into MBR at a concentration of 1 g/L. 13

On the other hand, as expected, in the absence of a denitrification zone within the MBR, 14

the removal of TN in this study was fairly low (Figure 44). In this study, there was no 15

discernible increase in removal of TN after addition of PAC at a concentration of 0.1 16

g/L. However, a slight increase in TN removal in MBR with a PAC concentration of 0.5 17

g/L was observed. 18

19

20

21


104

MBR MBR+0.1 g/L PAC MBR + 0.5g/L PAC

0

20

40

60

80

100

TO

C r

emo

val

eff

icie

ncy

(%

)

(a)

(b)

MBR MBR+0.1 g/L PAC MBR+ 0.5 g/L PAC

0

10

20

30

40

50

60

70

TN

rem

ov

al e

ffic

ien

cy (

%)

22

Figure 44: TOC (a) and TN (b) removal efficiency in MBR and PAC - MBR system. 23

Error bars represent standard deviation of 46, 10, and 15 samples in MBR, MBR – 0.1 24

g/L PAC and MBR – 0.5 g/L PAC, respectively. 25

In this study, the occurrence of NH3-N in MBR permeate suggests that complete 26

nitrification did not occur. The NH3-N concentrations in MBR permeate fluctuated in 27

the range of 2.5 - 8.4 mg/L (Figure 45). In a submerged MBR at a HRT 24 h an almost 28

complete conversion of NH4+ - N to NO3

- N was achieved with influent NH4

+ - N 29

concentration ranging from 180 mg/L to 1300 mg/L [220]. Li et al. [221] reported that 30

98 % conversion of NH4+ - N to NO3

- - N was achieved in a submerged MBR treating 31

ammonia-bearing inorganic wastewater without sludge withdrawal during 260 days of 32

operation. The high nitrification rate in MBR under a long SRT is attributed to the 33

prevention of washout of the slow-growing nitrifiers, which are responsible for the 34

nitrification process [222, 223]. However, controversies exist regarding the efficiency 35


105

of nitrification process within MBR. Incomplete nitrification of ammonia nitrogen in 36

MBR has been reported in other studies [224, 225]. In full scale wastewater treatment 37

plants, the nitrogenous organics are converted to ammonia during their transport from 38

the source to the treatment plants in the sewer. In this study, synthetic wastewater was 39

prepared by adding nitrogen as bound in organics (e.g., urea and peptone) and was 40

directly fed to the MBR. Accordingly, partial nitrification occurred following the 41

hydrolysis of the organic-bound nitrogen to ammonia. PAC has previously been 42

reported to show negligible removal of ammonium through physical adsorption due to 43

their high polarity and solubility in water [226]. In this study too there was no 44

discernible difference between the levels of ammonium in permeate before and after 45

addition of PAC into MBR. 46

As discussed earlier, (see Section 4.3.4) sequential anoxic – aerobic tanks [227] or 47

separate aerobic and anoxic zones within the same tank [189] or special designs 48

facilitating alternate aerobic and anoxic regimes, such as application of intermittent 49

aeration [191], are required for biological nitrogen removal However, in this study the 50

MBR was operated under aerobic conditions (DO concentration 3 – 7 mg/L) (see 51

Section 4.3.4). In the absence of a denitrification zone or any other means to promote 52

denitrification, complete denitrification was not expected in this study. The nitrate 53

concentration in the MBR permeate remained stable around a value of 2 mg/L during 54

the whole period of operation with PAC. The concentration of nitrate in supernatant and 55

MBR permeate was not much different. 56


106

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5

10

15

20

0 20 40 60 80100

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0

2

4

6

8

10

Feed Supernatant Permeate

Am

mo

niu

m (

mg

/L)

Time (Day)

P1

P2

T

Supernatant Permeate

Nit

rate

(m

g/L

)

Time (Day)

P1

P2T

(a)

(b)

57

Figure 45: Variation of (a) ammonium and (b) nitrate concentration in feed, supernatant 58

and permeate throughout the operation period. ―T‖ indicates the point of trace organic 59

contaminants addition while, ―P1‖ and ―P2‖ indicate points of PAC addition achieve 60

final PAC concentrations of 0.1 g/L and 0.5 g/L, respectively. 61

62

63

64

65


107

6.3.1.4 Transmembrane pressure 66

Membrane fouling is an unavoidable consequence of interactions between mixed liquor 67

and the membrane within an MBR. In absence of periodic cleaning, TMP generally 68

increases with the operating time. The focus of this study was on the removal 69

performance of the MBR. Therefore the reactor was designed as such that frequent 70

membrane fouling, requiring periodic cleaning, could be avoided by maintaining a low 71

average membrane flux. The average membrane flux as applied in this study (0.07 m/d) 72

was significantly lower than the maximum allowable flux (0.8 m/d) reported by the 73

manufacturer for similar but larger modules practically used in MBRs. Therefore the 74

membrane was operated with periodic relaxation (operation in a 14 min on and 1 min 75

off mode) without any periodic cleaning. Nevertheless, TMP was recorded throughout 76

this work. During continuous operation without any routine cleaning, ex-situ chemical 77

cleaning was performed only twice (on day 186 and 306) over the whole operation 78

period (306 days). As can be seen in Figure 46, TMP remained stable during the 51-day 79

start-up period. No abnormal transmembrane pressure increase was observed following 80

the introduction of the trace organic contaminants in the feed solution. The TMP started 81

to gradually increase approximately after 80 days of continuous operation. On day 186, 82

a high TMP value of 70.7 kPa was observed, which necessitated immediate cleaning. 83

Following this, PAC was added directly into the MBR to obtain a PAC concentration of 84

0.1 g/L. Direct addition of PAC into MBR has been widely reported to mitigate 85

membrane fouling [40, 161, 228] via several mechanisms including the adsorption of 86

membrane foulants on PAC, scouring action of PAC, changing the composition and 87

permeability of the cake layer and improved flocculation of MLSS [37, 40, 161, 228, 88

229]. In contrary, A few studies have reported that addition of PAC directly into MBR 89

did not improve the membrane permeability [227, 230]. The data presented in Figure 90

46, at the first instance indicate that TMP in the MBR increased slightly faster after the 91

addition of PAC. However, the MLSS concentration was 6 g/L at the point of initiation 92

of the operation with PAC, while at the very beginning the MLSS concentration was 93

only 3 g/L. Considering the TMP data from day 100 (MLSS concentration at around 6 94

g/L) to day 186 (operation without PAC, MLSS concentration ≥ 6 g/L) and that for day 95

206 to day 306 (operation with PAC, MLSS concentration ≈6 g/L), the rate of TMP 96

increase would in fact seem a bit slower for the operation with PAC. 97


108

EPS and SMP levels in the mixed liquor may have significant implication on floc 98

structure and sludge settleability and consequently on membrane fouling [231-233], 99

although controversies exist [234]. Yamato et al. [234] reported that no clear 100

relationship between the amount of EPS or carbohydrate on membrane fouling in pilot 101

MBR was established. It is worth mentioning that in this study EPS and SMP 102

components have been detected at higher concentration during operation with PAC 103

(Table 9). The contradictory effect of PAC addition on EPS concentration has been 104

reported in the literature. Kim et al. [217] reported that PAC addition decreases the EPS 105

content. In a study by Lesage et al. [38], a decrease in protein and carbonhydrate in 106

MBR supernatant was observed after PAC addition, while Thuy et al. [235] observed an 107

increase in soluble EPS concentration (SMP) after GAC addition into MBR. In addition, 108

variation of EPS content with different PAC dosage has also been reported. A decrease 109

in EPS content was observed at a PAC concentration of 0.75 g/L while an increase in 110

EPS concentration happened when the PAC concentration was doubled [228]. Although 111

the exact reason of elevated SMP during operation with PAC could not be explained, it 112

is interesting to note that despite significantly higher concentration of SMP in the MBR 113

after PAC addition, the rate of TMP increase was not significantly different from that 114

during operation without PAC, indicating that EPS and SMP concentrations did not 115

have any direct effect on fouling. 116

In this study, vigorous aeration was applied to maintain adequate level of DO within the 117

reactor and avoid settling of sludge at the corners of the reactor. However, as the reactor 118

design was not hydraulically optimized, mixing was not found to be adequate enough to 119

avoid settling of sludge at certain locations of the reactor and also to avoid accumulation 120

of sludge onto membrane surface. One may notice from Figure 47 that cake layer 121

appeared to cover more membrane area during the operation with PAC. The coverage 122

and characteristics of cake layer may be another factor responsible for the increase in 123

TMP in PAC – MBR. A comparison on the TMP between two MBRs operated in 124

parallel with 0.75 and 1.5 g/L PAC revealed that the TMP increased faster in the MBR 125

with higher dosage of PAC [228]. The authors explained that in the condition of high 126

PAC concentration, there was more chance of PAC particles to deposit on the 127

membrane surface. A similar observation has been also reported by Aurangzeb et al., 128

[39]. Because the MBR system in this study was not hydraulically optimized, a precise 129


109

comment about the role of PAC on mitigation of membrane fouling cannot be made 130

based on the observations made in this study. 131

132

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0

10

20

30

40

50

60

70

0

1

2

3

4

5

6

7

8

9

10

11

P2

P1

TMP

Tra

nsm

em

bra

ne p

ress

ure

(k

Pa)

Time (Day)

T

Chemical cleaning

ML

SS

(g

/L)

MLSS

133

Figure 46: Variation of transmembrane pressure (TMP) as a function of operation time. 134

―T‖ indicates the point of trace organic contaminants addition while ―P1‖ and ―P2‖ 135

indicate the point of PAC addition to achieve final PAC concentrations of 0.1 g/L and 136

0.5 g/L, respectively. 137


110

(a) Cake layer build up on the membrane

surface in MBR system

(b) Cake layer build up on the membrane

surface in PAC – MBR system

138

Figure 47: Fouled membrane in both (a) MBR and (b) PAC – MBR systems. Pictures 139

were taken on day 186 and 306, respectively. 140

141

6.3.2 Removal of trace organics by PAC - MBR hybrid system 142

As mentioned earlier in Section 4.3.6, low and variable removal efficiency was 143

observed for six biologically persistent and hydrophilic trace organic compounds 144

(metronidazole, fenoprop, ketoprofen, naproxen, diclofenac and carbamazepine) by 145

MBR before the PAC addition. The average removal efficiency of metronidazole, 146

fenoprop, ketoprofen, naproxen, diclofenac and carbamazepine was 39 ± 25 %, 20 ± 15 147

%, 67 ± 12 %, 45 ± 14 %, 15 ± 11 %, and 32 ± 17 %, respectively. Immediately after 148

adding PAC directly into the MBR, a sharp increase in removal efficiency was observed 149

for six biologically persistent and hydrophilic trace organic compounds (metronidazole, 150

fenoprop, ketoprofen, naproxen, diclofenac and carbamazepine), which showed low 151

removal by MBR- only treatment. On the other hand, as discussed earlier in (Section 152

4.3.6), a significant removal of hydrophobic compounds (Log D > 3.2) was observed in 153


111

MBR even before the addition of PAC. The dominant mechanism accounting for the 154

removal of hydrophobic compounds is sorption to activated sludge facilitating enhanced 155

biological degradation in some cases [236], [237]. As expected, a high degree of 156

removal of the hydrophobic compounds continued to be achieved by the MBR after 157

PAC addition. In addition, efficient removal of seven hydrophilic compounds (salicylic 158

acid, acetaminophen, primidone, ibuprofen, gemfibrozil, estriol and pentachlorophenol) 159

(log D < 3.2), which were consistently removed to higher than 60 (pentachlorophenol) 160

to higher than 80 % (the rest six) removal by MBR-only treatment, (see Section 4.3.6) 161

continued in PAC-MBR (Figure 48). 162


112

Salicylic

acid

Metronidazole

Fenoprop

Ketoprofen

Acetaminophen

Naproxen

Primidone

Ibuprofen

Diclofenac

Carbamazepine

Gemifibrozil

Pentachlorophenol

Estriol

4-tert-

butylphenol

Estrone

Bisphenol A

17-a-ethynylestradiol

17-b-estradiol

17-b-estrodiol-1

7-acetate

4-tert-

occtylphenol

Triclosan

4-n-nonylphenol0

20

40

60

80

100Log D < 3.2

Rem

ov

al e

ffic

ien

cy (

%)

A

MBR only Day 2 Day 5 Day 12 Day 18 Day 31

Log D < 3.2

Lo

g D

at

pH

7

-2

0

2

4

6

8

Log D at pH 7

163

Figure 48: Overall removal efficiency of trace organic compounds in PAC - MBR hybrid system after addition of PAC at a concentration of 0.1 164

g/L. 165


113

The removal efficiency for biologically persistent trace organics by the PAC - MBR

system was observed to improve in comparison to that by MBR- only treatment. PAC is

a well-known adsorbent for a wide range of organics (Section 2.4.1). Addition of PAC

into MBR supplies additional adsorptive sites for trace organic compounds in the PAC –

MBR system. Moreover, the growth of microorganisms on PAC surface can constitute a

process called biologically activated carbon. Therefore, conceptually, adsorption,

biodegradation and PAC regeneration can occur simultaneously within the PAC –

MBR. This process can enhance the removal of non- or slowly biodegradable

compounds. Similar observation has been reported in previous studies, for instance, in

case of treating dye wastewater [238] or high strength municipal synthetic wastewater

[45]. In this study, however, the increase in removal efficiency of the biologically and

persistent hydrophilic compounds under a PAC concentration of 0.1 g/L was only

temporary. As can be seen in

Figure 49, the removal efficiency dropped significantly after twelve days of operation

with a PAC concentration of 0.1 g/L. Observation of trace organics removal by the PAC

– MBR system for further twenty days revealed no increase in the removal efficiency of

the biologically persistent hydrophilic trace organic compounds. The possible

explanation is, in the presence of competition with other organics and inorganics in the

synthetic wastewater, PAC addition at a concentration of 0.1 g/L may not have been

sufficient enough to provide adequate additional adsorptive sites for the enhancement of

trace organics. According to Zhang et al., [44] under the competition with other

organics in the synthetic wastewater, only 30 % of the added PAC into MBR was

effectively utilized for carbamazepine adsorption. Other studies also pointed out that

competition for adsorptive sites and pore blockage are two mechanisms involved in the

reduction of adsorption capacity of target compounds on PAC [30, 239].

The instantaneous increase in removal efficiency of six biologically persistent

hydrophilic compounds (metronidazole, fenoprop, ketoprofen, naproxen, diclofenac and

carbamazepine) (log D < 3.2) suggests greater adsorption of trace organics onto PAC

than onto sludge. This observation is in line with available studies which report that

other mechanisms apart from hydrophobic interaction plays role in adsorption of target

compounds onto activated carbon [4, 19, 33, 34, 202, 204, 205]. Therefore, the

application of PAC can be a potential technique to enhance MBR performance.


114

However, as opposed to only temporary improvement in removal, achievement of

relatively more stable performance is important. For further understanding of the

phenomenon, 36 days after the first addition of PAC, PAC was added again to obtain a

PAC concentration of 0.5 g/L in the MBR. Following this, the PAC - MBR was

operated for further 64 days. Under the higher PAC concentration (0.5 g/L), an

improved removal of the hydrophilic and persistent compounds (metronidazole,

fenoprop, naproxen, ketoprofen, diclofenac and carbamazepine) was sustained for a

longer period, beyond which, however, the deterioration in removal efficiency did start

to occur for certain compounds. Although an instantaneous improvement in removal of

all six biologically persistent and hydrophilic trace organic compounds was observed

after addition of PAC, their profiles of removal efficiency followed different trends

afterwards (

Figure 49).

Significant variation in the breakthrough profiles amongst six biologically persistent

and hydrophilic trace organic compounds is evident from Figure 50. During operation

under a PAC concentration of 0.1 g/L, except for ketoprofen, the breakthrough of the

compounds gradually increased over time. Under an elevated concentration of 0.5 g

PAC/L, however, the breakthrough of ketoprofen, carbamazepine and naproxen

remained stable within 20%. Notably, during sequential operation of MBR-GAC, the

order of compounds in terms of decreasing severity of breakthrough was:

fenoprop=diclofenac>ketoprofen>naproxen>carbamazepine>metronidazole, indicating

some differences in breakthrough profiles of the compounds in the two distinct systems.

In the MBR – GAC, fixed bed GAC column treated MBR permeate. Breakthrough from

a GAC column will increase with operation time (number of bed volume) unless there is

biodegradation (like in biologically activated carbon, BAC) or regeneration of GAC

surface. The development of BAC within a GAC column depends on attainment of

several conditions which necessitate special design considerations [240, 241] .However,

in a PAC – MBR system, the bio-regeneration of PAC surface may occur immediately

to increase the adsorptive sites. The differences in breakthrough profiles of the

compounds in MBR - GAC and PAC - MBR may be attributed to the occurrence of bio-

regeneration in PAC - MBR. Nevertheless, the MBR - GAC and the PAC - MBR were

operated in two different configurations. The GAC column treated MBR permeate


115

under less competition for adsorptive sites between trace organics and the bulk organics.

Therefore, a direct comparison between two systems is not possible.

0 10 20 30 40 50 60 70 80 90 100 1100

10

20

30

40

50

60

70

80

90

100

Metronidazole Fenoprop Naproxen

Ketoprofen Diclofenac Carbamazepine

Rem

ov

al

eff

icie

ncy

(%

)

Time (Day)

0.5 g PAC/L

0.1 g PAC/L

Figure 49: Removal of six biologically persistent hydrophilic trace organic compounds

as a function of operation time at 0.1 g PAC/L and 0.5 g PAC/L concentrations.


116

0 10 20 30 40 50 60 70 80 90 100 110

0

10

20

30

40

50

60

70

80

90

100

0.5 g PAC/L0.1 g PAC/L

Metronidazole Fenoprop Naproxen

Ketoprofen Diclofenac Carbamazepine

Bre

ak

thro

ug

h (

%)

Time (Day)

50

% b

reak

thro

ug

h l

ine

Figure 50: Breakthrough profile of six biologically persistent hydrophilic trace organic

compounds as a function of operation time. The breakthrough values are defined as


sampling event.

Table 10 furnishes a preliminary estimate for the purpose of comparison between

simultaneous application of PAC within MBR and sequential application of GAC

adsorption following MBR treatment in terms of activated carbon usage and

effectiveness of the processes. The PAC-MBR was operated for 100 days with a total

addition of 2.25 g of PAC in two stages. A total of 450 L of permeate was produced

during the operation in the PAC - MBR configuration. On the other hand 7.5 g of GAC

in the fixed bed column produced 321 L of permeate over 93 days. When the above data

relating to volume treated per unit weight of GAC (Table 10) is considered in

conjunction with the difference in the extent of breakthrough from each configuration, it

can be said that the PAC-MBR performed relatively better. For instance, a complete

breakthrough of fenoprop and diclofenac occurred in the course of operation of the

GAC column at a GAC usage rate of 42.8 L (effluent) /g (GAC), while in the course of

production of 450 L of permeate from the PAC-MBR, the breakthrough of fenoprop and

diclofenac were 70 and 45 %, respectively although a PAC usage rate of 200 L

(effluent)/ g (PAC) was applied. The comparison of performance between MBR – GAC


117

and PAC – MBR systems in terms of trace organics removal has not been reported in

the literature. However, the performance of PAC—MBR and GAC—MBR in terms of

oily wastewater removal was compared in a study by William et al., [242].The results

highlighted that PAC - MBR was better than GAC – MBR system in terms of economy

(lower capital and operation cost in PAC – MBR system), effluent quality, less frequent

cleaning, tolerance to upsets and immediate acclimation [242]. Based on the current

study, activated carbon, either through sequential operation or through direct addition

into MBR can be used to achieve better removal over MBR-only treatment, however,

dosage and periodic replenishment of activated carbon will be critical for maintaining

excellent removal. In this study, the removal of fenoprop, which demonstrated the worst

removal by PAC – MBR system, was significantly decreased to below 80 % after 17

days of operation with 0.5 g/L PAC addition. If fenoprop is taken as a tracer for the

determination of the frequency of replenishment of PAC for maintaining above 80 %

removal, a 5.8 % of sludge wastage per day (0.26 L/day) and 5.8 % new PAC addition

per day (0.13 g/day).

Table 10: Comparison of the effectiveness between MBR - GAC and PAC - MBR

systems

Parameters MBR – GAC PAC – MBR *

Activated carbon usage during experiment (g) 7.5 2.25

Operation time (Day) 93 100

Treated water volume (L/day) 3.45 4.5

Total treated water volume (L) 321 450

Treated volume per unit weight of activated

carbon (L/g) 42.8 200

Breakthrough of fenoprop (%) **

100 70

Breakthrough of diclofenac (%) **

100 45

* PAC was added at day 206 and 243 to obtain a concentration of 0.1 g PAC/L and 0.5 g

PAC/L, respectively.

**The breakthrough values are defined as percentage of the effluent concentration over

the influent concentration of the same sampling event.


118

Table 11 presents estimated costs of GAC and PAC for operation of MBR – GAC and

PAC – MBR systems, respectively with a typical capacity of 1 m3/day based on the lab-

scale system data. As noted above, for maintaining an SRT of 17 days, 0.26 L of sludge

will need to be withdrawn and 0.13 g of PAC will need to be added daily to maintain a

PAC concentration of 0.5 g/L in MBR. The total corresponding cost for PAC usage is

24.5 AU $ per year. Consequently, the addition of PAC within the MBR treatment

process cost an extra 0.07 AU$/ m3 of treated water. On the other hand, in the MBR –

GAC configuration, 2.2 kg of GAC would need to be replaced every 14 days. The cost

required for GAC usage is 241 AU $ per year, which amounts to a cost of 0.7 AU$/ m3

treated water. Therefore, it can be concluded that simultaneous application of PAC

within MBR is a better configuration compared to sequential application of GAC

adsorption following MBR treatment.

Table 11: Cost analysis for GAC and PAC usage.

Parameters MBR – GAC PAC – MBR

System capacity (m3/day) 1 1

Cost for activated carbon

(AU $/kg) a

4.20 2.15

Activated carbon usage (kg) 2.2 0.5

Total activated carbon usage (kg/year) 57.4

11.4

Activated carbon replenishment period

(Day) b 14

17

Cost for activated carbon usage

(AU$/year) 241 24.5

Cost per unit volume of treated water

(AU$/m3.day)

0.7 0.07

a Typical industrial costs provided by Activated Carbon Technologies Pty Ltd, Victoria,

Australia.

b The activated carbon replacement period was selected to maintain above 80 % removal

of fenoprop in both MBR – GAC and PAC – MBR systems.


119

6.4 Conclusions

The addition of PAC directly into MBR resulted in a sharp increase in removal

efficiency of six biologically persistent and hydrophilic trace organic compounds,

which showed low removal by MBR- only treatment. The high degree removal (>95%)

of the hydrophobic compounds continued to be achieved, while the high removal

efficiency of the biologically persistent hydrophilic compounds did not last for long.

Significant drops in removal efficiencies of all six persistent compounds except

ketoprofen were observed within twelve days of the start of operation with a PAC

concentration of 0.1 g/L. The removal efficiency could be recovered by adding a second

dose of PAC, raising the PAC concentration in the MBR to 0.5 g/L. Good removal

(>70%) of ketoprofen, carbamazepine and naproxen sustained for 64 days (until the

end of operation). Overall, activated carbon, either through sequential operation or

through direct addition into MBR can be used to achieve better removal over MBR-only

treatment, however, dosage and periodic replenishment of activated carbon will be

critical for maintaining excellent removal.

Chapter 7 Conclusions and Recommendations

120

CHAPTER 7: CONCLUSIONS AND RECOMMENDATIONS

7.1 Conclusions

Laboratory scale experiments were conducted to investigate the removal efficiency of

trace organic contaminants by sequential and simultaneous application of activated

carbon adsorption with a submerged MBR system. The MBR system was equipped with

a microfiltration membrane module. Results obtained from this study demonstrate an

excellent performance of MBR regarding basic water quality parameters such as

turbidity, TOC and TN. However, removal efficiency of specific trace organic

contaminants was found strongly dependent on their physicochemical properties. Both

adsorption to the sludge and biodegradation were thought to be responsible for the

removal of hydrophobic compounds. In contrast, the former mechanism was absent for

hydrophilic and biologically persistent trace organic compounds. Accordingly,

approximately 90% removal efficiency or above of hydrophobic trace organic

compounds (log D > 3.2) was recorded, while under the same conditions, the removal

efficiency of less or moderately hydrophobic and biologically persistent trace organic

compounds was significantly variable.

Given the limitations of MBR treatment for the removal of hydrophilic and biologically

persistent trace organic compounds, a GAC post-treatment column was applied to

polish the MBR permeate. Our results confirm that initially GAC post-treatment could

significantly improve the removal of the compounds which experienced low to

moderate removal by MBR treatment (carbamazepine, diclofenac, fenoprop, naproxen,

ketoprofen and metronidazole). Because MBR produces suspended solids free permeate

and all significantly hydrophobic compounds had been already significantly removed by

the MBR, in presence of a reduced competition for the adsorptive sites, the GAC post-

treatment helped removing extensively the hydrophilic compounds from MBR

permeate. However, the adsorption capacity of GAC column gradually diminished, and

within a BV of 18093, there was no further additional removal of six hydrophilic and

biologically persistent compounds (carbamazepine, diclofenac, fenoprop, naproxen,

ketoprofen and metronidazole), especially for fenoprop and diclofenac. Of the six

problematic compounds, the neutral compounds (carbamazepine and metronidazole)

demonstrated slower breakthrough than the rest of the compounds which were

negatively charged. Single solute isotherm data appeared to be a good indicator to


121

predict the set of compounds likely to experience rapid breakthrough and especially can

differentiate the breakthrough behavior of negatively charged and neutral trace organic

contaminants.

Finally, PAC was directly added into the MBR in two steps to achieve a PAC

concentration of 0.1 and 0.5 g/L PAC, respectively. An improved removal of trace

organic contaminants by the hybrid PAC - MBR was demonstrated. Especially,

simultaneous application of PAC within MBR improved the removal performance of

the hydrophilic and biologically persistent trace organic compounds. The removal

performance of certain compounds for example, fenoprop, metronidazole, ketoprofen,

naproxen, diclofenac and carbamazepine was 80 %, 88 %, 92 % , 86 %, 85 %, and 96

%, respectively, after five days of 0.1 g/L PAC addition. However, gradual deterioration

in removal efficiency was observed, where the time taken for a certain level of

deterioration depended on the PAC concentration in the MBR. For example, during

operation under a PAC concentration of 0.1 g/L, except for ketoprofen, the

breakthrough of the compounds gradually increased over time (e.g., above 50 and 80 %

breakthrough was observed for fenoprop and diclofenac after 12 and 16 days of

operation, respectively). Under an elevated concentration of 0.5 g PAC/L, however, the

breakthrough of ketoprofen, carbamazepine and naproxen remained stable within 20%to

the end of the operation period. Periodic sludge withdrawal from MBR was not

practised in this study. Judging from the operation time and PAC concentration-

dependent performance of the PAC – MBR system, periodic withdrawal of sludge and

addition of fresh PAC are recommended. From the performance stability and activated

carbon usage points of view, simultaneous application of PAC within MBR could be a

better choice compared to sequential application of GAC adsorption following MBR

treatment. Overall, application of activated carbon can be used as post-treatment options

for MBR permeate.

7.2 Recommendations for further research

During the process of conducting this research work, new ideas emerged:

(i) Metabolites arising from degradation of the parent compounds need to be monitored

to understand the degradation pathway and the fate of the compounds following MBR

treatment. Data on the degradation pathway and the fate of the compounds would

facilitate the assessment of the potential risks of trace organics.


122

(ii) A comprehensive understanding of the performance of GAC column in removal of

trace organic contaminants will be a useful tool for the water industry in dealing with

these contaminants. As discussed particularly in chapter 5, the GAC column

demonstrated a good capacity of adsorption of a wide spectrum of trace organic

compounds. However, in this study, the GAC column was used to treat suspended

solids free permeate which resulted in an extended lifetime of the GAC column. The

performance of GAC column treating trace organic contaminants spiked in raw

wastewater and in Milli-Q water, respectively will need to be tested to study the effect

of suspended solids and background organics concentration on adsorption process.

(iii) Factors influencing the adsorption process for example, pH and EBCT need also to

be investigated. The results of these experiments will allow us to better understand the

performance of GAC column in the field.

(iv) The PAC dosage in parallel MBRs running under distinct SRTs and MLSS can be

varied to ascertain the effect of PAC dosage, SRT and MLSS on performance of PAC-

MBR. This will directly help to precisely estimate the required dosage and frequency of

withdrawal of spent PAC and replenishment. The effects of different HRTs on trace

organics removal also need to be studied.

(v) The disposal of PAC-mixed sludge from MBR and also the spent GAC from GAC

column can potentially cause secondary pollution by the residual trace organic

contaminants on PAC and GAC. The issue of sludge handling has not been dealt with in

this study. This can be an important point to explore in the future studies.

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Appendix

144

APPENDIX A

RECORDING DATA THROUGHOUT EXPERIMENT

Table 12: TOC and TN concentration in MBR feed and permeate before adding trace

organics into the MBR.

Days TOC (mg/L) TN (mg/L)

Days TOC (mg/L) TN (mg/L)

Feed Permeate Feed Permeate Feed Permeate Feed Permeate

1 25

2 26 252 3.3 48.20 37.02

3 139.90 4.29 27.04 10.34 27

4 28

5 136.9 3.56 27.23 9.04 29 136.3 4.523 24.9 41.75

6 30

7 31

8 132.90 2.67 25.95 11.60 32 145 4.534 27.44 39.92

9 33

10 140.60 2.21 26.53 12.87 34

11 35

12 136.10 2.00 24.98 13.02 36

13 37 128.00 7.273 28.45 39.07

14 38

15 136.90 2.17 25.29 13.92 39

16 40

17 140.00 3.32 26.65 19.83 41

18 42

19 272.50 1.97 48.75 18.04 43 132.60 4.07 26.63 22.57

20 44

21 45

22 268.90 2.61 51.33 28.37 46 136.20 3.193 26.79 19.66

23 47

24 48 124.80 3.428 25.44 21.56

Appendix

145

Table 13: TOC and TN concentration in MBR feed and permeate after adding trace

organics.

Days

TOC (mg/L) TN (mg/L)

Days

TOC (mg/L) TN (mg/L)

Feed Permeate Feed Permeate Feed Permeate Feed Permeate

49 85

50 86 185.5 2.222 26.05 12.12

51 87

52 189.6 2.62 23.16 14.95 88 186.1 1.918 25.63 13.29

53 89

54 190.2 2.37 26.56 13.47 90

55 91 178.1 1.855 24.66 15.06

56 92

57 184.1 5.12 22.01 15.25 93 185.5 2.326 23.77 15.74

58 94

59 184.6 2.00 26.42 16.68 95 184.5 1.553 21.84 12.03

60 96

61 97 183.6 1.54 25.65 8.785

62 98

63 99 170.5 2.484 23.58 10.16

64 184.3 4.11 25.69 12.77 100

65 101

66 164.2 2.27 23.73 13.52 102

67 103

68 178.5 1.45 26.39 12.43 104

69 105

70 106 160.5 5.61 26.04 13.26

71 161.5 1.68 23.79 10.11 107

72 108 173.5 7.72 23.34 13.49

73 189.5 1.639 24.56 9.789 109

74 110 175.8 6.005 22.25 13.58

75 187.3 1.364 26.82 8.578 111

76 112

77 177.8 1.297 25.68 8.834 113 173.2 3.87 23.4 12.79

78 114

79 115 177.2 2.617 24.58 14.21

80 183.4 2.442 25.76 12.45 116

81 117

82 195.5 1.711 24.55 11.47 118

83 119

84 189.1 1.714 24.92 11.66 120 171.3 1.479 19.4 13.08

Appendix

146

TOC (mg/L) TN (mg/L) TOC (mg/L) TN (mg/L)

Day Feed Permeate Feed Permeate Day Feed Permeate Feed Permeate

121 157

122 184.8 6.07 17.87 13.42 158

123 159 174.2 1.845 24.04 13.46

124 160

125 161

126 162

127 178.5 2.761 21.07 10.21 163

128 164 178.1 1.855 23.66 15.06

129 177.2 2.652 23.53 7.609 165

130 166

131 180.6 2.515 25.58 6.572 167

132 168

133 169

134 170.3 2.302 24.56 6.72 170 173.5 7.72 23.34 13.49

135 171

136 173.3 2.132 26.25 13.73 172

137 173

138 174

139 175 184.10 5.12 22.01 15.25

140 176

141 177

142 178

143 173.6 3.2 18.99 13.04 179 178.1 6.22 23.16 17.22

144 180

145 181

146 182

147 183 186 5.45 26.9 20.59

148 184

149 185 189.5 1.901 26.83 21.88

150 170.1 1.758 23.97 9.236 186

151 187

152 188

153 189

154 188.9 2.575 26.65 8.107 190

155 191

156 192

(Table 13, continued)

Appendix

147

Table 14: Trace organics concentration and removal efficiency by MBR - GAC

treatment.

Day 67 Feed After treated by MBR After further treated by GAC

Compounds

Concentration

(ng/L)

Concentration

(ng/L)

Removal

%

Concentration

(ng/L)

Removal

%

Salicylic acid 5946 24 99.6 181 97

Metronidazole 1561 533 65.8 37 97.6

Fenoprop 3760 2559 31.9 29 99.2

Ketoprofen 4919 3076 37.5 57 98.9

Acetaminophen 2104 442 79.0 272 87.1

Naproxen 5153 3735 27.5 50 99

Primidone 1067 69 93.5 33 96.9

Ibuprofen 3039 357 88.2 0 100

Diclofenac 5102 3781 25.9 55 98.9

Carbamazepine 5365 4271 20.4 107 98

Gemfibrozil 7117 332 95.3 10 99.9

Estriol (E3) 2310 44 98.1 35 98.5

Pentachlorophenol 5388 1801 66.6 9 99.8

4-tert-butylphenol 5908 408 93.1 13 99.8

Estone (E1) 4236 15 99.6 13 99.7

Bisphenol A 5810 837 85.6 169 97.1

17-α-

ethinylestradiol

(EE2) 4097 458 88.8 27 99.3

17-β estradiol (E2) 5382 15 99.7 0 100

17-β-estradiol-17-

acetate (E2Ac) 3225 30 99.1 25 99.2

4-tert-octylphenol 7248 75 99.0 19 99.7

Triclosan 6617 56 99.1 20 99.7

4-n-nonylphenol 4516 72 98.4 55 98.8


Appendix

148


Compounds

Concentration

(ng/L)

Concentration

(ng/L)

Removal

(%)

Concentration

(ng/L)

Removal

(%)

Salicylic acid 5974 127 97.9 43 99.3

Metronidazole 1331 449 66.3 2 99.8

Fenoprop 3308 1411 57.3 429 87

Ketoprofen 4501 2345 47.9 273 93.9

Acetaminophen 2466 586 76.2 211 91.4

Naproxen 3845 1510 60.7 22 99.4

Primidone 2706 64 97.6 100 96.3

Ibuprofen 2040 265 87.0 187 90.8

Diclofenac 3914 2510 35.9 280 92.8

Carbamazepine 3774 3597 4.7 90 97.6

Gemfibrozil 4443 142 96.8 23 99.5

Estriol (E3) 1624 2 99.9 1 99.9



Estone (E1) 2082 52 97.5 36 98.2

Bisphenol A 5638 491 91.3 59 99

17-α-ethinylestradiol

(EE2) 3522 340 90.3 25 99.3

17-β estradiol (E2) 3722 16 99.6 3 99.9

17-β-estradiol-17-

acetate (E2Ac) 3715 58 98.4 27 99.3


Triclosan 5294 99 98.1 33 99.4

4-n-nonylphenol 2875 151 94.8 65 97.7


Appendix

149


Compounds

Concentration

(ng/L)

Concentration

(ng/L)

Removal

(%)

Concentration

(ng/L)

Removal

(%)

Salicylic acid 6085 94 98.5 103 98.3

Metronidazole 752 341 54.7 76 89.8

Fenoprop 4172 3866 7.3 915 78.1

Ketoprofen 3481 1113 68.0 342 90.2

Acetaminophen 1806 189 89.5 94 94.8

Naproxen 5884 5387 8.4 796 86.5

Primidone 4390 545 87.6 0 100

Ibuprofen 4496 278 93.8 78 98.3

Diclofenac 5464 5036 7.8 1383 74.7

Carbamazepine 3392 2666 21.4 71 97.9

Gemfibrozil 4098 145 96.5 56 98.6

Estriol (E3) 2030 100 95.1 17 99.2

Pentachlorophenol 4887 2138 56.2 47 99


Estone (E1) 2400 660 72.5 290 87.9

Bisphenol A 4759 289 93.9 32 99.3

17-α-

ethinylestradiol

(EE2) 3354 374 88.9 22 99.3

17-β estradiol (E2) 3039 19 99.4 14 99.5

17-β-estradiol-17-

acetate (E2Ac) 3941 56 98.6 18 99.5


Triclosan 6215 51 99.2 12 99.8

4-n-nonylphenol 2393 100 95.8 54 97.7


Appendix

150


Compounds

Concentration

(ng/L)

Concentration

(ng/L)

Removal

(%)

Concentration

(ng/L)

Removal

(%)

Salicylic acid 5380 89 98.3 286 94.7

Metronidazole 644 437 32.2 94 85.4

Fenoprop 4206 3745 11.0 1231 70.7

Ketoprofen 3429 912 73.4 443 87.1

Acetaminophen 2051 165 91.9 75 96.3

Naproxen 7144 3844 46.2 1187 83.4

Primidone 1911 8 99.6 0 100

Ibuprofen 5411 170 96.9 94 98.3

Diclofenac 6608 5127 22.4 1552 76.5

Carbamazepine 3048 2617 14.1 168 94.5

Gemfibrozil 4493 106 97.6 54 98.8

Estriol (E3) 1446 2 99.8 4 99.7



Estone (E1) 3825 141 96.3 106 97.2

Bisphenol A 5547 180 96.8 51 99.1


(EE2) 3152 260 91.8 46 98.5

17-β estradiol (E2) 3201 12 99.6 5 99.8

17-β-estradiol-17-

acetate (E2Ac) 3789 12 99.7 10 99.7


Triclosan 5610 33 99.4 13 99.8

4-n-nonylphenol 2441 105 95.7 28 98.9


Appendix

151


Compounds

Concentration

(ng/L)

Concentration

(ng/L)

Removal

(%)

Concentration

(ng/L)

Removal

(%)

Salicylic acid 5589 96 98.3 73 98.7

Metronidazole 541 532 1.7 71 86.9

Fenoprop 4570 3666 19.8 2252 50.7

Ketoprofen 3432 917 73.3 404 88.2

Acetaminophen 1246 228 81.7 69 94.5

Naproxen 8279 3971 52 1684 79.7

Primidone 7883 0 100 0 100

Ibuprofen 5478 275 95 16 99.7

Diclofenac 6593 5187 21.3 3652 44.6

Carbamazepine 3142 2631 16.3 316 90

Gemfibrozil 4615 57 98.8 34 99.3

Estriol (E3) 2311 50 97.8 22 99



Estone (E1) 2827 19 99.3 190 93.3

Bisphenol A 5417 104 98.1 26 99.5

17-α-ethinylestradiol (EE2)

3831 162 95.8 38 99

17-β estradiol (E2) 3438 0 100 22 99.4

17-β-estradiol-17-

acetate (E2Ac) 4343 33 99.2 11 99.7


Triclosan 5130 68 98.7 44 99.1

4-n-nonylphenol 2149 171 92.1 94 95.6


Appendix

152


Compounds

Concentration

(ng/L)

Concentration

(ng/L)

Removal

(%)

Concentration

(ng/L)

Removal

(%)

Salicylic acid 5022 70 98.6 162 96.8

Metronidazole 482 462 4.2 16 96.7

Fenoprop 3817 3982 -4.3 2895 24.2

Ketoprofen 3226 1081 66.5 719 77.7

Acetaminophen 1780 143 92 25 98.6

Naproxen 7061 4113 41.8 2135 69.8

Primidone 3839 3 99.9 44 98.8

Ibuprofen 5767 77 98.7 62 98.9

Diclofenac 6273 6589 -5 5057 19.4

Carbamazepine 3140 2486 20.8 549 82.5

Gemfibrozil 4072 44 98.9 35 99.2

Estriol (E3) 1578 33 97.9 25 98.4



Estone (E1) 2404 159 93.4 140 94.2

Bisphenol A 4796 172 96.4 62 98.7

17-α-ethinylestradiol (EE2)

3111 221 92.9 77 97.5

17-β estradiol (E2) 3070 44 98.6 9 99.7

17-β-estradiol-17-

acetate (E2Ac) 3764 53 98.6 10 99.7


Triclosan 4606 19 99.6 38 99.2

4-n-nonylphenol 3142 83 97.4 132 95.8


Appendix

153


Compounds

Concentration

(ng/L)

Concentration

(ng/L)

Removal

(%)

Concentration

(ng/L)

Removal

(%)

Salicylic acid 4420 90 98 149 96.6

Metronidazole 982 630 35.8 0 100

Fenoprop 4418 3620 18.1 2452 44.5

Ketoprofen 3374 875 74.1 510 84.9

Acetaminophen 3861 835 78.4 603 84.4

Naproxen 5827 2703 53.6 1417 75.7

Primidone 5692 496 91.3 56 99

Ibuprofen 5366 72 98.7 34 99.4

Diclofenac 3569 3437 3.7 2884 19.2

Carbamazepine 5486 2846 48.1 453 91.7

Gemfibrozil 4092 22 99.5 24 99.4

Estriol (E3) 2830 33 96.2 46 98.4

Pentachlorophenol 3626 1305 64 238 93.4


Estone (E1) 2708 9 99.7 6 99.8

Bisphenol A 4587 311 93.2 36 99.2

17-α-ethinylestradiol (EE2) 4121 233 94.4 162 96.1

17-β estradiol (E2) 3534 4 99.9 0 100

17-β-estradiol-17-

acetate (E2Ac) 5104 12 99.8 0 100


Triclosan 4486 23 99.5 12 99.7

4-n-nonylphenol 2034 49 97.6 18 99.1


Appendix

154


Compounds

Concentration

(ng/L)

Concentration

(ng/L)

Removal

(%)

Concentration

(ng/L)

Removal

(%)

Salicylic acid 4853 129 97.3 180 96.3

Metronidazole 1553 988 36.4 0 100

Fenoprop 4713 3836 18.6 2635 44.1

Ketoprofen 3869 563 85.5 472 87.8

Acetaminophen 4013 500 87.6 987 75.4

Naproxen 6190 2856 53.9 1278 79.4

Primidone 4811 593 87.7 0 100

Ibuprofen 5955 285 95.2 79 98.7

Diclofenac 3798 3875 -2 2666 29.8

Carbamazepine 5324 2703 49.2 453 91.5

Gemfibrozil 4427 23 99.5 27 99.4

Estriol (E3) 3071 72 97.7 51 98.3


4-tert-butylphenol 4836 435 91 94 98.1

Estone (E1) 2826 19 99.3 0 100

Bisphenol A 5177 555 89.3 43 99.2


(EE2) 4663 280 94 132 97.2

17-β estradiol (E2) 3880 15 99.6 0 100

17-β-estradiol-17-

acetate (E2Ac) 5599 38 99.3 12 99.8


Triclosan 4918 63 98.7 45 99.1

4-n-nonylphenol 2279 78 96.6 73 96.8


Appendix

155

Day 124 Feed After treated by MBR

After further treated by

GAC Compounds

Concentration

(ng/L)

Concentration

(ng/L)

Removal

(%)

Concentration

(ng/L)

Removal

(%)

Salicylic acid 4124 190 95.4 128 96.9

Metronidazole 995 683 31.4 40 96

Fenoprop 5091 4191 17.7 3480 31.6

Ketoprofen 3530 874 75.2 735 79.2

Acetaminophen 1880 226 88 162 91.4

Naproxen 5424 3210 40.8 2108 61.1

Primidone 4407 577 86.9 0 100

Ibuprofen 4630 114 97.5 77 98.3

Diclofenac 4166 3784 9.2 3236 22.3

Carbamazepine 5267 3156 40.1 699 86.7

Gemfibrozil 3919 34 99.1 38 99

Estriol (E3) 3086 120 96.1 105 96.6



Estone (E1) 3017 11 99.6 39 98.7

Bisphenol A 4954 470 90.5 69 98.6


(EE2) 4989 319 93.6 109 97.8

17-β estradiol (E2) 4083 25 99.4 29 99.3

17-β-estradiol-17-

acetate (E2Ac) 4672 0 100 6 99.9


Triclosan 4854 41 99.2 0 100

4-n-nonylphenol 1719 0 100 9 99.5


Appendix

156



GAC Compounds

Concentration

(ng/L)

Concentration

(ng/L)

Removal

(%)

Concentration

(ng/L)

Removal

(%)

Salicylic acid 3810 325 91.5 233 93.9

Metronidazole 918 852 7.2 77 91.6

Fenoprop 3985 3813 4.3 3118 21.8

Ketoprofen 3507 1060 69.8 723 79.4

Acetaminophen 2000 377 81.2 56 97.2

Naproxen 5538 3082 44.3 1707 69.2

Primidone 3953 292 92.6 226 94.3

Ibuprofen 4535 101 97.8 69 98.5

Diclofenac 4899 3870 21 2946 39.9

Carbamazepine 5094 2614 48.7 750 85.3

Gemfibrozil 3925 27 99.3 26 99.3

Estriol (E3) 2768 123 95.6 31 98.9



Estone (E1) 2689 0 100 15 99.4

Bisphenol A 4314 206 95.2 38 99.1


(EE2) 3882 300 92.3 68 98.2

17-β estradiol (E2) 3515 33 99.1 15 99.6

17-β-estradiol-17-

acetate (E2Ac) 4303 37 99.1 38 99.1


Triclosan 3933 28 99.3 31 99.2

4-n-nonylphenol 1112 12 98.9 23 97.9


Appendix

157



GAC Compounds

Concentration

(ng/L)

Concentration

(ng/L)

Removal

(%)

Concentration

(ng/L)

Removal

(%)

Salicylic acid 3049 14 99.5 32 98.9

Metronidazole 863 453 47.5 53 93.9

Fenoprop 4239 4039 4.7 3119 26.4

Ketoprofen 3085 1118 63.7 836 72.9

Acetaminophen 2706 175 93.5 298 89

Naproxen 4937 2757 44.2 1812 63.3

Primidone 4126 1562 62.1 413 90

Ibuprofen 3972 14 99.6 94 97.6

Diclofenac 4418 3796 14.1 3074 30.4

Carbamazepine 3612 2596 28.1 891 75.3

Gemfibrozil 3287 26 99.2 20 99.4

Estriol (E3) 2449 0 100 45 98.2



Estone (E1) 2400 6 99.7 8 99.7

Bisphenol A 4141 92 97.8 24 99.4


(EE2) 3885 260 93.3 107 97.2

17-β estradiol (E2) 3591 27 99.2 0 100

17-β-estradiol-17-

acetate (E2Ac) 5325 75 98.6 24 99.6


Triclosan 4055 29 99.3 19 99.5

4-n-nonylphenol 2109 56 97.3 50 97.6


Appendix

158


Compounds

Concentration

(ng/L)

Concentration

(ng/L)

Removal

(%)

Concentration

(ng/L)

Removal

(%)

Salicylic acid 3896 25 99.4 47 98.8

Metronidazole 1241 385 69 0 100

Fenoprop 4793 3620 24.5 2784 41.9

Ketoprofen 3133 948 69.7 766 75.6

Acetaminophen 3178 59 98.2 55 98.3

Naproxen 5696 2571 54.9 1435 74.8

Primidone 5373 1310 75.6 340 93.7

Ibuprofen 4152 0 100 27 99.4

Diclofenac 3659 3215 12.1 2536 30.7

Carbamazepine 5047 2520 50.1 648 87.2

Gemfibrozil 3591 30 99.2 29 99.2

Estriol (E3) 2597 110 95.8 0 100

Pentachlorophenol 3729 970 74 176 95.3


Estone (E1) 2506 2 99.9 17 99.3

Bisphenol A 4180 76 98.2 18 99.6


(EE2) 3896 174 95.5 63 98.4

17-β estradiol (E2) 3434 4 99.9 12 99.6

17-β-estradiol-17-

acetate (E2Ac) 5382 25 99.5 7 99.9


Triclosan 4399 46 99 13 99.7

4-n-nonylphenol 2538 30 98.8 32 97.9


Appendix

159


Compounds

Concentration

(ng/L)

Concentration

(ng/L)

Removal

(%)

Concentration

(ng/L)

Removal

(%)

Salicylic acid 3296 19 99.4 29 99.1

Metronidazole 1149 323 71.9 140 87.8

Fenoprop 4482 3044 32.1 3136 30

Ketoprofen 2790 1011 63.7 818 70.7

Acetaminophen 3606 160 95.6 195 94.6

Naproxen 5454 2344 57 1936 64.5

Primidone 4971 1257 74.7 646 87

Ibuprofen 3936 16 99.6 24 99.4

Diclofenac 3520 2605 26 2517 28.5

Carbamazepine 4326 2096 51.5 995 77

Gemfibrozil 3436 45 98.7 33 99

Estriol (E3) 2486 43 98.3 0 100



Estone (E1) 2230 42 98.1 31 98.6

Bisphenol A 3957 60 98.5 30 99.2


(EE2) 3694 169 95.4 91 97.6

17-β estradiol (E2) 3344 16 99.5 1 100

17-β-estradiol-17-

acetate (E2Ac) 5165 84 98.4 30 99.4


Triclosan 4060 37 99.1 11 99.7

4-n-nonylphenol 2556 0 100 0 100


Appendix

160

Table 15: Trace organics concentration and removal efficiency by PAC - MBR treatment

with 0.1 g PAC /L concentration.

Day 205 Concentration (ng/L) PAC - MBR

Compounds Feed Permeate Removal (%)

Salicylic acid 2674 122 95.4

Metronidazole 1860 19 99

Fenoprop 2784 145 94.8

Ketoprofen 1844 6 99.7

Acetaminophen 1834 192 89.5

Naproxen 3752 102 97.3

Primidone 3553 17 99.5

Ibuprofen 2995 137 95.4

Diclofenac 3098 139 95.5

Carbamazepine 3793 118 96.9

Gemfibrozil 2534 21 99.2

Estriol 1985 40 98

Pentachlorophenol 2071 114 94.5

4-tert-butylphenol 2726 48 98.2

Estrone 2026 13 99.4

Bisphenol A 2786 24 99.1

17-α ethinylestradiol 3219 53 98.4

17-β- estradiol 2927 8 99.7

17-β- estradiol-17 acetate 3665 14 99.6

4-tert-octylphenol 2867 66 97.7

Triclosan 2532 82 96.8

4-n-nonylphenol 1229 90 92.7


Appendix

161




Metronidazole 1873 225 88

Fenoprop 2889 575 80.1


Acetaminophen 2088 188 91

Naproxen 3708 531 85.7


Ibuprofen 2763 21 99.3


Carbamazepine 3753 149 96


Estriol 1956 35 98.2



Estrone 2030 14 99.3



17-β- estradiol 3093 25 99.2



Triclosan 3033 30 99

4-n-nonylphenol 2058 41 98


Appendix

162




Metronidazole 1644 330 79.9

Fenoprop 3200 1662 48



Naproxen 3889 1003 74.2


Ibuprofen 3489 237 93.2




Estriol 1602 2 99.9

Pentachlorophenol 2757 275 90


Estrone 1722 48 97.2

Bisphenol A 2606 53 98


17-β- estradiol 2394 33 98.6






Appendix

163





Fenoprop 2485 2381 4.2



Naproxen 3618 1919 47

Primidone 2460 221 91

Ibuprofen 2564 50 98




Estriol 1951 61 96.9



Estrone 1966 27 98.6



17-β- estradiol 2966 3 99.9






Appendix

164


Compound Feed Permeate Removal (%)



Fenoprop 2041 1974 3.3



Naproxen 2976 1142 61.6






Estriol 1564 116 92.6



Estrone 1515 11 99.3



17-β- estradiol 2234 4 99.8

17-β- estradiol-17 acetate 3194 65 98


Triclosan 2083 100 95.2


Appendix

165

Table 16: Trace organics concentration and removal efficiency by PAC - MBR treatment

with 0.5 g PAC /L concentration.





Fenoprop 2970 216 92.7



Naproxen 3692 44 98.8






Estriol 1436 121 91.6



Estrone 1694 17 99



17-β- estradiol 2160 0 100

17-β- estradiol-17 acetate 3096 0 100





Appendix

166





Fenoprop 3006 413 86.3

Ketoprofen 1800 143 92


Naproxen 2934 349 88.1





Gemfibrozil 2031 41 98

Estriol 1707 24 98.6



Estrone 2124 21 99



17-β- estradiol 2767 7 99.8






Appendix

167


Compound Feed Permeate Removal (%)



Fenoprop 3263 750 77



Naproxen 3742 535 85.7






Estriol 1420 30 97.9



Estrone 1679 19 98.8



17-β- estradiol 2231 2 99.9



Triclosan 2920 31 99



Appendix

168





Fenoprop 2648 669 74.7



Naproxen 3426 485 85.8

Primidone 885 0 100





Estriol 1495 16 98.9



Estrone 1701 45 97.3



17-β- estradiol 2454 3 99.9






Appendix

169





Fenoprop 3687 1500 59.3



Naproxen 4573 280 93.9


Ibuprofen 3649 157 95.7




Estriol 2196 315 85.6



Estrone 2393 41 98.3


17-α ethinylestradiol 3798 75 98

17-β- estradiol 3632 13 99.6


4-tert-octylphenol 3026 60 98


4-n-nonylphenol 1476 73 95


Appendix

170





Fenoprop 3668 2484 32.3



Naproxen 4787 98 97.9


Ibuprofen 4130 150 96.4


Carbamazepine 3364 268 92


Estriol 2373 48 98



Estrone 2455 16 99.3



17-β- estradiol 3559 35 99






Appendix

171





Fenoprop 2645 1420 46.3



Naproxen 3412 46 98.7






Estriol 1368 28 97.9



Estrone 1740 221 87.3



17-β- estradiol 2213 88 96






Appendix

172





Fenoprop 2635 1866 29.2



Naproxen 3529 56 98.4






Estriol 1594 31 98



Estrone 1995 3 99.9



17-β- estradiol 2640 7 99.7






Appendix

173





Fenoprop 2723 1930 29.1



Naproxen 3549 80 97.8






Estriol 1693 52 96.9



Estrone 2327 56 97.6



17-β- estradiol 2799 7 99.7



Triclosan 2758 133 95.2



Appendix

174

APPENDIX B

PUBLICATION RESULTED FROM THIS RESEARCH

Accepted

1. NGUYEN, L. N., HAI, F. I., KANG, J., PRICE, W. E. & NGHIEM, L. D.

Removal of trace organic contaminants by a membrane bioreactor – granular

activated carbon (MBR-GAC) system, Bioresource Technology, 2012. 113: p.

169-173.

In preparation


Coupling granular activated carbon adsorption with membrane bioreactor

treatment for the removal of trace organic contaminants: breakthrough behavior

of persistent and hydrophilic compounds, CHEMOSPHERE.


Removal of emerging trace organic contaminants by MBR-based hybrid

treatment processes, Bioresource Technology.

3. NGUYEN, L. N., HAI, F. I., NGHIEM, L. D., KANG, J., PRICE, W. E., &

Yamamoto, K. Enhancing removal of trace organic contaminants by powdered

activated carbon dosing into membrane bioreactors— can long term stable

performance be achieved?, Journal of Membrane Science.

4. NGUYEN, L. N., HAI, F. I., NGHIEM, L. D., KANG, J., PRICE, W. E., NGO,

H. H., & Guo, W. Comparison between sequential and simultaneous

applications of activated carbon with membrane bioreactor for micropollutant

removal, Desalination.

Conference presentation

1. NGUYEN, L. N., HAI, F. I., KANG, J., PRICE, W. E. & NGHIEM, L. D. (oral

presentation) Removal of trace organic contaminants by a membrane bioreactor

– granular activated carbon (MBR-GAC) hybrid system. The 4th

Challenges in

Environmental Sciences and Engineering conference in Tainan City, Taiwan

(25 - 30 September 2011).

2. NGUYEN, L. N., HAI, F. I., KANG, J., PRICE, W. E. & NGHIEM, L. D. (oral

presentation) Removal of trace organic contaminants by membrane filtration

Appendix

175

technology. Micropol & Ecohazard conference, Sydney, Australia (11 - 13 July

2011).


Removal of emerging trace organic contaminants by MBR-based hybrid

treatment processes. The 5th

Challenges in Environmental Sciences and

Engineering conference in Melbourne, Australia (9 - 13 September 2012)

(accepted).


Coupling powdered activated carbon (PAC) adsorption with membrane

bioreactor (MBR) treatment for enhanced removal of trace organics.

Euromembrane 2012, London, UK, (23 - 27 September 2012) (accepted).

2012 Sequential and simultaneous application of activated

Documents

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