UNIVERSITI PUTRA MALAYSIA

SCALED-DOWN BIOGAS PRODUCTION FROM

ANAEROBIC TREATMENT OF PALM OIL MILL EFFLUENT

MOHAMAD FIRWANCE BIN BASRI

FK 2007 3

SCALED-DOWN BIOGAS PRODUCTION FROM ANAEROBIC TREATMENT OF PALM OIL MILL EFFLUENT

By

MOHAMAD FIRWANCE BIN BASRI

Thesis Submitted to the School of Graduate Studies, Universiti Putra Malaysia, in Fulfilment of the Requirement for the Degree of Master of Science

March 2007

Dedicated to:

My Loving and Caring Wife

Ernaleza Mahsum

My Cute, Funny and Sweet Children

Muhammad Furqan and Muhammad Farhan

My Loving and Supporting Parents and Parent-in Laws

My father and father-in law who nurtured and gave me strong spirit

Basri Mir and Mahsum Mohd Nooh

and

My mother and mother-in law who cares and understands

Salmiah Mohd Zain and Dayang Norimah Datu Shamsuddin

My Beloved Sister and Brothers

Haslinda, Ahmad Qadri and Mohd Syukri

My Sporting Sisters and Brother-in Laws:

Ernie, Erma, Ermie, Erda, Pija and Pijul

And to ALL

ii

Abstract of thesis presented to the Senate of Universiti Putra Malaysia in fulfilment of the requirement for the Degree of Master of Science

SCALED-DOWN BIOGAS PRODUCTION FROM ANAEROBIC TREATMENT OF PALM OIL MILL EFFLUENT

By

MOHAMAD FIRWANCE BIN BASRI

March 2007

Chairman: Professor Mohd. Ali Hassan, PhD

Faculty: Engineering

This study is an extension of a 500 m3 methane recovery test plant study located at

Serting Hilir Palm Oil Mill, Negeri Sembilan conducted by our research group on

anaerobic treatment of palm oil mill effluent (POME). Biomass washout has become

one of the problems faced by our research group because of the continuous mixing of

effluent during anaerobic treatment of POME. Therefore, in this study, anaerobic

POME treatment using a scaled down 50 L bioreactor which mimics the 500 m3

bioreactor was carried out to improve biogas production with and without biomass

sedimentation.

Three series of experiments were conducted under different conditions in terms of

biomass sedimentation applied to the system. The first experiment was operated

under semi-continuous mode whereas the second and third experiments were

operated based on mix and settle mode system. As expected, by retaining biomass in

the bioreactor, there was an improvement on the anaerobic process as the system

from the second and third experiments were be able to operate at organic loading rate

iii

(OLR) of 3.5 and 6.0 kg COD/m3/d, respectively while the first experiment only

achieved OLR of 3.0 kg COD/m3/d. At these OLR value, the hydraulic retention time

(HRT) obtained was 10 days in the third experiment and followed by the first and

second experiments with 15 days of HRT. The highest biogas production was

achieved from the third experiment which was 2.42 m3/m3 of reactor/d. This was

followed by second and first experiments which were 1.55 and 1.20 m3/m3 of

reactor/d respectively. The highest methane production rate was also obtained in the

third experiment with 0.992 m3/m3 of reactor/d as compared to the second and first

experiments which were 0.655 and 0.553 m3/m3 of reactor/d, respectively. For COD

removal, more than 90% of COD was removed for all of the experiments.

The experimental data for the first experiment was applied to the two-stage

mathematical model of acidogenesis and methanogenesis which were developed by

previous researchers. The first experimental data was used because it represented the

actual scenario on how the methane recovery test plant was operated in which

biomass washout was taken into consideration. In modelling the behavior of the

anaerobic digestion process, the mathematical model was used to simulate the

methane production from the anaerobic treatment of POME. From the simulation

result, the model was shown to be satisfactory for simulating methane production

from the anaerobic treatment of POME.

iv

Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia sebagai memenuhi keperluan untuk ijazah Master Sains

PENURUNAN SKALA PENGHASILAN BIOGAS DARI RAWATAN ANAEROBIK EFLUEN KILANG MINYAK SAWIT

Oleh

MOHAMAD FIRWANCE BIN BASRI

Mac 2007

Pengerusi: Profesor Mohd. Ali Hassan, PhD

Fakulti: Kejuruteraan

Kajian ini adalah lanjutan kepada kajian 500 m3 Loji Ujian Pemulihan Metana yang

terletak di Kilang Sawit Serting, Negeri Sembilan yang dijalankan oleh kumpulan

penyelidikan kami untuk rawatan anaerobik efluen kilang minyak sawit. Kehilangan

biojisim semasa rawatan anaerobik efluen kilang minyak sawit telah menjadi salah

satu dari masalah yang dihadapi oleh kumpulan kami disebabkan oleh pencampuran

efluen yang selanjar. Oleh yang demikian, di dalam kajian ini, rawatan anaerobik

efluen kilang minyak sawit telah dijalankan menggunakan bioreaktor 50 L yang

menyerupai bioreaktor 500 m3 bagi memperbaiki penghasilan biogas pada keadaan

pemendakan biojisim dan tanpa pemendakan biojisim.

Sebanyak tiga siri eksperimen telah dijalankan pada keadaan berbeza dari segi

pemendakan biojisim yang diaplikasikan kepada sistem tersebut. Eksperimen

pertama telah dijalankan di bawah mod separa selanjar manakala eksperimen kedua

dan ketiga dijalankan berdasarkan sistem mod campur dan mendak. Seperti yang

dijangkakan, dengan mengekalkan biojisim di dalam bioreaktor, ianya dapat

v

memperbaiki proses anaerobik kerana sistem dari eksperimen kedua dan ketiga dapat

dijalankan pada kadar bebanan organik 3.5 dan 6.0 kg COD/m3/hari masing-masing

manakala eksperimen pertama hanya memperolehi kadar bebanan organik 3.0 kg

COD/m3/hari sahaja. Pada nilai kadar bebanan organik ini, masa tahanan hidraulik 10

hari diperolehi bagi eksperimen ketiga dan diikuti oleh eksperimen pertama dan

kedua iaitu dengan masa penahanan hidraulik 15 hari. Kadar penghasilan biogas

tertinggi diperolehi dari eksperimen ketiga iaitu 2.42 m3/m3 reaktor/hari. Ini diikuti

oleh eksperimen kedua dan pertama iaitu 1.55 dan 1.20 m3/m3 reaktor/hari masing-

masing. Kadar penghasilan metana tertinggi juga diperolehi dari eksperimen ketiga

iaitu 0.992 m3/m3 reaktor/hari berbanding dengan eksperimen kedua dan pertama

iaitu 0.655 dan 0.553 m3/m3 reaktor/hari masing-masing. Bagi penyingkiran COD,

lebih dari 90% COD disingkirkan untuk semua eksperimen.

Data eksperimen pertama telah diaplikasikan kepada model matematik dua peringkat

iaitu asidogenesis dan metanogenesis yang mana telah dibangunkan oleh penyelidik-

penyelidik sebelum ini. Data eksperimen ini telah digunakan adalah kerana ianya

menyerupai senario sebenar bagaimana Loji Ujian Pemulihan Metana telah

dikendalikan yang mana mengambil kira kehilangan biojisim. Di dalam permodelan

sifat proses pencernaan anaerobik, model matematik telah digunakan untuk

mensimulasikan penghasilan metana dari rawatan anaerobik efluen kilang minyak

sawit. Dari keputusan simulasi, model tersebut telah menunjukkan keputusan yang

memuaskan untuk mensimulasikan penghasilan metana dari rawatan anaerobik

efluen kilang minyak sawit.

vi

ACKNOWLEDGEMENTS

I would like to express my gratitude to the members of my supervisory committee,

Professor Dr. Mohd Ali Hassan (Chairman), Professor Dr. Azni Idris and Professor

Dr. Yoshihito Shirai for their invaluable guidance, constructive comments and

assistance during my study, without their support and criticism I would not have

been able to complete this thesis.

I am also deeply indebted to Dr. Shahrakbah Yacob for his assistance during the

conduct of the experiments and comments during my thesis writing up process. Not

forgetting to all the Environmental Biotechnology Group members especially Serting

Group for their assistance in the experiments.

My heartfelt gratitude and utmost love to my wife, Ernaleza Mahsum for her support,

encouragement and patience. For my children Muhammad Furqan and Muhammad

Farhan, who enliven my life. Last but not least, my million thanks to my parents,

Basri Mir and Salmiah Mohd Zain, my sister, twin brothers and family in laws for

their pray and support. Thank you very much. And above all, to ALLAH, the most

gracious and most merciful who made all things possible.

vii

I certify that an Examination Committee has met on the 23rd March 2007 to conduct the final examination of Mohamad Firwance bin Basri on his Master of Science thesis entitled “Scaled-Down Biogas Production from Anaerobic Treatment of Palm Oil Mill Effluent (POME)” in accordance with Universiti Pertanian Malaysia (Higher Degree) Act 1980 and Universiti Pertanian Malaysia (Higher Degree) Regulations 1981. The Committee recommends that the Candidate be awarded the relevant degree. Members of the Examination Committee are as follows:

Johari Endan, PhD Associate Professor Faculty of Engineering Universiti Putra Malaysia (Chairman) Tey Beng Ti, PhD Associate Professor Faculty of Engineering Universiti Putra Malaysia (Internal Examiner) Ling Tau Chuan, PhD Senior Lecturer Faculty of Graduate Studies Universiti Putra Malaysia (Internal Examiner) Abdul Latif Ahmad, PhD Professor School of Chemical Engineering Universiti Sains Malaysia (External Examiner)

________________________________ HASANAH MOHD. GHAZALI, PhD Professor/Deputy Dean

School of Graduate Studies Universiti Putra Malaysia

Date:

viii

This thesis submitted to the Senate of Universiti Putra Malaysia and has been accepted as fulfilment of the requirement for the Degree of Master of Science. The members of the Supervisory Committee are as follows:

Mohd Ali Hassan, PhD Professor Faculty of Engineering Universiti Putra Malaysia (Chairman) Azni Idris, PhD Professor Faculty of Engineering Universiti Putra Malaysia (Member) Yoshihito Shirai, PhD Professor Kyushu Institute of Technology (KIT) Japan (Member)

__________________________ AINI IDERIS, PhD Professor/Dean School of Graduate Studies Universiti Putra Malaysia

Date: 14 JUNE 2007

ix

DECLARATION

I hereby declare that the thesis is based on my original work except for quotations and citations, which have been duly acknowledged. I also declare that it has not been previously or concurrently submitted for any other degree at UPM or other institutions.

_________________________________

MOHAMAD FIRWANCE BIN BASRI

Date:

x

TABLE OF CONTENTS

Page DEDICATION ii ABSTRACT iii ABSTRAK v ACKNOWLEDGEMENTS vii APPROVAL viii DECLARATION x LIST OF TABLES xiii LIST OF FIGURES xiv LIST OF ABBREVIATIONS xvii CHAPTERS

1 INTRODUCTION 1 2 LITERATURE REVIEW 2.1 Palm Oil 4 2.2 Palm Oil Mill Effluent (POME) 4 2.3 Anaerobic Decomposition 7 2.3.1 Mechanism 7 2.3.2 Acidogenic Microorganisms 11 2.3.3 Methanogenic Microorganisms 11 2.4 Factors Affecting Anaerobic Treatment 12 2.4.1 Rate-Limiting Processes 12 2.4.2 Temperature 14 2.4.3 pH, Acidity and Alkalinity 15 2.4.4 Other Factors 16 2.5 Anaerobic Treatment System 17 2.5.1 Conventional System 17 2.5.2 High-rate System 18 2.5.3 Hybrid Technology 18 2.6 Biogas 19 2.6.1 Production 19 2.6.2 Cleaning and Separation 19 2.6.3 Utilization 20 2.7 Modeling of Anaerobic Digestion 21 2.7.1 History of the Model Development 21 2.7.2 Types of Anaerobic Model 22 3 GENERAL MATERIALS AND METHODS 3.1 Chemical Reagents 24 3.2 Palm Oil Mill Effluent (POME) 24 3.3 POME Sludge 24 3.4 Bioreactor Setup and Operation 25 3.5 Experimental Design 26 3.6 Analytical Methods 29

xi

3.6.1 Chemical Oxygen Demand (COD) 29 3.6.2 Volatile Fatty Acids (VFA) Determination 29 3.6.3 Total Solids (TS) 30 3.6.4 Biogas Measurement 30 3.7 Modelling and Simulation 31 3.7.1 Method of calculation 31 4 DESIGN, FABRICATION AND MIXING

CHARACTERISTIC OF 50 L BIOREACTOR FOR BIOGAS PRODUCTION FROM ANAEROBICALLY TREATED POME

4.1 Introduction 33 4.2 Materials And Methods 34 4.2.1 Materials and Instruments 34 4.2.2 Determination of Mixing Time 34 4.3 Results and Discussion 35 4.3.1 Configuration of Bioreactors 35 4.3.2 Bioreactor Sections and Parts 37 4.3.3 Mixing Time 45 4.3.4 Mixing Patterns 48 4.4 Conclusions 51 5 ANAEROBIC PRODUCTION OF BIOGAS AND

MODELLING OF METHANE PRODUCTION FROM PALM OIL MILL EFFLUENT

5.1 Introduction 52 5.2 Materials And Methods 53 5.2.1 Chemical, POME and POME Sludge 53 5.2.2 Characteristics of POME 53 5.2.3 Anaerobic Treatment of POME with and without

Biomass Retention 53

5.2.4 POME Analyses 55 5.2.5 Model assumptions 57 5.2.6 Model Calculation and Solution 57 5.3 Results and Discussion 58 5.3.1 Characteristics of POME 58 5.3.2 Anaerobic Treatment of POME for Biogas

Production 59

5.3.3 Modelling of Methane Production 80 5.4 Conclusions 83 6 SUMMARY, CONCLUSIONS AND SUGGESTIONS FOR

FUTURE WORK

6.1 Summary 85 6.2 Conclusions 87 6.3 Suggestions for Future Work 87 REFERENCES 90 APPENDICES 98 BIODATA OF THE AUTHOR 101

xii

LIST OF TABLES

Table Page

2.1 Characteristics of POME 6

3.1 Method of calculation for one time increment 32

4.1 Configuration of the bioreactors 36

4.2 Time required for well mixing (pH convergence) 46

5.1 Classification and conditions of experiments 55

5.2 Raw POME conditions 58

5.3 POME sludge initial conditions 58

5.4 Achievement of biogas and methane production 63

5.5 Model parameter values 82

xiii

LIST OF FIGURES Figure Page

2.1 Schematic flow diagram of processing normally carried out in a palm oil mill

5

2.2 Schematic diagram of anaerobic digestion of organic compounds 8

2.3 Biogas utilization options 20

3.1 The 50 L bioreactor set-up 27

3.2 The piping on the top of the 50 L bioreactor 27

3.3 Experimental design for this study

28

4.1 Configuration of the bioreactors 36

4.2 Main vessel of the 50 L bioreactor 37

4.3 Gas draft of the 50 L bioreactor 38

4.4 Main vessel of the 500 m3 pilot plant 38

4.5 Mixing pumps of the 50 L bioreactor 39

4.6 Mixing pumps of the 500 m3 pilot plant 39

4.7 Feeding/Recycle pump of the 50 L bioreactor 40

4.8 Feeding pump of the 500 m3 pilot plant 41

4.9 Sludge recycle pump of the 500 m3 pilot plant 41

4.10 (a) Copper spiral 42

4.10 (b) Heater 42

4.11 Wet gas meter 43

4.12 Biogas outlet nozzles 43

4.13 T-distributor of the 50 L bioreactor 44

4.14 T-distributor of the 500 m3 pilot plant 44

4.15 Switch box/Control panel 45

xiv

4.16 (a) pH profile versus time for horizontal mixing 47

4.16 (b) pH profile versus time for vertical mixing 47

4.16 (c) pH profile versus time for combination of horizontal and vertical mixing

48

4.17 (a) Liquid flow for horizontal mixing (top and horizontal views) 49

4.17 (b) Liquid flow for vertical mixing (top and horizontal views) 50

4.17 (c) Liquid flow for combination of both mixing (horizontal views) 50

5.1 Schematic diagram of bioreactor operated without biomass sedimentation

56

5.2 Schematic diagram of bioreactor operated with biomass sedimentation

56

5.3 (a) Relationship between biogas production rates with OLR over time (1st Experiment)

60

5.3 (b) Relationship between biogas production rates with OLR over time (2nd Experiment)

60

5.3 (c) Relationship between biogas production rates with OLR over time (3rd Experiment)

61

5.4 (a) Methane and biogas production rates over time (1st Experiment) 64

5.4 (b) Methane and biogas production rates over time (2nd Experiment) 65

5.4 (c) Methane and biogas production rates over time (3rd Experiment) 65

5.5 (a) Relationship between biogas and methane production with total COD removed (1st Experiment)

67

5.5 (b) Relationship between biogas and methane production with total COD removed (2nd Experiment)

68

5.5 (c) Relationship between biogas and methane production with total COD removed (3rd Experiment)

68

5.6 (a) Raw POME COD, treated POME COD and OLR versus time (1st Experiment)

71

5.6 (b) Raw POME COD, treated POME COD and OLR versus time (2nd Experiment)

72

xv

5.6 (c) Raw POME COD, treated POME COD and OLR versus time (3rd Experiment)

72

5.7 (a) VFA effect on biogas and methane production (1st experiment) 74

5.7 (b) VFA effect on biogas and methane production (2nd experiment) 74

5.7 (c) VFA effect on biogas and methane production (3rd experiment) 75

5.8 (a) HRT profile and OLR increment over time (1st Experiment) 77

5.8 (b) HRT profile and OLR increment over time (2nd Experiment) 78

5.8 (c) HRT profile and OLR increment over time (3rd Experiment) 78

5.9 TS profiles of the bioreactor content 79

5.10 (a) pH profile for raw POME and treated POME (1st Experiment) 80

5.10 (b) pH profile for raw POME and treated POME (2nd Experiment) 81

5.10 (c) pH profile for raw POME and treated POME (3rd Experiment) 81

5.11 Experimental and simulation results of methane production 83

xvi

LIST OF ABBREVIATIONS

μ Specific growth rate

μ1 Acidogenic bacteria specific growth rate

μ2 Methanogenic bacteria specific growth rate

μmax1 Maximum acidogenic bacteria specific growth rate

μmax2 Maximum methanogenic bacteria specific growth rate

A Total acetic acid concentration

Ao Influent total acetic acid concentration

AH Unionized acetic acid concentration

AFBR Anaerobic fixed bed reactors

AN Ammoniacal Nitrogen

APB Acid producing bacteria

BOD Biological oxygen demand

COD Chemical oxygen demand

CSTR Continuous stirred tank reactor

D Dilution rate

D Diameter

EFB Empty fruit bunch

F Volumetric loading rate

FELDA Federal Land Development Authority

FF Fixed film

FFB Fresh fruit bunch

GHG Greenhouse gases

GI Galvanize iron

xvii

H Height

H+ Hydrogen ion concentration

HRT Hydraulic retention time

Ke Dissociation constant for acetic acid at 35oC

Kd1 Decay constant for acidogenic bacteria

Kd2 Decay constant for methanogenic bacteria

Kim Inhibition constant of acetic acid (expressed as unionized acid) on methane production

Kix1 Inhibition constant of acidogenic bacteria growth (expressed as unionized acetic acid)

Kix2 Inhibition constant of methanogenic bacteria growth (expressed as unionized acetic acid)

Km Saturation constant of methane production (expressed as unionized acetic acid)

Kx1 Saturation constant in the expression of acidogenic bacteria grwoth

Kx2 Saturation constant for the methanogenic bacteria growth (expressed as unionized acetic acid)

O & G Oil and grease

OLR Organic loading rate

ppm Part per million

POME Palm oil mill effluent

PVC Polyvinyl chloride

S Glucose equivalent concentration

So Influent glucose equivalent concentration

SHI Sumitomo Heavy Industries

SMAHS Submerged membrane adsorption hybrid system

SS Suspended solids

xviii

xix

STR Stirred tank reactor

t Time

TN Total nitrogen

TS Total solids

UASB Up-flow anaerobic sludge blanket

UASFF Up-flow anaerobic sludge blanket fixed film

v/v Volume per volume

VFA Volatile fatty acid

Vmmax Maximal production rate of methane per weight of methanogenic

bacteria per day

VR Bioreactor working volume

X1 Acidogenic bacteria concentration

X2 Methanogenic bacteria concentration

Xo1 Influent acidogenic bacteria concentration

Xo2 Influent methanogenic bacteria concentration

Yas Maximum yield of glucose conversion to acid

Yso Maximum yield of glucose

Yx1s Maximum growth yield of acidogenic bacteria on glucose

Yx2a Maximum growth yield of methanogenic bacteria on acetic acid

CHAPTER 1

INTRODUCTION

Palm oil is one of the main commodities in world trade. Malaysia was the largest

palm oil producer in the world in 2004 with 12.6 million tonnes of production, which

was about 52 per cent of the total world palm oil production (MPOB, 2005a). The

total exports of oil palm products produced by Malaysia, constituting palm oil, palm

kernel oil, palm kernel cake, oleochemicals and finished products increased

marginally by 3.1% or 0.53 million tonnes from 16.82 million tonnes in 2003 to

17.35 million tonnes in 2004 (MPOB, 2005b).

With such a huge production, palm oil industry generate large amount of by-products

such as shells, fibers, kernels, empty fruit bunches (EFB) and palm oil mill effluent

(POME). Basically, most of these wastes can be used as a renewable energy source

and other value-added by-products. POME is the largest palm oil industry by-

products, it is high in chemical oxygen demand (COD) and biological oxygen

demand (BOD) content and could create environmental problems if it is not properly

treated. On the other hand, it is a potential renewable energy source if it is treated

anaerobically to produce methane. Methane can be used as fuel to generate

electricity.

In Malaysia, various treatments have been used to treat POME in order to meet the

department of environmental (DOE) discharge standard. Anaerobic treatment of

POME is widely used because of its low operation cost. During anaerobic treatment,

large amount of methane (CH4) and carbon dioxide (CO2) are produced, which is

harmful to the environment but can be used as renewable energy source. The

uncontrolled release of CH4 and CO2 to the atmosphere can cause greenhouse gases

(GHG) effect.

Biogas is a mixture of colourless flammable gases obtained by anaerobic digestion of

plant based (lignocellulosic) organic waste materials and also from other type of

organic waste such as cow dung, pig slurry, effluent from slaughter house and

landfill. Biogas from anaerobic decomposition comprising methane, carbon dioxide

and a small amount of nitrogen (N2), hydrogen (H2) and hydrogen sulfide (H2S)

(Price, 1985).

Currently, our research group has conducted and still pursuing research on anaerobic

treatment of POME for biogas production. A 500 m3 pilot plant for biogas

production research was constructed in year 2004 (Yacob, 2005). As for this study, a

scaled down 50 L bioreactor was designed and fabricated based on the design of the

500 m3 pilot plant bioreactor. By having a small scale bioreactor, different operations

parameters can be tested and studied in order to achieve optimum operations.

Moreover, it is much easier to change and manipulate operational conditions for a

small bioreactor as compared with a large scale bioreactor. As reported by Yacob

(2005), biomass washout from the 500 m3 during anaerobic treatment of POME has

become one of the problems faced in his study because of the continuous re-

circulation of effluent. This has caused fully suspended of solid which then

contributed to biomass washout. Yacob (2005) recommended that the mixing should

be stopped at least 2-3 hours before loading to encourage the solids to settle down

thus reducing the washout of biomass. Therefore, in this study, series of experiments

2

3

were conducted at different conditions of biomass sedimentation which could

improve biogas production by increasing anaerobic POME treatment performance

using the 50 L scaled down bioreactor.

Theoretically, anaerobic digestion can be modelled and formulated mathematically

using differential equations. Even though anaerobic digestion is a complex process,

model simplicity is always taken as an approach to solve the modeling of the process.

Currently, numbers of anaerobic models had been published and widely accepted

(Havlik et al., 1986; Moletta et al., 1986). These models can be used to simulate

methane production rate, pH, alkalinity and so on of anaerobic digestion.

In this study, the objectives are:

1. To optimize anaerobic treatment of POME in the 500 m3 pilot plant to

improve biogas production from anaerobic treatment of POME with and

without biomass sedimentation by using a 50 L bioreactor.

2. To simulate biogas (CH4) production of anaerobic treatment of POME

using established mathematical model.

CHAPTER 2

LITERATURE REVIEW

2.1 Palm Oil

Palm oil is extracted from the palm fruits Elaeis guineensis. In its virgin form, the oil

is bright orange-red due to the high content of carotene. Malaysia is currently the

world’s largest palm oil exporters in the world. In 2004, it produces 12.6 million

tonnes of palm oil, which is about 52 per cent of the total world palm oil production

(MPOB, 2005a). Malaysia is so lucky to be the largest producer of this commodity

because palm oil is one of the main sources of edible oils in the world besides corn

oil, coconut oil, soybean oil and olive oil.

2.2 Palm Oil Mill Effluent (POME)

In the palm oil extraction process, a considerable amount of water is used

(Agamuthu, 1995), leading to the generation of large volumes of wastewater, known

as palm oil mill effluent (POME). Figure 2.1 shows the normal schematic flow

diagram of a palm oil mill. During palm oil extraction, about 1.5 tonnes of palm oil

mill effluent is produced per tonne of fresh fruit bunch (FFB) processed (Ahmad et

al., 2003). POME is generated from the sterilization and clarification processes and

in hydrocylone operation where the broken shells are separated from the kernels

(Basiron and Darus, 1995) as can be seen in Figure 2.1.

4

Sterilization

Stripping

Digestion

Pressing

Clarification Tank

Sludge

Separator

Oil Sludge waste

Empty bunches Mulching

Sterilization condensate

Nuts

Hydrocyclone Waste

Kernel

Centrifuge purification

Vacuum drying

Storage

Oil Shell for

boiler fuel

Nut cracker

Fiber for boiler fuel

Fresh Fruit Bunches

Figure 2.1: Schematic flow diagram of processing normally carried out in a palm oil mill (Basiron and Darus, 1995)

POME is a thick brownish liquid with average chemical oxygen demand (COD) and

biochemical oxygen demand (BOD) values of 50 000 and 25 000 mg/l, respectively.

It is discharged at a temperature of 80-90oC and has a pH typically between 4 and 5

(Ma and Halim, 1988; Polprasert, 1989; Singh et al., 1999). The characteristics of

POME are shown in Table 2.1 (Basiron and Darus, 1995).

5