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