pretreatment of instant coffee wastewater by coagulation and

PRETREATMENT OF INSTANT COFFEE WASTEWATER BY

COAGULATION AND FLOCCULATION

ENG WEE EAN

UNIVERSITI TEKNOLOGI MALAYSIA

iii

Dedicated to my beloved parents…

iv

ACKNOWLEDGEMENTS

The author would like to express his sincere appreciation and gratitude to his

supervisor, Dr. Mohd. Ariffin Bin Abu Hassan, of Department of Chemical

Engineering, Faculty of Chemical and Natural Resources Engineering, Universiti

Teknologi Malaysia (UTM) for his advice, guidance, support and encouragement

throughout his research study.

Special thanks to the staffs of the Faculty of Chemical and Natural Resources

Engineering, Universiti Teknologi Malaysia (UTM), especially the technician and

lab assistants for their assistance and cooperation in carrying out the experimental

studies. The author also appreciated En. Zukarnai from M/s. Dan Kaffe (M) Sdn Bhd

for his cooperation in completing the study.

The author also like to express his grateful to the course-mates for their helps

and supports in this study. At the last but not least, the encouragement, support and

love from parents and family members are sincerely acknowledged.

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ABSTRACT

This study investigated the performance and effectiveness of coagulation and

flocculation by using aluminum sulfate, ferric chloride and chitosan as a pretreatment

for instant coffee wastewater. The removal of total suspended solids (TSS), turbidity,

chemical oxygen demand (COD) and color by jar tests were used to determine the

optimum dosage and pH. Optimum conditions for aluminum sulfate and ferric

chloride was 1000 mg/L at pH 7, while for chitosan was 100 mg/L at pH 6. The

dosage of chitosan was 10 times much lesser as it had the higher charge density.

Chitosan exhibited the best result for turbidity and TSS removal by 96.95% and

91.43%, respectively. This was followed by ferric chloride that removed 95.38%

turbidity and 91.43% TSS; and aluminum sulfate with 87.65% turbidity and 88.57%

TSS removal. At the same time, ferric chloride was the best coagulant for color and

COD removal, with 95% and 66.45%, respectively. This was followed by the

aluminum sulfate with 90% color and 56% COD removal; and chitosan that removed

88.55% color and 46.46% COD. Chitosan produced the faster aggregation of colloids,

with the lowest volume of sludge of 60 mL. This was followed by aluminum sulfate

with 87 mL and ferric chloride with 103 mL. The cost of ferric chloride using per

day, RM20,340 was the lowest, which was 16.8% lower than aluminum sulfate and

119.8% lower than chitosan. Overall, all coagulants can be used for pretreatment of

coffee wastewater, with ferric chloride was preferable.

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ABSTRAK

Kajian ini mengkaji prestasi dan keberkesanan koagulasi dan flokulasi

dengan menggunakan aluminum sulfide, ferric chloride dan kitosan sebagai rawatan

awal untuk air sisa kilang kopi segera. Pengurangan jumlah pepejal terampai (TSS),

kekeruhan, warna dan keperluan oksigen kimia (COD) melalui ujian balang telah

digunakan untuk menentukan dos dan pH optimal. Keadaan optimal bagi aluminum

sulfate dan ferric chloride adalah 1000 mg/L dengan pH 7, manakala untuk kitosan

adalah 100 mg/L dengan pH 6. Dos yang diperlukan untuk kitosan adalah 10 kali

ganda lebih rendah kerana kitosan mempunyai ketumpatan cas yang lebih tinggi.

Kitosan menunjukkan keputusan yang terbaik untuk pengurangan kekeruhan dan

TSS dengan pengurangan 96.95% dan 91.43% masing-masing. Ini diikuti dengan

ferric chloride yang mengurangkan 95.38% kekeruhan dan 91.43% TSS; dan

aluminum sulfate dengan pengurangan 87.65% kekeruhan dan 88.57% TSS. Pada

masa yang sama, ferric chloride merupakan agen koagulasi terbaik untuk

pengurangan warna dan COD, dengan nilai 95% dan 66.45%. Ini diikuti dengan

aluminum sulfate dengan pengurangan 90% warna dan 56% COD; dan kitosan yang

mengurangkan 88.55% warna dan 46.46% COD. Kitosan menghasilkan

penggumpalan pepejal yang paling cepat, dengan isipadu enapan sebanyak 60 mL.

Ini diikuti dengan aluminum sulfate pada 87 mL dan ferric chloride pada 103 mL.

Kos ferric chloride yang digunakan sehari, RM20,340 adalah yang terendah, dengan

16.8% lebih rendah daripada aluminum sulfate dan 119.8% daripada kitosan.

Keseluruhannya, semua agen koagulasi berkeupayaan digunakan sebagai rawatan

awal untuk air sisa kopi, dengan ferric chloride adalah terpilih.

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TABLE OF CONTENTS

CHAPTER TITLE PAGE

DECLARATION ii

DEDICATION iii

ACKNOWLEDGEMENTS iv

ABSTRACT v

ABSTRAK vi

TABLE OF CONTENTS vii

LIST OF TABLES x

LIST OF FIGURES xi

LIST OF SYMBOLS xiv

LIST OF APPENDICES xvii

1 INTRODUCTION

1.1. Introduction 1

1.2. Research Background 2

1.3. Problem Statements 5

1.4. Objectives 7

1.5. Scope of Works 7

1.6. Contribution of Study 8

2 LITERATURE REVIEW

2.1. Introduction 9

2.2. Instant (Soluble) Coffee 10

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2.2.1. Production of Instant Coffee 12

2.2.2. Wastewater 15

2.3. Dan Kaffe (M) Sdn Bhd 17

2.3.1. Coffee Processing 18

2.4. Coagulation and Flocculation 20

2.4.1. Colloidal Particles 21

2.4.1.1. Colloidal Stability 22

2.4.1.2. Colloidal Interactions 24

2.4.2. Mechanisms of Coagulation 25

2.4.2.1. Double Layer Compression 26

2.4.2.2. Charge Neutralization 26

2.4.2.3. Sweep Coagulation 27

2.4.2.4. Interparticle Bridging 27

2.5. Coagulants 27

2.5.1. Inorganic Metal Salts 28

2.5.1.1. Aluminum Sulfate 33

2.5.1.2. Ferric Chloride 34

2.5.2. Polyelectrolytes 35

2.5.2.1. Chitosan 39

3 METHODOLOGY

3.1. Introduction 42

3.2. Materials 44

3.2.1. Wastewater Sample 44

3.2.2. Aluminum Sulfate 44

3.2.3. Ferric Chloride 45

3.2.4. Chitosan 45

3.3. Jar Test Experiment 46

3.4. Analytical Methods 51

3.4.1. Turbidity Measurement 51

3.4.2. Total Suspended Solid (TSS) 52

3.4.3. Chemical Oxygen Demand (COD) 53

3.4.4. Color 53

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3.4.5. pH 53

4 RESULTS AND DISCUSSIONS

4.1. Wastewater Characteristics 54

4.2. Effect of Dosage 55



4.2.3. Chitosan 60

4.3. Effect of pH 63



4.3.3. Chitosan 68

4.4. Comparison of Coagulants 71

5 CONCLUSIONS AND RECOMMENDATIONS

5.1. Conclusions 76

5.2. Recommendations 79

REFERENCES 80

APPENDICES 87

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LIST OF TABLES

TABLE NO. TITLE PAGE

2.1 Wastewater analysis from instant coffee industry 16

(Lim, 1999)

4.1 Typical characteristics of the raw wastewater 54

4.2 Optimum conditions for coagulants 71

4.3 Comparison of each coagulant at optimum conditions 72

4.4 Cost comparison of each coagulant 75

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LIST OF FIGURES

FIGURE NO. TITLE PAGE

2.1 Coffee manufacturing process 19

2.2 Structure of electrical double layer 23

2.3 Colloidal interparticulate forces versus distance 25

2.4 Design and operation diagram for alum coagulation 31

(Amirtharajah and Mills, 1982)

2.5 Design and operation diagram for Fe(III) coagulation 32

(Johnson and Amirtharajah, 1983)

2.6 Schematic organic polyelectrolyte bridging model 38

for colloid destabilization (Faust and Aly, 1983)

2.7 Chemical structure of chitosan 39

3.1 Research procedures 43

3.2 Jar test apparatus 47

3.3 Jar tests to determine optimum dosage 49

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3.4 Jar tests to determine optimum pH 50

4.1 Effect of aluminum sulfate dosage on residual parameters 56

4.2 Effect of aluminum sulfate dosage on parameter removals 56

4.3 Effect of ferric chloride dosage on residual parameters 58

4.4 Effect of ferric chloride dosage on parameter removals 59

4.5 Effect of chitosan dosage on residual parameters 61

4.6 Effect of chitosan dosage on parameter removals 61

4.7 Effect of different pH on the residual parameters by 64

aluminum sulfate

4.8 Effect of different pH on the parameter removals by 64

aluminum sulfate


ferric chloride


ferric chloride


chitosan


chitosan

4.13 Jar test using (a) aluminum sulfate, (b) ferric chloride 71

and (c) chitosan

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4.14 Comparison for aluminum sulfate, ferric chloride and 72

chitosan

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LIST OF SYMBOLS

Al3+

- Aluminum ion

Al(H2O)63+

- Aluminum aquometal complexes

Al(OH)2+

- Cationic mononuclear aluminum species

Al(OH)2+ - Cationic mononuclear aluminum species

Al(OH)3 - Aluminum hydroxide

Al(OH)4- - Aluminate ion

Al2(SO4)3 - Aluminum sulfate

Al2(SO4)3.14H2O - Aluminum sulfate 14 hydrate



Al2(OH)24+

- Cationic polynuclear aluminum species

Al6(OH)15+3


Al7(OH)17+4


Al8(OH)20+4


Al13(OH)345+


BOD - Biochemical oxygen demand

oC - Degree celsius

Ca(HCO3)2 - Calcium bicarbonate

CaOH - Calcium hydroxide

CaSO4 - Calcium sulfate

Ci - Initial concentration

Cf - Final concentration

cm - Centimeter

CO2 - Carbon dioxide

COD - Chemical oxygen demand

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-COO- - Anionically charged carboxyl group

-COOH - Carboxyl groups

d - Thickness of the layer surrounding the shear surface

D - Dielectric constant of the liquid

DA - Degree of acetylation

DLVO - Derjagin-Landau-Vervey-Overbeck theory

DD - Degree of deacetylation

DO - Dissolved Oxygen

DOE - Department of Environment

EQA - Environmental Quality Act 1974

Fe3+

- Ferric ion

Fe(OH)3 - Ferric hydroxide

Fe2(SO4)3 - Ferric sulfate

Fe(OH)2+ -

Cationic polynuclear ferric species

Fe2(OH)2+4

-


Fe3(OH)4+5 -


FeCl3 -

Ferric chloride

FeCl3.6H2O

- Ferric chloride 6 hydrate

g - Gram

g/mol - Gram per mole

g/cm3 - Gram per centimeter cubic

HAc - Acetic acid

HCl - Hydrochloric acid

H2O - Water

H2SO4 - Sulfuric acid

H3O+ - Ion hydrogen

ICO - International Coffee Organization

kg - Kilogram

kg/m3 - Kilogram per meter cubic

L - Liter

m3/day - Meter cubic per day

mg - Miligram

mg/L - Miligram per liter

mg/mL - Miligram per mililiter

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mL - Mililiter

M - Molar

NaOH - Sodium hydroxide

-NH2 - Amino group

-NH3+ - Positively charged amino group

NTU - Nephelometric Turbidity Units

-OH - Hydroxyl ion

PtCo - Platinum-cobalt

Q - Flowrate

q - Charge per unit area

RM - Ringgit Malaysia

rpm - Rotation per minute

Si4+

- Silicon ion

TSS - Total suspended solid

UASB - Upflow Anaerobic Sludge Blanket

µm - Micron

Wi - Initial weight

Wf - Final weight

ζ - Zeta potential

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LIST OF APPENDICES

APPENDIX TITLE PAGE

A Apparatus used for analytical methods 87

B Results of jar test using aluminum sulfate to

determine optimum dosage (wide range) 88

B.1 Results of jar test using aluminum sulfate to

determine optimum dosage 89

C Results of jar test using aluminum sulfate to

determine optimum pH 90

D Results of jar test using ferric chloride to


D.1 Results of jar test using ferric chloride to


E Results of jar test using ferric chloride to


F Results of jar test using chitosan to


xviii

F.1 Results of jar test using chitosan to


G Results of jar test using chitosan to


H Results of jar test using aluminum sulfate, ferric

chloride and chitosan 97

I Cost comparison for aluminum sulfate, ferric chloride

and chitosan 99

J T-test statistical analysis 100

CHAPTER 1

INTRODUCTION

1.1 Introduction

Nowadays, coffee is one of the most popular commodities in the developed

world. Supermarkets and coffee shops are always stocked with a plenty supply of

coffee blends and flavors. In the past, the fresh coffee for home and catering brewing

is available by the method of filtration (percolation), infusion or boiling (decoction)

the roast and ground coffee (Clarke and Macrae, 1987). The process will normally

take time with the requirement of some household or catering-type equipment. With

the desire to make coffee instantly by simply mixing a dry or liquid concentrate with

hot water, the product of soluble or instant coffee is marketed worldwide through the

improvement of modern processing technology in food and beverage industry.

Instant or soluble coffee is a beverage that derived from brewed coffee beans.

The coffee is dehydrated into the form of granules or powder through various

manufacturing processes. It can be rehydrated using hot water to provide a drink

similar to brewed coffee. Besides, the instant coffee is also available in the form of

concentrated liquid. Instant coffee is manufactured from coffee beans through a

series of process, including roasting, grinding, extraction, concentration, drying and

2

packing (Clarke and Macrae, 1987). It is normally to produce a soluble powder or

granules, either by spray-drying or freeze-drying technique.

In recent years, the growth of the instant coffee market due to the modern

consumer’s desire for a convenience product has been impressive. Consequently, the

market expansion has led to the production of increasing quantities of wastewater

with high pollution potential and the spent coffee grounds as an unwanted by-product

of instant coffee manufacture (Clarke and Macrae, 1987). Many research studies

have been conducted for the treatment, reusing and recycling of spent coffee grounds

but there is lack of the focus on the instant coffee processing wastewater. The

wastewater of instant coffee industry is primarily generated from cleaning operations

including equipment cleaning and floor washing. It is important to treat the instant

coffee wastewater with proper, effective and economical practices prior to their

discharge into the receiving water.

1.2 Research Background

The first soluble instant coffee was invented by Dr. Satori Kato, a Japanese

chemist in Chicago, and the soluble coffee was first sold to the public at the Pan-

America Exposition of 1901 (Wrigley, 1988). Shortly thereafter, George Washington

developed his own instant coffee process and it was first appeared on the American

market in 1910 (Ukers, 1935). The Nescafé brand that introduced a more advanced

coffee refining process was launched in 1938 (Clarke and Macrae, 1985). On a

global basis, it is estimated that in 1980 about 19% of coffee consumed went into

soluble manufacture and today the countries with the highest total consumption of

instant coffee are, in order, United States of America (USA), United of Kingdom

(UK), Japan, France, Germany and Canada (Clarke and Macrae, 1985). Now, the

instant coffee can be found all over the world and it has been widely used for

decades.

3

Instant coffee comes in three forms: freeze-dried, spray-dried and liquid

coffee extract. A good cup of coffee can be made from the instant coffee with a

number of advantages over fresh brewed coffee. The instant coffee allows the

consumer to make coffee in an ease and convenience way without any equipment

other than a cup and without having to discard any damp grounds. The preparation of

coffee is simple and fast as no time is required for infusing the coffee and it is ready

as soon as the hot water is added. The quality of instant coffee also has grown

dramatically over the years. It stays fresher longer and has long shelf life because

natural coffee, especially in ground form, loses flavor as its essential oils evaporate

over time. In short, the instant coffee is fast, cheap and clean.

Instant coffee has become a product that attracts great attention in the food

and beverage industries of Malaysia. Although Malaysia is not the major country of

coffee plantation and green coffee production, there are more than thirty soluble and

instant coffee manufacturers all around the country. The high technologies are used

to manufacture regular and agglomerated instant coffee in the form of powder or

granules as well as canned liquid coffee. The rapid growth of instant coffee industry

is accompanied by a staggering increase in the amount of wastewater produced. The

major sources of wastewater produced in the instant coffee processing industry

include the water used for the cleaning of extractor, spray dryer, freeze concentrator,

separator, heat exchanger, boiler, evaporator finisher and pasteurizer, washing the

floors and working areas (Lim, 1999).

The International Coffee Organization (ICO) has proposed the Common

Code for the Coffee Community (4C) to create a common global code to cover the

economic, social, and environmental pillars for achieving greater sustainability of

development for coffee industry (Osorio, 2005). From the aspect of environment that

related to coffee processing, there are three main issues to be considered, which

included proper wastewater treatment, utilizing by-products, and conserving energy.

The water quality and aquatic ecosystem will be affected seriously if the high

strength and polluted wastewater from coffee processing is discharging into the

receiving water without any suitable treatment system.

4

Different products of instant coffee with different technology can lead to

different amounts and quality of wastewater produced. The production of instant

coffee gives rise to substantial volumes of wastewaters containing a wide variety of

pollutants. In general, the wastewaters contain higher value of biochemical oxygen

demand (BOD), chemical oxygen demand (COD), total suspended solid (TSS) and

turbidity. The wastewaters also possess a distinctive dark brown color. The pH can

be in a wide range depending of its sources. Coffee wastewater contains high organic

loads which may result in dissolved oxygen depletion in the receiving waters

(Ricardo, 1996). The volume, concentration and composition of the effluent arising

in the manufacturing plant are dependent on the type of product being processed, the

production program, operating methods, design of the processing plant, the design of

water management being applied, and subsequently the amount of water being

conserved (Lawrence et al., 2004).

For instant coffee industry, the wastewater is normally treated by physical

and chemical, biological processes. The pretreatment or primary treatment is a series

of physical and chemical operations, which precondition the wastewater as well as

remove some of the wastes. The treatment is normally arranged in the sequence of

screening, flow equalization, coagulation-flocculation, sedimentation, and dissolved

air flotation (Lawrence et al., 2004). Screening is applied to remove coarse particles

in the influent while flow equalization is a method used to overcome the operational

problems caused by flowrate variations. Coagulation is used to destabilize the stable

suspended solids and colloidal particles while flocculation is used to aggregate the

destabilized particles to form a larger and rapid-settling floc. This normally acts as

preconditioning process for sedimentation and / or dissolved air flotation.

Biological processes have been developed for secondary treatment system to

remove the dissolved and particulate biodegradable components in the wastewater

(Metcalf and Eddy, 2003). Microorganisms are used to decompose the organic

wastes. With regard to different growth types, biological systems can be classified as

suspended growth or attached growth system. Furthermore, it can also be classified

by oxygen utilization: aerobic, anaerobic and facultative. A research study of

5

anaerobic treatment by upflow anaerobic sludge blanket (UASB) process was carried

out by the Nestlé Foods Corporation Purchase, which has one of the largest freeze-

dried coffee plant located in Freehold, New Jersey and generated approximately 760

m3/day of wastewater (Lanting et al., 1988). They study the treatability of coffee

wastewater by using four pilot systems under both mesophilic and thermophilic

conditions. The COD removals were between 49 to 69%.

1.3 Problem Statements

There has been limited research on coagulation and flocculation process for

the pretreatment of instant coffee wastewater as comparing with other food and

beverage industries. Due to the high concentration of organic pollutants and

suspended solids in wastewater of soluble coffee processing, its disposal without an

appropriate treatment into the receiving water has become undesirable because it will

be very dangerous for the water bodies and human health. The wastewater

discharged from any industries in Malaysia must follow the stringent effluent

standard of Environment Quality Act (EQA) 1974. Thus, a proper and effective

treatment system is needed. The pretreatment systems such as coagulation and

flocculation processes play a significant role for overall performance of the

wastewater treatment plant. It is important in reducing most of the suspended solids

and organic matter in the raw wastewater before entering into the secondary

treatment system (Metcalf and Eddy, 2003).

The most widely used coagulants in wastewater treatment are inorganic metal

salts, such as aluminum or iron salts. Aluminum sulfate and ferric chloride have been

extensively used as a primary coagulant in wastewater treatment. This is due to their

effectiveness, cheap, easy to handle and availability (Edzwald, 1993). However, its

best performance and cost-effectiveness can only be achieved during the optimum

conditions of coagulation and flocculation process. It is important not to overdose the

6

coagulants because a complete charge reversal and restabilization of colloid complex

can be occurred.

Recently, there is more attention on the extensive use of aluminum-based

coagulant. Besides producing large amount of sludge, the high level of aluminum

residual in the treated water has raised concern on public health. McLachlan (1995)

discovered that intake of large quantity of alum salt may cause Alzheimer disease.

To minimize the detrimental effect accompanied with the use of alum, polymers are

added either with alum or alone and have gradually gained popularity in water

treatment process. Synthetic polyelectrolytes produce sludge of better dewatering

characteristics with smaller volume and facilitate better filtration, but their long-term

effects on human health are not well understood (Pan et al., 1999). Furthermore, the

sludge formed during flocculation with synthetic polymers has a limited potential for

recycling due to the non-biodegradability of synthetic polymers (Bratskaya et al.,

2004).

Therefore, it is necessary to develop a more effective and environment

friendly coagulant as a viable alternative to these chemical coagulants. Since most of

the wastewater colloids are negatively charged, natural cationic polyelectrolytes,

such as chitosan has become a particular interest. Besides promotes an excellent

pollutant removal, the biodegradability and non-toxic nature of chitosan provides an

opportunity for water recycling in the industry and sludge recovery in the production

of fertilizers or additives for animal feeding mixture. However, chitosan is same as

aluminum sulfate or ferric chloride that must be applied in the optimum coagulation

and flocculation conditions for the best performance and cost-effectiveness.

7

1.4 Objectives

The objectives of this study are stated as below:

1. To investigate the efficiency of coagulation and flocculation processes

as a pretreatment for coffee industrial wastewater by using different

types of coagulants (aluminum sulfate, ferric chloride and chitosan).

2. To evaluate the performance of aluminum sulfate, ferric chloride and

chitosan in the reduction of total suspended solids (TSS), turbidity,

chemical oxygen demand (COD) and color.

3. To determine the optimum conditions for the coagulation and

flocculation processes of abovementioned coagulants.

1.5 Scope of Works

The steps and scopes leading to the objectives were:

1. To study and to determine the characteristics of raw wastewater from

instant coffee processing industry.

2. To investigate the optimum dosage of the selected coagulants in reducing

the pollutant load.

8

3. To determine the optimum pH for the coagulation and flocculation

processes.

4. To compare the treatment efficiency by using aluminum sulfate, ferric

chloride and chitosan.

1.6 Contribution of Study

This research will contribute on providing the optimum conditions of

coagulation and flocculation process for common coagulant such as aluminum

sulfate and ferric chlorite, applying for instant coffee processing wastewater. The

research also explores the potential of coagulation treatment system by using

chitosan, a natural polyelectrolyte. The knowledge obtained from this research will

allow more efficient, effective and economical design and operation of pretreatment

process for instant coffee industrial wastewater by using coagulation and flocculation.

CHAPTER 2

LITERATURE REVIEW

2.1 Introduction

Nowadays, water pollution is a very serious problem that occurred all around

the world followed by the very rapid evolution of industrialization. It is believed that

wastewaters from industry received relatively little treatment before the second half

of the twentieth century. If such wastewater is discharged to the environment without

proper treatment and management, it can pollute the receiving water bodies with

severe impact on the natural environment and public health. Awareness of the global

water crisis and limited supply of fresh water has initiated a general campaign to

reduce the pollution load of industrial wastewater. Regulatory agencies were set up

to monitor and control effluent discharges to fresh water.

Malaysia, a fast developing country, is also facing the water pollution

problems caused by the fast growth of industrial activities. As to protect receiving

waters and their associated aquatic system, and to protect public heath from harmful

effects of untreated wastewater, Department of Environment (DOE) has

implemented strengthened limits to regulate the disposal of industrial effluent. The

effluent standards are listed in the Environmental Quality (Sewage and Industrial

10

Effluents) Regulations 1979 under the Environmental Quality Act (EQA) 1974. In

order to meet the permissible discharge conditions, all discharging wastewater

treatment facilities, including for the instant coffee industry, must be designed and

constructed to provide at least secondary treatment that capable of producing effluent

in compliance with EQA 1974. Thus, pretreatment of industrial wastewater such as

coagulation and flocculation will become a necessity.

2.2 Instant (Soluble) Coffee

In the market, there are three forms of instant coffee: freeze dried, spray-dried

and liquid coffee extract. According to Malaysian Standard: Specification for Instant

Coffee (M.S. 777 :1982), instant coffee (soluble coffee) powder is derived by

dehydration of an aqueous extract prepared under suitable conditions of pure, freshly

roasted and ground coffee with water. The extract or brew thus obtained with or

without further concentration is dried to a powder which is packed in airtight

containers. Instant coffee may be classed as spray dried, spray dried agglomerate,

freeze dried or mixture thereof according to the method adopted for drying. The

product shall be in the form of a free flowing powder having the color, taste and

flavor characteristic of coffee. The material shall also comply with the requirements

under M.S. 777:1982 and any other requirements stipulated under the Food

Regulations currently enforced in Malaysia.

The history and background of the instant coffee can be reviewed from the

books of Ukers (1935), Clarke and Macrae (1985), and Wrigley (1988). The earliest

documented version of soluble coffee was developed in Britain in 1771. In 1853, the

first American product was developed. An experimental version (in cake form) was

field tested during the Civil War. The first successful technique for manufacturing a

stable powdered product was invented in 1901 by Dr. Sartori Kato, a Japanese

chemist from Tokyo, who used a process he had developed for making soluble tea.

11

Together with a green coffee broker and a roaster, the Kato Coffee Co, was set up

and then obtained patents on the soluble coffee process in 1903. Kato’s soluble

coffee was first sold to the public at the Pan-American Exposition of 1901.

Five years later, George Washington, a British chemist living in Guatemala,

developed the first commercially successful process for making instant coffee but

never patented. Washington's invention, marketed as “Red E Coffee” and latter

“George Washington’s Soluble Coffee”, dominated the instant coffee market in the

United States for 30 years, beginning around 1910. In the 1930s, the Brazilian

government was seeking a more widely acceptable form of soluble coffee in order to

absorb the over-production of their coffee. The problem was tackled by Nestlé in

1938 by producing a free-flowing, light-colored powder composed soluble coffee

solids and corn sugar (malto-dextrin) on a 50/50 basis that retained a reasonably

coffee-like flavor when reconstituted in hot water. Then, the Second World War has

resulted an even greater boost to instant coffee. Nestlé produced 25 million pounds

of soluble coffee for the US army during this war. After the war, competitors began

to manufacture instant coffee in a more comparable quality and the consumption has

increased rapidly worldwide.

A product made from 100% coffee solids (without adding carbohydrates) was

introduced in 1950s by General Foods. In the late 1960s, the first freeze-dried

products were developed. It was closely followed by the agglomeration of spray-

dried soluble coffee and aromatization that involving the adding back to the finished

products of aromatic elements recovered from earlier stages of coffee processing.

Latter, the decaffeinated instant coffee was also introduced. Since its invention,

manufacturers have tried to develop and improve the quality of instant coffee in a

variety of ways. It is aimed to produce an instant coffee that tastes as much as

possible like the freshly brewed beverage. Today, instant coffee industry has grown

steadily. As instant coffee providing a number of advantages over fresh brewed

coffee, it has become one of the most popular kinds of coffee drunk by millions of

people around the world. Therefore, a lot of counties have taken part in the industry

of instant coffee processing, included Malaysia.

12

2.2.1 Production of Instant Coffee

Instant coffee is manufactured from coffee beans through a series of process,

including roasting, grinding, extraction, concentration, drying and packing (Clarke

and Macrae, 1987). The green coffee bean itself has no desirable taste. It must first

be roasted to bring out its special flavor and aroma. The process of roasting is the

same for regular coffee. In most roasting plant, rotating cylinders containing the

green beans and hot combustion gases are used. The roasting begins when the bean

temperature reaches and exceeds 165 °C. These batch cylinders take about 8-15

minutes to complete the roasting with efficiency of about 25-75%. For continuous

fluidized bed roasting, it only takes between thirty seconds and four minutes. It

operates at lower temperature and allows greater retention of the coffee bean aroma

and flavor.

The next process after roasting is followed by grinding. Grinding is applied

for the purpose to reduce the coffee beans to a size between 0.5 and 1.1 mm. This is

in order to allow the coffee to be evenly put in solution with water for extraction and

then the drying stage. Sets of scored rollers that specially designed to cut rather than

crush the coffee bean are used. The particle size distribution must be tailored to

ensure extraction with high performance. Generally, too fine a grind will impede the

passage of the coffee liquor in the extraction column. Therefore, it is desired for a

coarse and fairly uniform grind.

Once roasted and ground, the coffee must be put into solution with water.

This stage is called extraction. Water is generally added in 5-10 percolation columns

at temperatures of between 155 to 180 °C to concentrate the coffee solution to about

15-30% coffee by mass. This could be further concentrated before the drying process

by using either vacuum evaporation or freeze concentration. Water is mainly used as

the solvent during this process. There are three ways for solids extraction for instant

coffee processing, included percolation batteries extraction, counter-current system

extraction, and slurry extraction.

13

For percolation batteries extraction, coffee is held in a series of vessels. Hot

water is passed through the vessels, causing the soluble coffee solids to be extracted.

The extracts are later isolated from the battery and spent coffee is discharged. For

counter-current system extraction, coffee is placed in the bottom of an inclined

cylindrical vessel and later moved upwards by the rotating of two helicoidal screws.

Hot water then comes into the top, causing the extraction of coffee solids while the

solution comes out through the bottom. Nevertheless, this process is very expensive

and not suitable for small-scale processing. For slurry extraction, water and coffee

are agitated together in a tank and separated using a centrifuge. This method is also

quite expensive.

After a filtering step to remove colloidal tars and other insoluble matter, the

brewed coffee is treated to increase its concentration. This is to create an extract that

is about 40% solids. In some cases, the liquid is processed in a centrifuge to separate

out the lighter water from the heavier coffee extract. Another alternative is to remove

water by evaporation before cooling the hot, brewed extract. A third technique is to

cool the extract to freeze water, and then mechanically separate the ice crystals from

the coffee concentrate. The next important stage in instant coffee manufacturing is

drying. There are two commercial methods of drying all over the world, included

freeze drying and spray drying, each has its own advantages and disadvantages.

Spray drying is preferred of its short drying time and cost effectiveness.

Spray drying produces spherical particles of size roughly equal to 300 µm with a

density of 0.22 g/cm³ (Masters, 1991). Nozzle atomization is used for this purpose.

Various ways of nozzle atomization can be applied commercially. High speed

rotating wheels operating at speeds of about 20,000 rpm are able to process up to

60,000 pounds of solution per hour. The use of spray wheels requires the drying

towers to have a wide radius to avoid the atomized droplets from collecting onto the

drying chamber walls. One drawback with spray drying is that the particles produced

are too fine to be used effectively by the consumer. Thus, they must be either steam-

fused in towers similar to spray dryers or by belt agglomeration to produce particles

with suitable size.

14

Nowadays, freeze drying has grown in popularity because it results in a

higher quality product. The principle of freeze drying is involving freezing of the

liquid, granulating the frozen solid, and subjecting it to conditions of ultra-high

vacuum and modest heat that causes the water in the food to sublime and produce a

dry solid product (Clarke and Macrae, 1985). Generally, the free-drying process

involves four steps. Beginning with primary freezing, extracted coffee liquor is

chilled to a slushy consistency at about -6°C. Then, the pre-chilled slush is placed on

a steel belt, trays, or drums and further cooled in a series of steps, until it reaches a

temperature of -40°C. Quick cooling processes of 30-120 seconds generate smaller,

lighter colored products, while slower processes of 10-180 minutes produce larger,

darker granules. Next, the slabs of ice are broken into pieces and ground into

particles of the size required. The frozen granules are then sent into a drying chamber

where, under proper conditions of heat and vacuum, the ice vaporizes and is removed.

The final freeze-dried or spray-dried product that carefully processed may

have a very acceptable coffee flavor when reconstituted but it usually has little or no

aroma in the dry state. Thus, it is in practice for the larger manufacturers to

‘aromatize’ the product by recovering volatile aromatic elements by various means

during the bean grinding or extraction processes and spraying them back on the

product just before the final filling operation. This can provide an attractive coffee-

like fragrance for the consumer when he opens the pack. Instant coffee in form of

spray-dried, agglomerate or freeze-dried has to be protected by suitable packaging

before distribution to the retail or catering market for prevention of absorption of

atmosphere moisture that will not only lead to lumping and eventual solidification

but also accelerate flavor deterioration (Clarke and Macrae, 1985).

15

2.2.2 Wastewater

The waste or unwanted by-products from the instant coffee manufacture are

large quantity of spent coffee ground and wastewater (Clarke and Macrae, 1987).

Instant coffee production with different technology can lead to different quantity and

characteristics of the wastewater. No much published research reports have been

focused on the wastewater from instant coffee processing and its wastewater

characteristics is very limited for reference.

The volume, concentration and composition of the effluent arising in the

manufacturing plant are dependent on the type of product being processed, the

production program, operating methods, design of the processing plant, the design of

water management being applied, and subsequently the amount of water being

conserved (Lawrence et al., 2004).

In general, the wastewaters of instant coffee processing contain higher value

of biochemical oxygen demand (BOD), chemical oxygen demand (COD), total

suspended solid (TSS) and turbidity. The wastewaters also possess a distinctive dark

brown color and the pH can be in a wide range depending on its production stages.

Coffee wastewater contains high organic loads which may result in dissolved oxygen

depletion in the receiving waters (Ricardo, 1996). If the untreated or poor treated

wastewaters are discharge directly into the environment, there will be a severe

problem and detrimental for aquatic life and human health.

Table 2.1 shows the wastewater analysis result for a coffee powder

manufacture obtained from a study by Lim (1999). The production of instant coffee

gives rise to substantial volumes of wastewaters containing a wide variety of

pollutants from different production stages. The major sources of wastewater

produced in the instant coffee processing industry include the water used for the

cleaning of extractor, spray dryer, freeze concentrator, separator, heat exchanger,

16

boiler, evaporator finisher and pasteurizer, washing the floors and working areas

(Lim, 1999).

Table 2.1: Wastewater analysis from instant coffee industry (Lim, 1999)

Location /

Production

stages

pH DO

(mg/L)

Temperature

(oC)

COD

(mg/L)

BOD5

(mg/L)

Q

(m3/d)

Heat exchanger

cleaning & spray

dryer cleaning

12.25 5.49 25.7 60 32 24

Vacuum pump

water, sealing

water

8.38 4.4 33.2 380 140 42

Extractor drain,

spent grounds

line drain

5.73 2.5 55.4 7950 2100 48

Separator

cleaning

8.50 4.61 31.7 63 38 48

Boiler area,

spent grounds

press

4.95 2.14 51 10880 970 30

Sump or bypass

8.28 3.6 39 2800 520 57

Final Discharge

5.13 2.56 33.2 3350 670 179

17

2.3 Dan Kaffe (M) Sdn Bhd

The source of wastewater for this research is obtained from Messrs Dan

Kaffe (M) Sdn Bhd. It was set up in 1994 and located at No. 7, Jalan Angkasa Mas 6,

Kawasan Perindustrian Tebrau II, Mukim Tebrau , 81100 Johor Bahru, Johor Darul

Takzim. It is to be the first coffee-extract plant with the state-of-the-art machinery

and technology in this part of the world that is able to deliver coffee extract and its

various derivative forms in word standard quality. The stringent demand for quality

every step of the production process has earned them the coveted position of being

the third largest exported of coffee extract to Japan, after Brazil and Columbia.

Dan Kaffe (M) Sdn Bhd possesses the advanced equipment and technology to

achieve rich aroma and full flavor in coffee products. An automatic batch roaster is

utilized to develop a consistently full flavor original of the raw material. The flavor-

developed coffee is then extracted with the continuous double extraction to preserve

the full flavor. The coffee extract is then passed through a ‘gentle’ freeze

concentration process to concentrate the extract to the customer’s specifications

before it is frozen to preserve the flavor. The coffee extract can also be further

processed to freeze dried coffee granules or spray dried coffee powder.

The product from Dan Kaffe (M) Sdn Bhd includes coffee extract, spray

dried coffee and freeze dried coffee. The liquid coffee extract from roasted beans is

‘gently’ concentrated with freeze concentration process. The packing size are

available in frozen form of 200kg, 100kg, 50kg, 25kg and 20kg drums, with the

application for canned coffee, bottled coffee, catering and coffee fountain. For spray

dried powder, the liquid coffee extract is atomized and dried in a hot air chamber to

concentrate the fully developed coffee flavor in the form of free flowing soluble

powder. For freeze dried coffee, frozen coffee extracts ground into coffee granules

under sub-zero temperature and dried in a high vacuum chamber. The packing size

for both types is available in 30kg carton, with application for 3-in-1 mix, consumer

coffee in jar, confectionery and catering.

18

2.3.1 Coffee Processing

Figure 2.1 illustrates the coffee manufacturing process in Dan Kaffe (M) Sdn

Bhd. Premium green beans are carefully selected from the growing regions in

accordance with customers’ requirements. When the beans arrive at the factory, they

are sampled and put to a series of stringent tests before being released to the

production line. When production begins, the approved beans will first go through

the cleaning process where cleaning and sorting take place. Here the beans are

separated from any debris or foreign matters. A further magnet screening process

removes any possible metal objects.

The cleaned beans are then transferred to the roaster. The roasting process is

fully automated to give a consistent roast and a well-developed flavor. Roasting

parameters are formulated between the experienced staff and customers to achieve a

specified flavor. The roasted beans are then transferred to the grinder and into the

extraction columns for extraction of liquid coffee. A continuous double extraction

process which enables the well-developed flavor to be preserved is used.

The coffee extract then goes through a centrifuge process to remove any tiny

coffee particles. From the centrifuge, the extract will go through either the freeze

concentration or the evaporator to concentrate the extract. The concentrated extract

will be pasteurized to eliminate any harmful microorganism before being packed in

drums and stored and preserved under subzero condition.

The pasteurized extract can also be freeze-dried. The freeze-drying process

freezes the coffee extract into sheets and then grinds the frozen sheets into granules.

It then dries the granules in its vacuum drying chamber. In another process, the

pasteurized extract goes into a spray drier to make spray-dried coffee powder. In this

process, the concentrated extract is atomized and dried with hot air to concentrate the

fully developed coffee flavor in the form of free flowing soluble powder.

19

Figure 2.1: Coffee manufacturing process

20

2.4 Coagulation and Flocculation

Coagulation and flocculation consists of adding a floc-forming chemical

reagent to a water or wastewater to enmesh or combine with nonsettleable colloidal

solids and slow-settling suspended solids to produce a rapid-settling floc (Reynolds

and Richards, 1996). Coagulation is the addition and rapid mixing of a coagulant,

which will cause destabilization of the colloidal and fine suspended solids, and then

the initial agglomeration of the destabilized particles. Flocculation is the gentle

agitation or slow stirring to aggregate the destabilized particles and form a rapid-

settling floc. The floc is subsequently removed by sedimentation or filtration.

Most colloids are stable in water solution as their negative surface charge

causing them to repel each other before they collide (Davis and Cornwell, 1991).

Cationic coagulants provide positive electric charges to neutralize and reduce the

negative charge (zeta potential) of the colloids. Thus, the particles collide to form

larger particles (flocs). Destabilization of charged particles in wastewater occurs as a

result of addition of treatment chemical. The selection of type and dosage must be

made by experimentation, most commonly with jar tests (Corbitt, 1990). Rapid

mixing is required to completely disperse the coagulant throughout the liquid while

slow mixing to mimic the flocculation basin condition.

Coagulation method is widely used in water and wastewater treatments and

well known for its capability of destabilizing and aggregating colloids. In water

treatment, the principle use of coagulation and flocculation is to agglomerate solids

prior to sedimentation and rapid sand filtration. In industrial wastewater treatment,

coagulation is employed to coalesce solids in wastewaters that have an appreciable

suspended solids content. In water treatment, the principal coagulants used are

aluminum and iron salts, although polyelectrolytes are employed to some extent. In

wastewater treatment, aluminum and iron salts, lime and polyelectrolytes are used

(Reynolds and Richards, 1996).

21

2.4.1 Colloidal Particles

According to Reynolds and Richards (1996), a portion of the dispersed solid

in surface waters and wastewaters are nonsettleable suspended materials that have a

particle size ranging from 0.1 milimicron to 100 microns. A significant fraction of

this nonsettleable matter is colloidal particulates since colloids have a particle size

ranging from one milimicron to one micron (0.001 to 1 µm). Metcalf and Eddy (2003)

classified the colloidal particles with size range from 0.01 to 1 µm while the

suspended particles are generally larger than 1 µm. The number of colloidal particles

in untreated wastewater and after primary sedimentation is typically in the range

from 106 to 10

12/mL. Colloidal particles are too small to be settled by gravity or

filtered through common filtration media. Colloidal particles may impact turbidity

and color to the water (Benefield et al., 1982).

Colloidal particles in water can be classified as hydrophilic or hydrophobic

according to their affinity for water. Hydrophobic colloids have relatively little

attraction for water; while hydrophilic colloids have a great attraction for water due

to the existence of water-soluble groups on the colloidal surface, such as amino,

carboxyl, hydroxyl and sulfonic. Colloids have an extremely large specific surface

area with an electrostatic charge relative to the surrounding water. The attraction

body forces between particles are considerably less than the repelling forces of the

electrical charge. Thus, Bownian motion keeps the particles in suspension (Metcalf

and Eddy, 2003). The system is in stable condition as the colloidal solids dispersed in

liquids (sols) and do not settle by the force of gravity.

Colloidal particles have electrostatics forces or surface charges, which are

important in maintaining dispersion and stability, due to the ionization of surface

groups, preferential adsorption, isomorphous replacement or structural imperfections

(Reynolds and Richards, 1996; Metcalf and Eddy, 2003). Hydrophilic colloids, such

as proteins and microbes, have charges due to the ionization of amino (-NH2) and the

carboxyl (-COOH) groups, that are depending on solution pH. Most naturally

22

occurring hydrophilic colloids have a negative charge if the pH is at or above the

neutral range. Oil droplets and some other chemically inert substances, will

preferentially adsorb negative ions, particularly the hydroxyl ion, from the

surrounding solution and become negatively charged. Through isomorphous

replacement, clay and other soil particles develop charge by replacing ions in the

lattice structure with ions from solution, such as the replacement of Si4+

with AL3+

.

In clay and similar particles, charge development can occur due to broken bonds on

the crystal edge and imperfections in the formation of the crystal.

2.4.1.1 Colloidal Stability

The overall stability of a colloidal particle is controlled by double-layer

repulsion forces and van der Waals forces of attraction (Benefield et al., 1982).

Colloidal particles found in wastewater typically have a net negative surface charge

(Metcalf and Eddy, 2003). A negative colloidal particle will adsorb the opposite

charge (counterions) from the surrounding water solution to its surface by

electrostatic attraction, as illustrated in Figure 2.2. The compact layer of counterions

is referred as the fixed (stern) layer while outside the fixed layer is termed as the

diffused layer. Both layers will contain positive and negative charged ions; however,

there will be a much larger number of positive ions than negative ions (Reynolds and

Richards, 1996).

The two layers represent the region surrounding the particle where there is an

electrostatic potential due to the particle (Reynolds and Richards, 1996). From Figure

2.2, it is found that the concentration of the counterions is greatest at the particle

surface. These potential is further reduced through the diffused layer until the outer

boundary of the diffused layer. These excess concentrations of counterions extend

out into the bulk solution until all the surface charge and electrostatic potential is

eliminated. Zeta potential is the magnitude of electrostatic potential at the shear plane.

It is related to the stability of a colloidal suspension that will affect the coagulation

process.

23

Figure 2.2: Structure of electrical double layer

A colloidal suspension is stable if the particles are maintained in suspension

and do not coagulate. The colloidal stability depends on the relative magnitude of the

forces of attraction and the forces of repulsion (Reynolds and Richards, 1996). The

forces of attraction are due to van der Waals forces that are effective only in the

immediate neighborhood of the colloidal particle. On the other side, the forces of

repulsion are due to the electrostatic forces of the colloidal dispersion. The

magnitude of these forces are measured by the zeta potential, which is

ζ = 4 π q d / D (2.1)

_

_

_

_

_

_

_

_

Electro-negative

Particle

Fixed Layer Diffuse Layer

Double Layer

Bulk Solution

Nernst Potential

Stern Potential

Zeta Potential

Po

ten

tia

l

Distance

Shear Plane

d

24

Where,

ζ = zeta potential

q = charge per unit area

d = thickness of the layer surrounding the shear surface through

which the charge is effective, as shown in Figure 2.2

D = dielectric constant of the liquid

From equation 2.1, zeta potential that measures the charge of the colloidal

particle is dependent on the distance through which the charge is effective. It follows

the rules that when the zeta potential is higher, the repulsion forces between the

colloids will be greater and the colloidal suspension is more stable. The presence of a

bound water layer and its thickness will also affect the colloidal stability, since this

layer prevents the particles from coming into close contact. Furthermore, hydrophilic

colloids have a shear surface at the outer boundary of the bound water layer while

hydrophobic colloids have a shear surface near the outer boundary of the fixed layer


2.4.1.2 Colloidal Interactions

Figure 2.3 shows the interparticulate forces acting on a colloidal particle. The

attractive forces are caused by the van der Waals forces acting between the particles.

The repulsive forces are due to the electrostatic zeta potential. Derjagin-Landau-

Vervey-Overbeck (DLVO) theory combines the action of the van der Waals

attractive forces with the electrostatic repulsive forces and the “net” potential caused

by the addition of these two forces determines the strength of the colloid interactions

(Hendricks, 2006). From Figure 2.3, the net resultant force is attractive out to the

distance x. Beyond this point the net resultant force is repulsive.

25

Figure 2.3: Colloidal interparticulate forces versus distance

2.4.2 Mechanisms of Coagulation

Particle destabilization can be achieved through four mechanisms: (1) double

layer compression, (2) adsorption and charge neutralization, (3) enmeshment in a

precipitate, and (4) adsorption and interparticle bridging (Benefield et al., 1982).

Coagulation is the processes by which the charge on particles is destroyed, or when

the DLVO energy barrier is effectively eliminated while flocculation is the

aggregation of particles into larger units. In this sense, double layer compression and

charge neutralization are considered to be coagulation, while enmeshment and

bridging are classified as flocculation (Benefield et al., 1982).

Att

rac

tio

n

Re

pu

lsio

n

x

Repulsion due to Zeta Potential

Attraction due to van der Waals Forces

Net Resultant Force

Distance Fo

rce

26

2.4.2.1 Double Layer Compression

This mechanism is based on DLVO theory of interactions between particles

as discussed before. Double layer compression involves electrostatic repulsion. It

occurs when counterions is added as coagulant. Surrounding the negatively charged

colloidal particle is an inner fixed layer and outer diffused layer of counterions. The

concentration of counterions is highest at the particle surface and decreases to that of

the bulk solution at the outer boundary of the diffused layer. Destabilization of

particles by counterions causes the diffused layer to compress around the particles.

High concentration of electrolyte in solution results a high concentrations of

counterions in the diffused layer. Compression of the diffused layer decreases the

electrostatic repulsive forces between the similar colloidal particles and the zeta

potential is mitigated. Thus, the attractive forces (van der Waals forces) can

dominate to bind particles together.

2.4.2.2 Charge Neutralization

Charge neutralization occurs when a charged particle is destabilized by

coagulant ions. As the coagulant dissociates in water, hydrolysis reactions produce

positively charged metal hydroxide ions that adsorbed to the surface of the negative

particles. The zeta potential, or charge on the colloidal particle, is reduced to a level

where the colloidal are destabilized. A stoichiometric relationship exists between the

coagulant and the particles under condition of charge neutralization. Restabilization

of particles may occur when excessive coagulant concentrations are added.

Monitoring the zeta potential of the particles gives an indication of coagulations

leading to restabilization.

27

2.4.2.3 Sweep Coagulation

Sweep coagulation involves the formation of a solid precipitate. The addition

of high concentrations of alum or ferric chloride in water forms metal hydroxides

precipitates which can enmesh colloidal particles (AWWA, 1990). In sweep

coagulation, physical interaction occurs between the voluminous metal hydroxide

precipitates and the raw water colloids. The negative colloids are enmeshed in the

precipitates. Sweep coagulation in water treatment occurs when the water is

supersaturated by three to four orders of magnitude above the solubility of the metal

salt. Under supersaturated conditions, metal hydroxide species precipitate rapidly.

2.4.2.4 Interparticle Bridging

Destabilized particles can be aggregated by bridging with a polymer.

Interparticulate bridging entails the interaction between the polymer and the reactive

groups on the destabilized particles. When a polymer with high molecular weight

comes into contact with a colloidal particle, some of the reactive groups in the

polymer adsorb at the particle surface and leaving other portions of the molecule

extending into the solution. A second particle can become attracted which forms a

particle-polymer-particle aggregate with the polymer serves as a bridge (AWWA,

1990).

2.5 Coagulants

The most widely and conventionally used coagulants in water treatment are

aluminum sulfate and iron salts. Aluminum sulfate (filter alum) is employed more

frequently than iron salts because it is usually cheaper. Nevertheless, iron salts

28

generally offer advantages over aluminum ones when pH adjustment is made to

produce a floc, in that floc formation is sensitive to pH with iron salts, owing to the

amphotericity of aluminium; and Fe(III) is also often superior to Fe(II) because it has

a wider pH range of action (Eilbeck and Mattock, 1987). Besides metal salts, high

molecular weight polymers or polyelectrolytes are also applied to produce a rapid-

settling floc. A coagulant is chosen based on the characteristics of the raw

wastewater and the preferred mechanism of coagulation.

2.5.1 Inorganic Metal Salts

The principle inorganic coagulants used in waster and wastewater treatment

are salts of aluminum and ferric ions, such as aluminum sulfate, ferrous sulfate, ferric

chloride and ferric sulfate. When added to water, these ions undergo a series of

reactions to form various hydrolysis products dependent on pH and concentration

(ionic strength of the solution). These hydrolyzed forms of metal ions are important

for particles destabilization and removal. Coagulation diagrams for aluminum (III)

and iron (III) salt (based on turbidity removal) are demonstrated in Figure 2.4 and

Figure 2.5 respectively. The tri-valent ion of aluminum and ferric ions have similar

reactions with water and either one can be used to illustrate the reaction behavior

(Hendricks, 2006).

When aluminum ion is added to water, the reaction product is a complex with

six water ligands, where the six waters each share a coordinated bind with the central

metal ion. This Al(H2O)63+

complex is commonly abbreviated as simply Al3+

. From

this initial product, an array of sequential hydrolysis reactions occurs where proton

loss occurs from the each of the water ligands, each at a time (Hendricks, 2006). A

simplified hydrolysis reaction is given in equation 2.2.

Al3+

→ Al(OH)2+

→ Al(OH)2+ → Al(OH)3 → Al(OH)4

- (2.2)

29

The array of hydrolysis products that result exist in equilibrium with the

distribution dependent on the solution pH as shown in Figure 2.4. This hydrolysis

scheme will proceed from left to right as the pH is increased, giving first the doubly

and singly-charged cationic species and then the uncharged aluminum hydroxide,

Al(OH)3.

From Figure 2.4, it can be seen that a significant amount of non-hydolyzed

Al3+

can only be found under low pH. The hydroxide is of very low solubility and an

amorphous precipitate can form at intermediate pH value (Duan and Gregory, 2003).

This is an enormous practical significance in the action of these materials as

coagulants. Minimum solubility of Al3+

is reached at pH 6 (Metcalf and Eddy, 2003).

When further increase in pH, the soluble anionic form Al(OH)4- (aluminate ion)

becomes dominant. Apart from simple monomeric hydrolysis products, there are

many possible polynuclear species (several aluminum ions) formed, such as

Al2(OH)24+

and Al13(OH)345+

, as well as some polymerization products, before a

negative aluminate ions is formed.

When a coagulant is added to the wastewater, destabilization of the colloids

will occur and a coagulant floc is formed. The interactions involved are (1) the

reduction of the zeta potential to a degree where the attraction van der Waals forces

and the agitation provided cause the particles to coalesce; (2) the aggregation of

particles by adsorption and interparticulate bridging between reactive groups on the

colloids; and (3) the enmeshment of particles in the precipitate floc that is formed


A coagulant salt will dissociate when it is added to the water. The common

coagulant is an aluminum salt, such as Al2(SO4)3, or an iron salt, such as Fe2(SO4)3

(Reynolds and Richards, 1996). The metallic ion undergoes hydrolysis and creates

positively charged hydroxo-metallic ion complexes. Al6(OH)15+3

, Al7(OH)17+4

,

Al8(OH)20+4

, and Al13(OH)34+5

are some of the resulting polymers for aluminum salts,

while Fe(OH)2+, Fe2(OH)2

+4 and Fe3(OH)4

+5 are the resulting polymers for iron salt

30

(Hendricks, 2006). The hydroxo-metallic complexes are polyvalent with high

positive charges that are able to adsorb to the surface of negative colloidal

particulates. A reduction of the zeta potential could be resulted to a level where the

colloids are destabilized.

The destabilized particles, along with their adsorbed hydroxo-metallic

complexes, will aggregate by interparticulate attraction of van der Waals forces.

These forces are aided by the gentle agitation of the water. In the aggregation process,

the agitation is very important since it causes the destabilized particles to come in

close vicinity, collide and then coalesce. Besides, the aggregation of the destabilized

particles also occurs by interparticulate bridging that involving chemical interactions

between reactive groups on the destabilized particles. The agitation of the water is

also important in this type of aggregation, since it causes interparticulate contacts.

The dosages of coagulation salts used are generally in appreciable excess of

the amount required to produce the necessary positive hydroxo-metallic complexes.

The excess complexes will continue to polymerize until they form an insoluble

metallic hydroxide, Al(OH)3 or Fe(OH)3. The solution will be supersaturated with

the hydroxide. In the formation of the metallic hydroxide, there is enmeshing of the

negative colloids with the precipitate as it forms. This enmeshment type of

coagulation is sometimes referred to as precipitate or sweep coagulation.

As the zeta potential reduction was caused by the adsorption of the highly

positively charged hydroxo-metallic complexes, the species of polyvalent metallic

ion complexes are more effective in coagulating a colloidal dispersion than the

monovalent complexes. Thus, polyvalent metallic salts are always used in the

coagulation (Reynolds and Richards, 1996).

31

Figure 2.4: Design and operation diagram for alum coagulation (Amirtharajah and

Mills, 1982)

Sweep coagulation

Optimum sweep

Charge neutralization to zero zeta potential with Al(OH) (s)

Charge

neutralization

Al(OH)2+

Restabilization zone boundaries change with

Combination sweep and charge neutralization

Al(OH)4

Al total

Al3+

Al8(OH)204+

Alu

m a

s A

l 2(S

O4) 3

.14H

2O

–m

g/L

Lo

g [

Al]

–m

ol/

L

pH of mixed solution

32

Figure 2.5: Design and operation diagram for Fe(III) coagulation (Johnson and

Amirtharajah, 1983)

Lo

g [

Fe

] –

mo

l/L

Fe

Cl 3

.6H

2O

–m

g/L

pH

33

2.5.1.1 Aluminum Sulfate

Aluminum sulfate is a widely used industrial chemical. It occurs naturally as

the mineral alunogenite. It is frequently used as a coagulating and flocculating agent

in the purification of drinking water and industrial wastewater treatment plants.

Aluminum sulfate has appearance as a white crystalline solid. Aluminum sulfate is

rarely, if ever, encountered as the anhydrous salt. It forms a number of different

hydrates, of which the hexadecahydrate is the most common.

Aluminum sulfate may be made by dissolving aluminum hydroxide, Al(OH)3,

in sulfuric acid, H2SO4 as per following equation:

2Al(OH)3 + 3H2SO4 + 10H2O → Al2(SO4)3·16H2O (2.3)

Sufficient alkalinity must be present in the water to react with the aluminum

sulfate to produce the hydroxide floc. Usually, for the pH ranges involved, the

alkalinity is in the form of the bicarbonate ion. The simplified chemical reaction to

produce the floc is as follows:

Al2(SO4)3.14H2O + 3Ca(HCO3)2 → 2Al(OH)3 + 3CaSO4 + 14H2O + 6CO2 (2.4)

Certain waters may not have sufficient alkalinity to react with the alum, so

alkalinity must be added. Usually alkalinity in the form of the hydroxide ion is added

by the addition of calcium hydroxide (slaked or hydrated lime). The coagulation

reaction with calcium hydroxide is

Al2(SO4)3.14H2O + 3Ca(OH)2 → 2Al(OH)3 + 3CaSO4 + 14H2O (2.5)

34

Alkalinity may also be added in the form of the carbonate ion by the addition

of sodium carbonate (soda ash). Most waters have sufficient alkalinity, so no

chemical needs to be added other than aluminum sulfate. The optimum pH range for

alum is from about 4.5 to 8.0, since aluminum hydroxide is relatively insoluble

within this range (Reynolds and Richards, 1996).

Aluminum sulfate is available in dry and liquid form; however, the dry form

is more common. The dry chemical may be in granular, powdered or lump form, the

granular being the most widely used. The granules, which are 15 to 22% Al2O3,

contain approximately 14 waters of crystallization, weigh from 960 to 1010 kg/m3,

and may be dry fed. The dry chemical may be shipped in bags, barrels, or bulk

(carload). The liquid from is 50% alum and is shipped by tank car or tank truck.

2.5.1.2 Ferric Chloride

Ferric chloride is an industrial scale commodity chemical compound, with the

formula FeCl3. When dissolved in water, ferric chloride undergoes hydrolysis and

gives off heat as the reaction is exothermic. The resulting brown, acidic, and

corrosive solution is used as a coagulant in water and wastewater treatment plant.

The simplified reaction of ferric chloride with natural bicarbonate alkalinity

to form ferric hydroxide is

2FeCl3 + 3Ca(HCO3)2 → 2Fe(OH)3 + 3CaSO4 + 6CO2 (2.6)

If natural alkalinity is insufficient for the reaction, slaked lime may be added

to form the hydroxide, as given by the equation

2FeCl3 + 3Ca(OH)2 → 2Fe(OH)3 + 3CaCl2 (2.7)

35

The optimum range for ferric chloride is from about 4 to 12 (Reynolds and

Richards, 1996). The floc formed is generally dense, rapid-settling floc. Ferric

chloride is available in dry or liquid form. The dry chemical may be in powder or

lump form. The lump form being the more common. The lumps, which are 59 to

61% FeCl3, contain six waters of crystallization and weigh from 960 to 1026 kg/m3.

The lumps are very hydroscopic and are usually solution fed. Upon absorbing water,

they decompose to yield hydrochloric acid. The powdered or anhydrous form is 98%

FeCl3, contain no water of crystallization and weight from 1360 to 1440 kg/m3. The

liquid form is 37 to 47% FeCl3. The dry form is shipped in barrels, the solution form

in bulk.

2.5.2 Polyelectrolytes

Polyelectrolyte is a polymer that having ionizable groups, usually one or

more per repeat unit (Vorchheimer, 1981). Monomers are polymerized to form

polyelectrolyte with high molecular weight and high charge densities. More than

1000 polyelectrolytes have been accepted for use in water and wastewater treatment,

although these polymers can be divided into 10 to 15 different types (Letterman and

Pero, 1990). The complexity of the polyelectrolyte is based on the numerous

structures including linear, cross-linked and branched chains, and the variation in the

manufacturing processes. The advantage of polyelectrolytes is the removal of

turbidity with much less floc compared with conventional coagulant, which causes a

decrease in the weight and volume of sludge, increases filter runs and also allows

higher filtration rates (Carn and Parker, 1985).

Polyelectrolytes can be classified as anionic (negative charge), cationic

(positive charge) or nonionic (neutral). The most common type of negatively charged

group in the anionic polyelectrolytes is the carboxyl group (-COO- ). The cationic

polyelectrolytes contain positively charged group, such as amino (-NH3+). Polymers

36

with no charged sites or a very low tendency to develop them in aqueous solution are

known as nonionic polymers. Ampholyte polymers have both positive and negative

sites. Anionic and nonionic polyelectrolytes generally have molecular weight about

10 times or more than that of typical cationic polyelectrolytes. The cationic

polyelectrolytes are often referred as primary coagulants while anionic and nonionic

polyelectrolytes are referred to either as coagulant aids or flocculants (Letterman and

Pero, 1990).

Furthermore, polyelectrolytes may be divided into two categories: synthetic

and natural (Metcalf and Eddy, 2003). Synthetic polyelectrolytes consist of simple

monomers that are polymerized into high-molecular-weight substance. Synthetic

water soluble polymers such as polyacrylamides, polyethylene oxide, polyvinyl

alcohol, polyethylene-imine were first used in the 1950’s (Leu and Ghosh, 1988).

Natural polyelectrolytes are polymers of biological origin and those derived from

starch products such as cellulose derivatives, alginates, chitin derivatives, microbial

polysaccharides and gelatins.

Particle destabilization and aggregation with polyelectrolytes can be divided

into three general categories: charge neutralization, polymer bridge formation, and

combination of charge neutralization and polymer bridge formation (Metcalf and

Eddy, 2003). For the first category, cationic polyelectrolytes act as primary

coagulants to lower or neutralize the negative charged particles in wastewater. The

polyelectrolytes must be adsorbed to the particle for proper charge neutralization. As

large number of particles in the wastewater, the mixing intensity must be sufficient

for the adsorption process, otherwise the polymer will fold back on itself and

ineffectively to reduce the surface charge. If too much polymer is added to a

suspension, each particle’s overall surface charge may become positive and this

occurrence, known as restabilization, can adversely affect coagulation and filtration.

The second type of polyelectrolytes action is interparticle bridging. Anionic

and nonionic polymers that have high molecular weight and appreciable length, are

37

able to attach at a number of adsorption sites of particle surface. A bridge is formed

when two or more particles become absorbed along the length of the polymer. Then,

the bridged particles become intertwined with other bridged particles as bigger flocs

during flocculation. For affinity of the adsorption, van der Waals force has the major

effect for adsorbing and destabilizing of colloids. If the dosage of polyelectrolytes

exceed the saturation of polymer bridging and no bridging sites are available, surplus

polyelectrolytes will destroy the polymer bridging between particles and cause

particles restabilization. Inadequate mixing also inhibits the polymer bridging

formation. Figure 2.6 illustrates several bridging functions of the polymers in the

inter-particle bridging.

For the third mode, the interaction may be classified as charge neutralization

and polymer bridging mechanisms, which results from using high molecular weight

of cationic polyelectrolytes. The polyelectrolytes will neutralize or lower the particle

surface charge, and subsequently form particle bridges to interconnect particles in

agglomerates. Chitosan, a natural cationic polyelectrolytes, that is used in this study,

is categorized in this mode with the application as coagulant and flocculant in

wastewater treatment.

38

Figure 2.6: Schematic organic polyelectrolyte bridging model for colloid

destabilization (Faust and Aly, 1983)

39

2.5.2.1 Chitosan

Chitosan is a linear polysaccharide composed of randomly distributed ß-(1-

4)-linked D-glucosamine (deacetylated unit) and N-acetyl-D-glucosamine (acetylated

unit). Figure 2.7 shows the chemical structure of chitosan. Chitosan is obtained from

the deacetylation of chitin that is the second most abundant organic material after

cellulose. Chitin (poly N-acetyl-D-glucosamine) is a cellulose-like biopolymer

widely distributed in nature, occurring in crustaceans, arthropods, fungi and yeasts

(Muzzarelli, 1977). The degree of deacetylation (%DD) can be determined by NMR

spectroscopy, and the %DD in commercial chitosans is in the range 60-100 %.

Chitosan is now available as a commercial product, manufactured from crab and

prawn shells, in countries such as Japan, China, Taiwan, India and the US which

have long coastlines where fishing and sea-food processing are major industries

(Divakaran and Pillai, 2001).

Figure 2.7: Chemical structure of chitosan

The chemical structure of chitosan is very similar to that of cellulose. While

cellulose is a polymer of d-glucose, chitosan is a polymer of d-glucosamine, with an

amino group (-NH2) in place of the hydroxyl group (-OH) on carbon-2 of d-glucose.

Chitosan is described as a cationic polyelectrolyte and is expected to coagulate

negatively charged suspended particles found in natural turbid waters. Chitosan is a

polymer of glucosamine monomer units with a degree of polymerization of

40

approximately 104 monomer units and molecular mass approximately 10

6 g/mol

(Divakaran and Pillai, 2002).

Chitosan is a non-toxic, linear cationic polymer with high molecular weight,

charge density and readily to be soluble in acidic solutions (An, et al., 2001).

Chitosan is virtually insoluble in water and alkalis under normal conditions. It can

soluble in dilute carboxylic acid solutions, in which acetic acid (HAc) has been a

most common solvent for chitosan. Chitosan has been recommended as a suitable

coagulant resource material. This is because of its excellent properties such as

biodegradability, biocompability, adsorption property, flocculating ability,

polyelectrolisity and its possibilities of regeneration in number of applications (Ravi,

2000).

Chitosan’s versatility as an adsorption is a function of its highly reactive

amino group at the C(2) position, besides the reactive primary and secondary

hydroxyl groups (Savant and Torres, 2000). The protonation of the amino groups in

solution results the chitosan to be positively charged and acts as cationic

polyelectrolytes, that is very attractive for flocculation and different kind of binding

application by allowing the molecule to bind to negatively charged surface via ionic

or hydrogen bonding (Gamage, 2003).

Since chitosan is effective in coagulation without any known disadvantage, it

can be a promising substitute for synthetic products (Kawamura, 1991). Studies on

the use of chitosan, either alone or in conjunction with inorganic coagulants such as

alum and ferric chloride have been reported by Bough (1975a, b); Bough et al. (1975)

and Kawamura (1991). Besides, chitosan has been applied in the coagulations of

bentonite and koalinite particles (Huang and Chen, 1996). The preliminary studies

suggested that chitosan can be a potent coagulant for the surface water treatment.

When investigating the adsorption of chitosan on kaolin, Domard et al. (1989)

showed that the adsorption can be described by the Langmuir equation and that the

greatest adsorption was achieved when the chitosan was fully deacetylated.

41

Furthermore, chitosan has been studied for the application as a coagulant or

flocculant for a variety of suspensions including the following: food industry

(Fernandez and Fox, 1997; Pinotti et al., 1997; Savant and Torres, 2000), fish

processing (Guerrero et al., 1998), latex particles (Ashmore and Hearn, 2000;

Ashmore et al., 2001), silt in river water (Divakaran and Pillai, 2002), mineral

colloids (Huang et al., 2000; Divakaran and Pillai, 2001; Roussy et al., 2004) and

microorganisms (Weir et al., 1993a, 1993b; Strand et al., 2001, 2002).

CHAPTER 3

METHODOLOGY

3.1 Introduction

Bench scale coagulation and flocculation studies were conducted as the

pretreatment for raw wastewater from an instant coffee processing factory. Three

types of coagulant namely aluminum sulfate, ferric chloride and chitosan were

investigated. All the experiments were carried out at Pollution Control Laboratory,

Faculty of Chemical and Natural Resources Engineering, Universiti Teknologi

Malaysia. Figure 3.1 showed the research procedures, which were mainly consisted

of wastewater sampling and preservation, bench scale jar tests, analytical analyses

for wastewater before and after the tests, data analyses, discussions and conclusions.

Jar tests were conducted in order to determine the optimum coagulant

dosages and optimum coagulation pH. Trials with different types of coagulant,

different dosages of used coagulant and then coagulation pHs were analyzed in jar

tests. The results were evaluated using the major ecological parameters, included

turbidity, total suspended solids (TSS), chemical oxygen demand (COD), color and

pH. The effectiveness of the treatment processes of used coagulants were analyzed

and compared based on the removal / reduction of these parameters.

43

Figure 3.1: Research procedures

Raw wastewater

sampling and

preservation

Jar tests:

• Coagulants:

Aluminum Sulfate,

Ferric Chloride,

Chitosan

• Different dosages

• Different pH

Analytical analyses

Analytical analyses

Parameter:

• Turbidity

• TSS

• COD

• pH

• Color

Data analyses,

discussions and

conclusions

44

3.2 Materials

3.2.1 Wastewater Sample

Raw wastewater samples of instant coffee industry were collected from

Messrs Dan Kaffe (M) Sdn Bhd, Johor Bahru. The sampling point was located at the

inlet of the existing wastewater treatment plant. The collected samples were filled in

a 25 Liter plastic container with proper label. The sample container was sealed

tightly and transported to the laboratory. In the laboratory, the initial raw wastewater

was analyzed to study its characteristics. Then, the raw wastewater samples were

preserved and refrigerated at about 4 oC to retard biological activity prior to use.

Before any test, raw wastewater samples need to be removed from the refrigerator

and placed for about 2 hours at room temperature of 25 ± 1 oC for conditioning.

Samples were thoroughly agitated for re-suspension of possible settling solids before

filling to each beaker for jar tests.

3.2.2 Aluminum Sulfate

Aluminum sulfate, Al2(SO4)3.18H2O was purchased from Hamburg

Chemicals in the form of white crystalline solid. The molecular weight of the

aluminum sulfate is 666.43 g/mol. The stock solution of aluminum sulfate with

concentration of 40 mg/mL was prepared in advance of the tests. 40 gram of

aluminum sulfate was dissolved in 1.0 Liter of distilled water. During the test, 1 ml

of stock solution added to 400 mL of wastewater sample in a beaker will equal to

100 mg/L of aluminum sulfate.

45

3.2.3 Ferric Chloride

Ferric chloride, Fe2Cl3.6H2O was purchased from GCE Laboratory

Chemicals. The molecular weight of the ferric chloride is 270.30 g/mol. The stock

solution of ferric chloride was prepared before the tests by dissolving 40 gram of

ferric chloride in 1.0 Liter of distilled water. The solution was dark-brown in color

with concentration of 40 mg/mL. As such, 1 ml of stock solution will result the

concentration in a 400 mL of wastewater sample to be equaled to 100 mg/L of ferric

chloride.

3.2.4 Chitosan

Chitosan was purchased in the form of a pale brown powder. Chitosan is

virtually insoluble in water under normal conditions. It can dissolve in carboxylic

acid solutions, in which acetic acid (HAc) has been a most common solvent for

chitosan. However, this organic solvent might increase the organic content of

suspensions, which were coagulated by chitosan (Huang et al., 2000). In this study,

therefore, one of inorganic acids, hydrochloric acid (HCl), was selected as an

alternative solvent to evaluate the coagulation capacity of HCl-prepared chitosan.

1.0 gram of chitosan powder was weighed accurately into a glass beaker and

mixed with 100 mL of 0.1M HCl solution and kept aside for about an hour to

dissolve. The dissolution was slow, and some amount of chitosan remained in the

form of a thin gel even after this time. It was then diluted to 1.0 L with distilled water

to obtain a solution containing 1.0 mg chitosan per mL of solution. Thus, 1 mL of

solution added to 400 mL wastewater sample will equal to 2.5 mg/L of chitosan. The

solutions were prepared fresh before each set of experiments for consistency.

46

3.3 Jar Test Experiment

Jar testing is a common laboratory procedure used to determine the optimum

operating conditions for water or wastewater treatment as it can mimic full-scale

operation of the treatment process. The jar test simulates the coagulation and

flocculation processes where optimal conditions are determined empirically rather

than theoretically. The values that are obtained through the experiment are correlated

and adjusted in order to account for the actual treatment system.

There are many variables affecting the performance of a chemical during jar

tests. These variables included coagulation pH, chemical type and chemical quantity,

test solution type, wastewater characteristics, stirrer speed for fast and slow mixing,

temperature, length of time of flash mixing and settling (Clark and Stephenson,

1999). The first two main variables (coagulant dosage and pH) were investigated in

this research.

The selection of type and dosage of coagulant, as well as the coagulation pH

must be made by experimentation, most commonly with jar tests (Corbitt, 1990). The

jar test apparatus consists of a set of six jars, which are used in conjunction with a

gang stirrer. The apparatus permits all six jars to be controlled simultaneously for

start, stop and rotation speed of paddles (Hendricks, 2006). Rapid mixing is required

to completely disperse the coagulant throughout the liquid while slow mixing mimics

the flocculation basin condition. It is important not to overdose the coagulants

because a complete charge reversal and re-stabilization of colloid complex can be

occurred.

In this research, a Phipps and Bird six-place paddle stirrer with 1 L beakers

was used to perform the jar tests that simulating the coagulation / flocculation and

settling processes. The apparatus was shown in Figure 3.2. For each set of

experiment, there will be five positions receiving coagulant at given dosages or

47

variation in pH value, and one control jar receiving initial raw wastewater only. The

analytical analyses for initial concentration of turbidity, TSS, COD, color and pH

were carried out for the control jar prior to the test. By using jar tests, the optimum

dosage was determined first for each single coagulant and then followed by its

optimum coagulation pH study.

(a) Mixing phase

(b) Settling phase

Figure 3.2: Jar test apparatus

Figure 3.3 illustrated the detailed steps to investigate the optimum dosage for

three different coagulants (aluminum sulfate, ferric chloride and chitosan). For each

single coagulant, a two-step method was performed. There will be an initial testing

for a wide range of doses, followed by a more tighten range that above and below the

best jar dosage obtained in the first test. After obtaining the optimum dosage, the best

coagulation pH was determined by following the procedures as displayed in Figure

3.4. The pH was adjusted by using 0.25 M HCl or 0.25 M NaOH solution. At last, a

48

jar test using three single coagulants, each at its optimum dosage and pH were

carried out to compare their treatment performance for instant coffee wastewater.

On addition of the coagulant, the solutions were rapidly mixed at 250 rpm for

a minute. The rapid mixing stage was to disperse the coagulant throughout each

beaker. This was followed by a slow mixing period of 20 minutes at 30 rpm. The

slow mixing speed helped to promote floc formation by enhancing particles

collisions, which leaded to larger flocs. The speed was slow enough to prevent

sheering of the floc due to turbulence caused by fast stirring. The paddles were then

lifted out of the sample beakers and the suspensions were left undisturbed for a

quiescent settling time for 30 minutes.

After the settling phase was completed, samples of the treated water or

supernatant were withdrawn by using a pipette from a depth of approximately 1.5 cm

below the surface for further analytical analyses of turbidity, TSS, color, COD and

pH. The optimum value of coagulant dosage and coagulation pH was identified at the

maximum removal efficiency of turbidity, TSS, COD and color. For a better

comparison among aluminum sulfate, ferric chloride and chitosan, the volume of

sludge that settled at the bottom of each jar after one hour was measured.

The initial and final concentration of each parameter was used to calculate the

pollutant removal efficiency by using equation 3.1.

Removal efficiency, % = (Ci – Cf ) x 100 (3.1)

Ci

Where,

Ci = initial concentration of wastewater

Cf = final concentration of supernatant

49

Figure 3.3: Jar tests to determine optimum dosage

Fill 1-Liter beaker each with 400 mL wastewater

Add the single coagulant to the wastewater at the initial pH

i. Jar tests for Aluminum Sulfate:

a. 500 to 2500 mg/L with 500 mg/L interval

b. 250 mg/L interval in between optimum point of (a)

ii. Jar tests for Ferric Chloride:



iii. Jar tests for Chitosan:



Fast mixing at 250 rpm for 1 minute

Slow mixing at 30 rpm for 20 minutes

Settling for 30 minutes

Withdraw the supernatant from a point located about 1.5 cm

below the top of the liquid level of the beaker

Analytical analyses: Turbidity, TSS, pH for (a)

Turbidity, TSS, COD, Color, pH for (b)

Initial analytical analyses: Turbidity, TSS, COD, Color, pH

50

Figure 3.4: Jar tests to determine optimum pH

Fill 1-Liter beaker each with 400 mL wastewater

Adjust the pH value of wastewater in the range of 4-8

by using 0.25 M HCl or 0.25 M NaOH

Fast mixing at 250 rpm for 1 minute

Slow mixing at 30 rpm for 20 minutes

Settling for 30 minutes

Withdraw the supernatant from a point located about 1.5 cm

below the top of the liquid level of the beaker

Analytical analyses: Turbidity, TSS, COD, Color, pH

Add the pre-determined optimum value of coagulant for

i. Aluminum Sulfate

ii. Ferric Chlorite

iii. Chitosan

Initial analytical analyses: Turbidity, TSS, COD, Color, pH

51

3.4 Analytical Methods

All of the quality parameters that applied in the study such as turbidity, total

suspended solids (TSS), chemical oxygen demand (COD), color and pH were

analyzed according to the procedures described in Standard Method for the

Examination of Water and Wastewater (APHA, 2002).

3.7.1 Turbidity Measurement

Turbidity in water is caused by suspended matter, finely dissolved organic

and inorganic matter, soluble colored organic compounds and other microscopic

organisms. Turbidity is an expression of the optical property that causes light to be

scattered and absorbed rather than transmitted in straight lines through the sample.

Correlation of turbidity with the weight concentration of suspended matter is difficult

because the size, shape and refractive index of the particles also affect the light-

scattering properties of the suspension (APHA, 2002).

Turbidity was measured using HACH Ratio/XR turbidimeter (HACH

Company, Loveland, Colorado). A photo of the turbidity meter was shown in

Appendix A. For wastewater sample that had been agitated thoroughly, 25 mL of the

volume was filled in a matched cell. The outside of the cell was cleaned and then

placed in the cell holder for turbidity measurement. The measured value was showed

in Nephelometric Turbidity Units (NTU). It is important to prevent any formation of

air bubbles in the cell by allowing sufficient time for bubbles to escape, as their

presence will cause erroneous turbidity reading. The instrument was regularly

calibrated with Formazin turbidity standard solutions supplied by the manufacturer.

52

3.7.2 Total Suspended Solids (TSS)

A well-mixed sample was filtered through a weighed standard glass fiber

filter and the residue retained on the filter was dried to a constant weight at 103 to

105 oC. The increase in weight of the filter represented the total suspended solids. If

the suspended material clogs the filter and prolongs filtration, it may be necessary to

increase the diameter of the filter or decrease the sample volume (APHA, 2002).

The first procedure is preparation of glass microfiber filters in Gooch

crucibles. The filtering apparatus as shown in Appendix A was assembled. The

crucibles were washed, rinsed, dried in the oven for 10 to 20 minutes and then set on

the crucible holding unit. The filters were added and then wetted with distilled water

with the vacuum already applied. They were then placed in the oven at 103 to 105 oC

for at least one hour and subsequently cooled in the desiccator for at least one hour to

balance the temperature. Crucibles were weighted as Wi, before being used in

filtration.

For filtration step, different sample volumes of 2 mL, 5 mL, 10 mL and 25

mL were selected (depending upon the solids concentration levels and physical

appearance of the raw samples) to ensure that more representative samples were used

in each run. The samples were then filtered through the Gooch crucibles. Then, the

crucibles were taken off the holding unit, placed in the oven at 103 to 105 oC for one

hour and then cool in the desiccator for one hour. After cooling, the crucibles were

weighed as Wf to calculate the total suspended solid by equation 3.2.

Total Suspended Solid, mg/L = (Wf – Wi ) x 1000 (3.2)

Volume of sample, mL

Where,

Wi = initial weight of filter and Gooch crucible (before filtration), mg

Wf = final weight of filter and Gooch crucible (after filtration), mg

53

3.7.3 Chemical Oxygen Demand (COD)

The chemical oxygen demand (COD) is used as a measure of the oxygen

equivalent of the organic matter content of a sample that is susceptible to oxidation

by a strong chemical oxidant (APHA, 2002). 2 mL of sample was heated with a

strong oxidizing agent, potassium dichromate at 150 oC in a COD reactor for 2 hours.

When it was cooled to room temperature, COD was analyzed by colorimetric method

using Spectrophotometer HACH Model DR/2000 (HACH Company, Lovelend,

Colorado). Appendix A showed the photo of the COD reactor and spectrophotometer.

3.7.4 Color

Color measurements were reported as true color (filtered using 0.45 µm filter

paper) assayed at 455 nm by using spectrophotometer DR/2000 (HACH Company,

Loveland, Colorado). Color is reported in Platinum–cobalt (PtCo) with 1 unit of

color is produced by 1 mg platinum/L in the form of the chloroplatinate ion.

3.7.5 pH

The pH was measured using the EcoMet pH meter (Interscience Sdn. Bhd.,

Selangor) as shown in Appendix A. The meter was checked daily with buffer

solutions of pH 4.0, 7.0 and 10.0 and calibrated when reading deviated from the

standard. For the measurement, the electrode probe was placed into the sample and

the pH value was obtained when the reading had stabilized. Between samples, the

electrode was rinsed with deionized distilled water.

CHAPTER 4

RESULTS AND DISCUSSIONS

3.5 Wastewater Characteristics

Typical characteristics of the raw wastewater from instant coffee industry

based on the samples using in this study are summarized in Table 4.1. The

concentration and composition of the effluent collected from the instant coffee

manufacturing plant varied and fluctuated significantly as it is very dependent on the

production program and operating methods on each day.

Table 4.1: Typical characteristics of the raw wastewater

Parameter Range of variables Standard Ba

pH 4.57-6.46 5.5 – 9.0

Turbidity (mg/L) 418-1835 -

Total Suspended Solids (TSS) 340-2280 100

Chemical Oxygen Demand (COD) 2040-4242 100

Color (PtCo) 8370-12540 -

a Standard B of the Environmental Quality (Sewage and Industrial Effluents)

Regulations 1979, under the Environmental Quality Act (EQA) 1974

55

3.6 Effect of Dosage

Dosage of the coagulant is a very important parameter in determining the

optimum conditions for the performance of coagulation and flocculation processes as

the pretreatment of instant coffee wastewater. Each type of the coagulants has its

own characteristic optimum dosage range. There will be poor treatment efficiency if

the coagulant dosage is insufficient or excessive. The study for the dosage effect of

three coagulants (aluminum sulfate, ferric chloride and chitosan) on the residual

pollutants has been undertaken by varying the amount of coagulant in the jar tests,

while keeping other conditions constant. The tests were carried at the initial pH of

the coffee wastewater with the operating conditions: (1) rapid mixing at 250 rpm for

1 minute; (2) slow mixing at 30 rpm for 20 minutes; (3) settling for 30 minutes. The

efficiencies were determined though the removal and reduction of turbidity, TSS,

color and COD. The data for all the experiments are presented in the “Appendix” and

only the results for a more tighten range of dosage are discuss in this section.


The result of the effects of different dosages of aluminum sulfate as sole

coagulant on the residual turbidity, TSS, COD and color in the supernatants are

illustrated in Figure 4.1 while their removal percentage from the wastewater are

presented in Figure 4.2. It is clear that the trends of removal for all parameters are

similar, but with different removal efficiency. The curves show some relationship for

these parameters. Turbidity is associated with the TSS concentration. It is suggested

that color is mainly produced by organic matter that is measured as COD, with some

insoluble forms that exhibited turbidity and suspended solids readings. The removal

of colloidal particles and organic matters by coagulation and flocculation processes

using aluminum sulfate in the wastewater led to the reduction of TSS, turbidity, COD

and color from the wastewater.

56

0

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

2400

0 250 500 750 1000 1250 1500

Dosage (mg/L)

Co

nce

ntr

atio

n (

mg/L

))

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

Co

lor

(PtC

o)

Turbidity

TSS

COD

Color

Figure 4.1: Effect of aluminum sulfate dosage on residual parameters

0

10

20

30

40

50

60

70

80

90

100

0 250 500 750 1000 1250 1500

Dosage (mg/L)

Rem

ov

al E

ffic

ien

cy (

%) )

0

1

2

3

4

5

6

7

8

9

10

11

12

13F

inal

pH

Turbidity

TSS

Color

COD

pH

Figure 4.2: Effect of aluminum sulfate dosage on parameter removals

57

The initial characteristics of the wastewater were 857 NTU of turbidity, 480

mg/L of TSS, 8525 PtCo of color, 2244 mg/L of COD and pH of 5.68. From the

figures, all the residual parameters were decreased while their removal efficiencies

were improved substantially as the dosage of aluminum sulfate was increasing until

1000 mg/L. At this optimal point, the highest removal efficiencies for turbidity, TSS,

color and COD were 97.86%, 95.00%, 87.33% and 48.31%, respectively. The

residual turbidity, TSS, color and COD at the optimum dosage of 1000 mg/L were

18.3 NTU, 24 mg/L, 1080 PtCo and 1160 mg/L. When the dosages were exceeding

1000 mg/L, there was a decrease in the removal efficiency for all the parameters.

According to Hendricks (2006), coagulation by using aluminum sulfate

involves hydrolysis reactions that release proton (H+ ions) to the solution upon

addition of such coagulants. Therefore, the pH of the water was lowering as the

coagulant dosage was increasing as one can see from Figure 4.2. The pH was

decreased from initial 5.68 to 3.85 as 1000 mg/L of aluminum sulfate was added. It

was further reduced to 3.57 when 1500 mg/L of aluminum sulfate was employed.

Increased coagulant dosage decreases the solution pH as alkalinity is consumed. The

hydrolysis species formed are controlled by the final pH of the wastewater after

coagulant addition (Amirtharajah and Mills, 1982).

The destabilization of particles by aluminum sulfate in this study can be

explained by the mechanisms of adsorption and charge neutralization (Metcalf and

Eddy, 2003). The positively charged mononuclear and polynuclear aluminum

hydrolysis products can be adsorbed on the particle surface during coagulation. The

negative surface charges of the colloidal particles are neutralized. The electrostatic

repulsive forces between the particles are eliminated. Thus, aggregation of the

colloidal particles and floc formation occurs because the attractive van der Waals

forces lead to attachment when interparticle contacts occur. If aluminum sulfate is

overdosed beyond its optimum concentration, the charge reversal occurs. The

electrostatic repulsion between the particles that have positive charges will cause

particles restabilization. This phenomenon was clearly proved by the up-and-down

trend of turbidity, TSS, COD and color removals as indicated in Figure 4.2.

58


Besides aluminum sulfate, ferric chloride at different dosages was also

conducted by using jar tests to study its performance. The influences of ferric

chloride dosage on the residue of turbidity, TSS, color and COD are demonstrated in

Figure 4.3. Their removal efficiencies are shown in Figure 4.4. Both figures are

interrelated. From Figure 4.4, it was observed that all the parameters also have a

similar trend of removal by using ferric chloride, with individual percentage at the

particular dosage. It was an up-and-down trend with increasing of dosages. The

removal of TSS, turbidity, COD and color were associated with the removal of

colloidal particles and organic matters in the wastewater by coagulation and

flocculation processes using ferric chloride. As indicated in Figure 4.3, the initial

value for turbidity of wastewater was 863 NTU, TSS was 340 mg/L, color was

10040 PtCo and COD was 2616 mg/L.

0

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

2400

2600

2800

0 250 500 750 1000 1250 1500

Dosage (mg/L)

Conce

ntr

atio

n (

mg/L

))

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

Colo

r (P

tCo)

Turbidity

TSS

COD

Color

Figure 4.3: Effect of ferric chloride dosage on residual parameters

59

0

10

20

30

40

50

60

70

80

90

100

0 250 500 750 1000 1250 1500

Dosage (mg/L)

Rem

ov

al E

ffic

iency

(%

) )

0

1

2

3

4

5

6

7

8

9

10

11

12

13

Fin

al p

H

Turbidity

TSS

Color

COD

pH

Figure 4.4: Effect of ferric chloride dosage on parameter removals

From Figure 4.4 above, the turbidity, TSS, color and COD removals

increased rapidly with an increase in coagulant dosage until it reached an optimum

value at 1000 mg/L. At this point, the dosage of 1000 mg/L ferric sulfate yielded the

highest removal efficiencies for turbidity, TSS, color and COD, with 98.24%,

90.59%, 92.08% and 55.43%, respectively. Turbidity was reduced from the initial

value to 15.2 NTU, TSS to 32 mg/L, color to 795 PtCo, and COD to 1166 mg/L.

Beyond the dosage of 1000 mg/L, the residual of these parameters in the supernatant

were increased whereas the removal efficiencies for all the parameters are decreased

gradually. This could be attributed by the restabilization of colloidal particulates

when coagulant was used at dosages in excess of the optimum value.

Furthermore, ferric ions can act as Bronsted acid, which means that they may

donate a proton (H+ ion) to the solution, thus depressing the pH (Hendricks, 2006).

As demonstrated in Figure 4.4, the pH was decreased from the initial value of 6.44 to

3.45 at optimum dosage of 1000 mg/L, and then to 2.54 at 1500 mg/L ferric chloride.

60

The tri-valent ions, ferric ion (Fe3+

) and aluminum ion (Al3+

) have similar

reactions with water, with difference in the values of the equilibrium constants

(Hendricks, 2006). Thus, the destabilization of particles by ferric chloride can also be

explained by the mechanisms of adsorption and charge neutralization. Adsorption

and charge neutralization involves the adsorption of positively charge mononuclear

and polynuclear ferric hydrolysis species on the surface of colloidal particles. This

will subsequently reduce the negative surface charge on the colloidal particles for

destabilization and floc formation. However, the excess concentration of ferric

chloride beyond its optimum dosage will confer positive charges on the particle

surface (a positive zeta potential) and redispersing the particles.

3.6.3 Chitosan

Besides using the common metal salts of aluminum sulfate and ferric chloride,

one type of inorganic polyelectrolyte, chitosan was also been studied for its

performance on coagulation and flocculation for instant coffee wastewater. As shown

in Figure 4.5, the initial turbidity of the raw wastewater was 440 NTU, TSS was 400

mg/L, color was 12090 PtCo and COD was 3636 mg/L. The effects of employing

chitosan at various dosages on the residual turbidity, TSS, color and COD are then

presented in Figure 4.5 while their removal percentages are illustrated in Figure 4.6.

As in the case of wastewater treatment with aluminum sulfate and ferric

chloride, it was observed that all the parameters have a same trend of removal

efficiency, with different removal percentage by using chitosan. It was found that

with an increase in chitosan dose up to a certain level, the percent removal of all

parameters was increased and then followed by a decreasing trend with further

increases in dose level. The reduction of turbidity, TSS, color and COD is believed

due to the removal of colloidal particles and organic matters by using chitosan in the

coagulation and flocculation processes.

61

0200

400600800

100012001400

1600180020002200

240026002800

300032003400

36003800

0 25 50 75 100 125 150 175

Dosage (mg/L)

Co

nce

ntr

atio

n (

mg/L

))

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

12000

13000

Co

lor

(PtC

o)

Turbidity

TSS

COD

Color

Figure 4.5: Effect of chitosan dosage on residual parameters

0

10

20

30

40

50

60

70

80

90

100

0 25 50 75 100 125 150 175

Dosage (mg/L)

Rem

ov

al E

ffic

iency

(%

) )

1

2

3

4

5

6

7

8

9

Fin

al p

HTurbidityTSSColorCODpH

Figure 4.6: Effect of chitosan dosage on parameter removals

62

From the figures, the residues of all parameters in the supernatant were

decreased while their removal efficiencies were improved simultaneously with an

increased dosage of chitosan. The turbidity, TSS, color and COD removals increased

rapidly as the dosage of chitosan was increasing until 100 mg/L. At this point, the

best results were obtained. The highest removal efficiencies for turbidity, TSS, color

and COD are 96.64%, 87.00%, 84.74% and 42.79%, respectively. The incremental of

dosage beyond 100 mg/L increased the value of these residual in the supernatant

while their removal efficiencies are decreased gradually. Besides, the addition of

increasing amounts of acidic chitosan solutions leaded to the decreasing of final pH,

from initial 6.45 to 3.71 at 100 mg/L and further declined to 2.42 at 150 mg/L.

The results reveal that the charge neutralization and polymer bridging play an

important role in the coagulation and flocculation processes by using chitosan. The

polymer adsorption increased as the charge density of the polymer increased. The

higher the dosage of chitosan with a higher charge density, the more likely was the

charge neutralization, polymer adsorption and bridging, and then aggregation

between colliding particles. This was proved by the trend of increasing in removal

efficiency until the optimum dosage of 100 mg/L as shown in Figure 4.6. The

optimum amount of chitosan in the wastewater caused larger amounts of colloidal

particles to aggregate and settle. When the dosage of chitosan was increased, more

functional groups were protonated and increase the amount of accessible NH3+.

These cationic polyelectrolytes reacted with negatively charged particles in the

wastewater, destabilized the charged particles and then built agglomerates.

However, an over optimum amount of chitosan in the wastewater would

cause restabilization of coagulated particles. For concentrations higher than 100

mg/L, there was an increase in the residual turbidity, TSS, color and COD indicated

that the solution has gone through the point of net electrical charge and the added

chitosan had increased the positive charge of the collides. This situation would

redisperse the aggregated particle and disturb particle settling. Excess polymer was

adsorbed on the colloidal surfaces and produced restabilized colloids that caused the

electrostatic repulsion among the colloids and hindrance of floc formation.

63

3.7 Effect of pH

The influence of different pH was further investigated as the pH is an

important factor in the coagulation process. The use of coagulant at its optimum pH

displays maximum pollutant removal with the highest performance of wastewater

pretreatment. To optimize the pH of the coagulation process, a known volume of pre-

determined optimum value of each sole coagulant (aluminum sulfate, ferric chloride

and chitosan solution) was added to a jar containing 400 mL of wastewater at the pH

values from 4 to 8, adjusted with 0.25 M HCl or 0.25 M NaOH solution. The

operating conditions of jar tests were: (1) rapid mixing at 250 rpm for 1 minute; (2)

slow mixing at 30 rpm for 20 minutes; (3) settling for 30 minutes. The efficiencies

based on the removal and reduction of turbidity, TSS, color and COD in the

wastewater were used to determine the optimum pH. The data for all the experiments

are presented in the “Appendix”


Figure 4.7 shows the effects of pH on the residual turbidity, TSS, color and

COD by using fixed 1000 mg/L of aluminum sulfate in the jar tests. Their removal

efficiencies are presented in Figure 4.8. There was 480 mg/L TSS, 871 NTU, 8370

PtCo and 2040 mg/L COD in the initial raw wastewater. For pH range 4 to 8, the

turbidity level of supernatant was almost constant; in the range 14.6-18.5 NTU with a

reduction around 98%. For TSS removals, there was an improvement from pH 4 to 6,

stable at pH 6 to 7 with the highest 95% removal and residual 24 mg/L. Similarly,

color and COD removal also followed this trend. More than 87% of color was

removed from pH 4 to 6, and then almost stable between pH 6 to 8 with around 91%

removal (690-720 PtCo). The removal of COD was gradually increased to pH 7 with

the highest 50% removal as 1020 mg/L, and slightly dropped at pH 8. Therefore, the

optimum pH range by using aluminum sulfate was 6 to 8, with pH 7 was preferable.

64

0

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

3 4 5 6 7 8 9

pH

Conce

ntr

atio

n (

mg/L

))

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

Colo

r (P

tCo)

Turbidity

TSS

COD

Color

Figure 4.7: Effect of different pH on the residual parameters by aluminum sulfate

35

40

45

50

55

60

65

70

75

80

85

90

95

100

3 4 5 6 7 8 9

pH

Rem

ov

al E

ffic

iency

(%

) )

0

1

2

3

4

5

Fin

al p

H

Turbidity

TSS

Color

COD

pH

Figure 4.8: Effect of different pH on the parameter removals by aluminum sulfate

Initial

65

The charge on hydrolysis byproducts of metal salt and the precipitation of

metal hydroxides are both dependent on pH because the pH would influence the

hydrolysis equilibrium of coagulant species. At pH values below their isoelectric

point (IEP) of the metal hydroxide, the hydrolysis byproducts (hydroxo-metallic

complexes) posses a positive charge that are able to adsorb to the surface of negative

colloids. A reduction of the zeta potential and charge neutralization could cause the

destabilization of negatively charged colloidal particles under low pH for floc

formation. In the formation of the insoluble metallic hydroxide at IEP, there is

enmeshing of the negative colloids with the precipitate, termed as sweep coagulation.

Negatively charge species which are predominant above IEP are ineffective for the

destabilization of negatively charged colloids.

From the equilibrium concentrations of hydrated aluminum (III) complexes in

a solution in contact with Al(OH)3(s), aluminum from Al3+

converts to mono- and

polynuclear cationic hydrolysis products at lower pH values (Amirtharajah and Mills,

1982). The positive charge of aluminum hydrolysis species increases when pH is

increasing. According to Metcalf and Eddy (2003), the operating region for

aluminum hydroxide precipitation is from a pH range of 5 to 7, with minimum

solubility occurring at a pH of 6. This can be proved by the improvement of pollutant

removals from acidic to neutral condition as shown in Figure 4.8. With increasing pH

up to 5, contribution of the charge neutralization to particles removal increased,

whereas, after pH 5 contribution of the charge neutralization decreased and

contributions of the adsorption and entrapment predominated for colloids removal.

The results from the study suggested that the optimal pH by using aluminum

sulfate dose of 1000 mg/L was 7, where the removals of particles were mainly due to

sweep floc mechanism of aluminum hydroxide precipitate. The large aluminum

hydroxide floc that can settle easily were formed at neutral condition. As they settled,

they “sweep” through the wastewater containing colloidal particles. The colloidal

particles was enmeshed in the flocs and then settled together. The amorphous, fractal

nature of the aluminum hydroxide floc provides places for such enmeshment and the

surface area most likely is very large (Hendricks, 2006).

66


Jar tests for ferric chloride were also conducted, at fixed dosage of 1000

mg/L but different pH values. The influences of different pH on the residual TSS,

turbidity, color and COD are illustrated in Figure 4.9 whereas Figure 4.10 shows the

effects of pH on their removal efficiencies. It appeared that with increasing the

coagulation pH, all parameters removals have a significant improvement, from initial

858 NTU of TSS, 440 mg/L of TSS, 8401 PtCo of color and 2244 mg/L of COD. A

low residual turbidity level in the supernatant was obtained for pH 4 to 8, with the

value below 15 NTU, corresponding to the 98% removal. TSS in the raw wastewater

was reduced to 40 mg/L at pH 4, and further declined to 16 mg/L with 96.36%

removal at pH 6 to 8. The parameter of color and COD also presented a clear picture

of decreasing from pH 4 to 7 and then almost constant at pH 7 to 8, with residual

462-469 PtCo of 94% removal and residual 2244 mg/L COD of 64% removal. Thus,

the optimum pH range by using ferric chloride was 7 to 8, with pH 7 was preferable.

0

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

2400

3 4 5 6 7 8 9

pH

Co

nce

ntr

atio

n (

mg/L

))

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

Colo

r (P

tCo

)Turbidity

TSS

COD

Color

Figure 4.9: Effect of different pH on the residual parameters by ferric chloride

Initial

67

45

50

55

60

65

70

75

80

85

90

95

100

3 4 5 6 7 8 9

pH

Rem

oval

Eff

icie

ncy

(%

) )

1

2

3

4

5

Fin

al p

H

Turbidity

TSS

Color

COD

pH

Figure 4.10: Effect of different pH on the parameter removals by ferric chloride

Reynolds and Richards (1996) suggest the optimum range for ferric chloride

is from about 4 to 12. According to Metcalf and Eddy (2003), the operating region

for ferric hydroxide precipitation is from a pH range of 7 to 9, with minimum

solubility occurring at a pH of 8. This is proved by the increasing of pollutant

removals from acidic to neutral condition as shown in Figure 4.10. The results reveal

that with increasing pH from 4 to 7, contribution of adsorption and charge

neutralization for particles removal increased. After pH 7, contribution of charge

neutralization decreased while contributions of the adsorption and entrapment or

sweep coagulation predominated.

The optimal pH of 7 was obtained for coagulation and flocculation processes

of coffee wastewater by using ferric chloride with the dosage of 1000 mg/L. At pH 7,

the removals of particles from the wastewater were predominated by the sweep floc

mechanism. The colloidal particles were enmeshed in the precipitate ferric hydroxide

flocs that were formed at this optimal pH.

68

3.7.3 Chitosan

The influence of pH (pH ranges between 4 and 8) by using a fixed 100 mg/L

chitosan on the reduction of turbidity, TSS, color and COD was investigated. The

results for these residuals in supernatant are presented in Figure 4.11 while their

removal efficiencies are illustrated in Figure 4.12. Results indicated that the

percentage of removal efficiency followed the similar trend for all pollutants, which

was an up-and-down curve. The initial value for turbidity of wastewater was 415

NTU, TSS was 340 mg/L, color was 12285 PtCo and COD was 4141 mg/L. There

was a poor performance for all parameter removals at the low pH of 4 and promptly

improved as pH was increasing up to 6. The highest removal efficiencies obtained at

this point indicated that the optimum pH for chitosan was 6. The residue for TSS,

turbidity, color and COD were 44 mg/L, 15.1 NTU, 1665 PtCo and 2415 mg/L, with

the removal efficiencies of 87.06%, 96.39%, 86.45% and 41.68%, respectively. After

pH 6, these residual parameters were increased again with declining performances.

0200400600800

10001200140016001800200022002400260028003000320034003600380040004200

3 4 5 6 7 8 9

pH

Con

centr

atio

n (

mg/L

))

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

12000

13000

Co

lor

(PtC

o)

Turbidity

TSS

COD

Color

Figure 4.11: Effect of different pH on the residual parameters by chitosan

Initial

69

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

3 4 5 6 7 8 9

pH

Rem

oval

Eff

icie

ncy

(%

) )

1

2

3

4

5

6

Fin

al p

H

Turbidity

TSS

Color

COD

pH

Figure 4.12: Effect of different pH on the parameter removals by chitosan

Chitosan performed the best result for destabilization of colloidal particles at

slightly acidic condition. There will be a poor result at strongly acidic and alkaline

condition that was indicated in this study. The effects of pH can be explained by the

functional amino group of chitosan that are important for charge neutralization of

colloidal particulates. A linear relationship between the degree of deacetylation (DD)

of chitosan and the optimal chitosan dosage indicates that amino group of chitosan is

the active site for coagulation (Huang et al., 2000). The cationic nature of chitosan is

strongly depended on the pH. The equilibrium reaction of amine group is shown as

follows:

-NH2 + H3O+ ↔ -NH3

+ + H2O (4.1)

From equation 4.1, the reaction shift to the right as the concentration of H+

ion increase. The equilibrium was predominantly (99.97%) shift to the right at pH 3

(Ashmore and Hearn, 2000). From Figure 4.12, there was a poor performance of

coagulation and flocculation process by using chitosan at pH 4. Strong acidic

70

condition will lead to very strong cationic charge on chitosan. At this lower pH,

particles restabilization due to reversal of surface charge was occurred and then

increased the residual pollutants in the supernatant. According to Huang and Chen

(1996), the reversal of surface charge is more likely at low pH as the reversal of zeta

potential can be observed with excess concentration of chitosan at pH 4 while it is

absent at pH 7. Divakaran and Pillai (2004) also reported that chitosan was very

soluble and incapable in producing floc at low pH value.

Charge neutralization was the principle mechanism of coagulation and

flocculation process at low pH. It was assumed that the particles destabilization and

colloidal particles removal after from pH 4 to 6 as shown in Figure.4.12 was mainly

due to the charge neutralization. Domard et al. (1989) mentioned that there are 90%

of the functional group of NH2 on the chitosan was protonated at pH 4 and gradually

decreased to about 50% as pH increased to 6. According to the zeta-potential

measurements by Huang and Chen (1996), the isoelectric point of chitosan was

around 8.9 and the positive charge on chitosan surface decreased as the pH changing

from 4 to this value. Therefore, the positive charges on the chitosan surface will

significantly decrease as solution pH increase.

Figures 4.12 revealed that the optimum pH for chitosan was 6 as the highest

removal efficiency for all parameters was achieved at this point. The contribution of

charge neutralization by chitosan to destabilize the colloidal particles becomes less

important at pH 6. It was suggested that the coagulation and flocculation by chitosan

at this optimum pH 6 was due to the combination of charge neutralization and

polymer bridging mechanism. Both charge neutralization and bridging mechanism

can be invoked due to the cationic behavior and higher molecular weight of chitosan

(Roussy et al., 2004). When the pH was increased from 6 to 9, the removal

percentages for all the parameters were gradually decreased. Chitosan will loss its

cationic nature in alkaline condition as the isoelectric point of chitosan is around pH

8.9. The polymer bridging mechanism that dominated in this region was not effective

for particles destabilization. The higher concentration of chitosan is required to

achieve a better performance in alkaline condition (Roussy et al., 2005).

71

3.8 Comparison of Coagulants

The optimum conditions for coagulation and flocculation process of instant

coffee wastewater based on dosage and pH for three different types of coagulants

(aluminum sulfate, ferric chloride and chitosan) which were analyzed earlier in

section 4.2 and 4.3 are tabulated in Table 4.2. Aluminum sulfate and ferric chloride

performed their best results at the same optimum condition, with dosage of 1000

mg/L and pH 7. For chitosan, its optimum dosage was 100 mg/L at pH 6.

Table 4.2: Optimum conditions for coagulants

Coagulant Optimum Dosage Optimum pH

Aluminum Sulfate 1000 mg/L 7

Ferric Chloride 1000 mg/L 7

Chitosan 100 mg/L 6

For a better comparison among these three types of coagulants, each single

coagulant was added to an individual jar containing 400 mL of wastewater at their

optimum value of dosage and pH with the operating conditions: (1) rapid mixing at

250 rpm for 1 minute; (2) slow mixing at 30 rpm for 20 minutes; (3) settling for 30

minutes. The characteristics of raw coffee wastewater used for this jar test was 463

NTU of turbidity, 420 mg/L of TSS, 12474 PtCo of color and 3636 mg/L of COD.

Figure 4.13 shows the photo of the above jar test after 30 minutes of settling. The

results were tabulated in Table 4.3 while the effects on the removal and reduction of

turbidity, TSS, color and COD from the wastewater was demonstrated in Figure 4.13.

(a) (b) (c)

Figure 4.13: Jar test using (a) aluminum sulfate, (b) ferric chloride and (c) chitosan

72

Table 4.3: Comparison of each coagulant at optimum conditions

Coagulant

Parameter

Initial

Raw

Wastewater Aluminum

Sulfate

Ferric

Chloride Chitosan

Standard Ba

Turbidity

(NTU) 463 57.2 21.4 14.1 -

TSS

(mg/L) 420 48 36 36 100

Color

(PtCo) 12474 1236 624 1428 -

COD

(mg/L) 3636 1600 1220 1940 100

Sludge Volume

(mL) - 87 103 60 - a Standard B of the Environmental Quality (Sewage and Industrial Effluents)

Regulations 1979, under the Environmental Quality Act (EQA) 1974

0

10

20

30

40

50

60

70

80

90

100

Turbidity TSS Color COD Sludge Settled

Parameter

Rem

oval

Eff

icie

ncy

(%

)))))

05101520253035404550556065707580859095100105

Slu

dge

Vo

lum

e (m

L))))

Figure 4.14: Comparison for aluminum sulfate, ferric chloride and chitosan

Aluminum Sulfate Ferric Chloride Chitosan

73

It is important to study whether the residual parameters for each coagulant as

shown in Table 4.3 are different significantly. Based on the concentration of TSS,

turbidity, COD and color remaining in the supernatants after the coagulation and

flocculation process by various sole coagulants, a statistical approach to compare the

differences of the mean values for each parameter was carried out using t-test

statistic. All the computed t values were calculated and shown in Appendix J. The

critical value of t (tcritical) was obtained at the significant level of α at 0.05. If the

computed t value is greater than tcritical or less than - tcritical, the null hypothesis for the

group means are equal is rejected. From the t-test statistic, it can be seen that there

was a significant differences exist among the mean values for all the parameters.

As indicated in Figure 4.15, chitosan achieved the best result for TSS and

turbidity reduction from the wastewater, followed by ferric chloride and aluminum

sulfate. 96.95% of turbidity and 91.43% of TSS was removed by using chitosan,

although the dosage of chitosan of 100mg/L was 10 times much lesser than

aluminum chloride and ferric chloride. This is because the amount of coagulant

required for destabilizing the colloidal particles is lesser for a coagulant with the

higher charge density, such as chitosan.

On the other hand, inorganic metal coagulants produced better achievement

for color and COD removal from instant coffee wastewater, compared with chitosan.

Ferric chloride exhibited the best performance in removing the color and COD by

coagulation and flocculation, with highest removal of 95% and 66.45%, respectively.

This was followed by the aluminum sulfate, which resulted 90% and 56% removal

for color and COD. 88.55% of color and 46.46% of COD in the wastewater could be

removed by using chitosan.

From Figure 4.15 again, it was found that all the coagulants were successfully

to reduce the level of turbidity and TSS, with more than 87% removal. Coagulation

and flocculation process was effective in colloidal particles removal from wastewater.

The concentration of TSS in the supernatant was below 100 mg/L that was complied

74

with Standard B of EQA 1974. However, the removal efficiency for COD recorded

for all coagulants was below 66.5%, with the lowest value of residual COD was 1220

mg/L by using ferric chloride that was still above the limit of 100 mg/L COD. As

COD are associated with the strength of organic matter in the wastewater, it can be

stated that the coagulants used in the study has only little effect on the removal of

dissolved organic matter compared with the suspended colloidal organics.

In addition to pollutants removal, sludge production by all coagulants, by

measuring the volume of sludge settled in each jar after 1 hour was conducted for

comparison. The sources, characteristics and quantities of the sludge to be handled

will affect the solids processing, treatment and disposal facilities (Metcalf and Eddy,

2003). The handling treatment and removal of the sludge generated in the

coagulation and flocculation process are important aspects to consider when

choosing the products to be used as coagulant (Aguilar et al., 2002). The amount and

the characteristics of the sludge produced during the coagulation and flocculation

process are highly dependent on the specific coagulants used.

From the observation during the jar test, chitosan showed a much faster

sedimentation, followed by aluminum sulfate and ferric chloride. Chitosan promoted

the faster aggregation of colloids, by the formation of particles with sufficient size

which can be settled faster and easily. As shown in Figure 4.13, the addition of

chitosan produced the lowest volume of sludge compared to the result obtained by

the inorganic metal coagulants, with the amount of 60 mL. When aluminum sulfate

was added, 87 mL of sludge was measured. The highest sludge volume was

produced by using ferric chloride, which was 103 mL.

The cost evaluation of using aluminum sulfate, ferric chloride and chitosan

each has been done and the results are shown in Table 4.4. The cost of coagulant was

calculated by applying the coagulant at its respective optimum dosage for

coagulation and flocculation of instant coffee wastewater on a day basis. The

flowrate of raw wastewater produced from the instant coffee industry was 180

75

m3/day. From Table 4.4, the costs of inorganic metal coagulants were much lower

than the chitosan. The use of ferric chloride can be considered as economical in pre-

treatment of instant coffee wastewater. The cost of ferric chloride using per day,

RM20,340 was the lowest, which was 16.8% lower than aluminum sulfate and

119.8% lower than chitosan.

Table 4.4: Cost comparison of each coagulant

Coagulant

Parameter Aluminum

Sulfate

Ferric

Chloride Chitosan

Unit Cost (RM/kg) 132 113 2,484

Total Cost (RM/day) 23,760 20,340 44,712

Considering the results obtained for removal efficiencies of tubidity, TSS,

color and COD, and well as the amount of sludge to be treated and the cost

comparison of coagulants, the most suitable coagulant for the pretreatment of instant

coffee wastewaters would be ferric chloride. This was due to its high performance,

effectiveness and more economical. In addition, chitosan is recommended as a

suitable and potential coagulant resource if its cost can be reduced by more

economical production method in the future. This is because chitosan has excellent

properties such as biodegradability, biocompability, adsorption property, flocculating

ability, polyelectrolisity and its possibilities of regeneration in number of

applications (Ravi, 2000).

CHAPTER 5

CONCLUSION AND RECOMMENDATIONS

1.7 Conclusions

The purpose of this study is to investigate the performance of coagulation and

flocculation by using aluminum sulfate, ferric chloride and chitosan as a

pretreatment for instant coffee industrial wastewater. Each type of the coagulants

has its own characteristic optimum conditions where the best results of pollutants

removal are achieved. The reduction and removal of total suspended solids (TSS),

turbidity, chemical oxygen demand (COD) and color in the supernatant are used as

indicator to determine the optimum conditions based on dosage and pH for

coagulation and flocculation process.

The optimum dosage for aluminum sulfate and ferric chloride was 1000 mg/L.

Since both coagulants are inorganic metal salts, the up-and-down removal trends

obtained for all parameters in the supernatant could be explained by the mechanism

of adsorption and charge neutralization. The reduction of turbidity, TSS, color and

COD is believed due to the removal of colloidal particles and organic matters. When

aluminum sulfate or ferric chloride was added during coagulation, the positively

charged mononuclear and polynuclear hydrolysis products would adsorb on the

77

particle surface, causing particles destabilization and floc formation. If aluminum

sulfate or ferric chloride was overdosed, there will be charge reversal on the colloidal

particles. The electrostatic repulsion between the particles with positive charges

caused particles restabilization and deteriorated the removal efficiencies.

Furthermore, the effects of pH for aluminum sulfate and ferric was also

similar. The charge on hydrolysis species of metal salt and the precipitation of metal

hydroxides are both dependent on pH as the pH would influence the hydrolysis

equilibrium of coagulant species. The optimal pH for both aluminum sulfate and

ferric chloride at 1000 mg/L was 7, with the removals of particles were mainly due to

the sweep floc mechanism of hydroxide precipitate. At optimum pH, the large

hydroxide floc that can be settled easily were formed. The colloidal particles were

enmeshed and removed in these flocs. The amorphous and fractal nature of the

hydroxide floc provides places for such enmeshment.

For chitosan, the optimum dosage was 100 mg/L. Charge neutralization and

polymer bridging were contributed for colloids removal by using chitosan. When the

dosage of chitosan was increased, more functional amino groups were protonated

and increased the cationic charge of chitosan to neutralize the particle surface charge

and subsequently form particle bridges to interconnect particles in agglomerates. The

optimum amount of chitosan in the wastewater caused larger amounts of colloidal

particles to aggregate and settle. However, an over optimum dosage of chitosan

would cause restabilization of coagulated particles. Excess polymer was adsorbed on

the colloidal surfaces and produced restabilized colloids that hinder floc formation.

The optimum pH for chitosan was slightly acidic, at pH 6 with the

combination of charge neutralization and polymer bridging mechanism were

contributed for its coagulation and flocculation process. There will be a poor result at

strongly acidic and alkaline condition. At lower pH, particles restabilization due to

reversal of surface charge was occurred. When the pH was increased from 6 to 9, the

removal percentages for all the parameters were gradually decreased as cationic

78

nature of chitosan was lost in alkaline condition and the polymer bridging

mechanism was ineffective for particles destabilization.

The dosage of chitosan of 100 mg/L was 10 times lesser than aluminum

chloride and ferric chloride as chitosan has higher charge density. For comparison

among the coagulants used, chitosan exhibited the best result for turbidity and TSS

removal. 96.95% of turbidity and 91.43% of TSS was removed by using chitosan.

This was followed by ferric chloride (95.38% turbidity and 91.43% TSS removal)

and aluminum sulfate (87.65% turbidity and 88.57% TSS removal). The residual

TSS level that below 100 mg/L was complied with Standard B of EQA 1974. On the

other hand, ferric chloride was the best coagulant for color and COD removal, with

95% and 66.45%, respectively. This was followed by the aluminum sulfate (90%

color and 56% COD removal) and chitosan (88.55% color and 46.46% COD

removal). The lowest value of residual COD, 1220 mg/L, by using ferric chloride

was still above the limit of 100 mg/L COD as it has only little effect on the removal

of dissolved organic matter.

In addition, chitosan showed a much faster sedimentation during jar test,

followed by aluminum sulfate and ferric chloride. Chitosan produced the faster

aggregation of colloids, by the formation of particles with sufficient size that can be

settled faster and easily. Thus, the lowest volume of sludge was obtained by chitosan,

with the amount of 60 mL. This was followed by aluminum sulfate with 87 mL of

sludge. 103 mL of sludge was produced by using ferric chloride.

Coagulation and flocculation process was effective for the removal of

colloidal particles from coffee wastewater. In short, all the coagulants used in this

study can be used for pretreatment of coffee wastewater, with ferric chloride was

preferable. This is due to it high performance and effectiveness. Furthermore, it can

be considered more economical in the pre-treatment of instant coffee wastewater.

The cost of ferric chloride using per day, RM20,340 was the lowest, which was

16.8% lower than aluminum sulfate and 119.8% lower than chitosan.

79

1.8 Recommendations

a) Beside the effects of dosage and pH, other factors such as optimum mixing

rate, mixing time, sedimentation time and temperature can be determined.

Their influences on the performance of coagulation and flocculation process

for each types of coagulant can be investigated.

b) As the characteristics and contents of the instant coffee wastewater were not

constant and varied by the industry activities, it is suggested to study the

effect of different initial characteristics of wastewater on the performance of

coagulation and flocculation process.

c) It is recommended to evaluate and characterize the surface charge of colloidal

particles in the coffee wastewater before and after the coagulation and

flocculation process in the jar tests. It can be analyzed by using zeta potential

measurements to have a better study of mechanism that dominated in the

coagulation and flocculation process for each coagulant.

d) The combination of aluminum sulfate or ferric chloride with chitosan or other

polyelectrolytes could be carried out to investigate their potential and

effectiveness in the coagulation and coagulation of instant coffee wastewater.

e) It is suggested to further study the characterization of the sludge produced

from each coagulant. Measurement of density and number of coagulation

flocs can be conducted to confirm the findings of this study.

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Appendix A

Apparatus used for analytical methods

HACH Ratio/XR turbidimeter Filtering apparatus with vacuum pump

Oven and desiccator Analytical balance

Spectrophotometer DR/2000 pH meter

88

Appendix B

Results of jar test using aluminum sulfate to determine optimum dosage (wide range)

Jar No. 1 2 3 4 5 6

Aluminum Sulfate Dosage (mg/L) Parameter

0 500 1000 1500 2000 2500

Final pH 4.57 4.18 3.85 3.69 3.51 3.38

Turbidity (NTU) 1835 116 38 50 56 57

Removal Efficiency (%) 0.00 93.68 97.93 97.28 96.95 96.89

TSS (mg/L) 2280 320 140 160 220 240


0

10

20

30

40

50

60

70

80

90

100

0 500 1000 1500 2000 2500 3000

Dosage (mg/L)

Rem

oval

Eff

icie

ncy

(%

) )

1

2

3

4

5

6

Fin

al p

H

Turbidity

TSS

pH

Jar No. 1 Jar No. 2 Jar No. 3


89

Appendix B.1

Results of jar test using aluminum sulfate to determine optimum dosage

Jar No. 1 2 3 4 5 6

Aluminum Sulfate Dosage (mg/L) Parameter

0 500 750 1000 1250 1500

Final pH 5.68 4.57 4.13 3.85 3.71 3.57

Turbidity (NTU) 857 307 125.7 18.3 25.6 40.1


TSS (mg/L) 480 188 80 24 28 32


Color (PtCo) 8525 5940 2760 1080 1410 1605


COD (mg/L) 2244 1820 1400 1160 1360 1540




90

1 2 3 4 5 6

Appendix C

Results of jar test using aluminum sulfate to determine optimum pH

Jar No. 1 2 3 4 5 6

pH Parameter

Initial 4 5 6 7 8

Final pH 4.84 2.24 3.15 3.61 3.86 3.88

Turbidity (NTU) 871 16.7 16.3 14.6 17.3 18.5


TSS (mg/L) 480 36 32 24 24 28


Color (PtCo) 8370 1076 865 720 705 690


COD (mg/L) 2040 1240 1160 1100 1020 1040




91

0

10

20

30

40

50

60

70

80

90

100

0 500 1000 1500 2000 2500 3000

Dosage (mg/L)

Rem

ov

al E

ffic

ien

cy (

%)

)

1

2

3

4

5

6

7

8

Fin

al p

H

Turbidity

TSS

pH

Appendix D

Results of jar test using ferric chloride to determine optimum dosage (wide range)

Jar No. 1 2 3 4 5 6

Ferric Chloride Dosage (mg/L) Parameter

0 500 1000 1500 2000 2500

Final pH 4.95 4.47 3.71 3.03 2.78 2.20

Turbidity (NTU) 1815 441 25.8 167 239 228


TSS (mg/L) 2060 340 60 220 350 330




92

1 2 3 4 5 6

Appendix D.1

Results of jar test using ferric chloride to determine optimum dosage

Jar No. 1 2 3 4 5 6

Ferric Chloride Dosage (mg/L) Parameter

0 500 750 1000 1250 1500

Final pH 6.44 4.92 4.29 3.45 2.94 2.54

Turbidity (NTU) 863 334 58.4 15.2 91.7 318


TSS (mg/L) 340 160 48 32 60 120


Color (PtCo) 10040 4500 2760 795 1170 3935


COD (mg/L) 2616 1793 1518 1166 1188 1529




93

1 2 3 4 5 6

Appendix E

Results of jar test using ferric chloride to determine optimum pH

Jar No. 1 2 3 4 5 6

pH Parameter

Initial 4 5 6 7 8

Final pH 4.94 2.24 3.15 3.61 3.86 3.88

Turbidity (NTU) 858 14.7 11.8 9.7 11.8 12.7


TSS (mg/L) 440 40 20 16 16 16


Color (PtCo) 8401 1386 756 553 462 469


COD (mg/L) 2244 1177 858 847 803 792




94

0

10

20

30

40

50

60

70

80

90

100

0 50 100 150 200 250 300

Dosage (mg/L)

Rem

ov

al E

ffic

ien

cy (

%))

1

2

3

4

5

6

7

8

9

10

Fin

al p

H

Turbidity

TSS

pH

Appendix F

Results of jar test using chitosan to determine optimum dosage (wide range)

Jar No. 1 2 3 4 5 6

Chitosan Dosage (mg/L) Parameter

0 50 100 150 200 250

Final pH 6.46 5.23 3.70 2.42 1.75 1.46

Turbidity (NTU) 435 168.8 18.3 219 171 193


TSS (mg/L) 380 290 52 230 260 220




95

Appendix F.1

Results of jar test using chitosan to determine optimum dosage

Jar No. 1 2 3 4 5 6

Chitosan Dosage (mg/L) Parameter

0 50 75 100 125 150

Final pH 6.45 5.21 4.24 3.71 2.94 2.42

Turbidity (NTU) 440 153.4 46.7 14.8 32.1 218


TSS (mg/L) 400 230 87 52 64 230


Color (PtCo) 12090 9295 3120 1845 2595 7470


COD (mg/L) 3636 3360 2540 2080 2240 2860




96

1 2 3 4 5 6

Appendix G

Results of jar test using chitosan to determine optimum pH

Jar No. 1 2 3 4 5 6

pH Parameter

Initial 4 5 6 7 8

Final pH 6.38 1.85 2.60 3.18 3.60 3.93

Turbidity (NTU) 418 252 176.5 15.1 15.5 32.4


TSS (mg/L) 340 180 105 44 40 48


Color (PtCo) 12285 8840 5440 1665 2070 2190


COD (mg/L) 4141 3234 2835 2415 2436 2562




97

Appendix H

Results of jar test using aluminum sulfate, ferric chloride and chitosan

Jar No. 0 1 2 3

Coagulant

Aluminum

Sulfate

Ferric

Chloride Chitosan

1000 mg/L 1000 mg/L 100 mg/L

Parameter

Initial

Raw

Wastewater

pH 7 pH 7 pH 6

Final pH 6.45 4.54 3.99 3.18

Turbidity (NTU) 463 57.2 21.4 14.1

Removal Efficiency (%) 0.00 87.65 95.38 96.95

TSS (mg/L) 420 48 36 36


Color (PtCo) 12474 1236 624 1428


COD (mg/L) 3636 1600 1220 1940


Sludge Volume (mL) 87 103 60

98

Rapid Mixing Slow Mixing

Settling (0 minute) Settling (1minute)

Settling (5 minutes)





1 2 3

1 2 3

1 2 3

99

Appendix I

Cost comparison for aluminum sulfate, ferric chloride and chitosan

Coagulant

Parameter Aluminum

Sulfate

Ferric

Chloride Chitosan

Optimum Dosage (mg/L) 1,000 1,000 100

Flowrate of Wastewater

(L/day) 180,000 180,000 180,000

Dosage required (kg/day) 180 180 18

Unit Cost (RM/kg) 132 113 2,484

Total Cost (RM/day) 23,760 20,340 44,712

100

Appendix J

Results of statistical analysis

For t-statistic: t = (µ2 - µ1) / √(S12/n1)+(S2

2/n2)

The computed value of t would be compared to the critical value at t(α;n1+n2-2).

Level of significance for one-tailed test, α = 0.05

Critical value of t(α;n1+n2-2) = 2.132

Null Hypothesis: Ho : µ1 = µ2

Alternative Hypothesis: H1 : µ1 < µ2 [ Reject Ho if t < -tcritical ]

H1 : µ1 > µ2 [ Reject Ho if t > tcritical ]

a) Turbidity

Coagulant Parameter Aluminum

Sulfate

Ferric

Chloride Chitosan

57.9 20.9 13.2

57.2 21.4 14.1 Turbidity (NTU)

56.5 21.9 15.0

Mean, µ 57.2 21.4 14.1

No. of Samples, n 3 3 3

Standard

Deviation, S 0.7 0.5 0.9

µ1 µ2 df Tcritical t-value Result

Aluminum

Sulfate

Ferric

Chloride 4 2.132 72.082 Reject Ho µ1 > µ2

Chitosan 4 2.132 65.474 Reject Ho µ1 > µ2


Ferric

Chloride

Aluminum

Sulfate 4 -2.132 -72.082 Reject Ho µ1 < µ2


101


Chitosan

Aluminum


Ferric

Chloride 3 -2.353 -12.281 Reject Ho µ1 < µ2

b) TSS

Coagulant Parameter Aluminum

Sulfate

Ferric

Chloride Chitosan

52 40 32

48 36 36 TSS (mg/L)

44 32 40

Mean, µ 48 36 36


Standard

Deviation, S 4.0 4.0 4.0


Aluminum

Sulfate

Ferric




Ferric

Chloride

Aluminum


Chitosan 4 2.132 0.000

Fail to

reject Ho µ1 = µ2


Chitosan

Aluminum


Ferric

Chloride 4 2.132 0.000

Fail to

reject Ho µ1 = µ2

102

c) Color

Coagulant

Parameter Aluminum

Sulfate

Ferric

Chloride Chitosan

1,236 618 1,434

1,236 624 1,428 Color (PtCo)

1,236 630 1,422

Mean, µ 1236 624 1428


Standard

Deviation, S 0 6 6


Aluminum

Sulfate

Ferric


Chitosan 2 -2.920 -55.426 Reject Ho µ1 < µ2


Ferric

Chloride

Aluminum

Sulfate 2 -2.920

-

176.669 Reject Ho µ1 < µ2

Chitosan 4 -2.132

-

164.116 Reject Ho µ1 < µ2


Chitosan

Aluminum

Sulfate 2 2.920 55.426 Reject Ho µ1 > µ2

Ferric


103

d) COD

Coagulant

Parameter Aluminum

Sulfate

Ferric

Chloride Chitosan

1640 1240 1920

1600 1220 1940 COD (mg/L)

1560 1200 1960

Mean, µ 1600 1220 1940


Standard

Deviation, S 40 20 20


Aluminum

Sulfate

Ferric


Chitosan 3 -2.353 -13.168 Reject Ho µ1 < µ2


Ferric

Chloride

Aluminum


Chitosan 4 2.132 -44.091 Reject Ho µ1 < µ2


Chitosan

Aluminum

Sulfate 3 2.353 13.168 Reject Ho µ1 > µ2

Ferric


Documents

pretreatment of instant coffee wastewater by coagulation and