USE OF CALCIUM ALGINATE AS A COAGULANT IN WATER TREATMENT

A THESIS SUBMITTED TO

THE GRADUATE SCHOOL OF NATURAL AND APPLIED

SCIENCES

OF

MIDDLE EAST TECHNICAL UNIVERSITY

BY

HALE AYLİN ÇORUH

IN PARTIAL FULFILLMENT OF THE REQUIREMENTS

FOR

THE DEGREE OF MASTER OF SCIENCE

IN

DEPARTMENT OF ENVIRONMENTAL ENGINEERING

SEPTEMBER 2005

i

Approval of the Graduate School of Natural and Applied Sciences

Prof. Dr. Canan Özgen

Director

I certify that this thesis satisfies all the requirements as a thesis for

the Degree of Master of Science.

Prof. Dr. Filiz B. Dilek

Head of Department

This is to certify that we have read this thesis and that in our opinion

it is fully adequate, in scope and quality, as a thesis for the Degree

of Master of Science.

Assoc. Prof. Dr. F. Dilek Sanin

Supervisor Examining Committee Members

Prof. Dr. Gülerman Sürücü (METU, ENVE) Prof. Dr. Ülkü Yetiş (METU, ENVE) Assoc. Prof. Dr. F. Dilek Sanin (METU, ENVE) Assist. Prof. Dr. Ayşegül Latifoğlu (HU, ENVE) Assist. Prof. Dr. İpek İmamoğlu (METU, ENVE)

ii

I hereby declare that all information in this document has been

obtained and presented in accordance with academic rules and

conduct, I have fully cited and referenced all material and results that

are not original to this work.

Name, Last Name:

Signature:

iii

ABSTRACT

USE OF CALCIUM ALGINATE AS A COAGULANT DURING WATER TREATMENT

ÇORUH, Hale Aylin M.Sc., Environmental Engineering Department

Supervisor: Assoc. Prof. Dr. F. Dilek Sanin

September 2005, 185 Pages

Coagulation and flocculation processes are important parts of water

and wastewater treatment. Coagulation or destabilization of colloidal

suspensions results in aggregation of colloidal particles by physical

and chemical processes. Flocculation results in the formation of

larger and settleable structures by bridging.

Alginate, a polysaccharide obtained from marine brown algae,

produces a gel structure when mixed with calcium ions, which is

expected to be a potential coagulant in water treatment. This study

aims to determine the use of calcium alginate as a potential

coagulant during water treatment and determine its capabilities and

deficiencies in coagulation processes.

The study was conducted on turbid water samples prepared in the

laboratory and those taken from the inlet of Ankara İvedik Water

Treatment Plant (IWTP) by running typical jar tests. The main

experimental variables were initial alginate and calcium doses, initial

turbidity of water samples and the order with which the two

iv

chemicals are dosed. The main criteria investigated to check the

success of the system was the final turbidity values and the turbidity

removal capacity of calcium- alginate.

Experiments were conducted on three different laboratory –

prepared turbid water samples and on the raw water taken from the

inlet point of Ankara İvedik Drinking Water Treatment Plant (IWTP).

These were prepared as high (150 NTU) medium (80 NTU) and low

(10 NTU) turbidity samples. The calcium concentrations tested

varied between 30 and 200 mg/L and alginate concentrations tested

varied between 0.04 to 40 mg/L.

Depending on the initial turbidity and initial calcium concentration of

water sample the results depict that calcium alginate could be used

as an effective coagulant for high (150 NTU) and medium (80 NTU)

turbidity water sample especially at the calcium doses of 120 and

160 mg/L for low alginate concentration doses like 0.4 mg/L. The

final turbidity met both the requirements of Drinking Water Standards

applied in Turkey and Europe. Generally, the higher the initial

turbidity was, the higher the turbidity removal efficiency achieved,

even with very low alginic acid concentration. As the initial turbidity

decreased, initial concentration of calcium required for the effective

coagulation processes decreased. However, for low (10 NTU)

turbidity water samples the system did not work properlyHowever,

for low turbidity water samples, the turbidity removal efficiency

decreased, and it was difficult to meet the limits.

Keywords: Alginate, Calcium, Calcium-Alginate gel, Coagulation,

Flocculation, Turbidity, Water Treatment.

v

ÖZ

KALSİYUM ALGİNATIN SU ARITIMINDA KOAGÜLAN MADDE OLARAK KULLANIMI

ÇORUH, Hale Aylin Yüksek Lisans, Çevre Mühendisliği Bölümü,

Tez Danışmanı: Doç. Dr. F. Dilek Sanin

Eylül 2005, 185 Sayfa

Pıhtılaştırma ve yumaklaştırma su ve atıksu arıtımında rol oynayan

önemli proseslerdir. Pıhtılaştırmada ilk aşama kolloidal maddelerin

kararlı hallerinin değiştirilmesi ve kolloidal parçacıkların fiziksel ve

kimyasal prosesler sonucu bir araya gelip kümeler oluşturmasıdır.

Yumaklaşma, daha büyük yapıdaki çökelebilir maddelerin

oluşmasıyla sonuçlanır.

Kahverengi alglerden üretilen bir polisakkarit olan alginat kalsiyum

iyonları ile karıştırıldığında, su arıtımı için potansiyel bir pıhtılaştırıcı

olarak değerlendirilebilen bir jel yapı oluşturur. Bu çalışmada

kalsiyum alginatın su arıtımı için potansiyel bir koagülan madde

olarak uygulanabilirliğinin ve koagülasyon prosesinde yeterli ve

yetersiz olduğu noktaların belirlenmesi amaçlanmıştır.

Çalışma, laboratuar ortamında hazırlanmış olan ve ASKİ İvedik İçme

Suyu Arıtma Tesisi giriş ünitesinden alınan bulanık su örnekleri

kullanılarak tipik jar test analizleri ile yapılmıştır. Deneysel

vi

çalışmanın ana değişkenleri başlangıç alginat ve kalsiyum dozları,

suyun başlangıç bulanıklığı ve bu iki kimyasalın arıtım sırasındaki

dozlama sırasıdır. Ölçülen parametreler ve başarının ölçütü olarak

kabul edilen temel kriter ise arıtım sonundaki bulanıklık ve kalsiyum

alginat sisteminin bulanıklık giderim kapasitesi olmuştur

Deneysel çalışma laboratuarda hazırlanan 3 farklı bulanıklığa sahip

su ve Ankara İvedik İçme suyu Arıtma Tesisi giriş ünitesinden alınan

ham su örneklerinde yapılmıştır. Bunlar yüksek (150 NTU) orta (80

NTU) ve düşük (10 NTU) seviyesinde bulanıklığa sahip

numunelerdir. Denenen kalsiyum konsantrasyonları 30 ile 200 mg/L

arasında, alginat konsantrasyonları ise 0.04 ile 40 mg/L arasında

değiştirilmiştir.

Sonuçlar, kalsiyum alginatın, su numunesinin başlangıç bulanıklığı

ve kalsiyum konsantrasyonuna bağlı olarak yüksek (150 NTU) ve

orta (80 NTU) bulanıklıklarındaki sular için özellikle 120 ve 160 mg/L

kalsiyum ve 0.4 mg/L gibi düşük alginat konsantrasyonları

kullanılarak etkili bir koagülan madde olabileceğini göstermektedir.

Son bulanıklık ve kalsiyum konsantrasyon değerleri, Türkiye ve

Avrupa’da uygulanmakta olan İçme Suyu Standartları’na uygundur.

Başlangıç bulanıklığı arttıkça çok küçük alginat konsantrasyonları

için bile daha fazla bulanıklık giderimi sağlanmıştır. Başlangıç

bulanıklığı azaldıkça, etkili koagülasyon için gereken kalsiyum

başlangıç konsantrasyonu azalmaktadır. Ancak, çok düşük

bulanıklıktaki su numuneleri için bulanıklık giderim veriminin azaldığı

ve standartlarda istenen değerlerin sağlanamadığı saptanmıştır.

Anahtar Kelimeler: Alginat, Bulanıklık, Kalsiyum, Kalsiyum-Alginat

Jeli, Su Arıtımı, Pıhtılaştırma, Yumaklaştırma.

vii

ACKNOWLEDGMENTS

I would like to express my sincere gratitude to Assoc.Prof. Dr.

F.Dilek Sanin for her guidance, enthusiasm and insight in

supervising the thesis.

I would also like to thank to Prof. Dr. Gülermen Sürücü, Prof Dr. Ülkü

Yetiş, Assist.. Prof. Dr. Ayşegül Latifoğlu and Assist. Prof. Dr. İpek

İmamoğlu for their suggestions and contributions Also, I am very

greatful to the following people for their assistance in the production

of this thesis and their contributions to the experimental works:

The various in-kind contributions of Assoc. Prof. Dr. Selim Sanin,

Prof. Dr. Ali Cemal Saydam, all the staffs working at the

Environmental Engineering Department of Hacettepe University.

Without this support this project could not be completed.

The valuable contributions and support made by our laboratory

technicians Kemal Demirtaş, Ramazan Demir and Aynur Yıldırım,

our secretaries Gülşen Erdem and our staffs Yakup Pınarbaşı and

Döndü İvedik.

The help provided by the administrative and technical support staff

from the Department of Geological Engineering at Middle East

Technical University and Ankara İvedik Drinking Water Treatment

Plant.

viii

And also I would like to express my thanks and appreciation to Prof.

Dr. Ümit Atalay, his assistance and my dear friend Tuğcan Tuzcu for

their valuable contributions to my study.

I am realy greatful to Aysun Vatansever, Fadime Kara, Firdevs

Yenilmez , Devrim Kaya, Avni Mete Yüksel, Nimet Uzal, Erkan

Şahinkaya and Recep Tuğrul Özdemir for their supports and aids

whenever I was in trouble.

Sometimes it is diffucult to say what you feel. I don’t know how to

thank, how to appreciate to my friends for their unforgiven

contributions, their nice fellowships, for all the things that they share

with me. My dear friends: Tuğba Altınışık, Esra Meriç, Bengü

Mındıkoğlu, Özge Yılmaz, İpek Turtin, Gülçin Özsoy, Hande

Yükseler, Can Akar and Cihan Ataş. It is glad for your beings. I really

thanks to you all.

I owe special thanks to the families of Devrimci, Künyeli, Dinç,

Erdem and Güneştan for their trust, interest and encouragement to

complete this work. I also would like to state special thanks to Soner

Künyeli for his equipmental and logistical support whenever I need.

I would like to appreciate my dear brother and his sweety wife for

their contribution, encouragement and attention to my life.

I would like to express my deepest gratitude and appreciation to my

parents for their endless love, power that they sent,

encouragements, contributions, supports and patience. I wish it is

possible to share out the diploma that “we achieved”.

ix

I am heavily indebted to my love, Mehmet Ş. Devrimci. This thesis

could not have been written without you. I would like to express my

thanks for your contributions, abetment, power, especially for your

patience and endless love. Everything could have been more and

more diffucult without you. I appreciate to you and your being, my

dear husband.

x

To my parents

And

To my deary love

xi

TABLE OF CONTENTS

ABSTRACT.............................................................III

ÖZ............................................................................ V

ACKNOWLEDGMENTS ....................................... VII

TABLE OF CONTENTS......................................... XI

LIST OF FIGURES................................................XV

LIST OF TABLES ................................................XIX

NOMENCLATURE ...............................................XXI

INTRODUCTION ......................................................1

1.1 GENERAL ................................................................................. 1 1.2 OBJECTIVE AND SCOPE OF THE STUDY .............................. 9

THEORETICAL BACKGROUND...........................10

2.1 TURBIDITY.............................................................................. 11 2.1.1 TURBIDITY CHANGES IN WATER SOURCES ............... 13 2.1.2. EFFECTS OF TURBIDITY ON HUMAN HEALTH AND AQUATIC LIFE .......................................................................... 14 2.1.3 IMPACT OF TURBIDITY IN WATER TREATMENT ......... 16 2.1.4 TURBIDITY LIMITS FOR WATER TREATMENT ............. 17

2.2 COAGULATION AND FLOCCULATION PROCESSES IN

WATER TREATMENT................................................................... 18 2.2.1. STABILITY OF COLLOIDS.............................................. 19 2.2.2 COAGULATION MECHANISMS ...................................... 28

2.2.2.1 DOUBLE LAYER COMPRESSION .....................................................................28 2.2.2.2 ADSORPTION AND CHARGE NEUTRALIZATION.........................................30 2.2.2.3 ENMESHMENT IN A PRECIPITATE..................................................................31 2.2.2.4 INTERPARTICULAR BRIDGING .......................................................................31

2.2.3 COMMONLY USED COAGULANTS IN WATER TREATMENT............................................................................. 34

xii

2.3 NATURAL POLYMERS - ALGINATE....................................... 42 2.3.1 PHYSICO-CHEMICAL PROPERTIES OF ALGINATE ..... 45 2.3.2 INDUSTRIAL APPLICATIONS AND ECONOMIC ASPECTS OF ALGINATE ......................................................... 51 2.3.3 COAGULATION MECHANISM OF ALGINATE ................ 54

MATERIALS & METHODS ....................................57

3.1 MATERIALS ....................................................................... 57 3.1.1 CLAY SUSPENSION................................................... 57 3.1.2 RAW WATER .............................................................. 59 3.1.1 COAGULANTS AND CHEMICALS ............................. 60

3.1.1.1 ALGINATE...................................................................................................60 3.1.1.2 CALCIUM CHLORIDE SOLUTION...........................................................61 3.1.1.3 CALCIUM STANDARD SOLUTION .........................................................61 3.1.1.4 SODIUM CHLORIDE ..................................................................................61 3.1.1.5 MAGNESIUM CHLORIDE .........................................................................61

3.2 METHODS.......................................................................... 62

3.2.1 COAGULATION EXPERIMENT .................................. 62 3.2.2 INVESTIGATED VARIABLES ..................................... 63

3.2.2.1 INITIAL TURBIDITY ..................................................................................63 3.2.2.2 CALCIUM DOSE .........................................................................................64 3.2.2.3 ALGINATE DOSE .......................................................................................64 3.2.2.4 ORDER OF CHEMICAL ADDITION .........................................................64 3.2.2.5 ADDITION OF SODIUM AND MAGNESIUM..........................................65 3.2.2.6 SETTLING TIME .........................................................................................65 3.2.2.7 pH..................................................................................................................65

3.3 ANALYTICAL TECHNIQUES ............................................. 66

3.3.1 TURBIDITY MEASUREMENT..................................... 66 3.3.2 CALCIUM MEASUREMENTS ..................................... 66 3.3.3 TOTAL ORGANIC CARBON (TOC) ANALYSIS............... 67

3.4 CLEANING OF GLASSWARE................................................. 67 3.5 EXPERIMENTAL FLOW CHART OF THE STUDY .................. 67

RESULTS & DISCUSSIONS .................................70

4.1 DETERMINATION OF THE INTERACTION BETWEEN

CALCIUM AND ALGINATE ........................................................... 70

4.2 ASSESSMENT OF THE EFFECT OF THE INTERACTION

BETWEEN CALCIUM AND ALGINATE ON PH ............................. 73

4.3 EVALUATION OF ALGINATE AS A POTENTIAL COAGULANT

FOR HIGH TURBIDITY (150 NTU) WATERS................................ 74

xiii

4.4 ASSESSMENT OF THE EFFECT OF THE DOSING ORDER

ON RESIDUAL TURBIDITY FOR DIFFERENT CALCIUM

CONCENTRATIONS BY USING THE 150 NTU TURBID WATER

SAMPLE........................................................................................ 82

4.5 EVALUATION OF TOTAL ORGANIC CARBON (TOC) VALUES DURING COAGULATION WITH CALCIUM ALGINATE . 89

4.5 EVALUATION OF ALGINATE AS A POTENTIAL COAGULANT FOR

MEDIUM TURBIDITY (80 NTU) WATER SAMPLES ................................ 91

4.6 ASSESSMENT OF THE EFFECT OF DOSING ORDER

BETWEEN CALCIUM AND ALGINATE ON THE TURBIDITY

REMOVAL FOR 80 NTU TURBIDITY SAMPLES .......................... 96

4.7 DETERMINATION OF THE EFFECT OF SODIUM ION AS

COAGULANT AID TO CALCIUM ALGINATE FOR INITIAL

TURBIDITY OF 80 NTU............................................................... 101

4.8 DETERMINATION OF THE EFFECT OF MAGNESIUM ION AS

COAGULANT AID TO CALCIUM ALGINATE FOR INITIAL

TURBIDITY OF 80 NTU............................................................... 104

4.9 DETERMINATION OF THE EFFECT OF SETTLING TIME ON

RESIDUAL TURBIDITY (80 NTU) ............................................... 105

4.10 DETERMINATION OF THE EFFECT OF SETTLING TIME

AND THE ORDER CHANGE ON RESIDUAL TURBIDITY (80 NTU)107

4.11 EVALUATION OF ALGINATE AS A POTENTIAL

COAGULANT FOR LOW TURBIDITY (10 NTU) WATER

SAMPLES ................................................................................... 108

4.12 EVALUATION OF THE EFFECT OF MAGNESSIUM IONS AS

COAGULANT AID ON THE PERFORMANCE OF CALCIUM

ALGINATE FOR LOW TURBIDITY WATERS.............................. 112

4.13 EVALUATION OF THE EFFECT OF TURBIDITY ON THE

PERFORMANCE OF CALCIUM ALGINATE ............................... 114

4.13 EVALUATION OF ALGINATE AS A POTENTIAL

COAGULANT FOR WATER SAMPLES TAKEN FROM IVEDIK

TREATMENT PLANT, ANKARA.................................................. 116

4.14 WORKING MECHANISM OF CALCIUM ALGINATE AS A

COAGULANT FOR WATER TREATMENT ................................. 122

xiv

4.15 COMPARISON OF POLYELECTROLYTE USED IN IVEDIK

TREATMENT PLANT WITH ALGINATE...................................... 124

4.16 COST ANALYSIS ............................................................... 127

CONCLUSION .....................................................130

REFERENCES .....................................................133

APPENDICES ......................................................132

xv

LIST OF FIGURES

Figure 2. 1 Electrical Double Layer around a sable particle......21

Figure 2. 2 Possible Polymer Particle Interaction (Adapted from

O’Melia et al., 1972).......................................................................33

Figure 2. 3 Cell wall structure in the brown algae. (After

Schiewer and Volesky , 1993). .....................................................45

Figure 2. 4 The Structural Compositions of Alginate (a) The

Monomer Structure of Alginate (b)The Sequence and Bond

Formations of Block Structures as an Example (c) The

Sequence Of The Block Types.....................................................47

Figure 2. 5 Alginate gel formation and egg-box model in the

presence of calcium (not to scale). .............................................49

Figure 2. 6 The egg-box model of alginate with high and low

ca+2 concentrations. .....................................................................51

Figure 3. 1 Zeta Potential Distribution of Clay Suspension

before Treatment...........................................................................58

Figure 3. 2 Particle Size Distribution of Suspended Particles

before Treatment...........................................................................59

Figure 3. 3 Flow Chart for Experimental Works of The Study..69

Figure 4. 1 Stages of Experiments (a) Flocs formation during

slow mixing stage, (b) Flocs start to settle at the end of slow

mixing, (c) Settling achieved at the end of 30 minute settling

time. ...............................................................................................71

Figure 4. 2 Assessment of the effect of change in calcium

concentration on final turbidity (initial turbidity 150 NTU) plotted

for samples giving final turbidity as less than 5 NTU................76

xvi

Figure 4. 3 Turbidity Removal Efficiency for Different Calcium

Dosages (Initial Turbidity 150 NTU).............................................80

Figure 4.4 Calcium Ion Removal Efficiency for Different Calcium

........................................................................................................81

Figure 4. 5 Assessment of the Effect of Change in Initial

Calcium Concentration on Final Turbidity) When Alginate was

Dosed First (plotted only for the data points lower than 5 NTU

for clarity). .....................................................................................83

Figure 4. 6 Turbidity Removal Efficiency for Different Calcium

Dosages (Initial Turbidity 150 NTU) When Alginate Was Dosed

First. ...............................................................................................87

Figure 4. 7 Change in Calcium Removals With Respect to

Applied Alginate Doses at Various Initial Calcium

Concentrations (when alginate was dosed first)........................88

Figure 4. 8 Assessment of the Effect of the Change in Calcium

Concentration on Final Turbidity (Initial Turbidity: 80 NTU) .....93

Figure 4. 9 Turbidity Removal Efficiency for Different Calcium

Dosages (Initial Turbidity: 80 NTU) .............................................94

Figure 4. 10 Calcium Removal Efficiency for Different Calcium

Dosages (Initial Turbidity: 80 NTU) .............................................95

Figure 4. 11 Assessment of the Effect of the Change in Dosing

Order on Final Turbidity When Alginate Dosed Initially (Initial

Turbidity: 80 NTU).........................................................................97

Figure 4. 12 Turbidity Removal Efficiency for Different Calcium

Dosages (Initial Turbidity: 80 NTU) .............................................98

Figure 4.13 Calcium Removal Efficiency for Different Calcium

Dosages When Alginate was Dosed First (Initial Turbidity: (80

NTU) ...............................................................................................99

Figure 4. 14 Assessment of the Effect of Calcium Concentration

Change on Residual Turbidity for the Fixed Turbidity (80 NTU)

and Fixed Sodium Concentration (4 meq/L). ............................102

xvii

Figure 4. 15 Assessment of Sodium Ions Effect on Residual

Turbidity as Coagulant Aid to Calcium Alginate (for 80 mg/L of

Calcium and 80 NTU of Initial Turbidity) ...................................103

Figure 4.16 Assessment of the Effect of Magnesium Ion as

Coagulant Aid for Fixed Calcium Concentration and Fixed Initial

Turbidity ......................................................................................104

Figure 4. 17 Effect of Settling Time on Final Turbidity ............106

Figure 4. 18 Assessment of The Effect of Settling Time and

Dosing Order Change on Residual Turbidity ...........................107

Figure 4. 19 Final Turbidity as a function of alginate dose for 10

NTU turbidity samples................................................................110

Figure 4. 20 The Effect of the Change in Calcium

Concentrations on Residual Turbidity for Low Turbidity Water

(10 NTU) .......................................................................................111

Figure 4. 21 Assessment of Magnesium Ions as Coagulant Aid

to Calcium Alginate ....................................................................113

Figure 4. 22 Effect of the Performance of Calcium Alginate ...115

Figure 4. 23 Evaluation of calcium alginate as potential

coagulant for the water samples taken from IWTP. .................118

Figure 4. 24 Evaluation of calcium alginate as potential

coagulant for the water samples taken from IWTP. .................119

Figure 4. 25 Evaluation of calcium alginate as potential

coagulant for IWTP with respect to the turbidity removal

efficiency at 120 mg/L.................................................................120

Figure 4. 26 Evaluation of calcium alginate as potential

coagulant for the water sample from IWTP with respect to the

calcium removal efficiency. .......................................................121

Figure 4. 27 Assessment of Polyelectrolyte and Calcium ion

interactions with respect to residual turbidity .........................125

xviii

Figure 4. 28 Comparison of Polyelectrolyte and Alginate within

the case of 80 mg/L of Calcium Dosed and 80 NTU of Initial

Turbidity ......................................................................................126

Figure 4. 29 Comparison of Polyelectrolyte and Alginate within

the case of 80 mg/L of Calcium Dosed and 80 NTU of Initial

Turbidity ......................................................................................127

xix

LIST OF TABLES

Table 1. 1 Different Sources of Water (Adapted from EPA

Guidance Manual Turbidity Provisions, 1999) ...................3 Table 2. 1 A summary of the industrial and biotechnological

uses of alginate..................................................54 Table 3. 1 Composition of Alginate in Terms of Its Monomers

Used in the Study................................................60

Table 4. 1 The Results from the Preliminary Analysis ........72 Table 4. 2 Examination of the system pH before and after

coagulation ......................................................73 Table 4. 3 Result of the Study to Determine the Effect of

Calcium Ion on the Turbidity Removal When Calcium was

Dosed Only.......................................................74 Table 4. 4 The Optimum Alginate Concentrations for Each of the

Calcium Concentrations Dosed, Having 150 NTU of Initial

Turbidity When Calcium Dosed First...........................79 Table 4. 5 The Optimum Alginate Concentrations for Each of the

Calcium Concentrations Dosed When Initially Alginate Was

Dosed, Having 150 NTU of Initial Turbidity ....................86 Table 4. 6 TOC Measurement Results of Water Samples Treated

With Different Calcium Doses Considering Their Optimum

Alginate Concentration for 150 NTU of Initial Turbidity.......90

xx

Table 4. 7 Result of the Study to Determine the Effect of

Calcium Ion on the Turbidity Removal When Calcium was

Dosed Only.......................................................91 Table 4. 8 The Optimum Alginate Concentrations for Each of the

Calcium Concentrations Dosed When Initially Calcium Was

Dosed, Having 80 NTU of Initial Turbidity......................96 Table 4. 9 Minimum Alginate Concentrations for Each of the

Calcium Concentrations Dosed, Having 80 NTU of Initial

Turbidity When Alginate Dosed First.........................100 Table 4. 10 Result of the Study to Determine the Effect of

Calcium Ion on the Turbidity Removal When Calcium was

Dosed Only.....................................................109 Table 4. 11 Result of the Study to Determine the Effect of

Calcium Ion on the Turbidity Removal When Calcium was

Dosed Only.....................................................117

Table 4. 12 Unit Prices of the Chemicals.....................128

Table 4. 13 Total Chemical Costs.............................128

xxi

NOMENCLATURE

• Total Organic Carbon (TOC)

• Nephelometric Turbidity Units (NTU)

• Formazin Turbidity Units (FTU)

• Jackson Turbidity Unit (JTU)

• Natural Organic Matter (NOM)

• DLVO Theory : Derjaguin, Landau, Verwery and Overbeek

Theory.

1

CHAPTER 1

INTRODUCTION

1.1 GENERAL

The quality of water for the purpose of human consumption has

been of interest since its effects on health was first discovered.

Considering the increase in demand and also the decrease in

resources, water as essential fluid of life is a scare commodity.

Water supply and treatment are critical needs of society. It was

recognized earlier that water quality involves both aesthetic and

health concerns depending on the purpose of consumption and also

the contaminants present. Therefore, the purpose of water treatment

is to produce a safe and aesthetically pleasing water. This requires

that the water be free of harmful chemicals and microbes, as well as

have an acceptable taste and odor (Ray B. T., 1993).

The potential for health problems associated with contaminated

drinking water is great because many diseases are transmitted by

water that is contaminated with bacteria or viruses (Mihelcic J. R. et

al., 2001). Thus, throughout the world, the water quality and control

standards are graded depending on for what purpose the water is

going to be consumed. For example, in US primary drinking water

standards relate directly to health, and secondary standards relate

more to the appearance and non- consumptive uses of water.

Primary standards are mandatory whereas secondary standards are

2

suggested as upper limits for non-health related parameters (Ray, B.

T., 1993). Europe, USA and Turkey are in agreement with respect to

the required turbidity limit values which are very important for both

aesthetics as well as health purposes depending on what purpose

the water is going to be consumed (See Appendix A). Depending on

the source of water, these countries have the water turbidity

limitation values as

• Less than 1 Nephelometric Turbidity Unit (NTU) when the

surface water is treated for drinking water purposes.

• Less than 5 Nephelometric Turbidity Unit (NTU) for human

consumptive purposes.

There are many sources of water, but limited amount can be used

safely for drinking purposes. Table 1.1 lists those sources and also

provides general comments regarding each of these sources (EPA

Guidance Manual Turbidity Provisions, 1999).

Most individuals and industries obtain their water from surface

waters (streams, rivers, lakes, reservoirs) and groundwater.

However, the amount of water that man has been able to use is

limited; and throughout the past few centuries we have not been

able to add significantly to the amount of available fresh water. Since

the world has experienced an increase in population and

technological growth, the available water is insufficient for future

needs and is becoming increasingly polluted. Moreover, the

distribution of the water sources throughout the world is not even.

Therefore, some parts of the world (e.g., Middle East) construct

desalination plants by the help of which the use of seawater as a

source of drinking water is possible (EPA Guidance Manual Turbidity

Provisions, 1999).

3

Table 1. 1 Different Sources of Water (Adapted from EPA Guidance Manual Turbidity Provisions, 1999)

Source of Water Comments

Surface water High flows, easy to contaminate, relatively high suspended solids (SS), turbidity, and pathogens. In some parts of the world, rivers and streams dry up during the dry season.

Groundwater Usable as source for drinking water, low flows but has natural filtering capacity that removes suspended solids (SS) and turbidity. May be high in dissolved solids (TDS) including Fe, Mn, Ca, Mg (hardness). Difficult to clean up after contaminated.

Ocean Energy intensive so costly compared to other sources. Desalination can occur by distillation, reverse osmosis, electrodialysis, freezing, and ion exchange. Of these, multistage distillation and reverse osmosis are two technologies most commonly used.

Reclaimed water Technically feasible. More likely to be unacceptable to the public

Generally, the surface waters as water supply are preferable due to

some reasons like its availability, attainability, treatability, etc.

Normally surface water sources contain substances that affect the

appearance of the water, e.g. silt or algae so that the need for

treatment is obvious. Many underground sources however, are free

from visual contamination and it may therefore appear not to be

necessary to treat the water. However, even these sources that do

not appear to be contaminated may contain harmful substances

leached from the soil and rock formations through which the water

moves during infiltration. The water may also be contaminated by

infiltration of polluted water into the groundwater. The treatment

4

needs could therefore only be determined from an analysis of the

water (Water Research Commission, 2002). The raw water quality

determines the processes that must be considered for inclusion in

the treatment process. After it has been decided that water from a

particular source has to be treated, the main aspects that must be

taken into account are:

• The quality of the water source (raw water quality) and its

variability;

• The quality of the treated water to be produced;

• The volume of water to be treated (capacity);

• The cost limitations (the water cost/price that is considered to

be acceptable to the consumers);

• The level of sophistication that is acceptable taking into

account plant locality and level of expertise available to

control and operate the plan;

• The support services available to assist with plant

optimization, troubleshooting and maintenance and repair

problems (Water Research Commission, 2002).

Suspended matters in water and wastewater result in turbidity. Not

only due to the aesthetical reasons but also its potential health risks,

turbidity is an important parameter stated in drinking water quality

criteria. In order to meet the criteria, the removal of colloidal particles

causing the turbidity is required. Moreover, raw water containing

colloidal particles should be treated via water treatment processes

for several reasons such as:

• Particles are removed in order to make the water aesthetically

pleasing to the consumers.

5

• Particles are also removed due to the fact that pathogenic

microorganisms often attach to the particles and when the

particles are removed, so are the pathogens.

• Particles in raw water can influence the disinfection process in

a negative way. When shielded by particles the disinfectant

may not be as effective in inactivating pathogens. Meaning

that particles may decrease the efficiency of disinfection, as a

result of which a higher degree of treatment might be required

for effective water treatment. Therefore, by the removal of the

particles, the efficiency of disinfection can be as effective as

possible (HDR Engineering, Inc., 2001).

There are many natural processes by which turbidity is created and

conveyed to a raw water intake for a water treatment plant. A typical

water treatment plant that uses surface water as a source of water

requires the removal of primarily particulate matter and pathogens.

Because most pathogens associate themselves with particulate

matter, removing large and small sized particles also assists in

making the water pathogen free (Water Research Commission,

2002).

The nature and characteristics of suspended and colloidal material in

water are important in determining the type of treatment process

required for removal. The suspended material can be inorganic in

nature, e.g. sand or clay particles or organic in nature such as algae

or humic material from decaying plant material. The size of the

particles is another very important characteristic because size

determines to a large extent the type of treatment process that can

be used to treat the water. The nature of suspended material in

water can vary from relatively coarse particles that can be removed

simply by allowing the particles to settle and decanting the clear

6

water. At the other end of the spectrum are very fine particles, called

colloidal particles which do not settle at all even if left for a long

period of time and which have to be treated chemically to remove

them from the water. Colloidal particles are very small (smaller than

0.1 micron), and since they are electrically charged they have very

specific characteristics. The most important characteristic is that they

form a stable colloidal suspension that do not settle readily, but

remain in suspension (even for periods of days or weeks). In order

for such particles to settle, they must be chemically destabilized or

coagulated to neutralize the charge on them and to form larger flocs

that can settle, thereby facilitating their removal from water (Water

Research Commission, 2002).

The conventional treatment methods for removal of suspended and

colloidal material from water include chemical coagulation of small

colloidal particles, flocculation of the small particles to form larger

flocs, followed by sedimentation and sand filtration. When the water

contains a large amount of suspended material, larger suspended

particles such as sand particles can be removed by means of

settling without coagulation and flocculation. Other methods that can

be used include slow sand filtration, flotation, micro-filtration and

ultra-filtration.

The selection of the best combination of processes to treat particular

water depends on a number of factors. These factors include:

• The amount of suspended solids;

• The turbidity of the water;

• The nature of the suspended material;

• The chemical properties of the water (alkalinity and pH);

7

• The volume of water to be treated, and the availability of

facilities, trained operators and supervisors (Water Research

Commission, 2002).

Coagulation and flocculation processes are important parts of water

and wastewater treatment regarding to the removal of suspended

particles, and are used together to remove particles that can impart

color to a water source, create turbidity, and retain bacterial and viral

organisms. Also, some of these small particles may be pathogenic

organisms themselves. The process of coagulation and flocculation

is used to treat small particles in the size range of 0.001 to 1.0

micrometer. These colloidal particles typically have large surface

areas and are usually negatively charged (AWWA, 1990).

Alum is the most common coagulant and it has been used in water

treatment. Alum and ferric chloride are specific chemical compounds

used for coagulation. They can be used as sweep floc coagulants or

used to reduce the zeta potential of the particles found in raw water.

There are many types of polymers that are used in water treatment

today. Polymers coagulate in a method called bridging in which

particles bond to their long chains and are then removed in filtering

(Huang and Chen, 1996).

In order to obtain an effective coagulation and flocculation, inorganic

flocculants are used in large quantities, leave large amount of

sludge, which needs further treatment procedures, which

complicates handling and disposal procedures. This brings about the

increase in the treatment costs. To minimize these drawbacks,

synthetic polymers have gained popularity as water treatment

chemicals. However, these materials also have limitations:

8

• They exhibit a significant degree of selectivity to certain types

of colloids.

• They form large and strong floc, but usually do not produce a

clear supernatant. Because, they are generally incapable of

enmeshing all of the colloidal particles in raw water.

• Their unit costs are much higher than alum or ferric chloride

• Most of them are not readily biodegradable. (Kawamura,

1991)

Natural polyelectrolytes, which can be extracted from certain kinds of

plant and animal life, are workable alternative to synthetic polymers.

These natural organic polymers have advantages such as

• They are safe for human health,

• They are biodegradable, so is their sludge produced and

• They have wider effective dosage range of flocculation for

various colloid suspensions (Kawamura, 1991).

In this study, the usability of an organic polymer, namely alginate – a

polysaccharide obtained from marine brown algae-, is investigated

as a coagulant. In the limited documents in literature it is stated that

some biopolysaccharides interact with the cations in the solution and

form gelatinous structure (Kawamura, 1991). This gelatinous

structure is considered as potential coagulant matter, by which the

effective flocculation and so the efficient turbidity removal could be

achieved. It is also pointed out that the removal of colloidal particles

via organic coagulants depends on the nature of the polymeric

structure, the degree of branching, the molecular weight of polymer,

the bond formation and the electrostatic interactions among the

surface of colloidal suspensions and polymers (Lee, 1998).

9

Alginate when mixed with calcium ions is able to produce a gel

structure, which finds use as thickening agent in the food industry, in

drug-release systems during pharmaceutical applications, as

biomaterials in wound healing, and cell culture applications. So, all

these reports in literature constitute a motivation and the driving

force for this study, and hence the applicability of calcium alginate as

a coagulant during water treatment is examined.

1.2 OBJECTIVE AND SCOPE OF THE STUDY

The aim of the study is to determine the use of calcium alginate as a

potential coagulant for water treatment and to determine its

capabilities and deficiencies in coagulation and flocculation

processes.

The study was conducted on turbid water samples prepared in the

laboratory and also on the water samples coming from Kurtboğazı

and Çamlıdere reservoirs feeding the İvedik Drinking Water

Treatment Plant (IWTP) in Ankara by running typical jar tests.

Sodium alginate and calcium chloride were used as coagulant in the

coagulation experiments. Initial turbidity, initial calcium and alginate

concentrations were chosen as independent variables. Coagulation

conditions were tried to be optimized for the maximum removal of

turbidity from the system.

Along with the processed water turbidity, the treated water was

examined for residual calcium concentration and total organic

carbon content and evaluated against both Drinking Water

Standards for Turkey and European Union.

10

CHAPTER 2

THEORETICAL BACKGROUND

WATER QUALITY PARAMETERS

Water is most widely used chemical on the earth. It is necessary for

all life. To examine water pollution in more specific, practical terms,

we must precesely define the characteristic of water in question. To

do so, the most widely used parameters are cited below.

Temperature: Surface waters are subject to large variations in

temperature. For example, some stream waters may vary from 1oC

in the winter to close to 28oC in the summer. This change in

temperature can have a large impact on the types of aquatic life and

reaction rates.

Dissolved Oxygen: The presence of dissolved oxygen is important

for the aquatic life and aesthetic quality of waters. The amount of

oxygen is perhaps the most widely used indicator of water quality.

Many factors may impact the level of oxygen in a surface water

body. For example, it is strongly affected by the presence of certain

bacteria that use oxygen as they biodegrade organic matter. The

saturation level is inversely proportional to the temperature.

pH : is –log [H+] and represents a measure of the concentration of

protons. Surface waters have a pH that can range from 5 to 8.

11

Total Suspended Solids: represents the concentration of suspended

solids. All contaminants of water, other than gases, contribute to the

solids load. Untreated wastewater has a solids concentration

between 200 and 700 mg/L, while surface waters usually have a

concentration less than 20 mg/L.

The suspended materials cause claudy appearence of water, which

is called turbidity. The information about turbidity is going to given in

detail in the section of 2.1.

Chloride: Is naturally present in waters (<50 mg/L) from leaching of

rocks, or as a result of road salting.

Nitrate: Nitrogen is the element required in greatest quantities next

to carbon and oxygen and typically has a concentration less than 5

mg/L in surface waters. Nitrate (NO3-) which is a nutrient, plays a

role in the nitrogen cycle within waters.

Sulfate: Is also a nutrient which is taken up by plants and bacteria for

the production of cells.

Calcium and Magnesium: are both naturally present in surface

waters. They cause hardness of waters and hard waters are

undesirable due to possibilities of precipitation and scaling and

excessive soap and detergent consumption.

2.1 TURBIDITY

Turbidity measures the scattering effect that suspended solids have

on light; the higher the intensity of scattered light, the higher the

12

turbidity. Primary contributors to turbidity include clay, silt, finely

divided organic and inorganic matter, soluble colored organic

compounds, plankton, and microscopic organisms (USEPA

Geological Survey, 1998).

Determination of turbidity is a common component of water-quality

assessments as follows:

• In surface water, the clarity of a natural body of water is used

routinely as an indicator of the condition and productivity of

the aqueous system.

• In ground water, turbidity commonly is measured during well

development and well purging to indicate the extent to which

particulates occurring as a result of well installation and

sampling activities have been removed (USEPA Geological

Survey, 1998).

The characteristics of turbidity in surface water supplies are a

function of many factors. Watershed features, such as geology,

human development (i.e., agricultural uses or urban development),

topography, vegetation, and precipitation events can all greatly

influence raw water turbidity. In addition, reservoirs and ponds can

often dampen the impact of increased turbidity events by acting as

points in a stream or river where particles can settle before being

drawn into the intake of a treatment plant. Wells and infiltration

galleries along streams or rivers can also reduce the impact of

turbidity increases in streams by their use of a natural aquifer as a

filter (EPA Guidance Manual Turbidity Provisions, 1999).

Turbidity is measured in Nephelometric Turbidity Units (NTU) or

Formazin Turbidity Units (FTU), depending on the method and

13

equipment used. Turbidity measured in NTU uses Nephelometric

methods that depends on passing specific light of a specific

wavelength through the sample. FTU is considered comparable in

value to NTU and is the unit of measurement when using

absorptometric methods (spectrophotometric equipment). Jackson

turbidity unit (JTU) values also approximate NTU but the JTU is no

longer in common use (EPA Guidance Manual Turbidity Provisions,

1999).

2.1.1 TURBIDITY CHANGES IN WATER SOURCES The turbidity in streams and rivers is a constantly changing

phenomenon. During dry periods, when no precipitation occurs,

turbidity levels usually drop to a somewhat stable value for the

stream. A precipitation event in the watershed can then bring

additional suspended material into the stream and greatly increase

the turbidity. Generally, the more intense the precipitation event is

the higher is the turbidity values experienced in the stream. In

addition, turbidity levels are typically found to be higher further

downstream in a watershed due to the amount contributed from

upstream, the variety of contributing factors it contains, and

biological growth that accumulates in the stream as the water moves

through the basin (Turbidity Guidelines, 1995).

Removal of turbidity from river water is a problem faced by water

treatment plants for producing potable water from river water,

especially during the dry season when silt is sucked into the

pumping well. Inorganic coagulants such as alum combined with

lime have been conventionally used for the removal of raw water

14

turbidity. The sludge obtained from such treatment poses disposal

problems and tends to accumulate in the environment (Turbidity

Guidelines, 1995).

Under normal weather conditions raw water turbidity is typically

below 10 NTU. Such conditions are referred to as low turbidity

period. The turbidity of raw water can increase to several hundreds

or even thousands of NTU in a day, and can continue to exceed 100

NTU over the succeeding 2 to 3 weeks. These conditions are

referred to as the high turbidity periods (Lin et al., 2004).

2.1.2. EFFECTS OF TURBIDITY ON HUMAN HEALTH AND AQUATIC LIFE

Health Effects: Turbidity may be composed of organic and/or

inorganic constituents. Organic particulates may harbor

microorganisms. Thus, turbid conditions may increase the possibility

for waterborne disease. Inorganic constituents have no notable

health effects (Turbidity Guideline, 1995). Many of the causes of

turbidity are not necessarily harmful to human health, but turbidity

can be a sign of another, more serious problem. Generally, as the

pollutant level of water increases, the turbidity increases (USEPA

Geological Survey, 1998).

Industrial Effects: Turbid water may not be suitable for use in

industrial processes. The abundance of suspended solids may clog

or scour pipes and machinery (Turbidity Guideline, 1995).

Recreational Effects: Highly turbid waters may be hazardous to the

welfare of swimmers and boaters. Turbidity may obscure potentially

dangerous obstructions such as boulders and logs. The organic

15

constituents of turbid waters may harbor high concentrations of

bacteria, viruses, and protozoan (Turbidity Guideline, 1995).

Environmental Effects: The series of turbidity-induced changes

that can occur in a water body may change the composition of an

aquatic community. First, turbidity due to a large volume of

suspended sediment will reduce light penetration, thereby

suppressing photosynthetic activity of phytoplankton, algae, and

macrophytes, especially those further from the surface. If turbidity is

largely due to algae, light will not penetrate very far into the water,

and primary production will be limited to the uppermost layers of the

water. Cyano bacteria (blue-green algae) are favored in this situation

because they possess flotation mechanisms. Overall, excess

turbidity leads to fewer photosynthetic organisms available to serve

as food sources for many invertebrates. As a result, overall

invertebrate numbers may also decline, which may then lead to a

fish population decline (USEPA Geological Survey, 1998; Turbidity

Guideline, 1995).

If turbidity is largely due to organic particles, dissolved oxygen

depletion may occur in the water body. The excess nutrients

available will encourage microbial breakdown, a process that

requires dissolved oxygen. In addition, excess nutrients may result in

algal growth. Although photosynthetic by day, algae respire at night,

using valuable dissolved oxygen. Fish deaths often result from

extensive oxygen depleting protozoan (Turbidity Guideline, 1995).

High concentrations of particulate matter can modify light

penetration, cause shallow lakes and bays to fill in faster, and

smother benthic habitats impacting both organisms and eggs. As

particles of silt, clay, and other organic materials settle to the bottom,

16

they can suffocate newly hatched larvae and fill in spaces between

rocks which could have been used by aquatic organisms as habitat.

Fine particulate material also can clog or damage sensitive gill

structures, decrease their resistance to disease, prevent proper egg

and larval development, and potentially interfere with particle feeding

activities. If light penetration is reduced significantly, macrophyte

growth may be decreased which would in turn impact the organisms

dependent upon them for food and cover. Reduced photosynthesis

can also result in a lower daytime release of oxygen into the water.

Effects on phytoplankton growth are complex depending on too

many factors to generalize (Turbidity Guidelines 1995).

Very high levels of turbidity for a short period of time may not be

significant and may even be less of a problem than a lower level that

persists longer (Turbidity Guidelines, 1995).

2.1.3 IMPACT OF TURBIDITY IN WATER TREATMENT In the light of the above discussions, control of turbidity in public

drinking water supplies is important for both health and aesthetic

reasons. Excessive turbidity detracts from the appearance of treated

water and can interfere with disinfection processes and the

maintenance of chlorine residual. It can serve as a source of

nutrients for microorganisms as well as interfering with their

enumeration. The adsorptive properties of suspended particles can

lead to a concentration of heavy metal ions and biocides in turbid

waters. Turbidity has also been related to trihalomethane formation

in chlorinated water. In addition, turbidity has often been associated

with unacceptable tastes and odors (Turbidity Guidelines, 1995).

17

Viable coliform bacteria have been detected in waters with turbidities

higher than 3 NTU even in the presence of free chlorine residuals of

up to 0.5 mg/L and after a contact time in excess of 30 minutes

coliform tests have also been reported in water supplies where

chlorination is the only treatment provided. Outbreaks of disease

traced to chlorinated water supplies have been associated with high

turbidity. The occurrence and persistence of microorganisms within

distribution systems have been correlated with turbidity and other

factors (Turbidity Guidelines, 1995).

The effect of turbidity on disinfection efficiency may be frequently

related to the type and nature of the particulates. Surface water

sources in particular may be susceptible to organic substances and

undesired organisms that can impede disinfection or otherwise

cause drinking water quality problems.

2.1.4 TURBIDITY LIMITS FOR WATER TREATMENT Because of all these problems created, turbidity is regulated by

many countries. In The European Commission Council Directive for

Water Quality, Turkish Water Quality Control Regulations, Turkish

Drinking Water Quality Standards- updated version- and EPA’s

Drinking Water Standarts it is stated that the maximum acceptable

value for turbidity in water entering a distribution system is 1

nephelometric turbidity unit (NTU), established on the basis of health

considerations. A less stringent value for turbidity in water entering a

distribution system may be permitted if it is demonstrated that the

system has a history of acceptable microbiological quality and that a

higher turbidity value will not compromise disinfection. Both the

18

European regulations and the Turkish Drinking Water Regulations

are summarized in Appendix A.

Provision of treated water at or below this limit will minimize the

introduction of unfavorable particulate and biological matter into the

distribution system and thereby render better disinfection

opportunity, effectiveness and maintenance. Special site-specific

problems may require more rigorous attention for the production of

low-turbidity water (European Commission on Drinking Water Quality

Standards, 1998).

Turbidity in excess of 5 NTU becomes apparent and may be

objected to by a majority of consumers. Therefore, an aesthetic

objective of 5 NTU has been set for water at the point of

consumption (European Commission on Drinking Water Quality

Standards, 1998).

2.2 COAGULATION AND FLOCCULATION PROCESSES IN WATER TREATMENT

Impurities in water vary in size by about six orders of magnitude,

from a few angstroms to a few hundred microns for suspended

materials. The removal of a large proportion of these impurities in

water treatment is accomplished by sedimentation. However; some

particles called colloids do not have adequate settling velocity to be

removed by sedimentation, since the size of colloids (about 0,01 to

1µm) is so small such that the attractive body forces between

particles are considerably less than the repelling forces of the

electrical charge. Under these stable conditions, Brownian motion

keeps the particles in suspension. Brownian motion occurs by the

constant thermal bombardment of the colloidal particles by the

19

relatively small water molecules that surround them. The

aggregation of these particles into large, more readily settleable

aggregates is essential for successful separation by sedimentation.

This process is called coagulation (Metcalf and Eddy, 2003).

Coagulation and flocculation consist of adding a floc-forming

chemical reagent to water to enmesh or to combine with non-

settleable colloidal solids and slow- settling suspended solids to

produce rapid-settling flocs. Coagulation is the addition and rapid

mixing of a coagulant, resulting in the destabilization of the colloidal

fine suspended solids, and the initial aggregation of the destabilized

particles. Flocculation is the slow stirring or gentle agitation to

aggregate the destabilized particles and forming a rapid-settling floc

(Reynolds, 1982).

2.2.1. STABILITY OF COLLOIDS Since the key to effective coagulation and flocculation is an

understanding of how individual colloids interact with each other, it is

useful to begin a discussion of colloidal stability. Many colloidal

systems can remain unchanged for very long periods of time, even

though they are thermodynamically unstable. A stable colloid is an

irreversible (thermodynamically unstable) colloid that aggregates at

a very slow rate (O’Melia et al., 1972). In other words, stabilization of

colloid refers to the chemical stability of particle, specifically with

respect to the tendency to settle.

The stability of a suspension depends on the number, size, density

and surface properties of solid particles of the dispersed phase and

the density of the dispersion medium. In an aqueous suspension; the

20

particles of the dispersed phase usually have negative electrical

charges. These negative charges are generated on the surface of

solid particles in three ways. First is the isomorphic substitution in

the solid lattice. Second is the ionization of surface groups (such as

OH group in mineral oxides, carboxyl groups of latex particles,

carboxyl or amino groups of proteins). The third method is the

preferential adsorption of ions or ionizable species from the

suspending medium. This negative charge is related to the amount

of protons in the solution or the pH of the surrounding solution

(AWWA, 1999). As the pH increases, the amount of negative the

charge on the surface of the particles increases. The particles

having similar surface charge repel each other. This keeps the

particles from aggregating into larger settable flocs. The hydrophilic

properties of the particles influence how the particles behave in a

way that water molecules form layers of positive and negative

charges around the particles (Faust and Ally, 1998).

The aggregation of colloidal particles can be considered as involving

two separate distinct steps:

(1) Particle transport to effect particle interparticle contact, and

(2) Particle destabilization to permit attachment when contact

occurs (O’Melia et al., 1972).

Because of the negative surface charge, ions of opposite charge in

the solution will be attracted towards the surface. The counter ions

(e.g. Ca 2+ or Mg 2+) are present in surrounding water. They

accumulate on the surface of the suspended particles. There will be

a higher concentration of the counter ions close to the surface than

in the bulk of the liquid. This concentration falls off with increasing

distance from the particle surface. Thus, there is a bound layer

21

(Stern layer) of the counter ions at the particle surface and after this

layer; a more diffused layer still exists. Only the bound layer moves

with particles. There is a plane of shear between the bound layer

and the diffuse layer. The potential difference between the plane of

shear and bulk solution is called the zeta potential. As the zeta

potential increases, the Columbian repulsion between the particles

becomes stronger and the suspension becomes more stable. The

double layer composed of the Stern and diffusive layers is shown in

Figure 2.1 (Hart, 2001)

Figure 2. 1 Electrical Double Layer around a sable particle

Coagulation is concerned primarily with the aggregation of

thermodynamically unstable (irreversible) colloids. By the help of the

22

coagulation processes, the rate at which colloidal system aggregates

increases.

Flocculation is usually taken to mean the process in which particles

are interlinked by molecular chains with no change in zeta potential

(Hart, 2001)

As mentioned above colloids in natural water are predominantly

negatively charged and they are stable by virtue of hydration or

electrostatic charge on their surfaces. Depending upon the

conditions, some coagulants can achieve colloidal destabilization by

more than one method. The selection of the proper type and dosage

of coagulant for a particular application requires an understanding of

how these materials function. Destabilization of colloidal particles

can be influenced by the following mechanisms (Faust and Ally,

1998):

• Double layer compression

• Adsorption and charge neutralization

• Entrapment in precipitates (sweep flocculation)

• Interparticle bridging.

THE DOUBLE LAYER The double layer model is used to visualize the ionic environment in

the vicinity of a charged colloid and explains how electrical repulsive

forces occur. It is easier to understand this model as a sequence of

steps that would take place around a single negative colloid if the

ions surrounding it were suddenly stripped away. We first look at the

effect of the colloid on the positive ions, which are often called

23

counter-ions. Initially, attraction from the negative colloid causes

some of the positive ions to form a firmly attached layer around the

surface of the colloid. This layer of counter-ions is known as the

Stern layer. Additional positive ions are still attracted by the negative

colloid but now they are repelled by the positive Stern layer as well

as by other nearby positive ions that are also trying to approach the

colloid. A dynamic equilibrium results, forming a diffuse layer of

counter-ions. The diffuse positive ion layer has a high concentration

near the colloid which gradually decreases with distance until it

reaches equilibrium with the normal counter-ion concentration in

solution. In a similar but opposite fashion, there is a lack of negative

ions in the neighborhood of the surface, because they are repelled

by the negative colloid. Negative ions are called co-ions because

they have the same charge as the colloid. Their concentration will

gradually increase as the repulsive forces of the colloid are screened

out by the positive ions, until equilibrium is again reached with the

co-ion concentration in solution (Singh et al., 2003)

DOUBLE LAYER THICKNESS The diffuse layer can be visualized as a charged atmosphere

surrounding the colloid. At any distance from the surface, its charge

density is equal to the difference in concentration of positive and

negative ions at that point. Charge density is greatest near the

colloid and rapidly diminishes towards zero as the concentration of

positive and negative ions merge together.

The attached counter-ions in the Stern layer and the charged

atmosphere in the diffuse layer are what we refer to as the double

layer. The thickness of the double layer depends upon the

24

concentration of ions in solution. A higher level of ions means more

positive ions are available to neutralize the colloid. The result is a

thinner double layer. Decreasing the ionic concentration (by dilution,

for example) reduces the number of positive ions and a thicker

double layer results.

The type of counter-ion will also influence double layer thickness.

Type refers to the valence of the positive counter-ion. For instance,

an equal concentration of aluminum (Al+3 ) ions will be much more

effective than sodium (Na+ ) ions in neutralizing the colloidal charge

and will result in a thinner double layer. Increasing the concentration

of ions or their valence are both referred to as double layer

compression. Increasing the level of ions in solution reduces the

thickness of the diffuse layer (Singh et al., 2003).

ZETA POTENTIAL The negative colloid and its positively charged atmosphere produce

an electrical potential across the diffuse layer. This is highest at the

surface and drops off progressively with distance, approaching zero

at the outside of the diffuse layer. The potential curve is useful

because it indicates the strength of the repulsive force between

colloids and the distance at which these forces come into play. A

particular point of interest on the curve is the potential at the junction

of the Stern layer and the diffuse layer. This is known as the zeta

potential. It is an important feature because zeta potential can be

measured in a fairly simple manner, while the surface potential

cannot (Singh et al., 2003).

25

Zeta potential is an effective tool for coagulation control because

changes in zeta potential indicate changes in the repulsive force

between colloids. The ratio between zeta potential and surface

potential depends on double layer thickness. The low dissolved

solids level usually found in water treatment results in a relatively

large double layer. In this case, zeta potential is a good

approximation of surface potential. The situation changes with levels

of ions; the high level of ions compresses the double layer and the

potential curve. Now the zeta potential is only a fraction of the

surface potential (Montogomery, 1985)

BALANCING OPPOSING FORCES The DLVO Theory (named after Derjaguin, Landau, Verwery and

Overbeek) is the classic explanation of how particles interact. It

looks at the balance between two opposing forces - electrostatic

repulsion and van der Waals attraction - to explain why some

colloids agglomerate and flocculate while others not (Sobeck et al.,

2001) .

REPULSION Electrostatic repulsion becomes significant when two particles

approach each other and their electrical double layers begin to

overlap. Energy is required to overcome this repulsion and force the

particles together. The level of energy required increases

dramatically as the particles are driven closer and closer together.

An electrostatic repulsion curve is used to indicate the energy that

must be overcome if the particles are to be forced together. The

26

maximum height of the curve is related to the surface potential

(Sobeck et al., 2001).

ATTRACTION Van der Waals attraction between two colloids is actually the result

of forces between individual molecules in each colloid. The effect is

additive; that is, one molecule of the first colloid has a van der Waals

attraction to each molecule in the second colloid. This is repeated for

each molecule in the first colloid and the total force is the sum of all

of these. An attractive energy curve is used to indicate the variation

in attractive force with distance between particles (Sobeck et al.,

2001).

THE ENERGY BARRIER The DLVO theory combines the van der Waals attraction curve and

the electrostatic repulsion curve to explain the tendency of colloids to

either remain discrete or to flocculate. The combined curve is called

the net interaction energy. At each distance, the smaller energy is

subtracted from the larger to get the net interaction energy. The net

value is then plotted above if repulsive, below if attractive and the

curve is formed. The net interaction curve can shift from attraction to

repulsion and back to attraction with increasing distance between

particles. If there is a repulsive section, then this region is called the

energy barrier and its maximum height indicates how resistant the

system is to effective coagulation (Sobeck et al., 2001).

In order to agglomerate, two particles on a collision course must

have sufficient kinetic energy (due to their speed and mass) to jump

over this barrier. Once the energy barrier is cleared, the net

27

interaction energy is all attractive. No further repulsive areas are

encountered and as a result the particles agglomerate. This

attractive region is often referred to as an energy trap since the

colloids can be considered to be trapped together by the van der

Waals forces (Sobeck et al., 2001).

LOWERING THE ENERGY BARRIER For really effective coagulation, the energy barrier should be lowered

or completely removed so that the net interaction is always

attractive. This can be accomplished by either compressing the

double layer or reducing the surface charge (Sobeck et al., 2001).

Double Layer Compression Double layer compression involves the addition of large quantities of

an indifferent electrolyte (e.g., sodium chloride). The indifference

refers to the fact that the ion retains its identity and does not adsorb

to the colloid. This change in ionic concentration compresses the

double layer around the colloid and is often called salting out

(Sobeck et al., 2001)

The DLVO theory indicates that this results in a lowering or

elimination of the repulsive energy barrier. It is important to realize

that salting out just compresses the colloid's sphere of influence and

does not necessarily reduce its charge. In general, double layer

compression is not a practical coagulation technique for water

treatment but it can have application in industrial wastewater

treatment if waste streams with divalent or trivalent counter-ions

happen to be available (Sobeck et al., 2001).

28

2.2.2 COAGULATION MECHANISMS

2.2.2.1 DOUBLE LAYER COMPRESSION The negative colloid and its positively charged atmosphere produce

an electrical potential across the diffuse layer. This is highest at the

surface and drops off progressively with distance, approaching zero

at the outside of the diffuse layer. The potential curve given in Figure

2.1 indicates the strength of the repulsive force between colloids and

the distance at which these forces come into play. A particular point

of interest on the curve is the potential at the junction of the Stern

layer and the diffuse layer. This is known as the zeta potential. It is

an important concept because zeta potential is the potential at the

surface of shear, i.e. the boundary surface between the fixed ion

layer and the solution. This layer acts as a Shear plane when the

particle undergoes movement in the solution. Zeta potential is an

effective tool for coagulation control because changes in zeta

potential indicate changes in the repulsive force between colloids

(Hart, 2001).

A coagulant is added to help destabilize the particles. A coagulant

can do this in three ways. A cationic coagulant reduces the zeta

potential of the particles by adding positive charge. This is usually

accomplished by adding a metal salt to the water. The metal forms

strong bonds with the oxygen of the water molecules weakening

them and releasing hydrogen ions into solution. The hydrogen ions

are attracted to the negative surface charge of the particles and

neutralize it (AWWA, 1999).

29

Double layer compression involves adding salts to the system. As

the ionic concentration increases, the double layer and the repulsion

energy curves are compressed until there is no longer an energy

barrier. Particle agglomeration occurs rapidly under these conditions

because the colloids can just about fall into the van der Waals “trap”

without having to surmount an energy barrier (Zeta-Meter, Inc.,

1993).

The thickness of the double layer depends upon the concentration of

ions in solution. A higher level of ions means more positive ions are

available to neutralize the colloid. The result is a thinner double

layer. Decreasing the ionic concentration (by dilution, for example)

reduces the number of positive ions and a thicker double layer

results (Zeta-Meter, Inc., 1993).

The type of counter-ion will also influence double layer thickness.

Type refers to the valence of the positive counter-ion (Zeta-Meter,

Inc., 1993) and its effect is explained in a previous section.

Increasing the concentration of ions or their valence are both

referred to as double layer compression. The quantity of ions in the

water surrounding a colloid has an effect on the decay function of

the electrostatic potential. The high ionic concentration compresses

the layers composed predominantly of counter ions toward the

surface of the colloid. If this layer is sufficiently compressed, then the

Van der Waals force will be dominant across the entire area of

influence, so that the net force will be the attractive force (O’Melia et

al.,1972).

In general, double layer compression is not a practical coagulation

technique for water treatment but it can have application in industrial

30

wastewater treatment if waste streams with divalent or trivalent

counter-ions happen to be available (Singh et al, 2003).

2.2.2.2 ADSORPTION AND CHARGE NEUTRALIZATION

Inorganic coagulants (such as alum) and cationic polymers often

work through charge neutralization. It is a practical way to lower the

DLVO energy barrier and form stable flocs. Charge neutralization

involves adsorption of a positively charged coagulant on the surface

of the colloid. This charged surface coating neutralizes the negative

charge of the colloid, resulting in a near zero net charge.

Neutralization is the key to optimizing treatment before

sedimentation, granular media filtration or air flotation. Adsorption of

the counter ions on the colloid surface causes charge neutralization,

which brings about van der Walls forces become dominant (O’Melia

et al., 1972). Charge neutralization alone will not necessarily

produce dramatic macroflocs (flocs that can be seen with the naked

eye). Microflocs (which are too small to be seen) may form but will

not aggregate quickly into visible flocs. Charge neutralization is

easily monitored and controlled using zeta potential. This is

important because overdosing can reverse the charge on the colloid,

and redisperse it as a positive colloid. The result is a poorly

flocculated system (Hart, 2001).

When a coagulant salt is added to water, it dissociates, and the

metallic ion the metallic ion goes hydrolysis and creates positively

charged hydroxometalic ion complexes. The hydroxometallic ions

are polyvalent, possess high positive charges, and adsorbed to the

surface of the negative colloids. This results in a reduction of the

zeta potential to a level where the colloids are destabilized. The

31

destabilized particles, along with their adsorbed hydro-metallic

hydroxometallic complexes, aggregate by interparticulate Van der

Waals forces. These forces are aided by the gentle mixing in water

(Reynolds, 1982).

2.2.2.3 ENMESHMENT IN A PRECIPITATE Colloid entrapment involves adding relatively large doses of

coagulants, usually aluminum or iron salts which precipitate as

hydrous metal oxides. The amount of coagulant used is far in excess

of the amount needed to neutralize the charge on the colloid. Some

charge neutralization may occur but most of the colloids are literally

swept from the bulk of the water by becoming enmeshed in the

settling hydrous oxide floc. This mechanism is often called sweep

floc. Sweep floc is achieved by adding so much coagulant to the

water that the water becomes saturated and the coagulant

precipitates out. Then the particles get trapped in the precipitant as it

settles downward (Hart, 2001).

2.2.2.4 INTERPARTICULAR BRIDGING

Bridging occurs when a coagulant forms threads or fibers which

attach to several colloids, capturing and binding them together.

Inorganic primary coagulants and organic polyelectrolytes both have

the capability of bridging. Higher molecular weights mean longer

molecules and more effective bridging (Hart, 2001).

Bridging is often used in conjunction with charge neutralization to

grow fast settling and/or shear resistant flocs. For instance, alum or

32

a low molecular weight cationic polymer is first added under rapid

mixing conditions to lower the charge and allow microflocs to form.

Then a slight amount of high molecular weight polymer, often an

anionic, can be added to bridge between the microflocs. The fact

that the bridging polymer is negatively charged is not significant

because the small colloids have already been captured as microflocs

(Hart, 2001).

In recent years the coagulation and flocculation of colloidal

suspensions by organic polyelectrolytes has become increasingly

important, since both laboratory and plant scale work have

demonstrated their effectiveness in extremely low concentrations.

The polymeric substances started to be used as a coagulant have a

specific site, which can be adsorbed by the colloidal particles

possessing long chain structure. These polymers are highly surface

reactive. Thus, several colloids may become attached to one

polymer, and several of the polymer-colloid groups may become

enmeshed resulting in a settleable mass. In order to assist

interparticle bridging, some synthetic polymers may be used in

addition to, organic polyelectrolytes instead of metallic salts (O’Melia

et al.,1972).

Adsorption sites on the colloidal particles can adsorb a polymer

molecule. A bridge is formed when one or more particles become

adsorbed along the length of the polymer. Bridge particles become

intertwined with other bridged particles during the flocculation

process. Besides this mechanism, many other mechanisms take

place in interparticular bridging (O’Melia et al.,1972) as shown in

Figure 2.2.

33

Figure 2. 2 Possible Polymer Particle Interaction (Adapted from O’Melia et al., 1972)

To be effective in destabilization, a polymer molecule must contain

chemical groups, which can interact with sites on the surface of the

colloidal particle. When a polymer molecule comes into contact with

a colloidal particle, some of these groups adsorb at the particle

surface, leaving the remainder of the molecule extending out into the

solution (Reaction 1 in Figure 2.2) If a second particle with some

vacant adsorption sites contacts these extended segments,

attachment can occur (Reaction 2 in

34

Figure 2. 2 Possible Polymer Particle Interaction (Adapted from

O’Melia et al., 1972).) A particle- polymer- particle complex is thus

formed in which the polymer serves as a bridge. If a second particle

is not available, in time the extended segments may eventually

adsorb on other sites on the original particle, so that the polymer is

no longer capable of serving a bridge (Reaction 3 in Figure 2.2)

Dosages of polymer, which are sufficiently large to saturate the

colloidal surfaces, produce a restabilized colloid, since no sites are

available for the formation of interparticle bridges (Reaction 4 in

Figure 2.2) Under certain conditions, a system , which has been

destabilized and aggregated, can be restabilized by extended

agitation, due to the breaking of polymer- surface bonds and the

subsequent folding back of extended segments onto the surface of

the particles (Reactions 5 and 6 in Figure 2.2) (O’Melia et al.,1972).

2.2.3 COMMONLY USED COAGULANTS IN WATER TREATMENT

Different chemicals can be used as coagulants. The most common

coagulants are:

• Aluminum sulfate (also referred to as alum),

• Ferric sulfate,

• Ferric chloride,

• Lime,

• Polyelectrolytes (synthetic or natural polymers).

Coagulant-aids are also sometimes used. These are substances

added in very small quantities to improve the action of the primary

35

coagulant. The characteristics of some example coagulants are

stated below.

ALUMINUM SULFATE (ALUM) Aluminum sulfate, also known as alum, is one of the most common

coagulants used today. It has been used in water treatment for many

years. The United States has been using alum in water treatment

systems since the late 1800s (AWWA, 1999). The chemical formula

for alum is Al2(SO4)3. It is a hydrolyzing metal salt coagulant. This

means that the way in which alum destabilizes the particles in water

is through hydrolysis. The alum is dissolved in water and the

aluminum ions, Al3+ that form, have a high capacity to neutralize the

negative charges which are carried by the colloidal particles and

which contribute to their stability. The aluminum ions form strong

bonds with the surrounding oxygen of the water molecules. This

weakens the atomic structure of the water molecules and positive

hydrogen ions are released into the solution (AWWA, 1999). The

aluminum ions hydrolyze and in the process form aluminum

hydroxide, Al(OH)3 which precipitates as a solid. During flocculation

when the water is slowly stirred the aluminum hydroxide flocs "catch"

or enmesh the small colloidal particles. The flocs settle readily and

most of them can be removed in a sedimentation tank.

The absorption of these hydrogen ions by the negatively charged

particles results in destabilization of the particles as the charge is

neutralized (Hart, 2001). An overdose of alum will produce what is

called sweep floc. The alum that precipitates out of solution will

settle to the bottom of a sedimentation basin, entrapping particles on

its way down removing them from the effluent.

36

Every coagulant has an optimal pH range in which it works the best.

Alum is most effective when working in a pH range between 5.5 and

6.5 (Davis and Cornwell, 1998). Since aluminum may be harmful at

high concentrations it must be allowed to precipitate completely as

the hydroxide. Complete precipitation is a function of the pH of the

water and the pH must therefore be closely controlled between 5.5

and 6.5 (Water Research Commission, 2002).

FERRIC CHLORIDE, FeCl3 Ferric chloride, FeCl3, is another common coagulant. It has been

used in high-rate filtration plants since the 1880s for its ability to

reduce the turbidity of the water (AWWA, 1999). Working as a

cationic coagulant, ferric chloride reacts with the water in a similar

manner as alum causing a hydrolysis effect. The resulting products

of that reaction neutralize the charge on the particles and destabilize

the particles allowing them to aggregate when slight motion is added

to the solution. Ferric chloride can also be used as a sweep floc

coagulant (AWWA, 1999).

Ferric chloride can be purchased in a liquid or dry form. The ferric

salts have a wider optimal pH range than alum as ferric salts can be

used between pH 4 and 9 (Davis and Cornwell, 1998). In the

absence of alkalinity, the reaction between ferric chloride and water

produces hydrochloric acid, which will lower the pH and present a

need for a pH adjuster.

When added to water, the iron precipitates as ferric hydroxide,

Fe(OH)3 and the hydroxide flocs enmesh the colloidal particles in the

37

same way as the aluminum hydroxide flocs do. The optimum pH for

precipitation of iron is not as critical as with aluminum and pH values

of between 5 and 8 give good precipitation. The reaction can be

presented in a similar way as for aluminum sulfate (Water Research

Commission, 2002).

The coagulation of metallic salts releases hydrogen ions as well as

coagulant species. These hydrogen ions neutralize alkalinity and if

the initial alkalinity of water is low, the buffering capacity of the water

will be destroyed and the initial pH of the water will decrease rapidly

during the coagulation process (AWWA, 2002).

LIME Lime is also used as coagulant, but its action is different than that of

alum and ferric chloride. When lime is added to water the pH

increases. These results in the formation of carbonate ions from the

natural alkalinity in the water. The increase in carbonate

concentration together with calcium added in the lime results in the

precipitation of calcium carbonate, CaCO3. The calcium carbonate

crystals enmesh colloidal particles in the same way as alum or ferric

flocs.

When lime is used as coagulant the pH has to be lowered in order to

stabilize the water chemically. Carbon dioxide is normally used for

this purpose.

38

POLYELECTROLYTES Polyelectrolytes are mostly used to assist in the flocculation process

and are often called flocculation aids. They are polymeric organic

compounds consisting of long polymer chains that act to enmesh

particles in the water.

A polymer is a chain of small subunits or monomers. Many polymers

contain only one kind of monomer; nevertheless some contain two or

three different types of subunits. The total number of subunits in

synthetic polymer can be varied, producing material and different

molecular weight. The polymer is called polyelectrolyte depending

on contained ionizable group. The classification is done according to

ionizable group; the polyelectrolytes can be:

• Cationic, i.e. carry a positive charge,

• Anionic, i.e. carry a negative charge,

• Non-ionic, i.e. have no net charge (Nozaic et al., 2001.)

The ability of a polymer to act as a flocculant depends on its ability to

bond to the surface of the colloidal particles making them quite

specific for destabilization of the colloids. Some other important

parameters, which affect the performance of a particular polymer,

are its molecular weight and degree of branching. Moreover, solution

characteristics can be important.

Polymers are different than inorganic coagulants in several ways.

Polymers remove particles by a mechanism called bridging. One or

more reactive groups on the molecular chain absorb the particles.

The effectiveness of polymers does not necessarily increase with

increased dosage. Their peak efficiency is within a specific dose

39

range and will begin to drop off if the dosage increases beyond a

certain point because the particles become re-stabilized (Nozaic et

al., 2001). The sludge produced from polymeric coagulants dewaters

more readily than sludge produced from metal salt coagulants

(Nozaic et al., 2001). Another advantage to polymeric coagulants is

that they do not affect the pH of the effluent (Nozaic et al., 2001).

Therefore the pH does not have to be adjusted several times during

the treatment process as is often required with the metal salt

coagulants. This saves money and time in treating the water.

Another added benefit to polymeric coagulants is that they contain

little or no aluminum. Researchers have established a link between

aluminum and Alzheimers disease; however, it is unknown whether

aluminum causes or is a result of the disease. Because the

relationship is uncertain, the public is somewhat skeptical of

aluminum being used in the treatment of water (Nozaic et al.,2001).

Polymeric coagulants do not cause a problem in this regard.

Polymeric coagulants are less expensive than metal salt coagulants

on the basis of overall chemical treatment. The treatment of water

with polymeric coagulants costs less overall than that treated with

alum comparing the sludge volume to be handled, the amount of

polymer to be used, etc. According to Nozaic et al.(2001), the total

water treatment cost decreased at Umgeni Water treatment plant

when the plant switched from inorganic coagulants to synthetic

organic polymeric coagulants, despite the fact that the amount of

water treated increased. This is because polymers require a lower

dose (usually about 1/10 the dose of a metal salt coagulant) and

therefore the pumps required are smaller and need less

maintenance (Nozaic et al., 2001). They rarely require pH

40

adjustments in the treatment process either because they tend to

keep the pH of the solution relatively stable.

Polymeric coagulants however, have some disadvantages. They

cannot reduce the turbidity of the water to the degree that the

inorganic metal salts can. They also could not be used if the goal of

the treatment included removing organics from the effluent.

Sometimes polymeric coagulants do not work as well in the

presence of chlorine. As already stated, they have a very small

range of efficiency and if an over dose occurred re-stabilization could

produce a major problem and clog the filters. The sludge polymeric

coagulants produce is often stickier and is sometimes harder to

remove from the hoppers especially if they were designed for the

metal salt coagulants (Nozaic et al., 2001).

Pulaski stated that when anionic polymers are used to destabilize

negative colloids, theory and observation indicate that divalent metal

ions must be present that a minimum polymer size must be provided

to overcome the activation energy barrier between colloid surface

and polymeric coagulant. On contrary to metal salts, necessary

optimization for the optimum coagulations takes longer time for the

polymeric coagulants, however once these condition are

established, using these can be efficient and economical (Nozaic et

al., 2001).

The concentration of divalent cations in the water can have a greet

effect on the ability of anionic polyelectrolytes to aggregate. Gregor

proposed three ways in which calcium ions may affect anionic

polymer clay systems:

41

1) These divalent ions induce the double layer compression

resulting in the reducing repulsive forces between clay

particles, which prevent aggregation.

2) These ions aid attachment by reducing the repulsive forces

between clay and anionic polymer.

3) Adsorbed polyelectrolytes tend to repel each other due to

their similar charges. Divalent ions may reduce the repulsion

forces and permit additional adsorption (Gregor, et al., 1995).

It may be stated that divalent metal ions will significantly change the

effective size of the anionic polymer molecules. It appears that a

minimum size is necessary in order for polymers to bridge the

potential energy barrier between two negative colloids when anionic

or non-ionic ones are used. This minimum size depends one such

factor as the number of charged particles, the charge on the colloidal

particles and the ionic strength of the medium (Moe, S.T. et al,

1995). However, regardless of the mechanism(s) there is strong

evidence that divalent metal ions are necessary for anionic polymers

to flocculate negative colloid (Moe, et al, 1995).

Organic polymers or polyelectrolytes could be group into two groups

depending on their origin:

• Synthetic polymers,

• Natural polymers

Since there is some uncertainty about the long-range toxicity,

carcinogenicity, and mutagenicity of synthetic polymers for humans

(Kawamura, 1991) natural polyelectrolytes, which can be extracted

42

from certain kinds of plant and animal life, became a workable

alternative to synthetic polyelectrolytes. Natural polymers, mainly

polysaccharides, are moderately efficient due to their low molecular

weights are shear stable, biodegradable, cheap and easily available

from reproducible farm and forest resources. Advantages of these

natural polyelectrolytes include safety to human health,

biodegradability, and a wider effective dosage range of flocculation

for various colloidal suspensions (Kawamura, 1991).

However the biodegradability of natural polymers reduces their shelf

life and needs to be suitably controlled. Their required dosages are

large and their solutions and flocs lose stability and strength

because of biodegradability. It is evident that all polymers, whether

natural or synthetic, have one or more disadvantages. In the past,

several attempts have been made to combine the best properties of

both by grafting synthetic polymers onto the backbone of natural

polymers after purification. One of the greatest advantages gained is

the consequent reduced biodegradability because of a drastic

change in the original regular structure of the natural polymer as well

as the increased synthetic polymer content within the product. It is

also observed that the grafting of shear degradable polymers onto a

rigid polysaccharide backbone provides fairly shear stable systems

(Singh et al., 2003).

2.3 NATURAL POLYMERS - ALGINATE Synthetic organic polymers have been used as an effective

coagulant aid in drinking water purification systems. However,

organic polymers have potential limitations. Polymer formulations

contain contaminants from the manufacturing process such as

43

residual monomers, other reactants, and reaction by-products that

could potentially negatively impact human health. Polymers and

product contaminants can react with other chemicals added to the

water treatment process to form undesirable secondary products.

Thus, in recent years, there has been considerable interest in the

development of natural coagulants. Natural polyelectrolytes, which

can be derived from certain kinds of plants and animal life, are

workable alternatives to synthetic polyelectrolytes or alum. The

advantages of these natural polyelectrolytes over the synthetic ones

include safety to human health, biodegradability and a wider

effective dose range of flocculation for various colloid suspension

(Al-Samawi, et al., 1996)

Today there are several naturally derived substances used as

polyelectrolytes, most of them being based on a polysaccharide

skeleton with anionic properties due to the presence of carboxyl

groups. An advantage of natural polyelectrolytes, especially for their

use in potable water treatment, is that in general they are virtually

toxic free (Al-Samawi, et al., 1996).

Considering the potential amount available as a natural resource

and reproducibility of alginic acid, it occurred to researchers and

biotechnologists that it would be meaningful to develop alginate as a

source for the biodegradable or edible films (Pavlath et al., 1999).

In 1881, the British chemist E.C.C. Stanford first described the

existence of alginate in brown algae as the most abundant

polysaccharide, comprising up to 40% of the dry matter. Microbial

alginate was discovered, more than 80 years later, by Linker and

Jones (1964), when isolating and partially characterizing the

exopolysaccharide from a mucoid strain of Pseudomonas

44

aeruginosa isolated from the sputum of a cystic fibrosis patient. Two

years later, Gorin and Spencer (1966) demonstrated that acetylated

alginate could also be produced by the soil bacterium Azotobacter

vinelandii (Sabra et al, 2001).

ALGINATE FROM BROWN ALGAE The term algae refers to a large and diverse assemblage of

organisms that contain chlorophyll and carry out oxygenic

photosynthesis. It is important to note that brown algae are also

oxygenic phototrophs, but is eubacteria (true bacteria), and are

therefore evolutionarily distinct from algae.

Although most algae are microscopic in size and are thus

considered to be microorganisms, several forms are macroscopic in

morphology. These colonial forms of algae occur as aggregates of

cells. In turn, each of these cells share common functions and

properties, including the storage products they utilize as well as the

structural properties of their cell walls (Rehm, et al., 1997).

The brown algae are an important assemblage of plants that are

classiffed in about 265 genera with more than 1500 species (Bold, et

al., 1985). They derive their characteristic color from the large

amounts of the carotenoid fucoxanthin (which yields a brown color)

contained in their chloroplasts. They occur mainly in the marine

environment, where they appear as an internal component of the

algal cell wall. A typical brown algal cell wall is depicted in Figure

2.3.

45

Figure 2. 3 Cell wall structure in the brown algae. (After Schiewer and Volesky , 1993).

2.3.1 PHYSICO-CHEMICAL PROPERTIES OF ALGINATE Alginate is of interest as a potential biopolymer film or coating

component because of its unique colloidal properties, which include

thickening, stabilizing, suspending, film forming, gel producing, and

emulsion stabilizing (King, 1983 and Moe et al.,1995). It is a

hydrophilic colloidal carbohydrate extracted with dilute alkali from

various species of brown algae. In molecular terms, it is a family of

unbranched binary copolymers of 1-4 linked β-D -mannuronic acid

and α-L- guluronic acid residues of widely varying composition and

sequential structure (King, 1983 and Moe et al., 1995).

Alginic acid is the only polysaccharide, which naturally contains

carboxyl groups in each constituent residue, and possesses various

abilities for functional materials (Ikeda et al., 2000).The most useful

46

and unique property of alginates is their ability to react with

polyvalent metal cations, specifically calcium ions to produce strong

gels or insoluble polymers (Grant, et al 1973 and King,1983). Such

calcium-alginate gels are used in the food processing industry for

producing restructured foods such as meat products, onion rings,

pimento olive fillings, crabsticks, and cocktail berries (Moe et al.,

1995), and in the biotechnology industry for producing beads for

immobilization of cells or enzymes (Brodelius,1984). Due to its

availability and reproducibility, it seemed meaningful to develop

alginic acid as a source for biodegradable or edible films (Kan,

2001).

Though edible films prepared from hydrocolloids like alginate form

strong films, they exhibit poor water resistance because of their

hydrophilic nature (Kan, 2001). The ability of alginate to make strong

and insoluble gels with calcium ions was utilized to improve such

properties of alginate. However, gel formation of alginate with

calcium ions is so instantaneous that it prevents casting to water

(Pavlath et al., 1999).

Commercially available alginates are currently isolated from marine

brown algae. The discovery of bacterial alginates, polymers irregular

structure as composed of D-mannuronic acid and L-guluronic acid,

resulted in several proposals that they could substitute for algal

products. (Sutherland, 1990).

The structural compositions are shown in Figure 2.3. The monomers

of alginate are distributed in blocks of continuous:

47

• Mannuronate residues (M-blocks),

• Guluronate residues (G-blocks), or Alternating residues (MG-

blocks) (Sabra et al., 2001).

Figure 2. 4 The Structural Compositions of Alginate (a) The Monomer Structure of Alginate (b)The Sequence and Bond Formations of Block Structures as an Example (c) The Sequence Of The Block Types

Alginates isolated from different natural sources vary in the length

and distribution of the different block types (Moe et al., 1995) The

variability in monomer block structures and acetylation strongly

affects the physicochemical and rheological properties of the

polymer, and the biological basis for the variability is therefore of

both scientific and applied importance (Moe et al., 1995).

48

Because alginate is a copolymer of guluronic acid (G) and

mannuronic acid (M), and because these two isomers have

significantly different stereochemical structures, the G and M

contents have a significant effect on the gelling abilities of the

alginate. The GG block is able to form a space between the two-

monomer units, which is ideal for fitting in the calcium ion (Figure

2.4). As the calcium ion forms salt with carboxylic acid groups in two

neighboring GG blocks, it can create a strong crosslink between the

two polymer chains, causing gelation when calcium ions are in

contact with the sodium alginate solution. For this reason, alginate

high in G content can form strong and firm gels, whereas those rich

in M contents tend to form weak and soft gels. The MM block adopts

a flat structure and its ability to bind calcium ions is low (Qin, 2003).

The gelling ability is affected by the guluronic acid and mannuronic

acid contents, and by the calcium and sodium contents. High M

alginate exchange ions more readily than high G alginate, and thus

they have better gelling abilities than those of high G alginates. By

introducing sodium ions into the alginate, the gelling ability and

absorption capacities can be improved for the high G alginate

(Onsoyen, 1996).

49

Figure 2. 5 Alginate gel formation and egg-box model in the presence of calcium (not to scale).

M-and G-block sequences shown in Figure 2.5 display significantly

different structures and their proportions in the alginate determine

the physical properties and reactivity of the polysaccharide

(Onsoyen, 1996).

In Figure 2.5 it is shown that in the presence of divalent calcium

ions, the calcium is ionically substituted at the carboxylic site. A

second alginate strand can also connect at the calcium ion, forming

a link in which the calcium ion attaches two alginate strands

together. The result is a chain of calcium-linked alginate strands that

form a solid gel (Simpson, et. al, 2003).

Simpson et al. (2003) indicates that an alginate solution turns into a

hydrogel in the presence of multivalent cations, usually divalent

50

Ca+2, Ba+2 or Sr+2. The hydrogel is formed because blocks of

guluronic residues bind to cations resulting in a three-dimensional

network of alginate strands held together with ionic interactions. The

model that best describes this network is called as the ‘‘egg-box

model’’.

The changes in resultant concentration and type of the cation, and the

changes in frequency and length of continuous guluronic acid units alter

the overall strength of the gel. Meaning that, changes in cation

concentration can alter the number of alginate strands held together in

the ‘‘egg-box’’ model and thus alter the strength of the gel network as

shown in Figure 2.5.

The higher specificity of polyguluronic acid residues for divalent

metals is explained by its ‘‘zigzag ‘‘structure, which can

accommodate the calcium and some other divalent cations more

easily. The alginates are thought to adopt an ordered solution

network, through interchain dimerization of the polyguluronic

sequences in the presence of calcium or other divalent cations of

similar size (see Figure.2.5). The rod-like shape of the poly-L –

guluronic sections results in an alignment of two chain sections

yielding an array of coordination sites, with cavities suitable for

calcium and other divalent cations because they are lined with the

carboxylate and other oxygen atoms of G residues. This description

is known as the ‘‘egg-box’’ model. The regions of dimerization are

terminated by chain sequences of polymannuronic acid residues. As

a result, several different chains may become interconnected and

this promotes gel network formation. The higher is the degree of

linkage, the greater is the resulting viscosity (Simpson et al., 2003).

51

Gel formation is also a function of cation concentration present.

Figure 2.6 shows that at high concentration of calcium alginates form

hydrogels (egg-box model) with an extended network structure,

which may entrap colloidal particles.

Figure 2. 6 The egg-box model of alginate with high and low ca+2 concentrations.

2.3.2 INDUSTRIAL APPLICATIONS AND ECONOMIC ASPECTS OF ALGINATE

High-quality alginates of extreme purity are used in the

pharmaceutical field (Rehm and Valla 1997). One of the most

interesting applications for such high-quality alginate involves the

reversal of type I diabetes by immobilizing insulin-producing cells

within alginate capsules. These capsules have been implanted into

the body of whole animals and even humans are currently being

52

evaluated as a bio-artificial endocrine pancreas (Rehm and Valla,

1997).

Alginate is active in stimulating immune cells to secrete cytokines,

e.g. tumor necrosis factor α, interleu-kin-1 and interleukin-6.

Surprisingly, the response of the immune system appears to depend

upon the sequential structures of alginates, giving the highest

response with M-rich polymers, while G blocks appear to be non-

stimulating. In fact, guluronic acid residues cannot be accepted in

therapeutic preparations, because they trigger unwanted effects,

such as antibody generation (Skjak-Braek, 1992).

Commercially produced alginate is used mainly in the food industry,

which currently consumes about 50% of the alginate produced. It is

used, for example, in ice-creams, frozen custards, cream and cake

mixtures. It has also found applications in beer production,

enhancing the foam, and in fruit drinks, assisting the suspension of

fruit pulp, which makes the product more appealing to the consumer

(Neidleman, 1991).

Textile and paper industries use this polymer, along with other

materials, as sizing, to improve the surface properties of cloth and

paper. This is important prior to printing, to enable the deposition

and adherence of dyes and inks (Sutherland and Ellwood, 1979).

Entrapment within spheres of calcium alginate gel has become the

most widely used technique for immobilizing living cells (algae,

animal cells, bacteria, cyanobacteria, fungi, plant cells and

protoplasts and yeasts). Alginate-immobilized cell systems are used

as biocatalysts in several industrial processes, ranging from ethanol

53

production by yeast cells, to the production of monoclonal antibodies

from hybridoma cells (Skjak-Braek, 1992).

Alginate has also several miscellaneous applications, such as in

pharmaceutical preparations (to form stable emulsions), in dental

impressionable materials, in the coating of tree roots prior to planting

(to ensure a hydrophilic coating for the roots during transport from

the nursery to the planting site) and as an inert pesticide adjuvant in

the coating of fresh citrus fruits.

Table 2.1 summarizes the industrial and biotechnological uses of

alginate. All alginates used for commercial purposes are currently

being produced by the harvesting of brown seaweeds; and in the

global market selling prices are in the range U.S. $ 5–20 per kg for

most applications (Rehm and Valla, 1997). Since the prices of such

alginates are generally low, it seems to be a difficult task to establish

a competitive bacterial production process in this price range.

However, due to environmental concerns associated with sea-weed

harvesting and processing and the possibility of producing high

quality alginate, it is probable that the bacterial alginate may also

become a commercial product.

54

Table 2. 1 A summary of the industrial and biotechnological uses of alginate

Application Application Function of alginate

Textile printing Fixation, color yield and brightness, ensuring even printing

Paper and board treatments Improvement of surface uniformity

Welding-rod production Component of covering materials for welding rods, improving bendability

Can sealing Formation of cords into slits of can lids

Creaming of latex Concentration of natural latex during extraction from rubber plants

Production of ceramics; food for humans and pets

Reduced rates of surface drying; stabilizing, thickening and gelling agent

Pharmaceutical and biotechnology industry

Immobilization of cells, sustained release, dermatology and wound healing, dental-impression materials

2.3.3 COAGULATION MECHANISM OF ALGINATE The major mechanisms of flocculation by polymers are surface

charge neutralization and bridging. The charge neutralization occurs

if the charge of the flocculants is opposite in sign to that of the

suspended particles. The addition of such a polymer to the

suspension will result in an aggregation caused by specific ion

adsorption. For neutral flocculants, the major mechanism of

flocculation is the polymer bridging. In polymer bridging, the high

molecular mass polymer chains are adsorbed onto the particle

surface and form bridges between adjacent particles. Adsorption

55

occurs by electrostatic forces, van der Wall forces, hydrogen

bonding and chemical bonding. The controversy concerning the

bridging and charge neutralization mechanisms of aggregating

aqueous suspensions by adsorption of water-soluble polymers is of

long standing. In their early experimental and theoretical

investigations, LaMer and his school were prominent in advocating

bridging. Hence, there is no question that the bridging mechanism

operates with uncharged polymers to the particles of suspension.

When very long polymer molecules are adsorbed on the surface of

particles, they tend to form loops that extend some distance from the

surface into the aqueous phase and their ends may dangle. These

loops and ends may come in contact with and attached to another

particle forming a bridge between the two particles. This is the

bridging mode of flocculation. Here the charges of particles and/or

polymer do not play any important role. The reason for better

flocculating power of the graft copolymers over the linear polymers is

as follows; essentially polymer bridging occurs because segments of

a polymer chain adsorb on different particles, thus linking the

particles together. In order for effective bridging to occur, there must

be sufficient chain length, which extends for enough from the particle

surface to attach to other particles. In cases of linear polymers, the

polymer segments attach to the surface in trains, project into the

solution as tails or form part of loops, which link trains together. This

way they can form bridges between the colloidal particles to form

flocs. (Singh et al., 2003)

The idea using alginate for turbidity removal was evolved after the

study of Sanin and Vesilind (1996). This research was aiming to

produce a synthetic sludge using alginate rather than aiming for

turbidity removal but provided evidence that alginate could be a

potential polyelectrolyte for coagulation and flocculation as well. So,

56

this current study aims to use alginate in synthetically prepared

turbid water samples having three different turbidity levels: low,

medium and high, and to evaluate it as a potential coagulant for

turbidity removal. Study also involves the use of calcium alginate in

the treatment of a natural water sample taken from the inlet of

Ankara İvedik Water Treatment Plant (IWTP).

57

CHAPTER 3

MATERIALS & METHODS

Several series of laboratory experiments were conducted during this

project. Laboratory experiments included running jar tests, at

different initial turbidities, calcium and alginate concentrations and

testing the effluent water for turbidity, residual calcium concentration,

and for limited number of samples for total organic carbon (TOC).

These experiments were designed to determine the ability of calcium

alginate as a coagulant to remove turbidity.

3.1 MATERIALS

3.1.1 CLAY SUSPENSION First part of the study was conducted using laboratory prepared

turbid water samples. The stock solution was prepared in a way that

2.5 g of clay was allowed to dissolve in 6 l of distilled water by mixing

for 24 hours. The mixing is achieved by the use of a magnetic stirrer

(FALC F30). The turbidity of this sample was determined to be

around 140-160 NTU. This constituted the highest turbidity sample

used in this study. Lower turbidity samples were prepared by diluting

this stock turbidity suspension to yield turbidity values of 150, 80 and

10 NTU values.

58

The clay that was used during the experiment was a negatively

charged colloid. Figure 3.1 shows the zeta potential distribution of

clay suspension before treatment, and its surface charge was as –

9.396 mV determined by MALVERN Nano ZS90.

Figure 3. 1 Zeta Potential Distribution of Clay Suspension before Treatment

Moreover, a mean particle size was measured approximately 10 µm

by MALVERN Mastersizer 2000, which is demonstrated in Figure

3.2.

59

Figure 3. 2 Particle Size Distribution of Suspended Particles before Treatment

3.1.2 RAW WATER The water samples used for the coagulation experiments are taken

from the inlet of Ankara İvedik Water Treatment Plant (IWTP). The

water coming from Çamlıdere and Kurtboğazı reservoirs are mixed

in 1:1 ratio homogeneously as that happens in the actual plant prior

to the treatment of water. Experiments were conducted on these

samples immediately after the water was taken and brought to the

laboratory within 1 day.

60

3.1.1 COAGULANTS AND CHEMICALS

3.1.1.1 ALGINATE Sodium alginate salt from marine brown algae was purchased from

Fluka AG (Buchs, Switzerland) with the following table, Table 3.1.

Table 3. 1 Composition of Alginate in Terms of Its Monomers Used in the Study

Monomer/ Block Percentage

Total G 41

Total M 59

MG 16

GM 16

GG 28

MM 43

A stock solution of alginate was prepared at 2 g/L. To ensure the

freshness of alginate small volumes of a new solution is prepared all

the times just before the experiment. A required amount of this stock

solution was dosed into the jars during jar test experiments.

61

3.1.1.2 CALCIUM CHLORIDE SOLUTION A stock solution of CaCl2.2H2O was prepared as having 73.5 g/L of

concentrate distilled water. Required amounts of this stock solution

were dosed into the jars during jar tests.

3.1.1.3 CALCIUM STANDARD SOLUTION For the residual calcium concentration determination, a calcium

standard at 5000 ppm was diluted to give 0.5 mg/L, 2.5 mg/L and 5

mg/L as stated in Standard Methods using distilled water. Atomic

Absorbtion Spectrometer was calibrated with these standards. The

reason of distilled water use rather than deionized water was to

prevent the matrix effect differences between the samples and the

standards since the samples were prepared using distilled water.

3.1.1.4 SODIUM CHLORIDE 4.193 g of NaCl was dissolved in 250 mL of distilled water to provide

a stock concentration as 18.053 g/L. Required amounts of this stock

solution was dosed into the jars during jar tests

3.1.1.5 MAGNESIUM CHLORIDE 0.725 g of MgCl2.6H2O was dissolved in 250 mL distilled water to

provide a stock concentration as 2.8999 g/L. Required amounts of

this stock solution was dosed into the jars during jar tests.

62

3.1.1.6 P3 Ferrocryl 8720 PWG

P3 Ferrocryl 8720 PWG is the anionic polyelectrolyte used in İvedik

WTP in Ankara along with alum. It has a molecular weight of 6x106

g/mole and a bulk density of 800± 80 kg/m3.

0.0125 g/L of this polyelectrolyte was dissolved in 100 mL of distilled

water to be able to dose it as 0.05mg/L to each jar as proposed by

the plant operators. Since it was difficult to dissolve, 60 minute

mixing period was provided to make sure the complete dissolution of

the polymer.

3.2 METHODS

3.2.1 COAGULATION EXPERIMENT The jar test experiments were performed using a series of 6 glass

beakers and jar test apparatuses, namely VELP Scientifica JLT6

Leaching Jar Test and Aqua Lytic Floc Tester AMF6. Contents of the

jars were mixed by stirring samples with a uniform power input. A 0.5

L of turbid water sample was placed in each of the jars, and at each

set same predetermined dose of CaCI2 solution was added to each

jar as quickly as possible. Then, rapid mixing at 120 rpm for 1 minute

was provided. Right after this, increasing concentration of alginate in

the range of 0.004- 40mg/L was added to the samples and again

rapid mixing at 120 rpm for 1 minute was provided. Then, the

samples were slowly stirred at 40 rpm for another 20 minutes. The

samples were then allowed to settle for 30 minutes, and the

supernatant samples were taken for the measurement of final

turbidity and residual calcium concentration. Maximum care was

63

provided in removing samples for turbidity for not to disturb the

settled flocs.

After jar test treatment, following turbidity measurements samples

were diluted for different dilution rates to measure the residual

calcium concentrations. These samples were kept at 4ºC, if

necessary until the measurement is conducted.

3.2.2 INVESTIGATED VARIABLES A series of independent variables including the initial turbidity, initial

calcium dose, initial alginate dose and order of chemical addition

were tested for their effects on the process.

At later stages of study, magnesium ions and sodium ions were

added to investigate their affects on the process. In addition, effect

of settling time was examined for a series of experiments where the

turbidity removal efficiency was not high. Details of these variables

and the tests conducted are explained below:

3.2.2.1 INITIAL TURBIDITY Since the turbidity is a very important variable of jar test and the

natural waters may vary in terms of their turbidity, low, medium and

high turbidity waters were prepared using the clay sample.

Depending on the water source (river, lake or ground water) and the

environmental events such as rainstorms or agricultural action, the

turbidity of the water source may vary between low levels like 10

NTU and high levels around 1000 NTU. Since most waters come

from reservoirs to treatment plant, the high turbidity values are

64

believed to be not very common and realistic. Therefore, much lower

turbidity values were studied in this work. A high turbid water sample

having 150 NTU was prepared using the clay sample. Similarly,

medium and low turbidity samples were prepared at 80 and 10 NTU,

respectively.

For each set of initial turbidity, tests were done with various calcium

and alginate doses as explained below.

3.2.2.2 CALCIUM DOSE For each set of initial turbidity, tests were done using initial calcium

ion concentrations between 15 mg/L to 200 mg/L (15, 30, 60, 80,

120, 160 and 200 mg/L).

3.2.2.3 ALGINATE DOSE For each set of initial turbidity and for each initial calcium

concentration studied, alginate concentrations varying from 0.004 to

40 mg/L (0.004,0.012, 0.020, 0.032, 0.04, 0.12, 0.2,0.32, 0.4, 0.8,

1.2, 1.5, 1.6, 2, 2.5, 4, 6 10, 20 and 40 mg/L) were dosed into the

water samples to be treated.

3.2.2.4 ORDER OF CHEMICAL ADDITION For turbid water samples having 150 and 80 NTU, two series of

experiments were conducted; in the first series calcium chloride was

dosed as the first chemical and rapidly mixed for 1 minute, followed

by alginate addition with 1 minute rapid mixing as also described in

65

Section 3.2.1. In the second series alginate is dosed first and

calcium is dosed next, following 1 minute rapid mixing of each. The

purpose of this experiment was to get an insight for the flocculation

mechanism using alginate.

3.2.2.5 ADDITION OF SODIUM AND MAGNESIUM For lower turbidity samples at low calcium concentrations where the

system does not work very efficiently, the addition of sodium and

magnesium ion at different doses along with calcium ion were dosed

into the jars. Here the purpose was to observe if these monovalent

or divalent ions improve the effectiveness of the coagulation

process.

3.2.2.6 SETTLING TIME Similarly, for low efficiency sets longer settling times than the regular

30 minutes, namely 60, 90 and 120 minutes, were employed to

investigate the effect of settling time on the removal of turbidity.

3.2.2.7 pH The pH of the clay sample was around 7. The pH value after the jar

test analysis was seen to remain at around 7 regardless of the

studied doses of calcium and alginate. Carboxylic acid dissociation

constants of Mannuranate and Guluranate have been determined as

pKa = 3.38 and pKa= 3.65, respectively and (Davis, T. A., 2003)

since at pH 7 all the carboxylic acid compounds of alginate are

deprotonated, the pH of the system was not changed during the

experiments. Besides pH effect on the performance of the system

66

was considered to be small and was not investigated in this work.

So, the pH all throughout the study was at 7.2±0.2

3.3 ANALYTICAL TECHNIQUES

3.3.1 TURBIDITY MEASUREMENT Turbidity measurements were performed using Nephelometric

method according to the Standard Methods No. 2130 A (Standard

Methods, 1995). Hach DR 2100 A model turbidimeter was used

throughout the experiments. The turbidimeter was calibrated by

using the standards of 100 and 1000 NTU. However, for the

calibration of the turbidimeter to 10 NTU, the standard was prepared

daily right before the measurements as stated in Standard Methods.

3.3.2 CALCIUM MEASUREMENTS Initial and residual calcium concentration at the beginning and at the

end of the jar tests were measured by using either Perkin Elmer 110

B Atomic Absorption Spectrometer or, Perkin Elmer AAnalyst 800

Atomic Absorption Spectrometer according to the Standard Methods

No 3111D (Standard Methods, 1995). The samples were centrifuged

and acidified before the calcium measurements. The pH of diluted

samples prepared for residual calcium concentration measurement

were brought to below 2, using HNO3. The calibration of the atomic

absorption spectrometer was done daily prior to the measurements

using the calcium standard solutions preparation of which is

described in section 3.1.3.3.

67

3.3.3 TOTAL ORGANIC CARBON (TOC) ANALYSIS Since alginate is an organic biopolymer, usage of it may bring a risk

of increasing the dissolved organic carbon content of treated water,

which then may cause formation of carcinogenic halogenated

organic compounds upon chlorination. For this purpose TOC of

some selected samples with initial turbidity of 150 NTU were

measured around the optimum alginate dose. To analyze the TOC,

samples around the optimum dose of alginate were certified

following the jar test treatment and analyzed using an Apollo 2000

TOC analyzer.

3.4 CLEANING OF GLASSWARE For cleaning of all the glassware used in the experimental work, a

dilute solution of 10% Nitric Acid (HNO3) was used.

3.5 EXPERIMENTAL FLOW CHART OF THE STUDY

To give better visualization of this study the flow chart in Figure 3.3

is drawn.

68

(Continued)

Determination of the

interaction of Alginate & Calcium

Determination of the effect of

Alginate & Calcium on system pH

Determination of initial

turbidity, initial calcium & optimum alginate

concentrations

150 NTU Turbid Water Sample

200 mg/L Ca2+

160 mg/L Ca2+

120 mg/L Ca2+

80 mg/L Ca2+

60 mg/L Ca2+

30 mg/L Ca2+

Dosing order effect

Dosing order effect

Dosing order effect

Dosing order effect

Dosing order effect

Dosing order effect

Dosing order effect

80 NTU Turbid Water

Sample

200 mg/L Ca2+

160 mg/L Ca2+

120 mg/L Ca2+

80 mg/L Ca2+

60 mg/L Ca2+

30 mg/L Ca2+

Dosing order effect

Dosing order effect

Dosing order effect

Dosing order effect

Dosing order effect

Dosing order effect

Settling Time Effect

Coagulant Aid Addition

69

Figure 3. 3 Flow Chart for Experimental Works of The Study

10 NTU Turbid Water Sample

80 mg/L Ca2+

60 mg/L Ca2+

30 mg/L Ca2+

Raw Water taken from the inlet of IWTP

120 mg/L Ca2+

80 mg/L Ca2+

60 mg/L Ca2+

30 mg/L Ca2+

15 mg/L Ca2+

Settling time effect

Polyelectrolyte comparison

Settling time effect

Coagulant aid addition effect

Settling time effect

Settling time effect

Settling time effect

Settling time effect

Settling time effect

Settling time effect

70

CHAPTER 4

RESULTS & DISCUSSIONS

4.1 DETERMINATION OF THE INTERACTION BETWEEN CALCIUM AND ALGINATE

The first part of the experimental series was conducted to

understand the general behavior of the interaction between Ca+2

ions and alginate. The determination of starting dose for calcium and

alginate was also achieved at this stage. Clay suspension having 2.5

g/L of concentration was prepared and left to mix for 24 hours in

order to achieve homogeneous dispersion. The initial turbidity values

of clay suspensions tested was 160 NTU.

To a sample of water having 160 NTU initial turbidity two doses of

calcium (150 and 300 mg7L) and two doses of alginate (40 and 20

mg7L) were added

The interaction of the Ca+2 ions and alginate could be easily seen as

soon as alginate was dosed. Figure 4.1 shows the interaction of

calcium ions and alginate. Formation of the flocs having visible, big

and circular shapes was formed immediately at the beginning of the

slow mixing (Figure 4.1 a). Very rapid settling of flocs experienced

as soon as settling time started (Figure 4.1 b). And at the end of 30

minute settling time more clarified water could be obtained (Figure

4.1c).

71

(a)

(b)

(c)

Figure 4. 1 Stages of Experiments (a) Flocs formation during slow mixing stage, (b) Flocs start to settle at the end of slow mixing, (c) Settling achieved at the end of 30 minute settling time.

72

The results obtained from these preliminary experiments are given in

Table 4.1. As stated in Table 4.1, there was a great difference in the

final turbidity values for 300 mg/L and 150 mg/L of calcium

concentration when alginate concentration is fixed both at 40 mg/L and

at 20 mg/L, respectively. The turbidity removal efficiency for 40 mg/L

and 20 mg/L of alginate was about 98% for 300 mg/L of calcium,

whereas this efficiency depended on the alginate dose for 150 mg/L of

calcium concentration. Looking at these results and considering the

earlier studies (Sanin and Vesilind, 1996) as well as the Turkish

Drinking Water Standards, upper limits for calcium and alginate were

set at 200 mg/L and 40 mg/L, respectively.

Table 4. 1 The Results from the Preliminary Analysis

Initial Turbidity (NTU) 160 160 160 160

Alginate Conc. (mg/L) 40 40 20 20

Calcium Conc. (mg/L) 300 150 300 150

Final Turbidity (NTU) 4 78 3 96

From these preliminary analyses tabulated in Table 4.1, it is observed

that there is strong interaction between alginate and calcium ions,

which can be thought as potent coagulant. Moreover, it can be stated

that the efficiency of coagulation and flocculation via alginate is highly

dependent on the calcium concentration.

The following experiments were conducted to come up with an optimal

dose for maximum turbidity removal with the smallest consumption of

calcium and alginate.

73

4.2 ASSESSMENT OF THE EFFECT OF THE INTERACTION BETWEEN CALCIUM AND ALGINATE ON pH

It is known that the polymeric coagulants do not alter the system pH

during coagulation/ flocculation process. The pH values of the calcium

alginate system before and after the coagulation were checked, and

results are tabulated in Table 4.2.

Table 4. 2 Examination of the system pH before and after coagulation

Initial Turbidity (NTU) 160 160 160 160 160

Alginate Conc. (mg/L) 40 20 10 8 4

Calcium Conc. (mg/L) 200 200 200 200 200

Final Turbidity (NTU) 1 1 0.8 0.7 3.4

Initial pH 7.3 7.3 7.3 ≈7.3 7.3

Final pH 7.4 7.4 7.3 7.3 7.4

Formation of the flocs could be easily seen for all of the alginate

dosages with 200 mg/L of calcium immediately after the coagulants are

added. Very rapid settling of flocs was also observed. The turbidity

removal efficiency was always higher than 98%.

When the data in Table 4.2 was examined, no significant pH change

was observed. Therefore, it is stated that the interaction between the

Ca+2 ions and alginate does not alter the pH of the water. Considering

these results, it is assumed that the pH is fixed and unchanged at

about 7.3 all throughout the experimental work.

74

4.3 EVALUATION OF ALGINATE AS A POTENTIAL COAGULANT FOR HIGH TURBIDITY (150 NTU) WATERS

To represent high turbidity water samples, clay suspension was

prepared at 150 NTU turbidity value and a series of experiments

were conducted on them.

To get better understanding of the potential usability of alginate as

coagulant and to determine the effect of the alginate, predetermined

calcium concentrations were dosed only as control variables without

dosing alginate and the results were examined and tabulated in

Table 4.3.

Table 4. 3 Result of the Study to Determine the Effect of Calcium Ion on the Turbidity Removal When Calcium was

Dosed Only.

Calcium

Concentration (mg/L)

Initial Turbidity

(NTU)

Residual Turbidity

(NTU)

Turbidity Removal Rate (%)

200 150 5.5 96.3

160 150 5.1 96.6

120 150 4.9 95.7

80 150 5.6 96.3

60 150 5.4 96.4

30 150 15 90

Table 4.3 states that calcium alone has an important effect on the

removal of turbidity. However, by itself, calcium cannot decrease the

residual turbidity to the limit values required in Turkish or European

Drinking Water Standards. Therefore, it was expected that the usage

75

of alginate as coagulant was going to improve the efficiency of

coagulation.

To verify this expectation the jar test procedure was applied as

described in Materials and Methods. Calcium concentrations were

fixed for each set during which alginate concentrations were

decreased from 40 to 0.004 mg/L (if necessary). Similar experiments

were conducted for calcium concentrations of 200, 160, 120, 80, 60

and 30 mg/L for the 150 NTU of initial turbidity to see the effect of

calcium concentration on effectiveness of coagulation.

It was easy to observe the gel formation and large flocs as soon as

alginate was dosed. Detailed results for this set can be observed in

Appendix B in Table B.1 to B.6. Also Figure 4.2 gives a plot of final

turbidity values with respect to alginate concentration for different

calcium doses, which is plotted for points yielding equal to or less

than 5 NTU of final turbidity to provide better visualization of the

results.

For 200 mg/L of calcium concentration, a decrease in final turbidity

was observed when the alginate dose was decreased from 40 mg/L

to 4 mg/L. The maximum turbidity removal was observed at 4 mg/L

having a final turbidity of 1.1 NTU.

76

0

1

2

3

4

5

0 1 2 3 4 5 6 7 8 9 10

Alginate Concentration (mg/L)

Fin

al T

urb

idit

y (N

TU

)

200 mg/L (10 meq/L) of Ca+2160 mg/L (8 meq/L) of Ca+2120 mg/L (6 meq/L) of Ca+280 mg/L (4 meq/L) of Ca+2

Figure 4. 2 Assessment of the effect of change in calcium concentration on final turbidity (initial turbidity 150 NTU) plotted for samples giving final turbidity as less than 5 NTU.

At the time of experimentation, Turkish Drinking Water Standards

(TS 266) required an allowable turbidity value of finished water

sample as 5 NTU, and maximum allowable calcium concentration of

200 mg/L. Compared to these standards, all the alginate

concentrations studied provided acceptable quality. However, the

Standards have been revised in April 2005, and new standards

require different turbidity limits; 1NTU turbidity level if surface water

sources like river, lake, etc. are treated for drinking purposes, 5 NTU

if groundwater sources are going to be treated. With respect to the

new standards, the turbidity of the water samples is believed to be

only marginally satisfactory following a typical filtration proceeding

77

coagulation/ flocculation/ settling units for alginate concentrations

between 2 and 8 mg/L. The extra 0.5 NTU is believed to be removed

by filtration. At 200 mg /L of calcium concentration dosed to 150

NTU turbid water, however, it was not possible to produce turbidities

low enough to meet the Turkish Drinking Water Standards.

Moreover, before the revision of Turkish Drinking Water Standards

(TSS 266), the final calcium concentration was another important

criterion for drinking water purposes. The required calcium

concentration was 100 mg/L, and the maximum allowable calcium

concentration was attained as 200 mg/L. Although, the new limitation

value for calcium concentration in treated water for drinking

purposes is not submitted in the revised version of TS 266,

maximum allowable 200 mg/L of the residual calcium concentration

stated in TS 266 is taken into consideration through out

experimentation

Considering the results of 150 NTU turbid water with lower doses of

calcium, it can be said from Tables B.2 to B.6 and Figure 4.3 that it

is possible to produce water of enough quality using especially 160

mg/L of calcium concentration over a wide range of alginate doses

covering the range 0.8 to 20 mg/L (Table B.2). For these the

turbidities of the treated water samples are always lower than 1 NTU

within this range and the calcium concentrations are at all

acceptable levels all.

At 120 mg/L of calcium concentration for 150 NTU turbid water

samples, the residual turbidity values were 1 NTU for the alginate

concentrations of 2 and 6 mg/L as minimum. Moreover, the required

final turbidity values could be obtained if filtering is applied following

to coagulation/ flocculation/ sedimentation processes when 2 to 10

mg/L of alginate concentration were applied (Table B.3).

78

When 80 mg/L of calcium was dosed into the turbid water sample

(Table B.4) it was possible to obtain the required quality of water at

alginate doses of 4 mg/L and 10 mg/L. However, it is again believed

that it would be possible to attain the required levels following

filtration for a wider alginate dose between 1.6 to 10 mg/L of

alginate. The calcium concentrations are also well within the

acceptable levels.

As the calcium dose was lowered to 60 mg/L (Table B.5), the

effectiveness of the system was greatly hampered; the lowest

turbidity attainable became 5.1 NTU at an alginate dose of 0.32

mg/L.

A similar situation was valid for the 30 mg/L calcium addition; with

the lowest turbidity achievable was 17 NTU at an alginate dose of

0.12 mg/L. Even though the final calcium concentrations were well

within the acceptable range, due to high residual turbidity values, the

calcium doses of 60 and 30 mg/L was considered ineffective and so

lower doses were not tested.

The optimum alginate concentrations for each of the calcium doses

studied to give the turbidity values in confirmation with the Turkish

Standards are tabulated in the Table 4.4 to summarize the results

presented in Tables B.1 to B.6 in Appendix B. Note that Table 4.4 is

tabulated for the lowest alginate concentration not for the lowest

turbidities attained. Because, the minimum concentration of alginate

used decreases the treatment cost, Moreover, if the final turbidity

values can not meet the requirement, the reduction of residual

turbidity could be achieved by filtration after coagulation/ flocculation/

sedimentation.

79

Table 4.3 declares that for the water samples having 150 NTU of

initial turbidity, as the concentration of calcium decreased, the

optimum alginate dosages decreased with the exception of 160 mg/L

of calcium sample. These results show that when calcium dosed first

the most efficient doses of calcium and alginate for 150 NTU turbid

water sample were 160 mg/L and 0.8 mg/L, respectively.

Table 4. 4 The Optimum Alginate Concentrations for Each of the Calcium Concentrations Dosed, Having 150 NTU of Initial

Turbidity When Calcium Dosed First

Calcium

Concentration (mg/L)

Optimum Alginate

Concentration (mg/L)

Residual Turbidity

(NTU)

Turbidity Removal

Rate (%)

Calcium Ion Removal

Rate (%)

200 4.00 1.1 99.3 32.5

160 0.80 1 99.3 90.5

120 2.00 1 99.3 86.3

80 1.60 1 99.3 20.4

Moreover, it could be reported that Table 4.3 demonstrates that the

usage of alginate improved the turbidity removal efficiency, and the

desired residual turbidity values could be decreased the turbidity

from around 5 NTU to less than 1 NTU when compared with the

control values stated in Table 4.3.

Figure 4.3 summarizes that the turbidity removal efficiencies

decrease as the dose of both calcium and alginate decrease. With

respect to the turbidity removal efficiencies, the efficient removal

could be attained for the calcium concentrations greater than 60

mg/L for the alginate concentrations in the range of 0.2 to 40 mg/L.

The interaction between alginate and 60 mg/L of calcium ion

80

concentration did not have a smooth trend, although its turbidity

removal rates were greater than 50% in general. Considering the

turbidity removal efficiencies for 30 and 60 mg/L of calcium ions, it

could be concluded that below a concentration of 60 mg/L of calcium

ions, calcium- alginate gel was not forming properly. This may be a

result of the fact that before the dosing calcium, the medium of the

suspension was highly anionic. The low concentration of positively

charged calcium ions was not sufficient to neutralize the colloidal

surfaces. After the addition of alginate, the medium turned to than a

more anionic nature, causing the colloids to stay stable.

0

10

20

30

40

50

60

70

80

90

100

40201086421.

600.

80

Alginate Concentration (mg/L)

Per

cen

t T

urb

idit

y R

emo

val (

%)

200 mg/L of Ca+2 160 mg/L of Ca+2 120 mg/L of Ca+2

80 mg/L of Ca+2 60 mg/L of Ca+2 30 mg/L of ca+2

Figure 4. 3 Turbidity Removal Efficiency for Different Calcium Dosages (Initial Turbidity 150 NTU)

Figure 4.4 states that rather than at 120 and 160 mg/L of calcium

concentrations there were little calcium removals. But as can be

81

seen from figure, 120 and 160 mg/L calcium doses were removed

very efficiently from the system especially at higher alginate

dosages. Calcium removals are expected to give some hint about

the turbidity removal mechanism and the interaction of calcium and

alginate. So we may speculate that this is a window (around 120 to

160 mg/L of calcium) where efficient gel formation. The reaction

between calcium and alginate is happening for alginate

concentration of 0.2 mg/L for 40 mg/L.

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

90.0

100.0

40201086421.

600.

800.

40

Alginate Conc. (mg/L)

Per

cen

t C

alci

um

Rem

ova

l (%

)

200 mg/L of Ca+2 160 mg/L of Ca+2120 mg/L of Ca+2 80 mg/L of Ca+260 mg/L of Ca+2 30 mg/L of Ca+2

Figure 4.4 Calcium Ion Removal Efficiency for Different Calcium Dosages (Initial Turbidity 150 NTU)

82

4.4 ASSESSMENT OF THE EFFECT OF THE DOSING ORDER ON RESIDUAL TURBIDITY FOR DIFFERENT CALCIUM

CONCENTRATIONS BY USING THE 150 NTU TURBID WATER SAMPLE

In the previous section calcium ions were dosed first then alginate

was dosed following 1 minute rapid mixing with the calcium ions.

Since the clay studied had a negative surface charge with a zeta

potential value of – 9.396 mV, it is believed that calcium acts as a

surface charge neutralizer before it forms a calcium alginate gel for

the turbidity removal. Control samples shown in Table 4.4 indicate

that calcium acts as a very important agent and only by itself is

available to remove a great amount of turbidity.

To further investigate this mechanism and check if the system would

work when the alginate is added first rather than calcium, the order

of dosing the chemicals is reversed in this part. The results are

summarized in Figure 4.5 and Appendix B in Tables B.7 to B.11.

In this section when alginate solution was added before calcium was

dosed at high concentration of calcium ions, it was easy to observe

bigger flocs formation with a decreasing size as the alginate

concentration was decreased. In other words, larger flocs were more

clearly visible in this part compared to the previous. Also, it was

observed that for the case in which alginate dosing was done first,

the calcium removal efficiency increased. This may be due to the

fact that calcium ions form complexes as well as a gel with

carboxylic groups on the polymer and ionic groups on the particle

(which happens at high calcium concentrations predominantly),

yielding the observed results. Similar results were suggested for the

interactions of cations and anionic polymers (Singh et al., 2003).

83

0

1

2

3

4

5

6

0 1 2 3 4 5 6 7 8 9 10

Alginate Concentration (mg/L)

Fin

al T

urb

idit

y (N

TU

)

200 mg/L (10 meq/L) of Ca+2 160 mg/L (8 meq/L) of Ca+2

120 mg/L (6 meq/L) of Ca+2 80 mg/L (4 meq/L) of Ca+2

Figure 4. 5 Assessment of the Effect of Change in Initial Calcium Concentration on Final Turbidity) When Alginate was Dosed First (plotted only for the data points lower than 5 NTU for clarity).

Moreover, the difference in the size of flocs may be a result of the

fact that divalent metal ions alter the effective size of anionic polymer

by reducing the polymer- colloid interaction and filling the pores of

alginate to form gel structure.

When the results of 200 mg/L calcium addition given in Figure 4.5

and Table B.7 are examined, we see that a greater region where the

turbidity criteria of ≤ 1 NTU is satisfied for the case where alginate is

dosed first. For alginate doses of 4 to 40 mg/L, the produced water

satisfies the turbidity criteria. When the initial calcium concentration

84

was lowered to 160 mg/L, again satisfactory turbidity and calcium

removals are obtained, even at much lower doses of alginate.

Between alginate doses of 0.4 to 2 mg/L final turbidities are all lower

than 1 NTU and the final calcium concentrations are between 12-15

mg/L. However, it should be added that for the calcium concentration

of 160 mg/L, the effective alginate dosing range was broader (0.4-

20 mg/L) when calcium was added first than that when the alginate

(0.4- 2 mg/L) was added first. This calcium dose (160 mg/L) seems

to be effective during which calcium addition was done first. It seems

that with the addition of alginate before calcium, it is possible to

lower the required minimum alginate dose significantly (from 2 mg/L

in the previous run to 0.4 mg/L in this run).

For 120 mg/L of calcium dose, minimum residual turbidity was

observed as 1.1NTU when 0.8 mg/L of alginate dosing was

conducted. It is believed that the target residual turbidity can be

obtained if the process is proceeded by filtration when alginate

concentrations of 0.4 -2 mg/L are dosed first. However, strictly

speaking, it was not possible to achieve the required turbidity levels

with 120 mg/L calcium dose when the alginate was first.

For 80 mg/L of calcium the minimum dose of alginate giving

maximum turbidity removal was 0.4 mg/L yielding a turbidity of 1.8

NTU. However, for the case in which calcium was dosed first, the

effective alginate concentration range was wider than that for the

case in which alginate was dosed.

Considering the change in dosing order (alginate first), a decrease in

the calcium concentration increased the range of alginate

concentration in which the effective turbidity removal could be

85

obtained. In some cases, a further treatment as filtration is expected

to help to meet the required turbidity values.

However, the case of 60 mg/L and 30-mg/L calcium addition, the

effectiveness of the system deteriorated and it was not possible to

go below 20 NTU and 30 NTU turbidity value, respectively.

Therefore lower doses of calcium were not investigated for 150 NTU

of initial turbidity.

Regardless of the mechanisms involved, there is strong evidence

that divalent metal ions are necessary for anionic polymers to

flocculate negatively charged colloids. When the ionic polymers are

used to destabilize negative colloids, theory and observations

indicate that divalent metal ions must be present either naturally or

by direct addition (O’Melia et al., 1982). Our results are in parallel

with this statement. Controls having only alginate going through the

coagulation/ flocculation process are not able to produce required

turbidity removals. As soon as the divalent cation addition is done,

coagulation is achieved. The effectiveness of coagulation is again a

strong function of the divalent cation concentration.

Table 4.5 lists the minimum alginate concentrations that are able to

produce water quality in conformity or close to conformity with

standards. Table 4.5 states that the minimum alginate concentration

decreases as the calcium concentration decreases. However, at low

calcium concentrations, which are not given in Table 4.5, the

turbidity removal efficiency diminishes so does the calcium removal

efficiency.

86

Table 4. 5 The Optimum Alginate Concentrations for Each of the Calcium Concentrations Dosed When Initially Alginate Was Dosed, Having 150 NTU of Initial Turbidity

Calcium

Concentration (mg/L)

Optimum Alginate

Concentration (mg/L)

Residual Turbidity

(NTU)

Turbidity Removal Rate (%)

Calcium Ion Removal Rate (%)

200 4.00 0.9 99.4 36.8

160 0.40 0.8 99.5 92.0

120 0.80 1.1 92.3 99.3

80 0.32 2 98.7 83.6

Moreover, Table 4.5 demonstrates that the usage of alginate also

improved the turbidity removal efficiency when compared to control

variables stated in Table 4.3. The dosing order change did not

cause a significant difference when making comparison of the

results of the cases when calcium dosed initially and when alginate

dosed initially.

Figure 4.6 shows that higher concentration of calcium ions produced

better results when alginate was dosed first with respect to the

turbidity removal efficiency. It is believed that the main mechanism of

removal is the calcium/ alginate gel formation around the colloidal

particles. Whereas in the previous part, the mechanism of turbidity

removal was by surface charge neutralization of the colloids by

calcium ions which was able to remove a significant amount of the

turbidity creating particles without the addition of alginate. However,

results in this part proves that for waters having turbidity of 150 NTU

of doses around 160 mg/L of calcium along with 0.4- 2 mg/L of

alginate causes calcium alginate gel formation, which is able to

clarify the water to the required levels by the drinking water

standards.

87

Figure 4.6 shows that there is an optimum region for alginate, where

neither higher nor lower doses work. This again can be explained by

the fact that higher doses of polymers sufficiently large to saturate

the colloid surface will cause restabilization of the system due to

finishing of the available sites on the particle surface for further

interparticle bridge formation.

0102030405060708090

100

4020108421,

600,

800,

40

Alginate Conc. (mg/L)

Per

cen

t T

urb

idit

y R

emo

val (

%)

200 mg/L of Ca+2 160 mg/L of Ca+2120 mg/L of Ca+2 80 mg/L of Ca+260 mg/L of Ca+2 30 mg/L of ca+2

Figure 4. 6 Turbidity Removal Efficiency for Different Calcium Dosages (Initial Turbidity 150 NTU) When Alginate Was Dosed First.

Figure 4.7 shows that there is a range of initial calcium concentration

for which the highest removal efficiency for calcium was possible.

This is the calcium doses between 120 to 160 mg/L where the

calcium removals were above 90% for alginate doses equal to or

higher than 0.8 mg/L. Higher doses than 160 mg/L (200 mg/L) was

possibly providing excess calcium of that required for gel formation

88

and most of it is left in the solution without being removed. Some

lower doses provided good removal efficiency (80 mg/L) but others

(60 and 30 mg/L) were removed with very low efficiency. However,

these cases do not create a water quality problem since the initial

doses are low already.

0

10

20

30

40

50

60

70

80

90

100

4020108421.

600.

800.

40Alginate Conc. (mg/L)

Pe

rce

nt

Ca

lciu

m R

em

ov

al (

%)

200 mg/L of Ca+2 160 mg/L of Ca+2 120 mg/L of Ca+280 mg/L of Ca+2 60 mg/L of Ca+2 30 mg/L of Ca+2

Figure 4. 7 Change in Calcium Removals With Respect to Applied Alginate Doses at Various Initial Calcium Concentrations (when alginate was dosed first)

The inability to attain the required low turbidity levels as the calcium

dose was decreased can be explained by the fact that the

interactions among the calcium ions, clay colloids and also solute.

Since alginate addition was expected to result in an increase in the

electronegativity of water sample, low calcium concentrations could

not be able to overcome the negative surface charge efficiently at

low doses, so it was not possible to decrease zeta potential, and the

double layer energy to produce effective coagulation.

89

Since the zeta potential value of the clay we used was negative (-

9,396 mV), the addition of calcium ions first causes zeta potential

approaches to zero, which results in better and effective settling.

Therefore, it is not surprising that in the case where calcium ions

dosed first, the removal efficiency of turbidity is higher for a wider

calcium range. In this case where alginate is dosed first the effective

coagulation region remains only at 200 and 160 mg/L of calcium

dose. In this range the dominant mechanism is believed to be gel

formation

4.5 EVALUATION OF TOTAL ORGANIC CARBON (TOC) VALUES DURING COAGULATION WITH CALCIUM ALGINATE TOC, in and of itself, does not affect the physical removal process;

but TOC levels affect the degree of coagulation, flocculation, and

sedimentation required. For example, increases in TOC also

increase the coagulant demand of the water, thus requiring more

coagulant in order to effectively remove the turbidity. Enhanced

coagulation for TOC removal is then required. Organic carbon

affects treatment in two additional ways: pathogens may adhere to

particulate organic carbon and be shielded from disinfection; and

oxidative disinfectants do not preferentially attack pathogenic

organisms. Consequently, the more organic material in the water,

the more disinfectant is spent oxidizing the organic matter (CALFED

Bay-Delta Program, 2000).

Since alginate is totally natural organic material obtained from

marine brown algae, its contribution to TOC content should be

analyzed since organic matters and free chlorine existing in the

90

system can form trihalomethane (THM), which is carcinogenic to

human.

In this section the TOC of the water samples following treatment with

optimum alginate concentration for all calcium doses were measured

and tabulated in Table 4.6.

In fact this is done just to check whether the use of alginate

increases the organic content of water significantly.

Table 4. 6 TOC Measurement Results of Water Samples Treated With Different Calcium Doses Considering Their Optimum Alginate Concentration for 150 NTU of Initial Turbidity

The TOC measurement results shown in Table 4.6 are very low and

are not expected to cause problems. Based on these

Ca+2 Concentration

(mg/L)

Alginate concentration

(mg/L)

TOC Concentration

(mg/L)

200 4.00 0.938

160 0.40 0.661

120 1.60 0.578

80 0.80 0.591

60 0.32 1.034

30 0.12 0.644

200 0.40 0.530

160 0.40 0.685

120 0.80 0.571

80 0.40 0.559

60 0.20 0.704

30 0.0004 0.830

0 0 0.694

91

measurements, it is concluded that at the doses calcium alginate is

used as conditioner, and it does not have effect on the TOC of the

water. Since the same alginate dose range is studied and the

effective doses are within close vicinity of each other and the ones

given in Table 4.6, TOC of treated water samples are not measured

in the later stages of the study thinking that it will not show any

significant changes.

4.5 Evaluation of Alginate as a Potential Coagulant for Medium Turbidity (80 NTU) Water Samples Depending on the factors such as geological, environmental,

structural, temperature, etc turbidities of water samples may vary.

Therefore, 80 NTU was chosen as initial turbidity to represent a

medium turbidity level, and the stock of clay suspension was diluted

to get 80 NTU. Dosing of calcium and alginate were conducted in a

similar fashion to the water samples at 150 NTU. All of the data

obtained in this part are given in Appendix C in Tables C.1 to C.5. In

Table 4.7 the effect of dosing calcium alone as control variable with

respect to the residual turbidity was tabulated.

Table 4. 7 Result of the Study to Determine the Effect of Calcium Ion on the Turbidity Removal When Calcium was Dosed Only.

Calcium Concentration

(mg/L)

Initial Turbidity

(NTU)

Residual Turbidity

(NTU)

Turbidity Removal Rate (%)

200 80 5.4 93.3

160 80 6.5 91.9

120 80 7.6 90.5

80 80 18 77.5

60 80 74 7.5

92

Table 4.7 states that the calcium could remove the colloids causing

decrease in residual turbidity values. As seen, when the calcium

concentration decreased, the efficiency of turbidity removal

decreased, as expected.

A summarized plot of data is also given in Figure 4.7, highlighting

the region where the best results are achieved.

When the results for 200 mg/L of calcium are examined (Table C.1)

it is seen that for 80 NTU turbidity when calcium dosing first, a wider

region of acceptable turbidity removal was obtained. For alginate

doses between 0.4 mg/L and 20 mg/L (except for the data at 4 mg/L

of alginate) provided sufficient turbidity removal and decreased the

final turbidity down to a level lower than or equal to 1 NTU. In case

of 160 mg/L of calcium, there is a wide range of alginate doses (0.4

to 20 mg/L) providing turbidity values less than 1 NTU, similar to the

case for 200 mg/L of calcium concentration. For the case of 120

mg/L of calcium, however, for a dose range of 0.4 to 6 mg/L, it is

possible to produce water of enough quality with low turbidity (less

than or equal to 1 NTU). Moreover, around the minimum alginate

concentration final calcium concentrations were low (around 40

mg/L). However, when 80 and 60 mg/L of initial calcium

concentrations were dosed, it was not possible to produce low

turbidity values as required by the standard. The lowest turbidities

attainable were 1.2 and 2.3 NTU for 80 and 60 mg/L of initial calcium

concentration, respectively. An addition of conventional filtering unit

besides the processes of coagulation/ flocculation/ settling may

decrease the residual turbidity value to that required in Standard,

especially in case of 80 mg/L calcium.

93

As seen from the Table 4.8, the residual turbidity values had similar

trend for the high concentrations of calcium ions. Lowest alginate

dose that provided the lowest final turbidity was attained at 160 mg/L

of calcium dose. This value was 0.4 mg/L of alginate concentration

and it results in a final turbidity value of 0.5 NTU.

0

1

2

3

4

5

0 1 2Alginate Concentration (mg/L)

Res

idu

al T

urb

idit

y (N

TU

)

200 mg/L of calcium 160 mg/L of calcium 120 mg/L of calcium80 mg/L of calcium 60 mg/L of calcium

Figure 4. 8 Assessment of the Effect of the Change in Calcium Concentration on Final Turbidity (Initial Turbidity: 80 NTU)

Residual turbidity reached its lowest at alginate concentrations in the

range of 0.5 to 1 mg/L as seen in the Figure 4.8 and in Appendix C

in Tables C.1 to C.6. Compared to the others, the three highest

calcium concentrations at 120, 160 and 200 mg/L brought about the

94

highest removal efficiency for turbidity, each have similar final

turbidity around 0.5 NTU for the dose of the alginate concentration

as 0.8 mg/L with respect to minimum turbidity. Depending on the

calcium concentration, the range of the optimum alginate

concentration providing the required turbidity limitations became

narrower while calcium concentration decreased.

Figure 4.9 shows the turbidity removal efficiency of different alginate

concentrations in 80 NTU of initial turbidity water. The results with

respect to the turbidity removal efficiency were drawn in Figure 4.9.

As seen from the Figure 4.9, the most effective removal could be

attained for the 0.8 mg/L of alginate concentration for the high

calcium concentrations (120, 160 and 200 mg/L). This could be

explained by the fact that the high amount of calcium ions decreased

the surface potential of colloids and neutralized the surface of

colloidal, and the colloids becoming unstable tended to settle down

following coagulation and flocculation.

80

90

100

21,6

0,8

0,4

0,320,

20,

120,

04

0,03

20,

02

Alginate Conc. (mg/L)

Perc

ent Turb

idity R

em

oval (

%)

200 mg/L of Ca+2 160 mg/L of Ca+2 120 mg/L of Ca+2

80 mg/L of Ca+2 60 mg/L of Ca+2

Figure 4. 9 Turbidity Removal Efficiency for Different Calcium Dosages (Initial Turbidity: 80 NTU)

95

Calcium removal efficiencies are plotted in Figure 4.10 for different

initial calcium and alginate dosages. As can be seen from this figure,

the removal efficiencies remained lower compared to the set with

150 NTU of turbidity. Also, calcium removal efficiency decreased as

the calcium ion concentration increased.

0

10

20

30

40

50

60

70

80

90

100

21,

600,

800,

400,

320,

200,

120,

040,

032

0,02

0

Alginate Conc. (mg/L)

Per

cen

t C

alci

um

Rem

ova

l (%

)

200 mg/L of Ca+2 160 mg/L of Ca+2 120 mg/L of Ca+280 mg/L of Ca+2 60 mg/L of Ca+2

Figure 4. 10 Calcium Removal Efficiency for Different Calcium Dosages (Initial Turbidity: 80 NTU)

The following Table 4.8 summarizes the optimum alginate doses for

different calcium concentration for the water having 80 NTU of

turbidity. These minimum values of alginate were determined

according to the lowest alginate concentrations rather than the

lowest turbidity. It should be reminded that the optimum values

stated before for the water having 80 NTU were determined

considering the lowest turbidity values for that specific calcium

concentration dosed.

96

Table 4. 8 The Optimum Alginate Concentrations for Each of the Calcium Concentrations Dosed When Initially Calcium Was Dosed, Having 80 NTU of Initial Turbidity

Calcium

Concentration (mg/L)

Optimum Alginate

Concentration (mg/L)

Residual Turbidity

(NTU)

Turbidity Removal Rate (%)

Calcium Ion

Removal Rate (%)

200 0.4 1 98.8 17.24

160 0.4 1 98.8 21.64

120 0.4 0.7 99.1 66.08

80 0.8 1.3 98.4 54.84

60 0.2 2.3 97.1 83.25

Table 4.8 summarizes the data for optimum alginate dosages and it

shows as calcium concentration was decreased, the residual

turbidity was increased. With respect to calcium removal efficiency

as the calcium ion decreases, the removal efficiency increases.

Moreover, it can be said that the usage of alginate has increased the

turbidity removal efficiency when compared the case when calcium

dosed only (Table 4.7). Meaning that alginate be used as coagulant

for medium turbid waters.

4.6 ASSESSMENT OF THE EFFECT OF DOSING ORDER BETWEEN CALCIUM AND ALGINATE ON THE TURBIDITY REMOVAL FOR 80 NTU TURBIDITY SAMPLES Considering the only calcium dosing cause the residual turbidity to

bring the final turbidity levels down to 5.4 to 74 NTU from 80 NTU

(stated in C.1 to C.5). For the 150 NTU turbid waters, it was proved

that the addition of alginate improve the removal of turbidity

depending on the calcium concentration. To verify the effectiveness

of alginate for medium turbid water samples (80 NTU for this case),

97

the dosing order is again reversed and the results are summarized in

Appendix C in Tables C.6 to C.10 and Figure 4.11. Examining these

figure and the tables, it is obvious that dosing alginate first and

calcium next does not work well with 80 NTU samples. Even though

it is possible to reduce the final turbidity to lower than 1 NTU level at

calcium doses of 200, 160 and 120 mg/L. For 200 mg/L the desired

turbidity values could be obtained for wide and lower doses of

alginate. Besides, samples treated with 80 and 60 mg/L of calcium

were unable to produce waters with required turbidity levels. 80 mg/L

calcium treatment left behind 1.2 NTU turbidity, and 60 mg/L calcium

treatment left behind 3.5 NTU turbidity. Therefore, these waters are

not fit for drinking water purposes due to turbidity levels.

0

1

2

3

4

5

0 0.5 1 1.5 2

Alginate Concentration (mg/L)

Res

idu

al T

urb

idit

y (N

TU

)

200 mg/L of Calcium 160 mg/L of Calcium120 mg/L of Calcium 80 mg/L of Calcium

Figure 4. 11 Assessment of the Effect of the Change in Dosing Order on Final Turbidity When Alginate Dosed Initially (Initial Turbidity: 80 NTU)

98

On the other hand, Figure 4.12 and Tables C.6 to C.10 show that the

turbidity removal values does not so much differ for the alginate

doses in the range of 0.2 and 0.4 mg/L and for the calcium

concentration as 80, 120, 160 and 200 mg/L. The removal

percentages remained high, well above 90%, for most of the studied

calcium and alginate doses. Since the alginate addition to the turbid

water samples alone cannot bring any significant turbidity removal,

these results, even though they are for a narrow alginate dose)

would warrant us that the coagulant is still working and the gel

formation is one of the important turbidity removal mechanism.

0102030405060708090

100

Tu

rbid

iy R

emo

val

Eff

icie

ncy

(%

)

21.61.20.40.20.040.02

Alginate Concentration (mg/L)

200 mg/L Calcium 160 mg/L of Calcium 120 mg/L Calcium

80 mg/L Calcium 60 mg/L Calcium

Figure 4. 12 Turbidity Removal Efficiency for Different Calcium Dosages (Initial Turbidity: 80 NTU)

Although the turbidity removal efficiencies are at very high levels, the

calcium removal efficiencies are not at the high levels (Figure 4.13).

99

For high calcium concentrations as 200, 160 and 120 mg/L there

were smaller removal rates, whereas at lower calcium

concentrations there was an increase in the removal of calcium ion.

This means that for medium turbidity waters (having turbidity as 80

NTU) the order of the coagulant dosing really influences the turbidity

removal efficiency.

0

10

20

30

40

50

60

70

Cal

ciu

m R

emo

val

Eff

icie

ncy

(%

)

21.61.20.40.20.040.02

Concentration of Alginate (mg/L)

200 mg/L Calcium 160 mg/L Calcium 120 mg/L Calcium

80 mg/L Calcium 60 mg/L Calcium

Figure 4.13 Calcium Removal Efficiency for Different Calcium Dosages When Alginate was Dosed First (Initial Turbidity: (80

NTU)

Table 4.9 summarizes the data for optimum alginate dosages for

effective turbidity removal, and it shows as calcium concentration

was decreased the residual turbidity was increased. With respect to

calcium removal efficiency as the calcium ion decreases, the

removal efficiency increases.

100

The data stated in Table 4.9 is summarizing the lowest alginate

concentrations for the nearest residual turbidity level of 1 NTU,

When this data is compared with the one at 150 NTU, it is seen that

calcium removal efficiency decreased for 120, 160 mg/L of calcium,

whereas the efficiency of calcium removal increased for 60 mg/L.

Table 4. 9 Minimum Alginate Concentrations for Each of the Calcium Concentrations Dosed, Having 80 NTU of Initial

Turbidity When Alginate Dosed First

The data stated in Table 4.9 show the lowest alginate concentrations

for the required 1 NTU turbidity level can be achieved. When this

data is compared with the one at 150 NTU, it is seen that with the

initial turbidity getting lower, lower residual turbidities are achievable

at lower alginate concentrations. Calcium concentrations at 200, 160

and 120 mg/L all yielded turbidities of decimal fractions of 1 NTU.

However, for 150 NTU systems, lowest alginate doses were able to

produce only turbidities on the order of 1 NTU.

As can be seen in Table 4.9 very low doses of alginate can provide

final turbidity levels less than or equal to 1 NTU for 200, 160 and 120

mg/L calcium ion concentrations. This shows the effectiveness of

Calcium Concentration (mg/L)

Optimum Alginate

Concentration (mg/L)

Residual Turbidity

(NTU)

Turbidity

Removal Rate

(%)

Calcium Ion Removal Rate (%)

200 0.2 0.9 98.9 12.79

160 0.32 1 98.8 15.27

120 0.4 0.7 99.1 15.41

80 2 1.2 98.5 41.20

60 0.12 3.5 95.6 46.40

101

calcium alginate as a coagulant in medium turbidity waters around

80 NTU, of course as mentioned before.

Moreover, considering the Table 4.7, the addition of alginate

improved the system efficiency with respect to turbidity removal,

which is the evidence of the fact that alginate usage for medium

turbid water sample is an alternative way to conventional coagulant

usage for water treatment.

4.7 DETERMINATION OF THE EFFECT OF SODIUM ION AS

COAGULANT AID TO CALCIUM ALGINATE FOR INITIAL TURBIDITY OF 80 NTU

In this part to be able to promote the mechanism of calcium alginate

gel formation, sodium and magnesium ions were added intending to

use them as double layer compressing ions. This part is intentially

conducted with 80 mg/L of calcium concentration since it was a

calcium dose not able to provide an acceptable turbidity value at 80

NTU samples. So sodium ions were expected to improve the

efficiency of the turbidity removal. Therefore, in this part first sodium

or magnesium is added, followed by calcium ions, which is then

followed by alginate addition. The purpose here is to use the first

added ion (sodium or magnesium) for charge neutralization and

double layer compression, so that all of the calcium ions added can

take part in gel formation with alginate and cause removal of colloids

while settling as sweeping flocs.

Results of sodium addition into 80 NTU samples with 80 mg/L of

calcium addition are given in Figure 4.14.

102

In Figure 4.14 it is observable that the addition of sodium ions might

enhance the removal of turbidity depending on the initial calcium and

alginate concentration. In other words, as the calcium concentration

is increased the residual turbidity is decreased due to the use of

sodium ions especially at high calcium concentration. It is clear that

for the initial calcium concentration of 120 mg/L the addition of

sodium ions improved the treatment for alginate concentrations

greater than 1 mg/L. For the lower concentrations of alginate (0.02 to

0.4 mg/L) the treatment was more efficient without using sodium

ions. Regarding to 80 mg/L of calcium dose, the concentration of

alginate used determines whether sodium ions to be used or not.

Because, there were fluctuations in the data and it was hard to

decide whether sodium helped the process or not.

0

1

2

3

4

5

0 0.5 1 1.5 2

Alginate Concentration (mg/L)

Res

idu

al T

urb

idit

y (N

TU

)

40 mg/L of Calcium +4 meq/L of Sodium.80 mg/L of Calcium + 4 meq/L of Sodium120 mg/L of Calcium + 4 meq/L of Sodium.60 mg/L of Calcium 80 mg/L of Calcium Only120 mg/L of Calcium Only

Figure 4. 14 Assessment of the Effect of Calcium Concentration Change on Residual Turbidity for the Fixed Turbidity (80 NTU)

and Fixed Sodium Concentration (4 meq/L).

103

As the calcium concentration was decreased to 60 mg/L the removal

efficiency of turbidity was also decreased independent of the usage

of sodium ions as a coagulant aid. The sodium ion use made the

process even worse.

Later, the effect of change in sodium ion concentration was also

analyzed in the range of 1, 2, 4, 5 and 7 meq/L. The data are

summarized in Figure 4.15.

Figure 4.15 shows the sodium ions in fact are not improving the

process except for 4 meq/L dose. Therefore, this effect is regarded

as insignificant, and the sodium ions were considered not helping

with the coagulation process.

0

1

2

3

4

5

6

7

0 0,5 1 1,5 2

Alginate Concentration (mg/L)

Res

idu

al T

urb

idit

y (N

TU

)

0 meq/L of Sodium 1 meq/L of Sodium 2 meq/L of Sodium4 meq/L of Sodium 5 meq/Lof Sodium 7 meq/L of Sodium

Figure 4. 15 Assessment of Sodium Ions Effect on Residual Turbidity as Coagulant Aid to Calcium Alginate (for 80 mg/L of Calcium and 80 NTU of Initial Turbidity)

104

4.8 DETERMINATION OF THE EFFECT OF MAGNESIUM ION AS COAGULANT AID TO CALCIUM ALGINATE FOR INITIAL

TURBIDITY OF 80 NTU

It was maintained that to meet the required turbidity standards for

drinking purposes was very difficult for the lower calcium

concentrations and lower turbid water samples. Therefore, in order

to enhance the coagulation the usage of magnesium ion as a

coagulant aid to calcium alginate was tried. The results obtained

were stated in Figure 4.16.

0

0,5

1

1,5

2

2,5

3

3,5

4

4,5

5

0 0,5 1 1,5 2 2,5

Alginate Concentration (mg/L)

Resi

du

al T

urb

idit

y (

NT

U)

0 meq/L of Magnesium 1 meq/L of magnesium

4 meq/L of magnesium

Figure 4.16 Assessment of the Effect of Magnesium Ion as Coagulant Aid for Fixed Calcium Concentration and Fixed Initial

Turbidity

105

Figure 4.16 shows that magnesium ions do not help with the process

to a great extent. Lowest turbidity values attainable were still at zero

magnesium doses, i.e. when it is absent from the system. This

finding is very important since both calcium and magnesium are

divalent cations. Results simply highlight the effectiveness of calcium

working with alginate indicating that adding magnesium into the

system will only make the process to deteriorate.

The results were tabulated Tables C.11 and Table C.12 in Appendix

C.

4.9 DETERMINATION OF THE EFFECT OF SETTLING TIME ON RESIDUAL TURBIDITY (80 NTU)

Results at 80 NTU showed high turbidity removal was achieved at a

high percentage. However, achievement of 1 NTU level occurred

only within a narrow alginate range and final turbidities could not be

lowered much lower than 1 NTU level. Knowing that the jar test

employs a 30 minutes settling and a real water treatment plant

makes the flocs settle for 1 to 2 hours at least, effect of settling time

is tested to observe the changes in the final turbidity.

This set was achieved at 80 NTU of initial turbidity with addition of 80

mg/L of calcium ions first. The residual turbidity and final calcium

concentrations were measured at the time of 30, 60, 90 and 120

minutes. The results are given in Figure 4.17.

106

0

0.5

1

1.5

2

2.5

3

0 0.5 1 1.5 2 2.5

Alginate Concentration (mg/L)

Re

sid

ua

l Tu

rbid

ity

(N

TU

)

at 30 min at 60 min at 90 min at 120 min

Figure 4. 17 Effect of Settling Time on Final Turbidity

As illustrated in the Figure 4.17 increase in the settling time resulted

in the increase in the turbidity removal efficiency. 30 minute settling

time created more the residual turbidity value than that created by 60

minute settling time for the same alginate concentration. So as the

settling time increasing from 30 to 90 minute, the turbidity removal

efficiency increased.

When settlement was conducted for 30 minutes only, the required 1

NTU level was only achievable at 1.6 mg/L alginate concentration.

However, with the employment of settling time of 1 hour, equal to or

less than 1 NTU level was achievable for alginate doses of 0.4 to 2

mg/L. for 90 minutes, and 120 minutes settling time all the doses

tested ranging from 0.2 mg/L to 2 mg/L alginate gave all less than 1

NTU turbidity levels. However, it should be stated that settling times

of 90 minutes and 120 minutes caused the same values of residual

turbidities, from which it could be concluded that additional 30

107

minutes after 90 minute settling time does not help the colloids to

settle down since only the more stable ones insist on staying

suspended.

4.10 DETERMINATION OF THE EFFECT OF SETTLING TIME AND THE ORDER CHANGE ON RESIDUAL TURBIDITY (80 NTU) In previous experiment, in which the impact of settling time was

analyzed, calcium was dosed first, and then alginate was added. In

this section, the coagulant dosing order was changed as alginate

was dosed first and then calcium was introduced next. The results

are presented in Figure 4.18.

0

1

2

3

4

5

0 0.5 1 1.5

Alginate Concentration (mg/L)

Res

idu

al T

urb

idit

y (N

TU

)

at 30 min at 60 min at 90 min at 120 min

Figure 4. 18 Assessment of The Effect of Settling Time and Dosing Order Change on Residual Turbidity

108

Figure 4.18 indicates that there is still decrease in the residual

turbidity values as the time is passed, even though adding alginate

first was not efficient as the case of calcium addition first. Because,

when the alginate was dosed initially the negatively charged surface

of colloids became much more negative since alginate used was an

anionic organic polymer. This increase in electronegativity resulted

in the increase of zeta potential to be lowered by calcium ions.

However, calcium ions could not be effective for this reduction since

its concentration was low (80 mg/L). Therefore, coagulation was

expected not to be influential in the case of low calcium dosed and

low turbidity waters.

In the case were alginate was dosed first, prolonged settling time

improved the final turbidity for the whole alginate concentration

range studied. However, for the whole concentration range of

alginate, it was not possible to produce water with less than 1 NTU

turbidity. Alginate dose at 0.4 mg/L provided sufficient treatment for

60, 90 and 120 minutes settling time. When the samples were

settled for 120 minutes, the alginate dose of 0.2 to 0.4 mg/L seemed

to provide the required turbidity levels.

4.11 EVALUATION OF ALGINATE AS A POTENTIAL COAGULANT FOR LOW TURBIDITY (10 NTU) WATER SAMPLES Tests were also run for water samples at 10 NTU turbidity in order to

evaluate the usability of calcium alginate as a coagulant in low

turbidity water samples.

To understand its effect, only calcium was dosed as control variable,

and the results were shown in Table 4.10.

109

Table 4. 10 Result of the Study to Determine the Effect of Calcium Ion on the Turbidity Removal When Calcium was Dosed Only.

Calcium Concentration

(mg/L)

Initial Turbidity

(NTU)

Residual Turbidity

(NTU)

Turbidity Removal Rate (%)

80 10 5 50

60 10 6 40

30 10 9.1 9

As seen from the Table 4.10 calcium alone has not much effect on

the turbidity removal when compared with the cases for 150 NTU

and 80 NTU, which means that as the initial turbidity decreased the

effect of calcium on the turbidity removal also decreased.

To represent low turbidity water samples 10 NTU turbidity sample

was prepared by diluting from the stock solution of clay. 80, 60 and

30 mg/L doses of calcium were used for 10 NTU turbidity water

samples. Since the addition of alginate first did not work well to meet

the required turbidity values in the previous work, the change in

dosing order was not studied for 10 NTU water sample. In all cases

calcium was dosed first. In the previous studies it was observed that

the change in settling time could improve the turbidity removal.

Therefore, for each set of this part, settling time effect were also

investigated. The results obtained are presented in Figures 4.19,

and Appendix D offered in the tables Table D.1 to D.3.

Figure 4.19 states that for calcium ions was dosed to 10 NTU of

water sample by differing the alginate concentration in the range of

0.02 to 1.6 mg/L, 0.04 mg/L of alginate concentration was the

110

optimum dose via which the minimum final turbidities were achieved

at the time of settling of 30, 60, 90 and 120 minutes could be

obtained as 3.9, 2.1, 1.9 and 1.3 NTU, respectively.

0

1

2

3

4

5

6

7

8

0 0.5 1 1.5 2

Alginate Concentration (mg/L)

Fin

al T

urb

idit

y (N

TU

)

at 30 min at 60 min at 90 min at 120 min

Figure 4. 19 Final Turbidity as a function of alginate dose for 10 NTU turbidity samples

The peak in Figure 4.19 may be resulted from many possible

situations. For example, at this dosage charge reversal could be an

explanation. Or experimental errors might be experienced. Figure

4.19 also states that the increase in settling time caused a decrease

in final value of turbidity. It was unfortunate that, although 120

minute was provided, the residual turbidity values could not reach

the necessary value. Additional process like filtration may help to

reach the Standard value. With respect to the turbidity removal

efficiency, it should be remembered that for low turbidity waters, the

111

colloidal material are generally stable or have very slow settling

velocity. The maximum turbidity removal efficiency was obtained at

the alginate concentration of 0.04 mg/L for 80 mg/L of calcium.

Parallely, the removal of calcium ions was low, generally at around

1.3%.

Similar results for 60 mg/L calcium of 10 NTU water sample were

observed while changing the alginate concentration and settling

time. However, considering the 30 mg/L, the results of which are

given in Tables D.5 and D.6 in Appendix D was different than the

other calcium concentrations. The dependency of settling time for 30

mg/L of calcium concentration was reduced after 30 minute

detention time. To get better understanding of the dependency of

low turbidity waters on the calcium solution was drawn to Figure

4.20.

0

2

4

6

8

10

12

0 0,5 1 1,5 2

Alginate Concentration (mg/L)

Res

idu

al T

urb

idit

y (N

TU

)

80 mg/L of calcium 60 mg/L of calcium 30 mg/L of calcium

Figure 4.20 The Effect of the Change in Calcium Concentrations on Residual Turbidity for Low Turbidity Water (10 NTU)

112

Figure 4.20 consisted of turbidity results from three calcium

concentrations as 80, 60 and 30 mg/L for the alginate concentration

range 0.02 to 1.6 mg/L. As seen as the calcium concentration

decreased its effectiveness on turbidity removal decreased, resulting

in high residual turbidity values. Te final turbidity values of 80 and 60

mg/L of calcium were close to each other as 3.9 and 4.1 NTU,

respectively. As calcium concentration decreases the effectiveness

of alginate with this concentration of calcium was getting very

smaller. Depending on the alginate concentration turbidity removal

rate changed. The lower concentrations of alginate resulted in better

turbidity removal. The graph also stated that the most effective

alginate concentration was 0.04 for all of calcium concentrations

dosed to 10 NTU.

Referring to Tables D.1 to D.6 in Appendix D, the calcium removal

efficiency was very poor even with the increment of settling time and

the increase in alginate imposed. This set was like a proof of our

result of the experimentation: for the lower turbidity sample, calcium

alginate does not work, properly.

4.12 EVALUATION OF THE EFFECT OF MAGNESSIUM IONS AS

COAGULANT AID ON THE PERFORMANCE OF CALCIUM ALGINATE FOR LOW TURBIDITY WATERS

In section 4.8, effectiveness of magnesium ions as coagulant aid to

calcium alginate is investigated. And it was found that magnesium

ions slightly decreased the value of residual turbidity.

113

For low turbidity water as 10 NTU, it was really difficult to maintain

the required final turbidity values of Standards. In this section the

validity of the use magnesium ions for 10 NTU of turbid water is

analyzed by changing the magnesium concentration as 1, 2 and 4

meq/L since the treatment efficiency of alginate with 30 mg/L of

calcium was not very good. The results are tabulated in Appendix E

in Tables E.1 to E.6. The results are summarized in Figure 4.21,

which declares the results of the experiments for 1, 2 and 4 meq/L of

magnesium ion concentration. Settling time was another variable of

this section of the study. By increasing settling time, residual

turbidity values were slightly decreased. Only in the case at which

1meq/L of magnesium dosed with 0.04 mg/L of alginate and 30 mg/L

of calcium concentrations were dosed residual turbidity value was as

1.3 NTU, nearest to 1 NTU, at the end of 120 minute settling time.

For the other cases we saw the increment in the residual turbidity

value, which may be a result of charge reversal.

4

5

6

7

8

9

10

11

12

0 0,5 1 1,5 2

Alginate Concentration (mg/L)

Res

idu

al T

urb

idit

y (N

TU

)

1 meq/L of magnesium+30 mg/L of calcium

2 meq/L of magnesium+30 mg/L of calcium

4 meq/L of magnesium+30 mg/L of calcium

30 mg/L of calcium

Figure 4. 21 Assessment of Magnesium Ions as Coagulant Aid to Calcium Alginate

114

Figure 4.21 states that comparing with the case in which 30 mg/L of

calcium was dosed; the addition of magnesium ions slightly

influenced the residual turbidity value. This effect was very clear

when 4 meq/L of magnesium ions was used for the alginate

concentration range of 0.02 to 0.8 mg/L. However, the residual

turbidity values did not match with the required values of related

Standard. Therefore, higher magnesium concentrations were not

tested.

4.13 EVALUATION OF THE EFFECT OF TURBIDITY ON THE

PERFORMANCE OF CALCIUM ALGINATE

When we examine the effect of initial turbidity with respect to

turbidity removals and final turbidities of water sample we see that

low turbidity levels such as 10 NTU unfortunately does not give

satisfactory results. At this turbidity level and at the studied calcium

and alginate doses, it was not possible to produce water with final

turbidity less than or equal to 1 NTU. On the other hand, calcium

alginate proved to be a very effective coagulant for higher turbidity

waters such as 80 NTU and 150 NTU. When the system is

examined with reference to Figure 4.21 A, B and C, it is seen that

calcium alginate is more effective at 80 NTU turbidity water than 150

NTU sample water. This response is in fact calcium dose dependent.

Even though it is not possible to see a sharp difference at 160 mg/L

calcium dosed waters between the two turbidity waters, in case of

200 and 120 mg/L of calcium alginate is more effective to produce

lower turbidities at 80 NTU turbidity sample.

115

200 mg/L of Calcium

0

1

2

3

0 2 4 6 8 10 12

Alginate Concentration (mg/L)

Fin

al T

urb

idit

y (N

TU

)

150 NTU 80 NTU

(A)

160 mg/L of Calcium

00.20.40.60.8

11.2

0 2 4 6 8 10 12

Alginate Concentration (mg/L)

Fin

al T

urb

idit

y (N

TU

)

150 NTU 80 NTU

(B)

120 mg/L of Calcium

0

1

2

3

4

0 1 2 3 4 5 6 7Alginate Concentration (mg/L)

Fin

al T

urb

idit

y (N

TU

)

150 NTU 80 NTU

(C)

Figure 4. 22 Effect of the Performance of Calcium Alginate

116

Turbidity creating particles possibly act as nuclei for the attachment of

calcium alginate gel. Normally higher the amount of nuclei a higher

effectiveness of the coagulant may be expected. In this study, since the

same alginate and calcium dosages are used, and Figure 4.22 A, B,

and C are plotted for this case we expect same amount of gel formation

at each point on the graph.

Then this gel settled down bringing the turbidity causing particles

together with it. Since the initial turbidity at 150 NTU is almost twice as

high as 80 NTU, same amount gel was unable bring all the particles in

the case of 150 NTU. This possibly caused a high final turbidities in the

150 NTU sample compared to 80 NTU sample.

4.13 EVALUATION OF ALGINATE AS A POTENTIAL COAGULANT

FOR WATER SAMPLES TAKEN FROM IVEDIK TREATMENT

PLANT, ANKARA

After analyzing the water samples prepared in the laboratory, it was

necessary to investigate calcium alginate as potential coagulant for a

real water sample. Water sample is coming from the dams of

Kurtboğazı and Çamlıdere to IWTP. The sample was collected from the

inlet point of IWTP. The previous analyses done by IWTP provided by

the plant personnel gave the information about the characteristic of

water quality at the inlet. Water samples taken from IWTP had the

initial pH around 7.2, initial turbidity around 6.5 and the background

calcium concentration around 23 mg/L at inlet point. The additional

information about the water characteristic of the water taken from the

inlet point of IWTP is stated in Appendix F.

117

The effect of the dosing of calcium alone on the residual turbidity of raw

water was investigated first. The Table 4.11 was obtained.

Table 4. 11 Result of the Study to Determine the Effect of Calcium Ion on the Turbidity Removal When Calcium was Dosed Only.

Calcium Concentration

(mg/L)

Initial Turbidity

(NTU)

Residual Turbidity

(NTU)

Turbidity Removal Rate (%)

120 6.4 5.4 15.6

80 6.4 5.4 15.6

60 6.5 5 23.1

30 6.5 5.4 16.2

15 6.5 5.6 13.8

In Table 4.11 it is stated that calcium dosing alone has slight effect on

turbidity removal efficiency.

Since its turbidity was very low, 120 mg/L of calcium concentration was

selected as the starting point for this set of experiment. All the data

obtained are collected in Appendix G and summarized in Figures 4.23,

4.24 and 4.25.

118

Results of Raw Water

3.0

4.0

5.0

6.0

0 0.5 1 1.5 2

Alginate Concentration (mg/L)

Res

idu

al T

urb

idit

y (N

TU

)

15 mg/L of Calcium 30 mg/L of Calcium60 mg/L of Calcium 80 mg/L of Calcium120 mg/L of Calcium

Figure 4. 23 Evaluation of calcium alginate as potential coagulant for the water samples taken from IWTP.

As stated in Figure 4.23, 15 mg/L of calcium concentration gave best

results, which still could not reach the necessary turbidity value. The

results show that the addition of alginate contributed to the turbidity

removal efficiency; therefore, alginate could be a good alternative as

coagulant since it has organic nature.

In Figure 4.24 the results were plotted with respect to settling time to

see if there is any effect.

119

2

3

4

5

6

7

0 20 40 60 80 100 120 140

Settling Time (minute)

Res

idu

al T

urb

idit

y (N

TU

)

120 mg/L of Calcium Dosed Only 0.02 mg/L of Alginate0.04 mg/L of Alginate 0.2 mg/L of Alginate0.4 mg/L of Alginate 0.8 mg/L of Alginate1.6 mg/L of Alginate 2 mg/L of Alginate4 mg/L of Alginate 6 mg/L of Alginate

Figure 4. 24 Evaluation of calcium alginate as potential coagulant for the water samples taken from IWTP.

As seen from Figure 4.24, the usage of 120 mg/L of calcium alone was

not effective to get the required turbidity limits alone. The usage of

alginate enhanced the removal of turbidity, thus reduce the residual

turbidity values when alginate was dosed between 0.02and 6 mg/L.

Particularly, the sample that received 4 mg/L of alginate was the most

effective in decreasing the turbidity to about 3 NTU levels. It was

unfortunate that no residual turbidity values could meet the

requirements even though settling time was prolonged up to 120

minutes.

The turbidity removal rates were plotted in Figure 4.25 depending both

on the settling time and also the alginate concentration. It was

concluded that as the settling time increased, settling of some colloidal

particles could be achieved. Thus, settling time improved the turbidity

removal efficiency in general especially in lower alginate dosed

samples, although it was not still sufficient.

120

0

10

20

30

40

50

60T

urb

idit

y R

emo

val

Eff

icie

ncy

(%

)

0.02 0.2 0.8 2 6

Alginate Concentration (mg/L)

Turbidity Removal Rate at 30 min. Turbidity Removal Rate at 60 min.

Turbidity Removal Rate at 90 min. Turbidity Removal Rate at 120 min

Figure 4. 25 Evaluation of calcium alginate as potential coagulant for IWTP with respect to the turbidity removal efficiency at 120 mg/L.

In Figure 4.26, the calcium removal rate was drawn with respect to the

alginate concentration and settling time. It could be said that nearly all

of the removal of calcium ions were achieved at the end of 30 minutes

settling time. As the settling time increased the removal of calcium

decreased, which was a proof of the resuspension of calcium ions

when 120 mg/L of calcium dosed to different alginate concentration.

121

0102030405060708090

Cal

ciu

m R

emo

val

Eff

icie

ncy

(%

)

0.02 0.2 0.8 2 6

Alginate Concentration (mg/L)

Calcium Removal Rate at 30 min. Calcium Removal Rate at 60 min.

Calcium Removal Rate at 90 min. Calcium Removal Rate at 120 min

Figure 4. 26 Evaluation of calcium alginate as potential coagulant for the water sample from IWTP with respect to the calcium removal efficiency.

To further determine the best removal conditions and optimum doses

for alginate and calcium, it was considered to analyze the water

samples with 80, 60, 30 and 15 mg/L of calcium concentrations for the

alginate concentration range of 0.02 to 6mg/L. The results are given in

Appendix F. One could determine that the turbidity change with respect

to the alginate concentration did not show much variations with these

calcium doses, either. The lowest turbidity values that could be

obtained was 3 NTU for the alginate concentration of 2 mg/L with 80

mg/L of calcium ions, 3 NTU for the alginate concentration of 2 mg/L

with 120 mg/L of calcium ions, 4 NTU for the alginate concentrations of

0. 2 to 0.4 with 60 mg/L of calcium ions, 4 NTU for the alginate

concentration from 0.04 mg/L with 30 mg/L of calcium ions, and 3.7

NTU for the alginate concentration of 0.04 mg/L with 15 mg/L of

calcium ions at the end of 30 minute settling time. Although the

colloidal particles have more chance to settle down when settling time

122

prolonged to 60, 90 and 120 minutes later on, the results of this part of

the experiment could not meet what is required in TSS 266.

4.14 WORKING MECHANISM OF CALCIUM ALGINATE AS A COAGULANT FOR WATER TREATMENT

it is believed that more than one mechanism of action was valid in the

case of calcium alginate to work as a coagulant. The first mechanism of

turbidity removal was by surface charge neutralization of the colloids by

calcium ions which was able to remove a significant amount of the

turbidity creating particles without the addition of alginate. Once the

surface charge is neutralize by stirring action of the flocculator,

particles were able to get together and settle out. This was especially

more effective in high turbidity samples. However, it was obvious that

calcium by itself can not create water of quality to meet the required

limit value for residual turbidity. To decrease the residual value of

turbidity to the acceptable limits the usage of alginate is necessary.

Regardless of the mechanisms involved, there is strong evidence that

divalent metal ions are necessary for anionic polymers to flocculate

negatively charged colloids. When the ionic polymers are used to

destabilize negative colloids, theory and observations indicate that

divalent metal ions must be present either naturally or by direct addition

(Weber, 1982). Our results are in parallel with this statement. Only

alginate going through the coagulation/ flocculation process are not

able to produce required turbidity removals. As soon as the divalent

cation addition is done, coagulation is achieved. Therefore, the major

mechanisms of flocculation by calcium alginate are surface charge

neutralization and bridging. The charge neutralization occurs since

charge of calcium is opposite in sign to that of the suspended particles

123

as well as that of alginate. After alginate is added the major mechanism

of flocculation is the polymer bridging. In polymer bridging, the high

molecular mass polymer chains are adsorbed onto the particle surface

and form bridges between adjacent particles. Besides, it is believed

that the main mechanism of coagulation is by the calcium/ alginate gel

formation around the colloidal particles. The effectiveness of

coagulation is a strong function of the divalent cation concentration.

Whenever alginate was dosed first, alginate addition was expected to

result in an increase in the electronegativity of water sample. Only high

concentration of calcium ions could be successful to decrease zeta

potential, and the double layer repulsive energy to produce effective

coagulation. That is why low calcium concentrations could not be able

to overcome the negative surface charge efficiently at low doses. The

GG blocks of alginate is of unique structure that has the carboxylic

groups, having sizes to which calcium ions can fit in. When calcium

ions bond to the carboxylic groups, gel formation occurs like egg box

model. This egg-box model cause to remove the suspended materials

by mechanism, namely sweep flocs.

Of course, as discussed earlier, the initial turbidity is very important to

provide condensation nuclei for the gel formed. Particles also add

weight to the system. Since alginate is not a very high molecular weight

polymer, its own weight is not enough to create highly settleable flocs

at low turbidity values. Whereas, when there is enough particles that

can create weight and that the gel can attach effectiveness of the

system increases.

124

4.15 COMPARISON OF POLYELECTROLYTE USED IN IVEDIK TREATMENT PLANT WITH ALGINATE.

In IWTP, 0.05 mg/L of polyelectrolyte is used with 30 mg/L of alum to

treat the water. To determine the interaction between the

polyelectrolyte and calcium and to compare the effectiveness of

calcium alginate with that of the polyelectrolyte, the calcium as 120, 80,

60, 30 and 15 mg/L with 0.05 mg/L of polyelectrolyte were dosed. The

results are shown in Figure 4.27.

It could be stated that the polyelectrolyte acts with calcium, and as the

calcium concentration increased, the turbidity removal efficiency

increased also. However, even for 120 mg/L of calcium concentration

the residual turbidity posed problem according to drinking water

standards.

125

2.5

3

3.5

4

4.5

5

5.5

0 30 60 90 120 150

Settling Time (minute)

Re

sid

ua

l Tu

rbid

ity

(N

TU

)

Only 0.05 mg/L of Polyelectrolyte dosed0.05 mg/L of Polyelectrolyte + 15 mg/L of Calcium0.05 mg/L of Polyelectrolyte + 30 mg/L of Calcium0.05 mg/L of Polyelectrolyte + 60 mg/L of Calcium0.05 mg/L of Polyelectrolyte + 80 mg/L of Calcium0.05 mg/L of Polyelectrolyte +120 mg/L of Calcium

Figure 4. 27 Assessment of Polyelectrolyte and Calcium ion interactions with respect to residual turbidity

To get better understanding, 80 NTU of clay suspension was prepared

by diluting the stock solution. Polyelectrolyte was dosed in the range of

0.02 to 1.6 mg/L in order to compare it with alginate results. 80mg/L of

calcium was dosed along with each concentration of polyelectrolyte.

The results are given in Figures 4.28 and 4.29.

In Figure 4.28 it is obvious that for the same dosage, same initial

turbidity and the same calcium concentration as 80 mg/L, alginate was

performing much better to result in lower residual turbidity values. For

higher concentration of both polymers, the residual turbidity values

were very close to each other and the limit values. However, at lower

126

polymer doses, the performance of alginate was far better than that of

the polyelectrolyte.

0,00

2,00

4,00

6,00

8,00

10,00

12,00

14,00

0 0,2 0,4 0,6 0,8 1

Concentration of Coagulant (mg/L)

Res

idu

al T

urb

idit

y (N

TU

)

Treatment with Polyelectrolyte Treatment with Alginate

Figure 4. 28 Comparison of Polyelectrolyte and Alginate within the case of 80 mg/L of Calcium Dosed and 80 NTU of Initial Turbidity

In addition, the usage of alginate had one more advantage to

polyelectrolyte used in IWTP, which was the lower residual calcium

concentrations it caused. This finding emphasizes the specific affinity

of calcium and alginate towards each other. It is believed that with this

specific affinity that leads to gel formation reaction calcium alginate

becomes an effective coagulant, more effective than many anionic

synthetic polyelectrolytes available in the market.

127

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

0 0.2 0.4 0.6 0.8 1

Concentration of Coagulant (mg/L)

Res

idu

al T

urb

idit

y (N

TU

)

Treatment with Polyelectrolyte Treatment with Alginate

Figure 4. 29 Comparison of Polyelectrolyte and Alginate within the case of 80 mg/L of Calcium Dosed and 80 NTU of Initial Turbidity

4.16 COST ANALYSIS

Cost is an important parameter when choosing the processes and the

substances to be used in them environmental engineering. For all the

systems where decisions are to be done among different processes a

cost benefit analysis should be done. These analyses reveal which

process and what substances are more feasible for that particular

system. For this reason, a brief cost analysis based on chemical costs

is done between alum- polyelectrolyte system, which is used in IWTP,

and calcium-alginate system.

128

In order to compare the cost of chemicals between alum-polyelectrolyte

system and calcium-alginate system usage the alum, polyelectrolyte,

calcium and alginate concentrations are selected as 30, 0.05, 120 and

0.4 mg/L, respectively. The values for alum and polyelectrolyte are the

concentrations being used in IWTP for all initial turbidity values in the

range of 5 to 100 NTU. Whereas, the concentration values of calcium

and alginate are determined as a result of the 80 NTU of initial turbidity

experiment, which is considered as the most efficient case. The Table

4.12 gives the unit prices of these chemicals. The prices stated in

Table 4.12 are taken from the firms, namely Türk Henkel and Interlab.

Table 4. 12 Unit Prices of the Chemicals

Chemical Unit Price (YTL/kg)

Amount Required

(g/m3)

Total Price (YTL/m3)

Alum sulfate 0.37 0.03 11.1×10-3

Polyelectrolyte 2.00 1×10-4 2×10-4

Calcium chloride 0.72 0.12 8.64×10-2

Alginate 2.61 4×10-4 10.44×10-4

Table 4.13 summarizes the total chemical costs of both systems to

meet the desired residual turbidity.

Table 4. 13 Total Chemical Costs

Total cost of alum-polyelectrolyte system

11.3×10-3 YTL/m3

Total cost of calcium-alginate system 87.44×10-3 YTL/m3

129

As it can be seen that chemical cost of both of the systems are

comparable, which proves that calcium-alginate system can be used as

an alternative coagulant. Moreover, it should be stated that these cost

values are calculated by considering only the chemical costs but not

operational costs and costs associated with further treatment of sludge

originating from coagulation/flocculation process. Although, operational

costs of both of the systems are close to each other, cost of sludge

handling is expected to create huge differences. Because, it is known

in general that the sludge originating from alum-polyelectrolyte system

is in much higher quantities and very difficult to be treated. However,

the calcium-alginate sludge is expected to be in much smaller

quantities handled easier to decrease the treatment cost.

130

CHAPTER 5

CONCLUSION

• The study showed that there is strong interaction between

alginate and calcium ions, due to which calcium alginate can be

thought as a potent coagulant. Moreover, it can be stated that

the efficiency of coagulation and flocculation via alginate is

highly dependent on the calcium concentration. There is an

optimum region for alginate, where neither higher nor lower

doses work.

• It is observed that the coagulation by calcium alginate does not

alter the pH of the water.

• It is concluded that at the doses calcium alginate is used as a

coagulant, it does not have a significant effect on the TOC of the

water.

• For high turbidity waters, the calcium- alginate system is more

effective than for low turbidity waters. Moreover, as the initial

turbidity decreases the required concentration of alginate and

calcium increases.

• For water samples having 150 NTU of initial turbidity with

calcium concentrations of 200 mg/L, 160 mg/L, 120 mg/L and 80

mg/L it is possible to decrease turbidity below or near 1 NTU

using varying concentrations of alginate. Considering the results

of 150 NTU turbid water, the turbidity removal efficiencies

131

decrease as the dose of both calcium and alginate decrease.

With respect to the turbidity removal efficiencies, the efficient

removal could be attained for the calcium concentrations greater

than 60 mg/L for the alginate concentrations in the range of 0.2

to 40 mg/L. As the concentration of calcium decreased, the

optimum alginate dosages decreased with the exception of 160

mg/L of calcium sample. Moreover, while applying typical jar test

procedure, it was easy to observe the gel formation and large

flocs as soon as alginate was dosed. The optimum calcşum

dose range is believed to be within 120 and 160 mg/L due to

efficient gel formation reaction observed.

• When dosing order of calcium and alginate was changed, for

highly turbid waters, it was easy to observe bigger floc formation

with a decreasing size as the alginate concentration was

decreased. Moreover, it was observed that for the case in which

alginate dosed first, the calcium removal efficiency increased.

• For 80 NTU initial turbidity, when the results for 200, 160 and

120 mg/L of calcium are examined it is seen that a wider region

of acceptable turbidity removal was obtained when the calcium

was dosed first. Alginate doses between 0.4 mg/L and 20 mg/L

(except for the data at 4 mg/L of alginate for 200 mg/L calcium

concentration) have provided sufficient turbidity removal and

decreased the final turbidity down to a level lower than or equal

to 1 NTU for calcium concentrations greater than 80 mg/L. As

calcium concentration was decreased, the residual turbidity was

increased. With respect to calcium removal efficiency as the

calcium ion decreases, the removal efficiency increases.

132

• It is unfortunate that for low turbidity water samples (10 NTU and

sample from IWTP) calcium alginate system does not cause an

effective turbidity removal.

• When alginate was dosed first, prolonged settling time improved

the final turbidity for the whole alginate concentration range

studied.

• Addition of monovalent and divalent cations showed fluctuating

results and it was not easy to decide whether they helped the

process or not.

• For 10 NTU samples, for the situation in which 80 mg/L of

calcium ions was dosed to at different alginate concentrations in

the range of 0.02 to 1.6 mg/L, turbidity removal rate changes

depending on the alginate concentration. It was observed that

low concentrations of alginate resulted in better turbidity

removal. The gel formedsettled down bringing the turbidity

causing particles together with it.

• It is observed that use of calcium acts as a very important agent

and only by itself it is lable to remove a great amount of turbidity.

However, by itself, calcium cannot decrease the turbidity to the

limit values required in Turkish or European Drinking Water

Standards. This provides evidence for the contribution of

alginate to be used as a coagulant when used with calcium ions,

and demonstrates its necessity to decrease the turbidity from

around 5 NTU to less than 1 NTU.

133

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140

APPENDIX A

Table A. 1 Parameters And Parametric Values Adapted from Official Journal of European Communities

Country Parameter Parametric

Value

Note

Total

organic

carbon

(TOC)

No abnormal

change

This parameter need

not to be measured for

supplies of less than

10000 m3 a day

European

Countries

Turbidity Acceptable to

consumers and No

abnormal change

In case of surface water

treatment, Member

States should strive for

a parametric value not

exceeding 1 NTU in the

water ex treatment

works.

141

Table A. 2 Parameters And Parametric Values Adapted from Turkish Drinking Water Standard (TST 266)

Parametric Value

Class 1 1

&

Class 2 2

Class 2 Countr

y Parameter

Type 1 3 Type 2 4

Unit Note

Total organic

carbon (TOC) No abnormal change

Turkey

Turbidity 5 5 NTU

In case of

surface water

treatment,

Member States

should strive for

a parametric

value not

exceeding 1 NTU

in the water ex

treatment works.

(1) Spring Water

(2) Water other than that for human consumption purposes

(3) Treated Spring Water

(4) Drinking and Potable Water

142

APPENDIX B (150 NTU)

Table B. 1 Effect of Different Alginate Concentrations on Turbidity Removal for 200 mg/L of Calcium

CALCIUM WAS DOSED FIRST, THEN ALGINATE WAS ADDED

INITIAL TURBIDITY

(NTU)

INITIAL CALCIUM CONCENTRATION

(mg/L)

INITIAL ALGINATE

CONCENTRATION (mg/L)

FINAL TURBIDITY

(NTU)

FINAL CALCIUM CONCENTRATION

(mg/L)

TURBIDITY REMOVAL

(%)

CALCIUM REMOVAL

(%)

150 200 40 3 173.03 98.0 13.5

150 200 20 2.3 167.12 98.5 16.4

150 200 10 1.6 161.46 98.9 19.3

150 200 8 1.5 192.52 99.0 3.7

150 200 6 1.5 150.64 99.0 24.7

150 200 4 1.1 134.90 99.3 32.5

150 200 2 1.5 126.84 99.0 36.6

150 200 1.60 1.8 144.17 98.8 27.9

150 200 0.80 2 93.92 98.7 53.0

150 200 0.40 2.8 98.23 98.1 50.9

150 200 0.32 3.5 91.32 97.7 54.3

150 200 0.20 4.8 174.83 96.8 12.6

Ca

CO

NC

EN

TR

AT

ION

200

mg

/L

150 200 0 5.3 nm 96.5 nm

Nm: Not measured

143

Table B. 2 Effect of Different Alginate concentrations on Turbidity Removal for 160 mg/L of Calcium

CALCIUM WAS DOSED FIRST, THEN ALGINATE WAS ADDED

INITIAL TURBIDITY

(NTU)

INITIAL CALCIUM CONCENTRATION

(mg/L)

INITIAL ALGINATE CONCENTRATION (mg/L)

FINAL TURBIDITY (NTU)

FINAL CALCIUM CONCENTRATION

(mg/L)

TURBIDITY REMOVAL

(%)

CALCIUM REMOVAL (%)

150 160 40 1.5 16.47 99.0 89.7

150 160 20 0.7 16.52 99.5 89.7

150 160 10 0.5 20.38 99.7 87.3

150 160 8 0.4 15.22 99.7 90.5

150 160 6 0.6 13.16 99.6 91.8

150 160 4 0.8 16.67 99.5 89.6

150 160 2 0.9 12.76 99.4 92.0

150 160 1.60 1 13.01 99.3 91.9

150 160 0.80 1 15.22 99.3 90.5

150 160 0.40 1.1 13.06 99.3 91.8

150 160 0.32 2.8 14.57 98.1 90.9

150 160 0 5,1 nm 96.6 nm

Ca

CO

NC

EN

TR

AT

ION

160

mg

/L

Nm: Not measured

144

Table B. 3 Effect Of Different Alginate Concentrations On Turbidity Removal for 120 mg/L of Calcium

CALCIUM WAS DOSED FIRST, THEN ALGINATE WAS ADDED

INITIAL TURBIDITY

(NTU)

INITIAL CALCIUM CONCENTRATION

(mg/L)

INITIAL ALGINATE CONCENTRATION

(mg/L)

FINAL TURBIDITY

(NTU)

FINAL CALCIUM CONCENTRATION

(mg/L)

TURBIDITY REMOVAL (%)

CALCIUM REMOVAL

(%)

150 120 40 2.5 17.28 98.3 85.6

150 120 20 1.6 16.43 98.9 86.3

150 120 10 1.1 43.73 99.3 63.6

150 120 8 1.1 72.88 99.3 39.3

150 120 6 1 16.83 99.3 86.0

150 120 4 1.3 17.78 99.1 85.2

150 120 2 1 16.43 99.3 86.3

150 120 1.60 1.5 20.88 99.0 82.6

150 120 0.80 2.8 130.68 98.1

150 120 0.40 3.5 19.88 97.7 83.4

150 120 0.32 3.8 18.28 97.5 84.8

150 120 0.20 4.6 20.98 96.9 82.5

150 120 0 4.9 nm 96,7 nm

Ca

CO

NC

EN

TR

AT

ION

120

mg

/L

Nm: Not measured

145

Table B. 4 Effect of Different Alginate Concentrations on Turbidity Removal for 80 mg/L of Calcium

CALCIUM WAS DOSED FIRST, THEN ALGINATE WAS ADDED

INITIAL TURBIDITY

(NTU)

INITIAL CALCIUM CONCENTRATION

(mg/L)

INITIAL ALGINATE CONCENTRATION

(mg/L)

FINAL TURBIDITY

(NTU)

FINAL CALCIUM CONCENTRATION

(mg/L)

TURBIDITY REMOVAL (%)

CALCIUM REMOVAL

(%)

150 80 40 2.3 53.08 98.5 33.7

150 80 20 1.6 52.13 98.9 34.8

150 80 10 0.8 55.23 99.5 31.0

150 80 8 0.8 55.18 99.5 31.0

150 80 6 0.8 92.18 99.5 <1

150 80 4 1 50.03 99.3 37.5

150 80 2 1.5 58.48 99.0 26.9

150 80 1.60 1 63.68 99.3 20.4

150 80 0.80 1.6 64.73 98.9 19.1

150 80 0.40 2 58.08 98.7 27.4

150 80 0.32 2.6 39.03 98.3 51.2

150 80 0.20 3.1 32.43 97.9 59.5

150 80 0 5.6 nm 96.3 nm

Ca

CO

NC

EN

TR

AT

ION

80

mg

/L

Nm: Not measured

146

Table B. 5 Effect of Different Alginate Concentrations on Turbidity Removal for 60 mg/L of Calcium

CALCIUM WAS DOSED FIRST, THEN ALGINATE WAS ADDED

INITIAL TURBIDITY

(NTU)

INITIAL CALCIUM CONCENTRATION

(mg/L)

INITIAL ALGINATE CONCENTRATION

(mg/L)

FINAL TURBIDITY

(NTU)

FINAL CALCIUM CONCENTRATION

(mg/L)

TURBIDITY REMOVAL

(%)

CALCIUM REMOVAL

(%)

150 60 40 37 48.05 75.3 14.9

150 60 20 19.5 49.09 87.0 13.6

150 60 10 18 49.91 88.0 12.6

150 60 8 12 49.45 92.0 13.2

150 60 6 7.8 54.03 94.8 7.5

150 60 4 17 49.43 88.7 13.2

150 60 2 15 50.55 90.0 11.8

150 60 1.60 15 48.95 90.0 13.8

150 60 0.80 10 51.05 93.3 11.2

150 60 0.40 5.7 52.41 96.2 9.5

150 60 0.32 5.1 51.81 96.6 10.2

150 60 0.20 5.4 50.99 96.4 11.3

150 60 0.12 26.5 50.93 82.3 11.3

150 60 0.04 39.5 53.09 73.7 8.6

150 60 0.032 31.5 50.63 79.0 11.7

150 60 0.020 33 53.67 78.0 7.9

150 60 0.012 49 51.15 67.3 11.1

150 60 0.004 48 57.13 68.0 3.6

150 60 0 5.4 nm 96,4 nm

Ca

CO

NC

EN

TR

AT

ION

60

mg

/L

Nm: not measured

147

Table B. 6 Effect of Different Alginate Concentrations on Turbidity Removal for 30 mg/L of Calcium

CALCIUM WAS DOSED FIRST, THEN ALGINATE WAS ADDED

INITIAL TURBIDITY

(NTU)

INITIAL CALCIUM CONCENTRATION

(mg/L)

INITIAL ALGINATE CONCENTRATION

(mg/L)

FINAL TURBIDITY

(NTU)

FINAL CALCIUM CONCENTRATION

(mg/L)

TURBIDITY REMOVAL

(%)

CALCIUM REMOVAL (%)

150 30 40 135 22.24 10.0 25.9

150 30 20 115 22.49 23.3 25.0

150 30 10 94.5 24.33 37.0 18.9

150 30 8 89.5 22.43 40.3 25.2

150 30 6 87 23.99 42.0 20.0

150 30 4 90 24.30 40.0 19.0

150 30 2 77 26.95 48.7 10.2

150 30 1.60 75.5 23.79 49.7 20.7

150 30 0.80 44 29.18 70.7 2.7

150 30 0.40 40 nm 73.3 nm

150 30 0.32 24 nm 84.0 nm

150 30 0.20 21 18.24 86.0 39.2

150 30 0.12 17 27.46 88.7 8.5

150 30 0.04 21 27.10 86.0 9.7

150 30 0.032 22 30.11 85.3 <1

150 30 0.020 24 29.38 84.0 2.1

150 30 0.012 22 30.47 85.3 <1

150 30 0.004 23 30.61 84.7 <1

Ca

CO

NC

EN

TR

AT

ION

30

mg

/L

nm: Not Measured

148

Table B. 7 Effect of Different Alginate Concentrations on Turbidity Removal for 80 mg/L of Calcium when Alginate was dosed first

ALGINATE WAS DOSED FIRST, THEN CALCIUM WAS ADDED

INITIAL TURBIDITY

(NTU)

INITIAL CALCIUM CONCENTRATION

(mg/L)

INITIAL ALGINATE CONCENTRATION

(mg/L)

FINAL TURBIDITY

(NTU)

FINAL CALCIUM CONCENTRATION

(mg/L)

TURBIDITY REMOVAL

(%)

CALCIUM REMOVAL (%)

150 200 40 1 162.00 99.3 19.0

150 200 20 0.7 118.95 99.5 40.5

150 200 10 0.7 193.10 99.5 3.5

150 200 8 0.8 101.25 99.5 49.4

150 200 6 0.8 108.30 99.5 45.9

150 200 4 0.9 126.40 99.4 36.8

150 200 2 1.1 83.25 99.3 58.4

150 200 1.60 1.9 123.95 98.7 38.0

150 200 0.80 2.1 81.15 98.6 59.4

150 200 0.40 3 110.25 98.0 44.9

150 200 0.32 3.2 130.55 97.9 34.7

150 200 0.20 12 nm 92.0 nm

Ca

CO

NC

EN

TR

AT

ION

200

mg

/L

nm: Not Measured

149

Table B. 8 Effect of Different Alginate Concentrations on Turbidity Removal for 160 mg/L of Calcium when Alginate was dosed first

ALGINATE WAS DOSED FIRST, THEN CALCIUM WAS ADDED

INITIAL TURBIDITY

(NTU)

INITIAL CALCIUM CONCENTRATION

(mg/L)

INITIAL ALGINATE CONCENTRATION

(mg/L)

FINAL TURBIDITY

(NTU)

FINAL CALCIUM CONCENTRATION

(mg/L)

TURBIDITY REMOVAL (%)

CALCIUM REMOVAL (%)

150 160 40 7.8 11.40 94.8 92.9

150 160 20 4.1 11.95 97.3 92.5

150 160 10 3 14.55 98.0 90.9

150 160 8 2.8 13.00 98.1 91.9

150 160 4 1.5 12.95 99.0 91.9

150 160 2 0.9 14.30 99.4 91.1

150 160 1.60 0.6 13.40 99.6 91.6

150 160 0.80 0.5 12.30 99.7 92.3

150 160 0.40 0.8 12.85 99.5 92.0

150 160 0.32 1.1 14.00 99.3 91.3

150 160 0.20 1.7 12.15 98.9 92.4

150 160 0.12 2.3 12.85 98.5 92.0

Ca

CO

NC

EN

TR

AT

ION

160

mg

/L

Nm: Not measured

150

Table B. 9 Effect of Different Alginate Concentrations on Turbidity Removal for 120 mg/L of Calcium when Alginate was dosed first

ALGINATE WAS DOSED FIRST, THEN CALCIUM WAS ADDED

INITIAL TURBIDITY

(NTU)

INITIAL CALCIUM CONCENTRATION

(mg/L)

INITIAL ALGINATE CONCENTRATION

(mg/L)

FINAL TURBIDITY

(NTU)

FINAL CALCIUM CONCENTRATION

(mg/L)

TURBIDITY REMOVAL (%)

CALCIUM REMOVAL

(%)

150 120 40 64 16.59 57.3 57.3

150 120 20 36 17.54 76.0 76.0

150 120 10 15 18.39 90.0 90.0

150 120 8 8.4 16.49 94.4 94.4

150 120 4 3.1 20.54 97.9 97.9

150 120 2 1.4 17.74 99.1 99.1

150 120 1.60 1.3 16.99 99.1 99.1

150 120 0.80 1.1 60.04 99.3 99.3

150 120 0.40 1.3 17.79 99.1 99.1

150 120 0.32 1.8 19.64 98.8 98.8

150 120 0.20 2.5 45.09 98.3 98.3

150 120 0.12 9.5 17.59 93.7 93.7

Ca

CO

NC

EN

TR

AT

ION

120

mg

/L

Nm: not measured

151

Table B. 10 Effect of Different Alginate Concentrations on Turbidity Removal for 80 mg/L of Calcium when Alginate was dosed first

ALGINATE WAS DOSED FIRST, THEN CALCIUM WAS ADDED

INITIAL TURBIDITY

(NTU)

INITIAL CALCIUM CONCENTRATION

(mg/L)

INITIAL ALGINATE CONCENTRATION

(mg/L)

FINAL TURBIDITY

(NTU)

FINAL CALCIUM CONCENTRATION

(mg/L)

TURBIDITY REMOVAL (%)

CALCIUM REMOVAL (%)

150 80 40 110 62.29 26.7 22.1

150 80 20 95 49.09 36.7 38.6

150 80 10 90 62.14 40.0 22.3

150 80 8 81 13.79 46.0 82.8

150 80 4 15 59.94 90.0 25.1

150 80 2 5.5 52.44 96.3 34.5

150 80 1.60 5 44.74 96.7 44.1

150 80 0.80 2 59.34 98.7 25.8

150 80 0.40 1.8 94.94 98.8 <1

150 80 0.32 2 63.74 98.7 20.3

150 80 0.20 2.5 64.29 98.3 19.6

150 80 0.12 3.2 53.74 97.9 32.8

Ca

CO

NC

EN

TR

AT

ION

80

mg

/L

Nm: not measured

152

Table B. 11 Effect of Different Alginate Concentrations on Turbidity Removal for 60 mg/L of Calcium when Alginate was dosed first

ALGINATE WAS DOSED FIRST, THEN CALCIUM WAS ADDED

INITIAL TURBIDITY

(NTU)

INITIAL CALCIUM CONCENTRATION

(mg/L)

INITIAL ALGINATE CONCENTRATION

(mg/L)

FINAL TURBIDITY

(NTU)

FINAL CALCIUM CONCENTRATION (mg/L)

TURBIDITY REMOVAL (%)

CALCIUM REMOVAL

(%)

150 60 40 135 47.64 10.0 20.6

150 60 20 130 43.96 13.3 26.7

150 60 10 125 48.66 16.7 18.9

150 60 8 126 46.32 16.0 22.8

150 60 6 115 nm 23.3 nm

150 60 4 115 45.30 23.3 9.2

150 60 2 110 49.34 26.7 6.7

150 60 1.60 89 48.98 40.7 6.9

150 60 0.80 59.5 48.60 60.3 7.1

150 60 0.40 30.5 51.72 79.7 5.2

150 60 0.32 32.5 46.58 78.3 8.4

150 60 0.20 19.5 50.52 87.0 5.9

150 60 0.12 27.5 50.62 81.7 5.9

150 60 0.04 29.5 48.56 80.3 7.2

150 60 0.032 24.5 51.74 83.7 5.2

150 60 0.020 30 52.36 80.0 4.8

150 60 0.012 21.5 51.70 85.7 5.2

150 60 0.004 21 52.28 86.0 4.8

C

a C

ON

CE

NT

RA

TIO

N 6

0 m

g/L

nm: Not Measured

153

Table B. 12 Effect Of Different Alginate Concentrations On Turbidity Removal for 30 mg/L of Calcium when Alginate was dosed first

ALGINATE WAS DOSED FIRST, THEN CALCIUM WAS ADDED

INITIAL TURBIDITY

(NTU)

INITIAL CALCIUM CONCENTRATION

(mg/L)

INITIAL ALGINATE CONCENTRATION

(mg/L)

FINAL TURBIDITY

(NTU)

FINAL CALCIUM CONCENTRATION

(mg/L)

TURBIDITY REMOVAL

(%)

CALCIUM REMOVAL (%)

150 30 40 135 20.49 10.0 31.7

150 30 20 140 21.12 6.7 29.6

150 30 10 140 23.07 6.7 23.1

150 30 8 140 22.38 6.7 25.4

150 30 6 140 22.60 6.7 24.7

150 30 4 135 23.60 10.0 21.3

150 30 2 130 23.78 13.3 20.7

150 30 1.60 125 26.56 16.7 11.5

150 30 0.80 110 26.59 26.7 11.4

150 30 0.40 66 nm 56.0 nm

150 30 0.32 51 26.46 66.0 11.8

150 30 0.20 30 27.32 80.0 8.9

Ca

CO

NC

EN

TR

AT

ION

60

mg

/L

nm: Not Measured

154

APPENDIX C (80 NTU)

Table C. 1 Results Of Set for Water Sample Having 80 NTU of

Initial Turbidity Treated With 200 mg/L of Calcium

CALCIUM WAS DOSED FIRST, THEN ALGINATE WAS ADDED

INITIAL TURBIDITY (NTU)

INITIAL CALCIUM

CONCENTRATION (mg/L)

INITIAL ALGINATE

CONCENTRATION (mg/L)

FINAL TURBIDITY (NTU)

FINAL CALCIUM CONCENTRATIO

N (mg/L)

TURBIDITY

REMOVAL (%)

CALCIUM REMOVAL

(%)

80 200 40 1.6 167.50 98.00 16.25

80 200 20 0.7 161.25 99.13 19.37

80 200 10 0.7 161.60 99.13 19.20

80 200 8 0.6 166.03 99.25 16.99

80 200 6 0.6 168.29 99.25 15.86

80 200 4 1.5 169.39 98.13 15.30

80 200 2 0.8 169.24 99.00 15.38

80 200 1.60 0.9 170.95 98.88 14.52

80 200 0.80 0.6 138.44 99.25 30.78

80 200 0.40 1 165.52 98.75 17.24

80 200 0.32 1.1 163.61 98.63 18.19

80 200 0.20 1.4 166.98 98.25 16.51

80 200 0.12 2.6 167.78 96.75 16.11

80 200 0.04 4.5 167.23 94.38 16.38

80 200 0.032 3.4 163.97 95.75 18.02

80 200 0.020 3.6 163.87 95.50 18.07

80 200 0.012 4.1 164.62 94.88 17.69

80 200 0.004 5.3 167.13 93.38 16.43

Ca

CO

NC

EN

TR

AT

ION

200

mg

/L

80 200 0 5.4 Nm 93.3 Nm

Nm: not measured

155

Table C. 2 Results of Different Alginate Concentrations Effects for 160 mg/L of Calcium (80 NTU Initial Turbidity)

CALCIUM WAS DOSED FIRST, THEN ALGINATE WAS ADDED

INITIAL TURBIDITY

(NTU)

INITIAL CALCIUM CONCENTRATION

(mg/L)

INITIAL ALGINATE

CONCENTRATION (mg/L)

FINAL TURBIDITY

(NTU)

FINAL CALCIUM CONCENTRATION

(mg/L)

TURBIDITY REMOVAL

(%)

CALCIUM REMOVAL

(%)

80 160 40 2 111.96 97.50 30.03

80 160 20 0.8 121.00 99.00 23.75

80 160 10 0.6 122.26 99.25 23.59

80 160 8 0.6 134.32 99.25 16.05

80 160 6 1.1 142.16 98.63 11.15

80 160 4 0.8 132.36 99.00 17.28

80 160 2 1 137.43 98.75 14.10

80 160 1.60 0.8 134.12 99.00 16.18

80 160 0.80 0.5 135.57 99.38 15.27

80 160 0.40 1 125.37 98.75 21.64

80 160 0.32 1.5 121.55 98.13 24.03

80 160 0.20 2 119.44 97.50 25.35

80 160 0.12 2.1 122.86 97.38 23.21

80 160 0.04 3 121.96 96.25 23.78

80 160 0.032 3.4 152.31 95.75 4.81

80 160 0.020 4 113.41 95.00 29.12

80 160 0.012 4.4 127.94 94.50 20.04

80 160 0 6.5 Nm 91.8 nm

Ca

CO

NC

EN

TR

AT

ION

160

mg

/L

Nm: not measured

156

Table C. 3 Results of Different Alginate Concentrations Effects for 120 mg/L of Calcium (80 NTU Initial Turbidity)

CALCIUM WAS DOSED FIRST, THEN ALGINATE WAS ADDED

INITIAL TURBIDITY

(NTU)

INITIAL CALCIUM CONCENTRATION

(mg/L)

INITIAL ALGINATE CONCENTRATION

(mg/L)

FINAL TURBIDITY

(NTU)

FINAL CALCIUM CONCENTRATION

(mg/L)

TURBIDITY REMOVAL

(%)

CALCIUM REMOVAL

(%)

80 120 6 0.6 97.08 99.25 19.10

80 120 4 0.6 93.47 99.25 22.11

80 120 2 1 88.59 98.75 26.17

80 120 1.60 0.7 88.39 99.13 26.34

80 120 0.80 0.6 40.93 99.25 65.89

80 120 0.40 0.7 40.70 99.13 66.08

80 120 0.32 1.1 88.59 98.63 26.17

80 120 0.20 1.4 94.52 98.25 21.23

80 120 0.12 1.9 90.55 97.63 24.54

80 120 0.04 3.5 84.17 95.63 29.86

80 120 0.032 4 91.46 95.00 23.79

80 120 0.020 5.3 82.76 93.38 31.03

80 120 0 7.6 nm 90.5 nm

Ca

CO

NC

EN

TR

AT

ION

120

mg

/L

Nm: not measured

157

Table C. 4 Results of Different Alginate Concentrations Effects for 80 mg/L of Calcium (80 NTU Initial Turbidity)

CALCIUM WAS DOSED FIRST, THEN ALGINATE WAS ADDED

INITIAL TURBIDITY

(NTU)

INITIAL CALCIUM CONCENTRATION

(mg/L)

INITIAL ALGINATE CONCENTRATION

(mg/L)

FINAL TURBIDITY

(NTU)

FINAL CALCIUM CONCENTRATION

(mg/L)

TURBIDITY REMOVAL (%)

CALCIUM REMOVAL

(%)

80 80 6 2 63.77 97.50 20.29

80 80 4 2.5 33.82 96.88 57.73

80 80 2 1.2 41.36 98.50 48.31

80 80 1.60 1.4 34.07 98.25 57.41

80 80 0.80 1.3 36.13 98.38 54.84

80 80 0.40 1.4 32.31 98.25 59.61

80 80 0.32 1.6 32.51 98.00 59.36

80 80 0.20 1.8 37.74 97.75 52.83

80 80 0.12 2.6 32.46 96.75 59.42

80 80 0.04 6 48.14 92.50 39.83

80 80 0.032 6.1 39.70 92.38 50.38

80 80 0.020 6.6 46.08 91.75 42.40

80 80 0 18 Nm 77.5 nm

Ca

CO

NC

EN

TR

AT

ION

80

mg/

L

Nm: Not measured

158

Table C. 5 Results of Different Alginate Concentrations Effects for 60 mg/L of Calcium (80 NTU Initial Turbidity)

CALCIUM WAS DOSED FIRST, THEN ALGINATE WAS ADDED

INITIAL TURBIDITY

(NTU)

INITIAL CALCIUM CONCENTRATION

(mg/L)

INITIAL ALGINATE CONCENTRATION

(mg/L)

FINAL TURBIDITY

(NTU)

FINAL CALCIUM CONCENTRATION

(mg/L)

TURBIDITY REMOVAL

(%)

CALCIUM REMOVAL

(%)

80 60 2 3.7 40.15 95.38 33.08

80 60 1.60 3 32.61 96.25 45.65

80 60 0.80 3.4 27.69 95.75 53.85

80 60 0.40 2.9 27.54 96.38 54.11

80 60 0.32 2.5 24.72 96.88 58.80

80 60 0.20 2.3 10.05 97.13 83.25

80 60 0.12 3.7 24.82 95.38 58.63

80 60 0.04 6.9 30.80 91.38 48.66

80 60 0.032 7.1 23.87 91.13 60.22

80 60 0.020 9.3 22.36 88.38 62.73

80 60 0 74 Nm 7.5 Nm

Ca

CO

NC

EN

TR

AT

ION

60

mg

/L

Nm: not measured

159

Table C. 6Results of Different Alginate Concentrations Effects for 200 mg/L of Calcium when Alginate was dosed first (80 NTU of Initial Turbidity)

ALGINATE WAS DOSED FIRST THEN CALCIUM WAS ADDED

INITIAL TURBIDITY

(NTU)

INITIAL CALCIUM CONCENTRATION

(mg/L)

INITIAL ALGINATE CONCENTRATION

(mg/L)

FINAL TURBIDITY

(NTU)

FINAL CALCIUM CONCENTRATION

(mg/L)

TURBIDITY REMOVAL

(%)

CALCIUM REMOVAL (%)

80 200 40 1.8 183.11 97.75 8.44

80 200 20 1 190.7 98.75 4.65

80 200 10 1.2 170.4 98.50 14.80

80 200 8 0.8 187.88 99.00 6.06

80 200 6 1 185.32 98.75 7.34

80 200 4 1.1 162.91 98.63 18.55

80 200 2 1.3 197.68 98.38 1.16

80 200 1.60 0.9 169.59 98.88 15.21

80 200 0.80 0.6 181.7 99.25 9.15

80 200 0.40 0.6 171.65 99.25 14.18

80 200 0.32 0.9 167.53 98.88 16.24

80 200 0.20 0.9 174.42 98.88 12.79

80 200 0.12 3 155.32 96.25 22.34

80 200 0.04 3.5 163.01 95.63 18.50

80 200 0.032 4.6 196.1 94.25 1.95

80 200 0.020 5 185.07 93.75 7.47

80 200 0.012 5.2 176.33 93.50 11.84

80 200 0.004 5 199.04 93.75 0.48

Ca

CO

NC

EN

TR

AT

ION

200

mg

/L

160

Table C. 7 Results Of Different Alginate Concentrations Effects For 160 mg/L of Calcium when Alginate was dosed initially (80 NTU of Initial Turbidity)

ALGINATE WAS DOSED FIRST THEN CALCIUM WAS ADDED

INITIAL TURBIDITY

(NTU)

INITIAL CALCIUM CONCENTRATION

(mg/L)

INITIAL ALGINATE CONCENTRATION

(mg/L)

FINAL TURBIDITY

(NTU)

FINAL CALCIUM CONCENTRATION

(mg/L)

TURBIDITY REMOVAL

(%)

CALCIUM REMOVAL (%)

80 160 6 6.2 134.32 92.25 16.05

80 160 4 2.8 134.32 96.50 16.05

80 160 2 3.2 142.16 96.00 11.15

80 160 1.60 2.2 132.36 97.25 17.28

80 160 0.80 1.4 137.43 98.25 14.10

80 160 0.40 0.9 134.12 98.88 16.18

80 160 0.32 1 135.57 98.75 15.27

80 160 0.20 1.2 125.37 98.50 21.64

80 160 0.12 4 143.11 95.00 10.56

80 160 0.04 6.6 119.44 91.75 25.35

80 160 0.032 6.5 122.86 91.88 23.21

80 160 0.020 6.4 121.96 92.00 23.78

Ca

CO

NC

EN

TR

AT

ION

160

mg

/L

161

Table C. 8 Results of Different Alginate Concentrations Effects for 120 mg/L of Calcium when Alginate was dosed initially (80 NTU of Initial Turbidity)

ALGINATE WAS DOSED FIRST THEN CALCIUM WAS ADDED

INITIAL TURBIDITY

(NTU)

INITIAL CALCIUM CONCENTRATION

(mg/L)

INITIAL ALGINATE CONCENTRATION

(mg/L)

FINAL TURBIDITY

(NTU)

FINAL CALCIUM CONCENTRATION

(mg/L)

TURBIDITY REMOVAL (%)

CALCIUM REMOVAL (%)

80 120 6 32 99.24 60.00 17.30

80 120 4 18 95.02 77.50 20.81

80 120 2 5 107.94 93.75 10.05

80 120 1.60 2.9 94.87 96.38 20.94

80 120 1.20 2.4 101.10 97.00 15.75

80 120 0.40 0.9 101.51 98.88 15.41

80 120 0.32 2 103.97 97.50 13.36

80 120 0.20 2.4 72.16 97.00 39.87

80 120 0.12 3.7 101.25 95.38 15.62

80 120 0.04 8.5 104.67 89.38 12.77

80 120 0.032 11 120.20 86.25 <1

80 120 0.020 14 102.71 82.50 14.41

Ca

CO

NC

EN

TR

AT

ION

120

mg

/L

162

Table C. 9 Results of Different Alginate Concentrations Effects for 60 mg/L of Calcium when Alginate was dosed initially (80 NTU of Initial Turbidity)

ALGINATE WAS DOSED FIRST THEN CALCIUM WAS ADDED

INITIAL TURBIDITY

(NTU)

INITIAL CALCIUM CONCENTRATION

(mg/L)

INITIAL ALGINATE CONCENTRATION

(mg/L)

FINAL TURBIDITY

(NTU)

FINAL CALCIUM CONCENTRATION

(mg/L)

TURBIDITY REMOVAL

(%)

CALCIUM REMOVAL (%)

80 80 6 57 60.90 28.75 23.87

80 80 4 55 46.88 31.25 41.40

80 80 2 55 47.03 31.25 41.21

80 80 1.60 40 58.84 50.00 26.45

80 80 0.80 3.7 50.85 95.38 36.43

80 80 0.40 2 43.87 97.50 45.16

80 80 0.32 2.1 38.79 97.38 51.51

80 80 0.20 1.8 31.31 97.75 60.87

80 80 0.12 2.5 44.87 96.88 43.91

80 80 0.04 4.5 52.01 94.38 34.99

80 80 0.032 5.4 45.33 93.25 43.34

80 80 0.020 7 44.87 91.25 43.91

Ca

CO

NC

EN

TR

AT

ION

80

mg

/L

163

Table C. 10 Results of Different Alginate Concentrations Effects for 60 mg/L of Calcium when Alginate was dosed initially (80 NTU of Initial Turbidity)

ALGINATE WAS DOSED FIRST THEN CALCIUM WAS ADDED

INITIAL TURBIDITY

(NTU)

INITIAL CALCIUM CONCENTRATION

(mg/L)

INITIAL ALGINATE CONCENTRATION

(mg/L)

FINAL TURBIDITY

(NTU)

FINAL CALCIUM CONCENTRATION

(mg/L)

TURBIDITY REMOVAL (%)

CALCIUM REMOVAL

(%)

80 60 2 54 22.31 32.50 62.82

80 60 1.60 50 20.70 37.50 65.50

80 60 0.80 41 47.89 48.75 20.19

80 60 0.40 26 20.95 67.50 65.08

80 60 0.32 20 23.92 75.00 60.14

80 60 0.20 8.5 28.14 89.38 53.10

80 60 0.12 3.5 25.48 95.63 57.54

80 60 0.04 7.7 32.16 90.38 46.40

80 60 0.032 11 36.63 86.25 38.95

80 60 0.020 13 38.69 83.75 35.51

Ca

CO

NC

EN

TR

AT

ION

60

mg

/L

164

Table C. 11 The Result of 1 meq/L of Magnesium Ion Used as Coagulant Aid to 80 mg/L for 80 NTU Sample Water

Table C. 12 The Result of 4 meq/L of Sodium Ion used as coagulant aid to 80 mg/L for 80 NTU Sample Water

Magnesium Conc.(mg/L)

1 meq/L Calcium Conc. (mg/L)

Alginate Conc. (mg/L)

Initial Turbidity

(NTU) Final

Turbidity (NTU)

Final Calcium Conc. (mg/L

Turbidity Removal efficiency

(%)

Ca Remaoval Efficiency

(%)

80 0.2 80 4.1 62.2 94.9 22.3

80 0.32 80 2.2 58.0 97.3 27.5

80 0.4 80 2.4 64.1 97.0 19.9

80 0.8 80 1.9 62.2 97.6 22.3

80 1.6 80 1.5 64.8 98.1 19.0

80 2 80 1.4 65.1 98.3 18.6

Magnesium Conc.(mg/L)

4 meq/L Calcium Conc. (mg/L)

Alginate Conc. (mg/L)

Initial Turbidity

(NTU) Final

Turbidity (NTU)

Final Calcium Conc. (mg/L

Turbidity Removal efficiency

(%)

Ca Remaoval Efficiency

(%)

80 0.2 80 4.4 65.2 94.5 18.5

80 0.32 80 2.2 63.4 97.3 20.7

80 0.4 80 1.6 63.8 98.0 20.3

80 0.8 80 1.5 66.1 98.1 17.3

80 1.6 80 1.4 67.5 98.3 15.6

80 2 80 1.2 62.7 98.5 21.7

165

APPENDIX D (10NTU)

Table D. 1 Evaluation of Alginate a1s a Potential Coagulant for Low Turbidity (10 NTU) Water Samples with 80 mg/L of Calcium

Table D. 2 Evaluation of Alginate As a Potential Coagulant for Low Turbidity (10 NTU) Water Water Samples with 80 mg/L of Calcium

(Cont’d)

Final Turbidity (NTU) Final Calcium Conc (mg/L)

Alginate Concentration

(mg/L)

Initial Calcium Concentration

(mg/L)

Initial Turbidity

(NTU)

at 3

0 m

in

at 6

0 m

in

at 9

0 m

in

at 1

20

min

at 3

0 m

in

at 6

0 m

in

at 9

0 m

in

at 1

20

min

0 80 10 5 2.8 1.2 1.1 n.m n.m n.m n.m

0.02 80 10 6.5 4.6 2.9 2.3 71.5 78.3 74.8 76.8

0.04 80 10 3.9 2.1 1.9 1.3 78.8 79.2 79.9 78.9

0.2 80 10 6 5 4.2 4.4 70.8 79 78.9 69.3

0.4 80 10 7.5 6.6 5.8 5.5 76.7 78.9 78.6 67.5

0.8 80 10 4.6 3.9 3.5 3.1 78.2 79 62.3 77.4

1.6 80 10 4.1 3.5 3.2 3 79.9 79.4 80 80

n.m. Not Measured.

Turbidity Removal Efficiency (%)

Calcium Removal Efficiency (%)

Alginate Concentration (mg/L)

Initial Calcium Concentration

(mg/L)

Initial Turbidity

(NTU)

at 3

0 m

in

at 6

0 m

in

at 9

0 m

in

at 1

20

min

at 3

0 m

in

at 6

0 m

in

at 9

0 m

in

at 1

20

min

0 80 10 50 72 88 89 n.m n.m n.m n.m

0.02 80 10 35 54 71 77 10.6 2.1 6.6 4.0

0.04 80 10 61 79 81 87 1.5 1.0 0.2 1.4

0.2 80 10 40 50 58 56 11.5 1.2 1.4 13.4

0.4 80 10 25 34 42 45 4.2 1.4 1.7 15.6

0.8 80 10 54 61 65 69 2.3 1.2 22.2 3.2

1.6 80 10 59 65 68 70 0.1 0.8 0.1 0.0

n.m. Not Measured.

166

Table D. 3 Evaluation of Alginate as a Potential Coagulant for Low Turbidity (10 NTU) Water Samples with 60 mg/L of Calcium

Table D. 4 Evaluation of Alginate As a Potential Coagulant for Low Turbidity (10 NTU) Water Water Samples with 60 mg/L of Calcium

(Cont’d)

Final Turbidity (NTU)

Final Calcium Conc (mg/L)

Alginate Concentration

(mg/L)

Initial Calcium Concentration

(mg/L)

Initial Turbidity

(NTU)

at 3

0 m

in

at 6

0 m

in

at 9

0 m

in

at 1

20 m

in

at 3

0 m

in

at 6

0 m

in

at 9

0 m

in

at 1

20 m

in

0 60 10 6 4.1 1.9 8.5 n.m n.m n.m n.m

0.02 60 10 6 4 2.7 2 57.0 56.7 56.8 57.0

0.04 60 10 4.1 2.6 2 1.5 51.3 51.3 52.0 52.2

0.2 60 10 5 4.5 4.1 3.6 54.0 53.8 54.5 54.8

0.4 60 10 6.5 6.2 5.7 5.1 53.7 54.0 54.6 54.9

0.8 60 10 6 5.4 5 4.6 56.0 55.6 56.1 56.7

1.6 60 10 6 5.2 5 4.5 55.6 56.1 56.2 56.9

n.m. Not Measured.

Turbidity Removal Efficiency (%)

Calcium Removal Efficiency (%)

Alginate Concentration

(mg/L)

Initial Calcium Concentration

(mg/L)

Initial Turbidity

(NTU)

at 3

0 m

in

at 6

0 m

in

at 9

0 m

in

at 1

20

min

at 3

0 m

in

at 6

0 m

in

at 9

0 m

in

at 1

20

min

0 60 10 40 59 81 15 n.m n.m n.m n.m

0.02 60 10 40 60 73 80 5.1 5.6 5.4 5.0

0.04 60 10 59 74 80 85 14.4 14.5 13.4 13.0

0.2 60 10 50 55 59 64 10.0 10.4 9.1 8.7

0.4 60 10 35 38 43 49 10.5 10.0 9.0 8.6

0.8 60 10 40 46 50 54 6.7 7.8 6.6 5.5

1.6 60 10 40 48 50 55 7.41 6.53 6.33 5.23

n.m. Not Measured.

167

Table D. 5 Evaluation of Alginate As a Potential Coagulant for Low Turbidity (10 NTU) Water Water Samples with 30 mg/L of Calcium

Table D. 6 Evaluation of Alginate as a Potential Coagulant for Low Turbidity (10 NTU) Water Water Samples with 30 mg/L of Calcium

(Cont’d)

Final Turbidity (NTU) Final Calcium Conc

(mg/L) Alginate

Concentration (mg/L)

Initial Calcium Concentration

(mg/L)

Initial Turbidity

(NTU)

at 3

0 m

in

at 6

0 m

in

at 9

0 m

in

at 1

20

min

at 3

0 m

in

at 6

0 m

in

at 9

0 m

in

at 1

20

min

0 30 10 9.1 9.7 6.2 6.1

0.02 30 10 8.8 5.6 5.5 5.4 29.1 29.5 29.6 29.4

0.04 30 10 8.8 5.5 5.1 5 29.5 29.4 29.6 29.7

0.2 30 10 9.5 6 6 5.9 29.2 29.4 29.1 29.6

0.4 30 10 9.7 6.1 6 6 30.0 29.9 29.7 30.0

0.8 30 10 9.6 6.1 6 6 29.8 29.4 29.0 29.5

1.6 30 10 9.7 6.4 6.1 6 29.2 28.9 29.6 29.7

n.m. Not Measured.

Turbidity Removal

Efficiency (%)

Calcium Removal

Efficiency (%) Alginate

Concentration

(mg/L)

Initial Calcium

Concentration

(mg/L)

Initial

Turbidity

(NTU)

at 3

0 m

in

at 6

0 m

in

at 9

0 m

in

at 1

20

min

at 3

0 m

in

at 6

0 m

in

at 9

0 m

in

at 1

20

min

0 30 10 9 3 38 39 n.m. n.m. n.m. n.m.

0.02 30 10 12 44 45 46 3.0 1.7 1.3 2.0

0.04 30 10 12 45 49 50 1.7 2.0 1.3 1.0

0.2 30 10 5 40 40 41 2.7 2.0 3.0 1.3

0.4 30 10 3 39 40 40 0.1 0.3 1.0 0.1

0.8 30 10 4 39 40 40 0.6 2.0 3.4 1.7

1.6 80 10 3 36 39 40 2.7 3.7 1.3 1.0

n.m. Not Measured.

168

APPENDIX E

Table E. 1 Evaluation of Magnesium As a Coagulant Aid for Low Turbidity (10 NTU) Water Samples with 30 mg/L of Calcium

Final Turbidity (NTU) Final Calcium Conc (mg/L)

Magnesium Concentration

(meq/L)

Alginate Concentration

(mg/L)

Initial Calcium Concentration

(mg/L)

Initial Turbidity

(NTU)

at 3

0 m

in

at 6

0 m

in

at 9

0 m

in

at 1

20

min

at 3

0 m

in

at 6

0 m

in

at 9

0 m

in

at 1

20

min

0 0 30 10 7.8 6.2 5.6 5 n.m. n.m. n.m. n.m.

1 0.02 30 10 6.5 4.6 2.9 2.3 71.5 78.3 74.8 76.8

1 0.04 30 10 3.9 2.1 1.9 1.3 78.8 79.2 79.9 78.9

1 0.2 30 10 6 5 4.2 4.4 70.8 79 78.9 69.3

1 0.4 30 10 7.5 6.6 5.8 5.5 76.7 78.9 78.6 67.5

1 0.8 30 10 4.6 3.9 3.5 3.1 78.2 79 62.3 77.4

1 1.6 30 10 4.1 3.5 3.2 3 79.9 79.4 80 80

n.m.: Not Measured

169

Table E. 2 Evaluation of Magnesium As a Coagulant Aid for Low Turbidity (10 NTU) Water Samples with 30 mg/L of Calcium

Turbidity Removal Efficiency (%) Calcium Removal Efficiency (%)

Magnesium Concentration

(meq/L)

Alginate Concentration

(mg/L)

Initial Calcium Concentration

(mg/L)

Initial Turbidity

(NTU)

at 3

0 m

in

at 6

0 m

in

at 9

0 m

in

at 1

20

min

at 3

0 m

in

at 6

0 m

in

at 9

0 m

in

at 1

20

min

0 0 30 10 22 38 44 50 n.m. n.m. n.m. n.m.

1 0.02 30 10 6 10 15 20 15.7 16 11.9 10.1

1 0.04 30 10 6 11 15 16 8.5 11.1 9.7 4

1 0.2 30 10 7 8 10 11 9.6 10 9.1 7.3

1 0.4 30 10 5 6 9 10 8.6 10.3 14.3 16.9

1 0.8 30 10 6 6 9 9 9.8 9.3 10.5 13.7

1 1.6 30 10 6 6 9 9 3.7 11.2 14.9 11.5

n.m.: Not Measured

170

Table E. 3 Evaluation of Magnesium As a Coagulant Aid for Low Turbidity (10 NTU) Water Samples with 30 mg/L of Calcium

Final Turbidity (NTU) Final Calcium Conc (mg/L) Magnesium

Concentration (meq/L)

Alginate Concentration

(mg/L)

Initial Calcium Concentration

(mg/L)

Initial Turbidity

(NTU)

at 3

0 m

in

at 6

0 m

in

at 9

0 m

in

at 1

20

min

at 3

0 m

in

at 6

0 m

in

at 9

0 m

in

at 1

20

min

0 0 30 10 7.8 6.2 5.6 5 n.m. n.m. n.m. n.m.

2 0.02 30 10 8.4 7.5 6.1 6 29.1 27.5 28.1 28.4

2 0.04 30 10 7.6 6.9 6 5.6 26.4 26.8 26.3 28.2

2 0.2 30 10 9.2 9.2 8.9 8.9 26.3 26.1 25.9 27.3

2 0.4 30 10 9.4 9.3 9 9 24.6 25.2 26.2 27.8

2 0.8 30 10 9.3 9.3 9.1 9 28.9 27.4 27 27.9

2 1.6 30 10 9.5 9.4 9.3 9.1 28.6 27.4 28.6 28.6

n.m.: Not Measured

171

Table E. 4 Evaluation of Magnesium As a Coagulant Aid for Low Turbidity (10 NTU) Water Samples with 30 mg/L of Calcium

Turbidity Removal Efficiency (%) Calcium Removal Efficiency (%)

Magnesium

Concentration (meq/L)

Alginate Concentration

(mg/L)

Initial Calcium Concentration

(mg/L)

Initial Turbidity

(NTU)

at 3

0 m

in

at 6

0 m

in

at 9

0 m

in

at 1

20

min

at 3

0 m

in

at 6

0 m

in

at 9

0 m

in

at 1

20

min

0 0 30 10 22 38 44 50 n.m. n.m. n.m. n.m.

2 0.02 30 10 16 25 39 40 2.9 8.5 6.2 5.2

2 0.04 30 10 24 31 40 44 12.1 10.5 12.2 5.9

2 0.2 30 10 8 8 11 11 12.4 13.1 13.6 9

2 0.4 30 10 6 7 10 10 18.1 15.9 12.8 7.5

2 0.8 30 10 7 7 9 10 3.7 8.8 9.9 7.1

2 1.6 30 10 5 6 7 9 4.8 8.6 4.8 4.7

n.m: Not Measured

172

Table E. 5 Evaluation of Magnesium As a Coagulant Aid for Low Turbidity (10 NTU) Water Samples with 30 mg/L of Calcium

Final Turbidity (NTU) Final Calcium Conc (mg/L)

Magnesium Concentration

(meq/L)

Alginate Concentration

(mg/L)

Initial Calcium Concentration

(mg/L)

Initial Turbidity

(NTU)

at 3

0 m

in

at 6

0 m

in

at 9

0 m

in

at 1

20

min

at 3

0 m

in

at 6

0 m

in

at 9

0 m

in

at 1

20

min

0 0 30 10 7.8 6.2 5.6 5 n.m. n.m. n.m. n.m.

4 0.02 30 10 7.3 5.9 5 4.5 25.3 25.2 26.4 27

4 0.04 30 10 7 6 5.1 5 27.5 26.7 27.1 28.8

4 0.2 30 10 6.9 6 7.8 8.5 27.1 27 27.3 27.8

4 0.4 30 10 6.9 8.9 8.6 8.5 27.4 26.9 25.7 24.9

4 0.8 30 10 9 9 8.9 8.5 27.1 27.2 26.9 25.9

4 1.6 30 10 nm nm nm nm 28.9 26.7 25.5 26.6

n.m: Not Measured

173

Table E. 6 Evaluation of Magnesium As a Coagulant Aid for Low Turbidity (10 NTU) Water Samples with 30 mg/L of Calcium

Turbidity Removal Efficiency (%)

Calcium Removal Efficiency (%)

Magnesium Concentration

(meq/L)

Alginate Concentration

(mg/L)

Initial Calcium Concentration

(mg/L)

Initial Turbidity

(NTU)

at 3

0 m

in

at 6

0 m

in

at 9

0 m

in

at 1

20

min

at 3

0 m

in

at 6

0 m

in

at 9

0 m

in

at 1

20

min

0 0 30 10 22 38 44 50 n.m. n.m. n.m. n.m.

4 0.02 30 10 27 41 50 55 15.7 16 11.9 10.1

4 0.04 30 10 30 40 49 50 8.5 11.1 9.7 4

4 0.2 30 10 31 40 22 15 9.6 9.9 9.1 7.3

4 0.4 30 10 31 11 14 15 8.6 10.3 14.3 16.9

4 0.8 30 10 10 10 11 15 9.8 9.3 10.5 13.7

4 1.6 30 10 nm nm nm nm 3.7 11.2 14.9 11.5

n.m: Not Measured

174

APPENDIX F

METALLIC AND OTHER PARAMETERS

PARAMETER (mg/l)

INFLUENT EFFLUENT PARAMETER

(mg/l) INFLUENT EFFLUENT

Iron 0.25 <0.05 Manganese <0.05 <0.05

Aluminum 0.11 <0.05 Copper <0.05 <0.05

Arsenic <0.01 <0.01 Lead <0.05 <0.05

Hg <0.01 <0.01 Cadmium <0.05 <0.05

Antimony <0.01 <0.01 Zinc 0.06 <0.05

Selenium <0.01 <0.01 Nickel <0.05 <0.05

Sn <0.01 <0.01 Cobalt <0.05 <0.05

Chromium <0.02 <0.02 Total Chromium <0.05 <0.05

CONTAMINATION PARAMETERS

PARAMETER (mg/l)

INFLUENT EFFLUENT PARAMETER (mg/l)

INFLUENT EFFLUENT

Amonnia Nitrogen 0.10 <0.05 Org. Content

(KmnO4) 3.8 2.2

Nitrite Nitrogen

0.004 <0.002 COD 6.2 <5

Nitrate Nitrogen <0.5 <0.5 BOD5 <5 <5

Org Nitrogen 7.54 5.77 TOC 8.94 2.42

Kjeldahl Nitrogen 7.64 5.77 TC 23.89 16.07

Total Phosphate 0.08 <0.02 TIC 14.95 13.65

Boron <0.05 <0.05 Detergent <0.1 <0.01

175

PYHSICAL/PHYSICOCHEMICAL PARAMETERS

PARAMETER INFLUENT EFFLUENT PARAMETER INFLUENT EFFLUENT

TURBIDITY (NTU) 5.0 0.3 COLOR (Pt-

Co) <5 <5

CONDUCTIVITY(µmhos/cm) 251 267 S.S.

(1050C.mg/l) 5.6 <5

pH 7.77 7.08

TOTAL SLUDGE

GENERATED (1800C,mg/l)

150 166

CHEMICAL PARAMETERS

PARAMETER Influent mg/l Effluent mg/l Influent meq/l

Effluent meq/l

Sodium 7.5 8.3 0.32 0.36

Potassium 3.1 3.3 0.079 0.08

Calsiyum 22.8 24.0 1.14 1.2

Magnesium 6.32 5.83 0.519 0.48

Li <0.1 <0.1

Barium <0.05 <0.05

Total Hardness(0FS) 8.3 8.4

Carbonate (CO3-2) <10 <10 -

Bicarbonate (HCO3-) 104 89 1.7 1.46

Chloride (Cl-) 6 8 0.16 0.22

Sulphate (SO4-2) 15 20 0.31 0.41

Nitrate 1.18 1.0 0.02 0.016

Floride <0.1 <0.1

SiO2 18.6 17.6

Total Alk. 85 73 1.7 1.46

176

APPENDIX G (RAW WATER)

Table G. 1 Assessment of water sample from IWTP by using 120 mg/L of Calcium

Final Turbidity (NTU) Turbidity Removal Efficiency (%) Alginate Conc

(mg/L)

Initial Cacium

Conc (mg/L)

Initial Turbidity

(NTU) at

30

min

at

60

m

in

at

90

min

at

12

0 m

in

at

30

min

at

60

m

in

at

90

min

at

12

0 m

in

0 120 6.4 5.4 4.8 4.9 5 15.6 25 23.4 21.9

0.02 120 6.4 5 4.4 4.3 4 21.9 31.3 32.8 37.5

0.04 120 6.4 4.6 4.4 4.3 4 28.1 31.3 32.8 37.5

0.2 120 6.4 4.4 4.1 3.8 3.7 31.3 35.9 40.6 42.2

0.4 120 6.4 4.6 4.1 4 3.8 28.1 35.9 37.5 40.6

0.8 120 6.4 5 4.3 4 3.7 21.9 32.8 37.5 42.2

1.6 120 6.4 4.3 4.1 3.7 3.7 32.8 35.9 42.2 42.2

2 120 6.4 3.1 3.1 3 2.9 51.6 51.6 53.1 54.7

4 120 6.4 3 3 3 3 53.1 53.1 53.1 53.1

6 120 6.4 3.1 3.1 3 3 51.6 51.6 53.1 53.1

177

Table G. 2 Assessment of water sample from IWTP by using 120 mg/L of Calcium (cont’d)

Final Calcium (mg/L) Calcium Removal Efficiency (%) Alginate

Conc (mg/L)

Initial Calcium

Conc (mg/L)

Initial Turbidity (NTU) at 30 min at 60 min at 90 min

at 120 min

at 30 min at 60 min at 90 min at 120 min

0 120 6.4 31.1 21.1 22.7 25.3 74.1 82.4 81.1 79.0

0.02 120 6.4 53.8 56.9 58.6 57.2 55.2 52.6 51.2 52.3

0.04 120 6.4 53.3 56.9 57.5 57.2 55.6 52.6 52.1 52.3

0.2 120 6.4 57.6 56.0 57.1 57.4 52.0 53.4 52.4 52.2

0.4 120 6.4 52.8 54.9 55.8 58.6 56.0 54.2 53.5 51.2

0.8 120 6.4 58.8 53.4 52.0 52.5 51.0 55.5 56.7 56.3

1.6 120 6.4 55.6 57.3 55.7 55.3 53.7 52.2 53.6 53.9

2 120 6.4 56.0 54.6 54.9 56.8 53.3 54.5 54.2 52.7

4 120 6.4 55.4 54.4 51.5 52.3 53.8 54.6 57.1 56.4

6 120 6.4 54.3 53.8 54.7 53.9 54.8 55.2 54.4 55.1

178

Table G. 3 Assessment of water sample from IWTP by using 80 mg/L of Calcium

Final Turbidity (NTU) Turbidity Removal Efficiency (%)

Alginate Conc (mg/L)

Initial Ca Conc (mg/L)

Initial Turbidity (NTU)

at 30 min at 60 min at 90 min at 120

min at 30 min at 60 min at 90 min

at 120 min

0 80 6.4 5.4 4.8 4.9 5 15.6 25.0 23.4 21.9

0.02 80 6.4 4 4 3.6 3.6 37.5 37.5 43.8 43.8

0.04 80 6.4 4.4 4.1 3.8 3.6 31.3 35.9 40.6 43.8

0.2 80 6.4 4.3 3.8 3.6 3.6 32.8 40.6 43.8 43.2

0.4 80 6.4 4.7 4 3.7 3.7 26.6 37.5 42.2 42.2

0.8 80 6.4 4.3 3.9 3.6 3.7 32.8 39.1 43.8 42.2

1.6 80 6.4 3.8 3.6 3.5 3.4 40.6 43.8 45.3 46.9

2 80 6.4 3 3 3 3 53.1 53.1 53.1 53.1

4 80 6.4 3.2 3.2 3.1 3.1 50.0 50.0 51.6 51.6

6 80 6.4 3.1 3.2 3.1 3.1 51.6 50.0 51.6 51.6

179

Table G. 4 Assessment of water sample from IWTP by using 80 mg/L of Calcium

Final Calcium Concentration (mg/L) Calcium Removal Efficiency (%) Alginate

Conc (mg/L)

Initial Ca Conc (mg/L)

Initial Turbidity (NTU)

at 30 min at 60 min at 90 min at 120

min at 30 min at 60 min at 90 min

at 120 min

0 80 6.4 12.4 12.4 11.0 11.0 84.5 84.5 86.3 86.3

0.02 80 6.4 28.9 29.7 29.8 33.4 63.9 62.9 62.8 58.3

0.04 80 6.4 26.9 26.0 28.3 30.2 66.4 67.5 64.6 62.2

0.2 80 6.4 26.3 27.5 31.6 28.6 67.2 65.7 60.5 64.2

0.4 80 6.4 28.1 28.1 27.7 25.5 64.8 64.9 65.4 68.1

0.8 80 6.4 38.5 28.4 30.2 25.9 51.9 64.6 62.2 67.7

1.6 80 6.4 32.4 29.9 30.2 31.0 59.5 62.6 62.2 61.3

2 80 6.4 24.0 27.3 23.7 24.6 70.0 65.9 70.4 69.3

4 80 6.4 25.8 26.9 23.5 23.4 67.7 66.4 70.6 70.8

6 80 6.4 32.1 29.0 31.4 29.4 59.8 63.7 60.7 63.3

180

Table G. 5 Assessment of water sample from IWTP by using 60 mg/L of Calcium

Final Turbidity (NTU) Turbidity Removal Efficiency (%)

Alginate Conc (mg/L)

Initial Ca Conc (mg/L)

Initial Turbidity

(NTU) at 30 min

at 60 min

at 90 min

at 120 min

at 30 min

at 60 min

at 90 min

at 120 min

0 60 6.5 5 4.8 5 4.9 23.1 26.2 23.1 24.6

0.02 60 6.5 5 4.5 4.1 4 23.1 30.8 36.9 38.5

0.04 60 6.5 5 4.5 4.1 4 23.1 30.8 36.9 38.5

0.2 60 6.5 4.9 4.4 4.1 4 24.6 32.3 36.9 38.5

0.4 60 6.5 4.9 4.4 4.1 4.5 24.6 32.3 36.9 30.8

0.8 60 6.5 5.2 4.4 4.4 4.4 20.0 32.3 32.3 32.3

1.6 60 6.5 5 4.4 4.4 4.3 23.1 32.3 32.3 33.9

181

Table G. 6 Assessment of water sample from IWTP by using 60 mg/L of Calcium (cont’d)

Final Calcium Concentration (mg/L) Calcium Removal Efficiency (%)

Alginate Conc (mg/L)

Initial Ca Conc (mg/L)

Initial Turbidity

(NTU)

at 30 min

at 60 min

at 90 min

at 120 min

at 30 min

at 60 min

at 90 min

at 120 min

0 60 6.5 12.6 8.4 9.8 11.7 79.0 86.0 83.7 80.5

0.02 60 6.5 24.9 25.3 27.9 25.9 58.5 57.9 53.5 56.9

0.04 60 6.5 27.7 26.5 23.1 26.1 53.8 55.8 61.4 56.5

0.2 60 6.5 25.8 26.5 25.4 23.1 57.1 55.8 57.8 61.5

0.4 60 6.5 20.8 20.4 19.8 20.9 65.4 66.0 67.0 65.2

0.8 60 6.5 23.3 26.0 23.2 24.9 61.2 56.7 61.4 58.6

1.6 60 6.5 23.3 20.9 20.7 17.1 61.2 65.2 65.5 71.5

182

Table G. 7 Assessment of water sample from IWTP by using 30 mg/L of Calcium

Final Turbidity (NTU) Turbidity Removal Efficiency (%)

Alginate Conc (mg/L)

Initial Ca Conc (mg/L)

Initial Turbidity (NTU)

at 30 min at 60 min at 90 min at 120 min at 30 min at 60 min at 90 min at 120

min

0 30 6.5 5.4 4.8 4.9 4.9 16.92 26.15 24.62 24.62

0.02 30 6.5 4.5 4.1 4 4 30.77 36.92 38.46 38.46

0.04 30 6.5 4.2 4.1 4 4 35.38 36.92 38.46 38.46

0.2 30 6.5 4.5 4.1 4 4 30.77 36.92 38.46 38.46

0.4 30 6.5 4.2 4.1 4 4 35.38 36.92 38.46 38.46

0.8 30 6.5 4.5 4.1 4 4 30.77 36.92 38.46 38.46

1.6 30 6.5 4.4 4.1 4 4 32.31 36.92 38.46 38.46

183

Table G. 8 Assessment of water sample from IWTP by using 30 mg/L of Calcium (cont’d)

Final Calcium Concentration (mg/L) Calcium Removal Efficiency (%)

Alginate Conc (mg/L)

Initial Ca Conc

(mg/L)

Initial Turbidity (NTU)

at 30 min at 60 min at 90 min at 120 min at 30 min at 60 min at 90 min at 120 min

0 30 6.5 12.2 13.8 11.4 11.7 59.5 54.1 62.2 61.0

0.02 30 6.5 20.6 21.6 19.3 20.3 31.3 28.1 35.7 32.3

0.04 30 6.5 21.3 21.1 23.8 23.9 29.0 29.8 20.7 20.3

0.2 30 6.5 20.8 17.1 18.3 20.2 30.8 42.9 39.1 32.6

0.4 30 6.5 18.87 18.6 18.3 18.8 37.1 37.9 39.1 37.4

0.8 30 6.5 24.0 17.8 21.3 22.7 20.1 40.7 28.0 24.5

1.6 30 6.5 18.6 17.4 17.1 19.9 38.1 42.1 43.1 33.6

184

Table G. 9 Assessment of water sample from IWTP by using 15 mg/L of Calcium

Final Turbidity (NTU) Turbidity Removal Efficiency (%)

Alginate Conc (mg/L)

Initial Calcium

Conc (mg/L)

Initial Turbidity

(NTU)

at 30 min at 60 min at 90 min at 120 min at 30 min at 60 min at 90 min at 120 min

0 15 6.5 5.6 4.9 5 5 13.9 24.6 23.1 23.1

0.02 15 6.5 4 3.9 3.7 3.5 38.5 40.0 43.1 46.2

0.04 15 6.5 3.7 3.6 3.5 3.4 43.1 44.6 46.2 47.7

0.2 15 6.5 3.8 3.7 3.6 3.4 41.5 43.1 44.6 47.7

0.4 15 6.5 3.9 3.8 3.6 3.5 38.5 46.2 46.2 47.7

0.8 15 6.5 4 3.5 3.5 3.4 40.0 44.6 46.2 49.2

1.6 15 6.5 3.9 3.6 3.5 3.3 40.0 44.6 46.2 49.2

185

Table G. 10 Assessment of water sample from IWTP by using 15 mg/L of Calcium (cont’d)

Final Calcium Concentration (mg/L) Calcium Removal Efficiency (%)

Alginate Conc (mg/L)

Initial Ca Conc (mg/L)

Initial Turbidity (NTU)

at 30 min at 60 min at 90 min at 120 min at 30 min at 60 min at 90 min at 120 min

0 15 6.5 9.8 11.8 10.7 11.7 34.5 21.3 28.9 21.9

0.02 15 6.5 14.5 12.9 14.1 14.7 3.3 14.2 5.9 1.8

0.04 15 6.5 13.2 10.7 9.4 9.4 12.2 28.4 37.2 37.4

0.2 15 6.5 7.2 5.9 6.3 5.7 52.0 60.9 58.2 62.1

0.4 15 6.5 5.5 8.6 7.0 6.6 63.3 42.9 53.1 56.2

0.8 15 6.5 5.9 5.4 3.0 2.8 61.0 64.4 80.3 81.2

1.6 15 6.5 3.6 2.5 3.2 4.4 76.2 83.12 79.0 70.4